# US 4,397,689 A · Process for the extraction of precious metals from concentrates thereof

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 4,397,689 A
- Document ID: US4397689A
- Status: Granted
- Kind: A
- Application number: 06/298,356
- Filed: 1981-09-01
- Granted: 1983-08-09
- Earliest claimed: 1980-09-05
- Assignees: Inco Limited
- Inventors: Richard K. Lea; Julian D. Edwards; D. Frederick Colton
- Web page: https://patentgrep.com/patent/US4397689A

## CPC

- C22B 3/34: containing sulfur {, e.g. sulfonium}
- C01G 7/003: {Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange}
- C01G 55/00: Compounds of ruthenium, rhodium, palladium, osmium, iridium, or platinum
- C01G 55/001: {Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange}
- C22B 3/262: {using alcohols or phenols}
- C22B 3/302: {Ethers or epoxides}
- C22B 3/306: {Ketones or aldehydes}
- C22B 3/32: Carboxylic acids
- C22B 3/3846: {Phosphoric acid, e.g. (O)P(OH)3}
- C22B 11/04: {by wet processes (extraction of metal compounds by leaching in organic solutions C22B3/16; treatment or purification of solutions by liquid-liquid extraction C22B3/26)}
- Y02P 10/20: Recycling
- C22B: PRODUCTION AND REFINING OF METALS (electrolytic C25); PRETREATMENT OF RAW MATERIALS
- C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

The process comprises the steps of leaching the concentrate with hot hydrochloric acid and chlorine gas to dissolve most of the gold, platinum and palladium, treating the residue from the leaching step with an excess of an alkaline oxidizing agent to solubilize the ruthenium, slurrying the resulting solids in water, combining the precious metal values from the slurry with the liquor from the leaching step and releaching the resulting slurry with hot hydrochloric acid and chlorine. The leach liquor which is then separated from the remaining solids is a chloride solution which contains substantially all the platinum group metals and gold present in the concentrate.

## Claims

### Claim 1

A process for leaching a concentrate containing precious metals, comprising the steps of leaching the concentrate with hydrochloric acid and chlorine at a temperature in the range from 60.degree. to 105.degree. C. to dissolve most of the gold, platinum and palladium present leaving a solid residue containing substantially all the other precious metals, separating and recovering silver from the process if the silver content of the concentrate is greater than about 10% (by weight) of the concentrate, separating the residue and treating it with an excess (on a weight for weight basis) of sodium peroxide at a temperature in the range from 550.degree. to 650.degree. C. to solubilise the ruthenium, slurrying the resulting solids in water, combining the precious metal values from the slurry with the liquor from the leaching step, releaching the resulting slurry with hydrochloric acid and chlorine at a temperature in the range from 60.degree. to 105.degree. C. and separating the leach liquor from the remaining solids.

### Claim 2

A process as claimed in clam 1 wherein the precious metal values from the slurry are combined with the liquor from the leaching step by combining the whole slurry with the liquor.

### Claim 3 (depends on 1)

A process as claimed in claim 1 wherein the precious metal values from the slurry are combined with the liquor from the leaching step by reducing the ruthenium in the slurry liquor to ruthenium metal which precipitates with the slurry solids, filtering the slurry and combining the solids thus obtained with the liquor from the leaching step.

### Claim 4 (depends on 3)

A process as claimed in claim 3, wherein the ruthenium is reduced using formic acid.

### Claim 5 (depends on 1)

A process as claimed in claim 1 which further includes the step of leaching the concentrate with nitric acid to dissolve some of the silver prior to leaching the concentrate with hydrochloric acid and chlorine.

### Claim 6 (depends on 1)

A process as claimed in claim 1 which further includes the step of treating the solid residue from the leaching step with aqueous sodium hydroxide and then with nitric acid to remove silver from the residue prior to oxidation thereof.