Treatment-train strategy realizes broad-spectrum capture of hundreds of per- and polyfluoroalkyl substances from fluorochemical wastewater

Treatment-train strategy realizes broad-spectrum capture of hundreds of per- and polyfluoroalkyl substances from fluorochemical wastewater | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Treatment-train strategy realizes broad-spectrum capture of hundreds of per- and polyfluoroalkyl substances from fluorochemical wastewater Hui Lin, Yiyang Yang, Lihui Yang, Caiming Tang, Ying Yang, Shangtao Liang, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4382526/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Feb, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract Hundreds of per- and polyfluoroalkyl substances (PFAS) are found in fluorochemical production effluents, and existing adsorption devices are inadequate to address this PFAS challenge given their extreme structural diversity. Here, we achieve the efficient and broad-spectrum capture of 107 PFASs from fluorochemical effluents using a treatment-train strategy that combines Zn-based electrocoagulation (EC) with anion-exchange resin (AER) beds. The “zero-carbon” adsorbent, zinc hydroxide flocs, generated in-situ by Zn-based EC bulk removes PFAS with log K ow >4 through a semi-micellar adsorption mechanism similar to mineral flotation, resulting in the highest adsorption capacities among all reported adsorbents. Technical-economic analysis and life-cycle environmental impact showed that coupling Zn-based EC reduces the cost by an order-of-magnitude and the carbon-footprint by 70% compared to AER beds alone. It was also observed that iodinated PFAS, in which the fluorine atom is replaced by an iodine atom, had significantly improved adsorption selectivity, which may shed light on designing environmentally-friendly fluorochemicals. Earth and environmental sciences/Environmental sciences/Environmental chemistry/Environmental monitoring Physical sciences/Engineering/Civil engineering Per- and Polyfluoroalkyl Substances Zn-based Electrocoagulation Treatment-train Strategy Broad-spectrum Removal Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction A few days ago, the Biden-Harris Administration issued the legally binding U.S. National Drinking Water Standard for per- and polyfluoroalkyl substances (PFAS) to ensure that everyone has access to clean, safe drinking water, which will ultimately reduce PFAS exposure for more than 100 million Americans 1 . Numerous studies have demonstrated that these anthropogenic “forever chemicals” are widely distributed in the waters 2 , soils 3, 4 , atmosphere 5 , and living organisms in various venues 6, 7 , including mountains 8 and deep oceans 9 , and from the Antarctic 10 to the Arctic 11 . This has led to serious public concerns. A study shows that every newborn baby has PFAS in their blood 12 , as the documentary, The Devil We Know , puts it, “There was no clean blood”. Industrial wastewater, particularly from fluorochemical-related industries that extensively use PFASs as emulsifiers, is regarded as one primary source of PFAS entering the environment 13, 14 . For instance, Feng et al. 15 estimated that a mega fluorochemical industrial park (FIP) located in Shandong, China, had emitted a maximum of 9450 kg of perfluorooctanoic acid (PFOA) and 6066 kg of hexafluoropropylene oxides (HFPOs) into the air and water in 2021. These fluorochemical effluents, rich in PFAS, cause serious threats to contaminate water sources in China’s urban areas. A study covering an area of 400 million people suggests that fluorochemical production significantly contributes to excessive PFAS concentrations in China’s urban drinking water 16 . Given the large quantities of PFAS-rich industrial effluents being discharged continuously, finding a solution is urgent. Eliminating PFAS from waste streams remains a significant challenge despite intensive efforts, as traditional chemical and biological treatment processes are ineffective due to the strong carbon-fluorine bond and the special helical structure 17, 18 . Advanced redox technologies often suffer from very harsh conditions, high energy consumption and difficulty in fully mineralizing PFAS 19, 20, 21 . Currently, adsorption is the most practiced technology for the treatment of PFAS-containing waters 22 . It is also necessary to be used prior to or following a destructive technology to ensure effective PFAS treatment. Conventional activated carbon (AC) and anion-exchange resins (AER) remain the economically viable adsorbents for PFAS effluent treatment 22 , despite the screening of a large variety of adsorbent types and the development of many novel efficient adsorbents such as β -cyclodextrin polymer 23 , metal-organic frameworks 24 , and covalent-organic frameworks 25 . However, the effectiveness of AC and AER in treating PFAS in complex effluents is limited 26 . Competing constituents, such as dissolved organic matters (DOMs) and various anions, can significantly reduce their adsorption selectivity to PFAS 27 . As a result, adsorption studies and engineering treatments on PFAS are mainly limited to relatively clean water bodies with minimal background matrix, such as drinking water 28, 29 and groundwater 30, 31 . On the other hand, real-world industrial wastewater typically contains a multitude of PFAS. For instance, Tang et al. identified 175 formulae of PFASs with over 350 congeners in fluorochemical effluents 32 . Removing a wide range of PFAS with diverse structures is a challenging task that requires the synergy of multiple interactions. To our knowledge, no study has yet addressed the broad-spectrum adsorption removal of these compounds from complex real wastewater, and most previous reports have focused on removing a few regulated and well-known PFAS, such as PFOA and perfluorooctane sulfonate (PFOS) 33 . Here, we report the extensive capture of 107 PFASs (Fig. 1 , ranging from C2 to C16) from polymer fluoropolymer production effluents using a novel treatment-train strategy that combines Zn-based electrocoagulation process (Zn-based EC) with existing AC and/or AER devices. The effectiveness, cost, and environmental impacts of the treatment-train process were compared to those of a single adsorption process in a systematic evaluation. A mechanism similar to mineral flotation is proposed to explain the selective adsorption of hydrophobic PFAS by the Zn-based EC. Furthermore, the analysis examined the impact of structural features, such as the ratio of F/C and F/H, as well as the number of –O– and C–X (H, Cl, and I), on the adsorption selectivity of PFAS in the Zn-based EC process. It was observed, for the first time, that substituting iodine for fluorine significantly alters the properties of PFAS that favors their adsorptive removal. This study provides new leads towards addressing the challenge of severe PFAS pollution in fluorochemical production effluents: treatment trains for broad-spectrum, effective PFAS capture as well as treatment-facile fluorochemical design. Results and Discussion Capturing Hundreds of PFAS in Complex Fluorochemical Wastewaters with Zn-based EC and Conventional Adsorbents: Efficiency and Broad-Spectrum The study assessed a total of 107 PFASs (Supplementary Table 1), which were classified according to their structural properties into 5 categories (15 classes) (Fig. 1 a), including: 1) 9 perfluorocarboxylic acids (PFCAs, C2 ~ C10), 2) 32 hydrogenated polyfluoroalkyl acids (H-PFAAs, C2 ~ C16), 3) 52 poly- and perfluoropolyether acids (Ether-PFAAs, C3 ~ C16), 4) 9 chlorinated polyfluoroalkyl acids (Cl x -PFAAs, C2 ~ C9), and 5) 5 iodinated polyfluoroalkyl acids (I x -PFAAs, C2 ~ C8). Figure 1 b presented the concentrations of individual PFAS identified in the fluorochemical wastewater by targeted LC-Orbitrap-MS quantitative analysis with authentic standards. For PFASs without reference standards, semi-quantification was performed by comparing the MS signal intensities of their quasi-molecular ions with those of similar PFASs that were quantitatively analyzed, e.g., hydrogenated PFOA and PFOA. The profile of quantified PFAS was uniquely dominated by PFCA (63.9%). Significantly, PFOA displayed the highest concentration, reaching up to 58 µM (23.8 mg·L − 1 ), which accounted for 48.7% of the concentration of ∑PFASs assessed (117.8 µM or 36 mg·L − 1 ) and was considerably higher than any other reported samples by at least an order of magnitude. On the other hand, Ether-PFAAs and H-PFAAs had the highest prevalence with molar concentrations of 6% and 28% of all assessed PFASs, respectively. We also discovered several specific PFASs that underwent substitution by other halogen atoms, including Cl x -PFAAs and I x -PFAAs. The concentrations of these Cl x /I x -PFAAs were all less than 1 µM, and their total molar concentration only accounted for 2.2% of all assessed PFAS. The assessed 107 PFASs are mainly carboxylic acids (82 species), with fewer sulfonic acids (25 species) (Fig. 1 c). The carbon chain-length of the 107 PFASs assessed ranges from C2 to C16, encompassing 47 short-chain PFASs (C < 7) with 9 being ultra-short-chain PFASs (C < 4) and 60 long-chain PFASs (C ≥ 7). In addition, the combustion-ion chromatography (CIC) test showed a total organic fluorine (TOF) concentration of 49.05 ± 2.51 mg·L − 1 , surpassing the combined concentrations of total 107 PFASs examined (∑PFASs = 36 mg·L − 1 ). This implies the likelihood of other unobserved PFASs in the fluorochemical wastewater or underestimation of certain PFASs that lack authentic standards. The measured fluorochemical wastewater pH was neutral (pH = 7.3), and the presence of large amounts of background constituents included 35.86 ± 0.43 mg·L − 1 total organic carbon (TOC), 388.42 ± 2.34 mg·L − 1 chloride, 34.51 ± 0.92 mg·L − 1 nitrate, 181.07 ± 4.18 mg·L − 1 sulfate, 44.52 ± 1.22 mg·L − 1 fluoride (Supplementary Table 2). First, we examined the kinetics of PFOA removal from fluorochemical wastewater using coconut shell AC and PFA694E AER as adsorbents, as well as electrocoagulation (EC) system using zinc, iron, and/or aluminum electrodes. As shown in Fig. 2 a, the traditional Al-based and Fe-based EC systems were ineffective in removing PFOA from the fluorochemical wastewater with a removal rate of less than 20%; while sustained and rapid reduction of PFOA concentration was seen in the Zn-based EC system and achieved a 92 ± 1.5% removal after 30-minute treatment. Although AC and PFA694E used here had high theoretical adsorption capacities (by Langmuir model, Supplementary Fig. 2) of 0.77 and 1.87 mmol PFOA·g − 1 , respectively; only a small amount of PFOA was removed, namely 16.5 ± 5.9% for AC and 26.9 ± 1.5% for PFA694E, after 60 minutes of sorption treatment at a high adsorbent dosage of 330 mg·L − 1 . The quantity of PFOA adsorbed ( q t ) over time was calculated and depicted in Fig. 2 b. Zinc hydroxide flocs generated in-situ by Zn-based EC exhibited the highest sorption of PFOA with a magnitude of 76.1 ± 4.2 mg·g − 1 (zinc hydroxide flocs), approximately 14.1 and 5.8 times greater than that of AC (5.4 ± 0.4 mg·g − 1 ) and PFA694E (13.2 ± 0.1 mg·g − 1 ), respectively. To assess the efficacy of eliminating all PFASs from fluorochemical wastewater utilizing AC, PFA694E and Zn-based EC, changes in the concentrations of TOF (Fig. 2 c) and 107 PFASs (Fig. 2 d) were analyzed. Compared to AC (12.1 ± 4.9%) and PFA694E (19.5 ± 1.9%), the Zn-based EC system achieved a significantly higher TOF reduction (51.6 ± 7%). The bubble plots in Fig. 2 d and Supplementary Figs. 3,4,5,6 displayed the PFAS arranged by m/z ( X -axis) and carbon-chain length ( Y -axis), with bubble diameters being proportional to their concentrations. The Zn-based EC system was greatly effective at reducing long-chain PFAS, but less effective at removing short-chain PFAS. The PFA694E appeared to be able to remove all kinds of PFAS, but most PFAS had limited removal; AC was the least effective, failing to significantly remove any of the 107 PFASs. Further, we counted the removal rate of 51 PFASs with concentrations higher than 10 µg·L − 1 , as depicted in Fig. 2 e. Specifically, 43 PFASs were removed at less than 30% after AC adsorption treatment, and the other 8 PFASs ranged from 30 to 50%; PFA694E adsorption achieved removal of 2 long-chain PFASs above 70%, but the vast majority of PFASs were removed at less than 50%. Impressively, as many as 21 (or 15, or 10) PFASs, mainly the long-chain PFAS, were removed greater than 70% (or 80%, or 90%) by the Zn-based EC system. It is well known that the traditional Al/Fe-based (electro)coagulation process is frequently used as a pre-treatment process for adsorption processes because of its ability to efficiently remove dissolved organic matters (DOMs) and certain inorganic ions, as well as trapping colloidal particles from wastewater 34 , and thereby reducing the adverse effects of these competing constituents on subsequent adsorption processes 35, 36 . Our observations showed that the Zn-based EC process also significantly reduced TOC as well as F − , SO 4 2− and NO 3 − (almost complete removal) in fluorochemical wastewater (Supplementary Fig. 7). This is quite significant given that few technologies have been reported to be capable of adsorbing large quantities of PFAS as well as simultaneously removing competing constituents from complex waste streams, which would greatly benefit the subsequent tandem conventional adsorption processes. With this in mind, we conducted a proof-of-concept test of a treatment-train process that combines Zn-based EC with the existing AC/AER adsorption devices to achieve broad-spectrum removal of hundreds of PFASs with diverse structural properties at varying concentrations from the complex fluorochemical wastewater. It is encouraging that the treatment-train process of Zn-based EC-coupled PFA694E adsorption achieved remarkable removal of all 107 PFASs (Fig. 2 d). Out of the 51 PFASs of high concentrations, up to 35 PFASs were reduced in concentration by more than an order of magnitude (Fig. 2 e). The total molar (mass) removal of 107 PFASs was 79.4 ± 3.2% (89.4 ± 3.9%), significantly higher than that of sorely PFA694E adsorption, which had a value of 24.4 ± 3.0% (27.8 ± 1.3%) (Fig. 2 f). A similar synergistic effect, albeit slightly less effective, was also noted when coupling the Zn-based EC process with generic AC sorption. Zn-based EC for Selective Adsorption of Hydrophobic PFAS with Ultra-High Capacity: Mechanistic Insights and PFAS Structural Implications Mechanistic Insights . To examine the differences in PFAS adsorption between conventional adsorbents and Zn-based EC process, we introduced the selective adsorption coefficient ( K d ) as a measure of PFAS adsorbability. A K d value greater than 1 for PFAS indicates that it will be preferentially adsorbed. The coefficient is calculated using the following Eq. 1 : $${K}_{\text{d}}=\frac{{\omega }_{\text{a}}}{{\omega }_{\text{b}}}/\frac{(1-{\omega }_{\text{a}})}{(1-{\omega }_{\text{b}})}$$ 1 where \({\omega }_{\text{b}}\) and \({\omega }_{\text{a}}\) represent the molar concentration fraction of a specific PFAS to the total 107 PFASs in the fluorochemical wastewater before and after adsorption, respectively. Figure 3 a illustrates the K d values of PFA694E for all 107 PFASs measured in the fluorochemical wastewater, which are located around 1 despite their wide variation in chemical structure and concentration. This finding is consistent with previous studies suggesting AER can adsorb a variety of ionizable