Experimental evaluation of catalyzed hydrogen peroxide and sodium persulfate for destruction of BTEX contaminants

Due to the toxicity and prevalence of BTEX contaminants (benzene, lolitene, ethylbenzene, and xylenes) at hazardous waste sites, approaches for their remediation are of interest, especially those that particularly address benzene, which is often the limiting factor for achieving regulatory cleaning at these contaminated sites. In situ chemical oxidation (ISCO) is a viable technology for BTEX destruction, and hydrogen peroxide and sodium persulfate are two oxidants of interest for BTEX treatment. Laboratory studies were conducted to conducted to compare BTEX contaminant destruction and oxidant persistence for these two oxidants and for varied methods of oxidant activation/propagation. Additionally, studies were performed to compare contaminant destruction and oxidant persistence in laboratory contaminant spike systems vs field site contaminant systems. Finally, contaminant destruction and oxidant persistence in field porous media with varied characteristics were evaluated. Contaminant and oxidant concentrations were measured at multiple time points over a three-week reaction period in each oxidant and oxidant activstion/propagation system. Under the comparable conditions evaluated here, sodium persulfate systems demonstrated greater BTEX contaminant destruction and greater oxidant persistence than hydrogen peroxide systems. FeSO4 and citric acid activation of sodium persulfate resulted in greater BTEX destruction and greater oxidant persistence than pH adjustment or hydrogen peroxide activation in both laboratory contaminant spike systems and field gas condensate systems. Additionally, results indicate that the response of the contaminant(s) and oxidant (extent and rate of depletion) are both contaminant- and porous media type-dependent.