Degradation Kinetic and Remediation Effectiveness of 1,4-Dioxane-Contaminated Groundwater by a Sono-Activated Persulfate Process

The well-known biorefractory organic material 1,4-Dioxane (1,4-D) is difficult to degrade in groundwater by classical treatment processes. The sono-activated persulfate process was applied to remediate 1,4-D-contaminated groundwater. The influences of the persulfate dose, solution pH, initial 1,4-D concentration, and ${\mathrm{H}}_2{\mathrm{O}}_2$ dose on the enhancement of 1,4-D degradation were studied. The degradation kinetic and remediation effectiveness were also investigated. Up to an 84% 1,4-D elimination was achieved with ${\mathrm{pH}}_0$ of 7.0, temperature of $25\pm 2°\mathrm{C}$, $7.40\mathrm{mmol}/\mathrm{L}$ persulfate, $39.2\mathrm{mmol}/{\mathrm{L}\mathrm{H}}_2{\mathrm{O}}_2$, 400 kHz ultrasonic frequency, 100 W of power, and $2.67\mathrm{W}/{\mathrm{cm}}^2$ ultrasonic density, with an initial 1,4-D of approximately $13\mathrm{mg}/\mathrm{L}$ after an 8-h reaction in aqueous solution. The material 1,4-D in groundwater was eliminated completely after 10 h, while the acute toxicity of the treated groundwater decreased by 99.87%. In this process, the sulfate radical (${\mathrm{SO}}_4^{•-}$) and hydroxyl radical ($•\mathrm{OH}$) were confirmed to be primary reactive species that degraded 1,4-D. A novel reaction kinetic model grounded on the radicals’ oxidation was developed to describe the 1,4-D degradation process from the point of view of math and chemistry. The sono-activated persulfate process successfully degraded the 1,4-D present in groundwater under mild conditions and was accompanied by a toxicity reduction. In conclusion, this is a promising method to remediate 1,4-D-contaminated groundwater.