Sustainable removals of antibiotics via biochar-enhanced ultrasound cavitation effect: synergy of carbon nanotube bonded biochar@Fe₃C composite and low frequency energy efficiency

Abstract

The recalcitrant antibiotics of enrofloxacin (ENT) and amoxicillin (AMT) were difficult to remove by conventional sonication. To address this challenge, a new type of carbon nanotube covalently bonded biochar@Fe₃C composite (BCM@Fe) was first designed by calcination and employed as a solid cavitation material (SCM) under low-frequency ultrasound (US) conditions to accelerate the removals of ENT and AMT. Compared to conventional carbon nanotube@Fe₃C composites, BCM@Fe demonstrated significantly improved removal performance, achieving 15.5-fold and 3.50-fold higher removal rates for ENT and AMT, respectively. The removal efficiencies increased by 32.1–32.3% compared with a conventional shake system. Mechanistic studies revealed a dual removal mechanism involving simultaneous adsorption and degradation. The coupling of low-frequency ultrasound with BCM@Fe had synergistic effects; the US promoted the dispersion of the composites and inhibited H₂O-induced oxidation by generating surface-localized cavitation bubbles. Notably, BC in BCM@Fe was found to amplify cavitation effect with performance strongly correlated with material characteristics such as pH, carbonization degree, aromaticity, hydrophobicity, and graphitization. Degradation differed between antibiotics: the degradation of ENT predominantly occurred at the material surface, while that of AMT took place in the liquid phase. Overall, the successful access to low-cost SCM integrating with low-frequency ultrasound made the possible for potential application in antibiotic wastewater.

Keywords

Biochar / Solid cavitation material / Antibiotics degradation / Low-frequency ultrasound / Cavitation effect

References

[1] Bergamonti L, Bergonzi C, Graiff C, Lottici PP, Bettini R, Elviri L. 3D printed chitosan scaffolds: a new TiO₂ support for the photocatalytic degradation of amoxicillin in water. Water Res, 2019, 163: 114841

[2] Çakmakçı N, Yoo B, Lee H, Jeong Y. Assessment of carbon nanotube sheet densification level. Carbon Lett, 2024, 34: 1239-1245

[3] Chen Z, Wannere CS, Corminboeuf C, Puchta R, Schleyer PVR. Nucleus-Independent Chemical Shifts (NICS) as an Aromaticity Criterion. Chem Rev, 2005, 105: 3842-3888

[4] Chen F, Ma M, Wang J, Wang F, Chern S, Zhao ER, Jhunjhunwala A, Darmadi S, Chen H, Jokerst JV. Exosome-like silica nanoparticles: a novel ultrasound contrast agent for stem cell imaging. Nanoscale, 2017, 9: 402-411

[5] Chong S, Zhang G, Zhang N, Liu Y, Huang T, Chang H. Diclofenac degradation in water by FeCeOx catalyzed H₂O₂: influencing factors, mechanism and pathways. J Hazard Mater, 2017, 334: 150-159

[6] Cui H, Zhan W, Ji X, Jiang M, Wu X, Huang M, Huang C, Ma S. Removal of sulfonamide antibiotics by a sonocatalytic fenton-like reaction: efficiency and mechanisms. Environ Res, 2023, 239: 117408

[7] De Visscher A, Van Eenoo P, Drijvers D, Van Langenhove H. Kinetic model for the sonochemical degradation of monocyclic aromatic compounds in aqueous solution. J Phys Chem, 1996, 100: 11636-11642

[8] Dehghan S, Kakavandi B, Kalantary RR. Heterogeneous sonocatalytic degradation of amoxicillin using ZnO@Fe₃O₄ magnetic nanocomposite: influential factors, reusability and mechanisms. J Mol Liq, 2018, 264: 98-109

[9] Dou M, Wang J, Gao B, Xu C, Yang F. Photocatalytic difference of amoxicillin and cefotaxime under visible light by mesoporous g-C3N4: mechanism, degradation pathway and DFT calculation. Chem Eng J, 2020, 383: 123134

