Efficient activation of peroxymonosulfate by CoMg2Mn-LDO for the degradation of orange Ⅱ: The important synergy of Mg

Advanced oxidation process (AOP) based on peroxymonosulfate (PMS) has aroused extensive discussion in the degradation of organic pollutants due to the strong oxidative ability of SO 4 •− . Great attention has been paid to developing transition metal catalysts for PMS activation . Still, few studies focused on the co-catalysis effect of non-redox metals. To study the co-catalysis of Mg and develop a more efficient metal catalyst, the CoMg 2 Mn-LDO was prepared by a co-precipitation method accompanied by calcination. The material showed an excellent ability for PMS activation. 97.1% of Orange Ⅱ was degraded within 15 min with the reaction rate constant (k obs ) of 0.539 min −1 when pH equals 6.7, the dosages of CoMg 2 Mn-LDO and PMS were 90 mg L −1 and 100 mg L −1 , respectively. By contrast, the value of k obs was 0.375 min −1 for the system of Co 3 Mn-LDO/PMS at the same experimental conditions. The electron paramagnetic resonance (EPR) and quenching experiments results proved the existence of O 2 •− , SO 4 •− and HO • in the CoMg 2 Mn-LDO/PMS system and the dominant role of SO 4 •− in Orange Ⅱ degradation. The synergistic effects among Co, Mn, and Mg were found to be responsible for the outstanding catalytic ability of CoMg 2 Mn-LDO. The presence of Mg could not only promote the formation of Mg–HSO 5 − and CoOH + complexes but also reduce the leaching of Co and Mn, which accelerated the generation of free radicals and decreased secondary pollution risk. Based on the overall analysis, reasonable activation mechanisms of PMS and possible degradation pathways of Orange Ⅱ in this reaction system were proposed. This work proves that Mg could be applied as an effective co-catalytic element and provides new insight into developing transition metal catalysts for PMS-based AOPs.