Dual-functional Ag-Fe@Biochar systems: simultaneous adsorption and radical-mediated oxidation of antibiotics in fenton-like reactions

Abstract

The prevalence of quinolone antibiotics as emerging contaminants in wastewater necessitates urgent remediation strategies due to their recalcitrant nature and ecological risks. This study demonstrates an innovative Ag-nZVI/BC composite synthesized through silver-modified nZVI immobilized on coconut shell biochar, which effectively activates H₂O₂ for levofloxacin (LVF) degradation. The composite’s exceptional performance (91.2% LVF removal at 0.3 g/L dosage) stems from its 238 m²/g specific surface area and abundant oxygen-containing functionalities that facilitate electron transfer. Systematic parameter optimization revealed pH 3.0, 10 mmol/L H₂O₂, and 0.3 g/L catalyst as optimal conditions, while coexisting anions showed differential inhibition effects. Radical quenching experiments coupled with EPR spectroscopy confirmed ·OH and ·O₂⁻ as dominant reactive species. Through LC-MS analysis, we identified three primary degradation pathways involving piperazine ring cleavage and defluorination. Notably, eco-toxicity assessment using ECOSAR indicated 62.7% reduction in acute aquatic toxicity after treatment. The regenerable catalyst maintained 83.4% efficiency after five cycles, demonstrating a sustainable approach for antibiotic-contaminated wastewater remediation.

Graphical abstract

Keywords

Silver-modified / nZVI / Biochar / Levofloxacin / Ecotoxicity

Highlight

	● Ag-nZVI loaded coconut shell biochar material (Ag-nZVI/BC) was obtained.
	● Ag-nZVI/BC with activated H2O2 has high efficiency for the removal of LVF.
	● Ag-nZVI/BC could still achieve 78.7% LAF removal after three repeated use.
	● The eco-toxicity of LVF was effectively attenuated after degradation.

References

[1] Ahmed M B, Zhou J L, Ngo H H, Guo W S, Johir M a H, Sornalingam K, Belhaj D, Kallel M. (2017). Nano-Fe⁰ immobilized onto functionalized biochar gaining excellent stability during sorption and reduction of chloramphenicol via transforming to reusable magnetic composite. Chemical Engineering Journal, 322: 571–581

[2] Babuponnusami A, Muthukumar K. (2013). Treatment of phenol-containing wastewater by photoelectro-Fenton method using supported nanoscale zero-valent iron. Environmental Science and Pollution Research, 20(3): 1596–1605

[3] Barzegar G, Jorfi S, Zarezade V, Khatebasreh M, Mehdipour F, Ghanbari F. (2018). 4-Chlorophenol degradation using ultrasound/peroxymonosulfate/nanoscale zero valent iron: reusability, identification of degradation intermediates and potential application for real wastewater. Chemosphere, 201: 370–379

[4] Cao J Y, Lai L D, Lai B, Yao G, Chen X, Song L P. (2019). Degradation of tetracycline by peroxymonosulfate activated with zero-valent iron: performance, intermediates, toxicity and mechanism. Chemical Engineering Journal, 364: 45–56

[5] Chang C, Lian F, Zhu L Y. (2011). Simultaneous adsorption and degradation of γ-HCH by nZVI/Cu bimetallic nanoparticles with activated carbon support. Environmental Pollution, 159(10): 2507–2514

[6] Chen Y Q, Bai F, Li Z Y, Xie P C, Wang Z P, Feng X N, Liu Z Z, Huang L Z. (2020). UV-assisted chlorination of algae-laden water: cell lysis and disinfection byproducts formation. Chemical Engineering Journal, 383: 123165

[7] Cheng H, Zheng X Y, Zhu Y, Wang P, Zhu J, Wei J, Liu Z L, Huang C. (2024). Stabilization of sulfidated nano zerovalent iron with biochar: enhanced transport and application for hexavalent chromium removal from water. Journal of Environmental Management, 371: 123045

[8] Deng J M, Dong H R, Zhang C, Jiang Z, Cheng Y J, Hou K J, Zhang L H, Fan C Z. (2018). Nanoscale zero-valent iron/biochar composite as an activator for Fenton-like removal of sulfamethazine. Separation and Purification Technology, 202: 130–137

[9] Dong G H, Chi W M, Chai D F, Zhang Z F, Li J L, Zhao M, Zhang W Z, Lv J, Chen S J. (2023). A novel Ag₃BiO₃/ZnO/BC composite with abundant defects and utilizing hemp BC as charge transfer mediator for photocatalytic degradation of levofloxacin. Applied Surface Science, 619: 156732

