Method for recovering nickel and cobalt from magnesium-containing nickel precipitation residue

Abstract

This invention belongs to the technical field of waste residue recycling, specifically relating to a method for recovering nickel and cobalt from magnesium-containing nickel slag. The method for recovering nickel and cobalt from magnesium-containing nickel slag provided by this invention includes the following steps: (1) Acid leaching: adding hydrofluoric acid and sulfuric acid to the magnesium-containing nickel slag for acid leaching treatment, filtering to obtain acid leaching residue and acid leaching solution; (2) Defluorination: adding lanthanum carbonate to the acid leaching solution, reacting, filtering to obtain defluorinated residue and defluorinated liquid; (3) Lanthanum removal: mixing the defluorinated liquid with P204, extracting to obtain a loaded organic phase and raffinate. This method has a high magnesium removal rate and can enrich and recycle nickel and cobalt in the magnesium-containing nickel slag, achieving resource recovery and utilization. Furthermore, this method has low energy consumption, high safety, and strong operability, making it easy to promote and apply in industrial production.

Description

Technical Field

[0001] This invention belongs to the technical field of waste residue recycling, specifically relating to a method for recovering nickel and cobalt from magnesium-containing nickel slag. Background Technology

[0002] Magnesium-containing nickel slag is a waste residue generated during the wet process of ternary precursor preparation, specifically from the purification of magnesium sulfate solution using magnesium oxide to precipitate nickel and cobalt. Analysis of the magnesium-containing nickel slag revealed that it contains 5.10–14.97% nickel, 1.18–6.19% cobalt, and 10.32–18.58% magnesium. The magnesium-containing nickel slag contains a certain amount of valuable metals such as nickel and cobalt, and thus possesses considerable comprehensive utilization value.

[0003] Currently, there is no effective method for treating magnesium-containing nickel slag. In most cases, it is sold cheaply as waste or disposed of haphazardly, resulting in serious resource waste and environmental pollution. Therefore, it is urgent to find suitable methods for treating magnesium-containing nickel slag to reduce the environmental pollution and resource waste caused by its indiscriminate dumping, while effectively recovering valuable metals from the slag. Summary of the Invention

[0004] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0005] Magnesium fluoride is a sparingly soluble substance, and its K... SP Only 5.13*10 -11 (mol / L) 3 Magnesium in solution can be removed by forming magnesium fluoride.

[0006] Current processes typically use sodium fluoride for magnesium removal. Calculations based on the magnesium-containing nickel slag after water washing show that if the nickel + cobalt concentration after leaching reaches 60 g / L or higher, the magnesium concentration can reach 12 g / L or higher. If sodium fluoride is used for magnesium removal, according to the chemical formula Mg... 2+ +2NaF→MgF2+2Na + Calculations show that the sodium content in the solution reached over 23 g / L after the magnesium removal process was completed, and the final sodium content in the solution is expected to exceed 25 g / L, far exceeding the standard of less than 8 g / L for sodium content in sulfate solutions.

[0007] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for recovering nickel and cobalt from magnesium-containing nickel slag. This method achieves a high magnesium removal rate and simultaneously enriches and recycles the nickel and cobalt in the magnesium-containing nickel slag, realizing resource recovery and utilization. Furthermore, this method has low energy consumption, high safety, and strong operability.

[0008] The method for recovering nickel and cobalt from magnesium-containing nickel slag according to embodiments of the present invention includes the following steps:

[0009] (1) Acid leaching: Add hydrofluoric acid and sulfuric acid to magnesium-containing nickel slag for acid leaching treatment, and filter to obtain acid leaching residue and acid leaching solution;

[0010] (2) Defluorination: Lanthanum carbonate is added to the acid leaching solution obtained in step (1), and the solution is filtered after reaction to obtain defluorinated residue and defluorinated liquid;

[0011] (3) Lanthanum removal: The defluorinated liquid obtained in step (2) is mixed with P204 and extracted to obtain a loaded organic phase and raffinate.

