U(Ⅵ)在缓冲回填材料高庙子膨润土胶体上的吸附

Investigation of U(Ⅵ)Sorption on GMZ Bentonite Colloid

甘肃北山地区是目前我国高放废物地质处置库的重点预选场址,内蒙古高庙子膨润土为首选缓冲回填材料。在处置库安全评价中需要考虑可能存在的地下水侵蚀形成膨润土胶体负载核素迁移的情况。以产自内蒙古自治区兴和县高庙子矿区Ⅲ号矿层的膨润土为原料提取膨润土胶体,研究其稳定性,通过批式吸附实验研究了溶液pH、背景电解质浓度等对U(Ⅵ)在高庙子膨润土胶体上吸附的影响。结果表明:酸性条件下,高庙子膨润土胶体对U(Ⅵ)的吸附随pH上升而增强,吸附分配系数在pH≈7时达到峰值;碱性条件下,胶体对U(Ⅵ)的吸附则随pH上升而减弱;在本研究所选取范围内,背景电解质NaClO 4浓度对U(Ⅵ)在高庙子膨润土胶体上的吸附影响不大。

Beishan area in Gansu Province has been chosen as one of the candidate sites for China’s HLW repository,and Gaomiaozi(GMZ)bentonite was identified as the most promising backfill material.Due to the intrusion of ground water,a potential problem was taken into account for the long-term safety assessment of the repository,clay colloids generated from the eroded bentonite might play an important role on radionuclide transport.In the present work,the stability of colloids prepared from the bentonite,which was sourced fromⅢledge in Gaomiaozi region,was investigated by the photon correlation spectroscopy.Furthermore,batch experiments were conducted to get a better understanding of the effects of variable pH and background electrolyte concentration on the U(Ⅵ)adsorption onto GMZ bentonite colloids.The results show that under acidic condition,the K d values of uranium increase with the pH increase and reach a peak maximum value in the range of pH≈7.Besides,under alkaline condition,the K d values of uranium decrease with the pH increase.The concentration of background electrolyte NaClO 4 in the selected range of this study has little effect on the adsorption of U(Ⅵ)on Gaomiaozi bentonite colloid.