Recovery of Silver and Gold from Cyanide Solution by Magnetic Species Formed in the Electrocoagulation Process

Abstract

Cyanidation is the predominant process by which gold and silver are recovered from their ores in metallurgical operations, and it is recognized that the Carbon in Pulp, the Merrill–Crowe, the Ion Exchange, and Solvent Extraction processes are used for concentration and purification of gold and silver from cyanide solutions. Among other available options for recovery of precious metals from cyanide solutions, Electrocoagulation (EC) is a very promising water and wastewater electrochemical technique that does not require high concentrations of silver and gold in cyanide solutions to yield excellent results. In this work, an introduction to the fundamentals of the EC process is given, followed by the conditions and results of the EC test run for removal of precious metals from cyanide solutions, and finally the characterization of the solid products formed during the EC process with X-ray Diffraction, SEM, and Transmission Mossbauer Spectroscopy. Results suggest that magnetite particles and amorphous iron oxyhydroxides are present (Lepidocrocite and Gohetite). With the EC process, the achieved removal efficiency of silver and gold from cyanide solutions, within 5 min, exceeded 99%.

Keywords:

• electrocoagulation
• gohetite
• green rust
• lepidocrocite

ACKNOWLEDGMENTS

The authors wish to acknowledge support of this project to the National Council of Science and Technology (CONACYT) and to Dirección General de Educación Superior Tecnológica (DGEST) from Mexico.