Uranium concentration from acidic mine effluent using forward osmosis

Uranium (U) is found in the earth's crust at concentrations ca. 1 to 3 ppm, which presents opportunities for various industrial and hydrometallurgical processes aimed at achieving economical and low-energy-intensive extraction. In this study, we assessed the potential of forward osmosis (FO) to concentrate the uranium mine effluent using sodium sulphate as draw solution. The diluted draw solution can be directly reused as a raw material in the uranium leaching process without the need for regeneration. Laboratory FO experiments were performed for 160 h duration on synthetic uranium solution representing typical mine effluent characteristics of the Jadguda uranium extraction facility, Bihar, India. The results of the study showed that with forward osmosis, uranium can be concentrated to ca. 3.36 times of its initial concentration and ca. 98% rejection, but with considerable flux decline due to membrane fouling and surface crystallization. Further, the membrane can be operated after regeneration using DI water rinsing or physical cleaning with a lower flux recovery of 83.1% and 81.2%, respectively. Importantly, it was observed that operating membrane below critical concentration factor via cyclic mode can avoid surface crystallization and subsequent membrane fouling with least periodic maintenance. Additionally, with FO concentration process the U concentration much lesser than Indian regulatory guidelines for inland water discharge (i.e. 180μg of U L^-1) could be achieved using draw solution. Our study highlights that the FO concentration process can significantly concentrate uranium mine effluent at room temperature, requiring less specific energy compared to conventional evaporation-based processes that are highly energy-intensive.