60Coγ activation of Cladophora rupestris biomass functional groups and its effect on Pb2+ adsorption

60Coγ activation of Cladophora rupestris biomass functional groups and its effect on Pb2+ adsorption | 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 Research Article 60 Coγ activation of Cladophora rupestris biomass functional groups and its effect on Pb 2+ adsorption Lu-sheng Zhang, Zhao-wen Liu, Chang-fa Qiu, Xiao-yu Feng, Shi-ying Ma, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5103068/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Dec, 2024 Read the published version in Environmental Science and Pollution Research → Version 1 posted 5 You are reading this latest preprint version Abstract To investigate the modification of Pb 2+ adsorption of the functional groups of Cladophora rupestris ( C. rupestris ) biomass by gamma radiation ( 60 Coγ-ray), the interface structure, chemical properties, adsorption behaviors, and Pb 2+ adsorption mechanisms of C. rupestris biomass were investigated after irradiation with varying doses of 60 Coγ-ray. The results indicate that 60 Coγ-ray significantly changed the surface characteristics and interfacial chemistry of the C. rupestris biomass .This led to fracturing and fragmentation that produced a larger specific surface area and more abundant pore structure, increasing the electronegativity in the C. rupestris biomass. The theoretical Pb 2+ adsorption capacity increased significantly (2.6–2.9 times) after 60 Coγ-ray irradiation. 60 Coγ-ray caused preferential degradation of protein components in the dissolved organic matter of the C. rupestris biomass, and protein deamination increased the absorption sites of cations. In the C. rupestris biomass, 60 Coγ-ray altered the elemental composition and functional groups, particularly the carbon- and oxygen-containing functional groups, to improve Pb 2+ adsorption. In conclusion, 60 Coγ-ray can activate the functional groups of C. rupestris biomass and improve their Pb 2+ adsorption sites. This study provides new insight into modification of biomass materials for enhanced removal of heavy metals from waterbodies. 60Coγ-ray C. rupestris Pb2+ Adsorption Functional groups Remediation potential Figures Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction Heavy metals (HMs) have attracted widespread attention (Godoy et al. 2019 ) because of their toxicity and increased presence in waterbodies. Pb 2+ , known for its bioaccumulation and non–degradability, is one of the most toxic HMs (Huang et al. 2023 ; Yang et al. 2014 ; Yuan et al. 2021 ), and the amount of Pb 2+ discharged into water systems in China increases every year (Wang et al. 2019 ). Pb 2+ contamination is a serious threat to human health and the environment (Yang et al. 2014 ). Pb 2+ can be removed from water systems via ion exchange, membrane filtration, chemical precipitation, and adsorption (Cao et al. 2019 ; Ge et al. 2022 ; Miao and Li 2021 ; Zhang et al. 2019 ). The adsorption method has attracted widespread attention owing to its low cost, high efficiency, simple operation, and short treatment cycle (Miao and Li 2021 ; Zhang et al. 2019 ). Cao et al. ( 2015 ) and Zhang et al. ( 2019 ) reported that Cladophora rupestris (C. rupestris ), which is widely distributed in natural waterbodies (Sucaldito and Camacho 2017 ; Zulkifly et al. 2012 ), presented favorable adsorption for Pb 2+ and Cd 2+ . Therefore, C. rupestris is valuable as a biosorbent for the removal of Pb 2+ from waterbodies. The theoretical Pb 2+ adsorption capacity (Qm) of the organic frameworks of C. rupestris has been found to be 15.02 mg/g (Zhang et al. 2024 ). Biochar has been widely used to remediate HM contamination (Wang et al. 2015 ). Moreover, modification of biomass materials, such as silicate-modified oil tea camellia shell-derived biochar for Cd 2+ removal, can often improve their HM absorption capacity (Cai et al. 2021 ). Wang et al. ( 2019 ) reported that the Pb 2+ Qm of fresh biochar at 350 and 650°C was 279.85 and 286.07 mg·g − 1 , respectively. Zhang et al. ( 2017 ) demonstrated that humic- and protein-like substances were involved in Pb 2+ adsorption, and Wang et al. ( 2022 ) demonstrated that biochar can enhance Pb 2+ adsorption through the cosorption of dissolved organic matter (DOM). Simultaneously, ultraviolet (UV) irradiation can promote the generation of new oxidation functional groups (Wang et al. 2023 ). Ethylenediamine-modified pectins have exhibited a remarkable removal efficiency for Pb 2+ (Liang et al. 2020 ). Gamma radiation (γ-ray) is considered an effective physical method for modifying biomass materials by engaging in cross-linking, grafting, copolymerization, and disintegration processes (Choi and Kim 2013 ). Mohamed et al. ( 2022 ) showed that 60 Coγ-ray could improve the surface characteristics of clay minerals, enhancing the efficient removal of Gd 3+ and Ce 3+ , with the primary mechanism being radical chemistry (Han et al. 2022 ). Zhao et al. ( 2022 ) found that polyisoprene underwent molecular transformations upon exposure to γ-ray, generating carbonyl (C = O) and hydroxyl (O − H) groups, and polyisoprene irradiated with 100 kGy of 60 Coγ-ray caused the fracture of the carbon main chain and oxidation of the side-chain functional groups. Li et al. ( 2022 ) found that higher 60 Coγ-ray doses can degrade the dietary fiber of a navel orange, rupturing the crystalline part of the fiber and breaking the covalent bonds. According to Gewert et al. ( 2018 ) and Wen et al. ( 2022 ), 60 Coγ-ray can break the main chain of polymers, and the chemical bonds of DOM can be broken and recombined, thus changing the structural characteristics of the DOM of C. rupestris . In this study, to investigate the interface structure, chemical properties, and functional group activation of C. rupestris biomass irradiated by 60 Coγ-ray, C. rupestris biomass samples were treated with different 60 Coγ-ray doses (0, 20, 100, and 200 kGy). Pb 2+ adsorption characteristics were investigated to reveal the Pb 2+ adsorption mechanism of C. rupestris biomass irradiated by 60 Coγ-ray. This study provides new insight into modification of biomass materials for enhanced removal of HMs from waterbodies. 2. Materials and methods 2.1. Materials and reagents C. rupestris biomass samples were collected from Heichiba in Hefei city, Anhui, China. The C. rupestris samples were washed with running water, dried in an oven at 60 ℃ for 24 h to constant weight, and then crushed through a 100-mesh sieve. The lead nitrate (Pb(NO 3 ) 2 ) was analytical purity grade and obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). All reagents were analytical purity grade, and solutions were prepared with ultrapure water (18.25 MΩ•cm). 2.2. 60 Coγ-ray irradiation The C. rupestris biomass samples were irradiated with 60 Coγ-ray doses of 0, 20, 100, and 200 kGy (Furui High Energy Technology Co., Ltd, Guangzhou, China). The samples were stored in sealed brown glass bottles. 2.3. Materials characterization Surface morphology changes were observed by scanning electron microscopy (SEM; s–4800, Hitachi, Japan). The particle size distribution and specific surface area were measured by a laser particle size distributor (BT–9300H, Bettersize, China). Surface hydrophilicity was measured by a contact angle analyzer (DSA100, KRUSS, Hamburg, Germany). Surface electronegativity was measured by a zeta potential analyzer (Zetasizer Nano ZS90, Malvern, UK). Crystalline phase and crystallinity were analyzed by X-ray diffraction (XRD; D8 ADVANCE, Bruker, Germany). Functional groups were characterized by Fourier transform infrared spectroscopy (FTIR; Nicolette 50, Thermo Scientific, USA). The chemical composition of the DOM was analyzed by a three-dimensional fluorescence spectrophotometer (3D–EEM; f–4500, Horiba, Japan) and UV-visible spectrophotometer (UV-Vis; UV–1452, Shimazu, Japan). The active centers and chemical states before and after Pb 2+ adsorption were characterized by X-ray photoelectron spectroscopy (XPS; Escalab 250, Thermo–VG Scientific, USA). The specific experimental steps are presented in Supplementary Information S1. 2.4. Batch adsorption experiments Adsorption isotherm experiments were performed at the initial Pb 2+ concentrations of 0, 25, 50, 100, 150, 200, 300, and 400 mg/L with a 4 g/L solid-to-liquid ratio in a 180 rpm thermostatic oscillator at 25 ℃ for 24 h. The mixtures were filtered with a 0.45 µm syringe filter, and the concentrations of Pb 2+ in the supernatant were analyzed by a flame atomic absorption spectrophotometer (ZEEnit 700P, Analytic Jena, Germany). The experiments were performed three times. 2.5. Environmental factors 2.5.1 pH The C. rupestris biomass of 0.100 g treated with different 60 Coγ-ray irradiation doses were added to 25 mL of Pb 2+ solution at a concentration of 400 mg/L, and the pH of the mixtures was adjusted by 0.1 M HNO 3 and 0.1 M NaOH to 2, 3, 4, 5, and 6 using a similar experimental step with adsorption isotherms. 2.5.2 Metal ion competition The C. rupestris biomass of 0.100 g treated with different 60 Coγ-ray irradiation doses were added to 25 mL of a solution containing 50 mg/L solution of Pb 2+ , Cd 2+ , Cu 2+ , Zn 2+ , and Ni 2+ to analyze the Qm of the C. rupestris biomass to different HM ions. 2.6 Release of net alkali metal cations and reusability The K + , Na + , Ca 2+ , and Mg 2+ concentrations were determined in pure water and in a 400 mg/L Pb 2+ solution, and the water-soluble K + , Na + , Ca 2+ , and Mg 2+ contents were calculated per unit of the biomass (Shen et al. 2017 ). After the equilibrium of adsorption, the sample was repeatedly centrifuged and filtered with ultrapure water for 3 times, and then 0.1 M dilute hydrochloric acid was added for resolution for 24 h, and the cycle was repeated for 4 times. 2.7. Data analysis The adsorption isotherms were fitted using the Langmuir and Freundlich models (details in Supplementary Information S2). The experimental data were analyzed and graphed using SPSS 22.0 and Origin2018, and the Duncan method was used for the significant difference comparison (p < 0.05). 3. Results and discussion 3.1. Characteristics of C. rupestris biomass irradiated by 60 Coγ-rays 3.1.1. Morphology, particle size, and crystallinity The surface morphology of the C. rupestris biomass treated with different 60 Coγ-ray irradiation doses is shown in Fig. 1 . The C. rupestris biomass samples were rough and full of grooves, with particles attached. However, cracks were gradually generated on the surface of the C. rupestris biomass samples treated with 60 Coγ-ray irradiation and pores tended to develop on the interior surface of the samples. Notably, with increasing 60 Coγ-ray irradiation doses, the surface morphology of the C. rupestris biomass samples changed more drastically, showing voids, increased tiny pores on the smooth surface, and an irregular structure. Overall, 60 Coγ-ray increased the specific surface area of the C. rupestris biomass samples, and more developed pore structures were observed at higher 60 Coγ-ray irradiation doses. The particle size distribution of the C. rupestris biomass treated with 60 Coγ-ray is shown in Fig. 2 a. As the 60 Coγ-ray irradiation dose increased from 0 to 200 kGy, the median diameter (D50) of the particle decreased from 52.26 to 39.73 µm, respectively. The drop ratio was 23.98% when the 60 Coγ-ray irradiation dose was 200 kGy. The specific surface area of the C. rupestris biomass samples treated with 60 Coγ-ray increased 14.6% from 159.1 to 182.3 m 2 /kg at radiation doses of 0 to 200 kGy, respectively, indicating that 60 Coγ-ray can cause fracture and breakage, creating a larger surface area that can be conducive to activate relevant functional groups (Zhu et al. 2019 ). These findings are similar to those of Mohamed et al. ( 2022 ). The XRD spectra are shown in Fig. 2 b. The peak intensity at 2θ values of 29.76°, 39.76°, 47.78°, and 48.89°, which is known as CaCO 3 (Miao and Li 2021 ), was significantly increased, particularly the 2θ value of 29.76°. This increase was more evident as the irradiation dose increased, indicating that the crystallinity and brittleness of the C. rupestris biomass increased with increasing 60 Coγ-ray irradiation doses (Xue et al. 2023 ), and the C. rupestris biomass were easier to break and fracture (Shen et al. 2023 ). The XRD spectra show that 60 Coγ-ray led to the C. rupestris biomass having an amorphous structure and their experiencing the breakage of the main polymer chain, which contributed to its crystallinity (Shen et al. 2023 ). This result is consistent with the particle size analysis result. Therefore, 60 Coγ-ray can cause the fracture and fragmentation of C. rupestris , resulting in a reduction in particle size and an increase in specific surface area, which can increase its HM-ion adsorption potential. 