Method for extracting cobalt in laterite-nickel ore acid leaching residues through ammonia leaching-citric acid reduction

Abstract

The invention discloses a method for extracting cobalt in laterite-nickel ore acid leaching residues through ammonia leaching-citric acid reduction, which comprises the following steps: carrying out multi-stage countercurrent leaching on the laterite-nickel ore acid leaching residues by adopting ammonia water-ammonium sulfate as a leaching system to obtain a laterite-nickel ore acid leaching residue ammonia leaching solution; the nickel laterite ore acid leaching residue ammonia leaching solution, citric acid and air are subjected to an oxidation-reduction reaction, and a cobalt-containing product is obtained; and adding strong base into the cobalt-containing product, and carrying out precipitation reaction in an oxidizing atmosphere to obtain cobalt hydroxide precipitate. According to the method, a multi-stage countercurrent ammonia leaching-citric acid reduction mode is adopted, phase transformation and selective recovery of cobalt in the laterite-nickel ore acid leaching residues are achieved, and the problems that in the prior art, recovery of heavy metal in the laterite-nickel ore acid leaching residues is high in cost, large in difficulty, low in recovery rate and the like are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a method for extracting cobalt from acid leaching residue of laterite nickel ore by ammonia leaching-citric acid reduction. Background Art

[0002] Cobalt plays an important strategic role in the development of modern industry and science and technology. Its high stability under extreme conditions makes it widely used in military industry and catalyst fields. Cobalt also plays a key role in renewable energy technology, especially in the development of hydrogen energy and fuel cell technology. With the global transition to clean energy, the demand for cobalt is expected to increase further. With the growth of global demand for clean energy and high-performance materials, the strategic importance of cobalt will become more prominent. Ensuring the security of the cobalt supply chain and the sustainability of resource utilization is becoming an important task for governments and enterprises. This means that laterite nickel acid leaching residue with large production and high cobalt content has become an important raw material for extracting cobalt. With the commissioning of a large number of laterite nickel hydroprocessing projects, the discharge of laterite nickel acid leaching residue is increasing. Laterite nickel acid leaching residue still contains a large amount of valuable elements such as nickel, iron, chromium, magnesium, aluminum, and rare earths, which is a valuable secondary mineral resource. Due to the limited technical approaches for the comprehensive utilization of laterite nickel acid leaching residue (the current disposal methods are mainly stacking, deep sea landfill or underground filter press backfill), the utilization rate of cobalt in the residue is extremely low. Therefore, it is urgent to develop a green, efficient and sustainable method for extracting cobalt from laterite nickel ore acid leaching residue. Summary of the invention

[0003] In view of the technical problems of low cobalt extraction rate and poor selectivity in the current extraction of metallic cobalt from laterite nickel ore acid leaching residue, the present invention provides a method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction, aiming to efficiently recycle the cobalt metal resources in the laterite nickel ore acid leaching residue and apply it as a material. The method uses multi-stage countercurrent ammonia leaching to selectively convert cobalt into a stable cobalt ammonia complex, and then uses citric acid and alkali to directionally convert it into cobalt hydroxide precipitate, which has a high cobalt extraction rate and selectivity.

[0004] In order to achieve the above technical purpose, the present invention provides a method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction. The method comprises the following steps: subjecting the laterite nickel ore acid leaching residue to multi-stage countercurrent leaching using ammonia water-ammonium sulfate as a leaching system to obtain an ammonia leachate of the laterite nickel ore acid leaching residue; subjecting the ammonia leachate of the laterite nickel ore acid leaching residue to an oxidation-reduction reaction with citric acid and air to obtain a cobalt-containing product; and adding a strong base to the cobalt-containing product to carry out a precipitation reaction in an oxidizing atmosphere to obtain a cobalt hydroxide precipitate.

