A persulfate oxidation system for removing acid orange from aqueous solution: Evaluation and degradation mechanism

Abstract

Peroxymonosulfate-based advanced oxidation (PMS-AOP) is a promising technology for the degradation of environmental pollutants. PMS can be activated by various transition metals, especially cobalt-based catalysts, but pure cobalt catalyst suffers from severe metal leakage and poor cyclicality. This study synthesized NiCo2O4 using a co-precipitation hydrothermal method. The structures, morphologies, and chemical states of the prepared catalysts were hexagonal sheet structures. The activation of PMS by catalyst (NiCo2O4) is investigated in a PMS/carbonate (PC) system for Orange II degradation. The observed pseudo-first-order rate constants (k1) were assessed by the effects of different water matrices and operation conditions. The results show that kobs with NiCo2O4 were increased by 13 times than that of treatment without NiCo2O4. This was mainly due to Co3+ and Ni3+ act as electron acceptors to capture electrons from the PMS/PC system, forming a good redox cycle with HSO5−/SO5− and oxidizing Co2+/Ni2+ to produce a large amount of more active components (e.g., 1O2 and SO4⋅-). The good reusability and high stability of NiCo2O4 were demonstrated by five recycle tests. These results suggest that the NiCo2O4/PC system is an efficient and stable method of pollution remediation.