Percarbonate persistence under different water chemistry conditions

Abstract

Oxidant persistence is a key factor that determines the successful application of in-situ chemical oxidation (ISCO) system for groundwater remediation. This study explored the stability of percarbonate (peroxide content) under different environmental conditions. We found that the peroxide content of percarbonate decomposed spontaneously once dissolved in water. The baseline treatment without pH adjustment (pH 10.4) had the highest peroxide decomposition rate. Both acidic conditions (pH < 7) and strong basic conditions (pH 12) significantly retarded peroxide decay. Trace amounts of metal cations (Fe2+, Fe3+, Mn2+, Co2+, and Cu2+) greatly accelerated peroxide decomposition while common water matrix anions (Cl−, Br−, HPO42−, NO3−, and SO42−) and natural organic matter (NOM) had negligible impacts on this process. We also found complicated impacts of nine minerals on peroxide decay. Overall, this study shows that the lifetime of the peroxide content of percarbonate is relatively short, thus limiting its long-term availability in the subsurface and reducing the radius of influence of the ISCO remedial system.