Electronic-grade cobalt sulfate, purification method thereof, and application thereof

Abstract

The present invention discloses an electronic-grade cobalt sulfate and its purification method and application, belonging to the field of chemical process technology. The electronic-grade cobalt sulfate purification method of the present invention comprises the following steps: S1, deoiling: deoiling a crude cobalt sulfate solution through an adsorbent to obtain a deoiled cobalt sulfate solution; S2, ion exchange: purifying the deoiled cobalt sulfate solution through an ion exchanger to obtain a purified cobalt sulfate solution; S3, recrystallization: evaporating and concentrating the purified cobalt sulfate solution, cooling and crystallizing it, and controlling the crystal yield to be greater than 0 and less than or equal to 60%, to obtain electronic-grade cobalt sulfate crystals. The purification method of the present invention can effectively remove impurities in the crude cobalt sulfate solution through the steps of deoiling, ion exchange and recrystallization, combined with the control of the crystal yield, to obtain electronic-grade cobalt sulfate crystals and an electronic-grade cobalt sulfate solution with low total metal impurity content and low total organic carbon content. The electronic-grade cobalt sulfate crystals and the electronic-grade cobalt sulfate solution have stable and good performance, and are particularly widely used in the field of nano-chip integrated circuits.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical processes, and in particular relates to electronic-grade cobalt sulfate and a purification method and application thereof. Background Art

[0002] Cobalt sulfate (CoSO4), as an important chemical raw material, has a wide range of applications in battery materials, catalysts, pigments, and the ceramic industry. In recent years, with the rapid development of the new energy sector, higher requirements have been placed on the purity of cobalt sulfate. Cobalt sulfate is an important raw material for preparing battery cathode material precursors and has important applications in the preparation of lithium cobalt oxide compounds and nickel-cobalt-manganese ternary compounds. However, current industrial-grade cobalt sulfate salts are difficult to meet the production requirements of electronic-grade compounds, necessitating further research into the purification process and methods of cobalt sulfate.

[0003] In the cobalt sulfate purification process, removing impurities, especially metallic and organic impurities, is crucial. Traditional methods such as precipitation, filtration, and solvent extraction often struggle to achieve highly selective impurity removal, resulting in a low-purity final product. This prevents the production of electronic-grade cobalt sulfate, making it difficult to meet the requirements of high-end applications. Summary of the Invention

[0004] In order to overcome at least one of the problems existing in the above-mentioned prior art, one of the objects of the present invention is to provide a method for purifying electronic-grade cobalt sulfate. The purification method is simple in process and the obtained electronic-grade cobalt sulfate has high purity and low impurity content.

[0005] A second object of the present invention is to provide electronic grade cobalt sulfate obtained by the above purification method.

[0006] A third object of the present invention is to provide an application of the electronic-grade cobalt sulfate in the field of nano-scale chip integrated circuits.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A first aspect of the present invention provides a method for purifying electronic-grade cobalt sulfate, comprising the following steps:

[0009] S1. Degreasing: Degreasing the crude cobalt sulfate solution by passing it through an adsorbent to obtain a degreasing cobalt sulfate solution;

[0010] S2. Ion exchange: purifying the cobalt sulfate deoiling liquid through an ion exchanger to obtain a purified cobalt sulfate liquid;

[0011] S3, recrystallization: evaporating and concentrating the purified cobalt sulfate solution, cooling and crystallizing the solution, and controlling the crystal yield to be greater than 0 and less than or equal to 60%, to obtain electronic grade cobalt sulfate crystals.

[0012] In the purification method of the present invention, the deoiling step can effectively remove organic impurities in the crude cobalt sulfate solution, significantly reducing the total organic carbon (TOC) content in the resulting deoiled cobalt sulfate solution; the ion exchange step can effectively remove metal impurities in the solution, significantly reducing the total metal impurity content in the resulting purified cobalt sulfate solution; and the recrystallization step can further remove metal impurities by controlling the crystal yield to no more than 60%, further reducing the total metal impurity content in the resulting electronic-grade cobalt sulfate crystals. Therefore, the purification method of the present invention can produce electronic-grade cobalt sulfate crystals with high purity, low total metal impurity content, and low total organic carbon content.

[0013] In some specific embodiments of the present invention, in step S1, the cobalt ion concentration of the crude cobalt sulfate solution is 70-90 g / L.

[0014] In some specific embodiments of the present invention, in step S1, the crude cobalt sulfate solution contains metallic impurities and / or organic impurities; the metallic impurities include other metallic elements except Co.

[0015] In some specific embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include at least one element selected from the group consisting of Ca, Cd, Cr, Fe, Mg, Mn, Mo, Na, Ni, Zn, Al, As, Cu, Pb, K, Au, Ti, In, Sn, Tl, and Hg.

[0016] In some specific embodiments of the present invention, in step S1, the total content of metal impurities in the crude cobalt sulfate solution is ≥900 μg / L.

[0017] In some specific embodiments of the present invention, in step S1, the total organic carbon content in the crude cobalt sulfate solution is ≥10 mg / L.

[0018] In some specific embodiments of the present invention, in step S1, the adsorbent is activated carbon.

[0019] In some specific embodiments of the present invention, the activated carbon is obtained by an impurity removal method comprising the following steps: primary washing: washing the activated carbon raw material with dilute sulfuric acid and soaking for 20 to 30 hours to obtain primary activated carbon; secondary washing: washing the primary activated carbon with ultrapure water to obtain secondary activated carbon and a water washing liquid, and washing in this step until the conductivity of the water washing liquid is ≤10μS; tertiary washing: washing the secondary activated carbon with a cobalt sulfate solution to obtain activated carbon after impurities are removed and a cobalt sulfate washing liquid, and washing in this step until the difference between the total content of metal impurities in the cobalt sulfate washing liquid and the total content of metal impurities in the cobalt sulfate solution is ≤30μg / L.

[0020] In some specific embodiments of the present invention, in step S2, the cobalt sulfate deoiling liquid passes through the ion exchanger at a rate of 50 to 100 L / h.

[0021] In some specific embodiments of the present invention, in step S2, the pH value of the cobalt sulfate deoiling solution when passing through the ion exchanger is 1.5-4.

[0022] In some specific embodiments of the present invention, in step S2, the ion exchanger is selected from a cation exchange resin.

[0023] In some specific embodiments of the present invention, in step S2, the particle size of the ion exchanger is 0.1-2 mm.

[0024] In some specific embodiments of the present invention, in step S2, the volumetric full exchange capacity of the ion exchanger is 1 to 20 mmol / mL.

[0025] The second aspect of the present invention provides an electronic grade cobalt sulfate crystal obtained by the purification method described in the first aspect of the present invention.

[0026] The third aspect of the present invention provides an electronic-grade cobalt sulfate solution obtained by mixing the electronic-grade cobalt sulfate described in the second aspect of the present invention with water.

[0027] In some specific embodiments of the present invention, the cobalt ion concentration of the electronic grade cobalt sulfate solution is 30-50 g / L.

[0028] In some specific embodiments of the present invention, the total metal impurity content of the electronic-grade cobalt sulfate solution is ≤200 μg / L.

