Enhanced electrokinetic remediation of Cd,Pb,and As compound-contaminated soil with GLDA
In this study,a biodegradable chelating agent(GLDA,tetrasodium N,N-bis(carboxymethyl)glutamic acid)was applied to electrokinetic remediation(EKR)heavy metals contaminated soil by combining the addition position of agents and pH control technology.The simultaneous removal efficiency of different heavy metals in soil by EKR technology was studied and the removal mechanism was discussed.The results showed that GLDA could significantly increase the concentration of heavy metals in soil solution,which wasconducive to the migration of heavy metals under the direct current electric field.The addition of GLDA increased the current,and the highest current(0.999 A)was found at 7 d in the treatment combined catholyte addition of GLDA with pH control(T4),which was related to the addition of a large amount of acid to the catholyte for controlling pH.The direction of electroosmotic flow was from anode to cathode except for the T4.The addition of GLDA to the anode(T5)was beneficial to the removal of As,and the removal rate was 60.7％.However,the alkaline soil environment was not conducive to the removal of Cd and Pb.The treatment combined catholyte addition of GLDA with pH control got the highest removal rates of Cd and Pb(35.9％and 23.7％),and the As removal rate(42.3％)was only lower than that of the treatment with anolyte addition of GLDA.So the treatment combined catholyte addition of GLDA with pH control was a better method to remove Cd,Pb and As synchronously.After electrokinetic treatment,soil pH and electrical conductivity changed greatly according to different treatments.The general trend was that the soil pH near the anode was lower than that near the cathode,and the soil electrical conductivity generally increased.This study provides a theoretical basis and technical support for the application of GLDA in the electrokinetic remediation of heavy metal-contaminated soils.
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