To improve the performance of focusing phenomenon related to energy consumption and removal efficiency in electrokinetic remediation of Cr-contaminated soil

The focusing phenomenon is a difficult point during the electrokinetic remediation (EKR) of contaminated soil. It restricts the extraction and removal of heavy metals. There is still a lack of methods to discern focusing position rapidly and take proper measures. Therefore, a total of seven tests with or without intervening and regulating measures were conducted. Among the four tests without regulating and intervening measures, focusing position often appeared in low-voltage region after three days' treatment. When using ammonium citrate as electrolyte, the highest removal efficiency of total chromium (Cr) (32.20%) was achieved. The intervening measure that adding citric acid near section 4 decreased the area of high-voltage and made it move towards cathode. Meanwhile, the removal efficiency of Cr(VI) (60.17%) was significantly improved. Using sodium dodecyl sulfate (SDS) as pretreatment agent and electrolyte made the position of high-voltage area move towards anode and removed 35.80% of total Cr and 53.47% of Cr(VI) eventually. Simultaneously, the energy consumption per gram of removed Cr was also the lowest. The focusing degree was reduced with intervening and regulating measures conducted but focusing position still existed in low voltage area, which further indicated that focusing position preferred to appear in low voltage area and we could discern focusing position through voltage distribution across the soil roughly.