A PROCESS FOR MANUFACTURING NICKEL SULPHATE

Abstract

A process for manufacturing nickel sulphate by leaching metal particles comprising nickel in an aqueous sulphuric acid solution, said process comprising the steps of: introducing the metal particles in the aqueous sulphuric acid solution introducing an aqueous hydrogen peroxide solution in the aqueous sulphuric acid solution containing the metal particles wherein the aqueous hydrogen peroxide solution is introduced progressively into the aqueous sulphuric acid solution containing the metal particles.

Claims

1. A process for manufacturing nickel sulphate by leaching metal particles comprising nickel in an aqueous sulphuric acid solution, said process comprising the steps of: introducing the metal particles in the aqueous sulphuric acid solution; and introducing an aqueous hydrogen peroxide solution in the aqueous sulphuric acid solution containing the metal particles; wherein the aqueous hydrogen peroxide solution is introduced progressively into the aqueous sulphuric acid solution containing the metal particles.

2. The process according to claim 1, wherein aqueous sulphuric acid solution has a concentration between 20 wt % and 35 wt %.

3. The process according to claim 1, wherein the aqueous hydrogen peroxide solution has a concentration between 30 wt % and 60 wt %.

4. The process according to claim 1, wherein the molar ratio Ni:H.sub.2SO.sub.4:H.sub.2O.sub.2 is between 1:1:1.3 and 1:1:1.1.

5. The process according to claim 1, wherein the molar ratio Ni:H2SO4:H.sub.2O.sub.2 is 1:1.1:1.2

6. The process according to claim 1, wherein the final NiSO.sub.4 concentration is between 80% and 90% of its molar concentration at saturation at room temperature.

7. The process according to claim 1, wherein the aqueous hydrogen peroxide solution is introduced by increments of less than 1% of the total amount of hydrogen peroxide to be added into the aqueous sulphuric acid solution containing the metal particles.

8. The process according to claim 7, wherein said process takes place in a vessel and wherein increments of less than 1% of the total amount of hydrogen peroxide to be added are introduced at the same time in different locations of the vessel.

9. The process according to claim 1, wherein the introduction of hydrogen peroxide into the sulphuric acid solution containing the metal particles starts within a few seconds or minutes after the metal particles are contacted with the sulphuric acid solution.

10. The process according to claim 1, wherein the hydrogen peroxide is introduced in the leaching vessel simultaneously with at least part of the sulphuric acid.

11. The process according to claim 1, wherein the hydrogen peroxide introduction starts before the explosive concentration of hydrogen is reached in the gas phase of/above the leaching vessel.

12. The process according to claim 1, wherein the pH of the leaching medium before the introduction of hydrogen peroxide is below 1 and wherein the pH at the end of the introduction of the required amount of hydrogen peroxide is below 3.

13. The process according to claim 1, wherein the aqueous solution of sulphuric acid is stirred or otherwise agitated under mechanical conditions throughout the introduction of the aqueous hydrogen peroxide solution.

14. The process according to claim 1, wherein the metal particles are substantially dissolved at the end of the introduction of the aqueous hydrogen peroxide solution into the aqueous sulphuric acid solution.

15. The process according to claim 1, wherein the introduction of the aqueous hydrogen peroxide solution takes place at temperatures from 65 to 75° C.

16. The process according to claim 1, wherein said process takes place under a pressure of oxygen or air.

17. The process according to claim 1, wherein the aqueous hydrogen peroxide solution is introduced in the aqueous sulphuric acid solution as close as possible the metal particles.

18. The process according to claim 1, wherein ultrasounds are used during the introduction of the aqueous hydrogen peroxide solution in the aqueous sulphuric acid solution.

19. The process according to claim 1, wherein after the introduction of the aqueous hydrogen peroxide solution in the aqueous sulphuric acid solution, the resulting NiSO4 solution is brought or kept at atmospheric pressure and cooled down to room temperature before being further processed to isolate the NiSO4 produced, or before being used as a feed material for the production of cathode material.

Description

EXAMPLE 1

Materials Used

[0047] Ni powder of a particle size 75-100 μm and a purity of 99.8%
H2SO4 aqueous solution 98 wt %
H2O2 aqueous solution with a concentration of 48.5 wt %
Caro's acid prepared with a molar ratio of H2SO4:H2O2 of 2.5

Experimental Conditions

[0048] Ni powder, H2SO4 and additional DMW (the case being) were introduced in the leaching vessel and were ice cooled before the drop wise introduction of the H2O2 solution.
The reaction conditions were thereafter as follows:

Temperature: 70° C.