[0005] The key to the technical solution of the present invention is to coordinate multi-stage countercurrent ammonia leaching with citric acid reduction to convert the cobalt in the acid leaching residue of laterite nickel ore into cobalt hydroxide precipitate, thereby greatly improving the cobalt extraction rate and selectivity. Specifically, the present invention first uses ammonia water and ammonium salt system as leaching agents to ensure the stability of the solution pH during the leaching process; during the leaching process, the lone pair of electrons on the nitrogen atom in the ligand [NH3] can be used to occupy the empty orbital of the outer valence layer of the cobalt nucleus, thereby forming a stable coordination bond, so that the cobalt is coordinated with the ammonia ion ([Co(NH3) i 2+ ]) enters the solution in the form of acid leaching residue, while the complexes of other metal ions in the laterite nickel ore acid leaching residue in the ammonia solution have poor stability or the compounds they form under ammonia conditions are insoluble in water, thereby achieving selective leaching of cobalt; secondly, the ammonia leaching of the present invention adopts multi-stage countercurrent ammonia leaching. In this process, the solvent first enters the last stage leaching tank to meet the ore, and then transfers upward step by step to leach the target element; while the ore moves downward in the opposite direction to gradually complete the leaching. A clarification link is provided between each stage to achieve effective separation and recycling of the acid leaching residue and the leachate. Through multi-stage countercurrent ammonia leaching, the stable concentration gradient and the solid-liquid two phases in motion can be used to make the boundary layer of the two phase interface thinner or the boundary layer update faster, thereby increasing the leaching speed; and the acid leaching residue and the leachate can be continuously and fully contacted and extracted in the extractor in a dynamic state of countercurrent flow, thereby improving the leaching rate. In addition, compared with the existing inorganic reducing agents, the present invention can not only avoid excessively violent reactions and affect the operation process by using citric acid to reduce the cobalt-containing product, but also can use the strong chelating ability of citric acid to quickly combine with the cobalt ions in the cobalt ammonia complex to achieve the selective conversion of cobalt ions into cobalt elemental substances. In this process, the introduction of air in the present invention helps to improve the contact efficiency between the acid leaching solution and the leached material, thereby improving the leaching effect, and at the same time can ensure that the leached material fully reacts and reduce the loss of elements. Finally, in OH - , ammonium sulfate and oxygen to convert the cobalt element into cobalt hydroxide precipitate. The reaction equation involved in the present invention is as follows:

[0006]

[0007] 4Co(NH3)2SO4+2C6H8O7+7O2=4Co+4(NH4)2SO4+4H2O+12CO2

[0008] 2Co+4NaOH+2(NH4)2SO4+O2=2Co(OH)2↓+2Na2SO4+4NH3+2H2O

[0009] As a preferred solution, the multi-stage countercurrent leaching includes N-stage countercurrent leaching, and the process of the multi-stage countercurrent leaching is as follows: the first-stage countercurrent leaching uses the leachate obtained by the second-stage countercurrent leaching as a leaching agent to leach the laterite nickel ore acid leaching residue, and the obtained leaching residue enters the second-stage countercurrent leaching, and the second-stage countercurrent leaching uses the leachate obtained by the third-stage countercurrent leaching as a leaching agent to leach the leaching residue obtained by the first-stage countercurrent leaching, and so on, the N-stage countercurrent leaching uses the initial leaching agent to leach the leaching residue obtained by the N-1-stage countercurrent leaching. The present invention can more effectively utilize the concentration gradient of the solid and liquid phases and improve the leaching efficiency through the dynamic continuous and sufficient contact of the countercurrent flows.

[0010] As a preferred solution, the initial leaching agent is a mixed solution of ammonia water and ammonium sulfate, and the total concentration of ammonia water and ammonium sulfate is 100-500 g / L.

[0011] As a preferred solution, the molar ratio of ammonia water to ammonium sulfate is (1-3): 1. An appropriate molar ratio of ammonia to ammonium sulfate helps to maintain the stability of the pH value of the leaching system, promotes the formation of ammine complexes by Co, and improves the leaching rate. Further preferably, the molar ratio of ammonia water to ammonium sulfate is 1:1, under which the leaching rate of cobalt can reach more than 98%.

[0012] As a preferred solution, the multi-stage countercurrent leaching includes 2 to 6 stages of countercurrent leaching, and the liquid-solid ratio during the countercurrent leaching process at each stage is (4 to 8): 1, the leaching temperature is 25 to 80 ° C, the leaching time is 1 to 6 hours, and the pH control is 9.5 to 10.5. With the increase of the number of stages, the leaching efficiency gradually increases, but after reaching a certain number of stages, the effect of further increasing the number of stages will tend to be stable, and a reasonable number of stages can improve the leaching efficiency, save resources, improve the washing quality, and reduce labor intensity. However, the increase in the number of stages may also lead to an increase in cost, so it is necessary to optimize according to specific process requirements and economic benefits in practical applications. In the present invention, the range of the number of stages is controlled within 2 to 6, and more preferably 4 to 6 levels. In addition, the stability difference between cobalt ammonia complex and other metal complexes can be utilized within the pH range selected by the present invention to achieve the selective separation of cobalt, and the further preferred pH is 10.

