Method of recovering Pt or Ag or Pt and Ag from sulfate based metal solutions

Patent metadata

Field	Value
Publication number	US-11486047-B2
Application number	US-201816624993-A
Country	US
Kind code	B2
Filing date	Jun 20, 2018
Priority date	Jun 22, 2017
Publication date	Nov 1, 2022
Grant date	Nov 1, 2022

Abstract

The invention relates to a method of recovering Pt or Ag or Pt and Ag from a sulfate solution on an electrode. In particular, the invention concerns a method for recovering Pt or Ag or Pt and Ag from base metal bearing process solution, particularly from a hydrometallurgical sacrificial metal bearing solution containing Zn and/or Ni. In general, the method of the present invention can be used for recovery of precious metals, which are dissolvable in sulfuric acid, from sulfate media based solutions. In addition to Pt and Ag, especially Pd should be mentioned.Deposited precious metal(s) can be recovered from the electrode or the deposition containing electrode can be used as such.

First claim

The invention claimed is:

1. A method of recovering a replacement metal from a sulfate-based process solution comprising:
(a) electrodepositing a sacrificial metal on an electrode by applying a potential or current to the electrode, wherein the potential or current comprises an external potential or current or an external pulse potential or pulse current, and wherein the electrode is placed in a sulfate-based process solution comprising a replacement metal and the sacrificial metal;
(b) conducting a redox replacement of the sacrificial metal by the replacement metal by cutting off or reducing the applied potential or current, wherein the replacement metal present in the sulfate-based process solution spontaneously replaces the sacrificial metal deposited in step (a), resulting in enrichment of the replacement metal on the electrode, and wherein the replacement metal is Pt or Ag or Pt and Ag;
c) optionally repeating steps (a) and (b) subsequently or by a multistep pattern; and
d) recovering the replacement metal from the electrode or using the deposition containing electrode as such.

2. The method according to claim 1 , wherein the sacrificial metal comprises Ni and/or Zn.

3. The method according to claim 1 , wherein sulfate-based process solution further comprises an additional element.

4. The method according to claim 1 , wherein Pd is recovered on the electrode from the sulfate-based process solution.

5. The method according to claim 1 , wherein the recovering takes place in sulfate-based solution, wherein the content of the replacement metal is <25 ppm.

6. The method according to claim 1 , wherein a concentration of the replacement metal is below a detection limit in the sulfate-based process solution.

7. The method according to claim 1 , wherein the sulfate-based solution has a sacrificial metal concentration >2 g/l.

8. The method according to claim 1 , wherein the sulfate-based process solution originates from a hydrometallurgical process, a leaching process for ores or concentrates, an electrowinning or electrorefining process, a solution purification process, a slime treatment process or a side-stream treatment process, and wherein a sulfate content of the sulfate-based process solution is greater than 0.1 M.

9. The method according to claim 1 , wherein the electrode comprises a conductive or semi-conductive material onto which the sacrificial metal can be deposited.

10. The method according to claim 1 , wherein the electrode comprises a three dimensional (3D) carbon material fabricated through pyrolysis of polymers.

11. The method according to claim 1 , wherein the electrodeposition step is conducted at a constant current or constant potential, by pulsing the current, pulsing the potential, or by varying the potential or current in a range in which the sacrificial metal deposits on the electrode.

12. The method according to claim 1 , wherein the potential or current in the electrodeposition step is such that sacrificial metal deposits on the electrode and hydrogen evolution does not prevent the metal recovery, and wherein a cathodic potential in the electrodeposition step is less than 0 V vs. SCE (saturated calomel electrode).

13. The method according to claim 1 , wherein an absolute value of a current density of the applied current density in the electrodeposition is in the range of 0.01-1000 mA/cm 2 .

14. The method according to claim 1 , wherein in the electrodeposition step (a) has a residence time in the range of 0.01 s-30 s.

15. The method according to claim 1 , wherein the redox replacement step (b) is finished after a pre-determined time or when the open circuit potential value reaches a pre-determined value, which is below 0.6 V vs. SCE, however at a potential higher than a deposition potential of the sacrificial metal.

16. The method according to claim 1 , wherein redox replacement step (b) can be conducted by cutting-off the applied potential or current or reducing the current to such a low value or potential close to open circuit potential that the spontaneous replacement of the sacrificial metal by the replacement metal can take place.

17. The method according to claim 1 , wherein the redox replacement step (b) is finished after a pre-determined time period that allows replacement of the sacrificial metal with the replacement metal after less than 48 hours.

18. The method according to claim 1 , wherein electrodeposition and redox replacement steps in claim 1 , are repeated 1-1000 times before recovering the replacement metal from the electrode.

19. The method according to claim 1 , wherein the electrode is subjected to leaching, a hydrometallurgical method, a pyrometallurgical method, chemical stripping, physical stripping or electrochemical stripping to recover the replacement metal from the electrode.

20. The method according to claim 1 , wherein the sulfate-based process solution has a concentration ratio between the sacrificial metal and the replacement metal of >100.

21. The method according to claim 1 , wherein the sulfate-based process solution is derived from a hydrometallurgical process.

Assignees

• Aalto Univ Foundation Sr

Inventors

• Lundström Mari
• Yliniemi Kirsi
• Halli Petteri
• Franssila Samuli
• Jokinen Ville
• Heikkinen Joonas

Classifications

• Y02P10/20

  Recycling · CPC title

• C25C1/20 Primary

  of noble metals · CPC title

• C22B11/042

  Recovery of noble metals from waste materials · CPC title

• C25C7/02

  Electrodes (consumable anodes for the refining the metals C25C1/00 - C25C5/00); Connections thereof · CPC title