PFAS 37, 38 . However, the lack of strong specific affinity between AER and PFAS also makes it highly susceptible to interference from coexisting competing constituents, thereby reducing its effectiveness in removing PFAS in practical complex wastewater matrices. It is interesting to note that the Zn-based EC selectively adsorbs highly hydrophobic PFASs and ignores hydrophilic PFAS (Fig. 3 a). Quantitative structure-activity relationship (QSAR) model fitting revealed a robust correlation between K d values and log K ow values (> 4) of PFAS, with the equation K d = 9.5 × log K ow − 38.6 ( R 2 = 0.849). It should be highlighted that all short-chain I x -PFAAs (C2 ~ C6) were preferentially adsorbed with K d >3, suggesting that all of them should be highly hydrophobic. However, the log K ow values (blue circle) estimated by the EPI Suite software for all short-chain I x -PFAAs are less than 4. Due to the lack of training set, current software has poor accuracy in predicting the physicochemical properties of novel PFAS. Since the log K ow values (no real measurements available) of all PFASs are derived from the software predictions, inaccurately predicted values for some novel PFASs are the main reason for their larger deviations from the fitted curves in Fig. 3 a, e.g., ether-PFAAs. In other words, these results suggest that the introduction of other atoms or structures, such as iodine atoms or ether groups, significantly alters the physicochemical properties of parent PFAS. This will be discussed in more detail later. To elucidate the selective adsorption mechanism in the Zn-based EC process, we further investigated the adsorption kinetics of 6 PFASs with varying chain-lengths in simulated solution. Zinc hydroxide flocs presented extremely rapid adsorption of all 6 PFASs with equilibrium time ( t eq ) less than of 2 min (Supplementary Fig. 8a), whereas AC and AER widely used in current applications had t eq of tens of hours or more (Supplementary Table 3). The observed maximum adsorption amount ( q m , mmol PFAS·g − 1 zinc hydroxide flocs) was monotonically correlated with their hydrophobicity and chain-lengths (Fig. 3 b and Supplementary Fig. 8b), suggesting a pivotal role of hydrophobic interaction. The weakly hydrophobic PFBA (C4, log K ow = 2.14) had a q m < 0.1 mmol·g − 1 , the moderately hydrophobic PFH x A (C6, log K ow = 3.48) had an elevated q m of 1.3 ± 0.2 mmol·g − 1 , and the highly hydrophobic PFDA (C10, log K ow = 6.15) achieved an ultra-high q m of > 23 mmol·g − 1 (> 10 g·g − 1 ). For the most discussed PFOA (log K ow =4.81), its q m was estimated to be 6.4 ± 0.4 mmol·g − 1 (2.6 g·g − 1 ). To the best of our knowledge, these achieved q m are the highest of all values reported in the literature, which are over an order-of-magnitude higher than the theoretical maximum adsorption capacity derived from the adsorption model fitting that of the data for the benchmark AC and several times higher than that of the AER (Fig. 3 c and Supplementary Table 3). Furthermore, the dynamic adsorption capacity ( q dyn = q t / t ) was more than 1 ~ 4 orders of magnitude higher than literature-reported adsorbents (Fig. 3 c). The SEM characterizations in Fig. 3 d and Supplementary Fig. 9 showed that the presence of PFAS affects the structural morphology of zinc hydroxide flocs generated in-situ by Zn-based EC. The fresh zinc hydroxide flocs were dispersed nanoflakes, while the Zn hydroxide flocs with adsorbed PFOA became dense. PFOA seemed to act as a binder to tightly aggregate and completely cover the dispersed Zn hydroxide flocs, as evidenced by the EDX results (Fig. 3 d). The F/Zn atomic ratio of Zn hydroxide flocs with adsorbed PFOA was up to 7.5. In mineral flotation, the non-polar ends of long hydrocarbon chain traps adsorbed on the surface of mineral particle associate with each other to form semi-micelles, i.e., semi-micellar adsorption, by van der Waals forces 39 . Similar to the mineral particles, zinc hydroxide flocs generated in-situ by electrocoagulation exhibit natural hydrophobicity. Inspired by the mineral flotation process, we propose a mechanism, i.e., hydrophobic force-driven semi-micellar adsorption, to clarify how Zn-based EC selectively absorbs hydrophobic PFAS (Fig. 3 e). Initially, benefiting from the highly dispersed and high specific surface area of zinc hydroxide flocs (minerals), hydrophobic PFAS (trapping agent) can quickly move to their surface via hydrophobic force. Then, van der Waals forces induce high surface activity PFAS (e.g., long-chain PFAS) to create semi-micelles or micelles on their own, which leads to a significant improvement in their adsorption capabilities and ultimately results in ultra-high adsorption capacities. Results from physicochemical characterizations of the PFAS-adsorbed zinc hydroxide flocs and theoretical calculations provided evidence for the proposed mechanism. Hydrophobic PFAS molecules would be adsorbed flat on the surface of zinc hydroxide flocs to minimize water-fluorine interactions. Based on the molecular size of PFAS optimized by the Gaussian 09 (Supplementary Fig. 10), the spatial maximum number of PFOA (11.61 × 4.05 × 3.98 Å) and PFDA (13.72 × 4.05 × 3.96 Å) molecules per unit surface area for a monolayer of coverage was estimated to be less than 2.1 and 1.8 molecules per nm 2 , respectively, assuming that the long axis (C-C chain) of the molecule is parallel to the surface and no space exists between molecules. Conversion of the molar mass of PFAS adsorbed per unit surface area results in approximately 18 PFOA molecules and > 65 PFDA molecules per nm 2 of the zinc hydroxide flocs (BET = 213.1 ± 10.6 m 2 ·g − 1 , Supplementary Fig. 10) according to their q m values, which is over an order-of-magnitude higher than the maximum number of molecules for a monolayer of coverage. The XPS and SEM-EDX characterizations further confirmed that the surface of zinc hydroxide flocs was tightly covered by the adsorbed-PFAS, as demonstrated by the intense F-element signals and significantly reduced Zn-element signals in Supplementary Fig. 9. The measured F/Zn atomic ratios of the zinc hydroxide flocs with adsorbed PFOA (PFNA and PFDA) were 6.35 ~ 7.54 (7.35 ~ 7.9 and 8.85 ~ 9.96) (Supplementary Table 4), and it is clear that these highly hydrophobic PFASs were multilayered adsorbed. Weakly hydrophobic PFASs, usually the short-chain PFAS, have low surface activity and are unable to form semi-micelles or micelles on the surface of zinc hydroxide flocs. Furthermore, the electrostatic adsorption can also be neglected because of the zinc hydroxide flocs had a negative or weakly positive zeta potential (Supplementary Fig. 12). As a result, their adsorption capacity is significantly lower compared to hydrophobic PFAS. In principle, this unique mechanism would also enable the Zn-based EC to avoid adverse effects from other coexisting contaminants and DOMs in solution, as these competing constituents tend not to be highly hydrophobic. Therefore, the Zn-based EC could be an effective technique for treating highly complex waste streams such as aqueous fire forming foams (AFFFs) solution and still bottoms liquid waste containing high concentrations of PFAS from adsorbent regeneration. Effect of the Structure of PFASs on their Adsorbability. As the use of legacy perfluorinated C n F 2 n +1 –X (X = COO − or SO 3 − ) compounds has been restricted, many alternative PFASs have been created and extensively applied for fluorochemical production. The main substitution strategy involves inserting –H, –Cl, –OH or –O– into perfluorinated molecules, which reduces the “effective length” of fluorinated chain segments, to reduce their persistence. Here, we sought to explore the adsorbability of various PFASs in terms of their chemical structure, which may provide critical guidance for the design of alternative PFASs that are easier to eliminate. Figure 4 a illustrated the relationship between the K d value of PFASs and the ratio of F/C as well as F/H in their chemical structure. The preferentially adsorbed PFASs were mainly concentrated in the upper-right quadrant region with high F/C and F/H ratios. This suggests that for a PFAS to be preferentially adsorbed, it must satisfy two structural conditions: ( 1 ) a high degree of fluorination (e.g., F/C > 1.6), and ( 2 ) a large number of fluorine atoms (e.g., > 8). It is evident that the physical and chemical properties of PFASs, as well as their environmental behavior, are profoundly determined by the number and distribution of [CF n ] ( n = 1 ~ 3) and [CH n ] ( n = 1 ~ 3) in their chemical structure. Figure 4 b showed how the length of the [CF n ] chain and the number of hydrogen atoms attached to the carbon in the PFAS molecule affect its K d . Typically, PFAS with 6 or more [CF n ] units would be preferentially adsorbed. However, [CH n ] groups may significantly reduce their adsorbability. For instance, although some PFASs have 7 or 8 [CF n ] units in their chemical structure, but the existence of multiple [CH n ] groups (e.g., > 5) can offset the benefits of the [CF n ] units. Ether-PFAAs are the most abundant class of PFASs in the fluorochemical wastewater. Figure 4 c illustrates the impact of the number of carbon-ether bonds (C–O–C) on the K d value of Ether-PFAAs (with PFCA and iodinated PFPESA as controls). In general, the existence of C–O–C bonds is likely to result in lower adsorbability regardless of the structure of the Ether-PFAAs. For instance, the K d value of PFPECA (green circle) was consistently lower than that of the corresponding chain-length of perfluoroalkyl acid (blue circle), and a plurality of C–O–C bonds further reduced its K d value. These results clearly indicated that PFAS alternatives with –H and/or –O– introduced into the perfluorinated structure (C n F 2 n +1 –) tend to be less adsorbable. Notably, the behavior of the novel I x -PFAAs was markedly different. Their chemical structure contains 1 to 3 [CH n ] units and no more than 4 [CF n ] groups (Fig. 4 b), placing them in the lower-left quadrant region with low F/C and F/H ratios in Fig. 4 a. In principle, they should not be preferentially adsorbed. However, all measured I x -PFAAs had K d values much greater than 1. For example, 4:4 I-FTOA (CH 2 I[CF 2 ] 4 [CH 2 ] 2 COOH) has a composition of 3[CH 2 ] groups and only 4[CF 2 ] units, yet it had an extremely high K d value of 17.39. Similarly, 3:3 I-FTHxA (CF 2 I[CF 2 ] 2 [CH 2 ] 2 COOH) with even less [CF 2 ] also had a K d value of 3.75. Both of them had higher K d values than the corresponding chain-length perfluorocarboxylic acids, i.e., PFOA ( K d =10.9) and PFHxA ( K d =0.53), respectively. Furthermore, we observed that the short-chain and ultra-short-chain iodinated ether-FTSAs (I-FTPESAs) were also preferentially adsorbed (Fig. 4 d). For example, 1:1 I-FTOPrSA (CH 2 I-O-CF 2 SO 3 H) and 2:2 I-FTOPeSA (CF 2 ICH 2 -O-CH 2 CF 2 SO 3 H) achieved K d values of 5.28 and 3.68, respectively. It is widely recognized that chlorinated PFAS (Cl x -PFAS), as a class of alternative PFAS, have been developed and used extensively in commercial products and industrial materials for decades 40 . Ten Cl x -PFASs (Supplementary Table 1) including 8 Cl x -PFCAs (ranging from C2 to C9) and 2 chloroperfluoropolyether carboxylates (Cl x -PFPECAs) found in the fluorochemical wastewater. The study found that Cl x -PFAS and non-chlorinated PFAS have similar or slightly higher K d values, e.g., Cl-PFOA (CF 2 Cl[CF 2 ] 6 COOH, K d =11.65) vs . PFOA ( K d =10.9), but none of the short-chain Cl-PFCAs showed preferential adsorption (Fig. 4 a). These results suggested that the Cl substitution (Cl→F) has little effect on the adsorbability of PFAS, but substitution of even one fluorine atom in PFAS with an iodine atom (I→F) causes a dramatic shift in their chemical properties. This finding is significant because it suggests that the potential environmental impacts of I x -PFAAs may differ significantly from those of traditional non-iodinated PFAS. A schematic diagram (Fig. 4 e) was drawn to depict the potential effect of inserting –H, –Cl, –I or –O– into the structure of PFAS molecules on their adsorbability. The novel structural feature and important environmental relevance (e.g., several hundred µg·L − 1 in the fluorochemical wastewater) of iodinated PFAS require an adequate understanding of their environmental behavior and fate. Alternatively, a recent study by Jin et al. 41 showed that the substitution of F with Cl significantly improved the biodegradability and reduced the toxicity of PFAS. Replacing F with I could further enhance this effect due to the larger radius of the iodine atom. Therefore, it may be possible to design alternative iodinated PFAS that are readily degradable and less toxic. Full-Scale System Simulations of Zn-based EC-coupled PFA694E Adsorption Bed To confirm the efficacy of the treatment-train strategy of Zn-based EC-coupled existing full-scale conventional adsorption units, a rapid small-scale column test (RSSCT) breakthrough experiment with fluorochemical wastewater was conducted as a proof-of-concept experiment. The constant diffusion model was used to scale down the operating parameters of the full-scale PFA694E beds to the RSSCT (Method section and Supplementary Table 5). First, we examined the breakthrough curve of the PFA694E bed fed by a simulated solution containing 25 mg·L − 1 of PFOA, at a concentration consistent with fluorochemical wastewater. The results showed that the bed values (BV) of BV 80 were estimated to be 15×10 3 BVs (Fig. 5 a). Unexpectedly, the PFA694E bed fed with untreated fluorochemical wastewater was breached in a very short time, with the values of BV 10 , BV 50 and BV 80 being only 0.39×, 0.54× and 0.66×10 3 BVs, respectively (Fig. 5 a). The concentration of TOF and other 106 PFASs in the effluent of the PFA694E bed was also monitored. As shown in Fig. 5 b, the TOF profile of the PFA694E bed was also rapidly breached, suggesting that the quick breakthrough occurred for all PFASs. When fed only 1.03×10 3 BV of untreated fluorochemical wastewater, the PFA694E bed showed almost complete breakthrough of the monitored 107 PFASs (Fig. 5 c and Supplementary Fig. 13), and the effluent TOF removal was less than 10% (Fig. 5 b). In contrast, Zn-based EC-coupled PFA694E bed adsorption treatment-train strategy achieved at least 50% removal of TOF throughout the treatment. At the point of 1.03×10 3 BV, the treatment-train strategy was still able to remove most of the monitored 107 PFASs (Fig. 5 c and Supplementary Fig. 13) and achieved 70% removal of TOF (Fig. 5 b). For example, nearly 99% of PFOA was removed by the treatment-train strategy with an effluent concentration of only 0.3 mg·L − 1 , compared to 22.3 mg·L − 1 in the effluent from the PFA694E bed fed with untreated fluorochemical wastewater. As a result, the front-end Zn-based EC treatment resulted in a 12.3-fold increase in BV 80 for PFOA, with a value of 7.77×10 3 BVs (Fig. 5 a). In addition to PFOA, we also monitored the breakthrough curves of 22 other representative PFASs with carbon-chain lengths ranging from 4 to 9 in fluorochemical wastewater at relatively high concentrations. As expected, the front-end Zn-based EC treatment significantly delayed the full breakthrough of the PFA694E bed (Supplementary Fig. 14), resulting in a 2.5-fold (PFBA) to 13.6-fold (Cl-PFOA) increase in BV80 values (Supplementary Fig. 15). Overall, PFASs with high log K ow values are more likely to achieve higher enhancement folds. A comparison of PFAS mass loading on a molar concentration basis identified distinct adsorption behaviors on the PFAE694E bed when combined with the front-end Zn-based treatment. As shown in Fig. 5 d, the cumulative adsorption mass profiles of all PFASs flattened, indicating that the PFA694E bed had reached its maximum PFAS adsorption capacity during the RSSCT test. The PFA694E bed retained a final PFAS loading of 41.2 µmol·g − 1 adsorbent fed with untreated fluorochemical wastewater, consisting of 81.1% of PFOA (compared to 76.5% PFOA in feed, Fig. 5 e) and 18.9% of other 22 PFASs. Although the front-end Zn-based EC treatment resulted in a 76% reduction in the total concentration of the 23 PFASs in the fluorochemical wastewater, from 75 µM to 18 µM (Fig. 5 e), the final loading of the 23 PFASs on the PFA694E bed, was even higher than that of the feed of untreated fluorochemical wastewater, i.e., 42.1 vs . 