Controllable synthesis of MnIn2S4 microspheres for piezoelectric degradation of oxytetracycline: Performance and mechanistic insights

Piezoelectric catalysis is a recently developed eco-friendly approach for the treatment of pollutant. In this study, a piezoelectric catalytic system of manganese indium sulphide (MnIn 2 S 4 ) was constructed for eliminating oxytetracycline (OTC) residues. X-ray diffraction and Scanning electron microscopy showed that MnIn 2 S 4 microspheres with a grain size of 3–5 μm could be hydrothermally produced. Brunauer–Emmett–Teller analysis showed that the specific surface area of the MnIn 2 S 4 sample was 26.6 m 2 ·g −1 , and the average pore size was 20.2 nm. The electrochemical performance test showed that the piezoelectric response current of the MnIn 2 S 4 sample was 0.35 × 10 −6 A. Using OTC as a degradation model, the piezoelectric catalytic performance of MnIn 2 S 4 was explored. The results showed that the maximum degradation efficiency of the OTC could reach 82.2 % after 60 min while the piezoelectric power was 455 W, the pH of the reaction system was 4, the OTC concentration was 0.02 mM, and the MnIn 2 S 4 dosage was 1.4 g·L −1 . During the piezoelectric catalytic process, the main active species were identified as h + , 1 O 2 , and •OH. Meanwhile, eight intermediate products of OTC and three possible degradation pathways were found. This study is important for exploring the application of sulfide-based piezoelectric catalytic materials in wastewater treatment.