ZINC DETOXIFICATION OF SOILS BY ELECTRO-OSMOSIS

The feasibility is determined of applying electro-osmosis to selective removal of zinc, a moderately toxic metal, from groundwater in low permeability soils. A laboratory study was conducted to increase the basic understanding of the effect of electro-kinetic phenomena on this chemical species and, subsequently, develop the methodology and technology for large-scale utilization. Equipment was constructed to simulate a system composed of electrode/solvant/membrane/solvant/electrode, where the soil represented the membrane. Experiments were conducted by applying an electrical gradient to the zinc-contaminated soil, which was placed between an anode and a cathode. Removal of metallic zinc from the soil pores to the anode and cathode cells was measured. Diffusion was also allowed between two experiments. Application of electricity appeared to enhance diffusion of zinc into the anode chamber. At the completion of the experiment the concentration of total Zn in the anode chamber increased from 275 mg/l to 745 mg/l and in the cathode chamber from 200 mg/l to 440 mg/l. The experiment consisted of 8 days of diffusion followed by 100 min of electro-osmosis and then 6 days of diffusion followed by 140 min of electro-osmosis. Thirty volts of electricity were applied across the soil specimen in electro-osmosis experiments. Influence of using ligands such as ammonia and hydroxyl ion on removal of zinc was also investigated.