Electrokinetic remediation of Cd-contaminated soil using low voltage gradients coupled with array adsorption zone and polarity exchange

Abstract

Soil Cd pollution is a threat to the global ecological environment. Electrokinetic remediation (EKR) generally uses strong electric fields to obtain high removal efficiency, which leads to a series of side reactions and high energy consumption. EKR using low-voltage gradients showed weak migration of Cd and low remediation efficiency. Herein, to develop an effective enhanced EKR technology using low voltage gradient (0.2 V·cm−1), array adsorption zone and polarity exchange were applied simultaneously. Five experiments were conducted to determine the effect of polarity exchange, array adsorption zone and their combination on Cd removal when EKR was carried out at 0.2 V·cm−1. Results showed that the combined use of the array adsorption zone and polarity exchange achieved optimal remediation and average Cd removal efficiency was 83%. Moreover, the reciprocating motion of Cd caused by polarity exchange is no longer a side effect. In the wheat cultivation experiment, the Cd concentration of wheat root, stem and leaf decreased by 86%, 93% and 95% after Cd was removed by EKR coupled with array adsorption zone and polarity exchange. The 30-day energy consumption is 7.72 kWh·m−3, which is far lower than that of other enhancement methods. The present work proposes an effective EKR technology working at low voltage for Cd-contaminated soil.