A method of recovering Pt or Ag or Pt and Ag from sulfate based metal solutions

Patent metadata

Field	Value
Publication number	US-2020141016-A1
Application number	US-201816624993-A
Country	US
Kind code	A1
Filing date	Jun 20, 2018
Priority date	Jun 22, 2017
Publication date	May 7, 2020
Grant date	—

Abstract

Deposited precious metal(s) can be recovered from the electrode or the deposition containing electrode can be used as such.

First claim

1 . A method of recovering Pt or Ag or Pt and Ag from sulfate based process solution rich in sacrificial metal comprising:
a) step 1: electrodeposition of sacrificial metal on an electrode by applying an external potential or current or pulse potential or pulse current to the electrode placed in a sulfate based process solution; b) step 2: a redox replacement of sacrificial metals by a replacement metal, such as Pt or Ag or Pt and Ag, by cutting off or reducing the applied external potential or current used in step 1, wherein Pt or Ag or Pt and Ag present in the solution spontaneously replaces sacrificial metals deposited in step 1, resulting in enrichment of Pt or Ag or Pt and Ag on the electrode; c) optionally repeating steps a) and b) subsequently or by a multistep pattern; and d) recovering Pt or Ag or Pt and Ag from the electrode or using the deposition containing electrode as such.

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

3 . The method according to claim 1 , wherein sulfate based process solution contains other elements, such as Bi, Cu, Pb, Pd, Sn, Te, Se, Co, Na, Ca, Mg, K or combinations thereof.

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

5 . The method according to claim 1 , wherein the recovery takes place in sulfate based solution wherein the replacement metal content is <25 ppm, typically <10 ppm, even more typically <1 ppm, even more typically <0.5 ppm.

6 . The method according to claim 1 , wherein the replacement metal content is below detection limit of typical analysis methods such AAS, ICP-OES.

7 . The method according to claim 1 , wherein the sulfate based solution has a sacrificial metal concentration of >2 g/l, typically >5 g/l, more typically >20 g/l and even more typically >40 g/l.

8 . The method according to claim 1 , wherein the sulfate content of the sulfate based solution is higher than 0.1 M, more typically higher than 0.3 M, even more typically higher than 0.5 M.

9 . The method according to claim 1 , wherein the sulfate based process solution originates from hydrometallurgical process such leaching process for ores or concentrates, electrowinning or electrorefining process, solution purification process, slime treatment process or side-stream treatment process.

10 . The method according to claim 1 , wherein the electrode(s) are made of any conductive or semi-conductive material onto which sacrificial metal can be deposited.

11 . The method according to claim 1 , wherein the electrode(s) are made of 3D carbon material, which is preferably fabricated through pyrolysis of polymers, primarily photoresists including SU-8.

12 . The method according to claim 11 , wherein multiscale roughness of the electrode is created spontaneously during pyrolysis of polymers, primarily photoresists including SU-8, or by micro- and nanostructuring of the polymer films prior to pyrolysis, utilizing for example lithography and embossing techniques, or alternatively, carbon (e.g. glassy carbon or nanotubes) is machined for example by laser, or 3D structures of other materials like silicon can be coated by a carbon.

13 . The method according to claim 1 , wherein the electrode(s) have any suitable shape, such as plate, ring, sheet, mesh, stick or any other applicable form, present in any configuration related to number of electrodes.

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

15 . The method according to claim 1 , wherein the potential in the electrodeposition step is such that sacrificial metal can deposit on the electrode and hydrogen evolution does not prevent the metal recovery.

16 . The method according to claim 1 , wherein the cathodic potential in the electrodeposition step in claim 1 a) is less than 0 V vs. SCE (saturated calomel electrode), typically in between 0 and −2.0 V vs. SCE, more typically between 0.0 V and −1.2 V vs. SCE, and even more typically between −0.3 V and −1.2 V vs. SCE.

17 . The method according to claim 1 , wherein the electrodeposition step in claim 1 a) is performed by potential pulsing between two or more potentials, where the most negative pulsing potential is less than 0 V vs. SCE (saturated calomel electrode), typically in between 0 and −2.0 V vs. SCE, more typically between 0.0 V and −1.2 V vs. SCE, and even more typically between −0.3 V and −1.2 V vs. SCE, while the other pulsing potential can be any potential higher than this most negative potential.

18 . The method according to claim 1 , wherein the absolute value of the externally applied current density in the electrodeposition step in the claim 1 a) is in the range of 0.01-1000 mA/cm2, typically 0.01-300 mA/cm2, more typically 0.01-200 mA/cm2, even more typically 0.01-100 mA/cm2.

19 . The method according to claim 1 , wherein in the electrodeposition step a) has a residence time, which is in the range of 0.01 s-10 min, more typically 0.01 s-30 s, or even more typically 0.01-10 s.

20 . 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 typically just below stripping potential of the replacement metal.

21 . The method according to claim 1 , wherein the redox replacement step b) is finished when the open circuit potential value reaches a predetermined value, which is below 0.6 V vs. SCE, typically below 0.4 V vs. SCE, more typically below 0.35 V vs. SCE, however at potential higher than deposition potential of sacrificial metal.

22 . The method according to claim 1 , wherein redox replacement step 2 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 sacrificial metals such as Zn and/or Ni by the replacement metals such as Pt or Ag or Pt and Ag can take place.

23 . The method according to claim 1 , wherein the redox replacement step in claim 1 b) is finished after a pre-determined time period that allows replacing the sacrificial metal such as Zn and/or Ni with the replacement metals such as Pt and/or Ag, typically after less than 48 hours, more typically after 3 s-24 hours, even more typically after 3 s-2 h, even more typically after 3 s-30 min.

24 . The method according to claim 1 , wherein electrodeposition and redox replacement steps in claim 1 are repeated 1-50 000 times, more typically 1-5 000 times, even more typically 10-1000 times, and still more typically 10-500 times, before recovering the replacement metals from the electrode.

25 . The method according to claim 1 , wherein the method can be finished after or during any of the steps.

26 . The method according to claim 1 , wherein the obtained deposit on the electrode is subjected to leaching, a hydrometallurgical method, a pyrometallurgical method, chemical stripping, physical stripping or electrochemical stripping for recovering Pt and/or Ag from the electrode.

27 . The method according to claim 1 , wherein the sulfate based process solution

Assignees

• Aalto Univ Foundation Sr

Inventors

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

Classifications

• C22B11/042

  Recovery of noble metals from waste materials · CPC title

• C25C1/20 Primary

  of noble metals · CPC title

• C25C7/02

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

• Y02P10/20

  Recycling · CPC title