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Silver electrolytic refining process
One, adding acid for precipitation
Thiosulfate Decomposition Process
Acid triggers thiosulfate ions to decompose into sulfur and sulfur dioxide gas. Silver ions then react with the sulfur to form a silver sulfide precipitate. Burning the silver sulfide in a high-temperature furnace breaks it down into elemental silver and sulfur dioxide gas.
Electrolysis
Use a stainless steel plate as the cathode and apply a direct current to produce metallic silver at the cathode. With careful control, this process achieves silver purity between 90–98% and recovery rates around 90–95%.
Metal Substitution
Reactive metal substitution offers a simple approach; however, it produces silver with low purity and a low recovery rate.
Sodium Borohydride Reduction
Leverage the strong reducing properties of sodium borohydride in an alkaline solution to replace metallic silver. This secondary recovery method reaches up to 99.9% recovery and yields silver with 96–98% purity.
Reducing Sugar Reduction Method
Recent developments use an organic reducing solution to recover silver. First, prepare a reducing sugar solution by mixing tartaric acid with sucrose, then use this solution to reduce silver in the waste fixing solution. This method avoids contamination from carbon, silicon, iron, aluminum, and copper, resulting in silver powder with purity greater than 99% and a recovery rate exceeding 95%.
Sodium Dithionite Reduction
Apply sodium dithionite (Na₂S₂O₄) directly to the waste fixing solution to reduce silver while oxidizing it to Na₂S₂O₃. This approach not only delivers high recovery rates and high-grade silver but also increases the concentration of Na₂S₂O₃—the main component of the waste fixing solution—thus regenerating the solution.
Additional Services
Our company supplies consumables for precious metal refining and silver extraction, such as crucible silver test paper and filter cloth. For silver electrolysis equipment, visit the Zhengzhou Jinquan official website for more details.
Silver electrolytic refining process
