Hierarchical Aramid Nanofibers/Carbon Nanotubes Composite Aerogel Engineered for High-Efficiency Tetracycline Hydrochloride Removal

Hierarchical Aramid Nanofibers/Carbon Nanotubes Composite Aerogel Engineered for High-Efficiency Tetracycline Hydrochloride Removal | 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 Hierarchical Aramid Nanofibers/Carbon Nanotubes Composite Aerogel Engineered for High-Efficiency Tetracycline Hydrochloride Removal Li Hua, Linfeng Li, Yu Chen, Gaofan Dai This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6849815/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract To address the growing concern over tetracycline (TCH) pollution in aquatic systems, this study employed high-temperature, corrosion-resistant, and acid-base-resistant aramid nanofibers (ANF) as the substrate material. By integrating physical cross-linking combined with π-π conjugation, ANFs/CNT aerogels were prepared using sol-gel and freeze-drying methods with cost-effective and chemically stable multi-walled carbon nanotubes (CNT). The optimized composite, Ca@ANFs/CNT, was identified through systematic optimization of solid-phase ratios and salt solution coagulation baths. Critical environmental parameters governing TCH removal by Ca@ANFs/CNT were investigated. Experimental results demonstrated that Ca@ANFs/CNT attained a 94.6% TCH elimination efficiency for 20 mg/L TCH solution under ambient conditions, coupled with a maximum adsorption capacity of 104.18 mg/g. The material maintained superior stability and efficiency across a wide pH range of 5 ~ 11, exhibiting resilience against interference from ubiquitous anions (Cl⁻, SO₄²⁻) in water had minimal impact on its performance. Notably,‌ ‌elevated CO₃²⁻ concentrations and humic acid reduced reaction efficiency due to competitive adsorption and pH changes. Combined Kinetic and thermodynamic modeling established chemical adsorption as the rate-limiting mechanism. Characterization techniques such as FT-IR, XPS, and SEM elucidated that Ca²⁺ mediated chelation is the cornerstone of TCH sequestration, augmented by synergistic contributions from electrostatic attraction, hydrogen bonding, and π-π conjugation effects. Additionally, the material’s pore structure contributed to adsorption. This study advances the rational design of antibiotic-capturing materials by unraveling structure-function relationships ‌while demonstrating Ca@ANFs/CNT’s practical viability for real-world water purification.‌ These findings establish a paradigm for developing multifunctional adsorbents targeting emerging contaminants in aquatic systems. Aramid nanofibers Carbon nanotubes Adsorption mechanism Aerogel Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 1 Introduction The burgeoning growth of pharmaceutical, agribusiness, and aquaculture sectors has precipitated severe ecological crises through indiscriminate antibiotic deployment, now recognized as a critical global sustainability challenge. Tetracycline hydrochloride (TCH), a cost-effective broad-spectrum bacteriostatic, dominates agricultural and veterinary applications due to its potent bacteriostatic activity and chemical stability [ 1 , 2 ] . However, its environmental persistence enables ‌multimedia migration‌ across atmospheric, aquatic, and terrestrial compartments, ‌disrupting biogeochemical cycles and threatening ecosystem integrity.‌ To enhance pollutant removal efficiency, understanding existing methods and their mechanisms is essential. Current treatment technologies, biological methods, physical methods, chemical methods, and advanced oxidation processes, face inherent limitations including narrow adsorption selectivity, prohibitive operational costs, and inadequate recoverability [3] . This technological gap has driven‌ innovation in ‌nanostructured adsorbents,‌ with aerogels emerging as ‌frontier materials‌ due to their ‌three-dimensional hierarchical porous architecture‌ and ‌tailorable surface chemistry [4] . Among these, aramid nanofibers (ANF) -based aerogels stand out‌ by inheriting the ‌exceptional mechanical robustness (> 500°C thermal stability) and chemical inertness‌ of poly (para phenylene terephthalamide) (PPTA) fibers [5] . Aramid nanofiber aerogels (ANFs) combine the advantages of high-performance aramid and nanofibers, serving as excellent nano-construction units and filler materials. Their superior properties have led to widespread applications in electrical insulation, lightweight structural materials, and flexible sensing. For example, Xu et al. [6] mass-produced aramid nanofiber aerogel microspheres (ANFAMs) with dense skin and porous internal structures via wet-spinning technology, achieving effective removal of organic dyes in harsh chemical environments. Wang et al. [7] prepared honeycomb-like carboxylated multi-walled carbon nanotube/aramid nanofiber aerogels through sol-gel, unidirectional freezing, and freeze-drying, demonstrating promising electromagnetic wave absorption and thermal insulation properties. Carbon nanotubes (CNT), tubular nanomaterials composed of carbon atoms, possess unique structures and excellent physicochemical properties. Multi-walled carbon nanotubes (MWCNT), in particular, have been widely studied due to their low cost, simple preparation, and stability, achieving significant results in electronics, catalysis, sensors, and energy storage. For instance, Wu et al. [ 8 ] developed a sensitive electrochemical sensor using ferrocene-covalently linked gold nanoparticles on MWCNT to enhance serotonin detection. Wang et al. [ 9 ] coated magnetic nanoparticles on MWCNT to prepare magnetic MWCNT with abundant surface active sites, effectively treating Cr-containing heavy metal wastewater. Capitalizing on these synergies,‌ we engineered an ‌ANFs/MWCNTs composite aerogel‌ through π–π stacking-assisted physical cross-linking, integrating sol-gel and freeze-drying methods, enhancing corrosion and acid-base resistance while increasing specific surface area and adsorption capacity. This study not only optimizes material performance but also deciphers the ‌chelation-dominated removal mechanisms, offering insights for next-generation antibiotic capture technologies. 2 Experimental 2.1 Materials Dimethyl sulfoxide (DMSO) was purchased from Chengdu Kelong Chemical Reagent Co., Ltd., China; potassium hydroxide (KOH) and potassium chloride (KCl) from Tianjin Damao Chemical Reagent Co., Ltd., China; calcium sulfate (CaSO₄) from Tianjin Fuchen Chemical Reagent Co., Ltd., China; sodium chloride (NaCl), anhydrous calcium chloride (CaCl₂), calcium carbonate (CaCO₃), and absolute ethanol (CH₃CH₂OH) from Sinopharm Chemical Reagent Co., Ltd., China; anhydrous magnesium chloride (MgCl₂) and tetracycline hydrochloride (TCH, 99%) from Shanghai Macklin Biochemical Technology Co., Ltd., China; methanol (CH₃OH), acetonitrile (CH₃CN), and formic acid (HCOOH) from Tianjin Kemiou Chemical Reagent Co., Ltd., China; humic acid (HA) from Shanghai Aladdin Reagent Co., Ltd., China. All reagents and chemicals were used as received without further purification. Deionized water was provided by a laboratory water purifier. 2.2 Preparation of ANFs aerogel The ANFs dispersion was prepared using the deprotonation and alkali dissolution methods. Ten grams of Kevlar short-cut fibers and an equal mass of KOH were added to a flask, followed by DMSO (dewatered), and stirred under nitrogen protection for 7 days to obtain a 2 wt% solution. ANFs dispersion. Similarly, ANFs dispersions with solid contents of 0.5 wt.%, 1 wt.%, and 1.5 wt.% were prepared. Seventy-five milliliters of the dispersion were mixed with 500 mL of deionized water to initiate gelation. After complete gelation, the gel was broken, sieved through a 2300-mesh sieve, and washed with water for 24 h to remove residual solvents. The gel was aged, loaded into a mold, pre-frozen at -20°C for 12 h to form a cryogel, and then freeze-dried for 48 h to obtain ANFs aerogel. 2.3 Preparation of ANFs/CNT aerogel with different coagulation baths The ANFs/CNT dispersion was synthesized via physical cross-linking: CNT (1.38 g) and KOH (1.38 g) were dissolved in DMSO (100 mL) under 48 h stirring, then blended with 2 wt.% ANFs dispersion (100 mL) under nitrogen for 5 days. Varying carbon content dispersions (0.2–0.8 wt.%) were prepared analogously. Its preparation process is shown in Fig. 1 . For gelation, 75 mL ANFs/CNT dispersion was injected into a 5 mM CaCl₂ bath (500 mL). The resultant gel was homogenized, sieved (2300-mesh), and washed with CaCl₂ solution. Subsequent processing followed Section 2.2 (ANFs aerogel protocol), yielding Ca@ANFs/CNT. Control aerogels were designated as: Water type variants: DI@ANFs (deionized), RO@ANFs (reverse osmosis), Tw@ANFs (tap), Pw@ANFs (purified). Salt-coagulated variants (5 mM): Ca@ANFs/CNT, Na@ANFs/CNT (NaCl), K@ANFs/CNT (KCl), Mg@ANFs/CNT (MgCl₂) 2.4 Investigation of the effects of preparation conditions on aerogel adsorption performance 2.4.1 Effect of coagulation bath on adsorption performance Thirty milligrams of DI@ANFs, RO@ANFs, Tw@ANFs, and Pw@ANFs aerogels were added to 50 mL of 20 mg/L TCH solution, respectively. Samples were taken at different time points to measure TCH concentration. The adsorption performance of each material for TCH was compared to screen the optimal water-based coagulation bath. 2.4.2 Effect of ANFs and CNT solid content on adsorption performance The experimental materials were replaced with ANFs aerogels with solid contents of 0.5 wt.%, 1 wt.%, and 1.5 wt.% or ANFs/CNT aerogels with carbon contents of 0.2 wt.%, 0.5 wt.%, and 0.8 wt.%, the other steps were the same as in 2.4.1. 2.4.3 Effect of different salt solution coagulation baths on adsorption performance The experimental materials were replaced with Ca@ANFs/CNT, Na@ANFs/CNT, K@ANFs/CNT, and Mg@ANFs/CNT, and the experimental steps were the same as in 2.4.1. 2.5 Material Characterization SEM analysis was performed using a field-emission microscope after gold sputter-coating of dried aerogel samples. XRD patterns of modified biochar were obtained with a Bruker D8 Advance diffractometer (Cu-Kα radiation), with crystallinity analysis via Jade software. Surface area and porosity were determined by nitrogen adsorption-desorption using a Micromeritics ASAP 2460 system. FTIR spectra (400–4000 cm⁻¹) were acquired through the KBr pellet method with a Nicolet iS20 spectrometer. XPS surface analysis was conducted on an ESCALAB Xi + system, with elemental quantification performed using Avantage software. 