[0029] In some specific embodiments of the present invention, the total organic carbon content of the electronic-grade cobalt sulfate solution is ≤5 mg / L.

[0030] In some specific embodiments of the present invention, the pH value of the electronic grade cobalt sulfate solution is 4-6.

[0031] A fourth aspect of the present invention provides an application of the electronic-grade cobalt sulfate crystals described in the second aspect of the present invention, or the electronic-grade cobalt sulfate solution described in the third aspect of the present invention in the field of nanoscale chip integrated circuits.

[0032] The beneficial effects of the present invention are as follows: the purification method of the present invention can effectively remove impurities in a crude cobalt sulfate solution through the steps of oil removal, ion exchange and recrystallization, combined with the control of crystal yield, to obtain electronic-grade cobalt sulfate crystals and an electronic-grade cobalt sulfate solution with low total metal impurity content and low total organic carbon content. The electronic-grade cobalt sulfate crystals and the electronic-grade cobalt sulfate solution have stable and good performance and are widely used, particularly in the field of nano-scale chip integrated circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the process of purifying cobalt sulfate in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] The following describes in detail embodiments of the present invention. The embodiments are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention.

[0035] A first aspect of an embodiment of the present invention provides a method for purifying cobalt sulfate, which specifically comprises the following steps:

[0036] S1. Degreasing: Degreasing the crude cobalt sulfate solution by passing it through an adsorbent to obtain a degreasing cobalt sulfate solution;

[0037] S2. Ion exchange: purifying the cobalt sulfate deoiling liquid through an ion exchanger to obtain a cobalt sulfate purified liquid;

[0038] S3. Recrystallization: The purified cobalt sulfate solution is evaporated and concentrated, cooled and crystallized, and the crystal yield is controlled to be greater than 0 and less than or equal to 60% to obtain electronic grade cobalt sulfate crystals.

[0039] In the purification method of the embodiment of the present invention, the deoiling step can effectively remove organic impurities in the crude cobalt sulfate solution, significantly reducing the total organic carbon (TOC) content in the obtained cobalt sulfate deoiling solution; the ion exchange step can effectively remove metal impurities in the solution, significantly reducing the total content of metal impurities in the obtained cobalt sulfate purified solution; and the recrystallization step can control the crystal yield to no more than 60%, further removing metal impurities, and further reducing the total content of metal impurities in the electronic-grade cobalt sulfate crystals obtained. Therefore, the purification method of the embodiment of the present invention can obtain electronic-grade cobalt sulfate crystals with high purity, low total content of metal impurities, and low total organic carbon content.

[0040] The crystal yield of the recrystallization process will affect the impurity removal effect. Controlling the crystal yield below 60% can ensure that the metal impurity removal effect is good. If the crystal yield is too high, the metal impurity removal effect is poor, and the total metal impurity content in the obtained electronic-grade cobalt sulfate solution is high, which is difficult to meet application requirements; and if the crystal yield is too low, the amount of the electronic-grade cobalt sulfate crystals obtained is less, the production efficiency is low, and the cost is high. Therefore, controlling the appropriate crystal yield of the recrystallization process can obtain electronic-grade cobalt sulfate crystals and electronic-grade cobalt sulfate solution with high purity and low total metal impurity content, and high production efficiency, controllable cost, which is conducive to large-scale production. In the present invention, it is necessary to keep the crystal yield greater than 0, and the specific crystal yield lower limit can be selected according to actual needs.

[0041] In some embodiments of the present invention, in step S3, the crystal yield is 10-60%; in some specific embodiments of the present invention, in step S3, the crystal yield is 15-55%; in some examples of the present invention, in step S3, the crystal yield is 20-50%; non-limiting specific examples are 25%, 30%, 35%, 40% or 45%.

[0042] In some embodiments of the present invention, in step S1, the cobalt ion concentration of the crude cobalt sulfate solution is 70-90 g / L; in some specific embodiments of the present invention, in step S1, the cobalt ion concentration of the crude cobalt sulfate solution is 72-88 g / L; in some examples of the present invention, in step S1, the cobalt ion concentration of the crude cobalt sulfate solution is 75-85 g / L; non-limiting specific examples are 76 g / L, 78 g / L, 80 g / L, 82 g / L or 84 g / L.

[0043] The cobalt ion concentration in the crude cobalt sulfate solution affects the subsequent purification effect and difficulty. The present invention controls the cobalt ion concentration within the range of 70 to 90 g / L, which is beneficial for controlling the impurity content within a controllable range and effectively removing it through subsequent purification steps to obtain high-purity cobalt sulfate.

[0044] In some embodiments of the present invention, in step S1, the crude cobalt sulfate solution is obtained by mixing crude cobalt sulfate with water; in some specific embodiments of the present invention, in step S1, the crude cobalt sulfate is selected from cobalt sulfate heptahydrate.

[0045] In some embodiments of the present invention, the mass ratio of crude cobalt sulfate to water in the crude cobalt sulfate solution is 1:(1-4); in some specific embodiments of the present invention, the mass ratio of crude cobalt sulfate to water in the crude cobalt sulfate solution is 1:(1.2-3.5); in some examples of the present invention, the mass ratio of crude cobalt sulfate to water in the crude cobalt sulfate solution is 1:(1.5-3); non-limiting specific examples include 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.5 or 1:2.8.

[0046] The specific mass ratio of crude cobalt sulfate to water is determined based on the purity of the crude cobalt sulfate. This ratio is adjusted to ensure that the resulting crude cobalt sulfate solution meets the requirements, particularly to achieve a specific cobalt ion concentration. Furthermore, the purity of the crude cobalt sulfate also affects the impurity content in the purification system. High crude cobalt sulfate purity reduces impurity levels and makes purification easier; low purity increases the difficulty of purification.

[0047] In some embodiments of the present invention, in step S1, the crude cobalt sulfate solution contains metal impurities and / or organic impurities; in some specific embodiments of the present invention, in step S1, the crude cobalt sulfate solution contains metal impurities and organic impurities.

[0048] The metal impurities in the present invention include other metal elements besides Co element.

[0049] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include at least one element of Ca, Cd, Cr, Fe, Mg, Mn, Mo, Na, Ni, Zn, Al, As, Cu, Pb, K, Au, Ti, In, Sn, Tl or Hg.

[0050] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Ca, and the Ca element content in the crude cobalt sulfate solution is ≥20 μg / L; in some specific embodiments of the present invention, the Ca element content in the crude cobalt sulfate solution is 20-3000 μg / L; in some examples of the present invention, the Ca element content in the crude cobalt sulfate solution is 30-1000 μg / L; non-limiting specific examples are 40 μg / L, 50 μg / L, 100 μg / L, 200 μg / L, 500 μg / L or 800 μg / L.

[0051] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Cd, and the Cd element content in the crude cobalt sulfate solution is ≥10 μg / L; in some specific embodiments of the present invention, the Cd element content in the crude cobalt sulfate solution is 10-400 μg / L; in some examples of the present invention, the Cd element content in the crude cobalt sulfate solution is 12-100 μg / L; non-limiting specific examples are 20 μg / L, 30 μg / L, 50 μg / L, 70 μg / L or 90 μg / L.

