A method for recovering cobalt from waste residues in the production of cobalt acetate by hydrogen peroxide method

Abstract

The application discloses a method for recovering cobalt from waste residues in the production of cobalt acetate by a hydrogen peroxide method, and adopts sodium thiocyanate and acetic acid to treat cobalt waste residues to obtain [Co(NCS)4] 2‑ solution, an oxide and unreacted metal cobalt; the obtained unreacted metal cobalt can be directly put into a synthesis kettle to participate in the production of cobalt acetate after being leached by sodium thiocyanate to remove surface impurities; the obtained oxide is reacted with sulfuric acid and hydrogen peroxide to obtain a cobalt sulfate solution; the obtained cobalt sulfate solution and the obtained [Co(NCS)4] 2‑ solution are reacted with sodium carbonate to obtain cobalt carbonate precipitation; the obtained cobalt carbonate precipitation is reacted with an acetic acid solution to obtain a cobalt acetate solution. The application does not produce toxic thiocyanic acid gas, and the sodium thiocyanate can be reused in the recovery process, so that the generation of waste liquid can be reduced, the cobalt recovery rate is high, and economic benefits are good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cobalt acetate production, and particularly relates to a method for recovering cobalt from waste residues in the production of cobalt acetate by the hydrogen peroxide method. BACKGROUND

[0002] Cobalt acetate is an important organic chemical raw material, which is mainly used as a liquid phase oxidation catalyst, such as the preparation of purified terephthalic acid. The preparation process of cobalt acetate generally includes the acetic acid method, the oxygen or air method, the hydrogen peroxide method, the electrolysis method, the waste residue recovery method and the like. Among them, the cobalt raw material source used in the hydrogen peroxide method is more extensive, and the production cost of the method is low, and there is no pollution, which is convenient for industrial production.

[0003] In the production process of cobalt acetate by the hydrogen peroxide method, hydrogen peroxide is added to the reaction system of dilute acetic acid and metal cobalt in a dropwise manner as an oxidizing agent, and after reacting with metal cobalt to generate an intermediate product-cobalt hydroxide, it reacts with acetic acid to generate cobalt acetate solution. In the synthesis process of cobalt acetate, the dropwise adding speed of hydrogen peroxide needs to be controlled to prevent the system from over-temperature due to the occurrence of violent reaction, and the reaction solution needs to maintain a certain acidity. If the dropwise adding speed of hydrogen peroxide is too fast, the local temperature of the reaction solution is relatively high and the acidity is relatively low, and the intermediate product-cobalt hydroxide will be oxidized by hydrogen peroxide to form high cobalt hydroxide, and part of the high cobalt hydroxide will be dehydrated to form trivalent cobalt oxide. For simplicity, the trivalent cobalt oxide and hydroxide are collectively referred to as oxide in the following description. Since the existing hydrogen peroxide method for preparing cobalt acetate adopts a dynamic hydrogen peroxide oxidation method, in order to promote the full contact of the solid and liquid phases, the oxide is discharged from the bottom of the reaction kettle to the top of the reaction kettle by circulating equipment, and is sprayed onto the surface of the metal cobalt in the kettle. The metal cobalt in the bottom of the reaction kettle is greatly excessive, and is in contact with the reaction solution for a long time, which causes the black oxide adsorbing cobalt acetate to embed the unreacted metal cobalt to form waste residues. The price of metal cobalt is expensive, and the cobalt in the waste residues is wasted because it cannot be converted into cobalt acetate, which causes great economic loss and resource waste, and therefore it is of great significance to recover and reuse the cobalt in the waste residues for the field.

[0004] The existing cobalt residue recovery technology mainly adopts high-temperature leaching with sulfuric acid, such as the methods disclosed in Chinese patents CN 104726717, CN 101838736 and CN 106222430. The existing patent methods can recover cobalt from waste residues, but a large amount of sulfuric acid and energy is consumed, and the generated waste acid liquid needs to be treated, which is not friendly to the environment. SUMMARY

[0005] In order to solve the technical problems in the existing cobalt residue recovery technology that a large amount of sulfuric acid and energy is consumed, and the generated waste acid liquid needs to be treated, which is not friendly to the environment, the present application provides a method for recovering cobalt from waste residues in the production of cobalt acetate by the hydrogen peroxide method.