2.6 Effect of process parameters on TCH removal efficiency by ANF-based aerogels 2.6.1 Effect of M@ANFs/CNT dosage on TCH removal To investigate the TCH removal efficiency of Ca@ANFs/CNT under various solid-liquid ratios, experiments were conducted with a TCH concentration of 20 mg/L, a reaction volume of 50 mL, and Ca@ANFs/CNT dosages of 0.1, 0.2, 0.4, 0.6, and 1.0 g/L. Other conditions were kept constant (room temperature 25°C, rotation speed 200 rpm). Samples were taken at 3, 5, 15, 30, 60, 90, 120, 180, and 240 min, filtered through a 0.22 µm organic filter into 2 mL HPLC vials, and TCH concentration was measured by HPLC. 2.6.2 Effect of initial TCH concentration on TCH removal To study the TCH removal efficiency of Ca@ANFs/CNT at different initial TCH concentrations, the initial TCH concentrations were set to 5, 10, 20, 40, and 60 mg/L, with a reaction volume of 50 mL and a Ca@ANFs/CNT dosage of 0.6 g/L. Other experimental steps were the same as in 2.6.1. 2.6.3 Effect of pH on TCH removal The effect of initial pH (3, 5, 7, 9, 11) on TCH removal by Ca@ANFs/CNT was studied. Other conditions were kept constant (room temperature 25°C, Ca@ANFs/CNT 0.6 g/L, rotation speed 150 rpm), and samples were taken at the time points described in 2.6.1 to measure TCH concentration. 2.6.4 Effect of exogenous ions and humic acid on TCH removal. Effect of anions: different concentrations (0.5, 1, 5, 10 mM) of NaCl, NaHCO₃, Na₂CO₃, and Na₂SO₄ were added, and other conditions were kept constant (reaction volume 50 mL, material dosage 0.6 g/L, TCH concentration 20 mg/L, room temperature 25°C). Samples were taken at the same time with 2.6.1 to measure TCH concentration. Effect of cations: 0.5 mM CaCl₂, NaCl, KCl, MgCl₂, and CuCl₂·2H₂O were added to the reaction solution to investigate their effects on TCH removal by Ca@ANFs/CNT. Other conditions were unchanged, and samples were taken at the time points in 2.6.1 for measurement. Effect of humic acid (HA): Different concentrations (10, 20, 40, 100 mg/L) of HA were added to the system, and other conditions were kept constant. Samples were taken at the time points in 2.6.1 to measure TCH concentration. 3 Results and discussion 3.1 Screening and optimization of aerogel materials 3.1.1 Effect of different aerogels on adsorption performance The ionic composition of coagulation baths containing varying anionic and cationic species was found to potentially influence the physicochemical characteristics of aerogels during the gelation process. Comparative adsorption experiments revealed that DI@ANFs, RO@ANFs, and Pw@ANFs had comparable TCH adsorption capacities within 240 min (Fig. 2 a), whereas Tw@ANFs demonstrated significantly enhanced performance, achieving 83.73% TCH removal within 90 min under the identical experimental conditions. Based on this marked efficiency improvement, tap water was selected as the coagulation medium for subsequent optimization of ANF/CNT composite formulations. The solid content of aramid fibers is a key factor determining the structural density and performance characteristics of the aerogel materials. When the solid content was 1 wt.%, the ANFs material exhibited superior TCH sequestration capability, achieving 91.51% removal efficiency (Fig. 2 b). Therefore, 1 wt.% ANFs were used as the base material for the subsequent screening of different carbon nanotube contents. Further verification of the TCH removal efficiency of ANFs/CNT with different carbon contents showed that the 0.5 wt.% ANFs/CNT material still outperformed other carbon contents, achieving adsorption equilibrium within 8 h and removing 63.58% of TCH, with an adsorption capacity of 169.91 mg/g (Fig. 2 c). When the CNT content in the material increased further, the TCH removal efficiency of ANFs/CNT decreased to some extent. Integrating performance metrics with cost-effectiveness considerations, the optimal CNT loading was strategically fixed at 0.5 wt.% for all downstream composite fabrication processes. The TCH removal efficiency of materials with different salt solution coagulation baths was investigated. Results showed that Ca@ANFs/CNT prepared with 1 mM CaCl₂ solution as the coagulation bath achieved 83.5% TCH elimination within 90 min, higher than K@ANFs/CNT, Na@ANFs/CNT, Mg@ANFs/CNT, and DI@ANFs/CNT(Fig. 3 a). Notably, when increasing the salt solution concentration to 5 mM, Ca@ANFs/CNT still maintained superiority in contaminant removal(Fig. 3 b). 3.1.2 Characterization of ANFs/CNT materials prepared with different coagulation baths Scanning electron microscopy (SEM) analysis revealed morphological differences in aerogels prepared with different metal salts (Figs. 4 ). Na⁺- and K⁺-based systems (Na@ANFs/CNT, K@ANFs/CNT) retained three-dimensional (3D) porous networks; however, energy-dispersive X-ray spectroscopy (EDS) indicated low-density distribution of Na/K elements (Figs. 4 a 4 /c 4 ) with localized agglomeration. In contrast, Mg²⁺-incorporated aerogels (Mg@ANFs/CNT) exhibited uniformly aligned needle-like MgO crystals on their surfaces (Figs. 4 b 1 -b 3 ). The growth of these crystals induced partial structural collapse, significantly reducing porosity and specific surface area. Notably, despite the homogeneous distribution of Mg, irreversible structural damage occurred due to stress interactions between the crystals and the framework. The Ca²⁺-incorporated system (Ca@ANFs/CNT) displayed a distinctive layered-curling morphology (Fig. 5a 1 ), attributed to an interpenetrating network formed via π-π stacking and hydrogen bonding between CNTs and ANFs. Pore reconstruction during freeze-drying (Figs. 5a 2 -a 3 ) endowed the material with high porosity (> 90%) and interconnected mesopores (2–50 nm), providing abundant adsorption sites. EDS analysis (Fig. 5 b) confirmed its composition: C/N/O dominated (> 85 wt.%), consistent with ANF/CNT components, while trace S (0.7 wt.%) and Cl (1.2 wt.%) originated from DMSO residues and ion exchange. Ca²⁺ was uniformly distributed (8.22 wt.%, CV < 5%), demonstrating stable anchoring via anion exchange. This structure-composition correlation elucidates the superior adsorption performance of the Ca²⁺ system. Figure 6 presents comparative XRD and FTIR analyses of the crystal structures of DI@ANFs/CNT and Ca@ANFs/CNT. XRD patterns (Fig. 6 a) reveal analogous crystalline phases in both materials, with retained diffraction peaks at (110), (200), and (004) planes characteristic of aramid nanofibers. Notably, the (004) plane diffraction in Ca@ANFs/CNT exhibits peak overlap due to epitaxial growth of CaCO₃ crystals, confirming carbonate phase coexistence (PDF#05-0586) [ 10 ] . Both materials show the (002) crystal plane corresponding to carbon nanotube crystals, confirming that carbon nanotubes are loaded onto the surface of aramid fibers via π-π conjugation. The FTIR spectrum in Fig. 6 b identifies critical functional groups and bonding interactions within the materials. The characteristic N-H stretching vibration of aramid fibers appears at 3420 cm⁻¹, while the bands at 1600 cm⁻¹ and 1355 cm⁻¹ are ascribed to C = O stretching and C-H bending modes in PPTA, respectively. Notably, Ca@ANFs/CNT exhibits a slight redshift and diminished intensity in these peaks, attributed to hydrogen-bond reorganization between amino and hydroxyl groups within its framework [ 11 ] . The characteristic band vibration at 770 cm⁻¹ is attributed to the asymmetric stretching vibration of the C-H group and the characteristic band vibration at 1310 cm⁻¹ is considered the unique Ph-N vibration of PPTA, confirming that the matrix of both fiber materials is ANF [ 12 ] . The characteristic band vibration at 1410 cm⁻¹ in Ca@ANFs/CNT is the vibration of nano-calcium carbonate, indicating that part of the calcium carbonate is loaded on the material surface via anion exchange [ 13 ] . Furthermore, weak absorptions at 1110 cm⁻¹ (Ca-O lattice vibration) and 1020 cm⁻¹ (Ca-OH bending) provide conclusive evidence for the successful incorporation of calcium species [ 14 ] . 3.2 Effects of different process conditions on the adsorption performance of Ca@ANFs/CNT 3.2.1 Effect of Ca@ANFs/CNT dosage on the adsorption performance The dosage of the material is a critical factor in maintaining the reaction equilibrium in the system, often determining the number of reactive sites [ 15 ] . Figure 7 a shows the TCH removal efficiency of Ca@ANFs/CNT at different dosages for a 20 mg/L TCH solution. As shown in Fig. 7 a, the TCH removal efficiency at 20 mg/L initial concentration exhibits a strong dependence on adsorbent dosage. Increasing the dosage to 0.4 g/L significantly enhanced removal efficiency, 82.80% at 120 min equilibrium, reflecting improved site accessibility. Further dosage escalation to 0.6 g/L and 1 g/L yielded near-saturation performance, indicating site abundance. Beyond 0.6 g/L, minimal efficiency gains were observed, suggesting surface saturation. Balancing cost-effectiveness, adsorption capacity, and practical feasibility, the optimal dosage was determined as 0.6 g/L for subsequent studies. 3.2.2 Effect of initial TCH concentration on adsorption performance As shown in Fig. 7 b, Ca@ANFs/CNT demonstrated good removal efficiency for 5, 10, and 20 mg/L TCH solutions, with rapid TCH concentration decline within the first 30 min, followed by slow equilibrium, and removal efficiency of 88.62%, 92.45%, and 92.56%, respectively. When the TCH concentration increased to 40 mg/L and 60 mg/L, the equilibrium time was significantly prolonged, and the removal efficiency decreased, with 83.29% and 78.57% TCH removed within 240 min. However, as the TCH concentration increased from 5 mg/L to 60 mg/L, the adsorption capacity of Ca@ANFs/CNT for TCH increased from 7.33 mg/g to 80.14 mg/g, indicating that higher TCH concentrations enhance the driving force for removal, promoting TCH migration from the solution to the adsorbent surface. However, excessively high TCH concentrations may lead to limited adsorption sites, reducing the removal efficiency. In actual water bodies, tetracycline concentrations vary across different water environments. Studies have found that residual TCH concentrations in some water media in China generally range from ng/L to µg/L [ 16 , 17 ] , but in some areas with heavy antibiotic use, TCH concentrations in livestock wastewater and medical wastewater can reach the mg/L level, typically not exceeding 5 mg/L [ 18 ] . Therefore, the results of this study provide valuable guidance for TCH removal in real aquatic systems. 