Method for preparing high-purity cobalt through electrodeposition

Abstract

The invention relates to the technical field of hydrometallurgy preparation of high-purity cobalt, in particular to a method for preparing high-purity cobalt through electrodeposition. The method comprises the steps that a 50-200 g / L cobalt solution is prepared, the concentration of impurity iron ions is lower than 0.001 g / L, the pH value is adjusted to be 3-4.5 with alkali, oxygen is introduced, ferrous iron is oxidized and hydrolyzed, filtering is conducted through a precision filter, then the pH value of the solution is adjusted to be 1-2 with acid, impurity removal is conducted through ion exchange resin, then the pH value is adjusted to be 2-5 with alkali, electrodeposition is conducted, and the iron content in the prepared high-purity cobalt is 1t; and 0.01 ppm of the catalyst. The method is simple in process, short in flow and environmentally friendly, and the content of trace iron in the cobalt solution can be effectively controlled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrometallurgical preparation of high-purity cobalt, and particularly relates to a method for preparing high-purity cobalt by electrodeposition. BACKGROUND

[0002] High-purity cobalt as a key material for semiconductors is mainly used for the preparation of high-end sputtering targets of integrated circuits, for PVD film coating including contact, via, interconnection, barrier layer, packaging, etc. As the process size of integrated circuits is continuously reduced, the requirements for inclusions and defects in metal thin films are also becoming more and more stringent, so the chemical purity of high-purity cobalt as a raw material for target preparation is also extremely high. Since cobalt and iron are similar in nature, they are co-deposited during electrolysis, and it is difficult to separate cobalt from iron by electrochemical process, so the two must be effectively separated before electrolytic preparation of high-purity cobalt.

[0003] Currently, the methods for removing iron from cobalt solution mainly include neutralization method, goethite method, iron oxide method, and iron sulfide method, etc. These methods are mainly for low-purity high-purity cobalt, and ion exchange method can be used for removing iron impurities from high-purity cobalt above 4N. It is found through practice that the purification depth of iron in cobalt solution should be less than 0.00001 g / L to ensure that the iron content in the prepared high-purity cobalt is less than 1 ppm. Since there is a limit to the adsorption of impurities by ion exchange method, and the selection and adaptability are high, when the iron content in the solution is less than 0.0001 g / L, the removal of this part of trace iron becomes particularly difficult and critical. In the prior art, there are related technologies that can achieve trace iron removal, for example, Chinese patent CN106636638B uses chelating resin Monophos to remove impurity iron in cobalt solution by dynamic ion exchange method, and 99.999% high-purity cobalt with an iron content less than 1 ppm can be obtained, but the adsorption capacity of the resin is extremely high, and when the purification capacity of the resin is insufficient, the unremoved divalent iron will be oxidized to trivalent iron during electrodeposition, the electrode potential of trivalent iron is more positive than that of divalent cobalt, so trivalent iron will be preferentially deposited on the cathode instead of cobalt, causing the iron content in cobalt to exceed the standard, seriously affecting the chemical purity and stability of the product.

[0004] In addition to ion exchange method, for the removal of trace iron in high-purity cobalt, Chinese patent CN103966627A discloses a method for deep removal of iron in cobalt electrolysis or electrodeposition solution with an iron concentration less than 500 mg / L, phosphates or phosphoric acid are added to the cobalt salt solution to form stable complexes with impurity iron, and then the method of electrodeposition cobalt is used to obtain high-purity cobalt with an iron impurity content less than 0.5 ppm, but this method introduces sodium and phosphate impurities, and the phosphorus-containing wastewater needs to be treated, increasing the production cost; patent CN102162031B uses trichloroisocyanuric acid with oxidizing property as an iron removal agent to oxidize Fe 2+ to Fe 3+ , while Co2+ The added ammonium oxalate generates cobalt oxalate precipitate, thereby achieving the effect of iron removal. However, cobalt oxalate cannot be directly used for electrodeposition to prepare high-purity cobalt and requires further treatment, which increases the process flow. In addition, trichloroisocyanuric acid and ammonium oxalate will produce ammonia nitrogen wastewater.

