Improvement in electrokinetic remediation of chromium contaminated soil with polarity exchange technique
- Received Date: 21/05/2008
- Accepted Date: 29/04/2008
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Key words:
- electrokinetic remediation /
- polarity exchanges /
- chromium contaminated soil /
- focusing effect /
- electric current density
Abstract: The successful electrokinetic treatment of heavy metal polluted soil depends mainly on soil pH value.Laboratory electrokinetic experiments were conducted using field soils with chromium concentration of 506.36 mg/kg, and subjected to a voltage gradient of 1 V/m. The results show that “focusing effect” generates in the second day using the conventional electrokinetic remediation with fixed polarity. The high remnant Cr(III) in alkaline zone and Cr(VI) in acid zone are observed, the concentration of which are 97.88 mg/kg and 328 mg/kg respectively. The low removal rate of 59.04% was achieved in 8 d. However, polarity exchange technique removed 70.18% Cr in 8 d when exchange frequency was 4 d. Another polarity exchange technique removed 86.10% Cr in 8 d when exchange frequency was 2 d, which decreased the initial concentration of total Cr from 506.36 to 73.56 mg/kg which met China Environmental Quality Standard I for Acid Soils. The polarity exchange technique is easily automated without additional chemicals and complex equipments, and obtains high electric-current intensity and neutral pH in soil.
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