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There is limited understanding of the underlying process that govern the peroxone activated persulfate (PAP) oxidation of 1,4-Dioxane, specifically at what rates this advanced oxidation process (AOP) proceeds, how long the system remains active once injected into a contaminant plume, and which radicals might be involved. The research presented herein investigates a peroxone activated persulfate oxidant, patented by EnChem Engineering (Newton, Massachusetts) under the name OxyZone®, and its effect on 1,4-Dioxane contaminated water under column scale conditions in the presence of porous material. A secondary objective of this study was to identify radicals formed during the oxidation of 1,4-Dioxane using OxyZone with Electron Paramagnetic Resonance (EPR) spectroscopy. Initial batch experiments provided data on the reaction rates as a function of the oxidant: contaminant ratio. The formation of hydroxyl radicals, and possibly sulfate radicals, was confirmed by EPR. Subsequent flow-through columnscale experiments were conducted in a sand packed, 1.5 m long PVC column saturated with an aqueous solution containing dissolved approximately 300 μ/L 1,4-Dioxane. 1,4Dioxane effluent concentrations were monitored with a Gas Chromatograph-Mass Spectrometer. Two types of column scale experiments were performed to simulate two possible oxidant injection schemes, namely oxidant injection at one or more than one locations within the flow field of a 1,4-Dioxane plume. In these column experiments, the oxidation rates varied from 0.08 h-1to 1.54 h-1 and were greatest when the oxidant was injected as two slugs farthest up-gradient. Under these conditions, almost all 1,4-Dioxane was destroyed during breakthrough of the oxidant solution. Most noteworthy is that the degradation process continued past the time expected from the breakthrough of a conservative tracer. The prolonged reactivity was found to be caused by the oxidant solution’s elevated density (about 1.05 g/cm3), which retarded the (upward) flow of the oxidant solution through the column, thereby extending the contact time with the contaminant and decreasing the 1,4-Dioxane concentration to below detection limit during much of the oxidant breakthrough. Together, this research suggests that the insitu chemical oxidation of 1,4-Dioxane in groundwater plumes with peroxone activated persulfate is possible. However, field application must account for the density driven transport that influences the oxidant transport.

In-Situ Treatment of 1,4-Dioxane Under Column Scale Conditions