3.1.2. Zeta potentials and functional groups Figure 2 c displays the zeta potentials of the C. rupestris biomass with pH values in the range of 2–9. With increasing 60 Coγ-ray irradiation doses, the electronegativity of the C. rupestris biomass s increased, indicating that 60 Coγ-ray causes C. rupestris biomass to attract electrons and become negatively charged (Liang et al. 2020 ). In summary, 60 Coγ-ray significantly increased the electronegativity of C. rupestris biomass. The increased electronegativity might increase the adsorption of cations owing to the reduced electrostatic repulsion between the adsorbent and cations. The FTIR results of the C. rupestris biomass samples treated with 60 Coγ-ray are shown in Fig. 2 d. The deformation vibration of the aromatic CH 2 peak at 1428.53 cm − 1 (Godoy et al. 2019 ) and bending vibration of the aromatic C − H peaks at 876.02 and 712.73 cm − 1 (Tan et al. 2020 ; Yang et al. 2014 ) significantly decreased as the 60 Coγ-ray irradiation dose increased, indicating that 60 Coγ-ray induced the benzene-ring breakage of C. rupestris biomass (Li et al. 2022 ). The peaks at 2924.76 and 2858.10 cm − 1 (Guan et al. 2020 ), corresponding to the symmetric and symmetric stretching vibrations of aliphatic C − H, respectively, decreased (Zhu et al. 2019 ), implying the cleavage of the C − H and C − C bonds from the main polymer chain. The stretching vibration of O − H at 3374.38 cm − 1 (Zhang et al. 2017 ) was enhanced and blue shifted, indicating the impact of different irradiation treatments on the structure of hydrogen and the hydroxyl group in cellulose and hemicelluloses (Li et al. 2022 ). The intensity of the C = O characteristic peak at 1647.89 cm − 1 (Liu et al. 2019 ), the position and peak shape of the asymmetric stretching vibration and symmetric stretching vibration of C − O−C at 1161.41 and 1110.30 cm − 1 (Chen et al. 2015 ), and the stretching vibration of C − O−H at 1034.61 cm − 1 all shifted accordingly after 60 Coγ - ray irradiation. These results demonstrate that oxidation reactions occurred with 60 Coγ-ray irradiation that caused a series of complex chain expansions, branching, and chain termination, and eventually led to the formation of C = O, C − O−C, and C − O−H (Zhu et al. 2019 ). The peaks at 1579.18 cm − 1 for C − N and N − H showed marked shoulder peaks after 60 Coγ-ray irradiation, indicating that more amide functional groups were generated (Guan et al. 2020 ). This result is consistent with that of Wang et al. ( 2023 ), who found that C = O and O − H can be formed by UV irradiation. The results are also consistent with those of Zhu et al. ( 2022 ) who found that high-dose irradiation of 60 Coγ-ray can significantly destroy the structure of lignocellulose. In conclusion, 60 Coγ-ray can alter the elemental composition and functional groups of C. rupestris biomass, especially in carbon- and oxygen-containing functional groups (CFGs and OFGs). 3.1.3. Hydrophilicity The water contact angle is used to characterize the hydrophobicity of a material, and the larger the contact angle, the more hydrophobic the material (Hu et al. 2023 ). The hydrophilicity was enhanced, and the adsorption amounts of Pb 2+ and Cu 2+ increased after microplastic aging (Wang et al. 2023 ). Figure 3 a shows that the water contact angle of the C. rupestris biomass decreased from 99.7° to 87.2° a 60 Coγ-ray irradiation doses increased from 0 to 200 kGy, respectively, indicating that the hydrophilicity of C. rupestris biomass increased. 60 Coγ-ray irradiation can produce hydrophilic groups, which enhances the Pb 2+ adsorption efficiency (Wang et al. 2023 ; Liu et al. 2019 ). 3.1.4. DOM DOM can adsorb, complex, and redox HMs (Mu et al. 2022 ). Huang et al. ( 2020 ) reported that DOM and Pb 2+ can form soluble complexes to inhibit the adsorption and precipitation of HMs. After treating the C. rupestris biomass with 60 Coγ-ray, the 3D-EEM fluorescence spectra of the DOM released from the C. rupestris biomass changed (Fig. 3 b). The intensity of peak A at Ex/Em = 276–279/347–353 nm, assigned to tryptophan-like substances (Li et al. 2020 ; Liu et al. 2022 ; Teng et al. 2019 ), decreased significantly as the 60 Coγ-ray irradiation dose increased and disappeared when the 60 Coγ-ray irradiation dose reached 200 kGy. Meanwhile, peak B at Ex/Em = 336–342/422–428 nm, assigned to humic acid (HA)-like substances (Li et al. 2020 ; Liu et al. 2022 ; Teng et al. 2019 ), exhibited a significant red shift with 60 Coγ-ray treatment, and the fluorescence intensity of the humic component increased in the DOM, especially when the irradiation dose reached 200 kGy. Therefore, 60 Coγ-ray can cause degradation of protein components and cause the amino group of the protein to fall off, thus increasing the humification process of DOM (Zhang et al. 2020 ). Photoaging may promote the release of soluble organics (Hu et al. 2023 ), causing amino groups of the protein to fall off and the absorption sites of cations to increase, which might increase the Pb 2+ adsorption efficiency (Chen et al. 2020 ). Shi et al. ( 2020 ) demonstrated that Pb 2+ was directly adsorbed by green algae until equilibrium in the presence of HA, and Pb 2+ bound to the algae in the form of a Pb–FA conjugated copolymer (Shi et al. 2020 ). Pb 2+ can form ternary complexes with biodegradable microplastics and their leached HA, providing new adsorption sites for unbound Pb 2+ , thus enhancing the Qm for Pb 2+ (Li et al. 2022 ). In conclusion, 60 Coγ-ray caused preferential degradation of protein components in the DOM of the C. rupestris biomass (Cao et al. 2019 ; Yang et al. 2014 ), and protein deamination increased the absorption sites of the cations. As shown in Fig. S1a, the absorption wavelength of the DOM released from the C. rupestris biomass samples shifted toward the higher wavelength with an increase in the 60 Coγ-ray irradiation, suggesting that 60 Coγ-ray caused the oxidation of the DOM (Gao et al. 2021 ). The absorption peaks of the UV-Vis spectra at 250–290 nm represent heterocyclic aromatic hydrocarbons, and 390 nm represents the carbonyl or conjugated groups (Teng et al. 2021 ). Fig. S1a shows that the UV-Vis spectra at 281 nm were blue shifted to 269 nm, suggesting that 60 Coγ-ray caused the heterocyclic aromatic hydrocarbons to change in the DOM and indicating that the π–π* electron transition of algae-derived DOM decreased with increasing irradiation doses (Janot et al. 2010 ). The spectra at 400 nm were blue shifted to 390 nm, indicating that carbonyl or conjugated groups were produced by 60 Coγ-ray irradiation and 60 Coγ-ray had some effect on the polyene structure containing seven conjugated double bonds in the visible region of the algae-derived DOM (Klempová et al. 2023 ; Zhou et al. 2020 ). In conclusion, 60 Coγ-ray causes successive decomposition and transformation of DOM, altering the molecular configuration of DOM (Dryer et al. 2008 ). 3.2. Adsorption of Pb 2+ onto C. rupestris biomass 3.2.1. Qm The Langmuir and Freundlich isotherms of Pb 2+ on the C. rupestris biomass treated with different doses of 60 Coγ-ray irradiation are shown in Fig. 4 . The theoretical Pb 2+ Qm of the C. rupestris biomass increased significantly to 74.907, 79.800, and 82.550 mg/g after 60 Coγ-ray irradiation doses of 20, 100, and 200 kGy, respectively, with an increase of 2.6–2.9 times. After 60 Coγ-ray irradiation, the Pb 2+ adsorption of the C. rupestris biomass showed a linear growth trend at equilibrium concentrations (Ces) in the range of 0–40 mg/L and then became saturated when Ce ≥ 40 mg/L. This may be attributed to 60 Coγ-ray, which increases the adsorption sites and functional groups and reduces the spatial site resistance, thus significantly increasing the equilibrium Qm (Spessato et al. 2019 ). The fitting parameters of the Langmuir and Freundlich models are listed in Table 1 . The adsorption isotherms were well fit by the Langmuir and Freundlich models (R 2 ≥ 0.92) when the 60 Coγ-ray irradiation dose was lower than 100 kGy; subsequently, the R 2 dropped significantly, particularly in the Freundlich model (R 2 = 0.70) at 200 kGy, which indicates that the Freundlich model was unable to describe the adsorption characteristics in the analyzed cases. The K L values of the Langmuir model decreased as the 60 Coγ-ray irradiation dose increased, indicating that the adsorption process was not a single surface chemisorption but was also affected by other forces (Li et al. 2020 ; Martins et al. 2015 ). Liu et al. ( 2019 ) found that the surface of UV-aged microplastics is rougher and has some cracks. The high energy of 60 Coγ-ray can allow oxidation to occur in the deeper layers, which leads to enhanced chemisorption (Huang et al. 2020 ; Teng et al. 2019 ; Zhang et al. 2020 ). The Freundlich constant K f —free energy of adsorption—indicates the lative biosorption capacity of the biosorbent bonding energy. In this study, K f was 1.48–10.72, which reflects the high affinity of Pb 2+ to the binding sites of the C. rupestris biomass (Pillai et al. 2013 ), especially at the 60 Coγ-ray irradiation dose of 200 kGy. The slope 1/n in the Freundlich model was less than 1, indicating that 60 Coγ-ray irradiation increased the surface heterogeneity of the C. rupestris biomass(Xie et al. 2015 ). Table 1 Adsorption isotherm parameters of the Langmuir and Freundlich models Irradiation treatment Model parameters Langmuir Freundlich K L /L•mg − 1 Qm/mg•g − 1 R 2 K f mg 1 − 1/n •g − 1 •L 1/n 1/n R 2 0 kGy 0.808 30.383 0.924 9.43 0.272 0.981 20 kGy 0.137 74.907 0.965 7.85 0.494 0.943 100 kGy 0.125 79.800 1.000 7.48 0.494 0.999 200 kGy 0.167 82.550 0.842 10.72 0.439 0.696 In conclusion, 60 Coγ-ray irradiation decreases the free energy of adsorption, increasing the biosorption capacity and affinity of Pb 2+ to the binding sites of C. rupestris biomass. 3.2.2. Influence of pH The influence of pH on the Pb 2+ adsorption capability of the C. rupestris biomass is shown in Fig. 5 a. The Pb 2+ adsorption capability of the C. rupestris biomass increased as the pH increased, and the Pb 2+ Qm increased to 19.04 mg/g when the pH was 6. This trend can be attributed to the increased dissolution of insoluble crystalline minerals in low pH environments, which releases a large number of cations (H + , K + , Na + , Ca 2+ , and Mg 2+ ) that can compete with Pb 2+ for adsorption sites, leading to a decrease in Pb 2+ adsorption (Wang et al. 2022 ). As the solution pH increased, deprotonation of the functional groups led to the formation of negative charges, facilitating cation adsorption through electrostatic interactions (Liang et al. 2020 ). After 60 Coγ-ray irradiation, the pH had no significant effect on the Pb 2+ adsorption. The above phenomena indicate that C. rupestris biomass has better environmental adaptability to Pb 2+ after 60 Coγ-ray irradiation (Yang et al. 2014 )—consistent with the results of the zeta potential analysis. 3.2.3. Competitive adsorption of other HM ions The competitive adsorption of the C. rupestris biomass is shown in Fig. 5 b. There was a significant difference for the different HMs, and the order of Qm was Pb 2+ > Cd 2+ > Ni 2+ ≈ Zn 2+ > Cu 2+ , implying preferential adsorption of Pb 2+ . These results are similar to those of Cao et al. ( 2015 ), in which C. rupestris was found to be able to accumulate Pb 2+ . Zhang et al. ( 2019 ) suggested that C. rupestris has a bioremediation potential for Cd 2+ . After the irradiation of 60 Coγ-ray at doses of 0 to 200 kGy, the Pb 2+ Qm increased from 10.73–24.00%, respectively. The adsorption capacities of Zn 2+ , Cd 2+ , and Ni 2+ also improved significantly after 60 Coγ-ray irradiation, but the Cu 2+ Qm did not significantly increase. These findings suggest that 60 Coγ-ray irradiation can activate the relevant adsorption sites and functional groups, and, among all the HMs tested, C. rupestris biomass demonstrated the highest affinity for Pb 2+ . These findings are similar to those of Zhao et al. ( 2023 ). 