3.2.3 Effect of initial pH on adsorption performance The initial pH of the solution can affect the charge properties of the material surface and the form of pollutants during organic contaminant removal [ 19 ] . The unique structure of TCH molecules causes them to ionize into different ionic states (TCH³⁺, TCH²⁺, TCH⁻, TC²⁻) under different pH conditions. The pKa values of TCH are pKa 1 = 3.30, pKa 2 = 7.6, and pKa 3 = 9.27. Below pH 3.3, TCH exists as H₃TC⁺; between 3.3 and 7.6, as HTC⁰; between 7.6 and 9.27, as HTC⁻; and above 9.27, as TC²⁻ [ 20 ] . Therefore, Ca@ANFs/CNT exhibits different TCH removal efficiencies at different pH values. As shown in Fig. 7 c, the material showed good TCH removal performance at pH 5 ~ 11, achieving adsorption equilibrium within approximately 90 min with removal rates above 90%. As pH increased from 5 to 11, the TCH removal capacity increased slightly, likely because TCH molecules gradually deprotonate acidic functional groups with increasing pH, transforming from HTC⁰ to negatively charged HTC⁻ and TC²⁻, while the Ca@ANFs/CNT surface carries positive charges, enhancing electrostatic attraction and removal efficiency. At pH = 3 (acidic conditions), TCH deprotonates basic functional groups to exist as H₃TC⁺, repelling the positive charges on the Ca@ANFs/CNT surface, enhancing electrostatic repulsion, and inhibiting complexation, resulting in significantly reduced removal efficiency (76.80% TCH removed within 240 min). Since the TCH solution is weakly acidic (pH ≈ 6), no buffer was used to adjust the pH in subsequent experiments. 3.3 Effects of different ions and humic acid on TCH adsorption by Ca@ANFs/CNT 3.3.1 Effect of anions on adsorption performance Natural aquatic systems typically contain diverse anion species, with Cl⁻, HCO₃⁻, CO₃²⁻, and SO₄²⁻ being particularly prevalent constituents that may exert significant influences on the reaction system. As shown in Fig. 8 a, increasing the SO₄²⁻ concentration from 0.5 mM to 10 mM had little effect on TCH removal efficiency by Ca@ANFs/CNT, with approximately 92% TCH removed within 240 min in both the presence and absence of SO₄²⁻, indicating that SO₄²⁻ does not interfere with TCH removal by Ca@ANFs/CNT. In contrast, CO₃²⁻ significantly reduced TCH removal efficiency (Fig. 8 c). The TCH removal efficiency exhibited an inverse correlation with CO₃²⁻ concentration, declining from 89.40% at 1 mM to 58.97% at 10 mM, representing a reduction of approximately 30%. This effect could be attributed to excessive CO₃²⁻ binding with Ca²⁺ on the material surface to form CaCO₃ precipitates, increasing solution mineralization, and CO₃²⁻ competing with TC for adsorption sites on the material surface. Additionally, studies have shown that CO₃²⁻ can shield ·OH under light, inhibiting natural photolysis, thus reducing removal efficiency in the reaction system. HCO₃⁻ showed weak inhibitory effects at low to moderate concentrations, with the removal efficiency decreasing from 92.76–86.65% at high concentrations, possibly due to partial hydrolysis of HCO₃⁻ to form a small amount of CO₃²⁻, leading to reduced efficiency. As a common ion in water, Cl⁻ had little effect on TCH removal, with a removal efficiency of around 90% at both low and high concentrations, similar to the ion-free control. 3.3.2 Effect of cations and humic acid on adsorption performance Tetracycline-containing wastewater, as a refractory organic wastewater, typically contains various cations. Notably, certain light metal ions may compete with tetracycline molecules for adsorption sites. As shown in Fig. 9 a, K⁺, Ca²⁺, Na⁺, and Mg²⁺ had weak effects on the system, with reaction trends and final removal rates similar to the ion-free control, all removing approximately 90% of TCH, indicating that 0.5 mM of these cations exhibit little competitive adsorption with tetracycline hydrochloride and do not significantly affect TCH removal. However, the presence of 0.5 mM Cu²⁺ caused the reaction system to achieve nearly 100% TCH removal within 30 min, possibly because copper, as a transition metal, provides efficient and selective removal capabilities, enhancing antibiotic removal [ 21 ] . Humic acid, a common organic matter in nature, is widely present in natural aquatic systems and polluted wastewater, affecting the removal of organic substances [ 22 ] . At 40 mg/L HA, the material still removed 90% of TCH, but at 100 mg/L HA, the inhibition significantly increased, with the TCH removal rate dropping to 81.61% within 240 min (Fig. 9 b). The observed phenomenon primarily stems from HA-induced pH depression. Specifically, when solution pH is reduced below 3.3 by elevated HA concentrations, TCH predominantly exists in H₃TC⁺ form, leading to two concurrent effects: enhancing electrostatic repulsion and reducing reaction efficiency. 3.4 Characterization of Ca@ANFs/CNT before and after TCH adsorption Figure 10 presents comparative SEM microstructural analyses of Ca@ANFs/CNT in pre-adsorption and post-adsorption states following TCH exposure. Figure 10 a–b are pre-adsorption surface morphologies, and Fig. 10 c–d are post-adsorption morphologies. After adsorption, the curling structure on the Ca@ANFs/CNT surface became more pronounced, and the three-dimensional network structure became looser. This is because the reaction solution was continuously stirred to ensure uniform contact between the material and TCH molecules, causing the aerogel to disperse evenly in the liquid due to centrifugal force, thus efficiently removing pollutants. FT-IR spectra (Fig. 11 a) show that the peaks at 3440 cm⁻¹ and 1637 cm⁻¹ correspond to the N-H stretching vibration and C = O stretching vibration of PPTA fibers, respectively. After the reaction with TCH, the intensity of the N-H stretching vibration peak at 3440 cm⁻¹ decreased significantly, and the C = O stretching vibration peak at 1637 cm⁻¹ shifted to 1663 cm⁻¹, indicating that the carbonyl and amino groups of the material participated in TCH adsorption via hydrogen bonding [ 23 ] . The enhanced peak at 1520 cm⁻¹ after reaction corresponds to the carbonyl skeleton stretching vibration peak of TCH molecules, further confirming TCH capture by Ca@ANFs/CNT. The Ca-O stretching vibration peak at 825 cm⁻¹ shifted to 810 cm⁻¹ after the reaction, suggesting that calcium ions on the material surface formed Ca-TC complexes with hydroxyl and carbonyl groups on tetracycline via complexation [ 24 ] . Additionally, changes in the displacement and intensity of the C-H stretching vibration peak of natural TC after reaction further indicate that TCH was immobilized on the Ca@ANFs/CNT surface via electrostatic attraction and hydrogen bonding [ 25 ] . XRD analysis of crystal morphology in pre-adsorption and post-adsorption states (Fig. 11 b) showed a distinct CaCO₃ crystal diffraction peak at 29.4° (corresponding to PDF #05-0586), which weakened significantly after reaction with TCH, further confirming that Ca²⁺ participated in TCH adsorption. To elucidate the adsorption mechanisms, X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical composition and electronic states of surface elements (C, O, Ca) in Ca@ANFs/CNT composites before and after TCH adsorption, with spectral deconvolution analysis conducted using Thermo Scientific Avantage software (Fig. 12 ). Figures 12 a–b shows the C 1s spectra before and after adsorption. Peaks at 284.8 eV and 288.1 eV correspond to C-C and O-C = O bonds in the material, respectively. After TCH adsorption, the intensities of both peaks decreased, and the O-C = O peak shifted slightly to 288.0 eV, likely due to the dissociation of carboxyl groups via hydrogen bonding and their binding with TCH molecules. The C-O-C bond at 285.58 eV shifted to 285.5 eV, and its peak area increased from 15.25–38.76%, indicating that TCH molecules bound to oxygen-containing groups on the aerogel surface via hydrogen bonding and electrostatic attraction [ 26 ] . The π-π satellite peak at 290.95 eV showed weak vibration and reduced area after adsorption, suggesting that π-π interactions also contributed to TCH adsorption [ 27 ] . Figures 12 c–d show the O 1s spectra before and after adsorption. The weakening and blue shift of C = O and H-O-C bonds after TC binding further indicate that the material captured TCH molecules by dissociating surface carbonyl and carboxyl groups to form hydrogen bonds with hydroxyl and amino groups on TCH. In the Ca 2p spectrum, peaks at 347.14 eV and 350.64 eV correspond to Ca 2p3/2 and Ca 2p1/2 of CaCO₃, respectively [ 28 ] . After reaction with TCH, their peak areas decreased from 60.71% and 35.66–56.9% and 27.75%, respectively, confirming that Ca²⁺ complexed with TCH molecules to promote TCH removal. Studies have shown that tetracycline dissociates surface carbonyl and hydroxyl groups to complexes with Ca²⁺, and hydroxyl groups on tetracycline dissociate more easily in alkaline environments, thus enhancing complexation [ 29 ] . This ion-complexation mechanism provides a plausible explanation for the observed pH-dependent adsorption efficiency, with optimal TCH removal achieved at elevated pH values. Integrated mechanistic analysis reveals that TCH adsorption by the Ca@ANFs/CNT composite arises from multiple synergistic mechanisms, including complexation, hydrogen bonding, π-π interactions, electrostatic attraction, and pore filling, as shown in Fig. 13 . 4 Conclusion In this study, the Ca@ANFs/CNT material was prepared under optimized conditions, and its performance and mechanism for TCH removal in water were systematically investigated. Experimental results show that Ca@ANFs/CNT exhibits excellent TCH removal efficiency (> 90%) under optimized conditions (dosage of 0.6 g/L, pH > 3.30). Environmental interference assays revealed that high concentrations of CO₃²⁻ (10 mM) significantly inhibit removal efficiency by competing for Ca²⁺, while Cu²⁺ accelerates the reaction via synergistic adsorption pathways, and humic acid inhibits removal efficiency with increasing concentration. This study not only reveals the multi-mechanism adsorption principle of Ca@ANFs/CNT but also provides actionable guidelines for designing cost-effective, multifunctional materials for practical water remediation scenarios involving emerging contaminants. Declarations Declaration of Competing Interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author Contribution Li Hua: Conceptualization, methodology, funding acquisition, writing—original draft, and writing—review & editing. Linfeng Li: Investigation, methodology, data curation. Yu Chen: Methodology, Software. Gaofan Dai: Methodology, Software. Acknowledgements This research was partially supported by the National Natural Science Foundation of China under Grant (22376133) and the Key Research and Development Program in Shaanxi Province (2024PT-ZCK-09) References Gudda F, Odinga E S, Tang L, et al. Tetracyclines uptake from irrigation water by vegetables: Accumulation and antimicrobial resistance risks[J]. Environmental Pollution, 2023, 338, 122696. https://doi.org/10.1016/j.envpol.2023.122696 . Shi M Q, Wang H F, Yuan P Q, et al. Degradation of tetracycline hydrochloride by electrocatalytic oxidation using NiO@Co3O4/Ti electrode[J]. Journal of Water Process Engineering, 2024, 61:105242. https://doi.org/10.1016/j.jwpe.2024.105242 . Vakili M M, Cagnetta H, Deng S B, et al. 