[10] Dong H R, Jiang Z, Deng J M, Zhang C, Cheng Y J, Hou K J, Zhang L H, Tang L, Zeng G M. (2018). Physicochemical transformation of Fe/Ni bimetallic nanoparticles during aging in simulated groundwater and the consequent effect on contaminant removal. Water Research, 129: 51–57

[11] DongZ PLe XLiX LZhangWDongC X MaJ T (2014). Silver nanoparticles immobilized on fibrous nano-silica as highly efficient and recyclable heterogeneous catalyst for reduction of 4-nitrophenol and 2-nitroaniline. Applied Catalysis B: Environmental, 158–159: 158–159

[12] Fan W, Shen X L, Zhu Z L, Liu X C, Zhang H, Qiu Y L, Yin D Q. (2025). Rsearch progress on biochar materials for new pollutants removal in the aquatic environment: a mini-review. Frontiers of Environmental Science & Engineering, 19(3): 33

[13] Fang Z Q, Qiu X H, Chen J H, Qiu X Q. (2011). Debromination of polybrominated diphenyl ethers by Ni/Fe bimetallic nanoparticles: influencing factors, kinetics, and mechanism. Journal of Hazardous Materials, 185(2−3): 958–969

[14] Gao J, Han D Q, Xu Y, Liu Y Y, Shang J G. (2020). Persulfate activation by sulfide-modified nanoscale iron supported by biochar (S-nZVI/BC) for degradation of ciprofloxacin. Separation and Purification Technology, 235: 116202

[15] Gao Y Q, Gao N Y, Wang W, Kang S F, Xu J H, Xiang H M, Yin D Q. (2018). Ultrasound-assisted heterogeneous activation of persulfate by nano zero-valent iron (nZVI) for the propranolol degradation in water. Ultrasonics Sonochemistry, 49: 33–40

[16] Gopal G, Sankar H, Natarajan C, Mukherjee A. (2020). Tetracycline removal using green synthesized bimetallic nZVI-Cu and bentonite supported green nZVI-Cu nanocomposite: a comparative study. Journal of Environmental Management, 254: 109812

[17] Guo Y G, Zhao Y, Yang T X, Gong B, Chen B. (2021). Highly efficient nano-Fe/Cu bimetal-loaded mesoporous silica Fe/Cu-MCM-41 for the removal of Cr(VI): kinetics, mechanism and performance. Journal of Hazardous Materials, 418: 126344

[18] Hong Q F, Liu C, Wang Z B, Li R Y, Liang X L, Wang Y P, Zhang Y T, Song Z L, Xiao Z H, Cui T Y. . (2021). Electron transfer enhancing Fe(II)/Fe(III) cycle by sulfur and biochar in magnetic FeS@biochar to active peroxymonosulfate for 2,4-dichlorophenoxyacetic acid degradation. Chemical Engineering Journal, 417: 129238

[19] LiQ YWei G TZhangL YLiZ MLiJ H (2023). Activation of peroxymonosulfate by a waste red mud-supported Co₃O₄ quantum dots under visible light for the degradation of levofloxacin. Chemical Engineering Journal, 452(Pt 2): 139382

[20] Li Y C, Li T L, Jin Z H. (2011). Stabilization of Fe⁰ nanoparticles with silica fume for enhanced transport and remediation of hexavalent chromium in water and soil. Journal of Environmental Sciences, 23(7): 1211–1218

[21] Liu F L, Zuo J N, Chi T, Wang P, Yang B. (2015). Removing phosphorus from aqueous solutions by using iron-modified corn straw biochar. Frontiers of Environmental Science & Engineering, 9(6): 1066–1075

[22] Liu K, Li M R, Zhu Z L, Gao B L, Zeng H C, Ma Y B, Fang L P. (2021). Emerging investigator series: 3D graphene anchored zerovalent Fe/Cu aerogel activating persulfate for efficiently 2,4 dichlorophenol degradation over a broad pH range. Environmental Science: Water Research & Technology, 7(4): 714–725

[23] Lu X W, Wu L S, Liang L L, Liu D, Chen Y Z, Zeng Y L, Zhong M J, Jia B. (2023). Levofloxacin degradation by porous Co_x/CN activated peroxymonosulfate: investigation of efficiency, mechanism, and degradation pathways. Journal of Water Process Engineering, 56: 104427

[24] Lv H Z, Niu H Y, Zhao X L, Cai Y Q, Wu F C. (2021). Carbon zero-valent iron materials possessing high-content fine Fe⁰ nanoparticles with enhanced microelectrolysis-Fenton-like catalytic performance for water purification. Applied Catalysis B: Environmental, 286: 119940