3.2.4. The reusability and desorption As shown in Fig. 6 , after four desorption and regeneration cycles, the adsorption capacity of Pb 2+ on C. rupestris biomass samples after 60 Coγ-ray irradiation only decreased by 28.25%, 17.51%, 18.97% and 15.36%. This phenomenon suggests that the adsorption capacity of the biomass is still high after several desorption and regeneration cycles (Chen et al. 2021 ) 3.3. Effect of groups activation by 60 Coγ-ray and adsorption of Pb 2+ As shown in Fig. 7 , 10.1 wt % Pb was detected on the C. rupestris biomass samples and Pb was mainly adsorbed on the surface and pores by combining with C and O. As shown in Fig. S2 and Table S1, C. rupestris biomass contains a large amount of O (50.37%), C (28.12%), and Ca (19.22%), as well as a small amount of N (2.30%). The functional groups and amorphous parts have been reported to be composed of these elements can act as initiators for photodegradation (Zhu et al. 2019 ). The O content and O/C ratio increased with increased 60 Coγ-ray irradiation doses, indicating that 60 Coγ-ray can cause C. rupestris biomass to produce more OFGs (Hu et al. 2023 ). The Pb 4f characteristic peak appeared in the irradiated C. rupestris biomass, indicating that Pb 2+ was successfully adsorbed onto the C. rupestris biomass. The C 1s peak of the C. rupestris biomass can be deconvoluted into four individual peaks corresponding to C−(C, H)/C = C (284.80 eV), C − O (286.20–286.73 eV), C = O (287.81–288.03 eV), and O − C = O (288.60–289.55 eV) (Zafar et al. 2022 ) (Fig. 8 ). After the irradiation of 60 Coγ-ray at doses of 0 to 200 kGy, the peak intensity of C−(C, H)/C = C of the C. rupestris biomass decreased from 15.14–11.25%, and the peak intensity of C − O increased from 15.6 to 11.34%, respectively. This result indicates that 60 Coγ-ray irradiation caused the C−(C, H) bonds to fracture and the benzene ring to open. These broken bonds are highly reactive and rapidly react with O 2 to form C − O bonds (Wang et al. 2023 ), which subsequently form C = O bonds, leading to the generation of unsaturated bonds represented by alcohols, aldehydes, and acids (Zhu et al. 2020 ). The C−(C, H)/C = C content in the C. rupestris biomass irradiated with 0 kGy of 60 Coγ-ray and loaded with Pb 2+ showed the most pronounced shift of 2.61%, indicating that the aromatic structure of the C. rupestris biomass participated in the Pb–π interaction adsorption process (Liu et al. 2023 ). After being treated with 60 Coγ-ray, the consumption of C − O was between 10.23% and 11.13%, indicating that the functional groups with C as the backbone underwent significant changes. Oxygen atoms often act as electron donors to form stable covalent bonds with HMs and play a crucial role in chelation (Wu et al. 2019 ). The primary OFGs in the C. rupestris biomass were C = O and C − O (Fig. S3). After 60 Coγ-ray irradiation, the content of the C = O bonds decreased while that of the C − O bonds increased, and the ratio of C = O/C − O decreased from 1.56 to 1 for 60 Coγ-ray doses of 0 to 200 kGy, respectively. The O − C = O functional group was observed when the 60 Coγ-ray dose was 200 kGy, indicating that the OFGs of C. rupestris biomass were enhanced after 60 Coγ-ray irradiation (Wu et al. 2021 ). The binding energy of the OFGs declined in the Pb-loaded C. rupestris biomass, suggesting that the chelation by the OFGs is crucial during Pb 2+ adsorption. After 60 Coγ-ray irradiation, the content of the C − O bonds in the C. rupestris biomass loaded with Pb 2+ decreased from 12.97–9.36% for 60 Coγ-ray doses of 0 to 200 kGy, respectively. Particularly, the O − C = O content of the C. rupestris biomass sample treated with 200 kGy of 60 Coγ-ray irradiation decreased to 5.77%, indicating that O − C = O plays an important role in Pb 2+ adsorption (Chen et al. 2021 ). In summary, 60 Coγ-ray irradiation activates the OFGs of C. rupestris biomass, enhancing the ability of the OFGs in C. rupestris biomass to bind with Pb 2+ . As shown in Fig. 9 , the Pb 4f7/2 and Pb 4f5/2 spectra of the C. rupestris biomass samples after 60 Coγ-ray irradiation can be deconvoluted into a pair of peaks corresponding to Pb 2+ and Pb − O (Wu et al. 2019 ). Therefore, the main combined forms of Pb were Pb 2+ and Pb − O. This phenomenon suggests that not only electrostatic interactions but also bonding interactions existed between Pb and C. rupestris biomass (Wu et al. 2019 ). The Pb 2+ /Pb − O ratio changed from 1.53 to 0.85 after the irradiation of 60 Coγ-ray at doses of 0 to 200 kGy, respectively, indicating that 60 Coγ-ray irradiation promoted the bonding interaction between the C. rupestris biomass and Pb to form Pb − O. However, the XRD results show that no Pb precipitation was generated after the adsorption of Pb 2+ (Fig. 10 ), indicating that precipitation was not an adsorption mechanism of Pb 2+ . 3.4 Release of metal ions and DOM from C. rupestris biomass by 60 Coγ-ray The release of small amounts of K + , Na + , Mg 2+ , and large amounts of Ca 2+ from the solution before and after the adsorption of Pb 2+ by the C. rupestris biomass samples is shown in Table S2, suggesting that 60 Coγ-ray was more favorable for Ca 2+ release from the cell wall of the C. rupestris biomass samples (Fan et al. 2021 ), resulting in enhanced ion exchange between Pb 2+ and Ca 2+ (Gao et al. 2019 ). After Pb 2+ adsorption, the 3D-EEM fluorescence spectra of the DOM released from the C. rupestris biomass decreased drastically, indicating that 60 Coγ-ray caused π-electron mobility on the aromatic carbon “core” and enhanced the conjugated unsaturated structure (Fig. S4) (Qu et al. 2016 ). In Fig. S1b, the disappearance of the two shoulder peaks suggests the binding of Pb 2+ and the DOM. In the wavelength range > 390 nm, the absorption spectra of DOM showed almost no change, suggesting that intermolecular reaction and the molecular structure did not play a significant role in the binding of Pb 2+ and the DOM due to 60 Coγ-ray (Yan et al. 2013 ). Therefore, the binding of Pb 2+ and the DOM was mainly due to the interaction of the carboxylate chromophores with 60 Coγ-ray (Teng et al. 2021 ). 60 Coγ-ray caused the successive decomposition and transformation of the DOM of the C. rupestris biomass, and the carboxy chromophore played an important role in the reaction with Pb 2+ . In conclusion, 60 Coγ-ray irradiation causes C. rupestri s biomass to be dearomatized, which exposes more unsaturated carbon - binding sites for Pb 2+ adsorption, while C. rupestris biomass treated with a high 60 Coγ-ray irradiation dose contain more OFGs and ion - exchange sites, which provide more active adsorption sites for Pb 2+ (Li et al. 2018 ). 4. Conclusions (1) 60 Coγ-ray significantly changed the surface characteristics and interfacial chemistry of the C. rupestris biomass, causing fracturing and fragmentation, producing a larger specific surface area and more abundant pore structure, and increasing the electronegativity. (2) The theoretical Pb 2+ Qm of the C. rupestris biomass increased significantly (2.6–2.9 times) after 60 Coγ-ray irradiation. 60 Coγ-ray irradiation can activate the relevant adsorption sites and increase the Pb 2+ affinity of C. rupestris biomass. (3) 60 Coγ-ray caused preferential degradation of protein components in the DOM of the C. rupestris biomass, and protein deamination increased the absorption sites of cations. (4) 60 Coγ-ray altered the elemental composition and functional groups of the C. rupestris biomass, especially the carbon-containing functional groups and OFGs. 60 Coγ-ray irradiation activated the OFGs of the C. rupestris biomass, promoting the adsorption of Pb 2+ . (5) 60 Coγ-ray irradiation produced a high degree of dearomatization, which exposed more unsaturated carbon-binding adsorption sites for Pb 2+ . The C. rupestris biomass treated with a high 60 Coγ-ray irradiation dose of 200 kGy contained more OFGs and ion-exchange sites, which provided more active Pb 2+ adsorption sites. These findings indicate that irradiation of 60 Coγ-ray is an efficient technique for improving the Pb 2+ adsorption of C. rupestris biomass, aiding in enhanced removal of HMs from waterbodies. Declarations Ethical Approval Not applicable. Consent to Participate We consent to participate this manuscript. Consent to Publish We consent to publish this manuscript. Authors Contributions Lu-sheng Zhang: Methodology, Writing - original draft, Investigation. Zhao-wen Liu and Chang-fa Qiu: Software, Formal analysis. Xiao-yu Feng: Conceptualization, Software. Shi-ying Ma and Qian Yin: Visualization, Conceptualization. De-ju Cao: Resources, Writing - review & editing, Supervision, Data curation. Funding This work was supported by the Natural Science Foundation of China (41877418) and the financial aid of Nature Fund of Anhui Province of China (1808085MD100). Competing Interests The authors declare that they have no conflict of interest. Availability of data and materials We declared that the data and materials presented in this paper are reliable. 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University","correspondingAuthor":false,"prefix":"","firstName":"Shi-ying","middleName":"","lastName":"Ma","suffix":""},{"id":383807922,"identity":"84522c46-dec9-44c3-b8f7-6c0e1b431fd4","order_by":5,"name":"Qian Yin","email":"","orcid":"","institution":"Anhui Agriculture University: Anhui Agricultural University","correspondingAuthor":false,"prefix":"","firstName":"Qian","middleName":"","lastName":"Yin","suffix":""},{"id":383807923,"identity":"9126ea43-9d2f-4286-af3e-d8ad2b5f722f","order_by":6,"name":"deju Cao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAsUlEQVRIiWNgGAWjYFCChMQHjA1glgHRWpINSNbCJkGaFv72hGcVP3fYJTawN2+TYKi5Q1iLxJkHaTd7zyQnNvAcK5NgOPaMsBYDiYS0G7xtzIkNEjlmQBceJk5L4d+2+sQG+TckaGHmbTsMtIWHSC1AvyRLy7YdN27jSSu2SDhGhBb+9pzEj2/bqmX72Q9vvPGhhggtDAw8CWCKDUQkEKOBgYH9AHHqRsEoGAWjYOQCAMZyOYrVEvIHAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-0911-0006","institution":"Anhui Agricultural University","correspondingAuthor":true,"prefix":"","firstName":"deju","middleName":"","lastName":"Cao","suffix":""}],"badges":[],"createdAt":"2024-09-17 12:03:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5103068/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5103068/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11356-024-35802-5","type":"published","date":"2024-12-26T15:57:35+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":70559729,"identity":"c29d3f0f-4915-4736-aab9-f742ef8ee361","added_by":"auto","created_at":"2024-12-04 11:49:46","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":216616,"visible":true,"origin":"","legend":"\u003cp\u003e(a)\u003cstrong\u003e \u003c/strong\u003eParticle size distribution, (b) XRD, (c) zeta potential, and (d) FTIR of \u003cem\u003eC. rupestris\u003c/em\u003e biomass treated with different \u003csup\u003e60\u003c/sup\u003eCoγ–ray irradiation doses\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/a86bf4d462d9d78d941807ee.png"},{"id":70561627,"identity":"6b9ed047-2e87-486d-84ac-e2d26266b8df","added_by":"auto","created_at":"2024-12-04 12:05:46","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":197529,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Water contact angle and (b) 3D-EEM spectra of DOM from \u003cem\u003eC. rupestris\u003c/em\u003e biomass treated with different \u003csup\u003e60\u003c/sup\u003eCoγ–ray irradiation doses\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/9e5cda81fd3ed360eb35dd36.png"},{"id":70561336,"identity":"f5c7144e-255b-4621-90f8-d531fcc0bf9d","added_by":"auto","created_at":"2024-12-04 11:57:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":76802,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Langmuir and (b) Freundlich isotherms of Pb\u003csup\u003e2+\u003c/sup\u003e on the \u003cem\u003eC. rupestris\u003c/em\u003e biomass treated with different \u003csup\u003e60\u003c/sup\u003eCoγ–ray irradiation doses\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/f6eaa21ba9a29ca7f88683c9.png"},{"id":70561642,"identity":"bd5fb755-502f-4163-a7cd-5c311907af49","added_by":"auto","created_at":"2024-12-04 12:05:47","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":49235,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Influence of initial pH and (b) co\u003cstrong\u003e–\u003c/strong\u003eexisting ions on