Recovery of base materials from geothermal brines

Abstract

A process is provided for the recovery of substantially pure zinc from geothermal brine also containing recoverable amounts of lead and silver. The process comprises selectively extracting lead and silver from the brine and then contacting the brine impoverished in lead and silver with a substantially insoluble organic extractant (e.g., an ion exchange resin [IX] or an organic solvent [SX]) selective to the extraction of zinc to produce a spent brine, and a zinc-loaded organic extractant. The zinc-loaded organic extractant is separated from the spent brine and the zinc-loaded extractant is contacted with an aqueous solution to remove the zinc as an aqueous zinc chloride solution. The pH of the zinc solution is adjusted, if necessary, to a level to condition the solution to promote the extraction thereof by a cationic organic solvent. The zinc is then extracted from the zinc-loaded aqueous solution using a cationic organic solvent (SX) or an ion exchange resin (IX) selective to the extraction of zinc, thereby producing a zinc-loaded cationic extractant which is separated from the aqueous solution. The zinc is then stripped from the zinc-loaded cationic extractant using an amount of sulfuric acid by volume sufficient to provide an electrolyte solution containing a concentration of zinc sufficient for the recovery thereof by electrowinning. Thus, the process may comprise an SX-SX, or an IX-SX, or an SX-IX or an IX-IX system.