Silver Recycling from Photographic Bleach-Fix Baths by Ionic Flotation and Thermal Decomposition and Reuse of the Baths

Abstract

Silver was recovered selectively by ionic flotation from photographic bleachfix solutions containing Fe-EDTA. The collector chosen was sodium di-isobutyldithiophosphinate (Aerophine 3418A). which gives a well flocculated precipitate containing 34% Ag and floats in less than 5 minutes. For a collector concentration ranging between once and twice the silver concentration, the recovery rates reach 99% and they are not significantly affected by a pH variation from 4 to 8 and a temperature increase between 20 and 40°C. The desilvered solutions can be recycled in photographic processing, and pure metallic silver at 99.9% Ag is easily obtained from the precipitate phase by thermal decomposition at 900°C.