SU454279A1 - The method of regeneration of the rhodian silver electrolyte - Google Patents

Description

one

This invention relates to the electrochemical deposition of metals, in particular, to the regeneration of spent silver nitride containing silver nitrate, ammonium containing boron and boric acid.

A known method for regenerating spent silver electrolyte involves adding hydrochloric acid to the spent electrolyte before precipitating silver chloride, settling the precipitate, decanting, treating it in aqua regia and washing the precipitate.

The proposed method differs from the known one in that the process is carried out by diluting the ammonium-rhodium silver complex with water, settling the silver rhodanide precipitate with decantation of the solution and then dissolving the precipitate in the rhodium ammonium solution, which reduces silver loss and shortens the regeneration time of the spent electrolyte.

The process is recommended as follows.

To the spent electrolyte water is poured in the ratio of 1:15.

Both distilled and tap water can be used for dilution. In the case of tap water, due to the presence of chlorine and iron ions in it, silver loss during regeneration increases by

0.2-0.3% and the electrolyte has a yellowish tint due to the color of the complex Fe (CK5) h.

Adding water in the ratio of 1: 15 causes the hydrolysis of the ammonium-rhodium complex, as a result of which a white precipitate is formed of the slightly soluble silver rhodanide salt AgCNS. The precipitate after decanting the solution and washing it once with distilled water is suitable for preparing

new electrolyte.

To this end, the silver rhodanide precipitate is dissolved in a 30% solution of rhodium ammonium, the resulting solution is filtered, and the content of silver and rhodium ammonium in the electrolyte is analyzed.

Example. For regeneration, 100 liters of rhodant silver electrolyte contaminated with noni copper exceeding the permissible (3 g / l) rate was taken.

Based on the proposed dilution ratio of 1; 15, 1500 liters of water were consumed.

The concentration of silver nitrate in the regenerated electrolyte is 30 g / l. A total of 100 liters was: 30X100 3000 g of silver nitrate.

The duration of the dilution process from 100 liters of electrolyte to 1500 liters is 30-40 minutes.

The precipitation of silver occurs within 30-40 minutes after complete dilution of the electrolyte. In order to completely precipitate out (check the filtrate for the presence of silver), it is necessary to settle for 2.5-3 hours.

The duration of the decantation of 1500 liters of filtrate is 50-60 minutes.

The duration of a single wash of rhodium silver with distilled water is about 0.5 hour (pour 8-10 liters of water, mix, stand for 10-15 minutes and drain the wash water).

The precipitate of rhodium silver does not require drying and weighing. Therefore, the precipitate obtained from the regeneration of the electrolyte is not weighed, but immediately dissolves in an excess of the new solution of rhodium ammonium.

The volume of sediment and a small amount of solution above it after decanting was 5 liters.

The amount of precipitate of rhodium silver is determined analytically after dissolving it in an excess of a 30% solution. Its weight was 2940 g.

In order to calculate the amount of the 30% solution of rhodium ammonium required to prepare a new electrolyte, the silver content in the sediment was assumed to be equal to the initial amount (3000 g). According to the electrolyte preparation procedure for 40 g of AgNOs, 282 g of NH4CNS is required. Follow the 3000-282

for 3000 g it will take -

40

 21150 g NH4CNS. In terms of a 30% solution of 70 liters.

The precipitate of rhodium silver was dissolved in 70 liters of a 30% NH4CNS solution.

The total volume of freshly prepared electrolyte was 75 l (sediment -f 70 l of 30% NH4CNS). The content of silver nitrate in 1 liter of the new electrolyte according to the analysis was 39.2 g. In total, 75 l of 2940 g of AgNOs.

For regeneration, 100 l of a solution containing 30 g / l of AgNOs, a total of 3000 g of AgNOs, was taken. To ensure that the silver concentration is within the normal range (40 g / l), the volume of the new electrolyte was 75 liters, i.e., decreased by 25 liters.

Dissolving the precipitate in a 30% NH4CNS solution (including weighing and preparing a 30% NH4CNS solution) was about 1.5 hours.

The total duration of the process of regeneration and preparation of a new electrolyte was 7 hours, i.e., one work shift. Silver losses during regeneration were 2% (60 g from 3000 g).

Subject invention

The method of regeneration of the rhodian silver electrolyte, characterized in that

in order to reduce silver losses and reduce regeneration time, the electrolyte is diluted with water, the precipitated silver rhodanide is precipitated, and the solution is decanted. And, followed by dissolving the precipitate in a solution of rhodium ammonium.