Rapid removal of ofloxacin with peroxymonosulfate activation process mediated by Co3O4/Sludge-derived biochar composite: Unveiling the enhancement of biochar

Abstract

In this study, sludge-derived biochar loaded Co3O4 composite (Co3O4@SDBC) were successfully synthesized through cobalt impregnation and secondary calcination of sludge-derived biochar precursors. The experimental results demonstrated that the Co3O4@SDBC catalyst performed exceptionally well for peroxymonosulfate (PMS) activation, with a high degradation efficiency (>99 %) of ofloxacin (OFL) within 10 min under the optimal conditions (a catalyst dose of 0.10 g•L−1, a PMS dose of 0.975 mM and an initial pH = 6.4), and showed good adaptability across a broad pH spectrum, under the interference of the anions and humic acid (HA), as well as in various water matrices. The results of quenching experiments revealed that the non-radical pathway (especially 1O2 and electron transfer) was the dominated reactive ingredients in the PMS activation process induced by Co3O4@SDBC. Notably, the online electrochemical tests and density functional theory (DFT) results indicated the presence of biochar carrier not only effectively lowered the escape of Co ions, while enhanced the steadiness of Co3O4@SDBC, but also accelerated the electron transfer, promoted the adsorption and cleavage of PMS, facilitated the redox cycle between Co(II) and Co(III), reduced the reaction energy barriers simultaneously, thereby making it more favourable for the generation of 1O2. Furthermore, the toxicity assessment suggested that the cumulative toxicity of OFL decreased throughout degradation. Overall, this work mechanistically revealed the enhancement of biochar on the Co3O4@SDBC catalyst, offering a viable method to activate PMS for antibiotic removal and achieving a mutually beneficial strategy for sludge waste resource utilization and environmental remediation.