Reclamation process for tungsten carbide/cobalt using acid digestion

• US 5,728,197 A
• Filed: 07/17/1996
• Issued: 03/17/1998
• Est. Priority Date: 07/17/1996
• Status: Expired due to Fees

• Current Assignee: NV Union Miniere SA
• Original Assignee: Nanodyne Incorporated
• Inventors: Wu, Li, Seegopaul, Purnesh
• Primary Examiner(s): Simmons, David A.
• Assistant Examiner(s): ELVE, MARIA ALEXANDRA
• Application Number:
  US08/690,148
• Time in Patent Office: 608 Days
• Field of Search: 75/414, 75/419, 75/425, 75/709, 75/710
• US Class Current: 75/710
• CPC Class Codes: C22B 1/005 Preliminary treatment of scrap C22B1/02 - C22B1/26 take precedence
• CPC Class Codes: C22B 23/0453 Treatment or purification of solutions, e.g. obtained by leaching C22B23/0407 takes precedence
• CPC Class Codes: C22B 34/365 from spent catalysts
• CPC Class Codes: C22B 7/007 by acid leaching
• CPC Class Codes: Y02P 10/20 Recycling

Abstract

Tungsten carbide cobalt and tungsten-containing materials are recycled using a single high-temperature oxidation with standard dilution chemistry. The scrap material is ground, oxidized, and subjected to an acid digestion, preferably in hydrochloric acid. This causes the cobalt to form cobalt chloride while the tungsten remains insoluble. The pH is then increased to about 7.0 which causes the cobalt chloride to form cobalt hydroxide which precipitates out of solution. The cobalt and tungsten are separated and dissolved in a high-pH ammonia solution which can then be spray dried to form a precursor powder for subsequent carburization to form tungsten carbide-cobalt powders.

Claims

1. A method of recycling a tungsten/cobalt composition comprising oxidizing said tungsten/cobalt composition at a temperature in excess of 850°

C. to form an oxidized composition;

digesting a portion of said oxidized composition in an aqueous acidic solution to form a slurry of dissolved cobalt composition combined with solid tungsten species;

neutralizing said slurry to a pH effective to cause cobalt hydroxide or cobalt oxychloride to precipitate, and separating liquid components from solid components of said slurry.

2. The method claimed in claim 1 further comprising dissolving said solid components in an aqueous medium having a pH greater than 11.0 and filtering said aqueous medium to remove any undissolved particulate matter.

3. The method claimed in claim 2 further comprising spray drying said aqueous medium.

4. The method claimed in claim 3 wherein said aqueous medium is an aqueous solution of ammonia.

5. The method claimed in claim 1 wherein said high temperature oxidation is conducted at from 850°

to 1200°

C. in the presence of oxygen.

6. The method claimed in claim 5 further comprising forming tungsten carbide by spray drying said aqueous medium and carburizing formed particles.

7. The method claimed in claim 6 further comprising adding a soluble salt of a carrier metal to said aqueous medium to establish a desired ratio of carrier metal to tungsten, and spray drying and carburizing said aqueous solution to form a carrier metal/tungsten carbide complex.

8. The method claimed in claim 1 wherein said acidic solution is an aqueous solution of an acid selected from the group consisting of sulfuric acid, phosphoric acid and nitric acid.

9. The method claimed in claim 3 further comprising adding a soluble salt of cobalt to said aqueous medium to establish a desired ratio of cobalt to tungsten, and spray drying and carburizing said aqueous solution to form a cobalt/tungsten carbide matrix.

10. The method claimed in claim 3, further comprising dissolving additional soluble salt of tungsten in said aqueous medium to establish a desired ratio of cobalt to tungsten.

11. The method claimed in claim 1 further including filtering insoluble material from said slurry.

12. The method claimed in claim 1 further including adding chelating agents to said slurry.