Copper Solvent Extraction from Waste Cyanide Solution with LIX 7820

Abstract

The use of a solvent mixture of a quaternary amine and nonylphenol (LIX 7820) to extract copper cyanide from waste cyanide solution has been studied. Copper extraction is favorable at low pH, whereas a high cyanide‐to‐copper ratio tends to suppress copper loading. The preferential extraction of Cu(CN)₃ ²⁻ over Cu(CN)₄ ³⁻ and CN⁻ has been confirmed by the examination of both the extraction of copper and cyanide by the solvent mixture under different experimental conditions. The solvent mixture also strongly extracted zinc and nickel from the cyanide solution, but it exhibits weak affinity for iron cyanide complex and free cyanide. The important findings suggested the potential application of the solvent mixture for the recovery of copper and cyanide from waste cyanide solutions, by which copper can be extracted and concentrated into a small volume of solution and the barren cyanide solution recycled to the cyanidation process.

Keywords:

• Copper
• cyanide
• solvent extraction
• LIX 7820

ACKNOWLEDGMENT

The authors thank Dr. Berend Wassink for his generous help on the project. The project was financially supported by the National Science and Engineering Research Council of Canada (NSERC). Cognis is thanked for providing laboratory samples of reagents.