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Calcium/iron-layered double hydroxides-sodium alginate for removal of tetracycline antibiotic from aqueous solution[J]. Alexandria Engineering Journal, 2023, 63: 127–142. https://doi.org/10.1016/j.aej.2022.07.055 . Nie Y, Zhao C W, Zhou C Y, et al. Hydrochloric acid-modified fungi-microalgae biochar for adsorption of tetracycline hydrochloride: Performance and mechanism[J]. Bioresource Technology, 2023, 383: 129224. https://doi.org/10.1016/j.biortech.2023.129224 . Danner M C, Robertson A, Behrends V, et al. Antibiotic pollution in surface fresh waters: Occurrence and effects[J]. Science of The Total Environment, 2019, 664: 793–804. https://doi.org/10.1016/j.scitotenv.2019.01.406 . Bai Y, Ruan X, Xie X, et al. Antibiotic resistome profile based on metagenomics in raw surface drinking water source and the influence of environmental factors: A case study in Huaihe River Basin, China[J]. Environ Pollut, 2019, 248: 438–447. https://doi.org/10.1016/j.envpol.2019.02.057 . Lim, S J, Seo C K, Kim T H, et al. Occurrence and ecological hazard assessment of selected veterinary medicines in livestock wastewater treatment plants[J]. Journal of Environmental Science and Health, 2013,48(8): 658–670. https://doi.org/10.1080/03601234.2013.778604 . Zhang Y, Zhang B-T, Teng Y, et al. Heterogeneous activation of persulfate by carbon nanofiber-supported Fe3O4@carbon composites for efficient ibuprofen degradation[J]. Journal of Hazardous Materials, 2021, 401: 123428. https://doi.org/10.1016/j.jhazmat.2020.123428 . Manuel C D,Gustavo F C, Avelino N D, et al. Competitive adsorption of tetracycline, oxytetracycline, and chlortetracycline on soils with different pH values and organic matter content[J]. Environmental Research, 2019, 178: 108669. https://doi.org/10.1016/j.envres.2019.108669 . Zhang P, Liu Q, Yao H D, et al. Copper-functionalized hydrochar from swine manure with complexation sites for selective adsorption of tetracycline antibiotics[J]. Separation and Purification Technology, 2025, 359(3): 130671. https://doi.org/10.1016/j.seppur.2024.130671 . Li Y, Bi E, Chen H. Effects of dissolved humic acid on fluoroquinolones sorption and retention to kaolinite[J]. Ecotoxicology and Environmental Safety, 2019, 178(8): 43–50. https://doi.org/10.1016/j.ecoenv.2019.04.002 . Du G H, Yang Y, Tian L, et al. Fabrication of Fe-based biomass aerogel with microwave assistance and its properties in the removal of tetracycline from wastewater[J]. Journal of Environmental Chemical Engineering, 2024, 12(2): 112343. https://doi.org/10.1016/j.jece.2024.112343 . Yukhajon P, Somboon T, Sansuk S. Enhanced adsorption and colorimetric detection of tetracycline antibiotics by using functional phosphate/carbonate composite with nanoporous network coverage[J]. Journal of Environmental Sciences, 2023, 126: 365–377. https://doi.org/10.1016/j.jes.2022.04.009 . Chen B, Chen Y M, Chen S Y, et al. Iron–calcium dual crosslinked graphene oxide/alginate aerogel microspheres for extraordinary elimination of tetracycline in complex wastewater: Performance, mechanism, and applications[J]. International Journal of Biological Macromolecules, 2024, 264(1): 130554. https://doi.org/10.1016/j.ijbiomac.2024.130554 . Hamid A S, Hamza E, Mohammed L, et al. Development of calcium phosphate-chitosan composites with improved removal capacity toward tetracycline antibiotic: Adsorption and electrokinetic properties[J]. International Journal of Biological Macromolecules, 2024, 257(2): 128610. https://doi.org/10.1016/j.ijbiomac.2023.128610 . Dai Y J, Li J J, Shan D X. Adsorption of tetracycline in aqueous solution by biochar derived from waste Auricularia auricula dregs[J]. Chemosphere, 2020, 238: 124432. https://doi.org/10.1016/j.chemosphere.2019.124432 . Zha Y P, Chen W T, Xu ZQ. Surface Organic Modification of CaCO3-TiO2 Composite Pigment[J]. Minerals, 2019, 9(2): 112231. https://doi.org/10.3390/min9020112 . Wei X X, Zhang R J, Zhang W C, et al. High-efficiency adsorption of tetracycline by the prepared waste collagen fiber-derived porous biochar[J]. Royal Society of Chemistry Advances, 2019, 9(67): 39355. https://doi.org/10.1039/c9ra07289f Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6849815","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":471057447,"identity":"23718711-bf3b-418f-a6f5-1fa6dabbe6be","order_by":0,"name":"Li Hua","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwUlEQVRIiWNgGAWjYBACAwYGxgMJFVAeD5FaGA4knAGSbCRpYWwjRYu5RPKDAw/n1SXOn9/A+OBtG4O8OSEtljPSDA4kbjucuOEYA7Ph3DYGw50NhBx2IwGk5UDiBjYGNmneNgYgl6CW9A8HEucAHdbGwP6bSC05QFsamBMbjjGwMROn5cybggMJxw4bbziW2Cw555yE4QaCWo6nb3z4o6ZOdn7z4YMf3pTZyBO0BQkwNgAJCeLVj4JRMApGwSjADQDDdEUN1sz8QQAAAABJRU5ErkJggg==","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Li","middleName":"","lastName":"Hua","suffix":""},{"id":471057448,"identity":"dbf55f78-1e03-4337-bc7a-5d1d315aa683","order_by":1,"name":"Linfeng Li","email":"","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Linfeng","middleName":"","lastName":"Li","suffix":""},{"id":471057449,"identity":"f3595fb6-68b9-42f9-ad32-f46d598873ca","order_by":2,"name":"Yu Chen","email":"","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yu","middleName":"","lastName":"Chen","suffix":""},{"id":471057451,"identity":"82e5274a-adbc-4f76-9702-8b10c0ff5d78","order_by":3,"name":"Gaofan Dai","email":"","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Gaofan","middleName":"","lastName":"Dai","suffix":""}],"badges":[],"createdAt":"2025-06-09 01:53:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6849815/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6849815/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84703995,"identity":"7c9a6897-ef4b-4c46-bc90-206d8f633765","added_by":"auto","created_at":"2025-06-16 12:03:13","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":3846267,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart for ANFs/CNT preparation\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/a59732528c098995659ed56f.png"},{"id":84703997,"identity":"aa37ebe6-3257-4df0-9b13-1f861d2504b9","added_by":"auto","created_at":"2025-06-16 12:03:13","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":203803,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of ANFs Prepared from Different Water-based Coagulation Baths and the Solid Content of Different Aramid Fibers and Carbon Nanotubes on the Removal of TCH\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/f48aecee3ff885ddb6bc423c.png"},{"id":84705152,"identity":"a0d8ac32-2034-4e11-94b5-9bd274deac80","added_by":"auto","created_at":"2025-06-16 12:11:13","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":107175,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of ANFs/CNT prepared in different calcium salt solution coagulation baths on TCH removal\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/9e11e8bbb063d5d1166d6cf7.png"},{"id":84705155,"identity":"9cc33fb8-2dc4-4460-96a3-58151bc8952a","added_by":"auto","created_at":"2025-06-16 12:11:13","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":6983552,"visible":true,"origin":"","legend":"\u003cp\u003eSEM and partial elemental mapping of aerogels prepared in different solidification baths.（a\u003csub\u003e1\u003c/sub\u003e-a\u003csub\u003e4\u003c/sub\u003e:Na@ANFs/CNT; b\u003csub\u003e1\u003c/sub\u003e-b\u003csub\u003e4\u003c/sub\u003e:Mg@ANFs/CNT; c\u003csub\u003e1\u003c/sub\u003e-c\u003csub\u003e4\u003c/sub\u003e:K@ANFs/CNT）\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/251306b5e7db7dd7a4a08c50.png"},{"id":84704002,"identity":"d87fe91c-08d9-478c-ae88-c09dac514acc","added_by":"auto","created_at":"2025-06-16 12:03:13","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2993341,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images and elemental distribution of Ca@ANFs/CNT at different magnifications\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/c43140b95655efb73acb065e.png"},{"id":84705153,"identity":"f56521bb-54e3-4aa8-bfc0-06bee420bcf4","added_by":"auto","created_at":"2025-06-16 12:11:13","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":219917,"visible":true,"origin":"","legend":"\u003cp\u003eXRD and FTIR spectra of DI@ANFs/CNT and Ca@ANFs/CNT\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/c0941f14249a9eacc684821f.png"},{"id":84704011,"identity":"26c97bb8-0d50-43c9-969a-09a17085d589","added_by":"auto","created_at":"2025-06-16 12:03:13","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":203593,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of different conditions on the adsorption performance of TCH (a: Dosage of Ca@ANFs/CNT; b: Initial concentration of TCH; c: pH value)\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/02fbf9dd50c65536ba6c2e22.png"},{"id":84704007,"identity":"5338a05f-7821-4e3e-90e0-736292e430c2","added_by":"auto","created_at":"2025-06-16 12:03:13","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1493011,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of different anions on the removal of TCH by Ca@ANFs/CNT(a:SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e; b:HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e; c:CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e; d:Cl\u003csup\u003e-\u003c/sup\u003e)\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/c3408b2d85c3310961f88319.png"},{"id":84704013,"identity":"6a463e6b-19b9-4c4b-ba7e-a6bef3196ecd","added_by":"auto","created_at":"2025-06-16 12:03:13","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":146226,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of different cations and humic acids on the reaction system（a: Effect of different cations on the reaction system; a: Effect of different concentrations of HA on the reaction system）\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/608917a3f307eaab7711ac0a.png"},{"id":84704010,"identity":"02c683af-91c2-4a29-aa52-c2f6c55f03e1","added_by":"auto","created_at":"2025-06-16 12:03:13","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":2355573,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of Ca@ANFs/CNT before and after reaction (a-b: Ca@ANFs/CNT; c-d: Ca@ANFs/CNT-TCH)\u003c/p\u003e","description":"","filename":"image10.