Enhanced-electrokinetic remediation of copper–pyrene co-contaminated soil with different oxidants and pH control

Electrokinetic (EK) remediation has potential to simultaneously remove heavy metals and organic compounds from soil, but the removal percent of these pollutants is very low in general if no enhancing treatment is applied. This study developed a new enhanced-EK remediation technology to decontaminate a heavy metal–organic compound co-contaminated soil by applying different oxidants and pH control. A red soil was used as a model clayed soil, and was spiked with pyrene and Cu at about 500 mg kg−1 for both to simulate real situation. Bench-scale EK experiments were performed using four oxidants (H2O2, NaClO, KMnO4, and Na2S2O8) and controlling electrolyte pH at 3.5 or 10. After the treatments with 1.0 V cm−1 of voltage gradient for 335 h, soil pH, electrical conductivity, and the concentrations and chemical fractionations of soil pyrene and Cu were analyzed. The results showed that there was significant migration of pyrene and Cu from the soil, and the removal percent of soil pyrene and Cu varied in the range of 30–52% and 8–94%, respectively. Low pH favoured the migration of soil Cu, while KMnO4 was the best one for the degradation of pyrene among the tested oxidants, although it unfortunately prevented the migration of soil Cu by forming Cu oxide. Application of Na2S2O8 and to control the catholyte pH at 3.5 were found to be the best operation conditions for decontaminating the Cu-pyrene co-contaminated soil.

► A new technology was developed to decontaminate a compound contaminated soil.
► The highest removal percent of soil pyrene and Cu was 52% and 94%, respectively.
► Acid catholyte (pH = 3.5) and application of Na2S2O8 was the best operation condition.
► The reduction product of KMnO4 prevented the migration of Cu.