Mechanism and Pathway of Atrazine Degradation by Peroxymonosulfate Activated by CoNiFe-Layered Double Hydroxide

Abstract

Advanced oxidation processes (AOPs) based on activated persulfate (PS) are gradually being employed in the treatment of novel pollutants. In this study, an efficient and reliable CoNiFe-layered double hydroxide (LDH) was prepared by a hydrothermal method, which could effectively activate peroxomonosulfate (PMS) and cause free sulfate radical (SO4•−) oxidation to decompose atrazine (ATZ). The degradation rate of ATZ was greater than 99% within 60 min at pH 7 when the initial concentration of ATZ was 10 mg·L−1, and the dosages of PMS and activator were 0.6 mM and 80 mg·L−1. The analysis of ATZ degradation confirmed the reusability of the activator and its strong structural stability. The generation of four free radicals was analyzed and confirmed, and the influence on the degradation reaction was SO4•− > O2•− > 1O2 > •OH. The analytical results showed that the metal ions reacted with HSO5− in PMS to cause an oxidation–reduction cycle change in the valence state of the metal ions and generated the primary factor affecting the degradation reaction—SO4•−. Nine degradation intermediates with reduced toxicity were detected and possible ATZ degradation pathways were deduced, thus confirming the activation mechanism of CoNiFe-LDH.