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/1b554b801bc2e4c16035fb23.png"},{"id":84705440,"identity":"4c380689-fecb-43a9-b202-25dbd7001f93","added_by":"auto","created_at":"2025-06-16 12:19:13","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":118148,"visible":true,"origin":"","legend":"\u003cp\u003eFT-IR and XRD plots of Ca@ANFs/CNT before and after reaction (a: FT-IR; b: XRD)\u003c/p\u003e","description":"","filename":"image11.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/e147f800f789b3390d305006.png"},{"id":84704003,"identity":"cda389fb-b55d-4c0b-a055-ee6b716d1973","added_by":"auto","created_at":"2025-06-16 12:03:13","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":3610312,"visible":true,"origin":"","legend":"\u003cp\u003eXPS analysis of Ca@ANFs/CNT before and after reaction\u003c/p\u003e","description":"","filename":"image12.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/c851b2670f3572ecf4524246.png"},{"id":84705158,"identity":"ea3a0017-6a81-4d4f-8ce4-2b4173327ec2","added_by":"auto","created_at":"2025-06-16 12:11:13","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":7568970,"visible":true,"origin":"","legend":"\u003cp\u003eAdsorption mechanism diagram of Ca@ANFs/CNT on TCH\u003c/p\u003e","description":"","filename":"image13.png","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/4c03d30b010c543917a253b7.png"},{"id":85352657,"identity":"9c0f418e-db08-4028-91c2-eb4223fd65d0","added_by":"auto","created_at":"2025-06-25 03:32:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":33136672,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6849815/v1/13077463-bc05-4163-8e6a-bfb7b724f1b7.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Hierarchical Aramid Nanofibers/Carbon Nanotubes Composite Aerogel Engineered for High-Efficiency Tetracycline Hydrochloride Removal","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe burgeoning growth of pharmaceutical, agribusiness, and aquaculture sectors has precipitated severe ecological crises through indiscriminate antibiotic deployment, now recognized as a critical global sustainability challenge. Tetracycline hydrochloride (TCH), a cost-effective broad-spectrum bacteriostatic, dominates agricultural and veterinary applications due to its potent bacteriostatic activity and chemical stability \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. However, its environmental persistence enables \u0026zwnj;multimedia migration\u0026zwnj; across atmospheric, aquatic, and terrestrial compartments, \u0026zwnj;disrupting biogeochemical cycles and threatening ecosystem integrity.\u0026zwnj; To enhance pollutant removal efficiency, understanding existing methods and their mechanisms is essential. Current treatment technologies, biological methods, physical methods, chemical methods, and advanced oxidation processes, face inherent limitations including narrow adsorption selectivity, prohibitive operational costs, and inadequate recoverability \u003csup\u003e[3]\u003c/sup\u003e. This technological gap has driven\u0026zwnj; innovation in \u0026zwnj;nanostructured adsorbents,\u0026zwnj; with aerogels emerging as \u0026zwnj;frontier materials\u0026zwnj; due to their \u0026zwnj;three-dimensional hierarchical porous architecture\u0026zwnj; and \u0026zwnj;tailorable surface chemistry \u003csup\u003e[4]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAmong these, aramid nanofibers (ANF) -based aerogels stand out\u0026zwnj; by inheriting the \u0026zwnj;exceptional mechanical robustness (\u0026gt;\u0026thinsp;500\u0026deg;C thermal stability) and chemical inertness\u0026zwnj; of poly (para phenylene terephthalamide) (PPTA) fibers\u003csup\u003e[5]\u003c/sup\u003e. Aramid nanofiber aerogels (ANFs) combine the advantages of high-performance aramid and nanofibers, serving as excellent nano-construction units and filler materials. Their superior properties have led to widespread applications in electrical insulation, lightweight structural materials, and flexible sensing. For example, Xu et al. \u003csup\u003e[6]\u003c/sup\u003emass-produced aramid nanofiber aerogel microspheres (ANFAMs) with dense skin and porous internal structures via wet-spinning technology, achieving effective removal of organic dyes in harsh chemical environments. Wang et al. \u003csup\u003e[7]\u003c/sup\u003eprepared honeycomb-like carboxylated multi-walled carbon nanotube/aramid nanofiber aerogels through sol-gel, unidirectional freezing, and freeze-drying, demonstrating promising electromagnetic wave absorption and thermal insulation properties.\u003c/p\u003e \u003cp\u003eCarbon nanotubes (CNT), tubular nanomaterials composed of carbon atoms, possess unique structures and excellent physicochemical properties. Multi-walled carbon nanotubes (MWCNT), in particular, have been widely studied due to their low cost, simple preparation, and stability, achieving significant results in electronics, catalysis, sensors, and energy storage. For instance, Wu et al. \u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003edeveloped a sensitive electrochemical sensor using ferrocene-covalently linked gold nanoparticles on MWCNT to enhance serotonin detection. Wang et al. \u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003ecoated magnetic nanoparticles on MWCNT to prepare magnetic MWCNT with abundant surface active sites, effectively treating Cr-containing heavy metal wastewater.\u003c/p\u003e \u003cp\u003eCapitalizing on these synergies,\u0026zwnj; we engineered an \u0026zwnj;ANFs/MWCNTs composite aerogel\u0026zwnj; through π\u0026ndash;π stacking-assisted physical cross-linking, integrating sol-gel and freeze-drying methods, enhancing corrosion and acid-base resistance while increasing specific surface area and adsorption capacity. This study not only optimizes material performance but also deciphers the \u0026zwnj;chelation-dominated removal mechanisms, offering insights for next-generation antibiotic capture technologies.\u003c/p\u003e"},{"header":"2 Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eDimethyl sulfoxide (DMSO) was purchased from Chengdu Kelong Chemical Reagent Co., Ltd., China; potassium hydroxide (KOH) and potassium chloride (KCl) from Tianjin Damao Chemical Reagent Co., Ltd., China; calcium sulfate (CaSO₄) from Tianjin Fuchen Chemical Reagent Co., Ltd., China; sodium chloride (NaCl), anhydrous calcium chloride (CaCl₂), calcium carbonate (CaCO₃), and absolute ethanol (CH₃CH₂OH) from Sinopharm Chemical Reagent Co., Ltd., China; anhydrous magnesium chloride (MgCl₂) and tetracycline hydrochloride (TCH, 99%) from Shanghai Macklin Biochemical Technology Co., Ltd., China; methanol (CH₃OH), acetonitrile (CH₃CN), and formic acid (HCOOH) from Tianjin Kemiou Chemical Reagent Co., Ltd., China; humic acid (HA) from Shanghai Aladdin Reagent Co., Ltd., China. All reagents and chemicals were used as received without further purification. Deionized water was provided by a laboratory water purifier.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Preparation of ANFs aerogel\u003c/h2\u003e \u003cp\u003eThe ANFs dispersion was prepared using the deprotonation and alkali dissolution methods. Ten grams of Kevlar short-cut fibers and an equal mass of KOH were added to a flask, followed by DMSO (dewatered), and stirred under nitrogen protection for 7 days to obtain a 2 wt% solution. ANFs dispersion. Similarly, ANFs dispersions with solid contents of 0.5 wt.%, 1 wt.%, and 1.5 wt.% were prepared. Seventy-five milliliters of the dispersion were mixed with 500 mL of deionized water to initiate gelation. After complete gelation, the gel was broken, sieved through a 2300-mesh sieve, and washed with water for 24 h to remove residual solvents. The gel was aged, loaded into a mold, pre-frozen at -20\u0026deg;C for 12 h to form a cryogel, and then freeze-dried for 48 h to obtain ANFs aerogel.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Preparation of ANFs/CNT aerogel with different coagulation baths\u003c/h2\u003e \u003cp\u003eThe ANFs/CNT dispersion was synthesized via physical cross-linking: CNT (1.38 g) and KOH (1.38 g) were dissolved in DMSO (100 mL) under 48 h stirring, then blended with 2 wt.% ANFs dispersion (100 mL) under nitrogen for 5 days. Varying carbon content dispersions (0.2\u0026ndash;0.8 wt.%) were prepared analogously. Its preparation process is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFor gelation, 75 mL ANFs/CNT dispersion was injected into a 5 mM CaCl₂ bath (500 mL). The resultant gel was homogenized, sieved (2300-mesh), and washed with CaCl₂ solution. Subsequent processing followed Section \u003cspan refid=\"Sec4\" class=\"InternalRef\"\u003e2.2\u003c/span\u003e (ANFs aerogel protocol), yielding Ca@ANFs/CNT. Control aerogels were designated as:\u003c/p\u003e \u003cp\u003eWater type variants: DI@ANFs (deionized), RO@ANFs (reverse osmosis), Tw@ANFs (tap), Pw@ANFs (purified). Salt-coagulated variants (5 mM): Ca@ANFs/CNT, Na@ANFs/CNT (NaCl), K@ANFs/CNT (KCl), Mg@ANFs/CNT (MgCl₂)\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Investigation of the effects of preparation conditions on aerogel adsorption performance\u003c/h2\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.4.1 Effect of coagulation bath on adsorption performance\u003c/h2\u003e \u003cp\u003eThirty milligrams of DI@ANFs, RO@ANFs, Tw@ANFs, and Pw@ANFs aerogels were added to 50 mL of 20 mg/L TCH solution, respectively. Samples were taken at different time points to measure TCH concentration. The adsorption performance of each material for TCH was compared to screen the optimal water-based coagulation bath.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e2.4.2 Effect of ANFs and CNT solid content on adsorption performance\u003c/h2\u003e \u003cp\u003eThe experimental materials were replaced with ANFs aerogels with solid contents of 0.5 wt.%, 1 wt.%, and 1.5 wt.% or ANFs/CNT aerogels with carbon contents of 0.2 wt.