[0013] As a preferred solution, the conditions of the redox reaction are: temperature of 25-60°C, time of 2-8h, and air with a flow rate of 50-500ml / min is introduced during the reaction to enhance the reaction. The increase in air flow rate can increase the longitudinal diffusion rate of the leaching agent solution, which helps the leached material to flow out quickly, weakens the reverse adsorption of ions, and improves the leaching efficiency; but if the air flow rate is too fast, it will make it difficult for the leaching agent to fully contact with the acid leaching residue particles, which is not conducive to the ion exchange reaction, thereby reducing the leaching rate and leaching rate of cobalt.

[0014] As a preferred solution, the amount of citric acid added is 1-10% of the mass of the laterite nickel ore acid leaching residue. The amount of citric acid added in the present invention has a direct impact on the efficiency of converting the cobalt ammonia complex into cobalt element. As a reducing agent, the increase in the concentration of citric acid can accelerate the reaction rate. However, citric acid is an organic acid, and excessive addition of citric acid will lead to changes in the acidity of the solution. Therefore, the addition of citric acid should not be excessive. It is further preferred that the amount of citric acid added is 3-5% of the mass of the laterite nickel ore acid leaching residue.

[0015] As a preferred solution, the molar ratio of the strong base to the cobalt-containing product is (1-4):1, wherein the cobalt-containing product is calculated as cobalt and the concentration of the strong base is 50-300 g / L; the strong base is one of sodium hydroxide and potassium hydroxide.

[0016] As a preferred solution, the conditions of the precipitation reaction are: temperature of 25-60°C, time of 2-8h, and air flow rate of 10-100ml / min to provide an oxidizing atmosphere. Since cobalt is a moderately active metal, it usually does not directly react with sodium hydroxide to form a precipitate. However, the cobalt-containing product of the present invention contains ammonium sulfate and the introduction of air can promote the directional conversion of cobalt into cobalt hydroxide precipitate.

[0017] As a preferred solution, the laterite nickel ore acid leaching residue includes nickel, cobalt, iron, aluminum, manganese, magnesium, zinc, calcium, copper and silicon.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention uses ammonia water-ammonium sulfate as a leaching system to perform multi-stage countercurrent leaching on laterite nickel ore acid leaching residue, selectively converts cobalt into a stable cobalt ammonia complex, and then uses citric acid and alkali to directionally convert it into cobalt hydroxide precipitate, thereby achieving phase transformation and selective recovery of cobalt in laterite nickel ore acid leaching residue, solving the current problems of high cost, great difficulty and low recovery rate of heavy metal cobalt recovery in laterite nickel ore acid leaching residue.

[0020] (2) Compared with the existing reducing agents, the present invention uses citric acid as a reducing agent to reduce the cobalt-containing product, which can not only avoid excessive reaction and affect the operation process, but also can use the strong chelating ability of citric acid to quickly combine with the cobalt ions in the cobalt ammonia complex to achieve the selective conversion of cobalt ions into cobalt element. In addition, in this process, the present invention can promote the reaction by introducing a certain amount of air to achieve rapid reduction.

[0021] (3) The process of the present invention is short and simple to operate, the direct recovery rate of cobalt can reach 98%, and the purity of the cobalt hydroxide product can reach 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1The present invention is a process flow chart of extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific implementation methods, but the protection scope of the present invention is not limited to the contents described. The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] A method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction, the specific steps are as follows:

[0026] (1) 2500 g of laterite nickel ore acid leaching residue (the components are shown in Table 1) was dried, ground, and sieved. Ammonia water-ammonium sulfate was used as the leaching system (the molar ratio of ammonia water to ammonium sulfate was 1:1), and the laterite nickel ore acid leaching residue was subjected to four-stage countercurrent leaching, wherein cobalt ions combined with ammonium ions to form a stable cobalt ammonia complex, which entered the solution in the form of ammonia complex ions to obtain a laterite nickel ore acid leaching residue ammonia leaching solution, wherein the total concentration of ammonia water-ammonium sulfate was 200 g / L, the liquid-solid ratio was 4:1, the leaching temperature was 50°C, the leaching time was 3 h, and the pH was 10; the leaching rate of cobalt in the leaching solution was 98.99%.

