Simultaneous removal of PAHs and heavy metals from soil by combining electrokinetic-assisted delivery of persulfate and ultrasound activation.

Herein, we proposed and demonstrated a novel approach of combining electrokinetics (EK)-assisted delivery of persulfate (PS) and ultrasound-induced thermal activation of PS and release of heavy metals, to synchronously remove organic pollutants and heavy metals from soil. Results showed that in tested soil, the mass transfer efficiency of PS induced by electromigration was approximately 3.36 times that by electroosmotic flow and 1416 times that by diffusion. Compared to the PS injection alone, EK-assisted delivery of PS significantly increased the degradation rate of phenanthrene, improving from 21.60 % to 76.23 %. Due to the applied ultrasound, the temperature of soil was observed to reach target temperatures∼50℃ for effective PS activation, and hydroxyl radicals and alkyl-like radicals were detected in the soil. Moreover, the decomposition of PS on the cathode electrode inhibited the electrolytic water reaction, avoiding the focusing effect and potential flattening. Concurrently, ultrasound thermally activated PS promoted the release of heavy metals from soil. As a result, the removal rates of Pb, Zn and Cd near the anode region increased from 0.00 %, 5.49 % and 11.72 % to 11.89 %, 82.64 % and 86.30 %, respectvcely. These results indicated the novel approach holds the potential for simultaneous removal of organic pollutants and heavy metals.