[10] Evich MG, Davis MJB, Mccord JP, Acrey B, Awkerman JA, Knappe DRU, Lindstrom BL, Speth TF, Tebes C, Stpynar MJ, Wang Z, Weber EJ, Henderson WM, Washington JW. Per- and polyfluoroalkyl substances in the environment. Science, 2022, 375: 6580

[11] Farshbaf Aghajani P, Soltani Firouz M, Alikhani Chamgordani P. The improvement of freezing time and functional quality of frozen mushrooms by application of probe-type power ultrasound. Ultrason Sonochem, 2023, 100: 106637

[12] Flint EB, Suslick KS. The temperature of cavitation. Science, 1991, 253: 1397-1399

[13] Fontana RJ, Shakil AO, Gerrnson JK, Boyd I, Lee WM. Acute liver failure due to amoxicillin and amoxicillin/clavulanate. Dig Dis Sci, 2005, 50: 1785-1790

[14] Francisco PCM, Mitsui S, Ishidera T, Tachi Y, Doi R, Shiwaku H. Interaction of FeII and Si under anoxic and reducing conditions: structural characteristics of ferrous silicate co-precipitates. Geochim Cosmochim Acta, 2020, 270: 1-20

[15] Geng C, Chen Q, Li Z, Liu M, Chen Z, Tao H, Yang Q, Zhu B, Feng L. Degradation of enrofloxacin by a novel Fe–N–C@ZnO material in freshwater and seawater: performance and mechanism. Environ Res, 2023, 237: 116960

[16] Gholami M, Rahmani K, Rahmani A, Rahmani H, Esrafili A. Oxidative degradation of clindamycin in aqueous solution using nanoscale zero-valent iron/H₂O₂/US. Desalin Water Treat, 2016, 57: 13878-13886

[17] Goel M, Hongqiang H, Mujumdar AS, Ray MB. Sonochemical decomposition of volatile and non-volatile organic compounds—a comparative study. Water Res, 2004, 38: 4247-4261

[18] Grilla E, Vakros J, Konstantinou I, Manariotis ID, Mantzavinos D. Activation of persulfate by biochar from spent malt rootlets for the degradation of trimethoprim in the presence of inorganic ions. J Chem Technol Biotechnol, 2020, 95: 2348-2358

[19] Gutiérrez M, Henglein A, Fischer CH. Hot spot kinetics of the sonolysis of aqueous acetate solutions. Int J Radiat Biol Relat Stud Phys Chem Med, 1986, 50: 313

[20] Hontoria-Lucas C, López-Peinado AJ, López-González JDD, Rojas-Cervantes ML, Martín-Aranda RM. Study of oxygen-containing groups in a series of graphite oxides: physical and chemical characterization. Carbon, 1995, 33: 1585-1592

[21] Inyang M, Gao B, Zimmerman A, Zhou Y, Cao X. Sorption and cosorption of lead and sulfapyridine on carbon nanotube-modified biochars. Environ Sci Pollut Res, 2015, 22: 1868-1876

[22] Jonnalagadda US, Fan Q, Su X, Liu W, Kwan JJ. Nanostructured sonophotocatalysts for spatially controlled inertial cavitation towards energy-efficient sonochemistry. ChemCatChem, 2022, 14: e202200732

[23] Joseph JM, Destaillats H, Hung H, Hoffmann MR. The sonochemical degradation of azobenzene and related azo dyes: rate enhancements via Fenton's reactions. J Phys Chem A, 2000, 104: 301-307

[24] Karim AV, Shriwastav A. Degradation of amoxicillin with sono, photo, and sonophotocatalytic oxidation under low-frequency ultrasound and visible light. Environ Res, 2021, 200: 111515

[25] Kowalska J, Banach K, Beberok A, Rok J, Rzepka Z, Wrześniok D. The biochemical and molecular analysis of changes in melanogenesis induced by UVA-activated fluoroquinolones—in vitro study on human normal melanocytes. Cells, 2021, 10: 2900

