LEACHING OF DOMINICAN GOLD ORES IN IODIDE-CATALYZED THIOCYANATE SOLUTIONS

The use of iodide-catalysed thiocyanate solutions under acidic oxidizi ng conditions to leach samples of gold ores from the Dominican Republi c was investigated in a laboratory-scale study. The thiocyanate system gave results at least as good as cyanide and considerably better than thiourea with modest consumption of SCN (<1 kg/t ore). For both cyani de and thiocyanate lixiviants a residence time of approximately 24 h w as required for maximum gold extraction, which was generally in the ra nge 92-96%. The adsorption of gold from thiocyanate leach liquors on t o activated carbon was found to be rapid. However, activated carbon ca talyses the autoreduction of ferric iron to ferrous iron in thiocyanat e solutions, which suggests that ion exchange may be a better route fo r gold recovery with this leaching system.