Optimization of the catalytic activity of a ZnCoO catalyst in peroxymonosulfate activation for bisphenol A removal using response surface methodology.

An effective peroxymonosulfate activator, ZnCoO, was synthesized through a microwave-assisted method. According to response surface methodology (RSM) using Box-Behnken design (BBD), the effects of four parameters, microwave temperature, microwave time, calcination time and calcination temperature, were investigated, and the results show that both the microwave temperature and calcination temperature have a great influence on the catalytic activity during the preparation process. In addition, a quadratic model is valid for computing and predicting the observed responses. The characteristics of the synthesized ZnCoO catalyst were analyzed with various equipments. The results show that the ZnCoO nanosheets are cubic crystals with a spinel structure and a high surface area of 105.90 m‧g. Under the conditions of [ZnCoO] = 0.2 g‧L and [PMS]/[BPA] = 2.0, the bisphenol A degradation efficiency reaches 99.28% within 5 min in the ZnCoO/PMS system. ZnCoO possesses great stability and reusability according to recycling experiments. In addition, the possible active radical species were confirmed through quenching experiments and EPR detection, indicating that surface-bound SO and OH play vital roles during the degradation process.