[0052] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Cr, and the Cr element content in the crude cobalt sulfate solution is ≥10 μg / L; in some specific embodiments of the present invention, the Cr element content in the crude cobalt sulfate solution is 10-530 μg / L; in some examples of the present invention, the Cr element content in the crude cobalt sulfate solution is 15-100 μg / L; non-limiting specific examples are 20 μg / L, 30 μg / L, 50 μg / L, 70 μg / L or 90 μg / L.

[0053] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Fe, and the Fe element content in the crude cobalt sulfate solution is ≥100 μg / L; in some specific embodiments of the present invention, the Fe element content in the crude cobalt sulfate solution is 100-2700 μg / L; in some examples of the present invention, the Fe element content in the crude cobalt sulfate solution is 200-1000 μg / L; non-limiting specific examples are 250 μg / L, 300 μg / L, 400 μg / L, 500 μg / L or 800 μg / L.

[0054] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Mg, and the Mg element content in the crude cobalt sulfate solution is ≥100 μg / L; in some specific embodiments of the present invention, the Mg element content in the crude cobalt sulfate solution is 100-3600 μg / L; in some examples of the present invention, the Mg element content in the crude cobalt sulfate solution is 120-1000 μg / L; non-limiting specific examples are 130 μg / L, 150 μg / L, 200 μg / L, 500 μg / L or 800 μg / L.

[0055] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Na, and the Na element content in the crude cobalt sulfate solution is ≥100 μg / L; in some specific embodiments of the present invention, the Na element content in the crude cobalt sulfate solution is 100-1600 μg / L; in some examples of the present invention, the Na element content in the crude cobalt sulfate solution is 130-1000 μg / L; non-limiting specific examples are 150 μg / L, 200 μg / L, 500 μg / L or 800 μg / L.

[0056] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Ni, and the Ni content in the crude cobalt sulfate solution is ≥100 μg / L; in some specific embodiments of the present invention, the Ni content in the crude cobalt sulfate solution is 100-3000 μg / L; in some examples of the present invention, the Ni content in the crude cobalt sulfate solution is 120-1000 μg / L; non-limiting specific examples are 140 μg / L, 150 μg / L, 200 μg / L, 500 μg / L or 800 μg / L.

[0057] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Cu, and the Cu element content in the crude cobalt sulfate solution is ≥10 μg / L; in some specific embodiments of the present invention, the Cu element content in the crude cobalt sulfate solution is 10-1000 μg / L; in some examples of the present invention, the Cu element content in the crude cobalt sulfate solution is 15-400 μg / L; non-limiting specific examples are 20 μg / L, 30 μg / L, 50 μg / L, 100 μg / L, 200 μg / L or 300 μg / L.

[0058] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include K, and the K element content in the crude cobalt sulfate solution is ≥50 μg / L; in some specific embodiments of the present invention, the K element content in the crude cobalt sulfate solution is 50-1600 μg / L; in some examples of the present invention, the K element content in the crude cobalt sulfate solution is 60-500 μg / L; non-limiting specific examples are 65 μg / L, 70 μg / L, 80 μg / L, 100 μg / L, 200 μg / L or 300 μg / L.

[0059] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Ti, and the K element content in the crude cobalt sulfate solution is ≥20 μg / L; in some specific embodiments of the present invention, the K element content in the crude cobalt sulfate solution is 20-200 μg / L; in some examples of the present invention, the K element content in the crude cobalt sulfate solution is 30-150 μg / L; non-limiting specific examples are 35 μg / L, 40 μg / L, 50 μg / L, 80 μg / L, 100 μg / L or 120 μg / L.

[0060] In some embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Sn, and the Sn element content in the crude cobalt sulfate solution is ≥5 μg / L; in some specific embodiments of the present invention, the Sn element content in the crude cobalt sulfate solution is 5-200 μg / L; in some examples of the present invention, the Sn element content in the crude cobalt sulfate solution is 10-100 μg / L; non-limiting specific examples are 15 μg / L, 20 μg / L, 30 μg / L, 50 μg / L, 70 μg / L or 90 μg / L.

[0061] In some specific embodiments of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Ca, Cd, Cr, Fe, Mg, Na, Ni, Cu, K, Sn elements, and at least one element of Mn, Mo, Zn, Al, As, Pb, Au, Ti, In, Tl or Hg; in some examples of the present invention, in step S1, the metal impurities in the crude cobalt sulfate solution include Ca, Cd, Cr, Fe, Mg, Mn, Mo, Na, Ni, Zn, Al, As, Cu, Pb, K, Au, Ti, Sn and Tl elements.

[0062] In some embodiments of the present invention, in step S1, the total content of metal impurities in the crude cobalt sulfate solution is ≥900 μg / L; in some specific embodiments of the present invention, in step S1, the total content of metal impurities in the crude cobalt sulfate solution is 900 μg / L to 25 mg / L; in some examples of the present invention, in step S1, the total content of metal impurities in the crude cobalt sulfate solution is 950 μg / L to 5 mg / L; non-limiting specific examples are 960 μg / L, 980 μg / L, 1 mg / L, 1.5 mg / L, 2 mg / L, 3 mg / L or 4 mg / L.

[0063] In some embodiments of the present invention, in step S1, the crude cobalt sulfate solution contains organic impurities. The total content of organic impurities is expressed as total organic carbon (TOC) content.

[0064] In some embodiments of the present invention, in step S1, the total organic carbon content in the crude cobalt sulfate solution is ≥10 mg / L; in some specific embodiments of the present invention, in step S1, the total organic carbon content in the crude cobalt sulfate solution is 10-30 mg / L; in some examples of the present invention, in step S1, the total organic carbon content in the crude cobalt sulfate solution is 12-20 mg / L; non-limiting specific examples are 13 mg / L, 14 mg / L, 15 mg / L, 16 mg / L, 17 mg / L, 18 mg / L or 19 mg / L.

[0065] In some embodiments of the present invention, in step S1, the crude cobalt sulfate solution includes the following components:

[0066] Co 70~90g / L Total organic carbon (TOC) ≥10 mg / L Metal impurities ≥900 μg / L

[0067] In some specific embodiments of the present invention, in step S1, the crude cobalt sulfate solution includes the following components:

[0068] Co 70~90g / L Total organic carbon (TOC) 10~30mg / L Metal impurities 900 μg / L~25 mg / L

[0069] In some examples of the present invention, in step S1, the crude cobalt sulfate solution includes the following components:

[0070] Co 70~90g / L Total organic carbon (TOC) 12-20 mg / L Metal impurities 950 μg / L~5 mg / L

[0071] In some specific examples of the present invention, in step S1, the crude cobalt sulfate solution includes the following components:

[0072]

[0073]

[0074] In some embodiments of the present invention, in step S1, the adsorbent is activated carbon.