41.2 µmol·g − 1 (Figs. 5 f, 5 g). More importantly, the total loading of the other 22 PFASs was dramatically increased by over 3 times to 22.9 µmol·g − 1 , accounting for 54.3% of the final loading of the PFA694E bed. Expanded enlarged petal plots in Figs. 5 f, 5 g showed significant increases in loadings for most of the 23 PFASs, except for several highly hydrophobic PFASs (such as PFOA, PFNA, 3:3 I-FTHxA and 4:4 I-FTOA) whose concentrations were dramatically or nearly completely removed by the front-end Zn-based EC treatment. These results highlighted that to maximize the usable adsorbent bed service-life and achieve broad-spectrum removal of dozens or hundreds of PFAS in real-world complex scenarios, a potential treatment configuration could use a combination of Zn-based EC treatment and adsorbent in series. Techno-Economic Analysis and Life-cycle Environmental Impact The application prospects of the proof-of-concept treatment-train strategy were also evaluated based on carbon-footprint and techno-economic analysis. In this study, the PFA694E bed was operated as a single-use adsorbent, and the spent PFA694E and zinc hydroxide flocs with adsorbed PFAS would be incinerated. As shown in Fig. 6 a and Supplementary Table 5, the operational cost of the Zn-based EC process was approximately $ 1.43 per m 3 treated under a treatment time of 20 min, consisting of $ 1.14 for zinc metal cost, $ 0.1 for the electricity, and $ 0.19 for the incineration of zinc hydroxide flocs (assuming 10% water content). Recycling the incineration byproduct, ZnO, as a resource can significantly reduce the cost of Zn-based EC treatment to $ 0.1. Assuming a base case scenario where adsorption bed change-out criteria are dictated by PFOA removal less than 90%, the predicted operating cost of the treatment-train strategy was $ 4.55 ( $ 3.22 when ZnO recycled) per m 3 treated. In the absence front-end Zn-based EC treatment, the estimated operating cost would greatly increase to $ 49.94 per m 3 treated for the PFA694E bed system, over an order-of-magnitude higher than those of the treatment-train strategy. A cradle-to-grave life-cycle assessment was employed to compute the carbon-footprint of both the Zn-based EC and the PFA694E adsorption bed systems. The PFA694E adsorption bed system had a carbon-footprint of 13.75 KgCO 2 per m 3 treated under the change-out criteria of > 90% of PFOA removal (Fig. 5 b and Supplementary Table 5). Setting the same change-out criteria, the carbon-footprint of the treatment-train strategy, i.e., 3.93 KgCO 2 per m 3 treated, was only 28.6% of that of the PFA694E adsorption bed alone. Unlike PFA694E, which is considered a “high-carbon” adsorbent due to the large amounts of CO 2 emitted during its incineration (1.77 ± 0.02 KgCO 2 per KgPFA694E), the inorganic zinc hydroxide flocs generated in-situ by Zn-based EC are essentially a “zero-carbon” adsorbent. Additionally, CIC and TOC/N analyzer tests showed that the PFA694E contains 0.6 ± 0.01 mmol S, 2.42 ± 0.1 mmol N, and 0.39 ± 0.01 mol Cl per gram, suggesting that incineration treatment of the spent PFA694E will produce significant amounts of other pollutants, such as SO 2 , ozone, smoke particles, carcinogenics, and NO x . Significantly, Zn-based EC has a much lower environmental impact compared to the reported adsorbents mainly carbon material-based adsorbents 42 . Critical Implications for PFAS Research The importance of addressing PFAS emissions from industrial production should be of great concern, as it is still the most important source of PFAS entering the environment in many countries and regions, such as China. However, the high concentration and diversity of PFAS in industrial wastewater, as well as the complex background matrix, pose significant challenges to existing adsorption technologies. This study is the critical initial step in developing a treatment-train strategy that couples a novel Zn-based EC process with existing adsorption devices (e.g., AER and AC) to achieve the efficient and broad-spectrum capture of hundreds of PFAS with diverse properties from a fluorochemical industrial park effluent. The zinc hydroxide flocs generated in-situ by Zn-based EC can selectively and rapidly ( t eq 4) via a semi-micellar adsorption mechanism similar to that of mineral flotation. This unique multilayered adsorption mechanism outweighs the conventional adsorbents that are based on their limited adsorption sites to remove PFAS, and results in Zn-based EC with the highest adsorption capacities (e.g., 6.4 mmol PFOA per gram of zinc hydroxide flocs) to hydrophobic PFASs among all adsorbents reported. Meanwhile, the Zn-based EC is also capable of substantially removing the coexisting competing constituents such as DOMs and NO 3 − to the conventional adsorbents. These features are quite important for the subsequent tandem adsorption processes, as they greatly extend their lifetime, enhance their adsorption selectivity and adsorption capacity for short-chain PFAS, and reduce operating costs. Furthermore, the zinc hydroxide flocs are essentially inorganic “zero-carbon” adsorbents that significantly reduce the environmental impact of the treatment-train strategy. The rose chart (Fig. 6 c) demonstrates that the treatment-train strategy is superior to the PFA694E adsorption on almost all perspectives (for details, see Supplementary Table 6), such as PFAS removal efficiency and broad-spectrum, as well as economics and environmental impact, and has less solid waste generation. Therefore, the treatment-train methodology could be a potential upgrade of existing adsorption devices. On the other hand, fluorochemical-related industries have been crucial to modern socio-economics. As the use of traditional PFASs is gradually restricted, more and more new alternatives are being developed and widely used. However, many of them have come under global scrutiny of new concerns, e.g., GenX, for exhibiting similar persistence and biotoxicity as traditional PFASs. For the future design of specialty PFAS products, we need to maximize their eliminability and reduce their biotoxicity and persistence while maintaining desirable properties. Our experimental results evidence the inclusion of –H and –O– into perfluorinated structure decreases the adsorbability compared to the parent PFAS. A recent study by Jin et al. 41 highlighted that replacing one or more F atoms with Cl atoms in PFAS structures, known as Cl x -PFAS, could be an effective strategy to improve their biological and chemical degradability without increasing toxicity. In this study, Cl x -PFAS does not show a significant improvement in adsorbability; rather, the substitution of even a single iodine atom impressively alters the nature of the parent PFAS, greatly enhancing its hydrophobicity and allowing iodinated PFAS (I x -PFAS) to be readily adsorbed. Additionally, we also observed the degradation of I x -PFAS under natural conditions (data not shown). These novel findings provide not only, for the first time, critical fundamental knowledge into the assessment of the environmental fate of iodinated PFAS, but can also help to design environmentally-friendly PFAS and achieve sustainable management of fluorochemicals. Methods Samples and Chemicals . Wastewater samples were taken from the reverse osmosis (RO) concentrate of mixed effluents from multiple production plants of a mega fluorochemical industrial park (FIP) in northern China, where various PFASs were extensively used during the production of polymer fluoropolymers, including polyperfluoroethylene propylene (FEP), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF). Ammonium acetate (NH 4 AC), sodium chloride (NaCl), and PFAS chemicals such as PFOA and PFOS used in the experiments were purchased from Sigma-Aldrich Chemical Co., Ltd. The mass-labeled perfluorinated compounds EISs solution (MPFAC-C-ES, 13 3 C-labeled PFASs) were purchased from Wellington Laboratories Inc. Details of these internal standards are provided in Supplementary Table 7. Methanol (MeOH) and acetonitrile (ACN) were chromatographic grade and purchased from Merck Corp. Granular activated carbon (GAC, 20 ~ 40 mesh) was purchased from Macklin Biochemical Co., Ltd; PFA694E anion exchange resin (AER) was obtained from Purolite® (Bala Cynwyd, PA, USA). Electrocoagulation , Batch Adsorption and RSSCT Experiments . The electrocoagulation (EC) reactor was composed of a cylindrical EC cell (8 cm diameter and 15 cm height) with a 500 mL volume, as shown in Supplementary Fig. 1a. A metal (Zn, Al or Fe) sheet of 100 cm 2 surface area was used as anode, while a 304 stainless steel rod of 0.3 cm diameter was used as the cathode, with a distance of 3 cm between the electrodes. In each run, 300 mL of wastewater or simulated solution was added, and powered by a DC power (DH1718G-4, Dahua, China) under a constant current mode. During the EC treatment, the solution pH value was not adjusted or controlled. Prior to use, AC (50 ~ 60 mesh) and PFA694E (50 ~ 60 mesh) were repeatedly washed with DI water, followed by drying at 150℃ for 4 h and stored in a dryer. Adsorption isotherm tests were conducted by AC and PFA694E with PFOA solution of a wide range from 10 to 400 mg·L − 1 (AC) or 100 to 600 mg·L − 1 (PFA694E) for 24 h. All isotherm data were fitted by the Langmuir and/or Freundlich model. The adsorption treatment of fluorochemical wastewater experiments was also conducted. All adsorption experiments were performed in the polypropylene centrifuge tubes (150 mL) at room temperature on a vortex plate at 500 rpm. The adsorbent dose was 330 mg·L − 1 . Rapid small-scale column test (RSSCT) experiments (Supplementary Fig. 1b) were designed based on the constant diffusivity mode. Columns were organic glass made (6.4 mm inner diameter and 50 mm height) with a maximum volume of 1.66 mL. The PFA694E was crushed and sieved to 0.282 ~ 0.25 mm, which allowed the column diameter/PFA694E particle diameter ratio to be > 8 ~ 10 to eliminate wall or channel effects. Filters (200-mesh) on both sides of the column are to distribute water flow and prevent the leading of the AER particles and during the column testing. The columns were operated in an up-flow configuration mode of a rate a mL·min − 1 using a peristaltic pump. The column was thoroughly cleaned using DI water for 24 h before the experiment. The specific design formula was expressed as Eq. 2 and parameters can be found in Supplementary Table 5: $$\frac{{\text{E}\text{B}\text{C}\text{T}}_{SC}}{{\text{E}\text{B}\text{C}\text{T}}_{LC}}={\left(\frac{{\text{d}}_{SC}}{{\text{d}}_{LC}}\right)}^{2}$$ 2 where EBCT refers to the empty bed contact time (min); SC and LC refer to the RSSCT column and full-scale adsorber, respectively; d represents the diameter of the adsorbent (mm). In all cases, triplicate experiments were conducted, and samples were collected and filtered by a 0.22 µm cellulose membrane (> 95% PFAS recovery). Additionally, solid phase loading (µmol PFAS per adsorbent) of PFAS was calculated as follows: $$\text{S}\text{o}\text{l}\text{i}\text{d} \text{p}\text{h}\text{a}\text{s}\text{e} \text{l}\text{o}\text{a}\text{d}\text{i}\text{n}\text{g}=\frac{\int \left({\text{C}}_{0}-{\text{C}}_{effluent}\right)\text{d}\text{V}}{\text{m}}$$ 3 where C 0 and C effluent refer to the PFAS concentrations in the influent and effluent, respectively; V is the wastewater treated; m is the mass of adsorbent. The dissolved zinc dosage (mg·L − 1 ) was calculated as a function of electrocoagulation time using the following equation: $$\text{Z}\text{i}\text{n}\text{c} \text{d}\text{o}\text{s}\text{a}\text{g}\text{e}=\frac{1000}{\text{V}}\times \frac{\text{I}\times { \text{t}}_{\text{E}\text{C} }}{n\text{F}}\times \text{M} \times {\eta }$$ 4 where I and t EC refer to the applied current and time during electrocoagulation, respectively; F is the Faraday’s constant; n is the number of electrons in Zn − 2 e → Zn 2+ ; M (65 g·mol − 1 ) refers to the relative molar mass of zinc; η refers the current efficiency of Zn − 2 e → Zn 2+ , which is determined to 0.91 in the fluorochemical wastewater used in this study. Flocs Characterization . The zinc hydroxide flocs were collected and freeze-dried. The Brunauer-Emmett-Teller (BET) surface areas of the dried flocs were measured using a Micromeritics ASAP 2460. Field-emission scanning electron microscopy (FESEM, ZEISS Sigma 300) coupled with energy dispersive X-ray spectroscopy (EDX) was used for the morphology and elemental analyses. X-ray photoelectron spectroscopy (XPS) spectra of the flocs were measured by an ESCALAB 250Xi XPS system with a monochromatic Al Kα source. The zeta potentials of zinc hydroxide flocs during EC were measured by a Malvern zeta potential analyzer (Zetasizer Nano ZS90). PFAS and Wastewater Analysis . Concentrations of 107 PFASs were analyzed using an LC-Q-Orbitrap-HRMS system comprised of a Dionex ultraperformance liquid chromatograph (UPLC) and a Q-Extractive Plus mass spectrometer equipped with a heated-electrospray ionization (HESI) source (Thermo-Fisher Scientific, USA). The UPLC separation was carried out by an Acquity UPLC® BEH C18 column (2.1 100 mm, 1.7, Waters) using a gradient composition of solvent A (ACN) and solvent B (2 mM NH 4 AC in DI water) at a flow rate of 0.25 mL·min − 1 . The gradient expressed as the concentration of solvent A was as follows: 0 − 0.2 min, hold at 20% A; 0.2 − 8 min, a liner increase from 20% A to 80% A; 8 − 10 min, a liner increase from 80% A to 95% A; 10 − 12 min, hold at 95% A; 12 − 12.1 min, a liner decrease from 95% A to 20% A; 12.1 − 15 min, and hold at 20% A. The sample volume injected was 5 µL. The HESI source was operated in negative ionization mode with the spray potential at 3.2 kV, the capillary temperature at 320°C, the aux gas heater temperature at 350°C, and the sheath and auxiliary gas flow rate of 45 arb and 10 arb, respectively. Each sample was spiked with EISs solution (5 µg·L − 1 of each 13 C-labeled PFAS, Supplementary Table 6) as the internal standard for analysis. Details concerning PFASs analysis and data processing can be found in our previous studies 32 . Concentrations of total organic fluorine (TOF) in wastewater, and sulfur and chlorine content in PFA694E were detected using a combustion-ion chromatography (CIC) equipped with an automatic quick furnace (AQF-2100H), a combustion monitor (CM-210), and an ion chromatography system (Dionex ICS-5000). The Dionex ICS-5000 was also employed to measure the cations in wastewater including SO 4 2− , Cl − , F − and NO 3 − . More information about the CIC and ion chromatography analysis can be found in our previous studies. Concentrations of total organic carbon (TOC) in wastewater, and carbon and nitrogen content in PFA694E were measured by a multi N/C UV TOC analyzer (Analytic Jena, Germany). Techno-Economic Analysis (TEA) and Life-cycle Environment Impact Assessment (LCEIA) . The electric energy ( E , kWh·m − 3 ) of the Zn-based EC was calculated by Eq. 5 : $$E=\frac{\text{U}\times \text{I}}{\text{V}}\times {\text{t}}_{\text{E}\text{C}}$$ 5 where U refers to average voltage during electrocoagulation. The operating costs include direct cost of electricity, adsorbents and spent adsorbents incineration treatment. For detailed calculations of operating costs for the Zn-based EC, PFA694E bed, and treatment-train process, see Supplementary Text 1. A cradle-to-grave life-cycle assessment was employed to compute the carbon-footprint of both the Zn-based EC and the PFA694E adsorption bed processes. In this study, we only consider the carbon footprints (Kg CO 2 eq.). For detailed calculations, see Supplementary Text 2. Declarations Acknowledgements This study was financially supported by the National Natural Science Foundation of China (No. No.51878170), and the Guangdong Basic and Applied Basic Research Foundation (No. 2023A1515140067). Author contributions Y.L. and L.Y. performed the experiments, analysed the data and drafted the manuscript. C.T. contributed to the instrumental analysis. Y.Y. and A.W. contributed to data interpretation. C.T., S.L., J.X. and Q.H. contributed to the revision of the manuscript. H.L. designed and supervised the research, provided resources, and revised the manuscript. All authors participated in the manuscript reviewing and editing. Competing interests The authors declare no competing interests. Additional information The authors declare no competing interests. Additional information Supporting Information. Supplementary material for this article is available at http://pending. Correspondence and requests for materials should be addressed to Hui Lin. References USEPA, Final PFAS National Primary Drinking Water Regulation. https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas (2024). He A , et al. 