Experimental Study On Supercritical CO₂Fluid Extraction Of Low Grade Uranium Deposit

Supercritical CO₂fluid has good mass transfer characteristics, which can greatlyshorten the time required for phase equilibrium, and is an ideal medium of efficient masstransfer. These mass transfer characteristics produce positive influence to the leaching ofuranium in the ore. In the process of leaching low-grade sandstone uranium ores,supercritical CO₂fluid can form a relatively high concentration of carbonate ions thatcombine with uranium ion in the solution, does not need to add additional leachingsolvents, the pollution to environment will be greatly reduced. The carbonate and uraniumions under certain pH value form highly soluble complexes which can exist in aqueoussolution stably.The supercritical fluid extraction device was designed by our laboratory. In this paper,we experimental research on the feasibility of uranium extraction of low grade sandstoneuranium deposit based on the device. Compared with the traditional acid and alkaline situleaching, this method has certain superiority. We then experimental study on the effect ofpressure on uranium leaching rate, and analyses the reasons. Finally, we examine the effectof leaching time on leaching rate of uranium. In the three stages of experiment, we obtainmain results are as follows:（1） The ratio of liquid-solid3:1, using ferric sulfate as oxidant conditions, supercriticalCO₂fluid can effectively leaching uranium from low grade uranium ore.（2） In the conditions of pressure5-12MPa and leaching time2hours, the uranium leachingrate can be increased. With the continuous rising of pressure, the permeability of rockwill get lower, and the leaching rate of uranium is more and more low. （3） Under the pressure of10MPa, solid-liquid ratio of3:1, FeCl3be the oxidizing agentand temperature45℃, the optimum leaching time is about105minutes.