Activation of peroxymonosulfate (PMS) by Co3O4 quantum dots decorated hierarchical C@Co3O4 for degradation of organic pollutants: Kinetics and radical-nonradical cooperation mechanisms

Abstract

Persulfate-based advanced oxidation process (PS-AOP) is a promising technology for in-depth wastewater treatment. Here, Co3O4 quantum dots (QDs) decorated hierarchical C@Co3O4 (C@Co3O4-Q5) was prepared by a facile route. The crystalline structure, micrograph and chemical composition of C@Co3O4-Q5 were characterized by XRD, SEM, TEM and XPS. Taking Rhodamine B (RhB) as a model contaminant, the influences of process parameters on the degradation performance were evaluated. Detailed reaction kinetics investigation indicated that, at elevated temperatures higher than 30 °C, RhB degradation rate approximately follows this expression: r=1.022×107exp(-47850/RT)[RhB][PMS]0.36, whereas the real energies for catalytic activation (Eac) and heat activation (Eah) were 16.231 kJ·mol−1 and 31.62 kJ·mol−1, respectively. Reactive oxygen species (ROS) quenching experiments and EPR tests suggested that not the general held radical SO4− but the downstream OH and the nonradical ROS 1O2 co-contribute to RhB mineralization. Meanwhile, PMS activation mechanisms referring to OH and 1O2 generation were elaborated based on XPS discussion. It was revealed that Co3O4 quantum dots and oxygen functional groups and/or oxygen defects on carbon surface cooperate to generate ROS. Additionally, 5 successive cycles confirmed C@Co3O4-Q5′s high stability and reusability. These findings provided new insights into carbon-loaded QDs catalysts for PMS-mediated micropollutants removal.