[0006] The technical scheme adopted by the present application is:

[0007] A method for recovering cobalt from production waste residue of cobalt acetate produced by hydrogen peroxide method, comprising the following steps:

[0008] (1) adding production waste residue and glacial acetic acid into sodium thiocyanate aqueous solution according to a certain mass ratio, stirring at room temperature for a period of time, and then grading filtering after standing to obtain [Co(NCS)4] 2- solution, cobalt oxide and unreacted metallic cobalt;

[0009] (2) washing the metallic cobalt obtained in step (1) with pure water, and then directly putting it into a synthesis kettle for cobalt acetate production;

[0010] (3) adding the cobalt oxide obtained in step (1) into sulfuric acid solution, heating and stirring for a period of time, slowly adding hydrogen peroxide for reduction reaction for a period of time, and then filtering after standing to obtain cobalt sulfate solution;

[0011] (4) adding sodium carbonate precipitant with the same molar amount of sulfuric acid in step (3) into the cobalt sulfate solution obtained in step (3), stirring at room temperature for a period of time, and then filtering after standing to obtain cobalt carbonate precipitate;

[0012] (5) analyzing the acidity and cobalt content of the [Co(NCS)4] 2- solution obtained in step (1), adding calculated amount of sodium carbonate precipitant, heating and stirring for a period of time, and then filtering after standing to obtain cobalt carbonate precipitate and filtrate;

[0013] (6) washing the cobalt carbonate precipitates obtained in steps (4) and (5) with pure water to remove impurity ions, and then reacting with acetic acid solution to obtain cobalt acetate solution.

[0014] Further, it further comprises: (7) adding production waste residue and glacial acetic acid with a certain mass ratio into the filtrate obtained in step (5), and repeating steps (1)-(6).

[0015] Further, the mass ratio of production waste residue, glacial acetic acid, filtrate (calculated based on sodium thiocyanate) is 1:0.5-2.0:1.5-4.5.

[0016] Further, the content of water-soluble cobalt in the waste residue is different, and in step (1), the mass ratio of production waste residue, glacial acetic acid, sodium thiocyanate is 1:0.5-2.0:1.5-4.5.

[0017] Further, the stability of [Co(NCS)4] 2- is improved, and in step (1), the concentration of sodium thiocyanate aqueous solution is 15-40%.

[0018] Further, the coordination reaction of cobalt ions is fully carried out, and the stirring time at room temperature in step (1) is 1-2 hours.

[0019] Further, the cobalt reduction reaction is fully carried out and energy consumption is reduced, and the temperature of heating and stirring in step (3) is 50-60℃, the time is 0.5-1 hour, and the reduction reaction time is 3-4 hours.

[0020] Further, the amount of reagents used in the cobalt reduction reaction is reduced as much as possible, and in step (3), the initial concentration of sulfuric acid solution is 2.0-6.0 mol / L, the concentration of hydrogen peroxide is 27.5-50.0%, and the mass ratio of cobalt oxide, sulfuric acid (98% by mass), and hydrogen peroxide (H2O2) is 1:1.0-1.5:0.3-0.5.

[0021] Further, the water-soluble cobalt is maximally converted into cobalt carbonate precipitate, and in step (4), the stirring time at room temperature is 1-2 hours; and in step (5), the temperature of heating and stirring is 85-95℃, and the time is 2-3 hours.

[0022] Further, the volume of waste liquid is reduced and the concentration of sodium thiocyanate in the filtrate is increased, and the sodium carbonate in steps (4) and (5) is solid sodium carbonate.

[0023] The beneficial effects of the present application are:

[0024] (1) The present application uses sodium thiocyanate and acetic acid to treat cobalt waste residue, and according to the principle of strong acid producing weak acid, this process does not produce toxic thiocyanic acid gas, and sodium thiocyanate can be reused in the recovery process, which can reduce the generation of waste liquid.

[0025] (2) The present application uses sodium thiocyanate and acetic acid to treat cobalt waste residue, and after fractional filtration, the unreacted block-shaped cobalt metal is washed with sodium thiocyanate to remove surface impurities, and can be directly put into a synthesis kettle to participate in the production of cobalt acetate; the obtained [Co(NCS)4] 2- solution and powdered cobalt oxide can be converted into cobalt acetate solution, and the recovery process is simple and easy to operate.

[0026] (3) The present application only uses sulfuric acid in the oxide digestion step, which can greatly reduce the generation of waste acid.

[0027] (4) The process and operation of the present application are simple, the raw materials used are low in price, the recovery rate is high, and the economic benefit is high. DETAILED DESCRIPTION

[0028] The present application will be further described below with specific examples to facilitate the understanding of the present application, but the present application is not limited thereto.

[0029] The production waste used in the following examples is cobalt metal waste from the reactor of our company's acetate plant, and the other raw materials are commercially available.

