Recovery of zinc(II) from HCI spent pickling solutions by solvent extraction

Recovery of zinc(II) from HCl spent pickling solutions by solvent extractio n using CYANEX921, CYANEX923, CYANEX302, tributyl phosphate, and ALAMINE336 extractants was studied. Tributyl phosphate was selected as suitable extra ctant. It permitted both effective zinc(II) extraction and the stripping fr om loaded organic phase with water. The presence of iron(II) did not affect zinc extraction, and only negligible oxidation of iron(II) was observed du ring extraction experiments. CYANEX reagents and ALAMINE336 extracted zinc( II) strongly, but the stripping with water was ineffective. Moreover, a sig nificant oxidation of iron(II) to iron(III) occurred during extraction. Eac h of three reagents (CYANEX923, ALAMINE336 and TBP) extracted iron(III) ver y well. Thus, if iron(III) was present in the spent pickling solution, prio r to the extraction it had to be reduced to iron(II). The oxidation was low for tributyl phosphate and high for CYANEX 923 and ALAMINE 336. CYANEX 302 was inactive both for zinc(II) and iron(III) and could not be used for ext raction of zinc(II) from spent pickling hydrochloric acid solutions.