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Life cycle assessment and life cycle cost analysis of anion exchange and granular activated carbon systems for remediation of groundwater contaminated by per- and polyfluoroalkyl substances (PFASs). Water Research 243 , 120324 (2023). Supplementary Information The Supplementary Tables, Supplementary Figures, and Supplementary Texts are missing. Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Published Journal Publication published 25 Feb, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4382526","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":303537373,"identity":"d8788642-856e-4940-985e-3842a446cbc4","order_by":0,"name":"Hui 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1","display":"","copyAsset":false,"role":"figure","size":159266,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDistribution of 107 PFASs species in fluorochemical wastewater\u003c/strong\u003e: (\u003cstrong\u003ea\u003c/strong\u003e) classification, (\u003cstrong\u003eb\u003c/strong\u003e) concentrations, and (\u003cstrong\u003ec\u003c/strong\u003e) chain length distribution of 107 PFASs.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4382526/v1/f14ace19d33ab5b75904eb5d.png"},{"id":56792329,"identity":"51297626-9ff0-4b23-8ce1-ca1653da173b","added_by":"auto","created_at":"2024-05-20 13:59:22","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":258996,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePerformance of different systems for the removal of PFAS from fluorochemical wastewater\u003c/strong\u003e: changes in the concentration of PFOA (\u003cstrong\u003ea\u003c/strong\u003e), TOF (\u003cstrong\u003ec\u003c/strong\u003e) and 107 PFASs (\u003cstrong\u003ed\u003c/strong\u003e), and the adsorbed amount (\u003cem\u003eq\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e) of PFOA \u003cem\u003evs\u003c/em\u003e. time (\u003cstrong\u003eb\u003c/strong\u003e); (\u003cstrong\u003ee\u003c/strong\u003e) removal efficiencies to 51 PFASs (initial concentration \u0026gt;10 μg·L\u003csup\u003e-1\u003c/sup\u003e); and (\u003cstrong\u003ef\u003c/strong\u003e) the total concentration removal of 107 PFASs. The error bars in this figure represent the SD (n=3 independent experiments).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4382526/v1/c49f746a266fcce84b4e895d.png"},{"id":56792333,"identity":"c28d90c8-3194-444f-b46a-efcf408ab7e5","added_by":"auto","created_at":"2024-05-20 13:59:22","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":531467,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMechanistic insights into the selective adsorption of hydrophobic PFAS with ultra-high capacity by Zn-based EC.\u003c/strong\u003e (\u003cstrong\u003ea\u003c/strong\u003e) Relationship between log\u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e and \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e of 107 PFASs: PFA694E \u003cem\u003evs\u003c/em\u003e. Zn-based EC. (\u003cstrong\u003eb\u003c/strong\u003e) The adsorption amount (\u003cem\u003eq\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e, in simulated water) of 6 PFCAs (C4~C10) by Zn-based EC \u003cem\u003evs\u003c/em\u003e. their log\u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e values, and (\u003cstrong\u003ec\u003c/strong\u003e) comparison of the achieved \u003cem\u003eq\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e and \u003cem\u003eq\u003c/em\u003e\u003csub\u003edyn\u003c/sub\u003e values for PFOA by Zn-based EC with various adsorbents in reported literature (listed in Supplementary Table 3). (\u003cstrong\u003ed\u003c/strong\u003e) SEM-EDX characterizations of the zinc hydroxide flocs generated in-situ by Zn-based EC in simulated solution with or without PFOA. (\u003cstrong\u003ee\u003c/strong\u003e) Schematic diagram of the proposed mechanisms for PFAS adsorption by Zn-based EC. The error bars in Fig. 3b represent the SD (n=3 independent experiments).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4382526/v1/d66ecf71befcedf494e4d69a.png"},{"id":56792349,"identity":"47d49824-b050-4a48-90e4-991ac85affad","added_by":"auto","created_at":"2024-05-20 13:59:24","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":188013,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEffect of the chemical structure of PFASs on their adsorbability by Zn-based EC. \u003c/strong\u003e(\u003cstrong\u003ea\u003c/strong\u003e) F/C ratio, F/H ratio of 107 PFASs \u003cem\u003evs\u003c/em\u003e. their \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values, and (\u003cstrong\u003eb\u003c/strong\u003e) [CF\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] (\u003cem\u003en\u003c/em\u003e=1~3), [CH\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] (\u003cem\u003en\u003c/em\u003e=1~3) numbers of 107 PFASs \u003cem\u003evs\u003c/em\u003e. their \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values. (\u003cstrong\u003ec\u003c/strong\u003e) [CF\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] (\u003cem\u003en\u003c/em\u003e=1~3), [C–O–C] numbers of 52 Ether-PFAAs \u003cem\u003evs\u003c/em\u003e. their \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values, and (\u003cstrong\u003ed\u003c/strong\u003e) F/C ratio, F/O ratio of 52 Ether-PFAAs \u003cem\u003evs\u003c/em\u003e. their \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values. (\u003cstrong\u003ee\u003c/strong\u003e) Schematic diagram of the potential effect of inserting –H, –Cl, –I or –O– into the structure of PFAS molecules on their adsorbability by Zn-based EC.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4382526/v1/a78012fd0defae1a7ef68717.png"},{"id":56792327,"identity":"d4dfec6a-2725-4b37-a71f-9f4e684836a7","added_by":"auto","created_at":"2024-05-20 13:59:22","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":241143,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFull-scale system simulations of PFA694E adsorption bed and Zn-based EC-coupled PFA694E adsorption bed (treatment-train) for fluorochemical wastewater purification. \u0026nbsp;a, b \u003c/strong\u003eRSSCT breakthrough curves of PFOA (\u003cstrong\u003ea\u003c/strong\u003e) and TOF (\u003cstrong\u003eb\u003c/strong\u003e). \u003cstrong\u003ec\u003c/strong\u003e Concentrations of 107 PFASs in the influent at 1.03×10\u003csup\u003e3\u003c/sup\u003e BV for the PFA694E adsorption bed fed with untreated (\u003cstrong\u003ec-1\u003c/strong\u003e) or Zn-based EC treated (\u003cstrong\u003ec-2\u003c/strong\u003e) fluorochemical wastewater. \u003cstrong\u003ed\u003c/strong\u003e Molar adsorption density profiles of 23 representative PFASs on the PFA694E adsorption bed. \u003cstrong\u003ee\u003c/strong\u003e Total concentrations of 23 representative PFASs and their percentage contribution in fluorochemical wastewater: untreated (outer ring)\u003cem\u003e vs\u003c/em\u003e. Zn-based EC treated (inter ring). \u003cstrong\u003ef, g\u003c/strong\u003e Finite loading of 23 representative PFASs onto the PFA694E bed fed with untreated (\u003cstrong\u003ef\u003c/strong\u003e) or Zn-based EC treated (\u003cstrong\u003eg\u003c/strong\u003e) fluorochemical wastewater. The error bars in Fig. 5b represent the SD (n=3 independent experiments).\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4382526/v1/f528c917cbf9e7ded97d518f.png"},{"id":56792337,"identity":"e285f285-042f-46af-90c0-8542ecd1a8b0","added_by":"auto","created_at":"2024-05-20 13:59:22","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":178204,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCost, environmental impact and technical performance analysis. a, b \u003c/strong\u003eTechno-economic analysis (\u003cstrong\u003ea\u003c/strong\u003e) and life-cycle environmental impact analysis (\u003cstrong\u003eb\u003c/strong\u003e) for the treatment of fluorochemical wastewater by the PFA694E adsorption bed or treatment-train strategy (adsorption bed replacement criterion set at \u0026gt;90% PFOA removal). \u003cstrong\u003ec\u003c/strong\u003e Rose chart depicting a comprehensive comparison of the PFA694E adsorption bed and treatment-train strategy on six metrics on a scale of 1 to 5 (i.e., low to high), including automatic operability, PFAS removal efficiency and broad-spectrum, environmental friendliness (mainly based on carbon-footprint), solid waste generation, and economics.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4382526/v1/3adcd3f17679cdf9d465433a.png"},{"id":77204241,"identity":"1d341387-bb5c-41cb-8ccb-04d1354e0a0f","added_by":"auto","created_at":"2025-02-26 08:05:18","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2736828,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4382526/v1/78e3de12-4727-41a7-b2ce-9c8b433d3f89.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Treatment-train strategy realizes broad-spectrum capture of hundreds of per- and polyfluoroalkyl substances from fluorochemical wastewater","fulltext":[{"header":"Introduction","content":"\u003cp\u003eA few days ago, the Biden-Harris Administration issued the legally binding U.S. National Drinking Water Standard for per- and polyfluoroalkyl substances (PFAS) to ensure that everyone has access to clean, safe drinking water, which will ultimately reduce PFAS exposure for more than 100\u0026nbsp;million Americans\u003csup\u003e1\u003c/sup\u003e. Numerous studies have demonstrated that these anthropogenic \u0026ldquo;forever chemicals\u0026rdquo; are widely distributed in the waters\u003csup\u003e2\u003c/sup\u003e, soils\u003csup\u003e3, 4\u003c/sup\u003e, atmosphere\u003csup\u003e5\u003c/sup\u003e, and living organisms in various venues\u003csup\u003e6, 7\u003c/sup\u003e, including mountains\u003csup\u003e8\u003c/sup\u003e and deep oceans\u003csup\u003e9\u003c/sup\u003e, and from the Antarctic\u003csup\u003e10\u003c/sup\u003e to the Arctic\u003csup\u003e11\u003c/sup\u003e. This has led to serious public concerns. A study shows that every newborn baby has PFAS in their blood\u003csup\u003e12\u003c/sup\u003e, as the documentary, \u003cem\u003eThe Devil We Know\u003c/em\u003e, puts it, \u0026ldquo;There was no clean blood\u0026rdquo;. Industrial wastewater, particularly from fluorochemical-related industries that extensively use PFASs as emulsifiers, is regarded as one primary source of PFAS entering the environment\u003csup\u003e13, 14\u003c/sup\u003e. For instance, Feng et al.\u003csup\u003e15\u003c/sup\u003e estimated that a mega fluorochemical industrial park (FIP) located in Shandong, China, had emitted a maximum of 9450 kg of perfluorooctanoic acid (PFOA) and 6066 kg of hexafluoropropylene oxides (HFPOs) into the air and water in 2021. These fluorochemical effluents, rich in PFAS, cause serious threats to contaminate water sources in China\u0026rsquo;s urban areas. A study covering an area of 400\u0026nbsp;million people suggests that fluorochemical production significantly contributes to excessive PFAS concentrations in China\u0026rsquo;s urban drinking water\u003csup\u003e16\u003c/sup\u003e. Given the large quantities of PFAS-rich industrial effluents being discharged continuously, finding a solution is urgent.\u003c/p\u003e \u003cp\u003eEliminating PFAS from waste streams remains a significant challenge despite intensive efforts, as traditional chemical and biological treatment processes are ineffective due to the strong carbon-fluorine bond and the special helical structure\u003csup\u003e17, 18\u003c/sup\u003e. Advanced redox technologies often suffer from very harsh conditions, high energy consumption and difficulty in fully mineralizing PFAS\u003csup\u003e19, 20, 21\u003c/sup\u003e. Currently, adsorption is the most practiced technology for the treatment of PFAS-containing waters\u003csup\u003e22\u003c/sup\u003e. It is also necessary to be used prior to or following a destructive technology to ensure effective PFAS treatment. Conventional activated carbon (AC) and anion-exchange resins (AER) remain the economically viable adsorbents for PFAS effluent treatment\u003csup\u003e22\u003c/sup\u003e, despite the screening of a large variety of adsorbent types and the development of many novel efficient adsorbents such as \u003cem\u003eβ\u003c/em\u003e-cyclodextrin polymer\u003csup\u003e23\u003c/sup\u003e, metal-organic frameworks\u003csup\u003e24\u003c/sup\u003e, and covalent-organic frameworks\u003csup\u003e25\u003c/sup\u003e. However, the effectiveness of AC and AER in treating PFAS in complex effluents is limited\u003csup\u003e26\u003c/sup\u003e. Competing constituents, such as dissolved organic matters (DOMs) and various anions, can significantly reduce their adsorption selectivity to PFAS\u003csup\u003e27\u003c/sup\u003e. As a result, adsorption studies and engineering treatments on PFAS are mainly limited to relatively clean water bodies with minimal background matrix, such as drinking water\u003csup\u003e28, 29\u003c/sup\u003e and groundwater\u003csup\u003e30, 31\u003c/sup\u003e. On the other hand, real-world industrial wastewater typically contains a multitude of PFAS. For instance, Tang et al. identified 175 formulae of PFASs with over 350 congeners in fluorochemical effluents\u003csup\u003e32\u003c/sup\u003e. Removing a wide range of PFAS with diverse structures is a challenging task that requires the synergy of multiple interactions. To our knowledge, no study has yet addressed the broad-spectrum adsorption removal of these compounds from complex real wastewater, and most previous reports have focused on removing a few regulated and well-known PFAS, such as PFOA and perfluorooctane sulfonate (PFOS)\u003csup\u003e33\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eHere, we report the extensive capture of 107 PFASs (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, ranging from C2 to C16) from polymer fluoropolymer production effluents using a novel treatment-train strategy that combines Zn-based electrocoagulation process (Zn-based EC) with existing AC and/or AER devices. The effectiveness, cost, and environmental impacts of the treatment-train process were compared to those of a single adsorption process in a systematic evaluation. A mechanism similar to mineral flotation is proposed to explain the selective adsorption of hydrophobic PFAS by the Zn-based EC. Furthermore, the analysis examined the impact of structural features, such as the ratio of F/C and F/H, as well as the number of \u0026ndash;O\u0026ndash; and C\u0026ndash;X (H, Cl, and I), on the adsorption selectivity of PFAS in the Zn-based EC process. It was observed, for the first time, that substituting iodine for fluorine significantly alters the properties of PFAS that favors their adsorptive removal. This study provides new leads towards addressing the challenge of severe PFAS pollution in fluorochemical production effluents: treatment trains for broad-spectrum, effective PFAS capture as well as treatment-facile fluorochemical design.