SEPARATION OF PALLADIUM AND SILVER FROM A NITRIC-ACID SOLUTION BY LIQUID SURFACTANT MEMBRANES

The recovery of palladium from a nitric acid solution containing silve r has been conducted by application of liquid surfactant membranes (LS Ms) containing LIX 860, a beta-hydroxyoxime, as a mobile carrier in a stirred tank. The extraction equilibria of palladium and silver using several different extractants were also studied. Palladium was selecti vely extracted from a silver-containing liquor with LIX 860 while it w as also observed that both palladium and silver were extractable with a sulfur-containing extractant. The recovery of palladium with LIX 860 was selectively achieved by using perchloric acid solution as the LSM internal phase dosed with thiourea, In the LSM operation, the effects of several chemical parameters on the selective recovery of palladium were studied. The use of hydrochloric acid as an internal receiving p hase prevented the transport of silver into the emulsion due to the fo rmation of silver chloride in the external feed solution. Commercially available Span 80 was found suitable for the selective extraction of palladium as a surfactant in LSM operation. Under optimum conditions, palladium was successfully separated from silver and concentrated into a receiving phase in W/O emulsions.