Collaborative modification strategy to improve the formation of biochar-derived persistent free radicals for aniline removal via peroxymonosulfate activation

Abstract

This study explores a novel approach to biochar modification aimed at increasing persistent free radical (PFR) formation on biochar surfaces, thereby enhancing aniline removal via peroxymonosulfate (PMS) activation. By adjusting pyrolysis temperatures and doping ratios, optimal conditions were established. Spearman's analysis highlighted the importance of C=C bonds, the I_D/I_G ratio, and pyridinic N in generating PFRs. The modified biochar derived at 500 ℃ (MB500), in conjunction with the PMS system demonstrated impressive efficiency, achieving 92% aniline removal within 30 min. Detailed adsorption tests and active species detection indicated that aniline degradation occurred through both direct oxidation by PFRs and indirect oxidation by reactive species, particularly superoxide radicals (O₂⋅⁻). Furthermore, the synergistic effects of heteroatom nitrogen and Na₂CO₃ modifications significantly impacted PFR formation and stability. These findings provide valuable insights into the mechanisms of PFR-mediated catalytic oxidation, highlighting the key roles of pyridinic rings, with or without oxygenated groups, in enhancing catalytic performance of biochar. This research advances the understanding of biochar surface chemistry and presents an effective strategy for developing high-performance biochar-based catalysts for environmental remediation, addressing the limitations of unmodified biochar through targeted surface modifications.

Graphical Abstract

References

[1] Bi D, Huang F, Jiang M, He Z, Lin X. Effect of pyrolysis conditions on environmentally persistent free radicals (EPFRs) in biochar from co-pyrolysis of urea and cellulose. Sci Total Environ, 2022, 805: 150339.

[2] Chen D, Xu J, Ling P, Fang Z, Re Q, Xu K, Jiang L, Wang Y, Su S, Hu S, Xiang J. Formation and evolution mechanism of persistent free radicals in biochar during biomass pyrolysis: Insights from biochar’s element composition and chemical structure. Fuel, 2024, 357: 129910.

[3] Ding D, Yang S, Qian X, Chen L, Cai T. Nitrogen-doping positively whilst sulfur-doping negatively affect the catalytic activity of biochar for the degradation of organic contaminant. Appl Catal B: Environ, 2020, 263: 118348.

[4] Hu W, Tan J, Pan G, Chen J, Chen Y, Xie Y, Wang Y, Zhang Y. Direct conversion of wet sewage sludge to carbon catalyst for sulfamethoxazole degradation through peroxymonosulfate activation. Sci Total Environ, 2020, 728: 138853.

[5] Hu S, Liu C, Bu H, Chen M, Fei Y. Efficient reduction and adsorption of Cr(VI) using FeCl₃ -modified biochar: synergistic roles of persistent free radicals and Fe(II). J Environ Sci, 2024, 137: 626-638.

[6] Huang W, Xiao S, Zhong H, Yan M, Yang X. Activation of persulfates by carbonaceous materials: a review. Chem Eng J, 2021, 418: 129297.

[7] Huang F, Bi D, Liu S, Yi W, Zhang J, Yao D. Formation and regulation of environmentally persistent free radicals in biochar and removal of diethyl-phthalate in water. J Anal Appl Pyrolysis, 2022, 168: 105770.

[8] Li D, Duan X, Sun H, Kang J, Zhang H, Tade M, Wang S. Facile synthesis of nitrogen-doped graphene via low-temperature pyrolysis: the effects of precursors and annealing ambience on metal-free catalytic oxidation. Carbon, 2017, 115: 649-658.

[9] Lin X, Chen X, Fu P, Tang B, Bi D. Highly efficient production of monocyclic aromatics from catalytic co-pyrolysis of biomass and plastic with nitrogen-doped activated carbon catalyst. Chem Eng J, 2023, 474: 145783.

[10] Liu B, Guo W, Wang H, Si Q, Zhao Q, Luo H, Ren N. Activation of peroxymonosulfate by cobalt-impregnated biochar for atrazine degradation: the pivotal roles of persistent free radicals and ecotoxicity assessment. J Hazard Mater, 2020, 398: 122768.

