US-20260125279-A1 - METHOD FOR PREPARING HIGH-PURITY MIXED NICKEL AND COBALT SULPHATE

Abstract

A method for preparing high-purity mixed nickel and cobalt sulphate, the method comprising the recovery of nickel and cobalt sulphate crystals from an organic phase rich in both nickel and cobalt by way of contacting the nickel and cobalt rich organic phase with an aqueous strip solution of sufficient H2SO4 concentration to extract nickel and cobalt from the organic phase and of sufficient Ni 2+ and Co 2+ concentration to precipitate nickel and cobalt sulphate crystals and form a nickel and cobalt lean organic phase. Also disclosed is a method for the optimisation of feed for downstream processing.

Inventors

• Christopher Brett Ward
• Aaron Christopher WHITE
• Karel John Osten

Assignees

• IGO LIMITED

Dates

Publication Date

20260507

Application Date

20231005

Priority Date

20221007

Claims (20)

1. 1 . A method for preparing high-purity mixed nickel and cobalt sulphate, the method comprising recovery of nickel and cobalt sulphate crystals from an organic phase rich in both nickel and cobalt by way of contacting the nickel and cobalt rich organic phase with an aqueous strip solution of sufficient H 2 SO 4 concentration to extract nickel and cobalt from the organic phase and of sufficient Ni 2+ and Co 2+ concentration to precipitate nickel and cobalt sulphate crystals and form a nickel and cobalt lean organic phase.
2. 2 . The method of claim 1 , wherein the mixed nickel and cobalt sulphate crystals comprise nickel sulphate hexahydrate and cobalt sulphate heptahydrate, respectively.
3. 3 . The method of claim 1 , wherein a purity of mixed nickel and cobalt sulphate crystals prepared is such that the nickel to trace element ratio, excluding cobalt and manganese, is >20,000 times.
4. 4 . The method of claim 1 , wherein the method further comprises separating the nickel and cobalt sulphate crystals from the nickel and cobalt lean organic phase.
5. 5 . The method of claim 1 , wherein the aqueous strip solution: (i) comprises concentrated H 2 SO 4 ; or (ii) has an H 2 SO 4 concentration of between 10 to 450 g/L.
6. 6 . The method of claim 1 , wherein the nickel and cobalt rich organic phase includes a coordination complex of nickel and cobalt and an organic extractant, wherein the organic extractant dissociates from the nickel and cobalt in the presence of a sufficient concentration of H + ions.
7. 7 . The method of claim 6 , wherein the organic extractant is selected from the group consisting of organophosphorous acids, chelating oximes or hydroxyoximes, carboxylic acids, and high molecular weight amines.
8. 8 . The method of claim 1 , wherein the method further comprises a nickel and cobalt recovery step, wherein an aqueous acidic nickel and cobalt containing solution is contacted with an organic phase including an organic extractant selectively extract nickel and cobalt from the aqueous solution into the organic phase to form a nickel and cobalt lean aqueous raffinate and the nickel and cobalt rich organic phase, and separating the raffinate and the nickel and cobalt rich organic phase.
9. 9 . The method of claim 8 , wherein the aqueous acidic nickel and cobalt containing solution is: (i) a pregnant leach solution; (ii) a pregnant leach solution obtained from a leach of a sulphide ore or concentrate; (iii) a pregnant leach solution obtained from a leach of a sulphide ore or concentrate and a mixed hydroxide precipitate.
10. 10 . The method of claim 8 , wherein the aqueous acidic nickel and cobalt containing solution will have had at least a portion of any impurities present substantially removed therefrom prior to the nickel and cobalt recovery step.
11. 11 . The method of claim 10 , wherein the impurities removed include iron and aluminium.
12. 12 . The method of claim 8 , wherein the method further comprises recirculating of the aqueous strip solution, depleted in sulfuric acid, but containing relatively high Ni2+ and Co2+ concentrations, to ensure solution saturation levels of nickel sulphate hexahydrate and cobalt sulphate heptahydrate are exceeded with addition of fresh nickel and cobalt loaded organic phase.
13. 13 . The method of claim 12 , wherein the aqueous strip solution has a Ni2+ concentration of about 80-100 g/L and a Co2+ concentration of: (i) about 2-13 g/L; or (ii) about 8-13 g/L.
14. 14 . The method of claim 1 , wherein the method further comprises passing the nickel sulphate and cobalt sulphate crystals produced to a dissolution/repulping step.
15. 15 . The method of claim 14 , wherein the dissolution/repulping step is conducted with high purity water.
16. 16 . The method of claim 14 , wherein from the dissolution/repulping step, a solution of the nickel sulphate and cobalt sulphate crystals is passed to a polishing step.
17. 17 . The method of claim 16 , wherein a purity of the solution from the polishing step is about 120 g/L nickel.
18. 18 . The method of claim 1 , wherein the mixed nickel sulphate and cobalt sulphate solution is utilised as feed for the production of PCAM.
19. 19 . The method of claim 18 , wherein manganese sulphate is retained in the mixed nickel sulphate and cobalt sulphate solution as feed for the production of PCAM.
20. 20 . A mixed nickel and cobalt sulphate produced by the method described in claim 1 .

