Oxidation cobalt precipitation method

Abstract

The invention relates to a method for oxidizing and precipitating cobalt, and belongs to the field of recovery of valuable metals in smelting slag. According to the method, the manganese oxide and the oxidizing agent are added into the cobalt-containing solution, the cobalt precipitation reaction is carried out, a neutralizer does not need to be added to adjust the pH value of ore pulp in the reaction process, the high precipitation rate of cobalt can be achieved, and the pH value at the reaction endpoint can be stabilized between 2.0 and 3.0. According to the method, the cobalt content of the filtrate after cobalt precipitation is smaller than 20 mg / L, the cobalt precipitation rate is larger than 98%, the high precipitation rate of cobalt is achieved, the amount of zinc precipitated along with cobalt in the cobalt precipitation process is reduced, the zinc loss is reduced, and the cobalt concentrate grade is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of valuable metal recovery from smelting slag, and in particular relates to precipitation and enrichment of cobalt in zinc purification slag. Background Art

[0002] The zinc sulfate solution obtained by zinc hydrometallurgy is purified and impurized. The current mainstream process is to use a three-stage reverse antimony purification process, that is, the first stage removes copper and cadmium, the second stage removes cobalt and nickel, and the third stage removes residual cadmium. The filter residue produced by the second stage of cobalt and nickel removal is leached with zinc by weak acid to produce cobalt-containing slag, whose composition is: Co 0.3-1.5%, Zn 15-30%, Cd 5-20%. For the cobalt-containing slag, dilute sulfuric acid is usually used to leach Zn, Cd and Co therein, and the leaching solution is oxidized and precipitated with potassium permanganate or sodium persulfate to produce cobalt concentrate. The cobalt-removed filtrate after cobalt precipitation is returned to the zinc smelting process to recover zinc and cadmium.

[0003] Existing studies have shown that the pH value of the system needs to be controlled above 4 when cobalt is precipitated, otherwise cobalt cannot be precipitated. For example, the document "Thermodynamic Analysis of Cobalt Precipitation by Potassium Permanganate Oxidation in Sulfuric Acid Leaching Solution of Zinc Slag for Cobalt Removal in Hydrometallurgy" (Ou Jun, Lan Dejun, Journal of Guilin Institute of Technology, Vol. 26, No. 2, April 2006) points out that the influence of the pH value of the system on the precipitation of cobalt by permanganate oxidation is crucial: the reaction will not occur if the pH value is too low, and there is a threshold of pH = 4, that is, the pH cannot be lower than 4 when cobalt is precipitated, otherwise the cobalt precipitation reaction will be difficult to proceed. The document "Experimental Study on Improvement of Cobalt Recovery Process of Nickel-Cobalt Slag" (Zhang Hongju et al., China Nonferrous Metallurgy, October 2020, No. 5) also points out that the pH value needs to be controlled at 4.0-4.5 when oxidizing cobalt. In the technical solution disclosed in patent CN101838736A, it is also clearly recorded that the pH value needs to be maintained between 4-4.5 during the oxidation precipitation reaction of cobalt.

[0004] Since acid is released during cobalt oxidation precipitation, a neutralizer must be added to keep the pH value at 4.0-4.5 during cobalt precipitation. Zinc oxide or sodium hydroxide is generally used as a neutralizer. Adding a neutralizer will not only increase production costs, but also increase the pH value, which will lead to incomplete reaction of the added zinc oxide, resulting in a high zinc content in the cobalt concentrate; when sodium hydroxide is added, it will be partially over-alkaline, causing zinc hydrolysis and precipitation in the solution, which will also cause a high zinc content in the cobalt concentrate, increase the loss of zinc metal with the cobalt concentrate, and not only affect the grade of the cobalt concentrate but also cause zinc loss. Summary of the invention

[0005] In order to overcome the shortcomings of the background technology, the present invention provides a technical solution for oxidative cobalt precipitation. The present invention does not add a neutralizing agent, and does not need to neutralize the pH value to 4.0-4.5, thereby reducing production costs, reducing the loss of zinc metal with cobalt concentrate, and obtaining a higher cobalt precipitation rate, and the grade of the cobalt concentrate is also improved.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions: The method for oxidizing and precipitating cobalt comprises the following steps: (1) adding manganese oxide and an oxidant to a cobalt-containing solution to precipitate cobalt into slag; (2) The cobalt precipitate slurry is subjected to liquid-solid separation to obtain cobalt concentrate and filtrate.

