Effective removal of Atrazine using peroxymonosulfate activated by CoNiFe-layered double hydroxides: mechanism and degradation pathway
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Advanced oxidation process (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). During the degradation process, the degradation rate of ATZ was greater than 99% within 60 min when the initial concentration of ATZ was 10 mg·L−1, the dosages of PMS and activator were 0.6 mM and 80 mg·L−1, respectively, and the pH value was 7.0. 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 of the free radicals on the degradation reaction was determined to be SO4•−> O2•− > 1O2>•OH. The analytical results showed that the metal ions reacted with HSO5− in PMS to obtain a change in the valence state of the metal ions and the primary factor affecting the degradation reaction SO4•− was also generated. Nine degradation intermediates with reduced toxicity were detected and possible ATZ degradation pathways were deduced, thus confirming the activation mechanism of CoNiFe-LDH. This representative ATZ removal method provides theoretical basis and guidance for the removal of similar organic pollutants.