employee from 01.01.2022 to 01.01.2026
Nizhniy Novgorod, Nizhny Novgorod, Russian Federation
Currently, ferrocyanide - rhodanate electrolyte and dicyanoargentate rhodanated electrolyte are widely used for galvanic silver plating in both scientific research and production. These electrolytes offer significant advantages, providing high-quality coatings approaching those obtained with classic cyanide electrolytes. They provide high cathodic and anodic current efficiencies, are easy to maintain, and are stable in operation. However, they also have significant drawbacks that lead to a gradual deterioration in coating quality: the accumulation of silver rhodanate complexes, metal ion impurities resulting from the cementation of silver by more electronegative metals, and the degradation of surfactants. The combination of these factors, which manifests itself during long-term use, necessitates complete electrolyte regeneration, which involves extracting silver as a metal, converting it into reactive salts, and preparing a new electrolyte. The aim of this study is to validate a technological process for extracting silver from spent electrolyte following laboratory testing and optimize the process to achieve a higher recovery rate approaching 100%, reduce extraction time, ensure operational safety, and enable the application of the obtained results in real-world production. A dicyanoargentate rhodanated electrolyte was used for the experiment. It was demonstrated that the most promising method is a combination of electrochemical metal deposition followed by chemical metal extraction from a low-concentration solution and rinse water. The choice of an electrodeposition mode enabling the extraction of up to 96% of silver in no more than two work shifts was justified. Anode material characterized by relatively low cost and satisfactory stability under electrolysis conditions was selected. To ensure operational safety, which requires the absence of free cyanide anions at concentrations above the maximum permissible concentration, a cyanide scavenger was used. The advantage of this scavenger is the concomitant chemical reduction of silver ions, which increases the overall metal yield and accelerates the overall process. After the main electrodeposition stage, silver was extracted chemically, leaving only traces of the metal in the electrolyte. The resulting silver-containing precipitate was converted into silver(I) chloride with a yield (as metal) of 97.75% of the initial silver content in the electrolyte.
SILVER EXTRACTION, REGENERATION, DICYANOARGENTATE RHODANATED ELECTROLYTE, ELECTRODEPOSITION
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