Boron and nitrogen hydrothermal co-doped sludge biochar towards efficiently activate peroxymonosulfate for sulfamethoxazole degradation

Abstract

Designing efficient catalyst for peroxymonosulfate (PMS) activation is beneficial for eliminating the adverse effects of sulfamethoxazole (SMX) on human health. A novel boron (B) and nitrogen (N) co-doped sludge biochar (BNSBC) was synthesized by one-pot hydrothermal activation, and its remarkable PMS activation performance facilitated the rapid elimination of SMX from water. The degradation rate of SMX by BNSBC/PMS system could reach 92.1% within 60 min ([SMX]0 = 10 mg/L, [BNSBC]0 = 0.4 g/L, [PMS]0 = 1 mM). B and N exhibited the synergistic enhancement effects on the physico-chemical characteristics of SBC, and abundant pores, defects, CO, -O-B-O-, graphitic-N and pyridinic N were confirmed as the main active sites of BNSBC for PMS activation. Characterization, quenching, electron paramagnetic resonance (EPR) and electrochemical tests proved that non-radicals of surface-bound, 1O2 and electron transfer were the main contributors to SMX degradation. The high anti-interference of BNSBC/PMS system to pH range, co-existing inorganic anions and organic matter guaranteed its outstanding purification performance for SMX in diverse environmental waters. Four potential degradation pathways of SMX in BNSBC/PMS system were proposed by its intermediates identification and density functional theory (DFT) calculation, and pathway Ⅳ was the main one. The toxicity levels of its intermediates were lower than that of SMX regardless of chronic and acute toxicity. Also, BNSBC/PMS system exhibited the board-spectrum removal performance for other typical antibiotics (e.g., sulfadiazine (SDZ), sulfamethoxypyridazine (SMP), ciprofloxacin (CIP), tetracycline (TC)). BNSBC/PMS has great application potential for eliminating diverse antibiotics in actual wastewater due to its high tolerance to complex environmental conditions and outstanding detoxification ability, also it offers a harmless disposal approach for sludge.