Coupled radical and nonradical activation of peroxymonosulfate by the piezo-photocatalytic effect of α-SnWO4/ZnO heterojunction to boost the degradation and detoxification of carbamazepine

Abstract

Piezo-photocatalytic processes based on heterogeneous catalysts, by establishing electronic fast track to realize electronic storage and conversion, are proved to be effective ways to improve the efficiency of PMS activation. Herein, α-SnWO4/ZnO catalyst with p-n heterojunction was constructed to testify the piezo-photocatalytic effect on peroxymonosulfate (PMS) activation for pollution control. The decomposition rate of carbamazepine (CBZ) in the piezo-photocatalytic PMS activation process by α-SnWO4/ZnO heterojunction was 12.6 and 5.2 times to that by ZnO and α-SnWO4 processes, respectively. In addition, the total organic carbon (TOC) removal rate of CBZ reached 89%, and TOC in the actual water body was also effectively removed. Free radical quenching and detection experiments showed that nonradicals (1O2) and free radicals (O2−, OH) were the mainly active species of the process, by which the toxicity of the intermediates of CBZ was significantly reduced by the combination of the radical and nonradical pathways through hydroxylation and singlet oxygen oxidation. Furthermore, the influences of the experimental factors, including the initial pH, PMS concentration, temperature and reuse of catalysts on CBZ degradation were evaluated. Notably, the activation energy (Ea) in this work was calculated as 34.2 kJ mol−1, which was lower than that of other reported systems. Overall, this work can scientifically guide the design of high-performance piezo-photocatalysts to use common metals for efficient activation of PMS as economical alternatives over expensive rare metal catalysts for water purification.