Persulfate activation by organic compounds

Activated persulfate is an increasingly popular reagent for the in situ chemical oxidation (ISCO) remediation of contaminated soils and groundwater; however most of the investigations conducted to date have been highly empirical. Results for field scale ISCO applications suggest that persulfate is activated by one or more compounds in contaminanted soils. The purpose of this research was to determine if organic compounds can activate persulfate, and to establish a mechanism of action. This route of activation is very important, since all soils and subsurface solids contain some amount of organic matter. Laboratory experiments were carried out at alkaline pH to screen different functional groups which include ketone, carboxyl acid, alcohols, aldehyde, and the groups in the Kreb cycle such as keto acids, dicarboxylic acids and alcohol acids. The results of the research demonstrated that ketones, primary alcohols and low carbon chain aldehydes can activate persulfate to generate reactive species, providing enhanced destruction of refractory compounds. The results also indicated that the ionized form of the organic compound is important to promote the activation of persulfate. Therefore, phenoxides, which are the salts of phenol and chlorophenols, were selected as the organic compounds for investigating the mechanism of persulfate activation. The results indicate that the activation was via reductive pathway mechanisms, with more rapid activation promoted by the more reduced phenoxides. The results of this study will enhance the effectiveness of persulfate in field application. Soil organic carbon content should be considered in process screening and treatability testing for persulfate in situ chemical oxidation.