Ryegrass (Lolium perenne L.) assisted electrokinetics coupled with permeable reactive barrier for the remediation of cadmium and copper compound contaminated soil

Abstract

The new type of integrated process of a typical terrestrial plant ryegrass (Lolium perenne L.) assisted electrokinetics coupled with permeable reactive barrier (PEK-PRB) was established for the remediation of Cadmium (Cd) and Copper (Cu) compound contaminated soil. The effects of voltage gradient, ryegrass, and PRB materials on the removal efficiency of heavy metals Cd and Cu in soil were explored. The electrolyte used was 0.1 mol/L citric acid (CA) combined with 0.01 mol/L EDTA, with 6 h of electricity per day and a remediation period of 5 d. The results showed that when the voltage gradient was at 2.0 V/cm, PEK-PRB achieved the best remediation effect, with removal rates of 57.1 % and 18.8 % for Cd and Cu in the soil, respectively. The bioaccumulation factors for Cd and Cu in ryegrass reached 6.67 and 1.80. The exchangeable form of Cd and Cu in soil in each area decreased, while their residual form increased after PEK-PRB remediation. In the case of the contribution rates to the removal of Cd and Cu from the soil, the main parts of the PEK-PRK device were PRB>electrolyte>ryegrass. The addition of plants improved the remediation effect of EK-PRB technology. Heavy metal ions in the PEK-PRB system migrated to the vicinity of the ryegrass and PRB chamber, and were adsorbed, resulting in bioconcentration and removal. By comparing the remediation effects of different technologies, PEK-PRB could achieve better remediation efficiency with lower cost, verifying the feasibility of PEK-PRB in industrial application.