[26] Kwan JJ, Lajoinie G, Stride EP, Versluis M, Coussios C. The induction of inertial cavitation from polymeric nanocups—from theory to observation. J Acoust Soc Am, 2018, 143: 1834

[27] Li H, Zhang D, Han X, Xing B. Adsorption of antibiotic ciprofloxacin on carbon nanotubes: pH dependence and thermodynamics. Chemosphere, 2014, 95: 150-155

[28] Li Z, Li M, Zhang Z, Li P, Zang Y, Liu X. Antibiotics in aquatic environments of China: a review and meta-analysis. Ecotox Environ Safe, 2020, 199: 110668

[29] Li S, Jin W, Jiang H, Zhang H, Kong D, Zhu L. Efficient removal of phenanthrene by covalent organic frameworks: an experimental combined with theoretical analysis. Sep Purif Technol, 2024, 336: 126189

[30] Liu K, Zhao D, Hu Z, Xiao Y, He C, Jiang F, Zhao N, Zhao C, Zhang W, Qiu R. The adsorption and reduction of anionic Cr(VI) in groundwater by novel iron carbide loaded on N-doped carbon nanotubes: effects of Fe-confinement. Chem Eng J, 2023, 452: 139357

[31] Liu P, Wu Z, Fang Z, Cravotto G. Sonolytic degradation kinetics and mechanisms of antibiotics in water and cow milk. Ultrason Sonochem, 2023, 99: 106518

[32] Lu Y, Zhou X, Zheng Y, Yang H, Cao W. How far do we still need to go with antibiotics in aquatic environments? Antibiotic occurrence, chemical-free or chemical-limited strategies, key challenges, and future perspectives. Water Res, 2025, 275: 123179

[33] Luan J, Liu W, Yao Y, Ma B, Niu B, Yang G, Wei Z. Synthesis and property examination of Er₂FeSbO₇/BiTiSbO₆ heterojunction composite catalyst and light-catalyzed retrogradation of enrofloxacin in pharmaceutical waste water under visible light irradiation. Materials, 2022, 15: 5906

[34] Ma W, Wang N, Fan Y, Tong T, Han X, Du Y. Non-radical-dominated catalytic degradation of bisphenol A by ZIF-67 derived nitrogen-doped carbon nanotubes frameworks in the presence of peroxymonosulfate. Chem Eng J, 2018, 336: 721-731

[35] Maguire CM, Rösslein M, Wick P, Prina-Mello A. Characterisation of particles in solution-a perspective on light scattering and comparative technologies. Sci Technol Adv Mat, 2018, 19: 732-745

[36] Meroni D, Djellabi R, Ashokkumar M, Bianchi CL, Boffito DC. Sonoprocessing: from concepts to large-scale reactors. Chem Rev, 2022, 122: 3219-3258

[37] Merouani S, Hamdaoui O, Saoudi F, Chiha M. Sonochemical degradation of Rhodamine B in aqueous phase: effects of additives. Chem Eng J, 2010, 158: 550-557

[38] Peng Z, Xiong C, Wang W, Tan F, Wang X, Qiao X, Wong PK. Hydrophobic modification of nanoscale zero-valent iron with excellent stability and floatability for efficient removal of floating oil on water. Chemosphere, 2018, 201: 110-118

[39] Peng G, Li T, Ai B, Yang S, Fu J, He Q, Yu G, Deng S. Highly efficient removal of enrofloxacin by magnetic montmorillonite via adsorption and persulfate oxidation. Chem Eng J, 2019, 360: 1119-1127

[40] Rahmani H, Gholami M, Mahvi AH, Alimohammadi M, Azarian G, Esrafili A, Rahmani K, Farzadkia M. Tinidazole removal from aqueous solution by sonolysis in the presence of hydrogen peroxide. B Environ Contam Toxicol, 2014, 92: 341-346

[41] Rangraz Y, Heravi MM. Recent advances in metal-free heteroatom-doped carbon heterogonous catalysts. RSC Adv, 2021, 11: 23725-23778

