| Large amounts of chromium residue are produced with the development of industrialization, the discharge of them has caused serious soil pollution.Thus, the soil contaminated with chromium needs to be remediated.The traditional treatment methods used for remediation of chromium-contaminated soil have some inevitable flaws, However, the electrokinetic technology, as a new and green remediate method, showed a great application prospect. In this study, the electrokinetic remediation improved by bipolar membrane technology was used to treat Kaolin soil contaminated chromium and the chromium residue. Different electrobaths were used to treat chromium-contaminated soil for investigating the optimal electrokinetic setup and the experimental conditions. The main results are as follows:An electrobath with a single soil compartment was used to remove Cr??? from simulated soil. Under the optimal conditions:the current density of 2.0 mA/cm2 and the electrolysis time of 69 h, Cr??? removal efficiency was 90.0% when the initial concentration of Cr??? was 2700 mg/kg. After Ca2+, Fe3+ and Zn2+, which were the main chemical composition of soil, were added into chromium-contaminated soil, the removal efficiency of Cr??? decreased from 97.3% to 66.6%?165 h?,73.9%?99 h? and 89.5% ?105 h?, respectively. When the current density was 2.0 mA/cm, the removal efficiencies of Cr??? were 89.2% and 90.0%, respectively, when an electrobath containing two soil compartments was used to treat the chromium-contaminated soil, after 57 h, the energy consumption was 0.120 kw.h/g chromium removed. As for using three soil compartments, the removal efficiencies of Cr??? were 89.2%,90.0% and 89.2%, respectively, at the same current density and electrolysis time, the energy consumption was 0.103 kw. h/g of Cr??? removed when an electrobath containing three soil compartments was used to treat chromium-contaminated soil.An electrobath with a single soil compartment was used to remove Cr??? from simulated soil.The results showed that when the initial concentrations of Cr?VI? was 1500 mg/kg, the Cr??? removal efficiency could reach to 87.8% under the optimal conditions:the current density of 3.0 mA/cm2 and the electrolysis time of 69 h. The highest removal efficiency of Cr??? increased to 95.5% after 80 mg/kg humic acid was addedinto the soil compartment. The removal efficiencies of Cr??? were 85.4% and 93.8%, respectively, the energy consumption was 0.351 kw.h/g of Cr?VI? removed, when a system with two soil compartments was used to treat soil after 45 h at the current density of 3.0 mA/cm2. The removal efficiencies of Cr??? were 81.5%?86.0% and 91.2%, respectively, and the energy consumption was 0.103 kw.h/g Cr?VI? removed when a system with three soil compartments was used to treat soil after 48 h at the current density of 3.0 mA/cm2.An electrobath with two adjacent soil compartments was used to remove Cr??? and Cr?VI? simultaneously. When the current density was 3.0 mA/cm2 and the electrolysis time was 43 h, the results showed that the removal efficiencies of Cr??? and Cr??? were 86.2% and 79.6%, respectively, and the total average energy consumption was 0.227 kw·h/gCr removed when the initial concentrations of Cr??? and Cr??? were 2700 mg/kg and 1500 mg/kg, respectively. At the same current density and the electrolysis time, the removal efficiencies of Cr??? and Cr??? were higher than 75%, the total average energy consumption was decreased to 0.162 kw·h/gCr removed, when an electrobath with four soil compartments was used to treat soil.The electrokinetic remediation improved by bipolar membrane technology was used totreat chromium residue, the removal efficiencies of weak acid extractable state chromium, iron and manganese oxides statechromium, organic matter and sulfide statechromium, and residual state chromium were 94.5%,67.8%,55.4% and 94.5%, respectively. This showed that the electrokinetic remediation was effective on the removal of weak acid extractable chromium and residual chromium. |
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