Electrokinetic Remediation Of Chromium Contaminated Soil Enhanced By Exchange Electrode And Additional Liquid Chamber

Due to the unreasonable stacking and improper disposal form of chromium slag,it poses a great risk to the environment around the stacking site.Electrokinetic remediation technology is an effective technology to remove heavy metal chromium from soil.When electrokinetic remediation of chromium contaminated soil,the removal of chromium in the soil is limited due to the focusing effect of Cr（III）with poor mobility,which reduces the efficiency of electrokinetic remediation.The exchange electrode method can effectively solve the problem of focusing effect of chromium.However,it will also lead to the reciprocating migration of chromium,which is easy to cause certain chromium accumulation in the middle area of the soil chamber and reduce the removal efficiency.Therefore,the purpose of this study is to set the area in the middle of the soil chamber as an additional liquid chamber to collect the reciprocating chromium and improve the total chromium removal rate.On this basis,in order to further improve the mobility of Cr（III）in the site soil polluted by chromium slag and improve the removal rate of total chromium,potassium permanganate,citric acid,potassium citrate and nitric acid solution are selected as enhancers to promote the migration and removal of chromium.The results show that:（1）The combination of exchange electrode method and additional liquid chamber method could not only effectively solve the focusing effect,but also alleviate the problem of chromium accumulation in the middle of soil caused by reciprocating migration,with the highest total chromium removal rate（62.97%）.The combination of exchange electrode method and additional liquid chamber method showed a certain synergy in the removal of total chromium.（2）Based on the combination of exchange electrode method and additional liquid chamber method,potassium permanganate was the most effective to improve the removal rate of total chromium,and its removal rate could reach 70.06%.In this study,the use of enhancing agents improved the soil moisture content and conductivity,but the effect on soil p H was not obvious.Soil p H mainly depended on the exchange electrode and the buffering performance of soil.（3）The additional liquid chamber can effectively collect chromium in the migration path.When the additional liquid chamber was combined with the exchange electrode method,the chromium collection effect was more obvious.The chemical enhancing agents had a significant effect on the chromium collection in the electrode chamber and the additional liquid chamber.Potassium permanganate as an enhancing agent could greatly improve the chromium collection in the anode chamber and the additional liquid chamber.（4）Potassium permanganate had the most obvious effect on the transformation from strongly bound chromium to weakly bound chromium,and greatly improves the content of exchangeable chromium.After the remediation,there were still more exchangeable chromium in the soil,which may need to prolong the remediation time.（5）The exchange electrode method will increase the current and increase energy consumption.Additional liquid chamber could improve the electrolysis efficiency and reduced energy consumption.The combined technology of exchange electrode and additional liquid chamber achieved the highest electrokinetic remediation efficiency while maintaining relatively low energy consumption,and its energy efficiency was2.05 k Wh/g.When using enhancing agents,the energy consumption of nitric acid as electrolyte was the lowest,and the energy efficiency of potassium permanganate as electrolyte was the highest.