Electrokinetically-delivered persulfate and pulsed direct current electric field induced transport, mixing and thermally activated in situ for remediation of PAHs contaminated soil

Herein, we proposed and proved a novel strategy that enhanced the delivery of persulfate (PS) to soil by electrokinetics (EK), and then applying a pulsed direct current (DC) electric field thermally activated the PS in situ, and synchronously promoted PS plume mixing, contaminants-free radicals reaction and continued to replenish PS to the soil, to achieve efficient degradation of contaminants in low permeability zones. Results showed that transport rate of PS in tested soil by EK was approximately 12.3 times than diffusion. Applying an irregular pulsed DC field maintained the targeted temperature (30-50 ℃) during activation phase, and generated two oxidative radicals (SO4∙-/∙OH). Concurrently, in the case, electromigration and electroosmosis have promoted the PS transport and the reactive mixing of PS/free radicals with polycyclic aromatic hydrocarbons (PAHs) contaminated soil and enhance the PAHs degradation. PS concentrations in pore fluid was characterized by an increase accompanied by continuous fluctuations. Eventually, in case of the long-term low-temperature activation (i.e., 30-40 ℃), a significant decreases (nearly 60%) in average concentration of PAHs in the whole soil cell was observed over 10 days. These results demonstrates that the novel strategy has great potentiality in the remediation of low permeability contaminated soil.