[0075] In some embodiments of the present invention, in step S1, the activated carbon is obtained by an impurity removal method comprising the following steps: primary cleaning: the activated carbon raw material is cleaned with dilute sulfuric acid and soaked for 20 to 30 hours to obtain primary activated carbon; secondary cleaning: the primary activated carbon is cleaned with ultrapure water to obtain secondary activated carbon and a water washing liquid, and the cleaning step is performed until the conductivity of the water washing liquid is ≤10μS; tertiary cleaning: the secondary activated carbon is cleaned with a cobalt sulfate solution to obtain activated carbon after impurities are removed and a cobalt sulfate washing liquid, and the cleaning step is performed until the difference between the total content of metal impurities in the cobalt sulfate washing liquid and the total content of metal impurities in the cobalt sulfate solution is ≤30μg / L.

[0076] Since conventional activated carbon raw materials contain a large amount of impurities, especially a large amount of metal impurities, if the activated carbon raw materials are directly used for oil removal, more impurities will be introduced. The activated carbon obtained by the above impurity removal method has a low metal impurity content. When deoiling the crude cobalt sulfate solution, it can not only achieve a good oil removal effect and significantly reduce the total organic carbon content, but also ensure that no new metal impurities are introduced into the purification system, which increases the difficulty of subsequent purification.

[0077] In the above impurity removal method, dilute sulfuric acid is first used for thorough washing to soak out some acid-soluble metal impurities, then ultrapure water is used for washing to further remove impurities and wash away residual acid to avoid affecting subsequent steps, and finally cobalt sulfate solution is used for washing. Since the Co ions in the cobalt sulfate solution are relatively high in the activated carbon adsorption order, they can replace a large amount of metal impurities contained in the activated carbon raw material, so that the metal impurities are desorbed from the activated carbon, thereby achieving the effect of further purification of the activated carbon. The difference between the total content of metal impurities in the cobalt sulfate washing solution and the total content of metal impurities in the cobalt sulfate solution is ≤30 μg / L, indicating that the impurities can basically no longer be desorbed from the activated carbon. The crude cobalt sulfate solution is deoiled using the activated carbon after impurity removal, and no new metal impurities are introduced into the purification system.

[0078] In some embodiments of the present invention, in the method for removing impurities from activated carbon, the concentration of dilute sulfuric acid is 0.1 to 1 mol / L; in some embodiments of the present invention, in the method for removing impurities from activated carbon, the concentration of dilute sulfuric acid is 0.3 to 0.7 mol / L.

[0079] In some embodiments of the present invention, in the method for removing impurities from activated carbon, the cobalt sulfate solution used can be the same as the crude cobalt sulfate solution in step S1, or a cobalt sulfate solution prepared with higher purity cobalt sulfate can be used. It only needs to contain cobalt sulfate, and there is no specific requirement for its purity.

[0080] In the present invention, a deoiling step is first performed to remove organic impurities from the crude cobalt sulfate solution. This prevents the organic impurities from affecting the ion exchange step, allowing the ion exchange agent to fully exchange ions with the metal impurities in the crude cobalt sulfate solution, thereby facilitating the removal of metal impurities in subsequent steps. After the deoiling step in step S1, a deoiled cobalt sulfate solution with a low total organic carbon content is obtained.

[0081] In some embodiments of the present invention, in step S1, the pH value of the crude cobalt sulfate solution during oil removal is 2.8-4; in some specific embodiments of the present invention, in step S1, the pH value of the crude cobalt sulfate solution during oil removal is 2.9-3.8; in some examples of the present invention, in step S1, the pH value of the crude cobalt sulfate solution during oil removal is 3-3.5; non-limiting specific examples are 3.1, 3.2, 3.3 or 3.4.

[0082] In some embodiments of the present invention, in step S1, the residence time of the crude cobalt sulfate solution in the activated carbon column during oil removal is 0.5 to 2 hours; in some specific embodiments of the present invention, in step S1, the residence time of the crude cobalt sulfate solution in the activated carbon column during oil removal is 0.6 to 1.8 hours; in some examples of the present invention, in step S1, the residence time of the crude cobalt sulfate solution in the activated carbon column during oil removal is 0.7 to 1.5 hours; non-limiting specific examples are 0.8 hours, 0.9 hours, 1 hour, 1.1 hours, 1.2 hours, 1.3 hours or 1.4 hours.

[0083] In some embodiments of the present invention, in step S1, the speed at which the crude cobalt sulfate solution passes through the activated carbon column during oil removal is 10 to 100 L / h; in some specific embodiments of the present invention, in step S1, the speed at which the crude cobalt sulfate solution passes through the activated carbon column during oil removal is 20 to 80 L / h; in some examples of the present invention, in step S1, the speed at which the crude cobalt sulfate solution passes through the activated carbon column during oil removal is 30 to 70 L / h; non-limiting specific examples include 35 L / h, 40 L / h, 45 L / h, 50 L / h, 55 L / h, 60 L / h, or 65 L / h.

[0084] By controlling the pH value of the crude cobalt sulfate solution, the residence time in the activated carbon column, the flow rate and other parameters during oil removal, a good TOC removal effect is ensured, which is also conducive to achieving a good metal impurity removal effect in subsequent steps.

[0085] In some embodiments of the present invention, in step S1, the cobalt ion concentration of the cobalt sulfate degreasing solution is 70-90 g / L; in some specific embodiments of the present invention, in step S1, the cobalt ion concentration of the cobalt sulfate degreasing solution is 72-88 g / L; in some examples of the present invention, in step S1, the cobalt ion concentration of the cobalt sulfate degreasing solution is 75-85 g / L; non-limiting specific examples are 76 g / L, 78 g / L, 80 g / L, 82 g / L or 84 g / L.

[0086] In some embodiments of the present invention, in step S1, the total organic carbon content in the cobalt sulfate deoiling liquid is ≤5 mg / L; in some specific embodiments of the present invention, in step S1, the total organic carbon content in the cobalt sulfate deoiling liquid is 1-5 mg / L; in some examples of the present invention, in step S1, the total organic carbon content in the cobalt sulfate deoiling liquid is 1-2 mg / L; non-limiting specific examples include 1.1, 1.2, 1.3 mg / L, 1.4 mg / L, 1.5 mg / L, 1.6 mg / L, 1.7 mg / L, 1.8 mg / L or 1.9 mg / L.

[0087] In some embodiments of the present invention, in step S1, the total content of metal impurities in the cobalt sulfate deoiling solution is ≥850 μg / L; in some specific embodiments of the present invention, in step S1, the total content of metal impurities in the cobalt sulfate deoiling solution is 850 μg / L to 25 mg / L; in some examples of the present invention, in step S1, the total content of metal impurities in the cobalt sulfate deoiling solution is 800 μg / L to 5 mg / L; non-limiting specific examples are 850 μg / L, 900 μg / L, 1 mg / L, 1.5 mg / L, 2 mg / L, 3 mg / L or 4 mg / L.