[0030] Example 1

[0031] (1) 20.14g of cobalt metal waste and 20.00g of glacial acetic acid were added to 240g of 25% sodium thiocyanate aqueous solution, stirred at room temperature for 2 hours, allowed to stand, and then filtered in stages to obtain 294.56g of [Co(NCS)4] 2- Solution, 1.52g oxide powder and 12.56g cobalt metal block.

[0032] (2) After being washed with pure water, metallic cobalt can be directly added into the synthesis reactor for cobalt acetate production; the oxide content is very low and insufficient for oxide digestion experiments, so the oxides obtained from multiple experiments can be combined.

[0033] (3) Sampling analysis [Co(NCS)4] 2- The solution had an acidity of 4.13% and a cobalt content of 1.22%. After sampling, the remaining 291.62g of solution required 17.03g of sodium carbonate precipitant. After adding 17.03g of solid sodium carbonate, the solution was heated to 85℃ and stirred for 2 hours. After standing, the solution was filtered to obtain 6.25g of cobalt carbonate precipitate and 346.38g of filtrate.

[0034] A 2.011g sample of the filtrate was tested and found to contain 0.24% cobalt, which translates to 23.2% [Co(NCS)4]. 2- The cobalt that remains in the filtrate will precipitate during the next recycling process.

[0035] (4) The 6.25g cobalt carbonate precipitate obtained is washed with pure water to remove impurity ions, and then reacted with 61g of 10.5% acetic acid solution to obtain a cobalt acetate solution with a cobalt content of 4.13%.

[0036] Calculations show that the cobalt recovery rate in Example 1 is 91.58%.

[0037] Example 2

[0038] (1) 24.89 g of cobalt metal waste and 28.56 g of glacial acetic acid were added to the remaining 344.37 g of filtrate from Example 1. The sodium thiocyanate concentration of the filtrate was 17.32%. The mixture was stirred at room temperature for 2 hours, allowed to stand, and then filtered in stages to obtain 412.67 g of [Co(NCS)4]. 2- Solution, 1.62g oxide powder and 15.67g cobalt metal block.

[0039] (2) The metal cobalt is washed by pure water and then directly put into a synthesis kettle for producing cobalt acetate.

[0040] (3) The [Co(NCS)4]2solution is sampled and analyzed. 2- The acidity of the solution is 3.64%, and the cobalt content is 1.08%. The mass of the required sodium carbonate precipitant in the remaining 409.73 g of the solution after sampling is 21.12 g. After adding the solid sodium carbonate, the solution is heated to 85°C and stirred for 2 hours. After standing, filtration is performed, and 7.84 g of cobalt carbonate precipitate and 488.54 g of filtrate are obtained.

[0041] The cobalt content of 2.137 g of the filtrate is measured to be 0.22%, i.e., 23.7% of the [Co(NCS)4]2solution remains in the filtrate. This part of cobalt will form a precipitate in the next recovery process. 2-

[0042] (4) The obtained 7.84 g of cobalt carbonate precipitate is washed with pure water to remove impurity ions, and then reacts with 77 g of a 10.5% acetic acid solution to obtain a cobalt acetate solution with a cobalt content of 4.11%.

[0043] It is calculated that the cobalt recovery rate of Example 2 is 92.24%.

[0044] Example 3

[0045] (1) 320 g of metal cobalt waste residue and 318 g of glacial acetic acid are added to 3800 g of a 25% sodium thiocyanate aqueous solution, stirred at room temperature for 2 hours, and then subjected to fractional filtration after standing. 4680 g of a [Co(NCS)4]2solution, 24.02 g of an oxide powder, and 191.35 g of a metal cobalt block are obtained. 2-

[0046] (2) The metal cobalt is washed by pure water and then directly put into a synthesis kettle for producing cobalt acetate.

[0047] (3) 24.02 g of the oxide powder is added to 61.80 g of a sulfuric acid solution with a concentration of 5.91 mol / L, heated to 55°C and stirred for 1 hour, and then 26.40 g of 35% hydrogen peroxide is slowly added dropwise and reacted for 4 hours. After standing, filtration is performed, and 112.22 g of a cobalt sulfate solution is obtained.

[0048] 30.53 g of solid sodium carbonate is added to the cobalt sulfate solution, stirred at room temperature for a period of 1 hour, and then subjected to filtration after standing. 33.42 g of cobalt carbonate precipitate is obtained.

[0049] (4) The [Co(NCS)4]2solution is sampled and analyzed. 2- ​​The solution has an acidity of 4.14% and a cobalt content of 1.22%. The mass of the required sodium carbonate precipitant is 271.80g for the remaining 4677g of the solution after sampling. After adding 271.80g of solid sodium carbonate, the solution is heated to 85°C and stirred for 2 hours. After standing, the solution is filtered to obtain 99.45g of cobalt carbonate precipitate and 5219g of filtrate.