[42] Sapalidis A, Sideratou Z, Panagiotaki KN, Sakellis E, Kouvelos EP, Papageorgiou S, Katsaros F. Fabrication of antibacterial poly(vinyl alcohol) nanocomposite films containing dendritic polymer functionalized multi-walled carbon nanotubes. Front Mater, 2018

[43] Serna-Galvis EA, Celis-Llamoca KP, Collantes-Díaz IE, Torres-Palma RA, Nieto-Juárez JI. Insights into the transformations, antimicrobial activity, and degradation efficiency of a representative carbapenem antibiotic by high-frequency ultrasound hybridized with the (photo) Fenton process. Ultrason Sonochem, 2025, 119: 107379

[44] Shan L, Gao M, Pan X, Li W, Wang J, Li H, Tian H. Association between fluoroquinolone exposure and children's growth and development: a multisite biomonitoring-based study in northern China. Environ Res, 2022, 214: 113924

[45] Singh R, Kim K. Environmental occurrence of antibiotic resistance, control measures and challenges in finding therapeutic management. Emerg Contam, 2025, 11: 100440

[46] Stride E, Coussios C. Nucleation, mapping and control of cavitation for drug delivery. Nat Rev Phys, 2019, 1: 495-509

[47] Sun Y, Yu IKM, Tsang DCW, Cao X, Lin D, Wang L, Graham NJD, Alessi DS, Komárek M, Ok YS, Feng Y, Li X. Multifunctional iron-biochar composites for the removal of potentially toxic elements, inherent cations, and hetero-chloride from hydraulic fracturing wastewater. Environ Int, 2019, 124: 521-532

[48] Tan C, Liu Y, He Y, Luo W, Zhang R, Vijver MG, Peijnenburg WJGM. The relative contributions of complexation, dispersing, and adsorption of tannic acid to the dissolution of copper oxide nanoparticles. Water Air Soil Pollut, 2021, 232: 359

[49] Tang H, Wang Y, Li S, Wu J, Li J, Zhou H, Gao Z. Graphene oxide composites for magnetic solid-phase extraction of twelve quinolones in water samples followed by MALDI-TOF MS. Anal Bioanal Chem, 2019, 411: 7039-7049

[50] Thomas RG, Jonnalagadda US, Kwan JJ. Biomedical applications for gas-stabilizing solid cavitation agents. Langmuir, 2019, 35: 10106-10115

[51] Wada OZ, Olawade DB. Recent occurrence of pharmaceuticals in freshwater, emerging treatment technologies, and future considerations: a review. Chemosphere, 2025, 374: 144153

[52] Wang H, Jiang S, Chen S, Li D, Zhang X, Shao W, Sun X, Xie J, Zhao Z, Zhang Q, Tian Y, Xie Y. Enhanced singlet oxygen generation in oxidized graphitic carbon nitride for organic synthesis. Adv Mater, 2016, 28: 6940-6945

[53] Wang J, Hui X, Liu H, Dai X. Classification, characteristics, harmless treatment and safety assessment of antibiotic pharmaceutical wastewater (APWW): a comprehensive review. Chemosphere, 2024, 366: 143504

[54] Wang Y, Lin Y, He S, Wu S, Yang C. Singlet oxygen: properties, generation, detection, and environmental applications. J Hazard Mater, 2024, 461: 132538

[55] Wu B, Meng H, Morales DM, Zeng F, Zhu J, Wang B, Risch M, Xu ZJ, Petit T. Nitrogen-rich carbonaceous materials for advanced oxygen electrocatalysis: synthesis, characterization, and activity of nitrogen sites. Adv Funct Mater, 2022, 32: 2204137

[56] Xie Z, He C, Pei D, Dong Y, Yang S, Xiong Z, Zhou P, Pan Z, Yao G, Lai B. Review of characteristics, generation pathways and detection methods of singlet oxygen generated in advanced oxidation processes (AOPs). Chem Eng J, 2023, 468: 143778

[57] Yang Z, Qian J, Yu A, Pan B. Singlet oxygen mediated iron-based Fenton-like catalysis under nanoconfinement. Proc Natl Acad Sci, 2019, 116: 6659-6664