%, 0.5 wt.%, and 0.8 wt.%, the other steps were the same as in 2.4.1.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e2.4.3 Effect of different salt solution coagulation baths on adsorption performance\u003c/h2\u003e \u003cp\u003eThe experimental materials were replaced with Ca@ANFs/CNT, Na@ANFs/CNT, K@ANFs/CNT, and Mg@ANFs/CNT, and the experimental steps were the same as in 2.4.1.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Material Characterization\u003c/h2\u003e \u003cp\u003eSEM analysis was performed using a field-emission microscope after gold sputter-coating of dried aerogel samples. XRD patterns of modified biochar were obtained with a Bruker D8 Advance diffractometer (Cu-Kα radiation), with crystallinity analysis via Jade software. Surface area and porosity were determined by nitrogen adsorption-desorption using a Micromeritics ASAP 2460 system. FTIR spectra (400\u0026ndash;4000 cm⁻\u0026sup1;) were acquired through the KBr pellet method with a Nicolet iS20 spectrometer. XPS surface analysis was conducted on an ESCALAB Xi\u0026thinsp;+\u0026thinsp;system, with elemental quantification performed using Avantage software.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Effect of process parameters on TCH removal efficiency by ANF-based aerogels\u003c/h2\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e2.6.1 Effect of M@ANFs/CNT dosage on TCH removal\u003c/h2\u003e \u003cp\u003eTo investigate the TCH removal efficiency of Ca@ANFs/CNT under various solid-liquid ratios, experiments were conducted with a TCH concentration of 20 mg/L, a reaction volume of 50 mL, and Ca@ANFs/CNT dosages of 0.1, 0.2, 0.4, 0.6, and 1.0 g/L. Other conditions were kept constant (room temperature 25\u0026deg;C, rotation speed 200 rpm). Samples were taken at 3, 5, 15, 30, 60, 90, 120, 180, and 240 min, filtered through a 0.22 \u0026micro;m organic filter into 2 mL HPLC vials, and TCH concentration was measured by HPLC.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e2.6.2 Effect of initial TCH concentration on TCH removal\u003c/h2\u003e \u003cp\u003eTo study the TCH removal efficiency of Ca@ANFs/CNT at different initial TCH concentrations, the initial TCH concentrations were set to 5, 10, 20, 40, and 60 mg/L, with a reaction volume of 50 mL and a Ca@ANFs/CNT dosage of 0.6 g/L. Other experimental steps were the same as in 2.6.1.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e2.6.3 Effect of pH on TCH removal\u003c/h2\u003e \u003cp\u003eThe effect of initial pH (3, 5, 7, 9, 11) on TCH removal by Ca@ANFs/CNT was studied. Other conditions were kept constant (room temperature 25\u0026deg;C, Ca@ANFs/CNT 0.6 g/L, rotation speed 150 rpm), and samples were taken at the time points described in 2.6.1 to measure TCH concentration.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e2.6.4 Effect of exogenous ions and humic acid on TCH removal.\u003c/h2\u003e \u003cp\u003eEffect of anions: different concentrations (0.5, 1, 5, 10 mM) of NaCl, NaHCO₃, Na₂CO₃, and Na₂SO₄ were added, and other conditions were kept constant (reaction volume 50 mL, material dosage 0.6 g/L, TCH concentration 20 mg/L, room temperature 25\u0026deg;C). Samples were taken at the same time with 2.6.1 to measure TCH concentration.\u003c/p\u003e \u003cp\u003eEffect of cations: 0.5 mM CaCl₂, NaCl, KCl, MgCl₂, and CuCl₂\u0026middot;2H₂O were added to the reaction solution to investigate their effects on TCH removal by Ca@ANFs/CNT. Other conditions were unchanged, and samples were taken at the time points in 2.6.1 for measurement.\u003c/p\u003e \u003cp\u003eEffect of humic acid (HA): Different concentrations (10, 20, 40, 100 mg/L) of HA were added to the system, and other conditions were kept constant. Samples were taken at the time points in 2.6.1 to measure TCH concentration.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"3 Results and discussion","content":"\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Screening and optimization of aerogel materials\u003c/h2\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003e3.1.1 Effect of different aerogels on adsorption performance\u003c/h2\u003e \u003cp\u003eThe ionic composition of coagulation baths containing varying anionic and cationic species was found to potentially influence the physicochemical characteristics of aerogels during the gelation process. Comparative adsorption experiments revealed that DI@ANFs, RO@ANFs, and Pw@ANFs had comparable TCH adsorption capacities within 240 min (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea), whereas Tw@ANFs demonstrated significantly enhanced performance, achieving 83.73% TCH removal within 90 min under the identical experimental conditions. Based on this marked efficiency improvement, tap water was selected as the coagulation medium for subsequent optimization of ANF/CNT composite formulations.\u003c/p\u003e \u003cp\u003eThe solid content of aramid fibers is a key factor determining the structural density and performance characteristics of the aerogel materials. When the solid content was 1 wt.%, the ANFs material exhibited superior TCH sequestration capability, achieving 91.51% removal efficiency (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Therefore, 1 wt.% ANFs were used as the base material for the subsequent screening of different carbon nanotube contents. Further verification of the TCH removal efficiency of ANFs/CNT with different carbon contents showed that the 0.5 wt.% ANFs/CNT material still outperformed other carbon contents, achieving adsorption equilibrium within 8 h and removing 63.58% of TCH, with an adsorption capacity of 169.91 mg/g (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). When the CNT content in the material increased further, the TCH removal efficiency of ANFs/CNT decreased to some extent. Integrating performance metrics with cost-effectiveness considerations, the optimal CNT loading was strategically fixed at 0.5 wt.% for all downstream composite fabrication processes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe TCH removal efficiency of materials with different salt solution coagulation baths was investigated. Results showed that Ca@ANFs/CNT prepared with 1 mM CaCl₂ solution as the coagulation bath achieved 83.5% TCH elimination within 90 min, higher than K@ANFs/CNT, Na@ANFs/CNT, Mg@ANFs/CNT, and DI@ANFs/CNT(Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). Notably, when increasing the salt solution concentration to 5 mM, Ca@ANFs/CNT still maintained superiority in contaminant removal(Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e \u003ch2\u003e3.1.2 Characterization of ANFs/CNT materials prepared with different coagulation baths\u003c/h2\u003e \u003cp\u003eScanning electron microscopy (SEM) analysis revealed morphological differences in aerogels prepared with different metal salts (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Na⁺- and K⁺-based systems (Na@ANFs/CNT, K@ANFs/CNT) retained three-dimensional (3D) porous networks; however, energy-dispersive X-ray spectroscopy (EDS) indicated low-density distribution of Na/K elements (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea\u003csub\u003e4\u003c/sub\u003e/c\u003csub\u003e4\u003c/sub\u003e) with localized agglomeration. In contrast, Mg\u0026sup2;⁺-incorporated aerogels (Mg@ANFs/CNT) exhibited uniformly aligned needle-like MgO crystals on their surfaces (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb\u003csub\u003e1\u003c/sub\u003e-b\u003csub\u003e3\u003c/sub\u003e). The growth of these crystals induced partial structural collapse, significantly reducing porosity and specific surface area. Notably, despite the homogeneous distribution of Mg, irreversible structural damage occurred due to stress interactions between the crystals and the framework.\u003c/p\u003e \u003cp\u003eThe Ca\u0026sup2;⁺-incorporated system (Ca@ANFs/CNT) displayed a distinctive layered-curling morphology (Fig.\u0026nbsp;5a\u003csub\u003e1\u003c/sub\u003e), attributed to an interpenetrating network formed via π-π stacking and hydrogen bonding between CNTs and ANFs. Pore reconstruction during freeze-drying (Figs.\u0026nbsp;5a\u003csub\u003e2\u003c/sub\u003e-a\u003csub\u003e3\u003c/sub\u003e) endowed the material with high porosity (\u0026gt;\u0026thinsp;90%) and interconnected mesopores (2\u0026ndash;50 nm), providing abundant adsorption sites. EDS analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb) confirmed its composition: C/N/O dominated (\u0026gt;\u0026thinsp;85 wt.%), consistent with ANF/CNT components, while trace S (0.7 wt.%) and Cl (1.2 wt.%) originated from DMSO residues and ion exchange. Ca\u0026sup2;⁺ was uniformly distributed (8.22 wt.%, CV\u0026thinsp;\u0026lt;\u0026thinsp;5%), demonstrating stable anchoring via anion exchange. This structure-composition correlation elucidates the superior adsorption performance of the Ca\u0026sup2;⁺ system.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e presents comparative XRD and FTIR analyses of the crystal structures of DI@ANFs/CNT and Ca@ANFs/CNT. XRD patterns (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea) reveal analogous crystalline phases in both materials, with retained diffraction peaks at (110), (200), and (004) planes characteristic of aramid nanofibers. Notably, the (004) plane diffraction in Ca@ANFs/CNT exhibits peak overlap due to epitaxial growth of CaCO₃ crystals, confirming carbonate phase coexistence (PDF#05-0586) \u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e. Both materials show the (002) crystal plane corresponding to carbon nanotube crystals, confirming that carbon nanotubes are loaded onto the surface of aramid fibers via π-π conjugation.