Electrokinetic Remediation Of Chromium- Contaminated Soil

With increasing of people's environmental awareness, remediation of contaminated soil is attracting more attentions and becoming one of hot topics of environmental scientific researches. For heavy metal-contaminated industrial sites, the soil washing technology is more preferable in field applications, but it is less effective to clay. Electrokinetic remediation (EKR) technology to clay is more effective, but low current efficiency and soil acidification issues severely impede its application in field. In this study, a joint process of water dipping + EKR was employed to treat the heavily contaminated clay spiked with K2Cr2O7. Two types of EKR technologies, traditional EKR with group A and B, were tested here to compare their current efficiency. Based on the results obtained the following conclusions were drawn.â‘ For the heavily chromium-contaminated soil of around 2000mg/kg, water-dipping pretreatment can significantly reduce chromium (â…¥) concentration to a removal rate of 45% to 47% accounting for 54% ~ 67% of the total removal rate.â‘¡In group A, the cathode was copper plate and cathodic electrolyte was KCl of 0.1mo/L. The anode was carbon rod and anodic electrolyte was KCl of 0.1mol/L as well. In the course of test, the pH value of anodic electrolyte decreased to 0.9~2.6 and the pH value of Cathodic electrolyte increase to 10.9~12.9. By comparison with the concentration after dipping treatment, the total removal rates of six sections were 26% in 24h and 43% in 72h. The Cr(â…¥) concentration in soil was 2142mg/kg initially, decreased to 1139mg/kg after water-dipping, and finally reached to 649mg/kg after 72h ERK again.â‘¢In group B, the cathode was copper plate and cathodic electrolyte was CuSO4 of 0.1~0.5mol/L. The anode was Fe and anodic electrolyte was KCl of 0.1mol/L. In the course of test, the pH value of cathodic electrolyte maintained around 4~5 and the pH value of anodic electrolyte maintained around 5~7. By comparison with the concentration after dipping treatment, the total removal rates of six sections were 8% in 24h, 35% in 85.4, and 68% in 203h. The Cr(â…¥) concentration in soil was 2312 mg/kg initially, decreased to 1280mg/kg after water-dipping, and finally reached to 372mg/kg after 203h ERK without water electrolysis.â‘£Comparing the current efficiency of two EKR methods under the same electricity consumption, it was found that EKR without water electrolysis had higher current efficiency. The current efficiency of EKR without water electrolysis was 1.7 times of the EKR with water electrolysis, increasing by 71.4~%72.6% when electricity consumption were 23043.63 C and 57139.5 C respectively.