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

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 NiCoO 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 (NiCoO) is investigated in a PMS/carbonate (PC) system for Orange II degradation. The observed pseudo-first-order rate constants (k) were assessed by the effects of different water matrices and operation conditions. The results show that k with NiCoO were increased by 13 times than that of treatment without NiCoO. This was mainly due to Co and Ni act as electron acceptors to capture electrons from the PMS/PC system, forming a good redox cycle with HSO/SO and oxidizing Co/Ni to produce a large amount of more active components (e.g., O and SO). The good reusability and high stability of NiCoO were demonstrated by five recycle tests. These results suggest that the NiCoO/PC system is an efficient and stable method of pollution remediation.