Cu2+/Cu+ cycle promoted PMS decomposition with the assistance of Mo for the degradation of organic pollutant
The limited production of Cu + in the Cu 2+ /PMS processes constrained its large-scan application for the elimination of organic pollutants . In this study, molybdenum powder (Mo) was applied as the co-catalyst to improve the degradation of 2,4-dichlorophenol (2,4-DCP) in Cu 2+ /PMS system at pH 5.6. By the assistance of Mo, Cu 2+ was rapidly reduced to Cu + which exhibited super activity for the peroxymonosulfate (PMS) activation. Compared with Cu 2+ /PMS processes, the PMS decomposition rate and 2,4-DCP degradation efficiency respectively increased by 62.1% and 83.6% in the Mo co-catalytic Cu 2+ /PMS system after reaction for 20 min. The degradation of 2,4-DCP was completed via both the free radical and non-radical pathways and the free radicals rather than Cu 3+ contributed most to the reaction. In contrast to fresh Mo, the ratio of Mo 4+ increased and Mo 6+ decreased in the used Mo powder, due to the oxidation of Mo 0 by Cu 2+ and/or ∙OH and the reduction of Mo 6+ by O 2 ∙ − . Additionally, the coexistence of Cl - and humic acid with low concentrations showed little effects on the Mo/Cu 2+ /PMS system while HCO 3 − presented an obvious depression for 2,4-DCP degradation. During five cycling runs, all the degradation rates were higher than 92.8%, indicating the good stability of Mo/Cu 2+ /PMS system.
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