Electrochemistry-Flushing & Reduction Remediation Of Chromium-Contaminated Soil

The current status of soil environment in China is worrying,especially in some areas.Among them,the problem of heavy metal contamination is particularly prominent.Chromium is one of the common elements in soils contaminated by heavy metal.Current remediation technologies of chromium-contaminated soil hardly achieve the goal of soil remediation,and therefore,the high efficient remediation technology is one of the main research areasforchromium-contaminated soil remediation.In this paper,a new technology,electrochemistry-flushing & reduction(E-F&R)technology,is proposed based on electrochemistry-flushing(E-Flushing)technology,and Cr(VI)desorption kinetics experiments,Cr(VI)reduction kinetics experiments and E-F&R experiments were conducted to study the feasibility and efficiency of E-F&R technology for remediating the Cr(?)-contaminated soil from a real contaminated site.The Cr(VI)desorption kinetics experiments showed that temperature and pH are the main two factors of influence the Cr(VI)desorption efficiency.The increasing of pH or temperature can significantly improve the efficiency of desorption of Cr(?)in the contaminated soil.The Cr(VI)reduction kinetics experiments showed that if the non-specific adsorption Cr(VI)was not removed before remediating Cr(?)-contaminated soil by reductionprocess,the soil particles will be wrapped by the complex precipitation generated fromreductions,resulting in the deficiency of the reduction of internal Cr(VI)and overall remediation.Even if the non-specific adsorption Cr(VI)was removed in advance,it also need high temperature and long time to ensure that Fe2+ can permeate into soil to reduce wrapped and embedded Cr(VI)to improve the reduction efficiency of Cr(VI)in contaminated soil.E-F&R experiments showed that pH did not change significantly compared with the initial pH,and the pH control could not improve the remediation efficiency.After the experiment of E-F&R,the concentrations of soil samples decreased from initial 600 mg·kg-1 to 41 ~ 132 mg·kg-1,72.2 mg·kg-1 in average,resulting in an average removal of 88%.E-F&R technology combines four processes of flushing,electrochemistry processes,and reduction of residual Cr(VI)in wastewater and soil.Fe2+ released from the iron anode reaction was used to reduce the Cr(VI).Flushing and electromigration processes transport Cr(VI)into flushing solution and Fe2+ into soil.Flushing process is also used to destroy the precipitation zone in the soil layer.The electrothermal effect increase the temperature of flushing and reducing reaction,resulting in a high removal for the real chromiumcontaminated soil with a high Cr(VI)concentration.