[0088] In some embodiments of the present invention, in step S1, the cobalt sulfate degreasing solution includes the following components:

[0089]

[0090]

[0091] In some specific embodiments of the present invention, in step S1, the cobalt sulfate degreasing solution includes the following components:

[0092] Co 70~90g / L Total organic carbon (TOC) 1~5mg / L Metal impurities 850 μg / L~25 mg / L

[0093] In some examples of the present invention, in step S1, the cobalt sulfate degreasing solution includes the following components:

[0094] Co 70~90g / L Total organic carbon (TOC) 1-2 mg / L Metal impurities 800 μg / L~5 mg / L

[0095] In some specific examples of the present invention, in step S1, the cobalt sulfate degreasing solution includes the following components:

[0096]

[0097]

[0098] In some embodiments of the present invention, in step S2, the cobalt sulfate deoiling liquid passes through the ion exchanger at a rate of 50 to 100 L / h; in some embodiments of the present invention, in step S2, the cobalt sulfate deoiling liquid passes through the ion exchanger at a rate of 55 to 95 L / h; in some embodiments of the present invention, in step S2, the cobalt sulfate deoiling liquid passes through the ion exchanger at a rate of 60 to 90 L / h; non-limiting specific examples include 65 L / h, 70 L / h, 75 L / h, 80 L / h, or 85 L / h.

[0099] By controlling the speed at which the cobalt sulfate degreasing liquid passes through the ion exchanger, sufficient ion exchange reaction is ensured between the ion exchanger and the metal impurities, and the metal impurities are adsorbed onto the ion exchanger to be removed from the solution, thereby achieving a good cobalt sulfate purification effect.

[0100] In some embodiments of the present invention, in step S2, the pH value of the cobalt sulfate deoiling liquid when passing through the ion exchanger is 1.5-4; in some specific embodiments of the present invention, in step S2, the pH value of the cobalt sulfate deoiling liquid when passing through the ion exchanger is 2-3.6; in some examples of the present invention, in step S2, the pH value of the cobalt sulfate deoiling liquid when passing through the ion exchanger is 2.4-3.2; non-limiting specific examples are 2.5, 2.6, 2.7, 2.8, 2.9, 3 or 3.1.

[0101] In some embodiments of the present invention, the ion exchanger is selected from a cation exchange resin; in some specific embodiments of the present invention, the cation exchange resin is selected from D001, LSC850, D860, D851, D401, D412 or 732, etc.

[0102] Compared with anion exchange resin, the present invention uses cation exchange resin to achieve better impurity removal effect and is more conducive to removing metal impurities in the system.

[0103] In some embodiments of the present invention, the particle size of the ion exchanger is 0.1 to 2 mm; in some specific embodiments of the present invention, the particle size of the ion exchanger is 0.2 to 1.8 mm; in some examples of the present invention, the particle size of the ion exchanger is 0.3 to 1.5 mm; non-limiting specific examples include 0.315 to 1.25 mm, 0.4 mm, 0.5 mm, 0.8 mm, 1 mm or 1.2 mm.

[0104] In some embodiments of the present invention, the volumetric full exchange capacity of the ion exchanger is 1 to 20 mmol / mL; non-limiting specific examples include 5 mmol / mL, 8 mmol / mL, 10 mmol / mL, 15 mmol / mL, or 18 mmol / mL.

[0105] Ion exchangers with specific particle size and exchange capacity are beneficial for better adsorption of metal impurities in the system, achieving better purification and impurity removal effects.

[0106] Through the ion exchange step in step S2, the metal impurities in the solution can be effectively removed to obtain a cobalt sulfate purified solution with a low total content of metal impurities.

[0107] In some embodiments of the present invention, in step S2, the cobalt ion concentration of the cobalt sulfate purified solution is 70-90 g / L; in some specific embodiments of the present invention, in step S2, the cobalt ion concentration of the cobalt sulfate purified solution is 72-88 g / L; in some examples of the present invention, in step S2, the cobalt ion concentration of the cobalt sulfate purified solution is 75-85 g / L; non-limiting specific examples are 76 g / L, 78 g / L, 80 g / L, 82 g / L or 84 g / L.

[0108] In some embodiments of the present invention, in step S2, the total content of metal impurities in the cobalt sulfate purified solution is ≤600 μg / L; in some specific embodiments of the present invention, in step S2, the total content of metal impurities in the cobalt sulfate purified solution is 300-600 μg / L; in some examples of the present invention, in step S2, the total content of metal impurities in the cobalt sulfate purified solution is 400-550 μg / L; non-limiting specific examples include 450 μg / L, 480 μg / L, 500 μg / L, 520 μg / L or 540 μg / L.

[0109] In some embodiments of the present invention, in step S2, the total organic carbon content in the cobalt sulfate purified solution is ≤5 mg / L; in some specific embodiments of the present invention, in step S2, the total organic carbon content in the cobalt sulfate purified solution is 1-5 mg / L; in some examples of the present invention, in step S2, the total organic carbon content in the cobalt sulfate purified solution is 1-2 mg / L; non-limiting specific examples include 1.1, 1.2, 1.3 mg / L, 1.4 mg / L, 1.5 mg / L, 1.6 mg / L, 1.7 mg / L, 1.8 mg / L or 1.9 mg / L.

[0110] In some embodiments of the present invention, in step S2, the cobalt sulfate purification solution includes the following components:

[0111] Co 70~90g / L Total organic carbon (TOC) ≤5mg / L Metal impurities ≤600 μg / L

[0112] In some specific embodiments of the present invention, in step S2, the cobalt sulfate purification solution includes the following components:

[0113] Co 70~90g / L Total organic carbon (TOC) 1~5mg / L Metal impurities 300~600μg / L

[0114] In some examples of the present invention, in step S2, the cobalt sulfate purification solution includes the following components:

[0115] Co 70~90g / L Total organic carbon (TOC) 1-2 mg / L Metal impurities 400~550μg / L

[0116] In some specific examples of the present invention, in step S2, the cobalt sulfate purification solution includes the following components:

[0117]

[0118]

[0119] Through the recrystallization step in step S3, the metal impurities in the solution can be further removed to obtain electronic-grade cobalt sulfate crystals with a further reduced total content of metal impurities.

[0120] A second aspect of the embodiments of the present invention provides an electronic-grade cobalt sulfate crystal obtained by the purification method of the first aspect of the embodiments of the present invention.

[0121] Through the oil removal, ion exchange and recrystallization steps in the purification method of the present invention, the crystals obtained have the characteristics of low total metal impurity content and low total organic carbon content, high purity, and are electronic-grade cobalt sulfate crystals with good application performance.

[0122] A third aspect of the embodiments of the present invention provides an electronic-grade cobalt sulfate solution obtained by mixing the electronic-grade cobalt sulfate crystals of the second aspect of the embodiments of the present invention with water.

[0123] In some embodiments of the present invention, the mass ratio of electronic grade cobalt sulfate crystals to water is 1:(1-10); in some embodiments of the present invention, the mass ratio of electronic grade cobalt sulfate crystals to water is 1:(2-8); in some embodiments of the present invention, the mass ratio of electronic grade cobalt sulfate crystals to water is 1:(4-6); non-limiting specific examples include 1:4.5, 1:5 or 1:5.5.

