Solvent extraction (SX) of rubidium (Rb) from leaching filtrate of gold waste (GW) in Mouteh Processing Plant by 18-crown-6 (18C6) was studied. High potential of new column flotoextraction (CFE) method in extraction of Rb from dilute solutions was also demonstrated. First, the factors affecting SX of Rb from a synthetic rubidium sulfate solution (containing 100 mg·L−1 Rb) were identified. 0.05 mol·L−1 18C6 in kerosene, 0.02 mol·L−1 picric acid in aqueous phase, aqueous to organic (A/O) ratio of 1, pH 7 and mixing time of 15 min are the optimum values for affective factors. The three-stage precipitation with sodium carbonate, pH adjustment with sulfuric acid and two-stage evaporation and crystallization were conducted to purify the leaching from impurities such as Fe, Al, Mn, Ca and especially competing cations of K and Na. Almost complete extraction of Rb and K from final filtrate containing 0.08 mol·L−1 picric acid was performed using 0.2 mol·L−1 18C6 in kerosene. The Rb and K strippings of 99.12 % and 9.93 %, respectively, are obtained with 2 mol·L−1 nitric acid with A/O ratio of 2. Finally, the performance comparison of the CFE and SX methods in similar conditions shows increased extraction of K and Rb by 16 % and 5 %, respectively, using CFE method. © 2015, The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg.
Year of publication: 2015