[0012] The advantages and technical effects of the method for recovering nickel and cobalt from magnesium-containing nickel slag according to embodiments of the present invention are as follows: 1. The method of the present invention uses hydrofluoric acid for magnesium removal. Hydrofluoric acid can provide fluoride ions, which react with magnesium ions to generate magnesium fluoride for magnesium removal, while avoiding the introduction of impurity ions such as sodium; 2. The method of the present invention uses hydrofluoric acid for magnesium removal, and can also replace part of the sulfuric acid for acid leaching. It can selectively leach cobalt and nickel without leaching magnesium, which is more selective and conducive to improving the recovery rate of nickel and cobalt; 3. The method of the present invention has a high magnesium removal rate, and can enrich the nickel and cobalt in the magnesium-containing nickel slag and make it re-resourced, realizing the recycling of resources. Moreover, the method has low energy consumption, high safety, strong operability, and is easy to promote and apply in industrial production.

[0013] In some embodiments, step (1) further includes first washing the magnesium-containing nickel slag with water, filtering to obtain a washing liquid and a washing residue, and then acid leaching the washing residue.

[0014] In some embodiments, in step (1), the amount of hydrofluoric acid added is 1.8 to 2.2 times the magnesium content in the water-washed residue, by weight; and / or, the pH of the acid leaching is controlled to be 3.5 to 4.5.

[0015] In some embodiments, in step (1), the acid leaching temperature is 70-85°C and the acid leaching time is 2-4 hours.

[0016] In some embodiments, in step (2), the amount of lanthanum carbonate added is 8 to 10 times the fluorine content in the leaching solution, by weight.

[0017] In some embodiments, in step (2), the reaction temperature is 70-85°C and the reaction time is 2-4 hours.

[0018] In some embodiments, in step (3), the defluorinated liquid and P204 are mixed at an A / O ratio of 3 to 5:1, the extraction temperature is 45 to 60°C, and the extraction time is 5 to 10 minutes.

[0019] In some embodiments, step (3) further includes sequentially washing, back-extracting, anti-iron treatment, and chlorine washing of the supported organic phase.

[0020] In some embodiments, the acid leaching residue is further subjected to a water washing treatment.

[0021] In some embodiments, the process further includes step (4) oil removal: adding activated carbon and hydrogen peroxide to the raffinate for oil removal treatment, and filtering to obtain the oil-removed liquid. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of recovering nickel and cobalt from magnesium-containing nickel slag in Example 1;

[0023] Figure 2 This is a process flow diagram of recovering nickel and cobalt from magnesium-containing nickel slag in Example 3. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] The method for recovering nickel and cobalt from magnesium-containing nickel slag according to embodiments of the present invention includes the following steps:

[0026] (1) Acid leaching: Add hydrofluoric acid and sulfuric acid to magnesium-containing nickel slag for acid leaching treatment, and filter to obtain acid leaching residue and acid leaching solution;

[0027] (2) Defluorination: Lanthanum carbonate is added to the acid leaching solution obtained in step (1), and the solution is filtered after reaction to obtain defluorinated residue and defluorinated liquid;

[0028] (3) Lanthanum removal: The defluorinated liquid obtained in step (2) is mixed with P204 and extracted to obtain a loaded organic phase and raffinate.

[0029] The method for recovering nickel and cobalt from magnesium-containing nickel slag in this invention uses hydrofluoric acid for magnesium removal. Hydrofluoric acid provides fluoride ions, which react with magnesium ions to generate magnesium fluoride for magnesium removal, while avoiding the introduction of impurity ions such as sodium. Using hydrofluoric acid for magnesium removal can also replace part of the sulfuric acid leaching process, selectively leaching cobalt and nickel without leaching magnesium, resulting in good selectivity and improved nickel and cobalt recovery rates. The method achieves a high magnesium removal rate and enriches the nickel and cobalt in the magnesium-containing nickel slag for reuse, realizing resource recycling. Furthermore, this method has low energy consumption, high safety, and strong operability, making it easy to promote and apply in industrial production.