Pb\u003csup\u003e2+\u003c/sup\u003e adsorption for \u003cem\u003eC. rupestris\u003c/em\u003e biomass treated with different \u003csup\u003e60\u003c/sup\u003eCoγ–ray irradiation doses\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/d24ab795d03b6e197d71ebed.png"},{"id":70563510,"identity":"6fe3a884-57da-4597-882a-2f3bc4aec2f0","added_by":"auto","created_at":"2024-12-04 12:21:46","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":70929,"visible":true,"origin":"","legend":"\u003cp\u003eAdsorption efficiency of \u003cem\u003eC. rupestris \u003c/em\u003ebiomass samples irradiated by \u003csup\u003e60\u003c/sup\u003eCoγ-rays on Pb\u003csup\u003e2+ \u003c/sup\u003eadsorption for four consecutive adsorption/desorption cycles\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/4200ef4f9e381ec48d76197e.png"},{"id":70563209,"identity":"88ede363-68ca-4237-baa0-3735f81b9b5d","added_by":"auto","created_at":"2024-12-04 12:13:46","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1040750,"visible":true,"origin":"","legend":"\u003cp\u003eSEM-EDS spectrum of \u003cem\u003eC. rupestris biomass\u003c/em\u003e samples irradiated by \u003csup\u003e60\u003c/sup\u003eCoγ-rays after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/560a0556f3c36c7ad301e2d3.png"},{"id":70559744,"identity":"5918f220-606d-4bc0-b141-fd3b7baabd72","added_by":"auto","created_at":"2024-12-04 11:49:46","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":187340,"visible":true,"origin":"","legend":"\u003cp\u003eC 1s spectra of \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples irradiated by \u003csup\u003e60\u003c/sup\u003eCoγ-ray before (above) and after (below) adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/f094f8d492993dabef3d6f48.png"},{"id":70563210,"identity":"90a674a7-c7dc-493b-a1a5-a60a8fcb1c00","added_by":"auto","created_at":"2024-12-04 12:13:46","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":91463,"visible":true,"origin":"","legend":"\u003cp\u003ePb 4f7/2 and Pb 4f5/2 spectra of \u003cem\u003eC. rupestris\u003c/em\u003e biomass treated with different \u003csup\u003e60\u003c/sup\u003eCoγ–ray irradiation doses\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/4a16473e77e7ca8fb3db0a23.png"},{"id":70561337,"identity":"50925464-dc29-45d8-87aa-c34e3426e514","added_by":"auto","created_at":"2024-12-04 11:57:46","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":120137,"visible":true,"origin":"","legend":"\u003cp\u003eXRD of \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples irradiated by \u003csup\u003e60\u003c/sup\u003eCoγ-ray after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/eb72d289f8947ff8cb4237a0.png"},{"id":73056720,"identity":"4d5774a3-e156-498f-9c04-e0be90f53e7f","added_by":"auto","created_at":"2025-01-06 10:18:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3199422,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/fe04411f-4fda-4a1e-b802-0da0db4cd9f9.pdf"},{"id":70563212,"identity":"2b915edc-8f54-46f3-871b-49669b41ea7b","added_by":"auto","created_at":"2024-12-04 12:13:46","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":291852,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.png","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/19ebc46eb80a5a4d0b5d5c6f.png"},{"id":70561631,"identity":"2ec8cfe1-eb9a-46a0-b1a2-0f0dc99aec96","added_by":"auto","created_at":"2024-12-04 12:05:46","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":830190,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-5103068/v1/c19e98161e8b682b66621e3d.docx"}],"financialInterests":"","formattedTitle":"\u003cp\u003e\u003csup\u003e60\u003c/sup\u003eCoγ activation of \u003cem\u003eCladophora rupestris\u003c/em\u003e biomass functional groups\u003cem\u003e \u003c/em\u003eand its effect on Pb\u003csup\u003e2+\u003c/sup\u003e adsorption\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eHeavy metals (HMs) have attracted widespread attention (Godoy et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) because of their toxicity and increased presence in waterbodies. Pb\u003csup\u003e2+\u003c/sup\u003e, known for its bioaccumulation and non\u0026ndash;degradability, is one of the most toxic HMs (Huang et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Yang et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Yuan et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), and the amount of Pb\u003csup\u003e2+\u003c/sup\u003e discharged into water systems in China increases every year (Wang et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Pb\u003csup\u003e2+\u003c/sup\u003e contamination is a serious threat to human health and the environment (Yang et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePb\u003csup\u003e2+\u003c/sup\u003e can be removed from water systems via ion exchange, membrane filtration, chemical precipitation, and adsorption (Cao et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ge et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Miao and Li \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Zhang et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The adsorption method has attracted widespread attention owing to its low cost, high efficiency, simple operation, and short treatment cycle (Miao and Li \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Zhang et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Cao et al. (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) and Zhang et al. (\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) reported that \u003cem\u003eCladophora rupestris (C. rupestris\u003c/em\u003e), which is widely distributed in natural waterbodies (Sucaldito and Camacho \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Zulkifly et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), presented favorable adsorption for Pb\u003csup\u003e2+\u003c/sup\u003e and Cd\u003csup\u003e2+\u003c/sup\u003e. Therefore, \u003cem\u003eC. rupestris\u003c/em\u003e is valuable as a biosorbent for the removal of Pb\u003csup\u003e2+\u003c/sup\u003e from waterbodies. The theoretical Pb\u003csup\u003e2+\u003c/sup\u003e adsorption capacity (Qm) of the organic frameworks of \u003cem\u003eC. rupestris\u003c/em\u003e has been found to be 15.02 mg/g (Zhang et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eBiochar has been widely used to remediate HM contamination (Wang et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Moreover, modification of biomass materials, such as silicate-modified oil tea camellia shell-derived biochar for Cd\u003csup\u003e2+\u003c/sup\u003e removal, can often improve their HM absorption capacity (Cai et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Wang et al. (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) reported that the Pb\u003csup\u003e2+\u003c/sup\u003e Qm of fresh biochar at 350 and 650\u0026deg;C was 279.85 and 286.07 mg\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. Zhang et al. (\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) demonstrated that humic- and protein-like substances were involved in Pb\u003csup\u003e2+\u003c/sup\u003e adsorption, and Wang et al. (\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) demonstrated that biochar can enhance Pb\u003csup\u003e2+\u003c/sup\u003e adsorption through the cosorption of dissolved organic matter (DOM). Simultaneously, ultraviolet (UV) irradiation can promote the generation of new oxidation functional groups (Wang et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Ethylenediamine-modified pectins have exhibited a remarkable removal efficiency for Pb\u003csup\u003e2+\u003c/sup\u003e (Liang et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eGamma radiation (γ-ray) is considered an effective physical method for modifying biomass materials by engaging in cross-linking, grafting, copolymerization, and disintegration processes (Choi and Kim \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Mohamed et al. (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) showed that \u003csup\u003e60\u003c/sup\u003eCoγ-ray could improve the surface characteristics of clay minerals, enhancing the efficient removal of Gd\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e, with the primary mechanism being radical chemistry (Han et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Zhao et al. (\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) found that polyisoprene underwent molecular transformations upon exposure to γ-ray, generating carbonyl (C\u0026thinsp;=\u0026thinsp;O) and hydroxyl (O\u0026thinsp;\u0026minus;\u0026thinsp;H) groups, and polyisoprene irradiated with 100 kGy of \u003csup\u003e60\u003c/sup\u003eCoγ-ray caused the fracture of the carbon main chain and oxidation of the side-chain functional groups. Li et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) found that higher \u003csup\u003e60\u003c/sup\u003eCoγ-ray doses can degrade the dietary fiber of a navel orange, rupturing the crystalline part of the fiber and breaking the covalent bonds. According to Gewert et al. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) and Wen et al. (\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), \u003csup\u003e60\u003c/sup\u003eCoγ-ray can break the main chain of polymers, and the chemical bonds of DOM can be broken and recombined, thus changing the structural characteristics of the DOM of \u003cem\u003eC. rupestris\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eIn this study, to investigate the interface structure, chemical properties, and functional group activation of \u003cem\u003eC. rupestris\u003c/em\u003e biomass irradiated by \u003csup\u003e60\u003c/sup\u003eCoγ-ray, \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples were treated with different \u003csup\u003e60\u003c/sup\u003eCoγ-ray doses (0, 20, 100, and 200 kGy). Pb\u003csup\u003e2+\u003c/sup\u003e adsorption characteristics were investigated to reveal the Pb\u003csup\u003e2+\u003c/sup\u003e adsorption mechanism of \u003cem\u003eC. rupestris\u003c/em\u003e biomass irradiated by \u003csup\u003e60\u003c/sup\u003eCoγ-ray. This study provides new insight into modification of biomass materials for enhanced removal of HMs from waterbodies.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Materials and reagents\u003c/h2\u003e \u003cp\u003e \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples were collected from Heichiba in Hefei city, Anhui, China. The \u003cem\u003eC. rupestris\u003c/em\u003e samples were washed with running water, dried in an oven at 60 ℃ for 24 h to constant weight, and then crushed through a 100-mesh sieve.\u003c/p\u003e \u003cp\u003eThe lead nitrate (Pb(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e) was analytical purity grade and obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). All reagents were analytical purity grade, and solutions were prepared with ultrapure water (18.25 MΩ\u0026bull;cm).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. \u003csup\u003e60\u003c/sup\u003eCoγ-ray irradiation\u003c/h2\u003e \u003cp\u003eThe \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples were irradiated with \u003csup\u003e60\u003c/sup\u003eCoγ-ray doses of 0, 20, 100, and 200 kGy (Furui High Energy Technology Co., Ltd, Guangzhou, China). The samples were stored in sealed brown glass bottles.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Materials characterization\u003c/h2\u003e \u003cp\u003eSurface morphology changes were observed by scanning electron microscopy (SEM; s\u0026ndash;4800, Hitachi, Japan). The particle size distribution and specific surface area were measured by a laser particle size distributor (BT\u0026ndash;9300H, Bettersize, China). Surface hydrophilicity was measured by a contact angle analyzer (DSA100, KRUSS, Hamburg, Germany). Surface electronegativity was measured by a zeta potential analyzer (Zetasizer Nano ZS90, Malvern, UK). Crystalline phase and crystallinity were analyzed by X-ray diffraction (XRD; D8 ADVANCE, Bruker, Germany). Functional groups were characterized by Fourier transform infrared spectroscopy (FTIR; Nicolette 50, Thermo Scientific, USA). The chemical composition of the DOM was analyzed by a three-dimensional fluorescence spectrophotometer (3D\u0026ndash;EEM; f\u0026ndash;4500, Horiba, Japan) and UV-visible spectrophotometer (UV-Vis; UV\u0026ndash;1452, Shimazu, Japan). The active centers and chemical states before and after Pb\u003csup\u003e2+\u003c/sup\u003e adsorption were characterized by X-ray photoelectron spectroscopy (XPS; Escalab 250, Thermo\u0026ndash;VG Scientific, USA). The specific experimental steps are presented in Supplementary Information S1.