[0124] In some embodiments of the present invention, the cobalt ion concentration of the electronic grade cobalt sulfate solution is 30 to 50 g / L; in some embodiments of the present invention, the cobalt ion concentration of the electronic grade cobalt sulfate solution is 32 to 45 g / L; in some embodiments of the present invention, the cobalt ion concentration of the electronic grade cobalt sulfate solution is 35 to 40 g / L; non-limiting specific examples are 36 g / L, 37 g / L, 38 g / L or 39 g / L.

[0125] In some embodiments of the present invention, the total metal impurity content of the electronic-grade cobalt sulfate solution is ≤200 μg / L; in some specific embodiments of the present invention, the total metal impurity content of the electronic-grade cobalt sulfate solution is 80-200 μg / L; in some examples of the present invention, the total metal impurity content of the electronic-grade cobalt sulfate solution is 100-150 μg / L; non-limiting specific examples are 110 μg / L, 120 μg / L, 130 μg / L or 140 μg / L.

[0126] Taking Fe, Mg, Na and Ni as an example, the purification method of the present invention can effectively remove metal impurities in the solution, remove a large amount of Fe, Mg, Na and Ni elements contained in the original crude cobalt sulfate solution, and obtain an electronic-grade cobalt sulfate solution with low content of Fe, Mg, Na and Ni elements.

[0127] In some embodiments of the present invention, the Fe content in the electronic-grade cobalt sulfate solution is ≤50 μg / L; in some specific embodiments of the present invention, the Fe content in the electronic-grade cobalt sulfate solution is 10-50 μg / L; in some examples of the present invention, the Fe content in the electronic-grade cobalt sulfate solution is 15-40 μg / L; non-limiting specific examples are 20 μg / L, 25 μg / L, 30 μg / L, 34 μg / L or 38 μg / L.

[0128] In some embodiments of the present invention, the Mg content in the electronic-grade cobalt sulfate solution is ≤50 μg / L; in some specific embodiments of the present invention, the Mg content in the electronic-grade cobalt sulfate solution is 10-50 μg / L; in some examples of the present invention, the Mg content in the electronic-grade cobalt sulfate solution is 15-40 μg / L; non-limiting specific examples include 20 μg / L, 25 μg / L, 30 μg / L, 34 μg / L or 38 μg / L.

[0129] In some embodiments of the present invention, the Na content in the electronic-grade cobalt sulfate solution is ≤10 μg / L; in some specific embodiments of the present invention, the Na content in the electronic-grade cobalt sulfate solution is 1-10 μg / L; in some examples of the present invention, the Na content in the electronic-grade cobalt sulfate solution is 2-8 μg / L; non-limiting specific examples are 3 μg / L, 4 μg / L, 5 μg / L, 6 μg / L or 7 μg / L.

[0130] In some embodiments of the present invention, the Ni content in the electronic-grade cobalt sulfate solution is ≤50 μg / L; in some specific embodiments of the present invention, the Ni content in the electronic-grade cobalt sulfate solution is 10-50 μg / L; in some examples of the present invention, the Ni content in the electronic-grade cobalt sulfate solution is 20-45 μg / L; non-limiting specific examples include 25 μg / L, 30 μg / L, 35 μg / L, 40 μg / L or 42 μg / L.

[0131] In some embodiments of the present invention, the total organic carbon content of the electronic-grade cobalt sulfate solution is ≤5 mg / L; in some specific embodiments of the present invention, the total organic carbon content of the electronic-grade cobalt sulfate solution is 0.5-5 mg / L; in some examples of the present invention, the total organic carbon content of the electronic-grade cobalt sulfate solution is 1-2 mg / L; non-limiting specific examples include 1.1, 1.2, 1.3 mg / L, 1.4 mg / L, 1.5 mg / L, 1.6 mg / L, 1.7 mg / L, 1.8 mg / L or 1.9 mg / L.

[0132] In some embodiments of the present invention, the electronic grade cobalt sulfate solution includes the following components:

[0133] Co 30~50g / L Total organic carbon (TOC) ≤5mg / L Metal impurities ≤200 μg / L

[0134] In some specific embodiments of the present invention, the electronic grade cobalt sulfate solution includes the following components:

[0135] Co 30~50g / L Total organic carbon (TOC) 0.5-5 mg / L Metal impurities 80~200μg / L

[0136] In some examples of the present invention, the electronic grade cobalt sulfate solution includes the following components:

[0137] Co 30~50g / L Total organic carbon (TOC) 1-2 mg / L Metal impurities 100-150 μg / L

[0138] In some specific examples of the present invention, the electronic grade cobalt sulfate solution includes the following components:

[0139] Co 30~50g / L Total organic carbon (TOC) 1-2 mg / L Ca 1-10 μg / L Cd 0.5-10 μg / L Cr 0.5-10 μg / L Fe 10-50 μg / L Mg 10-50 μg / L Mn 0.1~10μg / L Mo 0.001~10μg / L Na 1-10 μg / L Ni 10-50 μg / L Zn 0.001~10μg / L Al 0.1~10μg / L As 1-10 μg / L Cu 1-10 μg / L Pb 0.001~10μg / L K 5-10 μg / L Au 0.001~10μg / L Ti 1-10 μg / L In 0.001~10μg / L Sn 0.5-10 μg / L Tl 0.001~10μg / L Hg 0.001~10μg / L

[0140] In some embodiments of the present invention, the pH value of the electronic grade cobalt sulfate solution is 4 to 6; in some specific embodiments of the present invention, the pH value of the electronic grade cobalt sulfate solution is 4.5 to 5.5; in some embodiments of the present invention, the pH value of the electronic grade cobalt sulfate solution is 4.8 to 5.2; non-limiting specific examples include 4.85, 4.9, 4.95, 5, 5.05, 5.1 or 5.15.

[0141] Since cobalt sulfate is easily hydrolyzed at a high pH and is easily affected by other impurities, it is difficult for a general crude cobalt sulfate solution to maintain a high pH value. However, the pH value of the electronic-grade cobalt sulfate solution obtained by the purification method of the present invention can reach 4 to 6. The electronic-grade cobalt sulfate solution with a higher pH value is conducive to the expansion of its application field and the improvement of its application performance, such as in the electrodeposition of cobalt.

[0142] The use of a cobalt sulfate solution with a higher pH value is beneficial to increasing the current density and current efficiency, as well as improving the appearance quality of the deposit.

[0143] A fourth aspect of the embodiments of the present invention provides an application of the electronic-grade cobalt sulfate crystals of the second aspect of the embodiment of the present invention, or the electronic-grade cobalt sulfate solution of the third aspect of the embodiment of the present invention in the field of nanoscale chip integrated circuits.

[0144] The electronic-grade cobalt sulfate crystals and electronic-grade cobalt sulfate solution obtained by the purification method of the present invention have high purity, low total metal impurity content and low total organic carbon content, and thus have stable and good performance, and are widely used, especially in the field of nano-scale chip integrated circuits.

[0145] The content of the present invention is further described in detail below through specific examples. It should be understood that the following examples are only used to further illustrate the present invention and cannot be interpreted as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth in the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, and those skilled in the art can make selections within a suitable range through the description herein, and are not limited to the specific data exemplified below. The raw materials, reagents or devices used in the following examples and comparative examples, unless otherwise specified, can be obtained from conventional commercial sources, or can be obtained by existing known methods.

