Optimization of the catalytic activity of a ZnCo2O4 catalyst in peroxymonosulfate activation for bisphenol A removal using response surface methodology

An effective peroxymonosulfate activator, ZnCo2O4, 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 ZnCo2O4 catalyst were analyzed with various equipments. The results show that the ZnCo2O4 nanosheets are cubic crystals with a spinel structure and a high surface area of 105.90 m2‧g-1. Under the conditions of [ZnCo2O4] = 0.2 g‧L-1 and [PMS]/[BPA]molar = 2.0, the bisphenol A degradation efficiency reaches 99.28% within 5 min in the ZnCo2O4/PMS system. ZnCo2O4 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 SO4- and OH play vital roles during the degradation process.