[0030] In some embodiments, preferably, step (1) further includes first washing the magnesium-containing nickel slag with water, filtering to obtain a washing solution and a washing residue, and then acid leaching the washing residue. More preferably, the solid-liquid weight ratio of the magnesium-containing nickel slag to water in the washing process is 1:2 to 3.

[0031] In this embodiment of the invention, magnesium-containing nickel slag is subjected to water washing treatment, and the solid-liquid ratio of magnesium-containing nickel slag to water in the water washing treatment is optimized. After water washing, the magnesium content in the washed slag is significantly reduced, which has a certain promoting effect on the removal of magnesium from the magnesium-containing nickel slag, thereby effectively reducing the consumption of hydrofluoric acid during acid leaching treatment. If the solid-liquid ratio is too high, the solution is too viscous, the cleaning effect of magnesium-containing nickel slag is poor, and the removal rate of magnesium in the magnesium-containing nickel slag is affected. If the solid-liquid ratio is too low, a large amount of water is required, and the amount of water generated is also large, increasing the treatment cost.

[0032] In some embodiments, preferably, the water washing process includes two water washings, which are performed using a counter-current water washing method. The first water washing includes: adding magnesium-containing nickel slag to water, wherein the solid-liquid weight ratio of the magnesium-containing nickel slag to water is 1:2-3, the water washing temperature is 50-60°C, the water washing time is 1-3 hours, and filtering to obtain primary water washing residue and primary water washing liquid. The second water washing includes: adding the primary water washing residue to fresh industrial water, wherein the solid-liquid weight ratio of the primary water washing residue to fresh industrial water is 1:2-3, the water washing temperature is 50-60°C, the water washing time is 1-3 hours, and filtering to obtain secondary water washing residue and secondary water washing liquid. The secondary water washing residue is used in the acid leaching process, and the secondary water washing liquid is returned to the primary water washing process. More preferably, the water washing treatment further includes a third water washing, which includes: adding the secondary water washing residue to industrial fresh water, wherein the solid-liquid weight ratio of the secondary water washing residue to the industrial fresh water is 1:2 to 3, the water washing temperature is 50-60℃, the water washing time is 1 to 2 hours, and filtering to obtain the tertiary water washing residue and the tertiary water washing liquid, wherein the tertiary water washing residue is used in the acid leaching process.

[0033] In this embodiment of the invention, multiple water washings of the magnesium-containing nickel slag can significantly reduce the magnesium content in the slag, further reducing the consumption of hydrofluoric acid. When two water washes are used, the magnesium removal rate can reach 50%, and the removal effect is even better with three water washes, reaching 55%. Further increasing the number of water washes does not significantly increase the magnesium removal effect. Furthermore, using a countercurrent washing method can effectively reduce water consumption and lower treatment costs.

[0034] In some embodiments, preferably, in step (1), the amount of hydrofluoric acid added is 1.8 to 2.2 times the magnesium content in the water-washed residue, by weight; and / or, the pH of the acid leaching is controlled at 3.5 to 4.5. More preferably, in step (1), the acid leaching temperature is 70 to 85°C, and the acid leaching time is 2 to 4 hours. Even more preferably, the concentration of the hydrofluoric acid is 30 to 50 wt%, preferably 40 wt%.

[0035] In this embodiment of the invention, the amounts of hydrofluoric acid and sulfuric acid added are further optimized to better remove magnesium from magnesium-containing nickel slag. If the amount of hydrofluoric acid added is too small, the fluorine content in the solution will be low, and magnesium ions cannot be completely precipitated, resulting in a high magnesium ion content in the solution and a low magnesium removal rate. If the amount of hydrofluoric acid added is too large, the fluorine content in the solution will be high, requiring more lanthanum carbonate for subsequent defluorination, increasing the processing cost. Adjusting the pH value to 3.5-4.5 with sulfuric acid allows for sufficient leaching of nickel and cobalt. If the pH is too high, the amount of sulfuric acid added will be too small, affecting the leaching effect of nickel and cobalt and reducing the leaching rate. If the pH is too low, the generated magnesium fluoride is easily re-dissolved, affecting the magnesium removal effect.

