Method for recovering platinum group metals from catalytic structures

Patent metadata

Field	Value
Publication number	US-9580826-B2
Application number	US-201414784056-A
Country	US
Kind code	B2
Filing date	Apr 9, 2014
Priority date	Apr 11, 2013
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

A method for recovering platinum group metals from a catalytic structure, such as a fuel cell membrane electrode assembly, involving dissolution of the platinum group metal by treating the catalytic structure in an electrolytic cell with a suitable electrolyte containing a complexing agent and introducing an electric current into the electrolytic cell; and subsequently re-precipitating the platinum group metal by increasing the pH of the electrolyte system and adding a reducing agent.

First claim

The invention claimed is:

1. A method for recycling platinum group metals from a catalytic structure, comprising the steps of:
a) dissolving the platinum group metal by treating the catalytic structure in an electrolytic cell with a suitable electrolyte including a complexing agent and introducing an electric current into the electrolytic cell; and
re-precipitating from said electrolyte including a complexing agent the platinum group metal by increasing the pH of the electrolyte system and adding a reducing agent;
wherein the platinum group metal and the electrolyte are not separated prior to re-precipitation of platinum on the catalytic structure;
wherein said current is a bias for dissolving platinum with a constant potential with intermittent pulses of lower potential for reestablishing the state of the surface of the catalytic structure; and
wherein said current is not an alternating current.

2. A method according to claim 1 , wherein the electrolyte further comprises a wetting agent.

3. A method according to claim 2 wherein said wetting agent, comprises an ionic surfactant or a nonionic surfactant.

4. A method according to claim 1 , wherein the platinum group metal is re-precipitated as pure noble metal catalyst powder, or as part of an alloy or re-deposited directly on a support material.

5. A method according to claim 1 , wherein the platinum group metal is re-precipitated on a suitable substrate by nucleating the platinum group metal directly on the desired substrate structure.

6. A method according to claim 5 wherein said structure comprises carbon particles.

7. A method according to claim 1 , wherein the electrolyte system pH is adjusted according to the conditions of the re-precipitation method chosen.

8. A method according to claim 1 , wherein the complexing agent is any ligand system with donor atoms belonging to either the carbon group or the groups of pnictogens.

9. A method according to claim 8 wherein said carbon group comprises one or more members selected from the group consisting of cyanides, alkynes, alkenes, and aromatics.

10. A method according to claim 8 wherein said pnictogen comprises one or more members selected from the group consisting of amines, phosphenes, arsenes, chalcogens, and halogens.

11. A method according to claim 1 , wherein the reducing agent is selected from liquid organic compounds.

12. A method according to claim 11 wherein said liquid organic compound comprises one or more members selected from the group consisting of glycols, alcohols, antioxidants, and formic acid.

13. A method according to claim 1 , wherein the electrolytic cell is subjected to a suitable potential profile for dissolving the noble metal in the chosen electrolyte system.

14. A method according to claim 1 wherein said current cycles between 0.55V and 1.3 V.

Assignees

• Univ Syddansk

Inventors

• Skou Eivind
• Noergaard Casper
• Stamatin Serban Nicolae

Classifications

• C25C5/02

  from solutions · CPC title

• C25C1/20 Primary

  of noble metals · CPC title

• C22B11/048

  from spent catalysts · CPC title

• C22B11/04

  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) · CPC title

• C22B3/44

  by chemical processes (treatment or purification of solutions by liquid-liquid extraction C22B3/26, by ion-exchange extraction C22B3/42) · CPC title