REMEDIATION OF URANIUM AND CESIUM CONTAMINATED SOILS BY USING SOIL WASHING PROCESS

The soil and groundwater contamination caused by uranium and its decay products has become a serious environmental problem in worldwide. In this study, soil washing process to remove uranium and cesium from the contaminated soil was investigated by the batch experiment. Unconsolidated surface soils, manly originated from the weathered black shale in Ockeon, Korea, were used because of their high uranium and cesium concentration (uranium: 158 mg/kg and cesium: 7 mg/kg). The removal efficiency of washing solution according to various pH conditions of solution (pH 1-13) was investigated. Various solutions adding reactants such as acetic acid, citric acid, sulfuric acid, hydrochloric acid and EDTA were used as washing solutions to maximize uranium and cesium removal efficiencies from the soil. Different washing time, solution:soil ratio, and reactant concentration were applied in the experiment to find out the maxium removal efficiency of soil washing process. Results of soil washing experiments using various pH conditions of washing solution suggested that the uranium removal efficiency was over 76 % with strong acidic (pH 1) solution. However, at pH 2-12, the uranium removal efficiency of soil washing maintained around 0-10 %. The removal efficiencies of strong acidic washing solutions such as sulfuric acid and hydrochloric acid were very high, suggesting that the soil washing process is very useful to remediate uranium and cesium contaminated soil.