Simultaneous electrolytic recovery of silver from spent fixer solution andregeneration of bleach solution

In colour photography, the film is first treated with bleach solution so th at the reduced silver is oxidised to soluble silver ion which is subsequent ly dissolved in sodium thiosulphate bringing all silver into the solution. During bleaching, the wferricynanide bleach is reduced to ferrous state aff ecting its efficacy leading to its disposal. Similarly the build up of silv er concentration in the thiosulfate complex also leads to its rejection. Th e disposal of large quantities of chemicals not only poses environmental ha zard but also loss of valuable chemicals. This necessitates the recovery of silver From thiosulfate complex and regeneration of bleach solution which facilitate the recycling of the regenerated bleach and fixer solution in th e system, thereby avoiding the pollution problem. Even though various methods are available for the recovery of silver and re generation of bleach, electrolytic method offers the advantage of not alter ing the composition of solution and totally avoiding the use of unwanted ch emicals, thereby making the solution suitable for efficient reuse. In this paper an attempt has been made to recover silver at the cathode and regenerate bleach solution at the anode by the adoption of a divided cell configuration. It was observed that electrolytic production of two useful p roducts one at the cathode and the other at the anode simultaneously reduce s the electrical energy requirements by half in comparision to the power re quirement of individual electrolytic process.