[0036] In some embodiments, preferably, step (1) further includes adding water to the washing residue before adding hydrofluoric acid and sulfuric acid. More preferably, the solid-liquid weight ratio of the washing residue to water is 1:1 to 3.

[0037] In some embodiments, preferably, in step (2), the amount of lanthanum carbonate added is 8 to 10 times the fluorine content in the acid leaching solution, by weight. More preferably, in step (2), the reaction temperature is 70 to 85°C, and the reaction time is 2 to 4 hours.

[0038] In this embodiment of the invention, the dosage of lanthanum carbonate and the reaction conditions were further optimized so that the lanthanum content in the solution was about 1 g / L, which can effectively remove fluoride from the acid leaching solution. If too much lanthanum carbonate is added, although the defluorination effect is good, more lanthanum will enter the defluorinated solution, and the subsequent defluorinated solution will require more organic extractant and acid to remove lanthanum from the solution, which increases the processing cost of lanthanum removal. If the reaction temperature is too low, the lanthanum carbonate defluorination effect is poor; if the reaction temperature is too high, the energy consumption will increase.

[0039] In some embodiments, preferably, in step (3), the defluorinated liquid and P2O4 are mixed at an A / O ratio of 3–5:1, the extraction temperature is 45–60°C, and the extraction time is 5–10 min. More preferably, step (3) further includes sequentially washing, back-extracting, deferroplating, and chlorine washing of the supported organic phase. Even more preferably,

[0040] The washing process includes: adding dilute sulfuric acid to the loaded organic phase at an O / A ratio of 1 to 2:1 to wash, obtaining a washing liquid and a washing organic phase. The washing liquid is returned to the acid leaching process for reuse. The concentration of the dilute sulfuric acid is 50 to 100 g / L.

[0041] The back-extraction includes: adding dilute sulfuric acid to the washed organic phase at an O / A ratio of 1 to 2:1 to perform back-extraction, thereby obtaining a back-extraction solution and a back-extracted organic phase, wherein the concentration of the dilute sulfuric acid is 200 to 300 g / L;

[0042] The anti-iron process includes: adding dilute hydrochloric acid to the organic phase after back-extraction to obtain an anti-iron liquid and an anti-iron organic phase, wherein the concentration of the dilute hydrochloric acid is 5-6 mol / L;

[0043] The chlorine washing process includes: adding dilute sulfuric acid to the organic phase after antiferrolysis to obtain a chlorine washing solution and an empty organic phase P204. The empty organic phase P204 is returned to the lanthanum removal process. The concentration of the dilute sulfuric acid is 10-20 g / L.

[0044] In this embodiment of the invention, P204 is used for lanthanum removal, which can selectively remove lanthanum from the defluorination solution with high efficiency and easy operation. The loaded organic phase is washed, back-extracted, de-ironized and chlorine-washed to obtain an empty organic phase free of impurities. The empty organic phase is returned to the lanthanum removal process for recycling, which can reduce processing costs.

[0045] In some embodiments, preferably, the acid leaching residue is further subjected to a water washing treatment. More preferably, the acid leaching residue water washing process includes adding the acid leaching residue to water, wherein the solid-liquid weight ratio of the acid leaching residue to water is 1:1 to 2, the water washing temperature is 50 to 60°C, the water washing time is 1 to 2 hours, filtering to obtain acid leaching water-washed residue and acid leaching residue washing liquid, and returning the acid leaching residue washing liquid to the acid leaching process for reuse.

[0046] In this embodiment of the invention, the nickel and cobalt entrained in the acid leaching residue can be washed into the solution through the acid leaching residue washing process, reducing the loss of nickel and cobalt and helping to further improve the recovery rate of nickel and cobalt.

[0047] In some embodiments, preferably, the process further includes step (4) an oil removal step: adding activated carbon and hydrogen peroxide to the raffinate for oil removal treatment, and filtering to obtain the oil-removed liquid. More preferably, the amount of activated carbon added is 1-2 kg / m³. 3The amount of hydrogen peroxide added to the raffinate is 1-3 L / m³. 3 Residual extract.

