Coupling the effect of Co and Mo on peroxymonosulfate activation for the removal of organic pollutants

Although heterogeneous cobalt-based catalysts have been widely studied and used in SO₄^•- based advanced oxidation processes, the efficiencies were still not high enough due to the limiting step of Co(III)/Co(II) cycle in the system. In this study, a bimetallic oxide composed of Co and Mo was designed and used for enhancing the performance of peroxymonosulfate activation on organic pollutants removal. The CoMoO₄ nanorods exhibited superior catalytic activity for methylene blue (MB) degradation than Co₃O₄, MoO₃, and their mechanical mixture, which was attributed to the synergetic effect between Co and Mo. CoMoO₄ nanorods were able to efficiently degrade MB under a wide pH range of 3-11 and could maintain high efficiency in 5 cycles with less leakage of metal ions. Moreover, CoMoO₄ nanorods displayed broad spectrum applicability to the different water matrix and a variety of pollutants such as phenol and Congo red. The Co(II) was proved to be the main active site of the catalyst, while Mo played an important role in promoting the Co(III)/Co(II) cycle. Surface free radicals are the main active species in the degradation process. This work provides new insights into the design of cobalt-based bimetallic catalyst and the improvement on PMS activation.