[0005] Therefore, it is necessary to develop a method with a simple process flow, high trace iron removal efficiency, and the ability to produce high-purity cobalt above 5N. Summary of the Invention

[0006] In order to solve the deficiencies in the prior art, the present invention proposes a method for preparing high-purity cobalt by electrowinning, the specific method being as follows:

[0007] A method for preparing high-purity cobalt by electrowinning comprises the following steps:

[0008] Step 1: Prepare a cobalt solution with a concentration of 50-200 g / L, wherein the concentration of impurity iron ions is less than 0.001 g / L, and adjust the pH value of the cobalt solution to 3-4.5 with alkali;

[0009] Step 2: adding an oxidant to oxidize the divalent iron in the cobalt solution obtained in step 1 into trivalent iron and hydrolyze it, and filtering to remove the ferric hydroxide precipitate to obtain a deironed solution.

[0010] Step 3: Add acid to the iron removal solution to adjust the pH to 1-2;

[0011] Step 4: exchanging the solution obtained in step 3 through a chelating resin in an ion exchange column, and controlling the temperature of the solution to be 10° C.-60° C.;

[0012] Step 5: Add alkali to the above impurity-removed liquid to adjust its pH value to 2-5;

[0013] Step 6: Electrodeposit the solution obtained in step 5 to obtain high-purity cobalt with an iron content of less than 1 ppm.

[0014] Furthermore, the cobalt solution prepared in step 1 is a CoCl2 solution.

[0015] Furthermore, the alkali in step 1 and / or step 5 is high-grade pure ammonia water.

[0016] Furthermore, the acid in step 3 is high-grade pure hydrochloric acid.

[0017] Furthermore, the oxidant in step 2 is oxygen, and the flow rate of oxygen is 5-20 L / min.

[0018] Furthermore, the chelating resin in step 4 is chelating resin HP686.

[0019] Further, the flow rate of the solution in step 4 through the ion exchange column is 2-5 BV / h.

[0020] Further, the electrodeposition process parameters in step 6 are as follows: the solution pH value is 2-5, the electrodeposition temperature is 40-80℃, the current density is 50-300 A / m 2 , and the cell voltage is 2.5-12 V.

[0021] The method of the present application is simple in process, short in flow, environmentally friendly, and can effectively control the trace iron in the cobalt solution. The method not only can stably control the iron impurity content in high-purity cobalt, but also increases the capacity of the resin to adsorb impurities by removing iron before ion exchange adsorption, and further improves the removal of other key impurities. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0023] A method for preparing high-purity cobalt by electrodeposition, comprising the following steps:

[0024] Step 1: preparing a CoCl2 solution with a concentration of 50-200 g / L, wherein the concentration of impurity iron ions is less than 0.001 g / L, and adjusting the pH value of the cobalt solution to 3-4.5 by using high-purity ammonia water, which is beneficial to the hydrolysis of trivalent iron, trivalent chromium and trivalent aluminum without affecting the main metal ions;

[0025] Step 2: introducing oxygen at a flow rate of 5-20 L / min to oxidize the divalent iron in the cobalt solution obtained in step 1 to trivalent iron and hydrolyze it, and removing the iron hydroxide precipitate by filtration to obtain an iron-removed solution;

[0026] Step 3: adding high-purity hydrochloric acid to the iron-removed solution to adjust the pH value to 1-2 to achieve the optimal purification pH range for the resin to adsorb impurities such as divalent copper and divalent nickel;

[0027] Step 4: passing the solution obtained in step 3 through a chelating resin column with high selectivity, large adsorption capacity and good stability for impurities, and controlling the temperature of the solution to be 10-60℃, because too low temperature is not conducive to the adsorption of impurities by the resin, and too high temperature will damage the structure of the resin. The flow rate is 2-5 BV / h, at which the adsorption capacity of the resin for impurities is the strongest, and an impurity-removed solution is obtained;

[0028] Step 5: adding high-purity ammonia water to the above-mentioned impurity-removed solution to adjust the pH value to 2-5;

[0029] Step 6: The solution obtained in step 5 is subjected to electro-deposition to obtain high-purity cobalt with iron content less than 0.00001 g / L and chemical purity of the high-purity cobalt being more than 99.999%. The pH value of the solution during the electro-deposition is 2-5, the electro-deposition temperature is 40-80°C, the current density is 50-300 A / m 2 , and the cell voltage is 2.5-12 V.

[0030] Example 1

[0031] (1) A cobalt chloride solution with a concentration of 60 g / L is prepared using cobalt chloride crystals, and the pH value of the solution is adjusted to 4.5 using high-purity ammonia water;

[0032] (2) Oxygen is introduced at a flow rate of 5 L / min to fully oxidize the divalent iron in the solution to trivalent iron and to hydrolyze it, and the iron hydroxide precipitate generated by the hydrolysis precipitate is removed through a 0.1 micron precision filter;

[0033] (3) The solution in step 2 is adjusted to a pH value of 1-2 using high-purity hydrochloric acid;

[0034] (4) The solution is exchanged through an HP686 resin in an ion exchange column at a flow rate of 5 BV / h, and the temperature of the solution is controlled to be 55°C;

[0035] (5) The pH value is adjusted to 4.5 using high-purity ammonia water;

[0036] (6) Electro-deposition is performed, the pH value of the solution during the electro-deposition is 3-4, the electro-deposition temperature is 40°C, the current density is 200 A / m 2 , and the cell voltage is 8 V.

