Influence of SO32 − ions and current density on silver electrowinning from spent photographic solution

The paper describes hydrometallurgical treatment of photographic effluent. A combined effect of cathodic current density and Na2SO3 dosage on the purity of cathodic silver and efficiency of silver electrowinning from spent photographic fixer was shown. It was found that efficient silver recovery is possible at a gradual decrease in the cathodic current density in the subsequent electrolysis stages from an initial value of 0.1 A/dm2. Decrease in the Ag+ ions concentration with the electrolysis time was accompanied by increased contamination of silver deposits with Ag2S, if no extra SO32 − additive was used. 0.05-0.1 M SO32 − addition to the electrolyte allowed to maintain constant Ag2S percentage (1-2 wt%) in the cathodic deposit.