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Batch adsorption experiments\u003c/h2\u003e \u003cp\u003eAdsorption isotherm experiments were performed at the initial Pb\u003csup\u003e2+\u003c/sup\u003e concentrations of 0, 25, 50, 100, 150, 200, 300, and 400 mg/L with a 4 g/L solid-to-liquid ratio in a 180 rpm thermostatic oscillator at 25 ℃ for 24 h. The mixtures were filtered with a 0.45 \u0026micro;m syringe filter, and the concentrations of Pb\u003csup\u003e2+\u003c/sup\u003e in the supernatant were analyzed by a flame atomic absorption spectrophotometer (ZEEnit 700P, Analytic Jena, Germany). The experiments were performed three times.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Environmental factors\u003c/h2\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e2.5.1 pH\u003c/h2\u003e \u003cp\u003eThe \u003cem\u003eC. rupestris\u003c/em\u003e biomass of 0.100 g treated with different \u003csup\u003e60\u003c/sup\u003eCoγ-ray irradiation doses were added to 25 mL of Pb\u003csup\u003e2+\u003c/sup\u003e solution at a concentration of 400 mg/L, and the pH of the mixtures was adjusted by 0.1 M HNO\u003csub\u003e3\u003c/sub\u003e and 0.1 M NaOH to 2, 3, 4, 5, and 6 using a similar experimental step with adsorption isotherms.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e2.5.2 Metal ion competition\u003c/h2\u003e \u003cp\u003eThe \u003cem\u003eC. rupestris\u003c/em\u003e biomass of 0.100 g treated with different \u003csup\u003e60\u003c/sup\u003eCoγ-ray irradiation doses were added to 25 mL of a solution containing 50 mg/L solution of Pb\u003csup\u003e2+\u003c/sup\u003e, Cd\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Zn\u003csup\u003e2+\u003c/sup\u003e, and Ni\u003csup\u003e2+\u003c/sup\u003e to analyze the Qm of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass to different HM ions.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Release of net alkali metal cations and reusability\u003c/h2\u003e \u003cp\u003eThe K\u003csup\u003e+\u003c/sup\u003e, Na\u003csup\u003e+\u003c/sup\u003e, Ca\u003csup\u003e2+\u003c/sup\u003e, and Mg\u003csup\u003e2+\u003c/sup\u003e concentrations were determined in pure water and in a 400 mg/L Pb\u003csup\u003e2+\u003c/sup\u003e solution, and the water-soluble K\u003csup\u003e+\u003c/sup\u003e, Na\u003csup\u003e+\u003c/sup\u003e, Ca\u003csup\u003e2+\u003c/sup\u003e, and Mg\u003csup\u003e2+\u003c/sup\u003e contents were calculated per unit of the biomass (Shen et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). After the equilibrium of adsorption, the sample was repeatedly centrifuged and filtered with ultrapure water for 3 times, and then 0.1 M dilute hydrochloric acid was added for resolution for 24 h, and the cycle was repeated for 4 times.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.7. Data analysis\u003c/h2\u003e \u003cp\u003eThe adsorption isotherms were fitted using the Langmuir and Freundlich models (details in Supplementary Information S2). The experimental data were analyzed and graphed using SPSS 22.0 and Origin2018, and the Duncan method was used for the significant difference comparison (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. Characteristics of \u003cem\u003eC. rupestris\u003c/em\u003e biomass irradiated by \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-rays\u003c/h2\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.1. Morphology, particle size, and crystallinity\u003c/h2\u003e\n \u003cp\u003eThe surface morphology of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass treated with different \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation doses is shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples were rough and full of grooves, with particles attached. However, cracks were gradually generated on the surface of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples treated with \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation and pores tended to develop on the interior surface of the samples. Notably, with increasing \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation doses, the surface morphology of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples changed more drastically, showing voids, increased tiny pores on the smooth surface, and an irregular structure. Overall, \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray increased the specific surface area of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples, and more developed pore structures were observed at higher \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation doses.\u003c/p\u003e\n \u003cp\u003eThe particle size distribution of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass treated with \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray is shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea. As the \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation dose increased from 0 to 200 kGy, the median diameter (D50) of the particle decreased from 52.26 to 39.73 \u0026micro;m, respectively. The drop ratio was 23.98% when the \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation dose was 200 kGy. The specific surface area of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples treated with \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray increased 14.6% from 159.1 to 182.3 m\u003csup\u003e2\u003c/sup\u003e/kg at radiation doses of 0 to 200 kGy, respectively, indicating that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray can cause fracture and breakage, creating a larger surface area that can be conducive to activate relevant functional groups (Zhu et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e). These findings are similar to those of Mohamed et al. (\u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe XRD spectra are shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb. The peak intensity at 2\u0026theta; values of 29.76\u0026deg;, 39.76\u0026deg;, 47.78\u0026deg;, and 48.89\u0026deg;, which is known as CaCO\u003csub\u003e3\u003c/sub\u003e (Miao and Li \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e), was significantly increased, particularly the 2\u0026theta; value of 29.76\u0026deg;. This increase was more evident as the irradiation dose increased, indicating that the crystallinity and brittleness of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass increased with increasing \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation doses (Xue et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e), and the \u003cem\u003eC. rupestris\u003c/em\u003e biomass were easier to break and fracture (Shen et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). The XRD spectra show that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray led to the \u003cem\u003eC. rupestris\u003c/em\u003e biomass having an amorphous structure and their experiencing the breakage of the main polymer chain, which contributed to its crystallinity (Shen et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). This result is consistent with the particle size analysis result.\u003c/p\u003e\n \u003cp\u003eTherefore, \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray can cause the fracture and fragmentation of \u003cem\u003eC. rupestris\u003c/em\u003e, resulting in a reduction in particle size and an increase in specific surface area, which can increase its HM-ion adsorption potential.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.2. Zeta potentials and functional groups\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec displays the zeta potentials of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass with pH values in the range of 2\u0026ndash;9. With increasing \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation doses, the electronegativity of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass s increased, indicating that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray causes \u003cem\u003eC. rupestris\u003c/em\u003e biomass to attract electrons and become negatively charged (Liang et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). In summary, \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray significantly increased the electronegativity of \u003cem\u003eC. rupestris\u003c/em\u003e biomass. The increased electronegativity might increase the adsorption of cations owing to the reduced electrostatic repulsion between the adsorbent and cations.\u003c/p\u003e\n \u003cp\u003eThe FTIR results of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples treated with \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray are shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ed. The deformation vibration of the aromatic CH\u003csub\u003e2\u003c/sub\u003e peak at 1428.53 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Godoy et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e) and bending vibration of the aromatic C\u0026thinsp;\u0026minus;\u0026thinsp;H peaks at 876.02 and 712.73 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Tan et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e; Yang et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e) significantly decreased as the \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation dose increased, indicating that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray induced the benzene-ring breakage of \u003cem\u003eC. rupestris\u003c/em\u003e biomass (Li et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). The peaks at 2924.76 and 2858.10 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Guan et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e), corresponding to the symmetric and symmetric stretching vibrations of aliphatic C\u0026thinsp;\u0026minus;\u0026thinsp;H, respectively, decreased (Zhu et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e), implying the cleavage of the C\u0026thinsp;\u0026minus;\u0026thinsp;H and C\u0026thinsp;\u0026minus;\u0026thinsp;C bonds from the main polymer chain. The stretching vibration of O\u0026thinsp;\u0026minus;\u0026thinsp;H at 3374.38 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Zhang et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e) was enhanced and blue shifted, indicating the impact of different irradiation treatments on the structure of hydrogen and the hydroxyl group in cellulose and hemicelluloses (Li et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). The intensity of the C\u0026thinsp;=\u0026thinsp;O characteristic peak at 1647.89 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Liu et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e), the position and peak shape of the asymmetric stretching vibration and symmetric stretching vibration of C\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;C at 1161.41 and 1110.30 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e(Chen et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e), and the stretching vibration of C\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;H at 1034.61 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e all shifted accordingly after \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;\u003cstrong\u003e-\u003c/strong\u003eray irradiation. These results demonstrate that oxidation reactions occurred with \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation that caused a series of complex chain expansions, branching, and chain termination, and eventually led to the formation of C\u0026thinsp;=\u0026thinsp;O, C\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;C, and C\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;H (Zhu et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e). The peaks at 1579.18 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for C\u0026thinsp;\u0026minus;\u0026thinsp;N and N\u0026thinsp;\u0026minus;\u0026thinsp;H showed marked shoulder peaks after \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation, indicating that more amide functional groups were generated (Guan et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). This result is consistent with that of Wang et al. (\u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e), who found that C\u0026thinsp;=\u0026thinsp;O and O\u0026thinsp;\u0026minus;\u0026thinsp;H can be formed by UV irradiation. The results are also consistent with those of Zhu et al. (\u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e) who found that high-dose irradiation of \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray can significantly destroy the structure of lignocellulose.