U(Ⅵ) Adsorption Onto Beishan Soil Of Gansu

Large amounts of radioactive waste have been producing during the application of nuclear energy, and its effective disposal is closely related to the sustainable development of nuclear energy. Beishan in Gansu province was preselected as the candidate deep geological disposal repository of spent fuel, which attracted wide attention from researchers. In this paper, Beishan soil(surface soil is equivalent to 0-10 cm soil and deep soil is equivalent to 70-80 cm soil and their transformed soil) was chosen as the sorbent. The adsorption behavior of the original soil and the transformed soil to U(VI) under different environmental conditions was studied using batch techniques. The parameters such as the contact time, solution pH, ionic strength, temperature, and U(VI) initial concentration were optimized. The results show that:(1) Adsorption rate of U(VI) onto the transformed soil is faster than the original soil, and they can reach equilibrium within 24h;(2) The solution acidity has significantly effect on the adsorption. The adsorption capacity of the original surface soil and its transformed soil is enhanced and then declined with the increase of solution pH. But the adsorption capacity of original deep soil and its transformed soil keep increase in the whole pH range;(3) U(VI) adsorption onto the original surface soil and its transformed soil are inconspicuously affected by the ionic strength but onto the original deep soil and its transformed soil are obviously, showing that the adsorption mechanism may be different;(4)The temperature has effect on adsorption of U(VI) which has a certain role in promoting, indicating that adsorption reactions is endothermic process;(5) According to overlap situation of adsorption and desorption curve, U(VI) adsorption/desorption reaction onto the original surface soil and its transformed soil is an irreversible process, and onto the original deep soil and its transformed soil is reversible. The results of this study are expected to provide the basic accumulated data for the inquiry of uranium migration under different environmental conditions.