Mechanism and optimization of enhanced electro-kinetic remediation on 137Cs contaminated kaolin soils: A semi-pilot study based on experimental and modeling methodology

Csium-137 (Cs-137) contamination resulted from wastes disposal and incidents holds serious threat to ecosystems and human health. Electro-kinetic remediation (EKR) is a promising technique for the Cs-137 remediation while soil pH polarization remains to be the obstacle for improving its performance. In this study, strategies of non-uniform electric intensity (EI) and polarity reversal (PR) have been employed to enhance the EKR. A 2-dimensinal (2D) numerical model was applied to stimulate the transport-reactive processes and predict the possible electro-chemical variations during the remediation. Within 168 h treatment, each strategy could increased the EKR efficiency on Cs-137 removal by 5% and larger increase (12%) was observed when combined these two strategies. Good agreements were achieved between the experimental and model results which further verified the feasibility of enhanced EKR on soil Cs-137 removal. In addition, a polynomial linear fitting analysis was implemented for the optimization of PR frequency. The 24 h was determined as the optimal PR frequency and 90% of Cs-137 (276 mg) in polluted kaolin was eliminated within 415 h by PR-EKR under a non-uniform EI. Moreover, the energy utilization efficiency and cost for such technology was obtained in an acceptable value of 0.96 mg/kWh and $ 829, respectively. The results of the semi-pilot experiments indicated that EKR enhanced with non-uniform EI and PR strategies might be practicable and effective for the decontamination of soil Cs-137 in full-scale applications. (C) 2018 Elsevier Ltd. All rights reserved.