Activators are used with Klozur SP to convert the persulfate anion, a strong but kinetically slow oxidant, into the sulfate radical, a much stronger and kinetically faster oxidative species capable of destroying a wide range of organic contaminants. PeroxyChem is the owner or exclusive licensee of several patented methods to activate persulfate: heat, high pH, metals and chelated metals, hydrogen peroxide and zero valent iron (ZVI). The choice of activator system is dependent on several criteria, including the type of contaminants targeted, the application method, site hydrogeology and lithology, and other site conditions such as the presence of structures and underground utilities.
High pH activation is a widely used activation approach for Klozur persulfate that can treat a broad range of contaminants, including chlorinated ethenes, chlorinated ethanes, chlorinated methanes, BTEX, TPH, PAHs, alkanes, MTBE, 1,4-Dioxane, chlorinated benzenes, and pesticides. The target pH for proper activation is in the range of 10.5 – 12. Klozur Caustic (25% environmental grade NaOH) can be used for in situ injection applications. PeroxyChem does not recommend using NaOH solutions greater than 25% due to a high heat of mixing. For soil blending applications, hydrated lime is generally used. High pH activation provides efficient activation while maintaining persulfate longevity within the subsurface. The alkalinity can also provide additional benefits by increases desorption of contaminants from soil surfaces or aid in the dissolution of non-aqueous phase liquids for better contact with the Klozur persulfate. In addition, persulfate solutions at high pH are known to generate super oxide radicals, providing a source of reductive species capable of destroying compounds such as carbon tetrachloride.
Hydrogen peroxide can be used to activated Klozur persulfate for the treatment of a wide range of contaminants, including chlorinated ethenes, chlorinated ethanes, chlorinated methanes, BTEX, TPH, PAHs, alkanes, MTBE, 1,4-Dioxane, chlorinated benzenes, and pesticides. Typical use rates are 5:1 moles hydrogen peroxide to moles Klozur persulfate (46.2 gallons of 17.5% hydrogen peroxide per 100 lbs of Klozur persulfate). PeroxyChem does not recommend injection hydrogen peroxide solutions in excess of 17.5%. Hydrogen peroxide, through reaction with persulfate and generation of heat due to decomposition, activates the Klozur persulfate rapidly, providing an aggressive approach to treating recalcitrant compounds, but resulting in a shortened persulfate lifetime in the subsurface.
Use of iron to activate Klozur SP is very effective for the remediation of chlorinated ethenes, BTEX, chlorinated benzenes, 1,4 – dioxane, MTBE and low molecular weight polyaromatic hydrocarbons (PAHs). The use of a chelating agent, such as EDTA or citrate, helps to maintain iron solubility and transportability at elevated pH’s. Determination of the amount of iron needed is straightforward and dependent upon the volume of groundwater to be treated. Chelated iron provides efficient activation while maintaining persulfate longevity within the subsurface. It is recommended that solutions of chelated iron and Klozur persulfate be made in separate mixing tanks and mixed together prior to the well head. pH of the injected solution and resultant groundwater pH may become as low as 2.