[0049] Reaction time: 4 hours
Every hour, samples of the reaction medium were taken and analysed for their dissolved Ni content by ICP. The conversion (%) was then calculated in function of said measured dissolved Ni content as follows:

Conversion(%)=[(Ni max−Ni measured)/Ni max]×100

wherein Ni max is the amount (in grams or moles for instance) of Ni that would be dissolved at 100% conversion.

Experiments 1 to 3

[0050] The amounts of reactive species and water used in these experiments are detailed in Table 1 below.

TABLE-US-00001 TABLE 1 Experiment No Ingredient mol g 1 Nickel 99.8% 0.5101 30.00 H2SO4 98% 0.5101 51.05 H2O2 48.5% 0.6121 42.89 Water — — 2 Nickel 99.8% 0.4251 25.00 H2SO4 98% 0.4251 42.54 H2O2 48.5% 0.5101 35.78 Water 5.3528 96.43 3 Nickel 99.8% 0.4251 25.00 H2SO4 98% 0.4251 42.54 H2O2 48.5% — — Water 5.3649 96.65
Experiment 1 was performed with a 98 wt % H2SO4 starting solution, while experiments 2 and 3 used a 30 wt % H2SO4 starting solution.
FIG. 1 attached plots the conversion over time for experiment 1 (curve with the squares), experiment 2 (curve with the crosses) and experiment 3 (curve with the diamonds), as well as for an experiment conducted with Caro's acid in the same experimental conditions (curve with the triangles). It is quite clear from this Figure that the combination of H2SO4 30 wt % with H2O2 at a molar ratio H2O2:H2SO4 of 1.2:1 gives much better results, even quite surprisingly better than with H2SO4 98 wt % even in the presence of H2O2 at the same molar ratio.

EXAMPLES 2 TO 4: RESULTS ON NI POWDER

Materials Used:

[0051] Nickel powder (99.8%) with the following granulometry: 90%<138.6 μm, 50%<101.1 μm, 10%<73.7 μm

[0052] Sulphuric acid (98%) from Merck

[0053] Hydrogen peroxide ST50 from Solvay

Experimental Procedure:

[0054] 25 grams of nickel powder were introduced in the reactor with the required amount of sulphuric acid and mixed under mechanical stirring at 500 r.p.m. Once the reactor was closed, the hydrogen peroxide was added progressively, and the temperature of the reaction was recorded. Samples of the solution were taken every 10 minutes and diluted in DMW for the measurement of the dissolved nickel by ICP-OES. The last sample was taken 10 minutes after the last drop of hydrogen peroxide was added.

EXAMPLE 2: INFLUENCE OF THE PEROXIDE DOSING RATE

[0055] The hydrogen peroxide was dosed dropwise to the reaction mixture and the temperature was recorded.
Conditions of the test:

[0056] Sulphuric acid: 30%

[0057] Hydrogen peroxide: ST50 (50 wt %)

[0058] Molar ratio: Stoichiometric

The range of dosing rate selected for the study was between 0.5 and 1.0 ml/min of H2O2 ST50.
The results are plotted in FIG. 2 attached, which namely shows the evolution over time of the conversion (curve with triangles for 1 ml/min and stars for 0.5 ml/min) and of temperature (curve with small diamonds for 1 ml/min and small vertical lines for 0.5 ml/min).
The conversion of nickel powder to nickel (II) drops from 99.2% to 92.8% when the dosing rate increases from 0.5 ml/min to 1 ml/min. The leaching rate increases with the dosing rate; however, the temperature of the reaction increases as well, which might decompose the hydrogen peroxide, especially at temperatures above 80° C., and decrease the efficiency of the hydrogen peroxide.
Some bubbles are generated in the leached product due to the unreacted peroxide.

EXAMPLE 3: INFLUENCE OF THE SULPHURIC ACID CONCENTRATION

Conditions:

[0059] Hydrogen peroxide: 50%

[0060] Molar ratio: Stoichiometric

[0061] Peroxide dosing rate: 0.5 ml/min

The selected range of sulphuric acid selected for the study was 30%-40% in weight.
The results are plotted in FIG. 3 attached, which namely shows the evolution over time of the conversion (curve with crosses for 40% H2SO4 and stars for 30% H2SO4) and of temperature (curve with small dots for 40% H2SO4 and with small vertical lines for 30% H2SO4).
The crystalization of nickel sulphate started in the middle of the reaction with 40% sulphuric acid, from minute 30, which made it difficult for the sampling.
The temperature profile of the reaction was very similar; hence it is mainly affected by the dosing rate and not the concentration of sulphuric acid.