[0048] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0049] Example 1

[0050] The processing flow of this embodiment is as follows: Figure 1 As shown:

[0051] (1) Acid leaching

[0052] Take 200g of magnesium-containing nickel slag, add 240mL of water, and slowly add 23mL of hydrofluoric acid (40wt%) while stirring in an 80℃ water bath. The hydrofluoric acid concentration is 1.9 times the magnesium content in the magnesium-containing nickel slag. Add 12mL of sulfuric acid to adjust the pH value to 4.5. After stirring for 2 hours, filter to obtain 230mL of acid leaching solution and 125g of acid leaching residue.

[0053] (2) Defluorination

[0054] Take 250 mL of acid leaching solution and add 8 g of lanthanum carbonate under stirring in a 70℃ water bath. The amount of lanthanum carbonate added is 10 times the fluorine content in the acid leaching solution. Stir for 2 hours and then filter to obtain 240 mL of defluorinated solution and defluorinated residue.

[0055] (3) Lanthanum removal

[0056] Take 200 mL of the defluorinated liquid and 50 mL of the empty organic phase P204, stir and extract at 60 °C for 8 min, then separate the liquid in a separatory funnel to obtain 200 mL of raffinate and 50 mL of the loaded organic phase. The loaded organic phase is back-extracted with 50 mL of 200 g / L dilute sulfuric acid to obtain 50 mL of back-extract.

[0057] Example 2

[0058] The method is the same as in Example 1, except that in step (2), 125g of acid leaching residue is taken and washed with water at 60°C at a liquid-to-solid weight ratio of 3:1. After filtration, 350mL of acid leaching residue washing liquid is obtained and returned to the acid leaching process for reuse.

[0059] Example 3

[0060] The processing flow of this embodiment is as follows: Figure 2 As shown:

[0061] (1) Three washes

[0062] Take 530g of magnesium-containing nickel slag in a beaker, add 1325mL of water at a solid-liquid weight ratio of 1:2.5, and stir and wash for 2 hours in a 60℃ water bath. After observing that there are no large particles in the beaker, filter to obtain 1130mL of the first washing solution and 685g of the first washing residue.

[0063] Place 685g of the first washing residue in a beaker, add 1370mL of water at a solid-liquid weight ratio of 1:2 for magnesium-containing nickel precipitate residue to water, stir and wash for 1 hour in a 60℃ water bath, and filter to obtain 1310mL of the second washing solution and 680g of the second washing residue.

[0064] Place 680g of secondary washing residue in a beaker, add 1360mL of water at a solid-liquid weight ratio of 1:2 for magnesium-containing nickel precipitate residue to water, stir and wash for 1 hour under a 60℃ water bath, and filter to obtain 1340mL of tertiary washing liquid and 650g of tertiary washing residue.

[0065] The washing residue and washing liquid were tested, and the results are shown in Table 1 and Table 2, respectively.

[0066] Table 1. Data on the test results of water washing residue

[0067] Ni / % Co / % Mg / % <![CDATA[H2O / %]]> Magnesium-containing nickel slag 19.96 6.85 15.12 55.61 One-time water washing residue 18.81 6.35 11.1 63.48 Secondary washing residue 22.12 7.54 8.15 66.1 Three-times water washing residue 23.11 7.31 6.13 62.41

[0068] Table 2. Data on the test results of the washing solution.

[0069] Ni (g / L) Co(g / L) Mg(g / L) One time lotion 0.0077 0.0026 16.08 Secondary washing solution 0.023 0.003 3.63 Three times of washing liquid 0.0082 0.0017 1.74

[0070] The test data in the table above shows that the water washing process did not cause any loss of nickel and cobalt. However, the magnesium content in the magnesium-containing nickel slag was significantly reduced after water washing, and the magnesium content in each washing solution decreased accordingly. The magnesium content in the three washing solutions was less than 2 g / L. According to the data, the magnesium removal rates of the first, second, and third washing solutions were 40%, 10%, and 5%, respectively. This indicates that the water washing process can reduce the magnesium content in the slag to a certain extent, but the magnesium removal effect is no longer significant after multiple washings.