[0027] (2) adding organic citric acid to the ammonia leaching solution in step (1), and intensifying the reaction with air at a certain temperature, the cobalt ammonium complex is reduced by citric acid, the amount of citric acid added is 3% of the mass of the laterite nickel ore acid leaching residue, the air flow rate is 100 ml / min, the reduction temperature is 40° C., the reduction time is 4 hours, and a cobalt-containing product is obtained; the cobalt-containing product contains ammonium sulfate.

[0028] (3) adding sodium hydroxide solution to the reduction product in step (2), and simultaneously introducing air at a flow rate of 40 ml / min, wherein the cobalt is converted into cobalt hydroxide precipitate in the presence of ammonium sulfate, the solution is vacuum filtered, and the precipitate is rinsed with deionized water to prepare a cobalt hydroxide product, wherein the concentration of the sodium hydroxide solution is 100 g / L, the molar ratio of the sodium hydroxide solution to cobalt is 2:1, the temperature is 40° C., and the time is 4 h.

[0029] Table 1 Content of each component in the acid leaching residue of laterite nickel ore

[0030]

[0031] In this embodiment, the direct yield of Co is 98.7%, and the purity of the cobalt hydroxide product is 96.4%.

[0032] Example 2

[0033] A method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction, the specific steps are as follows:

[0034] (1) 3000 g of laterite nickel ore acid leaching residue (the components are shown in Table 2) was dried, ground, and sieved. Ammonia water-ammonium sulfate was used as the leaching system, and the molar ratio of ammonia water to ammonium sulfate was 1.5:1. The laterite nickel ore acid leaching residue was subjected to three-stage countercurrent leaching, wherein cobalt ions combined with ammonium ions to form a stable cobalt ammonia complex, which entered the solution in the form of ammonia complex ions to obtain an ammonia leaching solution of laterite nickel ore acid leaching residue. The total concentration of ammonia water-ammonium sulfate was 300 g / L, the liquid-solid ratio was 5:1, the leaching temperature was 55°C, the leaching time was 2 h; the pH was 10.5, and the leaching rate of cobalt in the leaching solution was 98.77%.

[0035] (2) adding organic citric acid to the ammonia leachate in step (1), and intensifying the reaction with air at a certain temperature, wherein the cobalt ammonium complex is reduced by citric acid, the amount of citric acid added is 5% of the mass of the laterite nickel ore acid leaching residue, the air flow rate is 150 ml / min, the reduction temperature is 45° C., and the reduction time is 3 h to obtain a cobalt-containing product; the cobalt-containing product contains ammonium sulfate.

[0036] (3) adding sodium hydroxide solution to the reduction product in step (2), and simultaneously introducing air at a flow rate of 40 ml / min, wherein the cobalt is converted into cobalt hydroxide precipitate in the presence of ammonium sulfate, the solution is vacuum filtered, and the precipitate is rinsed with deionized water to prepare a cobalt hydroxide product, wherein the concentration of the sodium hydroxide solution is 120 g / L, the molar ratio of the sodium hydroxide solution to cobalt is 3:1, the temperature is 45° C., and the time is 3 h.

[0037] Table 2 Content of each component in the acid leaching residue of laterite nickel ore

[0038]

[0039] In this embodiment, the direct yield of Co is 98.3%, and the purity of the cobalt hydroxide product is 95.8%.

[0040] Example 3

[0041] A method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction, the specific steps are as follows:

[0042] (1) 2800 g of laterite nickel ore acid leaching residue (the components are shown in Table 3) was dried, ground, and sieved. Ammonia water-ammonium sulfate was used as the leaching system, and the molar ratio of ammonia water to ammonium sulfate was 2:1. The laterite nickel ore acid leaching residue was subjected to 6-stage countercurrent leaching, wherein cobalt ions combined with ammonium ions to form a stable cobalt ammonia complex, which entered the solution in the form of ammonia complex ions to obtain an ammonia leaching solution of laterite nickel ore acid leaching residue, wherein the total concentration of ammonia water-ammonium sulfate was 180 g / L, the liquid-solid ratio was 5:1, the leaching temperature was 65°C, the leaching time was 2.5 h; the pH was 9.5, and the leaching rate of cobalt in the leaching solution was 99.03%.

