Mechanochemical treatment with CaO-activated PDS of HCB contaminated soils

Mechanochemical methods with co-milling reagents have been widely used to degrade organic pollutants. In this study, calcium oxide and persulfate were employed as co-milling reagents in a mechanochemical process that showed highly effective degradation of hexachlorobenzene in contaminated soil. The influences of soil particle size and organic matter content were also investigated. The interaction between different factors was analyzed by response surface methodology, and a multi-variate regression equation was obtained relating the soil-to-oxidant mass ratio, rotation speed and organic matter content. The existence of SO4 center dot- and center dot OH during the mechanochemical reaction was proved by the indirect detection of benzoquinone and p-hydroxybenzoic acid for the first time, providing a new method for testing free radicals in solid-phase reactions. Finally, a possible activation mechanism and hexachlorobenzene degradation pathway were proposed. This study successfully presents a mild degradation method in the field of hexachlorobenzene contaminated site remediation. (C) 2020 Elsevier Ltd. All rights reserved.