[0071] (2) Acid leaching

[0072] Take 200g of the residue from three washings, add 240mL of water, stir in an 80℃ water bath, slowly add 8mL of hydrofluoric acid (40% concentration, 1.9 times the magnesium content in the residue from three washings), then slowly add 22mL of sulfuric acid to adjust the pH to 4.5, stir for 2 hours and filter, yielding 260mL of acid leaching solution and 100g of acid leaching residue.

[0073] Take 100g of acid leaching residue, wash it with water at 60℃ at a liquid-to-solid weight ratio of 3:1, filter to obtain 320mL of acid leaching residue washing liquid, and return the acid leaching residue washing liquid to the acid leaching process for reuse.

[0074] (3) Defluorination

[0075] Take 250 mL of acid leaching solution and add 8 g of lanthanum carbonate under stirring in a water bath at 70 °C. The amount of lanthanum carbonate added is 10 times the fluorine content in the acid leaching solution. Stir for 2 h and then filter to obtain 240 mL of defluorinated solution and defluorinated residue.

[0076] (4) Lanthanum removal

[0077] Take 200 mL of the defluorinated liquid and 50 mL of the empty organic phase P204, stir and extract at 60 °C for 8 min, then separate the liquid in a separatory funnel to obtain 200 mL of raffinate and 50 mL of the loaded organic phase. The loaded organic phase is back-extracted with 50 mL of 200 g / L dilute sulfuric acid to obtain 50 mL of back-extract.

[0078] Example 4

[0079] The method is the same as in Example 3, except that in step (2), 200g of secondary washing residue is taken, 240mL of water is added, and the mixture is stirred in an 80℃ water bath. 10mL of hydrofluoric acid is slowly added. The concentration of hydrofluoric acid is 40%, and the hydrofluoric acid is 1.9 times the magnesium content in the secondary washing residue. 25mL of sulfuric acid is added to adjust the pH value to 4.5. After stirring for 2 hours, the mixture is filtered to obtain 250mL of acid leaching solution and 105g of acid leaching residue.

[0080] Take 105g of acid leaching residue, wash it with water at 60℃ at a liquid-to-solid weight ratio of 3:1, filter to obtain 330mL of acid leaching residue washing liquid, and return the acid leaching residue washing liquid to the acid leaching process for reuse.

[0081] Example 5

[0082] The method is the same as in Example 3, except that in step (3), 250 mL of acid leaching solution is taken and 12 g of lanthanum carbonate is added under the stirring condition of a water bath at 70°C. The amount of lanthanum carbonate added is 15 times the fluorine content in the acid leaching solution. After stirring for 2 hours, the solution is filtered to obtain 240 mL of defluorinated solution.

[0083] Step (4): Take 200 mL of the defluorinated liquid and 100 mL of the empty organic phase P204, stir and extract at 60 °C for 8 min, then separate the liquid in a separatory funnel to obtain 200 mL of raffinate and 100 mL of the loaded organic phase. The loaded organic phase is back-extracted with 100 mL of 200 g / L dilute sulfuric acid to obtain 100 mL of back-extracted liquid.

[0084] Example 6

[0085] The method is the same as in Example 3, except that in step (4), 200 mL of the defluorinated liquid and 50 mL of P204 empty organic phase are taken and extracted at 60°C for 8 min. The mixture is then separated in a separatory funnel to obtain 200 mL of raffinate and 50 mL of loaded organic phase. The loaded organic phase is first washed with 50 mL of 100 g / L dilute sulfuric acid to obtain 50 mL of washing solution. The washed organic phase is then back-extracted with 50 mL of 200 g / L dilute sulfuric acid to obtain 50 mL of back-extracted solution.

