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US 6,551,378 B2Granted
Recovery of precious metals from low concentration sources
AssigneeGreen Mineral Products LLC
InventorsWilliam A. Farone, Maryam H. Azad
Life of this patent
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Abstract
A process for the recovery of gold and the platinum group metals from sources that contain relatively low amounts of the metals is described. The process is environmentally acceptable and uses no expensive and potentially dangerous organic solvents. The process utilizes hydrogen chloride, sodium hydroxide, and cation resins to concentrate and purify the precious metals
Claims26
A precious metal recovery method which comprises:
- a. grinding precious-metal and base metals containing solids to obtain a solids fraction passing a less than 100 mesh screen;
- b. contacting said precious-metal-containing and base metals solids in an extraction tank with a leach solution comprising hydrochloric acid and an oxidizing agent for a time period ranging from 10 minutes to 24 hours;
- c. decanting said leach solution from said extraction tank and filtering said leach solution;
- d. sending residual solids from filtration step in (c) to an extraction vessel where residual leach solution from said filtration step is removed from said solids and combining said residual leach solution with filtered leach solution from step (c);
- e. neutralizing filtered solution from step (d) by addition of a alkali or alkaline concentrated base and precipitating any base metals present in said filtered solution as base metal hydroxides;
- f. filtering or centrifuging base metal hydroxides and treating filtrate or centrifugate containing the precious metals in solution with a resin to remove remaining base metals;
- g. precipitating precious metals from base metal free solution of step (f) with a reducing agent and recovering said precious metals.
4 more elements
A precious metal recovery method comprising:
- dissolving a mixture of precious metals and base metals in hydrochloric acid and an oxidizing agent;
- forming chloride salts and separating said chloride salts by a dual resin system in a chromatographic apparatus comprising two chromatographic columns;
- removing the base metals by ion exchange on first column;
- concentrating precious metal salts;
- separating precious metal salts on second chromatography column;
- and
- recovering the separated precious metals by reduction of the separated precious metal salts to pure metals by a reducing agent.
4 more elements
Dependencies are inferred from the claim text.