[25] Ma Q L, Zhang H X, Zhang X Y, Li B, Guo R N, Cheng Q F, Cheng X W. (2019). Synthesis of magnetic CuO/MnFe₂O₄ nanocompisite and its high activity for degradation of levofloxacin by activation of persulfate. Chemical Engineering Journal, 360: 848–860

[26] Ma Q Q, Cui L, Zhou S, Li Y, Shi W J, Ai S Y. (2018). Iron nanoparticles in situ encapsulated in lignin-derived hydrochar as an effective catalyst for phenol removal. Environmental Science and Pollution Research, 25(21): 20833–20840

[27] Masud M A A, Shin W S, Septian A, Samaraweera H, Khan I J, Mohamed M M, Billah M M, López-Maldonado E A, Rahman M M, Islam A R M T. . (2024). Exploring the environmental pathways and challenges of fluoroquinolone antibiotics: a state-of-the-art review. Science of the Total Environment, 926: 171944

[28] Othman S I, Alfassam H E, Alqhtani H A, Al-Waili M A, Allam A A, Abukhadra M R. (2024). Insight into the catalytic performances of Fe⁰@chitosan/cellulose green hybrid structure for enhanced photo-Fenton's oxidation of levofloxacin toxic residuals: pathway and toxicity. International Journal of Biological Macromolecules, 265: 130615

[29] Plaza J, Arencibia A, López-Muñoz M J. (2021). Evaluation of nZVI for the degradation of atrazine in heterogeneous Fenton-like systems at circumneutral pH. Journal of Environmental Chemical Engineering, 9(6): 106641

[30] Prieto P, Nistor V, Nouneh K, Oyama M, Abd-Lefdil M, Díaz R. (2012). XPS study of silver, nickel and bimetallic silver-nickel nanoparticles prepared by seed-mediated growth. Applied Surface Science, 258(22): 8807–8813

[31] Qian L B, Shang X, Zhang B, Zhang W Y, Su A Q, Chen Y, Ouyang D, Han L, Yan J C, Chen M F. (2019). Enhanced removal of Cr(VI) by silicon rich biochar-supported nanoscale zero-valent iron. Chemosphere, 215: 739–745

[32] Sarfaraz Q, da Silva L S, Drescher G L, Zafar M, Severo F F, Kokkonen A, Dal Molin G, Shafi M I, Shafique Q, Solaiman Z M. (2020). Characterization and carbon mineralization of biochars produced from different animal manures and plant residues. Scientific Reports, 10(1): 955

[33] Shen Z H, Peng G G, Shi J L, Ya G. (2021). A new supported Cu/Pd bimetallic nanoparticles composites prestoring reductant for nitrate removal: high reactivity and N₂ selectivity. Environmental Science and Pollution Research, 28(37): 51786–51794

[34] Wang B S, Zhao P Y, Zhang X N, Zhang Y, Liu Y M. (2024). Three-dimensional electro-Fenton system with iron-carbon packing as a particle electrode for nitrobenzene wastewater treatment. Frontiers of Environmental Science & Engineering, 18(11): 138

[35] Wang D J, Su C M, Zhang W, Hao X Z, Cang L, Wang Y J, Zhou D M. (2014). Laboratory assessment of the mobility of water-dispersed engineered nanoparticles in a red soil (Ultisol). Journal of Hydrology, 519: 1677–1687

[36] Wang F F, Wu Y, Gao Y, Li H, Chen Z L. (2016). Effect of humic acid, oxalate and phosphate on Fenton-like oxidation of microcystin-LR by nanoscale zero-valent iron. Separation and Purification Technology, 170: 337–343

[37] Wang H, Zhuang M, Shan L, Wu J, Quan G X, Cui L Q, Zhang Y H, Yan J L. (2022). Bimetallic FeNi nanoparticles immobilized by biomass-derived hierarchically porous carbon for efficient removal of Cr(VI) from aqueous solution. Journal of Hazardous Materials, 423: 127098

[38] Wang J J, Tang L, Zeng G M, Deng Y C, Liu Y N, Wang L L, Zhou Y Y, Guo Z, Wang J J, Zhang C. (2017). Atomic scale g-C₃N₄/Bi₂WO₆ 2D/2D heterojunction with enhanced photocatalytic degradation of ibuprofen under visible light irradiation. Applied Catalysis B: Environmental, 209: 285–294

