Enhanced degradation of sulfamethazine in FeCeOx Fenton-like system by tea polyphenols as reducing agents: Performance, mechanism and pathway

In this study, we constructed a Fenton-like system with FeCeOx nanocomposite, tea polyphenols (TP) and H2O2 for the degradation of sulfamethazine (SMT). Compared with other reducing agents (RAs), the addition of TP had a strong promoting effect on SMT degradation of FeCeOx/H2O2/RAs system, then FeCeOx/H2O2/TP system could realize the complete degradation of SMT within 90 min under optimized conditions of 150 mg·L−1 of catalyst dosage, 2.12 mmol·L−1 of H2O2 concentration, 115 mg·L−1 of TP dosage and 5.2 of initial pH. The main active species in FeCeOx/H2O2/TP system and their corresponding contributions to the SMT degradation were ranked as following: ∙OH (52.5%) > 1O2 (31.9%) > ∙O2- (15.6%). The reduction mechanism (heterogeneous catalysis) and chelation mechanism (homogeneous catalysis) of FeCeOx/H2O2/TP system were proposed. The addition of TP not only achieved the circulation of Fe/Ce species and the formation of oxygen vacancies on the catalyst surface, but also could accelerated the formation of various chelate structure in solution, which both contributed to the generation of active species. SMT was mineralized into CO2, H2O2 and some short chain carboxylic acids through five degradation pathways. Finally, FeCeOx/H2O2/TP system exhibited favorable degradation rate (>90%) towards SMT after six recycling times, and it could work effectively in different water sources. This study provided a new insight into Fenton-like process for improving pollutant degradation.