Agency of Industrial Science and Technology

Osamu Itabashi

Hiromichi Hayashi

Takashi Iwasaki

Yoshio Onodera

Kazuo Torii

Yoshito Wakui

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.

Method for the recovery of silver value from aqueous solution

Disclosed is a novel hydrous composite oxide of cerium (IV) and phosphorus characterized by the specified chemical composition and the unique X-ray diffractometric pattern, which is useful as an adsorbent or immobilizing agent of strontium ions in an aqueous solution such as radioactive wastes from atomic power plants. The composite oxide prepared by the precipitation reaction of a Ce (IV) salt in an aqueous solution and phosphoric acid can be imparted with an increased adsorption capacity for strontium ions when the precipitates are heat-treated under hydrothermal conditions at up to 300.degree. C. Immobilization of strontium ions adsorbed on the adsorbent can be more complete when the adsorbent bearing strontium ions is dried and subjected to a heat treatment at a temperature of 200.degree. C. or higher.

Growing community of inventors

Sendai, Japan

Osamu Itabashi