[0007] Furthermore, the manganese oxide is manganese dioxide.

[0008] Furthermore, the amount of manganese oxide added is 1.0-3.0 g / L calculated as pure manganese dioxide.

[0009] Furthermore, the amount of the oxidant added is 1.05-1.2 times the theoretical amount of cobalt oxidation reaction (the amount of divalent cobalt that is just completely oxidized to trivalent cobalt).

[0010] Furthermore, the oxidant is potassium permanganate or sodium persulfate.

[0011] Furthermore, the end point pH of the cobalt precipitation reaction is 2.0-3.0.

[0012] Further, the manganese oxide is derived from zinc electrolysis anode mud or manganese powder.

[0013] Furthermore, the proportion of manganese oxide with a particle size of ≤0.074 mm is ≥85%.

[0014] Furthermore, the cobalt precipitation temperature in step (1) is 75-85°C, and the reaction time is 3.0-4.0h.

[0015] Furthermore, the cobalt-containing solution is a dilute sulfuric acid leaching solution of cobalt-containing slag. Beneficial Effects

[0016] The invention adds manganese oxide and an oxidant to the dilute sulfuric acid leaching solution of cobalt-containing slag, and can achieve a high cobalt precipitation rate without adding a neutralizer. The cobalt precipitation rate is greater than 98%, and the cobalt content of the filtrate after precipitation is less than 20 mg / L, thereby achieving a high cobalt precipitation rate. At the same time, since it is not necessary to add a neutralizer, the pH value of the cobalt precipitation endpoint is between 2.0 and 3.0, thereby reducing the amount of zinc precipitated with cobalt during the cobalt precipitation process, reducing zinc loss, and improving the grade of cobalt concentrate.

[0017] The cobalt precipitation process of the present invention does not require the addition of a neutralizing agent, and cobalt can be efficiently precipitated when the pH value of the cobalt precipitation slurry is 2.0-3.0, thereby providing a new technical solution for oxidative cobalt precipitation.

[0018] In the cobalt precipitation process of the present invention, manganese oxide is added to make the acid released during the cobalt precipitation reaction enter the slag as basic sulfate, so that the pH value of the cobalt precipitation process is stabilized at 2.0-3.0. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and beneficial effects of the present invention clearer, the technical scheme of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0020] The method for oxidizing and precipitating cobalt comprises the following steps: (1) Cobalt precipitation reaction Manganese oxide and oxidant are added to the cobalt-containing solution, the cobalt-containing solution is heated and maintained at 75-85°C for 3.0-4.0 hours to precipitate cobalt into the slag. No neutralizer is added during the reaction, and the pH value at the reaction end point is 2.0-3.0.

[0021] Cobalt-containing solution Co800-3000mg / L, pH4.5-5.0.

[0022] The manganese oxide is manganese dioxide, and the amount of manganese oxide added is 1.0-3.0 g / L based on pure manganese dioxide. The manganese dioxide comes from zinc electrolysis anode mud or manganese powder, and the proportion of particle size ≤0.074 mm is ≥85%.

[0023] The amount of the oxidant added is 1.05-1.2 times the theoretical amount of the cobalt oxidation reaction. The oxidant is potassium permanganate or sodium persulfate.

[0024] Manganese oxide and oxidant can be added simultaneously or sequentially, after reaching the reaction temperature or before heating, and then the temperature is raised to the reaction temperature. No matter which method of addition is used, the cobalt precipitation effect will not be affected.