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003e \u003cb\u003eCapturing Hundreds of PFAS in Complex Fluorochemical Wastewaters with Zn-based EC and Conventional Adsorbents: Efficiency and Broad-Spectrum\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe study assessed a total of 107 PFASs (Supplementary Table\u0026nbsp;1), which were classified according to their structural properties into 5 categories (15 classes) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea), including: 1) 9 perfluorocarboxylic acids (PFCAs, C2\u0026thinsp;~\u0026thinsp;C10), 2) 32 hydrogenated polyfluoroalkyl acids (H-PFAAs, C2\u0026thinsp;~\u0026thinsp;C16), 3) 52 poly- and perfluoropolyether acids (Ether-PFAAs, C3\u0026thinsp;~\u0026thinsp;C16), 4) 9 chlorinated polyfluoroalkyl acids (Cl\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAAs, C2\u0026thinsp;~\u0026thinsp;C9), and 5) 5 iodinated polyfluoroalkyl acids (I\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAAs, C2\u0026thinsp;~\u0026thinsp;C8). Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb presented the concentrations of individual PFAS identified in the fluorochemical wastewater by targeted LC-Orbitrap-MS quantitative analysis with authentic standards. For PFASs without reference standards, semi-quantification was performed by comparing the MS signal intensities of their quasi-molecular ions with those of similar PFASs that were quantitatively analyzed, e.g., hydrogenated PFOA and PFOA. The profile of quantified PFAS was uniquely dominated by PFCA (63.9%). Significantly, PFOA displayed the highest concentration, reaching up to 58 \u0026micro;M (23.8 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), which accounted for 48.7% of the concentration of \u0026sum;PFASs assessed (117.8 \u0026micro;M or 36 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and was considerably higher than any other reported samples by at least an order of magnitude. On the other hand, Ether-PFAAs and H-PFAAs had the highest prevalence with molar concentrations of 6% and 28% of all assessed PFASs, respectively. We also discovered several specific PFASs that underwent substitution by other halogen atoms, including Cl\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAAs and I\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAAs. The concentrations of these Cl\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e/I\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAAs were all less than 1 \u0026micro;M, and their total molar concentration only accounted for 2.2% of all assessed PFAS. The assessed 107 PFASs are mainly carboxylic acids (82 species), with fewer sulfonic acids (25 species) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). The carbon chain-length of the 107 PFASs assessed ranges from C2 to C16, encompassing 47 short-chain PFASs (C\u0026thinsp;\u0026lt;\u0026thinsp;7) with 9 being ultra-short-chain PFASs (C\u0026thinsp;\u0026lt;\u0026thinsp;4) and 60 long-chain PFASs (C\u0026thinsp;\u0026ge;\u0026thinsp;7). In addition, the combustion-ion chromatography (CIC) test showed a total organic fluorine (TOF) concentration of 49.05\u0026thinsp;\u0026plusmn;\u0026thinsp;2.51 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, surpassing the combined concentrations of total 107 PFASs examined (\u0026sum;PFASs\u0026thinsp;=\u0026thinsp;36 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). This implies the likelihood of other unobserved PFASs in the fluorochemical wastewater or underestimation of certain PFASs that lack authentic standards. The measured fluorochemical wastewater pH was neutral (pH\u0026thinsp;=\u0026thinsp;7.3), and the presence of large amounts of background constituents included 35.86\u0026thinsp;\u0026plusmn;\u0026thinsp;0.43 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e total organic carbon (TOC), 388.42\u0026thinsp;\u0026plusmn;\u0026thinsp;2.34 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e chloride, 34.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.92 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e nitrate, 181.07\u0026thinsp;\u0026plusmn;\u0026thinsp;4.18 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e sulfate, 44.52\u0026thinsp;\u0026plusmn;\u0026thinsp;1.22 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e fluoride (Supplementary Table\u0026nbsp;2).\u003c/p\u003e \u003cp\u003eFirst, we examined the kinetics of PFOA removal from fluorochemical wastewater using coconut shell AC and PFA694E AER as adsorbents, as well as electrocoagulation (EC) system using zinc, iron, and/or aluminum electrodes. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea, the traditional Al-based and Fe-based EC systems were ineffective in removing PFOA from the fluorochemical wastewater with a removal rate of less than 20%; while sustained and rapid reduction of PFOA concentration was seen in the Zn-based EC system and achieved a 92\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5% removal after 30-minute treatment. Although AC and PFA694E used here had high theoretical adsorption capacities (by Langmuir model, Supplementary Fig.\u0026nbsp;2) of 0.77 and 1.87 mmol PFOA\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively; only a small amount of PFOA was removed, namely 16.5\u0026thinsp;\u0026plusmn;\u0026thinsp;5.9% for AC and 26.9\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5% for PFA694E, after 60 minutes of sorption treatment at a high adsorbent dosage of 330 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The quantity of PFOA adsorbed (\u003cem\u003eq\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e) over time was calculated and depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb. Zinc hydroxide flocs generated in-situ by Zn-based EC exhibited the highest sorption of PFOA with a magnitude of 76.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2 mg\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (zinc hydroxide flocs), approximately 14.1 and 5.8 times greater than that of AC (5.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4 mg\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and PFA694E (13.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 mg\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo assess the efficacy of eliminating all PFASs from fluorochemical wastewater utilizing AC, PFA694E and Zn-based EC, changes in the concentrations of TOF (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec) and 107 PFASs (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed) were analyzed. Compared to AC (12.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.9%) and PFA694E (19.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.9%), the Zn-based EC system achieved a significantly higher TOF reduction (51.6\u0026thinsp;\u0026plusmn;\u0026thinsp;7%). The bubble plots in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed and Supplementary Figs.\u0026nbsp;3,4,5,6 displayed the PFAS arranged by \u003cem\u003em/z\u003c/em\u003e (\u003cem\u003eX\u003c/em\u003e-axis) and carbon-chain length (\u003cem\u003eY\u003c/em\u003e-axis), with bubble diameters being proportional to their concentrations. The Zn-based EC system was greatly effective at reducing long-chain PFAS, but less effective at removing short-chain PFAS. The PFA694E appeared to be able to remove all kinds of PFAS, but most PFAS had limited removal; AC was the least effective, failing to significantly remove any of the 107 PFASs. Further, we counted the removal rate of 51 PFASs with concentrations higher than 10 \u0026micro;g\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee. Specifically, 43 PFASs were removed at less than 30% after AC adsorption treatment, and the other 8 PFASs ranged from 30 to 50%; PFA694E adsorption achieved removal of 2 long-chain PFASs above 70%, but the vast majority of PFASs were removed at less than 50%. Impressively, as many as 21 (or 15, or 10) PFASs, mainly the long-chain PFAS, were removed greater than 70% (or 80%, or 90%) by the Zn-based EC system.\u003c/p\u003e \u003cp\u003eIt is well known that the traditional Al/Fe-based (electro)coagulation process is frequently used as a pre-treatment process for adsorption processes because of its ability to efficiently remove dissolved organic matters (DOMs) and certain inorganic ions, as well as trapping colloidal particles from wastewater\u003csup\u003e34\u003c/sup\u003e, and thereby reducing the adverse effects of these competing constituents on subsequent adsorption processes\u003csup\u003e35, 36\u003c/sup\u003e. Our observations showed that the Zn-based EC process also significantly reduced TOC as well as F\u003csup\u003e\u0026minus;\u003c/sup\u003e, SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e and NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e (almost complete removal) in fluorochemical wastewater (Supplementary Fig.\u0026nbsp;7). This is quite significant given that few technologies have been reported to be capable of adsorbing large quantities of PFAS as well as simultaneously removing competing constituents from complex waste streams, which would greatly benefit the subsequent tandem conventional adsorption processes. With this in mind, we conducted a proof-of-concept test of a treatment-train process that combines Zn-based EC with the existing AC/AER adsorption devices to achieve broad-spectrum removal of hundreds of PFASs with diverse structural properties at varying concentrations from the complex fluorochemical wastewater. It is encouraging that the treatment-train process of Zn-based EC-coupled PFA694E adsorption achieved remarkable removal of all 107 PFASs (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). Out of the 51 PFASs of high concentrations, up to 35 PFASs were reduced in concentration by more than an order of magnitude (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee). The total molar (mass) removal of 107 PFASs was 79.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2% (89.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.9%), significantly higher than that of sorely PFA694E adsorption, which had a value of 24.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0% (27.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3%) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef). A similar synergistic effect, albeit slightly less effective, was also noted when coupling the Zn-based EC process with generic AC sorption.\u003c/p\u003e \u003cp\u003e \u003cb\u003eZn-based EC for Selective Adsorption of Hydrophobic PFAS with Ultra-High Capacity: Mechanistic Insights and PFAS Structural Implications\u003c/b\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eMechanistic Insights\u003c/b\u003e. To examine the differences in PFAS adsorption between conventional adsorbents and Zn-based EC process, we introduced the selective adsorption coefficient (\u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e) as a measure of PFAS adsorbability. A \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e value greater than 1 for PFAS indicates that it will be preferentially adsorbed. The coefficient is calculated using the following Eq.\u0026nbsp;\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$${K}_{\\text{d}}=\\frac{{\\omega }_{\\text{a}}}{{\\omega }_{\\text{b}}}/\\frac{(1-{\\omega }_{\\text{a}})}{(1-{\\omega }_{\\text{b}})}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\omega }_{\\text{b}}\\)\u003c/span\u003e\u003c/span\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\omega }_{\\text{a}}\\)\u003c/span\u003e\u003c/span\u003e represent the molar concentration fraction of a specific PFAS to the total 107 PFASs in the fluorochemical wastewater before and after adsorption, respectively. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea illustrates the \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values of PFA694E for all 107 PFASs measured in the fluorochemical wastewater, which are located around 1 despite their wide variation in chemical structure and concentration. This finding is consistent with previous studies suggesting AER can adsorb a variety of ionizable PFAS\u003csup\u003e37, 38\u003c/sup\u003e. However, the lack of strong specific affinity between AER and PFAS also makes it highly susceptible to interference from coexisting competing constituents, thereby reducing its effectiveness in removing PFAS in practical complex wastewater matrices. It is interesting to note that the Zn-based EC selectively adsorbs highly hydrophobic PFASs and ignores hydrophilic PFAS (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). Quantitative structure-activity relationship (QSAR) model fitting revealed a robust correlation between \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values and log\u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e values (\u0026gt;\u0026thinsp;4) of PFAS, with the equation \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e= 9.5 \u0026times; log\u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e \u0026minus;\u0026thinsp;38.6 (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.849). It should be highlighted that all short-chain I\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAAs (C2\u0026thinsp;~\u0026thinsp;C6) were preferentially adsorbed with \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e \u0026gt;3, suggesting that all of them should be highly hydrophobic. However, the log \u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e values (blue circle) estimated by the EPI Suite software for all short-chain I\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAAs are less than 4. Due to the lack of training set, current software has poor accuracy in predicting the physicochemical properties of novel PFAS. Since the log \u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e values (no real measurements available) of all PFASs are derived from the software predictions, inaccurately predicted values for some novel PFASs are the main reason for their larger deviations from the fitted curves in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, e.g., ether-PFAAs. In other words, these results suggest that the introduction of other atoms or structures, such as iodine atoms or ether groups, significantly alters the physicochemical properties of parent PFAS. This will be discussed in more detail later.