Iodide ion as an electron shuttle to significantly accelerate the elimination of sulfamethazine in the Fenton-like system under neutral condition

In this study, iodide ion (I−) was introduced as an electron shuttle to significantly accelerate the elimination of sulfamethazine (SMT) with hydrogen peroxide (H2O2) activated by amorphous zero-valent iron microsphere (A-mZVI) under neutral condition. Compared with the A-mZVI/H2O2 system, the removal efficiency of SMT was improved by 80.8% after supplying with trace amounts of I−. It was that 1O2 was the primary reactive species responsible for SMT degradation, although •OH, O2•−, FeIVO2+, and hypoiodous acid (HOI) also existed in the A-mZVI/H2O2/I− system. Furthermore, the possible degradation pathways of SMT were recommended, and the toxicity assessment of the degradation intermediates were also conducted. In addition, the influences of some key factors, the application in different water matrix, the degradation performance of some diverse pollutants, and the reusability of A-mZVI were also explored. This study proposed a promising process for improving the Fenton-like reaction under neutral condition by using I−.