[0043] (2) adding organic citric acid to the ammonia leachate in step (1), and intensifying the reaction with air at a certain temperature, wherein the cobalt ammonium complex is reduced by citric acid, the amount of citric acid added is 4% of the mass of the laterite nickel ore acid leaching residue, the air flow rate is 120 ml / min, the reduction temperature is 50° C., and the reduction time is 3.5 h to obtain a cobalt-containing product; the cobalt-containing product contains ammonium sulfate.

[0044] (3) adding sodium hydroxide solution to the reduction product in step (2), and simultaneously introducing air at a flow rate of 20 ml / min, wherein the cobalt is converted into cobalt hydroxide precipitate in the presence of ammonium sulfate, the solution is vacuum filtered, and the precipitate is rinsed with deionized water to prepare a cobalt hydroxide product, wherein the concentration of the sodium hydroxide solution is 120 g / L, the molar ratio of the sodium hydroxide solution to cobalt is 2:1, the temperature is 50° C., and the time is 3.5 h.

[0045] Table 3 Content of each component in the red nickel ore acid leaching residue

[0046]

[0047] In this embodiment, the direct yield of Co is 98.2%, and the purity of the cobalt hydroxide product is 95.9%.

[0048] Example 4

[0049] A method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction, the specific steps are as follows:

[0050] (1) 2400 g of laterite nickel ore acid leaching residue (the components are shown in Table 4) was dried, ground, and sieved. Ammonia water-ammonium sulfate was used as the leaching system, and the molar ratio of ammonia water to ammonium sulfate was 2.5:1. The laterite nickel ore acid leaching residue was subjected to four-stage countercurrent leaching, wherein cobalt ions combined with ammonium ions to form a stable cobalt ammonia complex, which entered the solution in the form of ammonia complex ions to obtain an ammonia leaching solution of laterite nickel ore acid leaching residue. The total concentration of ammonia water-ammonium sulfate was 220 g / L, the liquid-solid ratio was 5:1, the leaching temperature was 50°C, the leaching time was 3 h; the pH was 10.5, and the leaching rate of cobalt in the leaching solution was 98.86%.

[0051] (2) adding organic citric acid to the ammonia leachate in step (1), and intensifying the reaction with air at a certain temperature, wherein the cobalt ammonium complex is reduced by citric acid, the amount of citric acid added is 6% of the mass of the laterite nickel ore acid leaching residue, the air flow rate is 160 ml / min, the reduction temperature is 55° C., and the reduction time is 5 h to obtain a cobalt-containing product; the cobalt-containing product contains ammonium sulfate.

[0052] (3) adding sodium hydroxide solution to the reduction product in step (2), and simultaneously introducing air at a flow rate of 60 ml / min, wherein the cobalt is converted into cobalt hydroxide precipitate in the presence of ammonium sulfate, the solution is vacuum filtered, and the precipitate is rinsed with deionized water to prepare a cobalt hydroxide product, wherein the concentration of the sodium hydroxide solution is 140 g / L, the molar ratio of the sodium hydroxide solution to cobalt is 2.5:1, the temperature is 55° C., and the time is 5 h.

[0053] Table 4 Content of each component in the acid leaching residue of nickel ore

[0054]

[0055]

[0056] In this embodiment, the direct yield of Co is 98.5%, and the purity of the cobalt hydroxide product is 96.2%.

[0057] Example 5

[0058] A method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction, the specific steps are as follows:

[0059] (1) 3000 g of laterite nickel ore acid leaching residue (the components are shown in Table 5) was dried, ground, and sieved. Ammonia water-ammonium sulfate was used as the leaching system, and the molar ratio of ammonia water to ammonium sulfate was 3:1. The laterite nickel ore acid leaching residue was subjected to four-stage countercurrent leaching, wherein cobalt ions combined with ammonium ions to form a stable cobalt ammonia complex, which entered the solution in the form of ammonia complex ions to obtain an ammonia leaching solution of laterite nickel ore acid leaching residue, wherein the total concentration of ammonia water-ammonium sulfate was 300 g / L, the liquid-solid ratio was 6:1, the leaching temperature was 80°C, the leaching time was 6 h, and the pH was 10; the leaching rate of cobalt in the leaching solution was 99.01%.

