The enhancement of synthesized wastewater on non-uniform electrokinetic remediation of a Cd-spiked natural clayey soil.

It is usually very difficult to achieve satisfactory extraction efficiencies in electrokinetic remediation of heavy metal-contaminated soils of high acid/base buffer capacity. Enhancement agent is often required. In this study, synthesized citric acid industrial wastewater (CAIW) is used as the enhancement agent to remediate cadmium-spiked natural clayey soil from Shanghai, China. Four electrokinetic extraction experiments were carried out to evaluate the enhancement effects of CAIW on the remediation of metal-spiked clayed soil of high buffer capacity and the effects of treatment time and initial cadmium concentration on the migration of cadmium in the specimen. The results of electrokinetic experiments indicated that CAIW can efficiently enhance the transport of cadmium in comparison with HNO3 of the same pH. Cadmium mobilization was enhanced with prolonged treatment time from 104 to 261.2 h, but the average cadmium removal efficiency was not significantly enhanced. A non-uniform cadmium distribution in the specimen was observed after the enhanced electrokinetic experiments due to the localized electrical gradients with an electrical gradient of approximately 1 V/cm and a ratio of the distance between electrodes of the same polarity to the outer diameter of electrode of 2.8 (50:18 mm).