[0146] In the following examples, ND means that when the content of a substance is lower than the minimum detection limit of the detection equipment, the substance will be marked as "ND" in the test report, indicating that the content of the substance is ≤0.01 μg / L.

[0147] In the following embodiments, metal impurities include Fe, Na, Ni, Ca, Cd, Cr, Mg, Mn, Mo, Zn, Al, As, Cu, Pb, K, Au, Ti, In, Sn, Tl and Hg elements. The total metal impurity content (total metal impurities) refers to the sum of the contents of the above metal impurities. Co is not a metal impurity.

[0148] In the following examples, the water used in each step is ultrapure water, and the conductivity of the ultrapure water is less than 1 μS and the total content of metal impurities is less than 10 μg / L.

[0149] Example 1

[0150] A method for purifying electronic grade cobalt sulfate, the flow diagram is as follows Figure 1 As shown, the following steps are included:

[0151] S1. Preparation of crude solution: Prepare a crude cobalt sulfate solution with a Co concentration of 80.36 g / L by using a mass ratio of cobalt sulfate heptahydrate crystals to ultrapure water of 1:2.12.

[0152] S2. Deoiling: The crude cobalt sulfate solution is passed through an activated carbon column for adsorption deoiling to obtain a cobalt sulfate deoiled solution. In this step, the pH value of the crude cobalt sulfate solution is 3.2, the residence time of the crude cobalt sulfate solution in the activated carbon column is 1 hour, the crude cobalt sulfate solution passes through the activated carbon column at a rate of 50 L / h, and the column is passed in a bottom-in, top-out manner.

[0153] In this step, before degreasing, an activated carbon column is prepared by the following steps: washing the activated carbon raw material in a three-step process of dilute sulfuric acid (0.5 mol / L)-ultrapure water-cobalt sulfate solution, specifically, soaking in dilute sulfuric acid (0.5 mol / L) for 20 to 30 hours; washing with ultrapure water until the conductivity of the washing liquid is ≤10 μS; and washing with cobalt sulfate solution until the difference between the total content of metal impurities in the cobalt sulfate washing liquid and the total content of metal impurities in the cobalt sulfate solution is ≤30 μg / L, thereby obtaining the de-impurified activated carbon, which is then filled into a column to obtain an activated carbon column for degreasing.

[0154] S3. Ion Exchange: The cobalt sulfate deoiling liquid (pH 3.2) was passed through a cation exchange resin column at 25±5°C to purify the cobalt sulfate purified liquid. In this step, the cation exchange resin was model D001, had a resin particle size of 0.315-1.25 mm, and a volumetric full exchange capacity of 1-20 mmol / mL. The cation exchange resin column had a column volume of 100 L and an effective volume of 90 L. The cobalt sulfate deoiling liquid passed through the cation exchange resin column at a rate of 90 L / h, with a top-in, bottom-out flow rate.

[0155] S4. Recrystallization: The purified cobalt sulfate solution is evaporated and concentrated, cooled and crystallized, and the crystal yield is controlled to be 50%. The solution is filtered under reduced pressure and washed to obtain purified electronic grade cobalt sulfate crystals.

[0156] S5. Dissolution: Take electronic grade cobalt sulfate crystals and prepare an electronic grade cobalt sulfate solution with a Co concentration of 38.01 g / L at a mass ratio of cobalt sulfate crystals to ultrapure water of 1:5.02.

[0157] S6. Packaging: Put the electronic grade cobalt sulfate solution into the product packaging barrel.

[0158] The components and their contents in the solution system of each step in Example 1 were measured, and the results are shown in Table 1:

[0159] Table 1 Components and contents of the solution system in each step of Example 1

[0160]

[0161]

[0162] As can be seen from Table 1, in the purification method of Example 1 of the present invention, the crude cobalt sulfate solution contains a large amount of metallic impurities and organic impurities, with a total metallic impurity content of 964.19 μg / L, wherein the contents of Fe, Mg, Na, and Ni are all above 100 μg / L, and the TOC content reaches 15.23 mg / L. The deoiling step can effectively remove organic impurities in the solution, thereby significantly reducing the TOC content in the obtained cobalt sulfate deoiled solution. The ion exchange step can effectively remove metallic impurities in the solution, thereby significantly reducing the total metallic impurity content in the obtained cobalt sulfate purified solution. The recrystallization step can further remove metallic impurities, thereby further reducing the total metallic impurity content in the finally obtained electronic-grade cobalt sulfate crystals and the electronic-grade cobalt sulfate solution. The purity of the electronic-grade cobalt sulfate crystals in this example is 99.998%, and the pH value of the electronic-grade cobalt sulfate solution is 4.97.

[0163] In addition, the ion exchange in this example is carried out at 25±5°C. If the temperature is too high, the exchange groups in the resin may be damaged, thereby reducing the exchange capacity of the resin; if the temperature is too low, the activity of the exchange groups of the resin will be reduced, causing the exchange process to become slow and reducing the purification effect.

[0164] It should be noted that the Co concentration of the electronic-grade cobalt sulfate solution prepared in step S5 of this example is 38.01 g / L. The concentration can be adjusted according to actual needs. This example is only used as an example. If the Co concentration is increased to 80 g / L (similar to the Co concentration in the crude cobalt sulfate solution), the TOC in the obtained solution is 3.64 mg / L, and the total content of metal impurities is 269.33 μg / L. It can be seen that the method of the present invention can effectively remove TOC and metal impurities, and obtain high-purity electronic-grade cobalt sulfate crystals and electronic-grade cobalt sulfate solution.

[0165] Example 2

[0166] A method for purifying electronic-grade cobalt sulfate is disclosed. The method differs from Example 1 in that, in step S3 of this example, high-purity sulfuric acid is used to adjust the pH of the cobalt sulfate deoiling solution before ion exchange, so that the pH of the cobalt sulfate deoiling solution (column pH) varies when the solution passes through a cation exchange resin column. The specific column pH values are shown in Table 2. The other steps are the same as in Example 1.

[0167] The total content of metallic impurities in the cobalt sulfate purified solution obtained at different column pH values was detected to characterize the effect of column pH value on the impurity removal effect of the ion exchange step. The results are shown in Table 2.

[0168] Table 2 Effect of column pH value on impurity removal effect of ion exchange step

[0169]

[0170]

[0171] As can be seen from Table 2, the pH value affects the impurity removal effect of the ion exchange step. When the pH value of the cobalt sulfate deoiling liquid is between 2.8 and 3.2 when passing through the column, it has a good removal effect on the metal impurities contained therein. Through ion exchange at a specific pH value, a cobalt sulfate purified liquid with a low total metal impurity content can be obtained, which is beneficial for subsequent impurity removal and purification.

[0172] Example 3

[0173] A method for purifying electronic-grade cobalt sulfate is disclosed, which differs from Example 1 in that, in step S3 of this example, the ion exchange resin is replaced by an anion exchange resin of model D301 with a particle size of 0.710 to 1.250 mm. The other steps are the same as those in Example 1.

