Synergistic enhancement of redox pairs and functional groups for the removal of phenolic organic pollutants by activated PMS using silica-composited biochar: Mechanism and environmental toxicity assessment

Abstract

In present work, a novel catalyst of cobalt supported on silica-composited biochar (Co@ACFA-BC) derived from fly ash and agricultural waste was synthesized. A series of characterizations confirmed that Co3O4 and Al/Si–O compounds were successfully embedded on the surface of biochar, which triggered superior catalytic activity for PMS activation towards phenol degradation. Particularly, the Co@ACFA-BC/PMS system could completely degrade phenol in the wide pH range, and was almost unaffected by environmental factors including humic acid (HA), H2PO4−, HCO3−, Cl−, and NO3−. Further quenching experiment and EPR analysis proved that both radical (SO4·-, ·OH, O2·-) and non-radical (1O2) pathways were involved in the catalytic reaction system, and the excellent PMS activation was attributed to the electron pair cycling of Co2+/Co3+ and the active sites provided by Si–O–O and Si/Al–O bonds on the catalyst surface. Meanwhile, the carbon shell effectively inhibited the leaching of metal ions, enabling the Co@ACFA-BC catalyst to maintain excellent catalytic activity after four cycles. Finally, biological acute toxicity assay demonstrated that the toxicity of phenol could be significantly reduced after being treated by Co@ACFA-BC/PMS. Overall, this work provides a promising strategy for solid waste valorization and a feasible methodology for green and efficient treatment of refractory organic pollutants in water environment.