\u003c/p\u003e \u003cp\u003eThe FTIR spectrum in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb identifies critical functional groups and bonding interactions within the materials. The characteristic N-H stretching vibration of aramid fibers appears at 3420 cm⁻\u0026sup1;, while the bands at 1600 cm⁻\u0026sup1; and 1355 cm⁻\u0026sup1; are ascribed to C\u0026thinsp;=\u0026thinsp;O stretching and C-H bending modes in PPTA, respectively. Notably, Ca@ANFs/CNT exhibits a slight redshift and diminished intensity in these peaks, attributed to hydrogen-bond reorganization between amino and hydroxyl groups within its framework \u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. The characteristic band vibration at 770 cm⁻\u0026sup1; is attributed to the asymmetric stretching vibration of the C-H group and the characteristic band vibration at 1310 cm⁻\u0026sup1; is considered the unique Ph-N vibration of PPTA, confirming that the matrix of both fiber materials is ANF \u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. The characteristic band vibration at 1410 cm⁻\u0026sup1; in Ca@ANFs/CNT is the vibration of nano-calcium carbonate, indicating that part of the calcium carbonate is loaded on the material surface via anion exchange \u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. Furthermore, weak absorptions at 1110 cm⁻\u0026sup1; (Ca-O lattice vibration) and 1020 cm⁻\u0026sup1; (Ca-OH bending) provide conclusive evidence for the successful incorporation of calcium species \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Effects of different process conditions on the adsorption performance of Ca@ANFs/CNT\u003c/h2\u003e \u003cdiv id=\"Sec21\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1 Effect of Ca@ANFs/CNT dosage on the adsorption performance\u003c/h2\u003e \u003cp\u003eThe dosage of the material is a critical factor in maintaining the reaction equilibrium in the system, often determining the number of reactive sites \u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea shows the TCH removal efficiency of Ca@ANFs/CNT at different dosages for a 20 mg/L TCH solution. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea, the TCH removal efficiency at 20 mg/L initial concentration exhibits a strong dependence on adsorbent dosage. Increasing the dosage to 0.4 g/L significantly enhanced removal efficiency, 82.80% at 120 min equilibrium, reflecting improved site accessibility. Further dosage escalation to 0.6 g/L and 1 g/L yielded near-saturation performance, indicating site abundance. Beyond 0.6 g/L, minimal efficiency gains were observed, suggesting surface saturation. Balancing cost-effectiveness, adsorption capacity, and practical feasibility, the optimal dosage was determined as 0.6 g/L for subsequent studies.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section3\"\u003e \u003ch2\u003e3.2.2 Effect of initial TCH concentration on adsorption performance\u003c/h2\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb, Ca@ANFs/CNT demonstrated good removal efficiency for 5, 10, and 20 mg/L TCH solutions, with rapid TCH concentration decline within the first 30 min, followed by slow equilibrium, and removal efficiency of 88.62%, 92.45%, and 92.56%, respectively. When the TCH concentration increased to 40 mg/L and 60 mg/L, the equilibrium time was significantly prolonged, and the removal efficiency decreased, with 83.29% and 78.57% TCH removed within 240 min. However, as the TCH concentration increased from 5 mg/L to 60 mg/L, the adsorption capacity of Ca@ANFs/CNT for TCH increased from 7.33 mg/g to 80.14 mg/g, indicating that higher TCH concentrations enhance the driving force for removal, promoting TCH migration from the solution to the adsorbent surface. However, excessively high TCH concentrations may lead to limited adsorption sites, reducing the removal efficiency.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn actual water bodies, tetracycline concentrations vary across different water environments. Studies have found that residual TCH concentrations in some water media in China generally range from ng/L to \u0026micro;g/L \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e, but in some areas with heavy antibiotic use, TCH concentrations in livestock wastewater and medical wastewater can reach the mg/L level, typically not exceeding 5 mg/L \u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. Therefore, the results of this study provide valuable guidance for TCH removal in real aquatic systems.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section3\"\u003e \u003ch2\u003e3.2.3 Effect of initial pH on adsorption performance\u003c/h2\u003e \u003cp\u003eThe initial pH of the solution can affect the charge properties of the material surface and the form of pollutants during organic contaminant removal \u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. The unique structure of TCH molecules causes them to ionize into different ionic states (TCH\u0026sup3;⁺, TCH\u0026sup2;⁺, TCH⁻, TC\u0026sup2;⁻) under different pH conditions. The pKa values of TCH are pKa\u003csub\u003e1\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;3.30, pKa\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;7.6, and pKa\u003csub\u003e3\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;9.27. Below pH 3.3, TCH exists as H₃TC⁺; between 3.3 and 7.6, as HTC⁰; between 7.6 and 9.27, as HTC⁻; and above 9.27, as TC\u0026sup2;⁻ \u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. Therefore, Ca@ANFs/CNT exhibits different TCH removal efficiencies at different pH values. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec, the material showed good TCH removal performance at pH 5\u0026thinsp;~\u0026thinsp;11, achieving adsorption equilibrium within approximately 90 min with removal rates above 90%. As pH increased from 5 to 11, the TCH removal capacity increased slightly, likely because TCH molecules gradually deprotonate acidic functional groups with increasing pH, transforming from HTC⁰ to negatively charged HTC⁻ and TC\u0026sup2;⁻, while the Ca@ANFs/CNT surface carries positive charges, enhancing electrostatic attraction and removal efficiency. At pH\u0026thinsp;=\u0026thinsp;3 (acidic conditions), TCH deprotonates basic functional groups to exist as H₃TC⁺, repelling the positive charges on the Ca@ANFs/CNT surface, enhancing electrostatic repulsion, and inhibiting complexation, resulting in significantly reduced removal efficiency (76.80% TCH removed within 240 min). Since the TCH solution is weakly acidic (pH\u0026thinsp;\u0026asymp;\u0026thinsp;6), no buffer was used to adjust the pH in subsequent experiments.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Effects of different ions and humic acid on TCH adsorption by Ca@ANFs/CNT\u003c/h2\u003e \u003cdiv id=\"Sec25\" class=\"Section3\"\u003e \u003ch2\u003e3.3.1 Effect of anions on adsorption performance\u003c/h2\u003e \u003cp\u003eNatural aquatic systems typically contain diverse anion species, with Cl⁻, HCO₃⁻, CO₃\u0026sup2;⁻, and SO₄\u0026sup2;⁻ being particularly prevalent constituents that may exert significant influences on the reaction system. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea, increasing the SO₄\u0026sup2;⁻ concentration from 0.5 mM to 10 mM had little effect on TCH removal efficiency by Ca@ANFs/CNT, with approximately 92% TCH removed within 240 min in both the presence and absence of SO₄\u0026sup2;⁻, indicating that SO₄\u0026sup2;⁻ does not interfere with TCH removal by Ca@ANFs/CNT. In contrast, CO₃\u0026sup2;⁻ significantly reduced TCH removal efficiency (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec). The TCH removal efficiency exhibited an inverse correlation with CO₃\u0026sup2;⁻ concentration, declining from 89.40% at 1 mM to 58.97% at 10 mM, representing a reduction of approximately 30%. This effect could be attributed to excessive CO₃\u0026sup2;⁻ binding with Ca\u0026sup2;⁺ on the material surface to form CaCO₃ precipitates, increasing solution mineralization, and CO₃\u0026sup2;⁻ competing with TC for adsorption sites on the material surface. Additionally, studies have shown that CO₃\u0026sup2;⁻ can shield \u0026middot;OH under light, inhibiting natural photolysis, thus reducing removal efficiency in the reaction system. HCO₃⁻ showed weak inhibitory effects at low to moderate concentrations, with the removal efficiency decreasing from 92.76\u0026ndash;86.65% at high concentrations, possibly due to partial hydrolysis of HCO₃⁻ to form a small amount of CO₃\u0026sup2;⁻, leading to reduced efficiency. As a common ion in water, Cl⁻ had little effect on TCH removal, with a removal efficiency of around 90% at both low and high concentrations, similar to the ion-free control.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section3\"\u003e \u003ch2\u003e3.3.2 Effect of cations and humic acid on adsorption performance\u003c/h2\u003e \u003cp\u003eTetracycline-containing wastewater, as a refractory organic wastewater, typically contains various cations. Notably, certain light metal ions may compete with tetracycline molecules for adsorption sites. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea, K⁺, Ca\u0026sup2;⁺, Na⁺, and Mg\u0026sup2;⁺ had weak effects on the system, with reaction trends and final removal rates similar to the ion-free control, all removing approximately 90% of TCH, indicating that 0.5 mM of these cations exhibit little competitive adsorption with tetracycline hydrochloride and do not significantly affect TCH removal. However, the presence of 0.5 mM Cu\u0026sup2;⁺ caused the reaction system to achieve nearly 100% TCH removal within 30 min, possibly because copper, as a transition metal, provides efficient and selective removal capabilities, enhancing antibiotic removal \u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eHumic acid, a common organic matter in nature, is widely present in natural aquatic systems and polluted wastewater, affecting the removal of organic substances\u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. At 40 mg/L HA, the material still removed 90% of TCH, but at 100 mg/L HA, the inhibition significantly increased, with the TCH removal rate dropping to 81.61% within 240 min (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb). The observed phenomenon primarily stems from HA-induced pH depression. Specifically, when solution pH is reduced below 3.3 by elevated HA concentrations, TCH predominantly exists in H₃TC⁺ form, leading to two concurrent effects: enhancing electrostatic repulsion and reducing reaction efficiency.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec27\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Characterization of Ca@ANFs/CNT before and after TCH adsorption\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e presents comparative SEM microstructural analyses of Ca@ANFs/CNT in pre-adsorption and post-adsorption states following TCH exposure. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ea\u0026ndash;b are pre-adsorption surface morphologies, and Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ec\u0026ndash;d are post-adsorption morphologies. After adsorption, the curling structure on the Ca@ANFs/CNT surface became more pronounced, and the three-dimensional network structure became looser. This is because the reaction solution was continuously stirred to ensure uniform contact between the material and TCH molecules, causing the aerogel to disperse evenly in the liquid due to centrifugal force, thus efficiently removing pollutants.