Influence of anionic species on uranium separation from acid mine water using strong base resins

The presence of uranium and other elements in high concentrations in acid mine drainage at Poços de Caldas Uranium Mine (Brazil) is a matter of concern. The acid water pH is around 2.7, the uranium concentration is in the range of 6-14 mg L−1, sulfate concentration near 1400 mg L−1, fluoride 140 mg L−1 and iron 180 mg L−1. In this solution, where sulfate is present in elevated concentrations, uranium is basically in the form of UO2(SO4)34−. This study investigated the separation of uranium from the other anions present in the acid water under batch and column mode using ion exchange technique. The pH studied was 2.7 and 3.9. Two strong base anionic resins were tested. The influence of ions, commonly found in acid waters like sulfate and fluoride, on ion exchange process was also assessed. Equilibrium studies were carried out to determine the maximum adsorption capacities of the resins. The resins showed a significant capacity for uranium uptake which varied from 66 to 108 mg g−1 for IRA 910U and 53 to 79 mg g−1 for Dowex A. The results also showed that SO42− is the most interfering ion and it had a deleterious effect on the recovery in the pH range studied. Fluoride did not affect uranium removal.