The flotation of chrysocolla by mercaptan

Laboratory experiments have demonstrated that chrysocolla and malachite can be floated with a mercaptan as collector. In contrast, even when used in large quantities, the higher xanthate homologs (hexyl, dodecyl) will float malachite but not chrysocolla. The flotation of chrysocolla with mercaptan is readily accomplished in a pristine system, but in the presence of finely ground gangue particles, additions of the mercaptan to the grinding mill gave superior recoveries to those achieved when the mercaptan is added to the flotation cell. A model for the attachment of the mercaptan to the chrysocolla surface is proposed which involves the reaction of molecular mercaptan with the copper sites. This results in the formation of copper mercaptide at the surface and the splitting off of a molecule of water. By extension, this model should describe the reaction of mercaptan with any base metal oxide or sulfide mineral where the metal mercaptide is relatively insoluble.