[0025] The mechanism by which the addition of manganese oxide promotes cobalt precipitation is not fully understood. It may be that manganese oxide adsorbs and precipitates cobalt and also causes Co 3+ / Co 2+ The potential decreases, thereby promoting the oxidant to convert Co 2+ Oxidized to Co 3+ After extensive research, the inventors found that there are two related conditions for manganese oxide to promote cobalt precipitation: one is that the oxidant must be added in excess, and the other is that the cobalt to be precipitated must be Co 3 + ,Co 2+It will not be adsorbed and precipitated. These two conditions are indispensable. If only the oxidant is excessive but no manganese oxide is added, even if the reaction temperature is raised to above 85°C and the reaction time is extended to more than 4.0h, the precipitation rate of cobalt is only about 30%, that is, the cobalt precipitation is incomplete. If the cobalt precipitation needs to be complete (i.e., the cobalt precipitation filtrate Co≤20mg / L), a neutralizer needs to be added to adjust the pH value of the slurry and maintain it at 4.0-4.5, so that the cobalt can be completely precipitated; if only manganese oxide is added but no oxidant is added, even if the manganese oxide is added several times or even dozens of times, the cobalt will not precipitate, that is, Co 2+ It cannot be adsorbed and precipitated by manganese oxides.

[0026] The inventors also found that Co 2+ Oxidized to Co by oxidant 3+ , and then when it precipitates into the slag, the amount of acid released is less than the theoretical amount. The mechanism is not completely clear, but it is speculated that during the cobalt precipitation process, part of the released acid precipitates into the slag in the form of basic sulfate, so that the actual amount of acid released is less than the theoretical amount of acid released. In further research, the inventor unexpectedly found that the addition of manganese oxide can promote the formation of basic sulfate, thereby maintaining the pH value of the cobalt precipitate slurry at 2.0-3.0.

[0027] (2) Solid-liquid separation The cobalt precipitated slurry is subjected to liquid-solid classification to obtain cobalt concentrate and filtrate. The filtrate contains Co≤20mg / L. The filtrate after cobalt precipitation is returned to the zinc smelting process to recover zinc.

[0028] In order to more clearly illustrate the present invention, it is described in detail through the following examples. Example 1

[0029] Take 1000mL of cobalt-containing solution with Co850mg / L and pH4.5, add zinc electrolysis anode mud and potassium permanganate, the amount of zinc electrolysis anode mud added is 1.0g / L calculated as pure manganese dioxide, and the particle size is ≤0.074mm, the ratio is 86%, and the amount of potassium permanganate added is 1.05 times the theoretical amount of cobalt oxidation reaction; the reaction time is 3.0h, the reaction temperature is 75℃, no neutralizer is added during the reaction, and the reaction end point pH is 3.0.

[0030] After the solid-liquid separation of the cobalt ore slurry, the Co content of the filtrate was measured to be 11 mg / L, and the cobalt precipitation efficiency was 98.70%; the obtained cobalt concentrate contained Co14.36% and Zn2.75% (unless otherwise specified in the present invention, the percentages mentioned refer to the percentages by mass). Example 2

[0031] Take 1000mL of cobalt-containing solution with Co2860mg / L and pH5.0, add manganese powder and sodium persulfate, the amount of manganese powder added is 3.0g / L based on pure manganese dioxide, the particle size is ≤0.074mm, the ratio is 92%, the amount of sodium persulfate added is 1.2 times the theoretical amount of cobalt oxidation reaction, the reaction time is 4.0h, the reaction temperature is 85℃, no neutralizer is added during the reaction, and the reaction end point pH is 2.0.

[0032] After solid-liquid separation of the cobalt ore slurry, the filtrate Co was 18 mg / L and the cobalt precipitation efficiency was 99.37%; the obtained cobalt concentrate Co2 was 6.06% and Zn was 1.92%.

[0033] Comparative Example 1 1000 mL of the cobalt-containing solution having the same components as those in Example 1 was taken, and only zinc electrolysis anode mud was added without adding potassium permanganate. The zinc electrolysis anode mud used and the amount added were the same as those in Example 1. The reaction time was 3.0 h, the reaction temperature was 75° C., no neutralizer was added during the reaction, and the reaction end point pH was 4.5.

[0034] After solid separation of the cobalt ore slurry, the filtrate Co is 846 mg / L, and the cobalt concentrate Co is less than 0.01%, and Zn is 3.82%.