[0060] (2) adding organic citric acid to the ammonia leachate in step (1), and intensifying the reaction with air at a certain temperature, wherein the cobalt ammonium complex is reduced by citric acid, the amount of citric acid added is 10% of the mass of the laterite nickel ore acid leaching residue, the air flow rate is 200 ml / min, the reduction temperature is 60° C., and the reduction time is 6 hours to obtain a cobalt-containing product; the cobalt-containing product contains ammonium sulfate.

[0061] (3) adding sodium hydroxide solution to the reduction product in step (2), and simultaneously introducing air at a flow rate of 100 ml / min, wherein the cobalt is converted into cobalt hydroxide precipitate in the presence of ammonium sulfate, the solution is vacuum filtered, and the precipitate is rinsed with deionized water to prepare a cobalt hydroxide product, wherein the concentration of the sodium hydroxide solution is 150 g / L, the molar ratio of the sodium hydroxide solution to cobalt is 4:1, the temperature is 60° C., and the time is 6 h.

[0062] Table 5 Content of each component in the acid leaching residue of laterite nickel ore

[0063]

[0064] In this embodiment, the direct yield of Co is 98.2%, and the purity of the cobalt hydroxide product is 95.1%.

[0065] Example 6

[0066] The difference between this embodiment and embodiment 1 is that the addition amount of citric acid is replaced with 5% of the mass of the laterite nickel ore acid leaching residue, and the other steps and conditions are the same. The results show that the leaching rate of cobalt in the leachate in this embodiment is 96.22%, the direct recovery rate of Co is 95.86%, and the purity of the cobalt hydroxide product is 94.34%.

[0067] Example 7

[0068] The difference between this embodiment and embodiment 1 is that the addition amount of citric acid is replaced with 10% of the mass of the laterite nickel ore acid leaching residue, and the other steps and conditions are the same. The results show that the leaching rate of cobalt in the leachate in this embodiment is 96.15%, the direct recovery rate of Co is 95.54%, and the purity of the cobalt hydroxide product is 95.05%.

[0069] Example 8

[0070] The difference between this embodiment and embodiment 1 is that the molar ratio of ammonia water to ammonium sulfate in the ammonia water-ammonium sulfate leaching system is replaced with 2:1, and the other steps and conditions are the same. The results show that the leaching rate of cobalt in the leachate in this embodiment is 98.55%, the direct recovery rate of Co is 98.16%, and the purity of the cobalt hydroxide product is 94.88%.

[0071] Example 9

[0072] The only difference between this embodiment and embodiment 1 is that the molar ratio of ammonia water to ammonium sulfate in the ammonia water-ammonium sulfate leaching system is replaced with 3:1, and the other steps and conditions are the same. The results show that the leaching rate of cobalt in the leachate in this embodiment is 98.48%, the direct recovery rate of Co is 98.12%, and the purity of the cobalt hydroxide product is 94.67%.

[0073] Example 10

[0074] The difference between this embodiment and embodiment 1 is that the number of countercurrent leaching stages is replaced with 3 stages, and the other steps and conditions are the same. The results show that the leaching rate of cobalt in the leachate in this embodiment is 97.79%, the direct recovery rate of Co is 97.52%, and the purity of the cobalt hydroxide product is 95.30%.

[0075] Embodiment 11

[0076] The difference between this embodiment and embodiment 1 is that the number of countercurrent leaching stages is replaced with 6 stages, and the other steps and conditions are the same. The results show that the leaching rate of cobalt in the leachate in this embodiment is 98.95%, the direct recovery rate of Co is 98.77%, and the purity of the cobalt hydroxide product is 96.5%.

[0077] Comparative Example 1

[0078] The difference between this comparative example and Example 1 is that conventional leaching is used instead of countercurrent leaching, and the other steps and conditions are the same.

[0079] The results show that the leaching rate of cobalt in the leaching solution in the comparative example is 93.25%, the direct recovery rate of Co is 92.7%, and the purity of the cobalt hydroxide product is 91.4%. Therefore, the multi-stage countercurrent leaching of the present invention is beneficial to improving the direct recovery rate of cobalt element.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that the organic citric acid in step 2 is replaced by an equal amount of hydrazine hydrate, and the other steps and conditions are the same.