\u003c/p\u003e\n \u003cp\u003eIn conclusion, \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray can alter the elemental composition and functional groups of \u003cem\u003eC. rupestris\u003c/em\u003e biomass, especially in carbon- and oxygen-containing functional groups (CFGs and OFGs).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.3. Hydrophilicity\u003c/h2\u003e\n \u003cp\u003eThe water contact angle is used to characterize the hydrophobicity of a material, and the larger the contact angle, the more hydrophobic the material (Hu et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). The hydrophilicity was enhanced, and the adsorption amounts of Pb\u003csup\u003e2+\u003c/sup\u003e and Cu\u003csup\u003e2+\u003c/sup\u003e increased after microplastic aging (Wang et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). Figure \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea shows that the water contact angle of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass decreased from 99.7\u0026deg; to 87.2\u0026deg; a\u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation doses increased from 0 to 200 kGy, respectively, indicating that the hydrophilicity of \u003cem\u003eC. rupestris\u003c/em\u003e biomass increased. \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation can produce hydrophilic groups, which enhances the Pb\u003csup\u003e2+\u003c/sup\u003e adsorption efficiency (Wang et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e; Liu et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.4. DOM\u003c/h2\u003e\n \u003cp\u003eDOM can adsorb, complex, and redox HMs (Mu et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). Huang et al. (\u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e) reported that DOM and Pb\u003csup\u003e2+\u003c/sup\u003e can form soluble complexes to inhibit the adsorption and precipitation of HMs. After treating the \u003cem\u003eC. rupestris\u003c/em\u003e biomass with \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray, the 3D-EEM fluorescence spectra of the DOM released from the \u003cem\u003eC. rupestris\u003c/em\u003e biomass changed (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb). The intensity of peak A at Ex/Em\u0026thinsp;=\u0026thinsp;276\u0026ndash;279/347\u0026ndash;353 nm, assigned to tryptophan-like substances (Li et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e; Liu et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e; Teng et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e), decreased significantly as the \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation dose increased and disappeared when the \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation dose reached 200 kGy. Meanwhile, peak B at Ex/Em\u0026thinsp;=\u0026thinsp;336\u0026ndash;342/422\u0026ndash;428 nm, assigned to humic acid (HA)-like substances (Li et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e; Liu et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e; Teng et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e), exhibited a significant red shift with \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray treatment, and the fluorescence intensity of the humic component increased in the DOM, especially when the irradiation dose reached 200 kGy. Therefore, \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray can cause degradation of protein components and cause the amino group of the protein to fall off, thus increasing the humification process of DOM (Zhang et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). Photoaging may promote the release of soluble organics (Hu et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e), causing amino groups of the protein to fall off and the absorption sites of cations to increase, which might increase the Pb\u003csup\u003e2+\u003c/sup\u003e adsorption efficiency (Chen et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). Shi et al. (\u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e) demonstrated that Pb\u003csup\u003e2+\u003c/sup\u003e was directly adsorbed by green algae until equilibrium in the presence of HA, and Pb\u003csup\u003e2+\u003c/sup\u003e bound to the algae in the form of a Pb\u0026ndash;FA conjugated copolymer (Shi et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). Pb\u003csup\u003e2+\u003c/sup\u003e can form ternary complexes with biodegradable microplastics and their leached HA, providing new adsorption sites for unbound Pb\u003csup\u003e2+\u003c/sup\u003e, thus enhancing the Qm for Pb\u003csup\u003e2+\u003c/sup\u003e (Li et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eIn conclusion, \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray caused preferential degradation of protein components in the DOM of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass (Cao et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e; Yang et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e), and protein deamination increased the absorption sites of the cations.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig. S1a, the absorption wavelength of the DOM released from the \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples shifted toward the higher wavelength with an increase in the \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation, suggesting that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray caused the oxidation of the DOM (Gao et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). The absorption peaks of the UV-Vis spectra at 250\u0026ndash;290 nm represent heterocyclic aromatic hydrocarbons, and 390 nm represents the carbonyl or conjugated groups (Teng et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). Fig. S1a shows that the UV-Vis spectra at 281 nm were blue shifted to 269 nm, suggesting that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray caused the heterocyclic aromatic hydrocarbons to change in the DOM and indicating that the \u0026pi;\u0026ndash;\u0026pi;* electron transition of algae-derived DOM decreased with increasing irradiation doses (Janot et al. \u003cspan class=\"CitationRef\"\u003e2010\u003c/span\u003e). The spectra at 400 nm were blue shifted to 390 nm, indicating that carbonyl or conjugated groups were produced by \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation and \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray had some effect on the polyene structure containing seven conjugated double bonds in the visible region of the algae-derived DOM (Klempov\u0026aacute; et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e; Zhou et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eIn conclusion, \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray causes successive decomposition and transformation of DOM, altering the molecular configuration of DOM (Dryer et al. \u003cspan class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2. Adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e onto \u003cem\u003eC. rupestris\u003c/em\u003e biomass\u003c/h2\u003e\n \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.1. Qm\u003c/h2\u003e\n \u003cp\u003eThe Langmuir and Freundlich isotherms of Pb\u003csup\u003e2+\u003c/sup\u003e on the \u003cem\u003eC. rupestris\u003c/em\u003e biomass treated with different doses of \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation are shown in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. The theoretical Pb\u003csup\u003e2+\u003c/sup\u003e Qm of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass increased significantly to 74.907, 79.800, and 82.550 mg/g after \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation doses of 20, 100, and 200 kGy, respectively, with an increase of 2.6\u0026ndash;2.9 times. After \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation, the Pb\u003csup\u003e2+\u003c/sup\u003e adsorption of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass showed a linear growth trend at equilibrium concentrations (Ces) in the range of 0\u0026ndash;40 mg/L and then became saturated when Ce\u0026thinsp;\u0026ge;\u0026thinsp;40 mg/L. This may be attributed to \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray, which increases the adsorption sites and functional groups and reduces the spatial site resistance, thus significantly increasing the equilibrium Qm (Spessato et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe fitting parameters of the Langmuir and Freundlich models are listed in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The adsorption isotherms were well fit by the Langmuir and Freundlich models (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;\u0026ge;\u0026thinsp;0.92) when the \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation dose was lower than 100 kGy; subsequently, the R\u003csup\u003e2\u003c/sup\u003e dropped significantly, particularly in the Freundlich model (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.70) at 200 kGy, which indicates that the Freundlich model was unable to describe the adsorption characteristics in the analyzed cases. The K\u003csub\u003eL\u003c/sub\u003e values of the Langmuir model decreased as the \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation dose increased, indicating that the adsorption process was not a single surface chemisorption but was also affected by other forces (Li et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e; Martins et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e). Liu et al. (\u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e) found that the surface of UV-aged microplastics is rougher and has some cracks. The high energy of \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray can allow oxidation to occur in the deeper layers, which leads to enhanced chemisorption (Huang et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e; Teng et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e; Zhang et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). The Freundlich constant K\u003csub\u003ef\u003c/sub\u003e\u0026mdash;free energy of adsorption\u0026mdash;indicates the lative biosorption capacity of the biosorbent bonding energy. In this study, K\u003csub\u003ef\u003c/sub\u003e was 1.48\u0026ndash;10.72, which reflects the high affinity of Pb\u003csup\u003e2+\u003c/sup\u003e to the binding sites of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass (Pillai et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e), especially at the \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation dose of 200 kGy. The slope 1/n in the Freundlich model was less than 1, indicating that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation increased the surface heterogeneity of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass(Xie et al.