[0037] The content of iron impurities in the cobalt solution before being treated by the method of this example is 0.000012 g / L, and the content of iron impurities in the cobalt solution after being treated by the method of this example is detected to be less than 0.00001 g / L, and the content of iron impurities in the electro-deposited cobalt actually obtained is less than 0.1 ppm.

[0038] Example 2

[0039] (1) A cobalt chloride solution with a concentration of 95 g / L is prepared using cobalt chloride crystals, and the pH value of the solution is adjusted to 4.0 using high-purity ammonia water;

[0040] (2) Oxygen is introduced at a flow rate of 8 L / min to fully oxidize the divalent iron in the solution to trivalent iron and to hydrolyze it, and the iron hydroxide precipitate generated by the hydrolysis precipitate is removed through a 0.1 micron precision filter;

[0041] (3) The solution in step 2 is adjusted to a pH value of 1-2 using high-purity hydrochloric acid;

[0042] (4) The solution is exchanged through an HP686 resin in an ion exchange column at a flow rate of 4 BV / h, and the temperature of the solution is controlled to be 45°C;

[0043] (5) adjust the pH to 4.0 with high-purity ammonia water;

[0044] (6) carry out electrodeposition, the pH of the solution is 4-5 during electrodeposition, the electrodeposition temperature is 60°C, the current density is 50 A / m 2 , and the cell voltage is 3 V.

[0045] The content of iron impurities in the cobalt solution before treatment by the method of the example is 0.000016 g / L, and the content of iron impurities in the cobalt solution after treatment by the method of the example is less than 0.00001 g / L, and the content of iron impurities in the electrodeposited cobalt actually obtained is less than 0.1 ppm.

[0046] Example 3

[0047] (1) prepare a cobalt chloride solution with a concentration of 130 g / L using cobalt chloride crystals, and adjust the pH of the solution to 3.5 with high-purity ammonia water;

[0048] (2) pass oxygen at a flow rate of 12 L / min to fully oxidize the divalent iron in the solution to trivalent iron and hydrolyze it; remove the iron hydroxide precipitate generated by hydrolysis through a 0.1-micron precision filter;

[0049] (3) adjust the pH of the solution in step 2 to 1-2 with high-purity hydrochloric acid;

[0050] (4) exchange through HP686 resin in an ion exchange column at a flow rate of 3 BV / h, and control the temperature of the solution to be 40°C;

[0051] (5) adjust the pH to 3.5 with high-purity ammonia water;

[0052] (6) carry out electrodeposition, the pH of the solution is 4-5 during electrodeposition, the electrodeposition temperature is 80°C, the current density is 300 A / m 2 , and the cell voltage is 12 V.

[0053] The content of iron impurities in the cobalt solution before treatment by the method of the example is 0.000018 g / L, and the content of iron impurities in the cobalt solution after treatment by the method of the example is less than 0.00001 g / L, and the content of iron impurities in the electrodeposited cobalt actually obtained is less than 0.1 ppm.

[0054] Example 4

[0055] (1) prepare a cobalt chloride solution with a concentration of 165 g / L using cobalt chloride crystals, and adjust the pH of the solution to 4.0 with high-purity ammonia water;

[0056] (2) oxygen is bubbled into the solution at a rate of 15 L / min to fully oxidize the divalent iron to trivalent iron and to hydrolyze it; the iron hydroxide precipitate produced by the hydrolysis is removed by a 0.1 micron precision filter;

[0057] (3) the solution from step 2 is adjusted to a pH of 1-2 using high-purity hydrochloric acid;

[0058] (4) the solution is exchanged through HP686 resin in an ion exchange column at a flow rate of 2 BV / h, and the temperature of the solution is controlled at 30°C;

[0059] (5) the pH is adjusted to 3.0 using high-purity ammonia water;

[0060] (6) electrodeposition is performed, the pH of the solution during electrodeposition is 3-4, the electrodeposition temperature is 50°C, the current density is 150 A / m 2 , and the cell voltage is 5.5 V.