[39] Wang M, Tian D, Tian P P, Yuan L J. (2013). Synthesis of micron-SiO₂@nano-Ag particles and their catalytic performance in 4-nitrophenol reduction. Applied Surface Science, 283: 389–395

[40] Wang W, Zhou M H. (2010). Degradation of trichloroethylene using solvent-responsive polymer coated Fe nanoparticles. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 369(1−3): 232–239

[41] Wang X H, Lin A Y C. (2012). Phototransformation of cephalosporin antibiotics in an aqueous environment results in higher toxicity. Environmental Science & Technology, 46(22): 12417–12426

[42] Wang Y R, Tian D F, Chu W, Li M R, Lu X W. (2019). Nanoscaled magnetic CuFe₂O₄ as an activator of peroxymonosulfate for the degradation of antibiotics norfloxacin. Separation and Purification Technology, 212: 536–544

[43] Wang Z R, Jang H M. (2022). Comparative study on characteristics and mechanism of levofloxacin adsorption on swine manure biochar. Bioresource Technology, 351: 127025

[44] Weng X L, Chen Z X, Chen Z L, Megharaj M, Naidu R. (2014a). Clay supported bimetallic Fe/Ni nanoparticles used for reductive degradation of amoxicillin in aqueous solution: characterization and kinetics. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 443: 404–409

[45] Weng X L, Lin S, Zhong Y H, Chen Z L. (2013). Chitosan stabilized bimetallic Fe/Ni nanoparticles used to remove mixed contaminants-amoxicillin and Cd (II) from aqueous solutions. Chemical Engineering Journal, 229: 27–34

[46] Weng X L, Sun Q, Lin S, Chen Z L, Megharaj M, Naidu R. (2014b). Enhancement of catalytic degradation of amoxicillin in aqueous solution using clay supported bimetallic Fe/Ni nanoparticles. Chemosphere, 103: 80–85

[47] Wu H W, Feng Q Y. (2017). Fabrication of bimetallic Ag/Fe immobilized on modified biochar for removal of carbon tetrachloride. Journal of Environmental Sciences, 54: 346–357

[48] Wu H W, Feng Q Y, Yang H, Alam E, Gao B, Gu D M. (2017). Modified biochar supported Ag/Fe nanoparticles used for removal of cephalexin in solution: characterization, kinetics and mechanisms. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 517: 63–71

[49] Xia J, Shen Y H, Zhang H J, Hu X, Mian M M, Zhang W H. (2022). Synthesis of magnetic nZVI@biochar catalyst from acid precipitated black liquor and Fenton sludge and its application for Fenton-like removal of rhodamine B dye. Industrial Crops and Products, 187: 115449

[50] Xie P C, Ma J, Liu W, Zou J, Yue S Y, Li X C, Wiesner M R, Fang J Y. (2015). Removal of 2-MIB and geosmin using UV/persulfate: contributions of hydroxyl and sulfate radicals. Water Research, 69: 223–233

[51] Xu K, Ben W W, Ling W C, Zhang Y, Qu J H, Qiang Z M. (2017). Impact of humic acid on the degradation of levofloxacin by aqueous permanganate: kinetics and mechanism. Water Research, 123: 67–74

[52] Xu Z H, Sun Z H, Zhou Y W, Zhang D F, Gao Y Q, Huang Y X, Chen W F. (2020). Enhanced hydrodechlorination of p-chloronitrobenzene by a GAC-Fe-Cu ternary micro-electrolysis system: synergistic effects and removal mechanism. Separation and Purification Technology, 237: 116391

[53] Yan W L, Lien H L, Koel B E, Zhang W X. (2013). Iron nanoparticles for environmental clean-up: recent developments and future outlook. Environmental Science-Processes & Impacts, 15(1): 63–77

[54] Zhang L Z, Zhou Z J, Chen Z L, Li W B, Huang M M. (2025). High-temperature carbothermal synthesis of activated carbon-supported nano zero-valent iron and nanosilver composite and its performance for removal of As(Ⅲ). Journal of Industrial and Engineering Chemistry, 142: 237–252

[55] Zhang M H, Dong H, Zhao L, Wang D X, Meng D. (2019). A review on Fenton process for organic wastewater treatment based on optimization perspective. Science of the Total Environment, 670: 110–121

[56] Zhang Q Q, Ying G G, Pan C G, Liu Y S, Zhao J L. (2015). Comprehensive evaluation of antibiotics emission and fate in the river basins of China: source analysis, multimedia modeling, and linkage to bacterial resistance. Environmental Science & Technology, 49(11): 6772–6782

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