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo elucidate the selective adsorption mechanism in the Zn-based EC process, we further investigated the adsorption kinetics of 6 PFASs with varying chain-lengths in simulated solution. Zinc hydroxide flocs presented extremely rapid adsorption of all 6 PFASs with equilibrium time (\u003cem\u003et\u003c/em\u003e\u003csub\u003eeq\u003c/sub\u003e) less than of 2 min (Supplementary Fig.\u0026nbsp;8a), whereas AC and AER widely used in current applications had \u003cem\u003et\u003c/em\u003e\u003csub\u003eeq\u003c/sub\u003e of tens of hours or more (Supplementary Table\u0026nbsp;3). The observed maximum adsorption amount (\u003cem\u003eq\u003c/em\u003e\u003csub\u003em\u003c/sub\u003e, mmol PFAS\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e zinc hydroxide flocs) was monotonically correlated with their hydrophobicity and chain-lengths (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb and Supplementary Fig.\u0026nbsp;8b), suggesting a pivotal role of hydrophobic interaction. The weakly hydrophobic PFBA (C4, log \u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e = 2.14) had a \u003cem\u003eq\u003c/em\u003e\u003csub\u003em\u003c/sub\u003e \u0026lt; 0.1 mmol\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the moderately hydrophobic PFH\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003eA (C6, log \u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e = 3.48) had an elevated \u003cem\u003eq\u003c/em\u003e\u003csub\u003em\u003c/sub\u003e of 1.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 mmol\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the highly hydrophobic PFDA (C10, log \u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e = 6.15) achieved an ultra-high \u003cem\u003eq\u003c/em\u003e\u003csub\u003em\u003c/sub\u003e of \u0026gt;\u0026thinsp;23 mmol\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (\u0026gt;\u0026thinsp;10 g\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). For the most discussed PFOA (log \u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e=4.81), its \u003cem\u003eq\u003c/em\u003e\u003csub\u003em\u003c/sub\u003e was estimated to be 6.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4 mmol\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (2.6 g\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). To the best of our knowledge, these achieved \u003cem\u003eq\u003c/em\u003e\u003csub\u003em\u003c/sub\u003e are the highest of all values reported in the literature, which are over an order-of-magnitude higher than the theoretical maximum adsorption capacity derived from the adsorption model fitting that of the data for the benchmark AC and several times higher than that of the AER (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec and Supplementary Table\u0026nbsp;3). Furthermore, the dynamic adsorption capacity (\u003cem\u003eq\u003c/em\u003e\u003csub\u003edyn\u003c/sub\u003e= \u003cem\u003eq\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e/\u003cem\u003et\u003c/em\u003e) was more than 1\u0026thinsp;~\u0026thinsp;4 orders of magnitude higher than literature-reported adsorbents (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003eThe SEM characterizations in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed and Supplementary Fig.\u0026nbsp;9 showed that the presence of PFAS affects the structural morphology of zinc hydroxide flocs generated in-situ by Zn-based EC. The fresh zinc hydroxide flocs were dispersed nanoflakes, while the Zn hydroxide flocs with adsorbed PFOA became dense. PFOA seemed to act as a binder to tightly aggregate and completely cover the dispersed Zn hydroxide flocs, as evidenced by the EDX results (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). The F/Zn atomic ratio of Zn hydroxide flocs with adsorbed PFOA was up to 7.5. In mineral flotation, the non-polar ends of long hydrocarbon chain traps adsorbed on the surface of mineral particle associate with each other to form semi-micelles, i.e., semi-micellar adsorption, by van der Waals forces\u003csup\u003e39\u003c/sup\u003e. Similar to the mineral particles, zinc hydroxide flocs generated in-situ by electrocoagulation exhibit natural hydrophobicity. Inspired by the mineral flotation process, we propose a mechanism, i.e., hydrophobic force-driven semi-micellar adsorption, to clarify how Zn-based EC selectively absorbs hydrophobic PFAS (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee). Initially, benefiting from the highly dispersed and high specific surface area of zinc hydroxide flocs (minerals), hydrophobic PFAS (trapping agent) can quickly move to their surface via hydrophobic force. Then, van der Waals forces induce high surface activity PFAS (e.g., long-chain PFAS) to create semi-micelles or micelles on their own, which leads to a significant improvement in their adsorption capabilities and ultimately results in ultra-high adsorption capacities. Results from physicochemical characterizations of the PFAS-adsorbed zinc hydroxide flocs and theoretical calculations provided evidence for the proposed mechanism. Hydrophobic PFAS molecules would be adsorbed flat on the surface of zinc hydroxide flocs to minimize water-fluorine interactions. Based on the molecular size of PFAS optimized by the Gaussian 09 (Supplementary Fig.\u0026nbsp;10), the spatial maximum number of PFOA (11.61 \u0026times; 4.05 \u0026times; 3.98 \u0026Aring;) and PFDA (13.72 \u0026times; 4.05 \u0026times; 3.96 \u0026Aring;) molecules per unit surface area for a monolayer of coverage was estimated to be less than 2.1 and 1.8 molecules per nm\u003csup\u003e2\u003c/sup\u003e, respectively, assuming that the long axis (C-C chain) of the molecule is parallel to the surface and no space exists between molecules. Conversion of the molar mass of PFAS adsorbed per unit surface area results in approximately 18 PFOA molecules and \u0026gt;\u0026thinsp;65 PFDA molecules per nm\u003csup\u003e2\u003c/sup\u003e of the zinc hydroxide flocs (BET\u0026thinsp;=\u0026thinsp;213.1\u0026thinsp;\u0026plusmn;\u0026thinsp;10.6 m\u003csup\u003e2\u003c/sup\u003e\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, Supplementary Fig.\u0026nbsp;10) according to their \u003cem\u003eq\u003c/em\u003e\u003csub\u003em\u003c/sub\u003e values, which is over an order-of-magnitude higher than the maximum number of molecules for a monolayer of coverage. The XPS and SEM-EDX characterizations further confirmed that the surface of zinc hydroxide flocs was tightly covered by the adsorbed-PFAS, as demonstrated by the intense F-element signals and significantly reduced Zn-element signals in Supplementary Fig.\u0026nbsp;9. The measured F/Zn atomic ratios of the zinc hydroxide flocs with adsorbed PFOA (PFNA and PFDA) were 6.35\u0026thinsp;~\u0026thinsp;7.54 (7.35\u0026thinsp;~\u0026thinsp;7.9 and 8.85\u0026thinsp;~\u0026thinsp;9.96) (Supplementary Table\u0026nbsp;4), and it is clear that these highly hydrophobic PFASs were multilayered adsorbed. Weakly hydrophobic PFASs, usually the short-chain PFAS, have low surface activity and are unable to form semi-micelles or micelles on the surface of zinc hydroxide flocs. Furthermore, the electrostatic adsorption can also be neglected because of the zinc hydroxide flocs had a negative or weakly positive zeta potential (Supplementary Fig.\u0026nbsp;12). As a result, their adsorption capacity is significantly lower compared to hydrophobic PFAS. In principle, this unique mechanism would also enable the Zn-based EC to avoid adverse effects from other coexisting contaminants and DOMs in solution, as these competing constituents tend not to be highly hydrophobic. Therefore, the Zn-based EC could be an effective technique for treating highly complex waste streams such as aqueous fire forming foams (AFFFs) solution and still bottoms liquid waste containing high concentrations of PFAS from adsorbent regeneration.\u003c/p\u003e \u003cp\u003e \u003cb\u003eEffect of the Structure of PFASs on their Adsorbability.\u003c/b\u003e As the use of legacy perfluorinated C\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003eF\u003csub\u003e2\u003cem\u003en\u003c/em\u003e+1\u003c/sub\u003e\u0026ndash;X (X\u0026thinsp;=\u0026thinsp;COO\u003csup\u003e\u0026minus;\u003c/sup\u003e or SO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e) compounds has been restricted, many alternative PFASs have been created and extensively applied for fluorochemical production. The main substitution strategy involves inserting \u0026ndash;H, \u0026ndash;Cl, \u0026ndash;OH or \u0026ndash;O\u0026ndash; into perfluorinated molecules, which reduces the \u0026ldquo;effective length\u0026rdquo; of fluorinated chain segments, to reduce their persistence. Here, we sought to explore the adsorbability of various PFASs in terms of their chemical structure, which may provide critical guidance for the design of alternative PFASs that are easier to eliminate. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea illustrated the relationship between the \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e value of PFASs and the ratio of F/C as well as F/H in their chemical structure. The preferentially adsorbed PFASs were mainly concentrated in the upper-right quadrant region with high F/C and F/H ratios. This suggests that for a PFAS to be preferentially adsorbed, it must satisfy two structural conditions: (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) a high degree of fluorination (e.g., F/C\u0026thinsp;\u0026gt;\u0026thinsp;1.6), and (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) a large number of fluorine atoms (e.g., \u0026gt;\u0026thinsp;8). It is evident that the physical and chemical properties of PFASs, as well as their environmental behavior, are profoundly determined by the number and distribution of [CF\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1\u0026thinsp;~\u0026thinsp;3) and [CH\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1\u0026thinsp;~\u0026thinsp;3) in their chemical structure. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb showed how the length of the [CF\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] chain and the number of hydrogen atoms attached to the carbon in the PFAS molecule affect its \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e. Typically, PFAS with 6 or more [CF\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] units would be preferentially adsorbed. However, [CH\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] groups may significantly reduce their adsorbability. For instance, although some PFASs have 7 or 8 [CF\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] units in their chemical structure, but the existence of multiple [CH\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] groups (e.g., \u0026gt;\u0026thinsp;5) can offset the benefits of the [CF\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] units. Ether-PFAAs are the most abundant class of PFASs in the fluorochemical wastewater. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec illustrates the impact of the number of carbon-ether bonds (C\u0026ndash;O\u0026ndash;C) on the \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e value of Ether-PFAAs (with PFCA and iodinated PFPESA as controls). In general, the existence of C\u0026ndash;O\u0026ndash;C bonds is likely to result in lower adsorbability regardless of the structure of the Ether-PFAAs. For instance, the \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e value of PFPECA (green circle) was consistently lower than that of the corresponding chain-length of perfluoroalkyl acid (blue circle), and a plurality of C\u0026ndash;O\u0026ndash;C bonds further reduced its \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e value. These results clearly indicated that PFAS alternatives with \u0026ndash;H and/or \u0026ndash;O\u0026ndash; introduced into the perfluorinated structure (C\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003eF\u003csub\u003e2\u003cem\u003en\u003c/em\u003e+1\u003c/sub\u003e\u0026ndash;) tend to be less adsorbable.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eNotably, the behavior of the novel I\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAAs was markedly different. Their chemical structure contains 1 to 3 [CH\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] units and no more than 4 [CF\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e] groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), placing them in the lower-left quadrant region with low F/C and F/H ratios in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea. In principle, they should not be preferentially adsorbed. However, all measured I\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAAs had \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values much greater than 1. For example, 4:4 I-FTOA (CH\u003csub\u003e2\u003c/sub\u003eI[CF\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e4\u003c/sub\u003e[CH\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCOOH) has a composition of 3[CH\u003csub\u003e2\u003c/sub\u003e] groups and only 4[CF\u003csub\u003e2\u003c/sub\u003e] units, yet it had an extremely high \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e value of 17.39. Similarly, 3:3 I-FTHxA (CF\u003csub\u003e2\u003c/sub\u003eI[CF\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003e[CH\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCOOH) with even less [CF\u003csub\u003e2\u003c/sub\u003e] also had a \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e value of 3.75. Both of them had higher \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values than the corresponding chain-length perfluorocarboxylic acids, i.e., PFOA (\u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=10.9) and PFHxA (\u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=0.53), respectively. Furthermore, we observed that the short-chain and ultra-short-chain iodinated ether-FTSAs (I-FTPESAs) were also preferentially adsorbed (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). For example, 1:1 I-FTOPrSA (CH\u003csub\u003e2\u003c/sub\u003eI-O-CF\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003eH) and 2:2 I-FTOPeSA (CF\u003csub\u003e2\u003c/sub\u003eICH\u003csub\u003e2\u003c/sub\u003e-O-CH\u003csub\u003e2\u003c/sub\u003eCF\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003eH) achieved \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values of 5.28 and 3.68, respectively. It is widely recognized that chlorinated PFAS (Cl\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAS), as a class of alternative PFAS, have been developed and used extensively in commercial products and industrial materials for decades\u003csup\u003e40\u003c/sup\u003e. Ten Cl\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFASs (Supplementary Table\u0026nbsp;1) including 8 Cl\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFCAs (ranging from C2 to C9) and 2 chloroperfluoropolyether carboxylates (Cl\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFPECAs) found in the fluorochemical wastewater. The study found that Cl\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAS and non-chlorinated PFAS have similar or slightly higher \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values, e.g., Cl-PFOA (CF\u003csub\u003e2\u003c/sub\u003eCl[CF\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e6\u003c/sub\u003eCOOH, \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=11.65) \u003cem\u003evs\u003c/em\u003e. PFOA (\u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=10.9), but none of the short-chain Cl-PFCAs showed preferential adsorption (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). These results suggested that the Cl substitution (Cl\u0026rarr;F) has little effect on the adsorbability of PFAS, but substitution of even one fluorine atom in PFAS with an iodine atom (I\u0026rarr;F) causes a dramatic shift in their chemical properties. This finding is significant because it suggests that the potential environmental impacts of I\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAAs may differ significantly from those of traditional non-iodinated PFAS. A schematic diagram (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee) was drawn to depict the potential effect of inserting \u0026ndash;H, \u0026ndash;Cl, \u0026ndash;I or \u0026ndash;O\u0026ndash; into the structure of PFAS molecules on their adsorbability. The novel structural feature and important environmental relevance (e.g., several hundred \u0026micro;g\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the fluorochemical wastewater) of iodinated PFAS require an adequate understanding of their environmental behavior and fate. Alternatively, a recent study by Jin et al.