EXTRACTION OF CHROMIUM(VI) WITH CROWN-ETHERS FROM SOLUTIONS OF MINERAL ACIDS

The extraction of Cr(VI) and Cr(III) ions with solutions of dicyclohex ano-18-crown-6 (DCH18C6) in various organic solvents from solutions of sulfuric, nitric, hydrochloric, and phosphoric acids in the presence of salting-out agents was studied. It was found that the distribution coefficients grow in the sequence H3PO4 < HNO3 < HCl < H2SO4 Chromium( III) was not extracted under the conditions studied. The distribution coefficients of chromium(VI) increased with an increase in the concent ration of sulfuric acid (up to 5 M) and potassium and sodium sulfates in the aqueous phase. The best extracting conditions under which DCH18 C6 effectively separated chromium macroquantities from concomitant tra ce impurities were found, which can be used in the analysis of chromiu m-containing sulfate solutions.