Abstract
The paper concerns a hydrometallurgical method for selective recovery of copper from low-grade electric and electronic wastes. The following consecutive stages were proposed: smelting of the scraps to produce Cu–Zn–Ag alloy, leaching of the alloy in ammoniacal solution, and selective copper electrowinning. Cu–Zn–Ag alloy was a polymetallic and five-phase system. It was leached in chloride, carbonate, sulfate and thiosulfate solutions. This resulted in the separation of the metals, wherein metallic tin and silver as well as lead salts remained in the slimes, while copper and zinc were transferred to the electrolyte. Copper was selectively recovered from the ammoniacal solutions by the electrolysis, leaving zinc ions in the electrolyte. The best conditions of the alloy treatment were obtained in the ammonia–carbonate system, where the final product was copper of high purity (99.9 %) at the current efficiency of 60 %. Thiosulfate solution was not applicable for the leaching of the copper alloy due to secondary reactions of the formation of copper(I) thiosulfate complexes and precipitation of copper(I) sulfide, both inhibiting dissolution of the metallic material.
Highlights
Global trend in electric and electronic wastes production goes currently upward and it seems to be continued for a long time [1, 2]
Cu–Zn–Ag alloy was a polymetallic and five-phase system. It was leached in chloride, carbonate, sulfate and thiosulfate solutions. This resulted in the separation of the metals, wherein metallic tin and silver as well as lead salts remained in the slimes, while copper and zinc were transferred to the electrolyte
Five phases were found in the alloy: three of them appeared as small inclusions within two-phase brass-based alloy matrix
Summary
Global trend in electric and electronic wastes production goes currently upward and it seems to be continued for a long time [1, 2]. Copper is just one of the many metals present in the electrical and electronic equipment, electro-waste is a rich source of the elements It often contains higher percentages of valuable metals than native ores. Studies on the waste electronic scraps recycling are concerned mainly on the recovery of precious metals [4,5,6], while WEEE containing low amounts or no gold, palladium or platinum is classified as a low-value scrap. The latter remains still useful for recycling due to the presence of other elements like copper or tin
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