\u003csup\u003e41\u003c/sup\u003e showed that the substitution of F with Cl significantly improved the biodegradability and reduced the toxicity of PFAS. Replacing F with I could further enhance this effect due to the larger radius of the iodine atom. Therefore, it may be possible to design alternative iodinated PFAS that are readily degradable and less toxic.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eFull-Scale System Simulations of Zn-based EC-coupled PFA694E Adsorption Bed\u003c/h2\u003e \u003cp\u003eTo confirm the efficacy of the treatment-train strategy of Zn-based EC-coupled existing full-scale conventional adsorption units, a rapid small-scale column test (RSSCT) breakthrough experiment with fluorochemical wastewater was conducted as a proof-of-concept experiment. The constant diffusion model was used to scale down the operating parameters of the full-scale PFA694E beds to the RSSCT (Method section and Supplementary Table\u0026nbsp;5). First, we examined the breakthrough curve of the PFA694E bed fed by a simulated solution containing 25 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of PFOA, at a concentration consistent with fluorochemical wastewater. The results showed that the bed values (BV) of BV\u003csub\u003e80\u003c/sub\u003e were estimated to be 15\u0026times;10\u003csup\u003e3\u003c/sup\u003e BVs (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). Unexpectedly, the PFA694E bed fed with untreated fluorochemical wastewater was breached in a very short time, with the values of BV\u003csub\u003e10\u003c/sub\u003e, BV\u003csub\u003e50\u003c/sub\u003e and BV\u003csub\u003e80\u003c/sub\u003e being only 0.39\u0026times;, 0.54\u0026times; and 0.66\u0026times;10\u003csup\u003e3\u003c/sup\u003e BVs, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). The concentration of TOF and other 106 PFASs in the effluent of the PFA694E bed was also monitored. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, the TOF profile of the PFA694E bed was also rapidly breached, suggesting that the quick breakthrough occurred for all PFASs. When fed only 1.03\u0026times;10\u003csup\u003e3\u003c/sup\u003e BV of untreated fluorochemical wastewater, the PFA694E bed showed almost complete breakthrough of the monitored 107 PFASs (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec and Supplementary Fig.\u0026nbsp;13), and the effluent TOF removal was less than 10% (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). In contrast, Zn-based EC-coupled PFA694E bed adsorption treatment-train strategy achieved at least 50% removal of TOF throughout the treatment. At the point of 1.03\u0026times;10\u003csup\u003e3\u003c/sup\u003e BV, the treatment-train strategy was still able to remove most of the monitored 107 PFASs (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec and Supplementary Fig.\u0026nbsp;13) and achieved 70% removal of TOF (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). For example, nearly 99% of PFOA was removed by the treatment-train strategy with an effluent concentration of only 0.3 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, compared to 22.3 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the effluent from the PFA694E bed fed with untreated fluorochemical wastewater. As a result, the front-end Zn-based EC treatment resulted in a 12.3-fold increase in BV\u003csub\u003e80\u003c/sub\u003e for PFOA, with a value of 7.77\u0026times;10\u003csup\u003e3\u003c/sup\u003e BVs (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn addition to PFOA, we also monitored the breakthrough curves of 22 other representative PFASs with carbon-chain lengths ranging from 4 to 9 in fluorochemical wastewater at relatively high concentrations. As expected, the front-end Zn-based EC treatment significantly delayed the full breakthrough of the PFA694E bed (Supplementary Fig.\u0026nbsp;14), resulting in a 2.5-fold (PFBA) to 13.6-fold (Cl-PFOA) increase in BV80 values (Supplementary Fig.\u0026nbsp;15). Overall, PFASs with high log\u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e values are more likely to achieve higher enhancement folds. A comparison of PFAS mass loading on a molar concentration basis identified distinct adsorption behaviors on the PFAE694E bed when combined with the front-end Zn-based treatment. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed, the cumulative adsorption mass profiles of all PFASs flattened, indicating that the PFA694E bed had reached its maximum PFAS adsorption capacity during the RSSCT test. The PFA694E bed retained a final PFAS loading of 41.2 \u0026micro;mol\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e adsorbent fed with untreated fluorochemical wastewater, consisting of 81.1% of PFOA (compared to 76.5% PFOA in feed, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee) and 18.9% of other 22 PFASs. Although the front-end Zn-based EC treatment resulted in a 76% reduction in the total concentration of the 23 PFASs in the fluorochemical wastewater, from 75 \u0026micro;M to 18 \u0026micro;M (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee), the final loading of the 23 PFASs on the PFA694E bed, was even higher than that of the feed of untreated fluorochemical wastewater, i.e., 42.1 \u003cem\u003evs\u003c/em\u003e. 41.2 \u0026micro;mol\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef,\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg). More importantly, the total loading of the other 22 PFASs was dramatically increased by over 3 times to 22.9 \u0026micro;mol\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, accounting for 54.3% of the final loading of the PFA694E bed. Expanded enlarged petal plots in Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef,\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg showed significant increases in loadings for most of the 23 PFASs, except for several highly hydrophobic PFASs (such as PFOA, PFNA, 3:3 I-FTHxA and 4:4 I-FTOA) whose concentrations were dramatically or nearly completely removed by the front-end Zn-based EC treatment. These results highlighted that to maximize the usable adsorbent bed service-life and achieve broad-spectrum removal of dozens or hundreds of PFAS in real-world complex scenarios, a potential treatment configuration could use a combination of Zn-based EC treatment and adsorbent in series.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eTechno-Economic Analysis and Life-cycle Environmental Impact\u003c/h2\u003e \u003cp\u003eThe application prospects of the proof-of-concept treatment-train strategy were also evaluated based on carbon-footprint and techno-economic analysis. In this study, the PFA694E bed was operated as a single-use adsorbent, and the spent PFA694E and zinc hydroxide flocs with adsorbed PFAS would be incinerated. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea and Supplementary Table\u0026nbsp;5, the operational cost of the Zn-based EC process was approximately \u003cspan\u003e$\u003c/span\u003e1.43 per m\u003csup\u003e3\u003c/sup\u003e treated under a treatment time of 20 min, consisting of \u003cspan\u003e$\u003c/span\u003e1.14 for zinc metal cost, \u003cspan\u003e$\u003c/span\u003e0.1 for the electricity, and \u003cspan\u003e$\u003c/span\u003e0.19 for the incineration of zinc hydroxide flocs (assuming 10% water content). Recycling the incineration byproduct, ZnO, as a resource can significantly reduce the cost of Zn-based EC treatment to \u003cspan\u003e$\u003c/span\u003e0.1. Assuming a base case scenario where adsorption bed change-out criteria are dictated by PFOA removal less than 90%, the predicted operating cost of the treatment-train strategy was \u003cspan\u003e$\u003c/span\u003e4.55 (\u003cspan\u003e$\u003c/span\u003e3.22 when ZnO recycled) per m\u003csup\u003e3\u003c/sup\u003e treated. In the absence front-end Zn-based EC treatment, the estimated operating cost would greatly increase to \u003cspan\u003e$\u003c/span\u003e49.94 per m\u003csup\u003e3\u003c/sup\u003e treated for the PFA694E bed system, over an order-of-magnitude higher than those of the treatment-train strategy.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA cradle-to-grave life-cycle assessment was employed to compute the carbon-footprint of both the Zn-based EC and the PFA694E adsorption bed systems. The PFA694E adsorption bed system had a carbon-footprint of 13.75 KgCO\u003csub\u003e2\u003c/sub\u003e per m\u003csup\u003e3\u003c/sup\u003e treated under the change-out criteria of \u0026gt;\u0026thinsp;90% of PFOA removal (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb and Supplementary Table\u0026nbsp;5). Setting the same change-out criteria, the carbon-footprint of the treatment-train strategy, i.e., 3.93 KgCO\u003csub\u003e2\u003c/sub\u003e per m\u003csup\u003e3\u003c/sup\u003e treated, was only 28.6% of that of the PFA694E adsorption bed alone. Unlike PFA694E, which is considered a \u0026ldquo;high-carbon\u0026rdquo; adsorbent due to the large amounts of CO\u003csub\u003e2\u003c/sub\u003e emitted during its incineration (1.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 KgCO\u003csub\u003e2\u003c/sub\u003e per KgPFA694E), the inorganic zinc hydroxide flocs generated in-situ by Zn-based EC are essentially a \u0026ldquo;zero-carbon\u0026rdquo; adsorbent. Additionally, CIC and TOC/N analyzer tests showed that the PFA694E contains 0.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 mmol S, 2.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 mmol N, and 0.39\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 mol Cl per gram, suggesting that incineration treatment of the spent PFA694E will produce significant amounts of other pollutants, such as SO\u003csub\u003e2\u003c/sub\u003e, ozone, smoke particles, carcinogenics, and NO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e. Significantly, Zn-based EC has a much lower environmental impact compared to the reported adsorbents mainly carbon material-based adsorbents\u003csup\u003e42\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eCritical Implications for PFAS Research\u003c/h2\u003e \u003cp\u003eThe importance of addressing PFAS emissions from industrial production should be of great concern, as it is still the most important source of PFAS entering the environment in many countries and regions, such as China. However, the high concentration and diversity of PFAS in industrial wastewater, as well as the complex background matrix, pose significant challenges to existing adsorption technologies. This study is the critical initial step in developing a treatment-train strategy that couples a novel Zn-based EC process with existing adsorption devices (e.g., AER and AC) to achieve the efficient and broad-spectrum capture of hundreds of PFAS with diverse properties from a fluorochemical industrial park effluent. The zinc hydroxide flocs generated in-situ by Zn-based EC can selectively and rapidly (\u003cem\u003et\u003c/em\u003e\u003csub\u003eeq\u003c/sub\u003e\u0026lt; 2 min) adsorb hydrophobic PFAS (log\u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e \u0026gt;4) via a semi-micellar adsorption mechanism similar to that of mineral flotation. This unique multilayered adsorption mechanism outweighs the conventional adsorbents that are based on their limited adsorption sites to remove PFAS, and results in Zn-based EC with the highest adsorption capacities (e.g., 6.4 mmol PFOA per gram of zinc hydroxide flocs) to hydrophobic PFASs among all adsorbents reported. Meanwhile, the Zn-based EC is also capable of substantially removing the coexisting competing constituents such as DOMs and NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e to the conventional adsorbents. These features are quite important for the subsequent tandem adsorption processes, as they greatly extend their lifetime, enhance their adsorption selectivity and adsorption capacity for short-chain PFAS, and reduce operating costs. Furthermore, the zinc hydroxide flocs are essentially inorganic \u0026ldquo;zero-carbon\u0026rdquo; adsorbents that significantly reduce the environmental impact of the treatment-train strategy. The rose chart (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec) demonstrates that the treatment-train strategy is superior to the PFA694E adsorption on almost all perspectives (for details, see Supplementary Table\u0026nbsp;6), such as PFAS removal efficiency and broad-spectrum, as well as economics and environmental impact, and has less solid waste generation. Therefore, the treatment-train methodology could be a potential upgrade of existing adsorption devices.\u003c/p\u003e \u003cp\u003eOn the other hand, fluorochemical-related industries have been crucial to modern socio-economics. As the use of traditional PFASs is gradually restricted, more and more new alternatives are being developed and widely used. However, many of them have come under global scrutiny of new concerns, e.g., GenX, for exhibiting similar persistence and biotoxicity as traditional PFASs. For the future design of specialty PFAS products, we need to maximize their eliminability and reduce their biotoxicity and persistence while maintaining desirable properties. Our experimental results evidence the inclusion of \u0026ndash;H and \u0026ndash;O\u0026ndash; into perfluorinated structure decreases the adsorbability compared to the parent PFAS. A recent study by Jin et al.\u003csup\u003e41\u003c/sup\u003ehighlighted that replacing one or more F atoms with Cl atoms in PFAS structures, known as Cl\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAS, could be an effective strategy to improve their biological and chemical degradability without increasing toxicity. In this study, Cl\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAS does not show a significant improvement in adsorbability; rather, the substitution of even a single iodine atom impressively alters the nature of the parent PFAS, greatly enhancing its hydrophobicity and allowing iodinated PFAS (I\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAS) to be readily adsorbed. Additionally, we also observed the degradation of I\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e-PFAS under natural conditions (data not shown). These novel findings provide not only, for the first time, critical fundamental knowledge into the assessment of the environmental fate of iodinated PFAS, but can also help to design environmentally-friendly PFAS and achieve sustainable management of fluorochemicals.