Monitoring and analysis of key indicators in the process of electrickinetic remediation of Cr(Ⅵ) contaminated groundwater

Electrokinetic remediation is an effective method to remove heavy metal contaminants from groundwater. The effect of different voltage gradients (1, 2, 3 V/cm) on the removal rate of saturated zone groundwater Cr(Ⅵ) was studied with an initial content of 1 000 mg/kg for 4 days by the electrokinetic remediation method. In addition, the relevant factors in the repair process, including current, pH and redox potential (E_h) of anode and cathode electrolytes, and the concentrations of Cr(Ⅵ) in different positions were monitored. PH, the removal rates of Cr(Ⅵ) and E_h of the saturated zone medium before and after treatments were analyzed The results showed that: 1) The average removal rates of Cr(Ⅵ) increased with the increase of voltage gradient. When the voltage gradient was set at 2 V/cm, the removal efficiency and economy were better. The removal rate increase/energy consumption increase ratio was 0.52. The highest removal rate of 91.41% was observed when the voltage gradient was set at 3 V/cm, and the higher corresponding energy consumption was observed. 2) During the repair process, Cr(Ⅵ) would be enriched near the anode, especially when the voltage gradient was low (1 V/cm). The Cr(Ⅵ) concentration in groundwater near the anode after the reaction was up to 2170.95 mg/L, and the concentration of Cr(Ⅵ) in the medium was 1497.45 mg/kg, with negative removal rate. The concentration of Cr(Ⅵ) in the anolyte showed a tendency to increase first and then stabilize. When the Cr(Ⅵ) concentration was close to 4000 mg/L, it was close to the maximum migration value of the device. Increasing the reaction time had little effect on the recovery rate of Cr(Ⅵ). 3) The decrease of E_h and the increase of pH during the repair process would promote the reduction and desorption of Cr(Ⅵ), which could promote the removal of Cr(Ⅵ).