Agency of Industrial Science and Technology

Yoshito Wakui

Osamu Itabashi

Proposed is an efficient method for the highly selective recovery of silver value in an aqueous solution containing silver ions in a low concentration, such as depleted photographic fixing solutions, by extracting the silver ions from the aqueous phase with an organic solution containing 0,0-bis(2-ethylhexyl) hydrogen thiophosphate as an extractant solution and the silver ions contained in the extract solution are back-extracted with a hydrochloric acid solution containing thiourea. Alternatively, the silver-containing starting aqueous solution is contacted with beads of a porous resin bearing the thiophosphate compound so that the silver ions are selectively adsorbed on the resin beads and then the silver ions are leached out of the resin beads with an organic solvent.

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Sendai, Japan

Yoshito Wakui