EXAMPLE 4: INFLUENCE OF THE SULPHURIC ACID MOLAR RATIO

[0062] With the aim of increasing the stability of the hydrogen peroxide and improve the performance of the reaction, the addition of a small excess of sulphuric acid was assessed.

Conditions:

[0063] Sulphuric acid: 30%

[0064] Hydrogen peroxide: 50%

[0065] Peroxide dosing rate: 1 ml/min

The amount of excess added was Ni:H2SO4 1:1.1 (molar ratio).
The results are plotted in FIG. 4 attached, which namely shows the evolution over time of the conversion (curve with triangles for a stoichiometric ratio and squares for the molar excess) and of temperature (curve with diamonds for a stoichiometric ratio and with dots for the molar excess).
The conversion increased from 92.8% to 99.5% with just the addition of 1.1 excess of molar ratio of H2SO4. No bubbles were formed in the leached solution.

EXAMPLE 5: INFLUENCE OF PARTICLE SIZE

[0066] The Ni materials used are: [0067] For the powder: same as in Examples 2 to 4 [0068] For the briquettes: Nickel briquettes (99.8%); Size: 4×3×2 cm (weight 93 g-119 g)

Conditions:

[0069] Sulphuric acid: 30% [0070] Hydrogen peroxide: 50% [0071] Peroxide dosing rate: 0.5 ml/min
For the powder, the same procedure was followed as in Examples 2 to 4.
For the briquettes, due to their size, the tests were performed with one briquette per test and heating to 70° C. was required. The briquette was introduced into a double jacket reactor with the sulphuric acid solution and mixed with a mechanical stirrer at 300 rpm. The reactor was then closed and the peroxide was dosed progressively. Samples were taken every hour for the analysis of Ni (II) by ICP-OES.
The last sample was taken 10 minutes after the last drop of hydrogen peroxide was added.

[0072] FIG. 5 attached plots the conversion over time for the powder (curve with the diamonds) and briquettes (curve with the triangles).

EXAMPLE 6: EFFICIENCY ON A MIX OF METALS

[0073] As the cathode material of batteries is made of the sulphate salt of Ni, Mn and Co in the molar ration (8:1:1), the process of the invention was tested on such a mixture of metals in powder form with a maximal particle size of 45 μm and a purity of about 99.5%.

Conditions:

[0074] Peroxide dosing rate: 0.5 ml/min

H2SO4: 30%

Results:

[0075] 100% dissolution of the 3 metals after about 1 hour: see FIG. 6 attached (the diamonds are for Ni, the squares for Mn and the triangles for Co).

EXAMPLE 7: INFLUENCE OF THE DOSING RATE ON BRIQUETTES

Test Conditions:

[0076] Sample: Nickel briquettes as in Example 5

[H2SO.SUB.4.]: 30%

Temperature: 70° C.

[0077] Molar ratio: Stoichiometric
Peroxide grade: ST50
Mechanical stirring: 200 RPM
FIG. 7 attached plots the conversion over time for a dosing rate of 0.5 ml/min (curve with the diamonds), 0.3 ml/min (curve with the squares) and 0.2 ml/min (curve with the triangles).

EXAMPLE 8: PROCESS OPTIMIZATION WITH BRIQUETTES

[0078] Sample: Nickel briquettes as in Example 5
With the aim of evaluating the impact of each parameter in the process, a design of experiments was performed.
The selected parameters for the study were:

[0079] Dosing rate (ml/min): 0.3-0.5

[0080] Sulphuric acid concentration (%): 24-30

[0081] Temperature (° C.): 50-70 Fixed parameters:

[0082] Hydrogen peroxide: 50 wt %

[0083] Molar ratio Ni:H2SO4:H2O2 1:1.1:1.2

[0084] Mechanical stirring: 300 rpm

The matrix of the tests performed is summarized in Table 1 below.

TABLE-US-00002 TABLE 1 Experiment DOE1 DOE2 DOE3 DOE4 Temperature (° C.) 50 70 70 50 Dosing rate 0.5 0.5 0.3 0.3 (ml/min) H2SO4 (%) 24 30 24 30
FIG. 8 attached plots the conversion over time for experiment DOE1 (curve with the diamonds), experiment DOE2 (curve with the squares), experiment DOE3 (curve with the triangles), and experiment DOE4 (curve with the crosses). In the conditions of DOE2, there was some NiSO4 precipitation at the end of the experiment.
Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.