Effects of different dissolved organic matter on peroxymonosulfate activation over Co-Fe binary metal: Experiments and density functional theory

Abstract

The role of dissolved organic matter (DOM) on sulfate radical (SO4•−)-mediated advanced oxidation processes (AOPs) remains poorly studied. In this work, we systematically investigated the effects of hydrochar-derived DOM (hyDOM), humic acid (HA), and fulvic acid (FA) on peroxymonosulfate (PMS) activation over Co-Fe bimetallic catalysts (CoFeO). The results showed that the functional groups and surface oxygen vacancies of CoFeO composite were increased after compounding with DOM, which could provide more reactive sites for catalytic reaction and improve the electronic conductivity. More importantly, hydroxyl groups of the loading humic acid-like compounds on hyDOM-CoFeO and FA-CoFeO composites could accelerate the reduction of Co(III) and Fe(III), thus enhancing the PMS activation greatly. Not surprisingly, the degradation efficiency for 10 mg L−1 Bisphenol A (BPA) in PMS activation by composites within 10 min followed the order: FA-CoFeO > hyDOM-CoFeO > HA-CoFeO, and the kinetics constant (k) was 3.6, 2.6, and 8.2 times higher than that of CoFeO composite, respectively. The electron paramagnetic resonance (EPR) and quenching experiments indicated that more reactive oxygen species (ROS) were generated after compounding DOM, and SO4•− was the dominant ROS in the degradation process. Furthermore, the LC-MS analysis and density functional theory (DFT) calculation were conducted to prove the proposed degradation pathways of BPA. Our work is expected to clarify the effects of DOM on Co-Fe bimetallic catalysts/PMS system for environmental remediation.