[0050] The cobalt content of 2.211g of the filtrate is measured to be 0.24%, i.e. 22.0% of the [Co(NCS)4]2- ion in the filtrate is precipitated. 2- The cobalt in the filtrate will form a precipitate in the next recovery process.

[0051] (5) The total cobalt carbonate precipitate obtained is 132.87g. After washing with pure water to remove impurity ions, the cobalt carbonate precipitate is reacted with 1297g of a 10.5% acetic acid solution to obtain a cobalt acetate solution with a cobalt content of 4.13%.

[0052] It is calculated that the cobalt recovery rate of Example 3 is 95.30%.

[0053] The above only describes preferred embodiments of the present application. It should be noted that those of ordinary skill in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements are within the scope of the present application.

Claims

1. A method for recovering cobalt from a production waste residue of cobalt acetate produced by a hydrogen peroxide method, characterized by, The method comprises the following steps: (1) The production of waste slag and glacial acetic acid according to a certain mass ratio is added to the aqueous solution of sodium thiocyanate, stirred at room temperature for a period of time, and then filtered after standing to obtain [Co(NCS)4] 2- solution, cobalt oxide and unreacted metal cobalt; (2) washing the cobalt metal obtained in step (1) with pure water, and directly putting it into a synthesis kettle for producing cobalt acetate; (3) adding the cobalt oxide obtained in step (1) into a sulfuric acid solution, heating and stirring for a period of time, slowly adding hydrogen peroxide for reduction reaction for a period of time, and then filtering after standing to obtain a cobalt sulfate solution; (4) adding sodium carbonate precipitant with the same molar amount of sulfuric acid in step (3) into the cobalt sulfate solution obtained in step (3), stirring at room temperature for a period of time, and then filtering after standing to obtain a cobalt carbonate precipitate; (5) The [Co(NCS)4] obtained in step (1) is analyzed. 2- The acidity and cobalt content of the solution are measured, a calculated amount of sodium carbonate precipitant is added, and the mixture is heated and stirred for a period of time. After standing, the mixture is filtered to obtain a cobalt carbonate precipitate and a filtrate. (6) reacting the cobalt carbonate precipitates obtained in steps (4) and (5) with acetic acid solution after washing with pure water to remove impurity ions, to obtain a cobalt acetate solution.

2. The method of claim 1, wherein the method is characterized by, The method further comprises: (7) adding production waste residue and glacial acetic acid in a certain mass ratio into the filtrate obtained in step (5), and repeating steps (1)-(6).

3. A method of recovering cobalt from spent sludge produced in the production of cobalt acetate from hydrogen peroxide method according to claim 2, characterized in that, The mass ratio of the production waste residue, glacial acetic acid and sodium thiocyanate in the filtrate is 0.5-2.0:1.5-4.

5.

4. The method of claim 1, wherein the method is characterized by, In step (1), the mass ratio of the production waste residue, glacial acetic acid and sodium thiocyanate is 1:0.5-2.0:1.5-4.

5.

5. The method of claim 1, wherein the method is characterized by: In step (1), the concentration of the aqueous sodium thiocyanate solution is 15-40%.

6. A method of recovering cobalt from spent sludge produced in the production of cobalt acetate from hydrogen peroxide method according to claim 1, characterized in that, In step (1), the stirring time at room temperature is 1-2 hours.

7. A method of recovering cobalt from spent sludge produced in the production of cobalt acetate from hydrogen peroxide method according to claim 1, characterized in that, In step (3), the heating and stirring temperature is 50-60℃, the time is 0.5-1 hour, and the reduction reaction time is 3-4 hours.

8. A method of recovering cobalt from spent sludge produced in the production of cobalt acetate from hydrogen peroxide method according to claim 1, characterized in that, In step (3), the initial concentration of the sulfuric acid solution is 2.0-6.0 mol / L, the concentration of hydrogen peroxide is 27.5-50.0%, and the mass ratio of cobalt oxide, 98% sulfuric acid and hydrogen peroxide H2O2 is 1:1.0-1.5:0.3-0.

5.

9. A method of recovering cobalt from spent sludge produced in the production of cobalt acetate from hydrogen peroxide method according to claim 1, characterized in that, In step (4), the stirring time at room temperature is 1-2 hours; in step (5), the heating and stirring temperature is 85-95℃, and the time is 2-3 hours.

10. A method of recovering cobalt from spent sludge produced in the production of cobalt acetate from hydrogen peroxide method according to claim 1, characterized in that, The sodium carbonate in steps (4) and (5) is solid sodium carbonate.