ON THE POSSIBLE USE OF DI-(2-ETHYLHEXYL) PHOSPHORIC-ACID ZINC AS A RECOMMENDED SYSTEM FOR LIQUID-LIQUID-EXTRACTION - THE EFFECT OF IMPURITIES ON KINETICS

The use of di-(2-ethylhexyl)phosphoric acid (D2EHPA) to extract zinc is being considered by the European Federation of Chemical Engineering Working Party on Distillation, Absorption and Extraction as a recommended system for liquid-liquid extraction studies. If it is to be used on a pilot plant scale then a purification procedure is required which is not complex or expensive. The use of glycol alone to remove mono-ester impurities has been found to affect subsequent zinc extraction kinetics adversely. However, for impure D2EHPA with a mono-ester content not exceeding 3 mol%, the kinetics of extraction were the same as for highly purified D2EHPA produced using the copper precipitation method. Purification of D2EHPA with carbon and silica gel appears attractive for large scale operation; the use of carbon appeared not to affect kinetics. The introduction of surface active impurities in the diluent remains a potential problem. © 1990.