METHOD FOR PRODUCING REFINED SILVER FROM INTERMEDIATE PRODUCTS OF PRECIOUS METAL PRODUCTION CONTAINING SILVER IN THE FORM OF CHLORIDE Russian patent published in 2022 - IPC C22B11/00 C22B3/14 C22B3/10 

FIELD: metallurgy.

SUBSTANCE: invention relates to the metallurgy of precious metals, in particular, to a method for refining silver. Production of refined silver from intermediate products of precious metal production containing silver in the form of chloride includes ammonia leaching, filtration, washing of the deposit, distillation of ammonia into the gas phase, forming silver chloride deposition, metallisation thereof and melting into ingots. The initial intermediate product of precious metal production undergoes reducing treatment in a hot alkaline solution at a temperature of 70 to 90°C and a pH=7 to 12 with a consumption of the reducing agent of 3 to 7% of the one stoichiometrically necessary for silver chloride reduction while ensuring that the redox potential of the system is at the level of 100 to 300 mV relative to the silver chloride electrode. Two cycles of hydrometallurgical processing are then performed in sequence, wherein each cycle consists of ammonia leaching at a temperature of 20 to 40°C, at a concentration of free ammonia of 15 to 25%, for 1 to 4 hours; distillation of ammonia with evaporation of the solution under vacuum or at the boiling point of the solution with absorption of the resulting vapour-gas phase by circulating ammonia solutions; and hydrochloric acid leaching of the silver chloride deposit formed at the stage of distillation of ammonia in a solution at a concentration of HCl=10 to 150 g/dm³, at a temperature of 40 to 90°C, for 1 to 3 hours. The filtered and washed silver chloride is metallised at a temperature of 40 to 90°C, a pH=7-12, initial L:S ratio of 2 to 5 for 2 to 4 hours using an organic reducing agent, then melted into ingots of refined silver with the addition of a fluxing agent, wherein sodium hydroxide is used as said agent.

EFFECT: possibility of reducing the consumption of reagents, lowering the fault rate of silver by impurities of platinum metals due to the reduction thereof to a metallic state and the removal from the process chain at head operations of the process diagram.

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