PRECIOUS METAL EXTRACTION PROCESS

摘要

There is disclosed a process useful for the extraction of gold, silver, and the platinum metals from precious metal containing ores which poses no threat to the environment or the ground water. The process utilizes sodium bromide, sodium chloride, and potassium monopersulfate to react with a water slurry of the precious metal containing ore which has been reduced to a minimum particle size of 250 mesh (10). The leaching out of the gold, silver, and platinum metals occurs when the oxidation-reduction potential is maintained at +600 to +900 with the pH at 3.2 to 3.6 (18). After the precious metals have been dissolved into solution, the ore tailings are filtered (22) and discarded (23). The pregnant leach liquor is pumped to a holding tank (24) where it is subsequently reacted with a solution of sodium hydroxide and sodium borohydride at a pH of 8.2 to 8.6 and the oxidation-reduction parameter held at -550 to -650. A black suspension of the mixed precious metals precipitate out of solution where it is collected (30) and transferred to the refinery for separation and purification by standard procedures. The "barren" leach liquor filtrate is then electrically treated (32), and make-up chemicals of sodium bromide, sodium chloride, and potassium monopersulfate are added for re-use with the next ore batch.