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SLOW-RELEASE PERMANGANATE VERSUS UNACTIVATED PERSULFATE FOR LONG-TERM IN SITU CHEMICAL OXIDATION OF 1,4-DIOXANE AND CHLORINATED SOLVENTS
Evans, P.J., P. Dugan, D. Nguyen, M. Lamar, and M. Crimi.
Chemosphere 221:802-811(2019)

Slow-release permanganate and unactivated persulfate were evaluated for in situ treatment of 1,4-dioxane (DX) and associated chlorinated solvents. Lab batch studies with unactivated persulfate in deionized water or in soil and groundwater demonstrated DX removal with pseudo second-order rate constants ranging from 10-5 to 10-3/M/s. Flow-through column studies demonstrated over 99% DX removal with slow-release unactivated persulfate but not with slow-release permanganate. The slow-release permanganate cylinders became coated with a rind that limited oxidant mass transfer and DX oxidation. In a field study conducted with slow-release persulfate cylinders transverse to groundwater flow, >99% removal of DX and chlorinated solvents was observed 2.5 m downgradient of the cylinders. Density-driven flow associated with the released persulfate was observed and attributed to a low horizontal hydraulic gradient. Most of the contaminant and persulfate flux was thought to be isolated to a deep aquifer zone bound by an underlying silt aquitard. Contaminant reductions were also observed in shallow groundwater samples. Persulfate oxidant cylinder longevity was an estimated 6-12 months. Careful consideration of cylinder placement during the design phase is needed to prevent the contaminant plume from bypassing and not contacting the released oxidant.



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