PRECIPITATION SEPARATION OF STRONTIUM AND CALCIUM FROM ACIDIC SOLUTIONS USING CROWN-ETHER AND TUNGSTOSILICIC ACID

Strontium forms a compound of composition (SrL)AA.nH2O with low solubi lity (5.0 . 10(-6) mol Sr . dm-3) in the presence of 18-crown-6 (L) an d tungstosilicic acid (H4A) in acid media, as has been found by radiom etric precipitation titration. Formation of the compound with limited solubility was used for separation of strontium and calcium from 1 mol . dm-3 HCl. It is possible to separate strontium in the range from tra ce to 6 mmol. dm-3 in the presence of calcium with its concentration u p to 0.2 mol. dm-3 and the recovery determined was 95% of Sr and 5% Ca or 90% of Sr and 4% Ca, respectively. The ratio of Sr/Ca depends on t he stability constants ratio of metal-L (beta(sr)/beta(ca)) in the cas e of gradual addition of L. Potassium up to the concentration of 0.05 mol . dm-3 does not influence recovery of strontium.