\u003c/p\u003e \u003cp\u003eFT-IR spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ea) show that the peaks at 3440 cm⁻\u0026sup1; and 1637 cm⁻\u0026sup1; correspond to the N-H stretching vibration and C\u0026thinsp;=\u0026thinsp;O stretching vibration of PPTA fibers, respectively. After the reaction with TCH, the intensity of the N-H stretching vibration peak at 3440 cm⁻\u0026sup1; decreased significantly, and the C\u0026thinsp;=\u0026thinsp;O stretching vibration peak at 1637 cm⁻\u0026sup1; shifted to 1663 cm⁻\u0026sup1;, indicating that the carbonyl and amino groups of the material participated in TCH adsorption via hydrogen bonding \u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. The enhanced peak at 1520 cm⁻\u0026sup1; after reaction corresponds to the carbonyl skeleton stretching vibration peak of TCH molecules, further confirming TCH capture by Ca@ANFs/CNT. The Ca-O stretching vibration peak at 825 cm⁻\u0026sup1; shifted to 810 cm⁻\u0026sup1; after the reaction, suggesting that calcium ions on the material surface formed Ca-TC complexes with hydroxyl and carbonyl groups on tetracycline via complexation\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e. Additionally, changes in the displacement and intensity of the C-H stretching vibration peak of natural TC after reaction further indicate that TCH was immobilized on the Ca@ANFs/CNT surface via electrostatic attraction and hydrogen bonding \u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. XRD analysis of crystal morphology in pre-adsorption and post-adsorption states (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003eb) showed a distinct CaCO₃ crystal diffraction peak at 29.4\u0026deg; (corresponding to PDF #05-0586), which weakened significantly after reaction with TCH, further confirming that Ca\u0026sup2;⁺ participated in TCH adsorption.\u003c/p\u003e \u003cp\u003eTo elucidate the adsorption mechanisms, X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical composition and electronic states of surface elements (C, O, Ca) in Ca@ANFs/CNT composites before and after TCH adsorption, with spectral deconvolution analysis conducted using Thermo Scientific Avantage software (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e). Figures\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003ea\u0026ndash;b shows the C 1s spectra before and after adsorption. Peaks at 284.8 eV and 288.1 eV correspond to C-C and O-C\u0026thinsp;=\u0026thinsp;O bonds in the material, respectively. After TCH adsorption, the intensities of both peaks decreased, and the O-C\u0026thinsp;=\u0026thinsp;O peak shifted slightly to 288.0 eV, likely due to the dissociation of carboxyl groups via hydrogen bonding and their binding with TCH molecules.\u003c/p\u003e \u003cp\u003eThe C-O-C bond at 285.58 eV shifted to 285.5 eV, and its peak area increased from 15.25\u0026ndash;38.76%, indicating that TCH molecules bound to oxygen-containing groups on the aerogel surface via hydrogen bonding and electrostatic attraction\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. The π-π satellite peak at 290.95 eV showed weak vibration and reduced area after adsorption, suggesting that π-π interactions also contributed to TCH adsorption \u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e. Figures\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003ec\u0026ndash;d show the O 1s spectra before and after adsorption. The weakening and blue shift of C\u0026thinsp;=\u0026thinsp;O and H-O-C bonds after TC binding further indicate that the material captured TCH molecules by dissociating surface carbonyl and carboxyl groups to form hydrogen bonds with hydroxyl and amino groups on TCH. In the Ca 2p spectrum, peaks at 347.14 eV and 350.64 eV correspond to Ca 2p3/2 and Ca 2p1/2 of CaCO₃, respectively \u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e. After reaction with TCH, their peak areas decreased from 60.71% and 35.66\u0026ndash;56.9% and 27.75%, respectively, confirming that Ca\u0026sup2;⁺ complexed with TCH molecules to promote TCH removal. Studies have shown that tetracycline dissociates surface carbonyl and hydroxyl groups to complexes with Ca\u0026sup2;⁺, and hydroxyl groups on tetracycline dissociate more easily in alkaline environments, thus enhancing complexation \u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e. This ion-complexation mechanism provides a plausible explanation for the observed pH-dependent adsorption efficiency, with optimal TCH removal achieved at elevated pH values.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIntegrated mechanistic analysis reveals that TCH adsorption by the Ca@ANFs/CNT composite arises from multiple synergistic mechanisms, including complexation, hydrogen bonding, π-π interactions, electrostatic attraction, and pore filling, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eIn this study, the Ca@ANFs/CNT material was prepared under optimized conditions, and its performance and mechanism for TCH removal in water were systematically investigated. Experimental results show that Ca@ANFs/CNT exhibits excellent TCH removal efficiency (\u0026gt;\u0026thinsp;90%) under optimized conditions (dosage of 0.6 g/L, pH\u0026thinsp;\u0026gt;\u0026thinsp;3.30). Environmental interference assays revealed that high concentrations of CO₃\u0026sup2;⁻ (10 mM) significantly inhibit removal efficiency by competing for Ca\u0026sup2;⁺, while Cu\u0026sup2;⁺ accelerates the reaction via synergistic adsorption pathways, and humic acid inhibits removal efficiency with increasing concentration. This study not only reveals the multi-mechanism adsorption principle of Ca@ANFs/CNT but also provides actionable guidelines for designing cost-effective, multifunctional materials for practical water remediation scenarios involving emerging contaminants.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eDeclaration of Competing Interest:\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eLi Hua: Conceptualization, methodology, funding acquisition, writing\u0026mdash;original draft, and writing\u0026mdash;review \u0026amp; editing. Linfeng Li: Investigation, methodology, data curation. Yu Chen: Methodology, Software. Gaofan Dai: Methodology, Software.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThis research was partially supported by the National Natural Science Foundation of China under Grant (22376133) and the Key Research and Development Program in Shaanxi Province (2024PT-ZCK-09)\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eGudda F, Odinga E S, Tang L, et al. Tetracyclines uptake from irrigation water by vegetables: Accumulation and antimicrobial resistance risks[J]. Environmental Pollution, 2023, 338, 122696. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.envpol.2023.122696\u003c/span\u003e\u003cspan address=\"10.1016/j.envpol.2023.122696\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShi M Q, Wang H F, Yuan P Q, et al. 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Royal Society of Chemistry Advances, 2019, 9(67): 39355. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/c9ra07289f\u003c/span\u003e\u003cspan address=\"10.1039/c9ra07289f\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Aramid nanofibers, Carbon nanotubes, Adsorption mechanism, Aerogel","lastPublishedDoi":"10.21203/rs.3.rs-6849815/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6849815/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTo address the growing concern over tetracycline (TCH) pollution in aquatic systems, this study employed high-temperature, corrosion-resistant, and acid-base-resistant aramid nanofibers (ANF) as the substrate material. By integrating physical cross-linking combined with π-π conjugation, ANFs/CNT aerogels were prepared using sol-gel and freeze-drying methods with cost-effective and chemically stable multi-walled carbon nanotubes (CNT). The optimized composite, Ca@ANFs/CNT, was identified through systematic optimization of solid-phase ratios and salt solution coagulation baths. Critical environmental parameters governing TCH removal by Ca@ANFs/CNT were investigated. Experimental results demonstrated that Ca@ANFs/CNT attained a 94.6% TCH elimination efficiency for 20 mg/L TCH solution under ambient conditions, coupled with a maximum adsorption capacity of 104.18 mg/g. The material maintained superior stability and efficiency across a wide pH range of 5\u0026thinsp;~\u0026thinsp;11, exhibiting resilience against interference from ubiquitous anions (Cl⁻, SO₄\u0026sup2;⁻) in water had minimal impact on its performance. Notably,\u0026zwnj; \u0026zwnj;elevated CO₃\u0026sup2;⁻ concentrations and humic acid reduced reaction efficiency due to competitive adsorption and pH changes. Combined Kinetic and thermodynamic modeling established chemical adsorption as the rate-limiting mechanism. Characterization techniques such as FT-IR, XPS, and SEM elucidated that Ca\u0026sup2;⁺ mediated chelation is the cornerstone of TCH sequestration, augmented by synergistic contributions from electrostatic attraction, hydrogen bonding, and π-π conjugation effects. Additionally, the material\u0026rsquo;s pore structure contributed to adsorption. This study advances the rational design of antibiotic-capturing materials by unraveling structure-function relationships \u0026zwnj;while demonstrating Ca@ANFs/CNT\u0026rsquo;s practical viability for real-world water purification.\u0026zwnj; These findings establish a paradigm for developing multifunctional adsorbents targeting emerging contaminants in aquatic systems.\u003c/p\u003e","manuscriptTitle":"Hierarchical Aramid Nanofibers/Carbon Nanotubes Composite Aerogel Engineered for High-Efficiency Tetracycline Hydrochloride Removal","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-16 12:03:08","doi":"10.21203/rs.3.rs-6849815/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"601149e2-6333-43de-aedb-3694bd63cb15","owner":[],"postedDate":"June 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-06-25T03:23:39+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-16 12:03:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6849815","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6849815","identity":"rs-6849815","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}