\u0026nbsp;\u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAdsorption isotherm parameters of the Langmuir and Freundlich models\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"13\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003eIrradiation treatment\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"11\"\u003e\n \u003cp\u003eModel parameters\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"5\"\u003e\n \u003cp\u003eLangmuir\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"5\"\u003e\n \u003cp\u003eFreundlich\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003eL\u003c/sub\u003e/L\u0026bull;mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQm/mg\u0026bull;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003ef\u003c/sub\u003e mg\u003csup\u003e1\u0026thinsp;\u0026minus;\u0026thinsp;1/n\u003c/sup\u003e\u0026bull;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026bull;L\u003csup\u003e1/n\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1/n\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0 kGy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.808\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e30.383\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.924\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.272\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.981\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20 kGy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.137\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e74.907\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.965\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.494\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.943\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100 kGy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e79.800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.494\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.999\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e200 kGy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.167\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e82.550\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.842\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.439\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.696\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eIn conclusion, \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation decreases the free energy of adsorption, increasing the biosorption capacity and affinity of Pb\u003csup\u003e2+\u003c/sup\u003e to the binding sites of \u003cem\u003eC. rupestris\u003c/em\u003e biomass.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.2. Influence of pH\u003c/h2\u003e\n \u003cp\u003eThe influence of pH on the Pb\u003csup\u003e2+\u003c/sup\u003e adsorption capability of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass is shown in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea. The Pb\u003csup\u003e2+\u003c/sup\u003e adsorption capability of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass increased as the pH increased, and the Pb\u003csup\u003e2+\u003c/sup\u003e Qm increased to 19.04 mg/g when the pH was 6. This trend can be attributed to the increased dissolution of insoluble crystalline minerals in low pH environments, which releases a large number of cations (H\u003csup\u003e+\u003c/sup\u003e, K\u003csup\u003e+\u003c/sup\u003e, Na\u003csup\u003e+\u003c/sup\u003e, Ca\u003csup\u003e2+\u003c/sup\u003e, and Mg\u003csup\u003e2+\u003c/sup\u003e) that can compete with Pb\u003csup\u003e2+\u003c/sup\u003e for adsorption sites, leading to a decrease in Pb\u003csup\u003e2+\u003c/sup\u003e adsorption (Wang et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). As the solution pH increased, deprotonation of the functional groups led to the formation of negative charges, facilitating cation adsorption through electrostatic interactions (Liang et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). After \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation, the pH had no significant effect on the Pb\u003csup\u003e2+\u003c/sup\u003e adsorption.\u003c/p\u003e\n \u003cp\u003eThe above phenomena indicate that \u003cem\u003eC. rupestris\u003c/em\u003e biomass has better environmental adaptability to Pb\u003csup\u003e2+\u003c/sup\u003e after \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation (Yang et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e)\u0026mdash;consistent with the results of the zeta potential analysis.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec21\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.3. Competitive adsorption of other HM ions\u003c/h2\u003e\n \u003cp\u003eThe competitive adsorption of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass is shown in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb. There was a significant difference for the different HMs, and the order of Qm was Pb\u003csup\u003e2+\u003c/sup\u003e \u0026gt; Cd\u003csup\u003e2+\u003c/sup\u003e \u0026gt; Ni\u003csup\u003e2+\u003c/sup\u003e \u0026asymp; Zn\u003csup\u003e2+\u003c/sup\u003e \u0026gt; Cu\u003csup\u003e2+\u003c/sup\u003e, implying preferential adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e. These results are similar to those of Cao et al. (\u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e), in which \u003cem\u003eC. rupestris\u003c/em\u003e was found to be able to accumulate Pb\u003csup\u003e2+\u003c/sup\u003e. Zhang et al. (\u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e) suggested that \u003cem\u003eC. rupestris\u003c/em\u003e has a bioremediation potential for Cd\u003csup\u003e2+\u003c/sup\u003e. After the irradiation of \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray at doses of 0 to 200 kGy, the Pb\u003csup\u003e2+\u003c/sup\u003e Qm increased from 10.73\u0026ndash;24.00%, respectively. The adsorption capacities of Zn\u003csup\u003e2+\u003c/sup\u003e, Cd\u003csup\u003e2+\u003c/sup\u003e, and Ni\u003csup\u003e2+\u003c/sup\u003e also improved significantly after \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation, but the Cu\u003csup\u003e2+\u003c/sup\u003e Qm did not significantly increase.\u003c/p\u003e\n \u003cp\u003eThese findings suggest that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation can activate the relevant adsorption sites and functional groups, and, among all the HMs tested, \u003cem\u003eC. rupestris\u003c/em\u003e biomass demonstrated the highest affinity for Pb\u003csup\u003e2+\u003c/sup\u003e. These findings are similar to those of Zhao et al. (\u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec22\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.4. The reusability and desorption\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e, after four desorption and regeneration cycles, the adsorption capacity of Pb\u003csup\u003e2+\u003c/sup\u003e on \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples after \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation only decreased by 28.25%, 17.51%, 18.97% and 15.36%. This phenomenon suggests that the adsorption capacity of the biomass is still high after several desorption and regeneration cycles (Chen et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e)\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec23\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3. Effect of groups activation by \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray and adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e, 10.1 wt % Pb was detected on the \u003cem\u003eC. rupestris biomass\u003c/em\u003e samples and Pb was mainly adsorbed on the surface and pores by combining with C and O.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig. S2 and Table S1, \u003cem\u003eC. rupestris\u003c/em\u003e biomass contains a large amount of O (50.37%), C (28.12%), and Ca (19.22%), as well as a small amount of N (2.30%). The functional groups and amorphous parts have been reported to be composed of these elements can act as initiators for photodegradation (Zhu et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e). The O content and O/C ratio increased with increased \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation doses, indicating that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray can cause \u003cem\u003eC. rupestris\u003c/em\u003e biomass to produce more OFGs (Hu et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). The Pb 4f characteristic peak appeared in the irradiated \u003cem\u003eC. rupestris\u003c/em\u003e biomass, indicating that Pb\u003csup\u003e2+\u003c/sup\u003e was successfully adsorbed onto the \u003cem\u003eC. rupestris\u003c/em\u003e biomass.\u003c/p\u003e\n \u003cp\u003eThe C 1s peak of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass can be deconvoluted into four individual peaks corresponding to C\u0026minus;(C, H)/C\u0026thinsp;=\u0026thinsp;C (284.80 eV), C\u0026thinsp;\u0026minus;\u0026thinsp;O (286.20\u0026ndash;286.73 eV), C\u0026thinsp;=\u0026thinsp;O (287.81\u0026ndash;288.03 eV), and O\u0026thinsp;\u0026minus;\u0026thinsp;C\u0026thinsp;=\u0026thinsp;O (288.60\u0026ndash;289.55 eV) (Zafar et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e) (Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e). After the irradiation of \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray at doses of 0 to 200 kGy, the peak intensity of C\u0026minus;(C, H)/C\u0026thinsp;=\u0026thinsp;C of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass decreased from 15.14\u0026ndash;11.25%, and the peak intensity of C\u0026thinsp;\u0026minus;\u0026thinsp;O increased from 15.6 to 11.34%, respectively. This result indicates that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation caused the C\u0026minus;(C, H) bonds to fracture and the benzene ring to open. These broken bonds are highly reactive and rapidly react with O\u003csub\u003e2\u003c/sub\u003e to form C\u0026thinsp;\u0026minus;\u0026thinsp;O bonds (Wang et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e), which subsequently form C\u0026thinsp;=\u0026thinsp;O bonds, leading to the generation of unsaturated bonds represented by alcohols, aldehydes, and acids (Zhu et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). The C\u0026minus;(C, H)/C\u0026thinsp;=\u0026thinsp;C content in the \u003cem\u003eC. rupestris\u003c/em\u003e biomass irradiated with 0 kGy of \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray and loaded with Pb\u003csup\u003e2+\u003c/sup\u003e showed the most pronounced shift of 2.61%, indicating that the aromatic structure of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass participated in the Pb\u0026ndash;\u0026pi; interaction adsorption process (Liu et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). After being treated with \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray, the consumption of C\u0026thinsp;\u0026minus;\u0026thinsp;O was between 10.23% and 11.13%, indicating that the functional groups with C as the backbone underwent significant changes.\u003c/p\u003e\n \u003cp\u003eOxygen atoms often act as electron donors to form stable covalent bonds with HMs and play a crucial role in chelation (Wu et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e). The primary OFGs in the \u003cem\u003eC. rupestris\u003c/em\u003e biomass were C\u0026thinsp;=\u0026thinsp;O and C\u0026thinsp;\u0026minus;\u0026thinsp;O (Fig. S3). After \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation, the content of the C\u0026thinsp;=\u0026thinsp;O bonds decreased while that of the C\u0026thinsp;\u0026minus;\u0026thinsp;O bonds increased, and the ratio of C\u0026thinsp;=\u0026thinsp;O/C\u0026thinsp;\u0026minus;\u0026thinsp;O decreased from 1.56 to 1 for \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray doses of 0 to 200 kGy, respectively. The O\u0026thinsp;\u0026minus;\u0026thinsp;C\u0026thinsp;=\u0026thinsp;O functional group was observed when the \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray dose was 200 kGy, indicating that the OFGs of \u003cem\u003eC. rupestris\u003c/em\u003e biomass were enhanced after \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation (Wu et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). The binding energy of the OFGs declined in the Pb-loaded \u003cem\u003eC. rupestris\u003c/em\u003e biomass, suggesting that the chelation by the OFGs is crucial during Pb\u003csup\u003e2+\u003c/sup\u003e adsorption. After \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation, the content of the C\u0026thinsp;\u0026minus;\u0026thinsp;O bonds in the \u003cem\u003eC. rupestris\u003c/em\u003e biomass loaded with Pb\u003csup\u003e2+\u003c/sup\u003e decreased from 12.97\u0026ndash;9.36% for \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray doses of 0 to 200 kGy, respectively. Particularly, the O\u0026thinsp;\u0026minus;\u0026thinsp;C\u0026thinsp;=\u0026thinsp;O content of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass sample treated with 200 kGy of \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation decreased to 5.77%, indicating that O\u0026thinsp;\u0026minus;\u0026thinsp;C\u0026thinsp;=\u0026thinsp;O plays an important role in Pb\u003csup\u003e2+\u003c/sup\u003e adsorption (Chen et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). In summary, \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation activates the OFGs of \u003cem\u003eC. rupestris\u003c/em\u003e biomass, enhancing the ability of the OFGs in \u003cem\u003eC. rupestris\u003c/em\u003e biomass to bind with Pb\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e, the Pb 4f7/2 and Pb 4f5/2 spectra of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples after \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation can be deconvoluted into a pair of peaks corresponding to Pb\u003csup\u003e2+\u003c/sup\u003e and Pb\u0026thinsp;\u0026minus;\u0026thinsp;O (Wu et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e). Therefore, the main combined forms of Pb were Pb\u003csup\u003e2+\u003c/sup\u003e and Pb\u0026thinsp;\u0026minus;\u0026thinsp;O. This phenomenon suggests that not only electrostatic interactions but also bonding interactions existed between Pb and \u003cem\u003eC. rupestris\u003c/em\u003e biomass (Wu et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e). The Pb\u003csup\u003e2+\u003c/sup\u003e/Pb\u0026thinsp;\u0026minus;\u0026thinsp;O ratio changed from 1.53 to 0.85 after the irradiation of \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray at doses of 0 to 200 kGy, respectively, indicating that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation promoted the bonding interaction between the \u003cem\u003eC. rupestris\u003c/em\u003e biomass and Pb to form Pb\u0026thinsp;\u0026minus;\u0026thinsp;O.