[58] Yi C, Shang J, Shen Z, Sun Y, Yang Y, Zheng X, Peng Z, Chen J, Liu Y, Guo R, Liao Q. Distribution and risk characteristics of antibiotics in China surface water from 2013 to 2024. Chemosphere, 2025, 375: 144197

[59] Yu Z, Ma J, Huang X, Lv Y, Liu Y, Lin C, Dou R, Ye X, Shi Y, Liu M. Insights into enhanced peroxydisulfate activation with S doped Fe@C catalyst for the rapid degradation of organic pollutants. J Colloid Interf Sci, 2022, 610: 24-34

[60] Yun E, Lee JH, Kim J, Park H, Lee J. Identifying the nonradical mechanism in the peroxymonosulfate activation process: singlet oxygenation versus mediated electron transfer. Environ Sci Technol, 2018, 52: 7032-7042

[61] Zhang W, Fu Y, Liu W, Lim L, Wang X, Yu A. A general approach for fabricating 3D MFe₂O₄ (M=Mn, Ni, Cu, Co)/graphitic carbon nitride covalently functionalized nitrogen-doped graphene nanocomposites as advanced anodes for lithium-ion batteries. Nano Energy, 2019, 57: 48-56

[62] Zhang S, Zhang S, Rong F, Huang S, Zhao S, Wang M, He L, Zhang Z, Du M. Atomic Fe sites embedded within carbon nanotubes for the efficient photodegradation of multiple tetracyclines. Sep Purif Technol, 2022, 287: 120530

[63] Zhao N, Chang F, Hao B, Yu L, Morel JL, Zhang J. Removal of organic dye by biomass-based iron carbide composite with an improved stability and efficiency. J Hazard Mater, 2019, 369: 621-631

[64] Zhao N, Liu K, He C, Gao J, Zhang W, Zhao T, Tsang DCW, Qiu R. Singlet oxygen mediated the selective removal of oxytetracycline in C/Fe₃C/Fe⁰ system as compared to chloramphenicol. Environ Int, 2020, 143 105899

[65] Zhao N, Zhao C, Liu K, Zhang W, Tsang DCW, Yang Z, Yang X, Yan B, Morel JL, Qiu R. Experimental and DFT investigation on N-functionalized biochars for enhanced removal of Cr(VI). Environ Pollut, 2021, 291: 118244

[66] Zhao N, Tan X, Xiong J, Chen N, Gao J, Wang R, Yang X, Zhang W, Qiu R. Quantitative analysis on the redox conversion mechanism of Cr(VI) and As(III) by iron carbide based biochar composites. Chem Eng J, 2022, 446: 137417

[67] Zhao C, Meng L, Chu H, Wang J, Wang T, Ma Y, Wang C. Ultrafast degradation of emerging organic pollutants via activation of peroxymonosulfate over Fe₃C/Fe@N-C-x: singlet oxygen evolution and electron-transfer mechanisms. Appl Catal B-Environ, 2023, 321: 122034

[68] Zhao J, Yang X, Yang Y, Liu L, Lin Y, Xie L, Chai X, Xu K, Du G, Zhang L. Biomass polyamine-functionalized nanocellulose-loaded covalent organic framework to construct composite aerogels for highly efficient removal of Cr (VI) and methyl orange. Chem Eng J, 2024, 486: 150282

[69] Zhao N, Wang A, Xiao Y, Zhao D, Zhao C, Yin Z, Zhang W, Zhang W, Qiu R, Xing B. Fe crystalline phases in Fe/C composites modulated the selective adsorption of Pb(II) from industrial wastewater with Cd(II): an electronic-scale perspective. Inorg Chem, 2024, 63: 15679-15691

Funding

Key Technologies Research and Development Program(2019YFC1803900)

GDAS'Proiect of Science and Technology Development(2023GDASZH-2023010103)

Natural Science Foundation of Guangdong Province(2023A1515012279)

Science and Technology Program of Guangzhou(202201011177)

Guangdong Foundation for Program of Science and Technology Research(2023B1212060044)

RIGHTS & PERMISSIONS

The Author(s)