[0086] Example 7

[0087] The method is the same as in Example 3, except for step (2). Take 200g of the three-time washing residue, add 240mL of water, stir in a water bath at 70°C, slowly add 6mL of hydrofluoric acid with a concentration of 40%, and the hydrofluoric acid is 1.1 times the magnesium content in the three-time washing residue. Then slowly add 25mL of sulfuric acid to adjust the pH to 4.5, stir for 2 hours and filter to obtain 250mL of acid leaching solution and 75g of acid leaching residue.

[0088] Take 75g of acid leaching residue, wash it with water at 60℃ at a liquid-to-solid weight ratio of 3:1, filter to obtain 250mL of acid leaching residue washing liquid, and return the acid leaching residue washing liquid to the acid leaching process for reuse.

[0089] Example 8

[0090] The method is the same as in Example 3, except that in step (2), 200g of the three-time washing residue is added to 240mL of water, stirred in an 80℃ water bath, and 8mL of hydrofluoric acid is slowly added. The concentration of hydrofluoric acid is 40%, and the hydrofluoric acid is 1.9 times the magnesium content in the three-time washing residue. 30mL of sulfuric acid is added to adjust the pH value to 2.5. After stirring for 2 hours, the mixture is filtered to obtain 270mL of acid leaching solution and 80g of acid leaching residue.

[0091] Take 80g of acid leaching residue, wash it with water at 60℃ at a liquid-to-solid weight ratio of 3:1, and filter to obtain 250mL of acid leaching residue washing solution.

[0092] Example 9

[0093] The method is the same as in Example 3, except that in step (3), 250 mL of acid leaching solution is taken and 4 g of lanthanum carbonate is added under stirring conditions in a water bath at 70 °C. The amount of lanthanum carbonate added is 5 times the fluorine content in the acid leaching solution. After stirring for 2 hours, the solution is filtered to obtain 240 mL of defluorinated solution.

[0094] Experimental Example

[0095] (1) The acid leaching solutions and acid leaching residue washing solutions of Examples 1-4 and Examples 7-8 were tested, and the results are shown in Tables 3 and 4, respectively:

[0096] Table 3. Test results of acid leaching solution (unit: g / L)

[0097] Ni Co Mg F Nickel leaching rate (%) Cobalt leaching rate (%) Example 1 56.47 13.17 0.011 3.15 74.76 55.12 Example 2 56.47 13.17 0.011 3.15 74.76 55.12 Example 3 50.84 11.49 0.0066 3.11 76.08 54.36 Example 4 46.12 10.6 0.0057 3.44 76.88 51.84 Example 7 52.42 12.95 0.028 3.02 75.43 58.91 Example 8 51.84 13.21 0.03 3.20 80.56 64.90

[0098] Table 4. Test results of acid leaching residue washing solution (unit: g / L)

[0099] Ni Co Mg F Nickel leaching rate (%) Cobalt leaching rate (%) Example 2 9.51 2.8 0.035 2.96 19.16 17.83 Example 3 10.73 2.59 0.0038 2.42 19.76 15.08 Example 4 9.48 2.45 0.0076 2.43 20.86 15.82 Example 7 9.22 2.64 0.0054 2.11 18.57 16.81 Example 8 9.51 2.18 0.019 2.75 13.68 9.92

[0100] Conclusion: Calculations based on Examples 1-4 and Examples 7-8 show that the leaching rate of nickel in the acid leaching solution is 74-80%, and the leaching rate of cobalt is 51-64%. Example 1 used unwashed magnesium-containing nickel slag, which had a high magnesium content, requiring more hydrofluoric acid to reduce the magnesium to a acceptable level. Examples 2 and 3 used washed slag, which had a lower magnesium content, requiring less hydrofluoric acid. After washing, the total leaching rate of nickel was 90-95%, and the total leaching rate of cobalt was 72-75%. However, when the amount of hydrofluoric acid added is reduced (Example 7), the magnesium-containing nickel slag is not washed (Example 1), or the pH is too low (Example 8), the magnesium content in the acid leaching solution becomes too high, reducing the magnesium removal efficiency.