[0082] The results show that the direct recovery rate of Co in the comparative example is 94.7%, and the purity of the cobalt hydroxide product is 93.4%. Therefore, the use of citric acid reduction is beneficial to improving the direct recovery rate of cobalt element and the purity of the product, because although the reducing property of hydrazine hydrate is stronger than that of citric acid, the complexing ability of citric acid is significantly better than that of hydrazine hydrate, which is more conducive to the selective reduction of cobalt.

[0083] Comparative Example 3

[0084] The difference between this comparative example and Example 1 is that air is not introduced into the enhanced experiment in step 2, and the other steps and conditions are the same.

[0085] The results show that in this comparative example, air-assisted reaction enhancement was not used, and the direct recovery rate of Co was only 72.1%.

[0086] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction, characterized in that: The laterite nickel ore acid leaching residue is subjected to multi-stage countercurrent leaching using an ammonia water-ammonium sulfate leaching system to obtain a laterite nickel ore acid leaching residue ammonia leaching solution; the laterite nickel ore acid leaching residue ammonia leaching solution is subjected to an oxidation-reduction reaction with citric acid and air to obtain a cobalt-containing product; a strong base is added to the cobalt-containing product to carry out a precipitation reaction in an oxidizing atmosphere to obtain a cobalt hydroxide precipitate.

2. The method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction according to claim 1, characterized in that: The multi-stage countercurrent leaching comprises N-stage countercurrent leaching, and the process of the multi-stage countercurrent leaching is as follows: the first-stage countercurrent leaching adopts the leachate obtained by the second-stage countercurrent leaching as a leaching agent to leach the laterite nickel ore acid leaching residue, and the obtained leaching residue enters the second-stage countercurrent leaching; the second-stage countercurrent leaching adopts the leachate obtained by the third-stage countercurrent leaching as a leaching agent to leach the leaching residue obtained by the first-stage countercurrent leaching; and so on, the N-stage countercurrent leaching adopts the initial leaching agent to leach the leaching residue obtained by the N-1-stage countercurrent leaching; through the dynamic continuous and sufficient contact of the countercurrent flows, the concentration gradient of the solid and liquid phases can be more effectively utilized, thereby improving the leaching efficiency.

3. The method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction according to claim 2, characterized in that: The initial leaching agent is a mixed solution of ammonia water and ammonium sulfate, and the total concentration of ammonia water and ammonium sulfate is 100-500g / L.

4. The method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction according to claim 3, characterized in that: The molar ratio of the ammonia water to ammonium sulfate is (1-3):

1.

5. The method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction according to any one of claims 1 to 4, characterized in that: The multi-stage countercurrent leaching includes 2 to 6 stages of countercurrent leaching, and the liquid-to-solid ratio during each stage of countercurrent leaching is (4 to 8):1, the leaching temperature is 25 to 80° C., the leaching time is 1 to 6 hours, and the pH is controlled to be 9.5 to 10.

5.

6. The method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction according to claim 5, characterized in that: The conditions of the redox reaction are: temperature of 25-60° C., time of 2-8 hours, and air flow rate of 50-500 ml / min.

7. The method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction according to claim 6, characterized in that: The added amount of citric acid is 1-10% of the mass of the laterite nickel ore acid leaching residue.

8. The method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction according to claim 1, characterized in that: The molar ratio of the strong base to the cobalt-containing product is (1-4):1, wherein the cobalt-containing product is calculated based on cobalt and the concentration of the strong base is 50-300 g / L; the strong base is one of sodium hydroxide and potassium hydroxide.

9. The method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction according to claim 8, characterized in that: The conditions of the precipitation reaction are: temperature of 25-60° C., time of 2-8 hours, and an oxidizing atmosphere provided by passing air at a flow rate of 10-100 ml / min.

10. The method for extracting cobalt from laterite nickel ore acid leaching residue by ammonia leaching-citric acid reduction according to claim 1 or 9, characterized in that: The laterite nickel ore acid leaching residue comprises nickel, cobalt, iron, aluminum, manganese, magnesium, zinc, calcium, copper and silicon.

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