[0174] The total content of metallic impurities in the cobalt sulfate purified solution obtained by ion exchange in different ion exchange resins was measured to characterize the effect of the ion exchange resin on the impurity removal effect of the ion exchange step. The results are shown in Table 3.

[0175] Table 3 Effect of ion exchange resin on impurity removal effect of ion exchange step

[0176]

[0177] As can be seen from Table 3, the type of ion exchange resin has a greater impact on the impurity removal effect. Compared with cation exchange resin, cation exchange resin has a better effect on removing metal impurities from cobalt sulfate degreasing liquid.

[0178] Example 4

[0179] A method for purifying electronic-grade cobalt sulfate is disclosed. The method differs from Example 1 in that, in step S3, the speed at which the cobalt sulfate deoiling liquid passes through the cation exchange resin column (column flow rate) is changed. The specific column flow rates are shown in Table 4. The other steps are the same as in Example 1.

[0180] The total content of metallic impurities in the cobalt sulfate purified solution obtained at different column flow rates was measured to characterize the effect of column flow rate on the impurity removal effect of the ion exchange step. The results are shown in Table 4.

[0181] Table 4 Effect of column speed on impurity removal effect of ion exchange step

[0182]

[0183]

[0184] As can be seen from Table 4, the column speed affects the impurity removal effect of the ion exchange step. A column speed within the range of the embodiment of the present invention (e.g., 70 to 100 L / h) has a good impurity removal effect. If the column speed is too fast (e.g., exceeding 100 L / h), the impurity removal effect is poor. Using an appropriate column speed can produce a cobalt sulfate purified solution with a low total metal impurity content, which is beneficial for subsequent further impurity removal and purification.

[0185] Example 5

[0186] A method for purifying electronic-grade cobalt sulfate is disclosed. The method differs from Example 1 in that, in step S4 of this example, the crystal yield is changed. The specific crystal yields are shown in Table 5. The other steps are the same as those in Example 1.

[0187] The total content of metallic impurities in the electronic-grade cobalt sulfate solutions obtained at different crystal yields was detected to characterize the effect of crystal yield on the impurity removal results of the recrystallization step. The results are shown in Table 5.

[0188] Table 5 Effect of crystal yield on impurity removal results in the recrystallization step

[0189]

[0190]

[0191] As can be seen from Table 5, the crystal yield of the recrystallization process affects the impurity removal effect. Controlling the crystal yield below 60% can ensure a good metal impurity removal effect. If the crystal yield is too high, the metal impurity removal effect is poor, and the total metal impurity content in the obtained electronic-grade cobalt sulfate solution is high, which is difficult to meet application requirements. If the crystal yield is too low, the amount of electronic-grade cobalt sulfate crystals obtained is small, the production efficiency is low, and the cost is high. Controlling the appropriate crystal yield in the recrystallization process can obtain electronic-grade cobalt sulfate crystals and electronic-grade cobalt sulfate solutions with high purity and low total metal impurity content, and have high production efficiency and controllable costs, which is conducive to large-scale production.

[0192] From the above, it can be seen that the embodiment of the present invention can effectively improve the impurity removal effect of the crude cobalt sulfate product by controlling the temperature, pH value, column flow rate and resin type of the ion exchange step, as well as the crystal yield of the recrystallization step, and ultimately obtain electronic-grade cobalt sulfate crystals and electronic-grade cobalt sulfate solutions with low total metal impurity content and low total organic carbon content.

[0193] In summary, the purification method of the present invention can effectively remove impurities in the crude cobalt sulfate solution through the steps of oil removal, ion exchange and recrystallization, combined with the control of crystal yield, to obtain electronic-grade cobalt sulfate crystals and an electronic-grade cobalt sulfate solution with low total metal impurity content and low total organic carbon content. The electronic-grade cobalt sulfate solution has stable and good performance and is widely used, especially in the field of nanoscale chip integrated circuits.

Claims

1. A method for purifying electronic grade cobalt sulfate, characterized in that: The following steps are involved: S1. Deoiling: Deoiling the crude cobalt sulfate solution through an adsorbent to obtain a cobalt sulfate deoiled solution; S2. Ion exchange: purifying the cobalt sulfate deoiling liquid through an ion exchanger to obtain a purified cobalt sulfate liquid; S3, recrystallization: evaporating and concentrating the purified cobalt sulfate solution, cooling and crystallizing, and controlling the crystal yield to be 20-50% to obtain electronic grade cobalt sulfate crystals; In step S1, the cobalt ion concentration of the crude cobalt sulfate solution is 70-90 g / L; In step S2, the cobalt sulfate degreasing liquid passes through the ion exchanger at a rate of 70 to 90 L / h; the pH value of the cobalt sulfate degreasing liquid when passing through the ion exchanger is 2.8 to 3.2; the ion exchanger is selected from a cation exchange resin; In step S1, the crude cobalt sulfate solution contains metal impurities and organic impurities; the metal impurities include other metal elements except Co; the total content of metal impurities in the crude cobalt sulfate solution is ≥300 μg / L; the total organic carbon content in the crude cobalt sulfate solution is ≥10 mg / L; the metal impurities in the crude cobalt sulfate solution include Ni, and the Ni content in the crude cobalt sulfate solution is 100 to 3000 μg / L; In step S1, the adsorbent is activated carbon; the activated carbon is obtained by an impurity removal method comprising the following steps: primary cleaning: using dilute sulfuric acid to clean the activated carbon raw material and soaking it for 20 to 30 hours to obtain primary activated carbon; secondary cleaning: using ultrapure water to clean the primary activated carbon to obtain secondary activated carbon and a water wash solution, and cleaning in this step until the conductivity of the water wash solution is ≤10μS; tertiary cleaning: using a cobalt sulfate solution to clean the secondary activated carbon to obtain activated carbon after impurities are removed and a cobalt sulfate wash solution, and cleaning in this step until the difference between the total content of metal impurities in the cobalt sulfate wash solution and the total content of metal impurities in the cobalt sulfate solution is ≤30μg / L.

2. The purification method according to claim 1, wherein In step S1, the metal impurities in the crude cobalt sulfate solution further include at least one element selected from the group consisting of Ca, Cd, Cr, Fe, Mg, Mn, Mo, Na, Zn, Al, As, Cu, Pb, K, Au, Ti, In, Sn, Tl, and Hg.

3. The purification method according to claim 1, wherein In step S2, the particle size of the ion exchanger is 0.1 to 2 mm; And / or, the volumetric total exchange capacity of the ion exchanger is 1 to 20 mmol / mL.

4. The purification method according to any one of claims 1 to 3, characterized in that mixing the electronic-grade cobalt sulfate crystals with water to obtain an electronic-grade cobalt sulfate solution; The cobalt ion concentration of the electronic-grade cobalt sulfate solution is 30-50 g / L; the total metal impurity content of the electronic-grade cobalt sulfate solution is ≤200 μg / L; the total organic carbon content of the electronic-grade cobalt sulfate solution is ≤5 mg / L; and the pH value of the electronic-grade cobalt sulfate solution is 4-6.

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