A Mechanistic Understanding on Persulfate Decomposition by Soil Minerals: Radical and Non-Radical Pathways of Persulfate Decomposition

Abstract

Persulfate (PS)-based in situ chemical oxidation (ISCO) has been widely used for pollutant remediation in soil and groundwater. However, the underlying mechanism of interactions between mineral and persulfate was not fully explored. In this study, several soil model minerals including goethite, hematite, magnetite, pyrolusite, kaolin, montmorillonite and nontronite were selected to investigate their potential effects on persulfate decomposition and free radical evolution. It was found the decomposition efficiency of PS by these minerals varied significantly, and both the radical and non-radical decomposition processes were included. Pyrolusite has the highest reactivity for PS decomposition, but producing the relatively less free radical including hydroxyl radicals (•OH) and sulfate radicals (SO4•-), because of the non-radical PS decomposition process. While radical process was dominant for PS decomposed by goethite and hematite, and both of radical and non-radical pathways were including in PS decomposed by magnetite, kaolin, montmorillonite and nontronite, respectively. Furthermore, the radical process exhibited the high degradation performance for model pollutant such as phenol with relatively high utilization efficiency of PS, while non-radical decomposition has limited contribution to phenol degradation with extremely low utilization efficiency of PS. This study deepened the understanding of interactions between persulfate and minerals during the persulfate-based ISCO in soil remediation.

Keywords: Persulfate, decomposition, Mineral, free radical, organic pollutant