Experimental study on removal behaviors of heavy metal chromium from contaminated soil via electrokinetic method
To solve the problem of soil pollution,the removal behaviors of chromium from contaminated soil were studied via the electrokinetic method using the self-set electrokinetic device,considering of the influencing factors such as voltage,electrolyte type,and concentration.The results show that the electrokinetic method can effectively remove heavy metal chromium in soil,and the migration of chromium(Ⅵ)in soil is greatly affected by voltage.When the voltage increases from 10 V to 40 V,the removal rate of chromium(Ⅵ)increases by 12.25％.However,the removal rate of chromium(total)slightly increases only by 3.72％.After adding 0.05 mol/L Sodium Dodecyl Benzene Sulfonate(SDBS)to the electrolyte,the removal rate of chromium(total)increases by 5.94％,and the removal rate of chromium(Ⅵ)increases by 4.77％after adding 0.15 mol/L SDBS,indicating that SDBS has no significant effect on the electromigration of chromium from contaminated soil.The Citric Acid(CA)can efficiently enhance the electromigration of chromium,and increasing the concentration of CA could improve the removal rate of chromium.When 0.15 mol/L citric acid is added to the electrolyte,the removal rate of chromium(total)increases by 18.03％,the removal rate of chromium(Ⅵ)reaches 93.4％,and the removal rate of chromium(total)reaches 74.96％.The removal amount of weak acid extraction and reducible chromium accounts for about 95％of the total chromium removal amount.Citric acid can promote the conversion of residual chromium to a weak acid extraction state and promote the migration of chromium,so that the residual amount of chromium in various forms is reduced,and the toxicity of chromium-contaminated soil is greatly reduced.After electrokinetic removal,the surface of the soil appeared needle-like,flocculent,or granular.A large number of small pores could also be observed,and the structure became relatively loose.
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