Removal of Chromium from Contaminated Soil by Electrokinetic Remediation Combined with Adsorption by Anion Exchange Resin and Polarity Reversal

Soil chromium pollution is a serious environmental problem in the world. The electrokinetic remediation (EKR) is an effective method to remediate heavy metal-contaminated soil. This study aimed to investigate the removal mechanism and the effect of electrolyte alkalization when used the conventional electrokinetic remediation and adsorption to remove Cr(VI) from the contaminated soil. Moreover, we attempted to eliminate the effect of electrolyte alkalization by polarity reversal method. The laboratory experiments include three parts: jar tests of 717 resin adsorption capacity, conventional EKR experiments (EK1–EK5), and polarity reversal experiments (C1–C11). The 717 exchange resin provided better adsorption performance for Cr(VI) in low pH condition. The Cr(VI) in soil was removed by functions of electromigration, adsorption, and reduction. The Cr(VI) removal efficiency reached 72.35%. Part of Cr(VI) was reduced to less toxic Cr(III) by citric acid and free electrons in soil. The electrolyte alkalization in the cathode was an important factor that hindering the EKR. The polarity reversal controlled the electrolyte pH below 7 during EKR. Moreover, the Cr(VI) removal efficiency was 69.20% by reversing polarity every 4 h, and it consumed less energy as compared to the conventional EKR. There were no hazardous materials were added or produced in EKR process. The EKR combined with adsorption is sustainable and can be used in situ.