\u003c/p\u003e\n \u003cp\u003eHowever, the XRD results show that no Pb precipitation was generated after the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e (Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e), indicating that precipitation was not an adsorption mechanism of Pb\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec24\" class=\"Section2\"\u003e\n \u003ch2\u003e\u003cstrong\u003e3.4 Release of metal ions and DOM from\u003c/strong\u003e \u003cstrong\u003eC. rupestris\u003c/strong\u003e \u003cstrong\u003ebiomass by\u003c/strong\u003e \u003csup\u003e\u003cstrong\u003e60\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003eCo\u0026gamma;-ray\u003c/strong\u003e\u003c/h2\u003e\n \u003cp\u003eThe release of small amounts of K\u003csup\u003e+\u003c/sup\u003e, Na\u003csup\u003e+\u003c/sup\u003e, Mg\u003csup\u003e2+\u003c/sup\u003e, and large amounts of Ca\u003csup\u003e2+\u003c/sup\u003e from the solution before and after the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e by the \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples is shown in Table S2, suggesting that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray was more favorable for Ca\u003csup\u003e2+\u003c/sup\u003e release from the cell wall of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass samples (Fan et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e), resulting in enhanced ion exchange between Pb\u003csup\u003e2+\u003c/sup\u003e and Ca\u003csup\u003e2+\u003c/sup\u003e (Gao et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eAfter Pb\u003csup\u003e2+\u003c/sup\u003e adsorption, the 3D-EEM fluorescence spectra of the DOM released from the \u003cem\u003eC. rupestris\u003c/em\u003e biomass decreased drastically, indicating that \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray caused \u0026pi;-electron mobility on the aromatic carbon \u0026ldquo;core\u0026rdquo; and enhanced the conjugated unsaturated structure (Fig. S4) (Qu et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e). In Fig. S1b, the disappearance of the two shoulder peaks suggests the binding of Pb\u003csup\u003e2+\u003c/sup\u003e and the DOM. In the wavelength range\u0026thinsp;\u0026gt;\u0026thinsp;390 nm, the absorption spectra of DOM showed almost no change, suggesting that intermolecular reaction and the molecular structure did not play a significant role in the binding of Pb\u003csup\u003e2+\u003c/sup\u003e and the DOM due to \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray (Yan et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e). Therefore, the binding of Pb\u003csup\u003e2+\u003c/sup\u003e and the DOM was mainly due to the interaction of the carboxylate chromophores with \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray (Teng et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray caused the successive decomposition and transformation of the DOM of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass, and the carboxy chromophore played an important role in the reaction with Pb\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eIn conclusion, \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation causes \u003cem\u003eC. rupestri\u003c/em\u003es biomass to be dearomatized, which exposes more unsaturated carbon\u003cstrong\u003e-\u003c/strong\u003ebinding sites for Pb\u003csup\u003e2+\u003c/sup\u003e adsorption, while \u003cem\u003eC. rupestris\u003c/em\u003e biomass treated with a high \u003csup\u003e60\u003c/sup\u003eCo\u0026gamma;-ray irradiation dose contain more OFGs and ion\u003cstrong\u003e-\u003c/strong\u003eexchange sites, which provide more active adsorption sites for Pb\u003csup\u003e2+\u003c/sup\u003e (Li et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003e(1) \u003csup\u003e60\u003c/sup\u003eCoγ-ray significantly changed the surface characteristics and interfacial chemistry of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass, causing fracturing and fragmentation, producing a larger specific surface area and more abundant pore structure, and increasing the electronegativity.\u003c/p\u003e \u003cp\u003e(2) The theoretical Pb\u003csup\u003e2+\u003c/sup\u003e Qm of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass increased significantly (2.6\u0026ndash;2.9 times) after \u003csup\u003e60\u003c/sup\u003eCoγ-ray irradiation. \u003csup\u003e60\u003c/sup\u003eCoγ-ray irradiation can activate the relevant adsorption sites and increase the Pb\u003csup\u003e2+\u003c/sup\u003e affinity of \u003cem\u003eC. rupestris\u003c/em\u003e biomass.\u003c/p\u003e \u003cp\u003e(3) \u003csup\u003e60\u003c/sup\u003eCoγ-ray caused preferential degradation of protein components in the DOM of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass, and protein deamination increased the absorption sites of cations.\u003c/p\u003e \u003cp\u003e(4) \u003csup\u003e60\u003c/sup\u003eCoγ-ray altered the elemental composition and functional groups of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass, especially the carbon-containing functional groups and OFGs. \u003csup\u003e60\u003c/sup\u003eCoγ-ray irradiation activated the OFGs of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass, promoting the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e(5) \u003csup\u003e60\u003c/sup\u003eCoγ-ray irradiation produced a high degree of dearomatization, which exposed more unsaturated carbon-binding adsorption sites for Pb\u003csup\u003e2+\u003c/sup\u003e. The \u003cem\u003eC. rupestris\u003c/em\u003e biomass treated with a high \u003csup\u003e60\u003c/sup\u003eCoγ-ray irradiation dose of 200 kGy contained more OFGs and ion-exchange sites, which provided more active Pb\u003csup\u003e2+\u003c/sup\u003e adsorption sites.\u003c/p\u003e \u003cp\u003eThese findings indicate that irradiation of \u003csup\u003e60\u003c/sup\u003eCoγ-ray is an efficient technique for improving the Pb\u003csup\u003e2+\u003c/sup\u003e adsorption of \u003cem\u003eC. rupestris\u003c/em\u003e biomass, aiding in enhanced removal of HMs from waterbodies.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical Approval\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe consent to participate this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe consent to publish this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLu-sheng Zhang: Methodology, Writing - original draft, Investigation. Zhao-wen Liu and Chang-fa Qiu: Software, Formal analysis. Xiao-yu Feng: Conceptualization, Software. Shi-ying Ma and Qian Yin: Visualization, Conceptualization. De-ju Cao: Resources, Writing - review \u0026amp; editing, Supervision, Data curation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Natural\u0026nbsp;Science\u0026nbsp;Foundation\u0026nbsp;of China (41877418) and the financial aid of Nature Fund of Anhui Province of China (1808085MD100).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe declared that the data and materials presented in this paper are reliable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCai T, Liu X, Zhang J, Tie B, Lei M, Wei X, Peng O, Du H (2021) Silicate-modified oiltea camellia shell-derived biochar: A novel and cost-effective sorbent for cadmium removal. 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Am J Bot 99:1541\u0026ndash;1552. https://doi.org/10.3732/ajb.1200161. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"60Coγ-ray, C. rupestris, Pb2+, Adsorption, Functional groups, Remediation potential","lastPublishedDoi":"10.21203/rs.3.rs-5103068/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5103068/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTo investigate the modification of Pb\u003csup\u003e2+\u003c/sup\u003e adsorption of the functional groups of \u003cem\u003eCladophora rupestris \u003c/em\u003e(\u003cem\u003eC. rupestris\u003c/em\u003e) biomass by gamma radiation (\u003csup\u003e60\u003c/sup\u003eCoγ-ray), the interface structure, chemical properties, adsorption behaviors, and Pb\u003csup\u003e2+\u003c/sup\u003e adsorption mechanisms of \u003cem\u003eC. rupestris\u003c/em\u003e biomass were investigated after irradiation with varying doses of \u003csup\u003e60\u003c/sup\u003eCoγ-ray. The results indicate that \u003csup\u003e60\u003c/sup\u003eCoγ-ray significantly changed the surface characteristics and interfacial chemistry of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass .This led to fracturing and fragmentation that produced a larger specific surface area and more abundant pore structure, increasing the electronegativity in the \u003cem\u003eC. rupestris\u003c/em\u003e biomass. The theoretical Pb\u003csup\u003e2+\u003c/sup\u003e adsorption capacity increased significantly (2.6–2.9 times) after \u003csup\u003e60\u003c/sup\u003eCoγ-ray irradiation. \u003csup\u003e60\u003c/sup\u003eCoγ-ray caused preferential degradation of protein components in the dissolved organic matter of the \u003cem\u003eC. rupestris\u003c/em\u003e biomass, and protein deamination increased the absorption sites of cations. In the \u003cem\u003eC. rupestris\u003c/em\u003e biomass, \u003csup\u003e60\u003c/sup\u003eCoγ-ray altered the elemental composition and functional groups, particularly the carbon- and oxygen-containing functional groups, to improve Pb\u003csup\u003e2+\u003c/sup\u003e adsorption. In conclusion, \u003csup\u003e60\u003c/sup\u003eCoγ-ray can activate the functional groups of\u003cem\u003e C. rupestris\u003c/em\u003e biomass and improve their Pb\u003csup\u003e2+\u003c/sup\u003e adsorption sites. This study provides new insight into modification of biomass materials for enhanced removal of heavy metals from waterbodies.\u003c/p\u003e","manuscriptTitle":"60Coγ activation of Cladophora rupestris biomass functional groups and its effect on Pb2+ adsorption","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-04 11:49:41","doi":"10.21203/rs.3.rs-5103068/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Accept","date":"2024-12-12T14:15:14+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-12-04T05:25:10+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-11-28T10:30:46+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2024-11-28T04:26:56+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2024-11-27T09:50:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"a44103ca-04a5-43ae-a920-a138d522ca8b","owner":[],"postedDate":"December 4th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-12-30T16:05:09+00:00","versionOfRecord":{"articleIdentity":"rs-5103068","link":"https://doi.org/10.1007/s11356-024-35802-5","journal":{"identity":"environmental-science-and-pollution-research","isVorOnly":false,"title":"Environmental Science and Pollution Research"},"publishedOn":"2024-12-26 15:57:35","publishedOnDateReadable":"December 26th, 2024"},"versionCreatedAt":"2024-12-04 11:49:41","video":"","vorDoi":"10.1007/s11356-024-35802-5","vorDoiUrl":"https://doi.org/10.1007/s11356-024-35802-5","workflowStages":[]},"version":"v1","identity":"rs-5103068","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5103068","identity":"rs-5103068","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}