[0035] To further study the effect of not adding an oxidant on cobalt precipitation, the amount of zinc electrolysis anode mud added was increased to 10 times that of Example 1, that is, the amount added was 10 g / L; the reaction time was 3.0 h, the reaction temperature was 75 ° C, no neutralizer was added during the reaction, and the reaction end pH was 4.8. After the solid-liquid separation of the cobalt ore slurry, the filtrate Co was 847 mg / L, the cobalt concentrate Co <0.01%, and Zn 4.51%.

[0036] Comparative Example 1 shows that if no oxidant is added to the Co 2+ Oxidized Co 3+ , cobalt will not precipitate into the slag, indicating that manganese oxide cannot adsorb Co 2+ precipitation.

[0037] Comparative Example 2 Take 1000 mL of the cobalt-containing solution with the same components as in Example 2, add 1.2 times the theoretical amount of sodium persulfate for the cobalt oxidation reaction, do not add manganese oxide, react for 4.0 h, and at a temperature of 85° C. No neutralizer is added during the reaction, and the reaction end point pH is 2.0.

[0038] After solid separation of cobalt ore slurry, the filtrate Co was 1965 mg / L, and the cobalt precipitation efficiency was 31.23%; the cobalt concentrate Co was 6.92%, and Zn was 1.88%.

[0039] Comparative Example 2 shows that without adding a neutralizing agent and without adding manganese oxide, the efficiency of oxidative cobalt precipitation is low, and the cobalt concentrate contains low cobalt, which cannot achieve the purpose of deep cobalt removal and improving the grade of cobalt concentrate. The inventor tried to extend the reaction time to 5.0h and increase the reaction temperature to 90°C. After the solid separation of the cobalt ore slurry, the filtrate Co1962mg / L, the cobalt precipitation efficiency 31.25%; the cobalt concentrate Co6.90%, Zn1.82%, the cobalt precipitation efficiency still did not improve.

[0040] Comparative Example 3 Take 1000 mL of the cobalt-containing solution with the same components as in Example 2, add manganese powder and sodium persulfate, the amount of manganese powder added is 3.0 g / L as pure manganese dioxide, the proportion of manganese powder particle size ≤ 0.074 mm is 92%, the amount of sodium persulfate added is 1.0 times the theoretical amount of cobalt oxidation reaction, the reaction time is 4.0 h, the reaction temperature is 85 ° C, no neutralizer is added during the reaction, and the reaction end point pH is 2.0.

[0041] After solid separation of the cobalt ore slurry, the filtrate Co3 is 80 mg / L, and the cobalt precipitation efficiency is 86.67%; the cobalt concentrate Co2 is 2.55%, and Zn is 1.73%.

[0042] Comparative Example 3 shows that when manganese oxide is added but the oxidant is not added in excess, the cobalt precipitation reaction is incomplete and the cobalt precipitation filtrate contains more than 20 mg / L of Co.

[0043] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for oxidative precipitation of cobalt, characterized in that: The following steps are involved: (1) adding manganese oxide and an oxidant to a cobalt-containing solution to precipitate cobalt into slag; (2) The cobalt precipitate slurry is subjected to liquid-solid separation to obtain cobalt concentrate and filtrate.

2. The method according to claim 1, characterized in that The manganese oxide is manganese dioxide.

3. The method according to claim 1, characterized in that The amount of manganese oxide added is 1.0-3.0 g / L based on pure manganese dioxide.

4. The method according to claim 1, characterized in that: The amount of oxidant added is 1.05-1.2 times the theoretical amount of cobalt oxidation reaction.

5. The method according to claim 4, characterized in that The oxidizing agent is potassium permanganate or sodium persulfate.

6. The method according to any one of claims 1 to 5, characterized in that: The end point pH value of the cobalt precipitation reaction is 2.0-3.

0.

7. The method according to any one of claims 1 to 3, characterized in that: Manganese oxides come from zinc electrolysis anode mud or manganese powder.

8. The method according to claim 7, characterized in that The proportion of manganese oxide with a particle size of ≤0.074mm is ≥85%.

9. The method according to claim 1, characterized in that: The cobalt precipitation temperature in step (1) is 75-85°C, and the reaction time is 3.0-4.0h.

10. The method according to claim 1, characterized in that The cobalt-containing solution is a dilute sulfuric acid leaching solution of cobalt-containing slag.