Gold cyanidation under pressure. Review

Currently, the process of gold cyanidation under oxygen pressure is used on an industrial scale, one of the examples is the autoclave processing of the residue of the CESL copper process (hydrometallurgical technology of processing sulfide concentrates). Cyanidation is carried out in an autoclave at room temperature at a partial pressure of oxygen (1.4 MPa). In the presence of submicroscopic gold or tellurides in the concentrate, such as calaverite (AuTe2), petzite (Ag3AuTe2) and silvanite ({Au,Ag}2Te4), the material is reground before the autoclave procedure. Pressure cyanidation (CESL gold process) is carried out under high oxygen pressure with short exposure time at ambient temperature. These conditions minimize thiocyanate formation, while effective leaching gold and silver takes place. This is followed by a filtration step that produces saturated copper-gold-silver solution and washed residue. Gold and silver are extracted through conventional processes of adsorption-desorption-recovery (ADR + CIC) from the saturated solution. The Consolidated Murchison ore deposit contains antimony which is considered to behave as an oxygen scavenger during gold extraction, while increasing both cyanide and lime consumption. There is evidence that the gold is passivated in the presence of antimony sulphides during normal cyanidation. Therefore, the gold mining of the Consolidated Murchison deposit first involves the separation of free gold using gravity enrichment. Then the remaining ore is subjected to flotation, concentrating both gold and stibnite. One of the options for the hardware implementation of the process is the use of a continuous autoclave. At Consolidated Murchison, the autoclave is assembled into a set of 16 pipes with a diameter of 5 cm and a total length of 1360 m. The total pressure in the autoclave is 8.8 MPa, the temperature is 30 °C. Another hardware option is to use a jet type reactor. The principal possibility of using autoclave technology for processing gold-containing flotation concentrates and pyrite cinder is shown.