[11] Liu T, Cui K, Li C-X, Chen Y, Wang Q, Yuan X, Chen Y, Liu J, Zhang Q. Efficient peroxymonosulfate activation by biochar-based nanohybrids for the degradation of pharmaceutical and personal care products in aquatic environments. Chemosphere, 2023, 311: 137084.

[12] Liu F, Ding J, Zhao Q, Zhao G, Wang K, Li L, Guan S. Insight into the self-driven O₂ activation and interfacial electron transfer for micropollutant degradation by boron-doped biochar: role of boron moieties and persistent free radicals. Sep Purif Technol, 2024, 330: 125444.

[13] Liu X, Chen Z, Lu S, Shi X, Qu F, Cheng D, Wei W, Shon H-K, Ni B-J. Persistent free radicals on biochar for its catalytic capability: a review. Water Res, 2024, 250: 120999.

[14] Luo K, Yang Q, Pang Y, Wang D, Li X, Lei M, Huang Q. Unveiling the mechanism of biochar-activated hydrogen peroxide on the degradation of ciprofloxacin. Chem Eng J, 2019, 374: 520-530.

[15] Luo K, Pang Y, Wang D, Li X, Wang L, Lei M, Huang Q, Yang Q. A critical review on the application of biochar in environmental pollution remediation: role of persistent free radicals (PFRs). J Environ Sci, 2021, 108: 201-216.

[16] Qi Y, Ge B, Zhang Y, Jiang B, Wang C, Akram M, Xu X. Three-dimensional porous graphene-like biochar derived from Enteromorpha as a persulfate activator for sulfamethoxazole degradation: role of graphitic N and radicals transformation. J Hazard Mater, 2020, 399: 123039.

[17] Ruan X, Sun Y, Du W, Tang Y, Liu Q, Zhang Z, Doherty W, Frost R, Qian G, Tsang D. Formation, characteristics, and applications of environmentally persistent free radicals in biochars: a review. Bioresour Technol, 2019, 281: 457-468.

[18] Suresh S, Srivastava VC, Mishra IM. Studies of adsorption kinetics and regeneration of aniline, phenol, 4-chlorophenol and 4-nitrophenol by activated carbon. Chem Ind Chem Eng Q, 2013, 19(2): 195-212.

[19] Tao W, Duan W, Liu C, Zhu D, Si X, Zhu R, Oleszczuk P, Pan B. Formation of persistent free radicals in biochar derived from rice straw based on a detailed analysis of pyrolysis kinetics. Sci Total Environ, 2020, 715: 136575.

[20] Tao W, Zhang P, Li H, Yang Q, Oleszczuk P, Pan B. Generation mechanism of persistent free radicals in lignocellulose-derived biochar: roles of reducible carbonyls. Environ Sci Technol, 2022, 56: 10638-10645.

[21] Wen Y, Liu L, He D, Wu J, Yang W, Li S, Wang S, Shu L, Zhou Z, Zhou Z, Zhou N. Highly graphitized biochar as nonmetallic catalyst to activate peroxymonosulfate for persistent quinclorac removal in soil through both free and non-free radical pathways. Chem Eng J, 2024, 480: 148082.

[22] Wu W, Zhu S, Huang X, Wei W, Jin C, Ni B-J. Determination of instinct components of biomass on the generation of persistent free radicals (PFRs) as critical redox sites in pyrogenic chars for persulfate activation. Environ Sci Technol, 2021, 55: 7690-7701.

[23] Xie J, Latif J, Yang K, Wang Z, Zhu L, Yang H, Qin J, Ni Z, Jia H, Xin W, Li X (2024) A state-of-art review on the redox activity of persistent free radicals in biochar. Water Res 255:121516. https://doi.org/10.1016/j.watres.2024.121516

[24] Yan Y, Ma X, Cao W, Zhang X, Zhou J, Liu Q, Qian G. Identifying the reducing capacity of biomass derived hydrochar with different post-treatment methods. Sci Total Environ, 2018, 643: 486-495.