[0101] (2) The defluorination solutions from Examples 2, 3, 5 and 9 were tested, and the results are shown in Table 5:

[0102] Table 5. Test results of the defluorinated solution (unit: g / L)

[0103] Ni Co Mg F <![CDATA[La2O3]]> Fluorine removal rate (%) Example 2 41.99 10.79 0.022 0.07 0.12 97.83 Example 3 43.69 10.68 0.0006 0.05 0.13 98.45 Example 5 41.92 9.96 0.0058 0.01 0.27 99.66 Example 9 42.65 9.87 0.016 0.73 0.16 77.32

[0104] Conclusion: By comparing the results of acid leaching solution and defluorinated solution, it was found that adding a certain amount of lanthanum carbonate can effectively remove fluoride from the solution, with a fluoride removal rate as high as 97%. However, when the amount of lanthanum carbonate added is small (Example 9), the fluoride removal rate decreases. When the amount of lanthanum carbonate added is large (Example 5), although the fluoride removal rate can reach as high as 99.66% and the defluorination effect is better, the defluorinated solution requires more organic extractant and acid to remove lanthanum, increasing the cost of lanthanum removal treatment.

[0105] (3) The raffinate, back-extraction solution, and washing solution produced in Examples 3 and 6 were tested, and the results are shown in Table 6:

[0106] Table 6. Statistical table of detection data during the extraction process (unit: g / L)

[0107]

[0108] Conclusion: Analysis of the data in Table 6 shows that the lanthanum content in the raffinate is very low, indicating that P204 extraction can effectively remove lanthanum from the defluorinated solution.

[0109] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0110] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for recovering nickel and cobalt from magnesium-containing nickel slag, characterized in that, Includes the following steps: (1) Acid leaching: Hydrofluoric acid and sulfuric acid are added to magnesium-containing nickel slag for acid leaching treatment, and the acid leaching residue and acid leaching solution are obtained by filtration; the pH of the acid leaching is controlled at 3.5~4.5; (2) Defluorination: Lanthanum carbonate is added to the acid leaching solution obtained in step (1), and the solution is filtered after reaction to obtain defluorinated residue and defluorinated liquid; (3) Lanthanum removal: The defluorinated liquid obtained in step (2) is mixed with P204 and extracted to obtain a loaded organic phase and raffinate; the defluorinated liquid and P204 are mixed at A / O=3~5:1, the extraction temperature is 45~60℃, and the extraction time is 5~10min.

2. The method for recovering nickel and cobalt from magnesium-containing nickel slag according to claim 1, characterized in that, The step (1) further includes first washing the magnesium-containing nickel slag with water, filtering to obtain washing liquid and washing slag, and then acid leaching the washing slag.

3. The method for recovering nickel and cobalt from magnesium-containing nickel slag according to claim 2, characterized in that, In step (1), the amount of hydrofluoric acid added is 1.8 to 2.2 times the magnesium content in the water-washed residue, by weight.

4. The method for recovering nickel and cobalt from magnesium-containing nickel slag according to claim 3, characterized in that, In step (1), the acid leaching temperature is 70~85℃ and the acid leaching time is 2~4h.

5. The method for recovering nickel and cobalt from magnesium-containing nickel slag according to claim 1, characterized in that, In step (2), the amount of lanthanum carbonate added is 8 to 10 times the fluorine content in the acid leaching solution, by weight.

6. The method for recovering nickel and cobalt from magnesium-containing nickel slag according to claim 1 or 5, characterized in that, In step (2), the reaction temperature is 70~85℃ and the reaction time is 2~4h.

7. The method for recovering nickel and cobalt from magnesium-containing nickel slag according to claim 1, characterized in that, Step (3) further includes sequentially washing, back-extracting, iron removal, and chlorine washing of the supported organic phase.

8. The method for recovering nickel and cobalt from magnesium-containing nickel slag according to claim 1, characterized in that, It also includes washing the acid leaching residue with water.

9. The method for recovering nickel and cobalt from magnesium-containing nickel slag according to claim 1, characterized in that, It also includes step (4) oil removal process: adding activated carbon and hydrogen peroxide to the raffinate for oil removal treatment, and filtering to obtain the oil-removed liquid.

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