The Study On Degradation Of Organic Pollutants In Water By Manganese Oxide Activated Persulfate

Advanced oxidation processes（AOPs）based on persulfate（PS）has attracted great attention due to its high efficiency for degradation of organic pollutants.Manganese-based materials have been considered as the desirable catalysts for in-situ chemical oxidation since they are abundant in the earth’s crust and environment-friendly.There are many valence and existence states of manganese oxides,and the mechanism of activating persulfate is still unclear,which becomes the bottleneck for its efficient activation of persulfate to remove pollutants.In this paper,a series of manganese oxides have been synthesized and their removal mechanism has been discussed in detail to provide theoretical and technical support for the acquisition of efficient persulfate systems.The conclusions obtained are as follows:（1）Manganese oxyhydroxide（MnOOH）was synthesized and used as an activator for PS to degrade p-chloroaniline（PCA）from wastewater.Experimental results showed that PCA degradation efficiency was enhanced by higher MnOOH and PS addition,and the degradation efficiency was slightly inhibited as the initial p H increased from 3 to 9.MnOOH showed excellent stability and reusability when used as the activator of PS.A comprehensive study was conducted to determine the PS activation mechanism.The results revealed that PS activation by MnOOH followed a nonradical mechanism.No¹O₂ was generated,and the main active substance in the reaction was the activated PS molecule on the surface of MnOOH.The hydroxyl group on the catalyst surface acted as a bridge connecting PS and the catalyst,leading to the activation of PS.The intermediates during PCA degradation were also analyzed,and three possible degradation pathways of PCA were proposed.（2）Different crystalline MnO₂ was synthesized and used it for the study of activated persulfate.The activation effect ofβ-phase MnO₂ on PS was better than that ofαandγphases.β-MnO₂ activation of PS to degrade PCA was a nonradical process and ¹O₂ was not generated during the reaction.The chloride ions in the sewage will not affect the degradation efficiency of theβ-MnO₂/PS/PCA system,and reduce the risk of more toxic and reduced products due to the introduction of halogen ions.Oxygen vacancies on the surface of MnO can promote PMS to degrade TC.This study expects to deepen the understanding of the PS activation mechanism by manganese oxide,and provides technical support for the practical application of AOPs of manganese-based materials for wastewater treatment.