[25] Yang J, Pan B, Li H, Liao S, Zhang D, Wu M, Xing B. Degradation of p-nitrophenol on biochars: role of persistent free radicals. Environ Sci Technol, 2016, 50: 694-700.

[26] Yu S, Wang X, Ai Y, Tan X, Hayat T, Hu W, Wang X. Experimental and theoretical studies on competitive adsorption of aromatic compounds on reduced graphene oxides. J Mater Chem A, 2016, 4: 5654-5662.

[27] Yu S, Wang X, Chen Z, Wang J, Wang S, Hayat T, Wang X. Layered double hydroxide intercalated with aromatic acid anions for the efficient capture of aniline from aqueous solution. J Hazard Mater, 2017, 321: 111-120.

[28] Yu W, Lian F, Cui G, Liu Z. N-doping effectively enhances the adsorption capacity of biochar for heavy metal ions from aqueous solution. Chemosphere, 2018, 193: 8-16.

[29] Yu J, Zhu Z, Zhang H, Shen X, Qiu Y, Yin D, Wang S. Persistent free radicals on N-doped hydrochar for degradation of endocrine disrupting compounds. Chem Eng J, 2020, 398: 125538.

[30] Yu C, Xing J, Xu K, Chen S. Enhanced adsorption of micropollutants on oxygen plasma-modified carbon nanotubes (O-CNTs) under electrochemical assistance. J Water Process Eng, 2024, 58: 104854.

[31] Yuan J, Wen Y, Dionysiou DD, Sharma VK, Ma X. Biochar as a novel carbon-negative electron source and mediator: electron exchange capacity (EEC) and environmentally persistent free radicals (EPFRs): a review. Chem Eng J, 2022, 429: 132313.

[32] Zhang Y, Xu M, He R, Zhao J, Kang W, Lv J. Effect of pyrolysis temperature on the activated permonosulfate degradation of antibiotics in nitrogen and sulfur-doping biochar: key role of environmentally persistent free radicals. Chemosphere, 2022, 294: 133737.

[33] Zhang Z, Yang R, Zheng Y, Bai H, Shi J, Zhang J, Zhou X, Cai M, Fan S, Li C. Graphene oxide-Fe₃O₄ nanocomposite used as aniline adsorbent with a wide pH range. Colloid Polym Sci, 2022, 300: 83-93.

[34] Zhang R, Zhang R, Zimmerman A, Wang H, Gao B. Applications, impacts, and management of biochar persistent free radicals: a review. Environ Pollut, 2023, 327: 121543.

[35] Zhang J, Liu S, Huang F, Bi D, Song J, Chou S. Coupled effects of Fenton-like systems with different concentrations of H₂O₂/Biochar on diethyl phthalate removal: dominant role of environmental persistent free radicals (EPFRs). Environ Pollut, 2024, 385: 124499.

[36] Zhao C, Shao B, Yan M, Liu Z, Liang Q, He Q, Wu T, Liu Y, Pan Y, Huang J, Wang J, Liang J, Tang L. Activation of peroxymonosulfate by biochar-based catalysts and applications in the degradation of organic contaminants: a review. Chem Eng J, 2021, 416: 128829.

[37] Zhu S, Huang X, Ma F, Wang L, Duan X, Wang S. Catalytic removal of aqueous contaminants on N-doped graphitic biochars: inherent roles of adsorption and nonradical mechanisms. Environ Sci Technol, 2018, 52: 8649-8658.

[38] Zhu S, Huang X, Yang X, Peng P, Li Z, Jin C. Enhanced transformation of Cr(VI) by heterocyclic-N within nitrogen-doped biochar: impact of surface modulatory persistent free radicals (PFRs). Environ Sci Technol, 2020, 54: 8123-8132.

[39] Zhu Y, Wei J, Li J. Biochar-activated persulfate oxidation of arsenic(III): nonnegligible roles of environmentally persistent free radicals. J Environ Chem Eng, 2023, 11: 111033.

Funding

Science, Technology and Innovation Commission of Shenzhen Municipality(GXWD20231130102759003)

National Natural Science Foundation,(42177044)

RIGHTS & PERMISSIONS

The Author(s)