Catalytic ozonation for degradation of sulfamethazine using NiCo2O4 as catalyst

Abstract

In this study, spinel NiCo2O4 was prepared, characterized, and used for catalytic ozonation of SMT. The performance of NiCo2O4 in SMT mineralization was systematically evaluated. The results showed that NiCo2O4 could significantly enhance the mineralization of SMT over a wide initial pH range of 3.0–9.0. The mineralization rate of SMT increased with the increase in the dosage of NiCo2O4 and O3 concentration, while the initial concentration of SMT (from 10 mg/L to 40 mg/L) had no obvious influence on the removal efficiency of TOC, indicating that the SMT mineralization was mainly affected by the mass transfer. Furthermore, according to the result of the determination of OH, NiCo2O4 could undoubtedly improve the generation of OH, the quenching test confirmed that OH played an important role in TOC removal in ozonation process. Moreover, the XPS spectra of as-prepared and used NiCo2O4 catalyst showed that Co ions might indirectly promote the catalytic ozonation process as the Lewis acid sites, while the Ni2+/Ni3+ cycle in the catalyst played a vital role in catalyzing ozone to generate free radicals and enhancing the mineralization capacity of NiCo2O4/O3 system.