Abstract: A low viscosity water insoluble extraction reagent composition according to the invention is comprised of: (a) an extractant selected from the group consisting of an aldoxime, a ketoxime, or a combination thereof; (b) an equilibrium modifier having a Brookfield viscosity of equal to or less than about 5 centapoise at 25° C. and a flash point equal to or greater than about 141° F. wherein the molar ratio of modifier to extractant is from about 0.05 to about 2.0 so as to provide a net copper transfer greater than that achieved in the absence of modifier. Such low viscosity extractants afford higher recoveries of copper, permit reduced equipment size such as smaller mixers and settlers and the use of reduced amounts of less overall organic inventory.

Abstract: The disclosed invention concerns a process comprising: (a) providing a pregnant leach solution comprising copper values; (b) contacting the pregnant leach solution with an organic phase comprising a copper extractant at an extraction temperature, Text, to form a loaded organic phase comprising the metal values; (c) contacting the loaded organic phase with an aqueous stripping solution at a stripping temperature, Tstrip, to form a copper-enriched stripping solution; wherein the difference in temperature (?T) between the stripping temperature and the extraction temperature according to equation (I): ?T=Tstrip?Text is less than or equal to about 10° C. In other increasingly more preferred embodiments of the invention, the difference in temperature (?T) is less than or equal to about 5° C., less than or equal to about 2.5° C., less than or equal to about 0° C., less than or equal to about ?5° C., and less than or equal to about ?10° C.