\u003c/p\u003e \u003c/div\u003e"},{"header":"Methods","content":"\u003cp\u003e \u003cb\u003eSamples and Chemicals\u003c/b\u003e. Wastewater samples were taken from the reverse osmosis (RO) concentrate of mixed effluents from multiple production plants of a mega fluorochemical industrial park (FIP) in northern China, where various PFASs were extensively used during the production of polymer fluoropolymers, including polyperfluoroethylene propylene (FEP), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF). Ammonium acetate (NH\u003csub\u003e4\u003c/sub\u003eAC), sodium chloride (NaCl), and PFAS chemicals such as PFOA and PFOS used in the experiments were purchased from Sigma-Aldrich Chemical Co., Ltd. The mass-labeled perfluorinated compounds EISs solution (MPFAC-C-ES, 13 \u003csup\u003e3\u003c/sup\u003eC-labeled PFASs) were purchased from Wellington Laboratories Inc. Details of these internal standards are provided in Supplementary Table\u0026nbsp;7. Methanol (MeOH) and acetonitrile (ACN) were chromatographic grade and purchased from Merck Corp. Granular activated carbon (GAC, 20\u0026thinsp;~\u0026thinsp;40 mesh) was purchased from Macklin Biochemical Co., Ltd; PFA694E anion exchange resin (AER) was obtained from Purolite\u0026reg; (Bala Cynwyd, PA, USA).\u003c/p\u003e \u003cp\u003e \u003cb\u003eElectrocoagulation\u003c/b\u003e, \u003cb\u003eBatch Adsorption and RSSCT Experiments\u003c/b\u003e. The electrocoagulation (EC) reactor was composed of a cylindrical EC cell (8 cm diameter and 15 cm height) with a 500 mL volume, as shown in Supplementary Fig.\u0026nbsp;1a. A metal (Zn, Al or Fe) sheet of 100 cm\u003csup\u003e2\u003c/sup\u003e surface area was used as anode, while a 304 stainless steel rod of 0.3 cm diameter was used as the cathode, with a distance of 3 cm between the electrodes. In each run, 300 mL of wastewater or simulated solution was added, and powered by a DC power (DH1718G-4, Dahua, China) under a constant current mode. During the EC treatment, the solution pH value was not adjusted or controlled. Prior to use, AC (50\u0026thinsp;~\u0026thinsp;60 mesh) and PFA694E (50\u0026thinsp;~\u0026thinsp;60 mesh) were repeatedly washed with DI water, followed by drying at 150℃ for 4 h and stored in a dryer. Adsorption isotherm tests were conducted by AC and PFA694E with PFOA solution of a wide range from 10 to 400 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (AC) or 100 to 600 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (PFA694E) for 24 h. All isotherm data were fitted by the Langmuir and/or Freundlich model. The adsorption treatment of fluorochemical wastewater experiments was also conducted. All adsorption experiments were performed in the polypropylene centrifuge tubes (150 mL) at room temperature on a vortex plate at 500 rpm. The adsorbent dose was 330 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eRapid small-scale column test (RSSCT) experiments (Supplementary Fig.\u0026nbsp;1b) were designed based on the constant diffusivity mode. Columns were organic glass made (6.4 mm inner diameter and 50 mm height) with a maximum volume of 1.66 mL. The PFA694E was crushed and sieved to 0.282\u0026thinsp;~\u0026thinsp;0.25 mm, which allowed the column diameter/PFA694E particle diameter ratio to be \u0026gt;\u0026thinsp;8\u0026thinsp;~\u0026thinsp;10 to eliminate wall or channel effects. Filters (200-mesh) on both sides of the column are to distribute water flow and prevent the leading of the AER particles and during the column testing. The columns were operated in an up-flow configuration mode of a rate a mL\u0026middot;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e using a peristaltic pump. The column was thoroughly cleaned using DI water for 24 h before the experiment. The specific design formula was expressed as Eq.\u0026nbsp;\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and parameters can be found in Supplementary Table\u0026nbsp;5:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\frac{{\\text{E}\\text{B}\\text{C}\\text{T}}_{SC}}{{\\text{E}\\text{B}\\text{C}\\text{T}}_{LC}}={\\left(\\frac{{\\text{d}}_{SC}}{{\\text{d}}_{LC}}\\right)}^{2}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere EBCT refers to the empty bed contact time (min); \u003cem\u003eSC\u003c/em\u003e and \u003cem\u003eLC\u003c/em\u003e refer to the RSSCT column and full-scale adsorber, respectively; d represents the diameter of the adsorbent (mm).\u003c/p\u003e \u003cp\u003eIn all cases, triplicate experiments were conducted, and samples were collected and filtered by a 0.22 \u0026micro;m cellulose membrane (\u0026gt;\u0026thinsp;95% PFAS recovery). Additionally, solid phase loading (\u0026micro;mol PFAS per adsorbent) of PFAS was calculated as follows:\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\text{S}\\text{o}\\text{l}\\text{i}\\text{d} \\text{p}\\text{h}\\text{a}\\text{s}\\text{e} \\text{l}\\text{o}\\text{a}\\text{d}\\text{i}\\text{n}\\text{g}=\\frac{\\int \\left({\\text{C}}_{0}-{\\text{C}}_{effluent}\\right)\\text{d}\\text{V}}{\\text{m}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere C\u003csub\u003e0\u003c/sub\u003e and C\u003csub\u003e\u003cem\u003eeffluent\u003c/em\u003e\u003c/sub\u003e refer to the PFAS concentrations in the influent and effluent, respectively; V is the wastewater treated; m is the mass of adsorbent. The dissolved zinc dosage (mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) was calculated as a function of electrocoagulation time using the following equation:\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$\\text{Z}\\text{i}\\text{n}\\text{c} \\text{d}\\text{o}\\text{s}\\text{a}\\text{g}\\text{e}=\\frac{1000}{\\text{V}}\\times \\frac{\\text{I}\\times { \\text{t}}_{\\text{E}\\text{C} }}{n\\text{F}}\\times \\text{M} \\times {\\eta }$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere I and t\u003csub\u003eEC\u003c/sub\u003e refer to the applied current and time during electrocoagulation, respectively; F is the Faraday\u0026rsquo;s constant; \u003cem\u003en\u003c/em\u003e is the number of electrons in Zn \u0026minus;\u0026thinsp;2\u003cem\u003ee\u003c/em\u003e\u0026rarr; Zn\u003csup\u003e2+\u003c/sup\u003e; M (65 g\u0026middot;mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) refers to the relative molar mass of zinc; η refers the current efficiency of Zn \u0026minus;\u0026thinsp;2\u003cem\u003ee\u003c/em\u003e\u0026rarr; Zn\u003csup\u003e2+\u003c/sup\u003e, which is determined to 0.91 in the fluorochemical wastewater used in this study.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFlocs Characterization\u003c/b\u003e. The zinc hydroxide flocs were collected and freeze-dried. The Brunauer-Emmett-Teller (BET) surface areas of the dried flocs were measured using a Micromeritics ASAP 2460. Field-emission scanning electron microscopy (FESEM, ZEISS Sigma 300) coupled with energy dispersive X-ray spectroscopy (EDX) was used for the morphology and elemental analyses. X-ray photoelectron spectroscopy (XPS) spectra of the flocs were measured by an ESCALAB 250Xi XPS system with a monochromatic Al Kα source. The zeta potentials of zinc hydroxide flocs during EC were measured by a Malvern zeta potential analyzer (Zetasizer Nano ZS90).\u003c/p\u003e \u003cp\u003e \u003cb\u003ePFAS and Wastewater Analysis\u003c/b\u003e. Concentrations of 107 PFASs were analyzed using an LC-Q-Orbitrap-HRMS system comprised of a Dionex ultraperformance liquid chromatograph (UPLC) and a Q-Extractive Plus mass spectrometer equipped with a heated-electrospray ionization (HESI) source (Thermo-Fisher Scientific, USA). The UPLC separation was carried out by an Acquity UPLC\u0026reg; BEH C18 column (2.1 100 mm, 1.7, Waters) using a gradient composition of solvent A (ACN) and solvent B (2 mM NH\u003csub\u003e4\u003c/sub\u003eAC in DI water) at a flow rate of 0.25 mL\u0026middot;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The gradient expressed as the concentration of solvent A was as follows: 0\u0026thinsp;\u0026minus;\u0026thinsp;0.2 min, hold at 20% A; 0.2\u0026thinsp;\u0026minus;\u0026thinsp;8 min, a liner increase from 20% A to 80% A; 8\u0026thinsp;\u0026minus;\u0026thinsp;10 min, a liner increase from 80% A to 95% A; 10\u0026thinsp;\u0026minus;\u0026thinsp;12 min, hold at 95% A; 12\u0026thinsp;\u0026minus;\u0026thinsp;12.1 min, a liner decrease from 95% A to 20% A; 12.1\u0026thinsp;\u0026minus;\u0026thinsp;15 min, and hold at 20% A. The sample volume injected was 5 \u0026micro;L. The HESI source was operated in negative ionization mode with the spray potential at 3.2 kV, the capillary temperature at 320\u0026deg;C, the aux gas heater temperature at 350\u0026deg;C, and the sheath and auxiliary gas flow rate of 45 arb and 10 arb, respectively. Each sample was spiked with EISs solution (5 \u0026micro;g\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of each \u003csup\u003e13\u003c/sup\u003eC-labeled PFAS, Supplementary Table\u0026nbsp;6) as the internal standard for analysis. Details concerning PFASs analysis and data processing can be found in our previous studies\u003csup\u003e32\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eConcentrations of total organic fluorine (TOF) in wastewater, and sulfur and chlorine content in PFA694E were detected using a combustion-ion chromatography (CIC) equipped with an automatic quick furnace (AQF-2100H), a combustion monitor (CM-210), and an ion chromatography system (Dionex ICS-5000). The Dionex ICS-5000 was also employed to measure the cations in wastewater including SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e, Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e, F\u003csup\u003e\u0026minus;\u003c/sup\u003e and NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e. More information about the CIC and ion chromatography analysis can be found in our previous studies. Concentrations of total organic carbon (TOC) in wastewater, and carbon and nitrogen content in PFA694E were measured by a multi N/C UV TOC analyzer (Analytic Jena, Germany).\u003c/p\u003e \u003cp\u003e \u003cb\u003eTechno-Economic Analysis (TEA) and Life-cycle Environment Impact Assessment (LCEIA)\u003c/b\u003e. The electric energy (\u003cem\u003eE\u003c/em\u003e, kWh\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e) of the Zn-based EC was calculated by Eq.\u0026nbsp;\u003cspan refid=\"Equ5\" class=\"InternalRef\"\u003e5\u003c/span\u003e:\u003cdiv id=\"Equ5\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ5\" name=\"EquationSource\"\u003e\n$$E=\\frac{\\text{U}\\times \\text{I}}{\\text{V}}\\times {\\text{t}}_{\\text{E}\\text{C}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e5\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere U refers to average voltage during electrocoagulation. The operating costs include direct cost of electricity, adsorbents and spent adsorbents incineration treatment. For detailed calculations of operating costs for the Zn-based EC, PFA694E bed, and treatment-train process, see Supplementary Text 1. A cradle-to-grave life-cycle assessment was employed to compute the carbon-footprint of both the Zn-based EC and the PFA694E adsorption bed processes. In this study, we only consider the carbon footprints (Kg CO\u003csub\u003e2\u003c/sub\u003e eq.). For detailed calculations, see Supplementary Text 2.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was financially supported by the National Natural Science Foundation of China (No. No.51878170), and the Guangdong Basic and Applied Basic Research Foundation (No. 2023A1515140067).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eY.L. and L.Y. performed the experiments, analysed the data and drafted the manuscript. C.T. contributed to the instrumental analysis. Y.Y. and A.W. contributed to data interpretation. C.T., S.L., J.X. and Q.H. contributed to the revision of the manuscript. H.L. designed and supervised the research, provided resources, and revised the manuscript. All authors participated in the manuscript reviewing and editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupporting Information.\u0026nbsp;\u003c/strong\u003eSupplementary material for this article is available at http://pending.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrespondence\u0026nbsp;\u003c/strong\u003eand requests for materials should be addressed to Hui Lin.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eUSEPA, Final PFAS National Primary Drinking Water Regulation. https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas (2024).\u003c/li\u003e\n\u003cli\u003eHe A\u003cem\u003e, et al.\u003c/em\u003e Vital Environmental Sources for Multitudinous Fluorinated Chemicals: New Evidence from Industrial Byproducts in Multienvironmental Matrices in a Fluorochemical Manufactory. \u003cem\u003eEnvironmental Science \u0026amp; Technology\u003c/em\u003e \u003cstrong\u003e56\u003c/strong\u003e, 16789-16800 (2022).\u003c/li\u003e\n\u003cli\u003eBrusseau ML, Anderson RH, Guo B. 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Here, we achieve the efficient and broad-spectrum capture of 107 PFASs from fluorochemical effluents using a treatment-train strategy that combines Zn-based electrocoagulation (EC) with anion-exchange resin (AER) beds. The “zero-carbon” adsorbent, zinc hydroxide flocs, generated in-situ by Zn-based EC bulk removes PFAS with log\u003cem\u003eK\u003c/em\u003e\u003csub\u003eow\u003c/sub\u003e\u0026gt;4 through a semi-micellar adsorption mechanism similar to mineral flotation, resulting in the highest adsorption capacities among all reported adsorbents. Technical-economic analysis and life-cycle environmental impact showed that coupling Zn-based EC reduces the cost by an order-of-magnitude and the carbon-footprint by 70% compared to AER beds alone. It was also observed that iodinated PFAS, in which the fluorine atom is replaced by an iodine atom, had significantly improved adsorption selectivity, which may shed light on designing environmentally-friendly fluorochemicals.\u003c/p\u003e","manuscriptTitle":"Treatment-train strategy realizes broad-spectrum capture of hundreds of per- and polyfluoroalkyl substances from fluorochemical wastewater","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-20 13:59:14","doi":"10.21203/rs.3.rs-4382526/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"9ecc34d3-4b32-4092-a65e-e642e91c2c60","owner":[],"postedDate":"May 20th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":32041692,"name":"Earth and environmental sciences/Environmental sciences/Environmental chemistry/Environmental monitoring"},{"id":32041693,"name":"Physical sciences/Engineering/Civil engineering"}],"tags":[],"updatedAt":"2025-02-26T08:05:11+00:00","versionOfRecord":{"articleIdentity":"rs-4382526","link":"https://doi.org/10.1038/s41467-025-57272-0","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2025-02-25 05:00:00","publishedOnDateReadable":"February 25th, 2025"},"versionCreatedAt":"2024-05-20 13:59:14","video":"","vorDoi":"10.1038/s41467-025-57272-0","vorDoiUrl":"https://doi.org/10.1038/s41467-025-57272-0","workflowStages":[]},"version":"v1","identity":"rs-4382526","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4382526","identity":"rs-4382526","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}