Study of the possibility of regenerative recycling of waste copper plating electrolytes

The possibility of regenerative recycling of waste copper plating solution was studied. The process was based on the reagent method using 10% solutions of sodium hydroxide and sodium carbonate as precipitants. The required amount of precipitant was determined by potentiometric titration. We found that the molar ratio between the precipitant and copper ions is 2.2 to 1. The optimal pH value for solutions during precipitation with alkali was 11, and for soda solution – 10. The degree of metal ions extraction from the waste copper plating electrolyte in these conditions exceeds 99%. By methods of IR spectroscopy and simultaneous thermal analysis, it was established that the interaction of copper ions with alkali produces copper(II) hydroxide, and with sodium carbonate – copper(II) dihydroxydicarbonate (an analog of the natural material azurite). A simulation of the technological scheme for the regenerative recycling of waste copper plating solutions with the obtaining of new working electrolytes was carried out. Copper coatings applied to steel products using the resulting alkali working solutions satisfy the production requirements. Based on the experimental data obtained the disposal of 1 m3 of waste copper plating solutions required about 62 kg of sodium hydroxide or 26 kg of sodium carbonate. Economic calculations have shown that the cost of copper sulfate returned to production is almost 2 times higher than the cost of alkali and acid and 2.1 times higher than the cost of sodium carbonate and sulfuric acid. Taking into account the quality of the applied copper coating the most appropriate option is the regenerative recycling of waste copper plating solutions using alkali.