Studies on lowering of uranium from mine water by static bed ion exchange process

This paper gives results of the studies carried out for lowering of U content in mine water of a carbonate-hosted uranium ore deposit using static bed ion exchange technology with an emphasis on using chemicals benign to the environment and operating plant. The mine water contained 2 mg/L of U. The limiting concentration of U for safe discharges fixed by the World Health Organisation (WHO) is <= 0.03 mg/L. The investigations carried out include screening of various commercial strong base anion exchange resins for the duty condition followed by optimization of operating parameters during loading and elution with 'screened-in resin'. Modeling of the U sorption on the resin was also carried out. A commercial strong base anion exchange resin namely PFA 4759 satisfied the desired conditions for safe discharges. PFA 4759 gave good loading capacity of about 28 g of U per litre of wet settled resin, when the counter-ion was bicarbonate anion with 50 bed volume/h of mine water as volumetric throughput. Elution studies with strong bicarbonate solution (1M) indicated the scope of recovering 99% of the loaded U. The adsorption followed the Langmuir model with pseudo-second-order kinetics.