Abstract:Clay minerals adsorption on uranium is one of influencing factors on uranium migration in acid in-situ leaching system. Kaolin was used as adsorption medium to carry out different L/S experiments on acidic uranium solution with pH value of 2.0 and uranium concentration of 55 mg/L at 17 ℃. The results show that after 97.5 h interaction with kaolin, uranium concentration in liquid phase drops to 0.06~48.76 mg/L under different L/S, and uranium concentration is positively correlated with L/S. Decrease of uranium concentration is not only due to adsorption, but also due to hydrolysis and precipitation of uranium. The smaller the L/S is, the larger the pH value of solution rising, and the more significant the uranium hydrolysis precipitation is. Critical limit of pH value for significant precipitation of dissolved uranium is 2.8~2.9. Adsorption capacity of kaolin to uranium is small and mainly occurs in initial short period within acidic conditions. Adsorption reaction is carried out for the first 0.5 h, and adsorption capacity of different L/S ranges from 44.8 μg/g to 57.04 μg/g, followed by desorption. Uranium adsorption capacity after desorption equilibrium is positively correlated with L/S in general. Occurrence of desorption is related to drops of uranium content in liquid phase, change of molecular structure and surface charge of kaolin, and change of hydrochemical composition.