[0061] The content of the iron impurities in the cobalt solution before being treated by the method of this example is 0.000034 g / L, the content of the iron impurities in the cobalt solution after being treated by the method of this example is less than 0.00001 g / L as detected, and the content of the iron impurities in the electrodeposited cobalt actually obtained is less than 0.1 ppm.

[0062] Example 5

[0063] (1) a cobalt chloride solution with a concentration of 190 g / L is prepared using cobalt chloride crystals, and the pH of the solution is adjusted to 4.0 using high-purity ammonia water;

[0064] (2) oxygen is bubbled into the solution at a rate of 20 L / min to fully oxidize the divalent iron to trivalent iron and to hydrolyze it; the iron hydroxide precipitate produced by the hydrolysis is removed by a 0.1 micron precision filter;

[0065] (3) the solution from step 2 is adjusted to a pH of 1-2 using high-purity hydrochloric acid;

[0066] (4) the solution is exchanged through HP686 resin in an ion exchange column at a flow rate of 2 BV / h, and the temperature of the solution is controlled at 20°C;

[0067] (5) the pH is adjusted to 2.5 using high-purity ammonia water;

[0068] (6) electrodeposition is performed, the pH of the solution during electrodeposition is 2-3, the electrodeposition temperature is 45°C, the current density is 100 A / m 2 , and the cell voltage is 4.5 V.

[0069] The content of the iron impurities in the cobalt solution before being treated by the method of this example is 0.000050 g / L, the content of the iron impurities in the cobalt solution after being treated by the method of this example is less than 0.00001 g / L as detected, and the content of the iron impurities in the electrodeposited cobalt actually obtained is less than 0.1 ppm.

[0070] Table 1 GDMS total elemental analysis of high purity cobalt produced in Example 1

[0071]

[0072]

[0073] Some exemplary embodiments of the present application are described above, it is understood that the above-described embodiments are merely used to explain the present application, and do not constitute a limitation to the protection scope of the present application. The features in these embodiments can be recombined in a suitable manner, and the schemes thus obtained are still within the protection scope required by the present application. Based on the above-described embodiments, all other embodiments obtained by those skilled in the art without making creative efforts, i.e. all modifications, equivalent replacements and improvements, etc. made within the spirit and principles of the present application, are also within the protection scope required by the present application.

Claims

1. A method for preparing high-purity cobalt by electrowinning, characterized in that: The following steps are involved: Step 1: Prepare a cobalt solution with a concentration of 50-200 g / L, wherein the concentration of impurity iron ions is less than 0.001 g / L, and adjust the pH value of the cobalt solution to 3-4.5 with alkali; Step 2: adding an oxidizing agent to oxidize the divalent iron in the cobalt solution obtained in step 1 to trivalent iron and hydrolyze it, and filtering to remove the ferric hydroxide precipitate to obtain a deionized solution; Step 3: Add acid to the iron removal solution to adjust the pH to 1-2; Step 4: exchanging the solution obtained in step 3 through a chelating resin in an ion exchange column, controlling the temperature of the solution to be 10° C.-60° C., to obtain a decontaminated solution; Step 5: adding alkali to the above impurity-removed liquid to adjust its pH value to 2-5; Step 6: Electrodeposit the solution obtained in step 5 to obtain high-purity cobalt with an iron content of <0.1 ppm.

2. The method for preparing high-purity cobalt by electrowinning according to claim 1, characterized in that: The cobalt solution prepared in step 1 is a CoCl2 solution.

3. The method for preparing high-purity cobalt by electrowinning according to claim 1, characterized in that: The base in step 1 and / or step 5 is aqueous ammonia.

4. The method for preparing high-purity cobalt by electrowinning according to claim 1, characterized in that: The acid in step 3 is hydrochloric acid.

5. The method for preparing high-purity cobalt by electrowinning according to claim 1, characterized in that: The oxidant in step 2 is oxygen, and the flow rate of oxygen is 5-20 L / min.

6. The method for preparing high-purity cobalt by electrowinning according to claim 1, characterized in that: The chelating resin in step 4 is chelating resin HP686.

7. The method for preparing high-purity cobalt by electrowinning according to claim 1, characterized in that: The flow rate of the solution in step 4 through the ion exchange column is 2BV-5BV / h.

8. The method for preparing high-purity cobalt by electrowinning according to claim 1, characterized in that: The electrolytic process parameters in step 6 are: solution pH 2-5, electrolytic temperature 40-80°C, current density 50-300A / m 2 , the cell voltage is 2.5-12V.

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