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CuCoFe-LDO/BCD was successfully synthesized from CuCoFe-LDH and biochar derived from durian shell (BCD). Ciprofloxacin (CFX) degraded more than 95% mainly by O 2 •− and 1O 2 in CuCoFe-LDO/BCD(2/1)/PMS system within 10 min with a rate constant of 0.255 min−1, which was 14.35 and 2.66 times higher than those in BCD/PMS and CuCoFe-LDO/PMS systems, respectively. The catalytic system exhibited good performance over a wide pH range (3–9) and high degradation efficiency of other antibiotics. Built-in electric field (BIEF) driven by large difference in the work function/Fermi level ratio between CuCoFe-LDO and BCD accelerated continuous electron transfer from CuCoFe-LDO to BCD to result in two different microenvironments with opposite charges at the interface, which enhanced PMS adsorption and activation via different directions. As a non-radical, 1O 2 was mainly generated via PMS activation by C=O in BCD. The presence of C=O in BCD resulted in an increase in atomic charge of C in C=O and redistributed the charge density of other C atoms. As a result, strong adsorption of PMS at C atom in C=O and other C with a high positive charge was favorable for 1O 2 generation, whereas an enhanced adsorption of PMS at negatively charged C accounted for the generation of •OH and SO 4 •−. After adsorption, electrons in C of BCD became deficient and were fulfilled with those transferred from CuCoFe-LDO driven by BIEF, which ensured the high catalytic activity of CuCoFe-LDO/BCD. O 2 •−, on the other hand, was generated via several pathways that involved in the transformation of •OH and SO 4 •− originated from PMS activation by the transition of metal species in CuCoFe-LDO and negatively charged C in BCD. This study proposed a new idea of fabricating a low-cost metal-LDH and biomass-derived catalyst with a strong synergistic effect induced by BIEF for enhancing PMS activation and antibiotic degradation. [Display omitted] • Durian peel-derived biochar enhances CFX degradation in CuCoFe-LDO/BCD/PMS by 1.48 times. • The role of C=O in BCD for PMS activation and 1O 2 generation is confirmed by DFT calculations. • A new pathway for 1O 2 generation via PMS activation by C=O is proposed. • Built-in electric field between CuCoFe-LDO and BCD accelerates electron transfer and enhances PMS activation. • CFX degradation is contributed mainly by both radical (O 2 •−) and non-radical (1O 2). [ABSTRACT FROM AUTHOR]

[Display omitted] • Boosted PMS activation is achieved by N, S co-doped durian peel-derived biochars (N,S-BCD-X) • N and S raise the ESP and redistribute the electron density in the doping sites of BCD. • Electron-donating capability is enhanced by N&S doping-induced decrease of work function. • 1O 2 is generated via different ways, enhanced by •OH and SO 4 •− due to elongated O-O bond of PMS. • S site in N,S-BCD-800 exhibits the strongest PMS adsorption with the most electron transferred. Biochar is an environmentally friendly material with various potential applications in water treatment. Herein, nitrogen and sulfur co-doped biochars (N,S-BCD-X) were fabricated from durian peel as an agricultural waste by coupling with thiourea via thermal treatment to activate peroxymonosulfate (PMS) for degradation of ofloxacin (OFX) in water. The OFX removal using PMS activated by N,S-BCD-800 was over 85 % after 120 min of reaction, which was 17.78 times higher than that by pure BCD. The OFX degradation was not inhibited over a wide pH range of 3 to 9. Through radical quenching tests, electron paramagnetic resonance, and DFT calculations, 1O 2 was revealed as the key reactive species in the N,S-BCD-800/PMS system because of PMS's elongated O-O bond-induced promoted generation of •OH and SO 4 •- with an insignificant contribution and the generation of 1O 2 via various reactions associated with •OH, SO 4 •-, and PMS. The boosted catalytic activity of N,S-BCD-800 mainly came from synergetic effect of N and S co-doping due to the enhanced electron-donating capability caused by decrease in the work function. Furthermore, the increase in electrostatic potential and the difference in electron density and atomic charge could also account for stronger adsorption and activation of PMS on N,S-BCD-800 to generate more 1O 2 besides the N,S-BCD-800/PMS complex as a minor species responsible for the degradation of OFX via electron transfer. Finally, the attainment of high efficiency of N,S-BCD/PMS for OFX degradation in various water matrices as well as after 5 cycles proved that N,S-BCD had high stability and applicability. [ABSTRACT FROM AUTHOR]