| 摘要 |
The invention relates to a process for silver extraction from used photographic materials and may be used in the industry, using argentiferous materials. Summary of the invention consists in that the process includes treatment of the used photographic materials with 20...40% basic solution of sodium hypochlorite at the temperature of 30...50?C, dissolution of the obtained sediment with 30...40% mixture of hydrogen peroxide and concentrated nitric acid in a volume ratio of (2...3):1, correspondingly, interaction with sodium chloride or ammonium sulphate with formation of the silver chloride or silver sulphate sediment and subsequent silver electrochemical reduction. The silver electrochemical reduction is carried out from the electrolyte obtained by dissolution of silver chloride with potassium ferrocyanide, by boiling in basic medium, with supplementary introduction into the electrolyte of the potassium carbonate, in the following component ratio, g/l:silver chloride��10...20potassium ferrocyanide�30...50potassium carbonate��20...30,at the temperature of 20...30?C and the current cathodic density of 1...1,5 A/dm2, or from the electrolyte obtained at dissolution by boiling of silver sulphate with sodium thiosulphate, with supplementary introduction into the electrolyte of the sodium sulphate, in the following component ratio, g/l;silver chloride��30...40potassium ferrocyanide�300...400potassium carbonate��20...30,at the temperature of 20...30?C on porous electrodes, in flux with the velocity of 3...5 m/min and the current cathodic density of 100...150 A/dm2.
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