Description

FIELD OF THE INVENTION The present invention relates to a method for preparing high-purity mixed nickel and cobalt sulphate. Further, the present invention also relates to a high-purity mixed nickel and cobalt sulphate produced by this method. BACKGROUND ART In the Applicant's previous International Patent Application PCT/AU2019/051044 (WO 2020/061639) there is described a method of recovering nickel sulphate hexahydrate (NiSO4·6H2O). It is described therein that the nickel sulphate hexahydrate should be high purity. By ‘high purity’ it is meant a nickel content of at least 21%, and preferably between 21 and 24% and most preferably around 22-23%, in the nickel sulphate hexahydrate. As would be understood by the skilled person this includes a nickel content of 22.0%, 22.1%, 22.2%, 22.3%, 22.4%, 22.5%, 22.6%, 22.7%, 22.8%, 22.9% and 23%, in the nickel sulphate hexahydrate. It is also meant that high purity/battery-grade nickel sulphate hexahydrate is also very low in trace metal element levels, including no more than 350 ppm Co, no more than 10 ppm Cu, no more than 25 ppm Ca, no more than 15 ppm Cr, no more than 15 ppm Fe, no more than 35 ppm Mg, no more than 15 ppm Mn, no more than 15 ppm Pb and no more than 15 ppm Zn. Preferably, high purity/battery-grade nickel sulphate hexahydrate includes no more than 250 ppm Co, no more than 5 ppm Cu, no more than 15 ppm Ca, no more than 10 ppm Cr, no more than 10 ppm Fe, no more than 25 ppm Mg, no more than 10 ppm Mn, no more than 10 ppm Pb and no more than 10 ppm Zn. High purity nickel sulphate hexahydrate is an important source of nickel for use in advanced lithium-ion batteries. It is therefore also referred to as ‘battery-grade’ nickel sulphate, wherein battery-grade nickel sulphate has the same nickel sulphate hexahydrate content as detailed above for high purity nickel sulphate hexahydrate, and is used interchangeably. In a first aspect of the invention described in the Applicant's previous International Patent Application PCT/AU2019/051044 (WO 2020/061639), the entire content of which is explicitly incorporated herein by reference, there is provided a method of recovering NiSO4·6H2O crystals from a nickel rich organic phase, the method including: (i) contacting a nickel rich organic phase with an aqueous strip solution of sufficient H2SO4 concentration to extract nickel from the organic phase and of sufficient Ni2+ concentration to precipitate NiSO4·6H2O crystals and form a nickel lean organic phase. The skilled person will appreciate that the concentration of H2SO4 and Ni2+ in the strip solution will vary depending on the particular conditions under which the method is carried out (e.g. temperature, pressure, presence of other ions). In an embodiment, the strip solution has a Ni2+ concentration of 60 g/L or greater. More preferably, the strip solution has a Ni2+ concentration of 70 g/L or greater. Most preferably, the strip solution has a Ni2+ concentration of 80 g/L or greater. Additionally, or alternatively, the strip solution has a Ni2+ concentration of up to 100 g/L. In an embodiment, the strip solution has an H2SO4 concentration of 300 g/L or greater, or 350 g/L or greater, or the strip solution has a H2SO4 concentration of from about 350 up to about 450 g/L. In an alternative embodiment, the strip solution has an H2SO4 concentration of 300 g/L or less. Preferably, the strip solution has a H2SO4 concentration of 10-300 g/L. In an embodiment, the strip solution has a SO42− and Ni2+ concentration that are together at or near the solubility limit of NiSO4·6H2O. By near the solubility limit it is meant that the concentration is such that at least 90 wt % of the nickel extracted from the organic phase is precipitated as NiSO4·6H2O. Preferably, 95 wt % of the nickel extracted from the organic phase is precipitated as NiSO4·6H2O. More preferably, 98 wt % of the nickel extracted from the organic phase is precipitated as NiSO4·6H2O. Most preferably, 99 wt % of the nickel extracted from the organic phase is precipitated as NiSO4·6H2O. In an embodiment, the nickel rich organic phase is immiscible with water. In an embodiment, the method further includes separating the NiSO4·6H2O crystals from the nickel lean organic phase. In an embodiment, the nickel rich organic phase includes at least: nickel (such as in the form of Ni2+), an organic extractant, and an organic diluent. Preferably, the nickel rich organic phase includes a coordination complex of nickel and an organic extractant, wherein the organic extractant dissociates from the nickel in the presence of a sufficient concentration of H+ ions (such as those derived from the dissociation of H2SO4). More preferably, the H+ ions are provided in an ion exchange process with the NiSO4. In forms of the above embodiment, the organic extractant is selected from the group consisting of: organophosphorus acids, chelating oximes or hydroxyoximes, carboxylic acids, and high molecular weight amines (such as n-octylaniline, tri-