Removal of Radioactive Cesium in Secondary Wastewater after Soil-washing Process

Objectives : Secondary wastewater is generated as the soil washing process proceeds to restore contaminated soil near the nuclear power plants (NPPs). In this study, we tried to evaluate the possibility of removing radioactive cesium from secondary wastewater through the adsorption process using illite.Methods : To treat radioactive cesium present in wastewater, as an adsorbent, we used illite collected from Yeongdong, Chungbuk, and weathering illite artificially weathered by high temperature and acid treatment (60℃, 0.01 M HCl). Before and after weathering, the adsorption rate of illite at low concentrations of cesium and the desorption rate of adsorbents were compared and evaluated using a 1.5 ppm of competitive potassium ion similar to that of groundwater.Results and Discussion : When the illite was artificially weathered, the amount of frayed edge sites increased as the interlayer ions in the illite eluted. As a result of the adsorption and desorption experiments, it was confirmed that the adsorption rate of weathering illite increased by about 11% in acid condition (pH 3) and about 26% in neutral condition (pH 6.2), and the desorption rate of weathering illite decreased by about 6% in acid and neutral conditions, compared to Yeongdong illite. Yeongdong illite and weathering illite showed higher adsorption rate under neutral condition than acidic condition, because the surface of the illite became negatively charged at high pH so the reactivity with cesium present as a cation increased.Conclusions : The artificial weathering process has improved the performance of illite as an adsorbent. We expect that weathering illite can be used as an effective adsorbent for the removal of radioactive cesium from NPP.

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