Valuable metal recovery method based on slag containing lithium, calcium and magnesium

Abstract

The invention belongs to the technical field of valuable metal resource recovery, and particularly discloses a valuable metal recovery method based on slag containing lithium, calcium and magnesium. The method comprises the following steps: mixing the lithium-containing calcium-magnesium slag with acid liquor for pickling to obtain a solution containing nickel, cobalt and manganese and lithium-containing pickling slag; mixing the lithium-containing acid pickling slag with acid liquor and soluble sodium salt, and performing transformation twice to obtain lithium-containing transformation liquid and transformation slag; performing neutralization and impurity removal on the transformation liquid to obtain a lithium-containing neutralization and impurity removal liquid and neutralization and impurity removal slag; evaporating and concentrating the lithium-containing neutralizing and impurity-removing solution to obtain a lithium-containing concentrated solution and concentrated slag; the lithium-containing concentrated solution is subjected to alkalization calcium removal to obtain a lithium-containing purified solution, then sodium carbonate lithium precipitation is carried out, battery-grade lithium carbonate is obtained, and valuable metal nickel, cobalt, manganese and lithium are recycled. The method can separate and recover most lithium from nickel, cobalt and manganese, the lithium recovery rate reaches 99% or above, and the method has the advantages of being easy and convenient to operate, low in energy consumption, environmentally friendly, high in recovery rate and the like and is suitable for industrial large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of valuable metal resource recovery, and in particular to a valuable metal recovery method based on lithium-calcium-magnesium slag. Background Art

[0002] At present, in waste battery recycling enterprises, especially in the process of wet recycling of ternary batteries, the raw material powder is subjected to reduction acid leaching to obtain an acid leaching solution containing Li, Ni, Co and Mn. Before entering the ternary extraction system, in order to prevent calcium and magnesium from producing calcium sulfate and magnesium sulfate crystals during the extraction process, which will block the pipeline and hinder the normal operation of production, it is necessary to perform chemical unit operations to remove calcium and magnesium from the pre-extraction solution. Major companies generally use sodium fluoride to remove calcium and magnesium ions in the solution. Due to the removal of calcium and magnesium in high-concentration Li, Ni, Co and Mn solutions, a small number of Li, Ni, Co and Mn ions enter the crystal lattices of sodium fluoride, calcium fluoride and magnesium fluoride to form substitution compounds and interstitial compounds. Among them, Li ions react with Al in the solution under this weakly acidic condition. 3+ 、Na + and F - Ionic reactions also easily generate LiNa which is insoluble in water and acid. 2 AlF 6 (lithium sodium cryolite) substances, so it eventually forms complex calcium fluoride slag and magnesium fluoride slag containing valuable metal ions, which are also called calcium magnesium slag (lithium calcium magnesium slag), in which metal lithium contains 6% to 7%, metal nickel contains 5% to 6%, metal cobalt contains 2% to 3%, and metal manganese contains 5% to 6%. This process not only causes the loss of valuable metals, but also the recovery of valuable metals in this complex calcium magnesium slag has become a problem.

[0003] At present, conventional methods such as dilute acid and soluble calcium-magnesium salt transformation cannot effectively recover all valuable metals in calcium-magnesium slag. The reaction between concentrated acid and calcium-magnesium slag generates highly toxic hydrogen fluoride, which pollutes the environment and corrodes equipment. In addition, the high-acid solution containing valuable metals cannot be recovered at low cost. Calcium and magnesium elements are always circulating in the system, and the treatment cost is high. 2 AlF 6 The existence of substances, low Li recovery rate, high residual lithium content in slag, cannot be directly discharged. Therefore, most of the waste battery recycling companies currently have a large amount of calcium-magnesium slag stored, which cannot be discarded and requires a large amount of space for storage, resulting in a waste of resources. Therefore, how to recover the valuable metals in calcium-magnesium slag at low cost and pollution-free and solve the problem of calcium-magnesium slag storage is the focus of research for major companies.

[0004] Invention patent application CN109735709A leaches the valuable metals in the calcium-magnesium slag by transforming soluble magnesium salts under acidic conditions. The leachate is then separated into nickel, cobalt, manganese and lithium by a precipitant. The nickel-cobalt-manganese slag is then acid-dissolved, calcium and magnesium are removed, and extracted to obtain a ternary precursor. The crude lithium solution is then alkalized to remove magnesium and pure ash is used to precipitate lithium to obtain battery-grade lithium carbonate. This method achieves the recovery of valuable metals in the calcium-magnesium slag with good recovery effect. However, due to the introduction of magnesium salts, the process requires a large amount of acid and alkali, and the nickel-cobalt-manganese slag acid solution has a high content of calcium and magnesium impurities. Further calcium and magnesium removal is required to produce new calcium-magnesium slag again, which is costly and does not treat the LiNa in the calcium-magnesium slag. 2 AlF 6 Materials are transformed and recycled.

[0005] Invention patent application CN105838893A converts the valuable metal fluoride in calcium magnesium slag into more insoluble Na2CO3 by using a mixture of aluminum chloride and sodium chloride in a molar ratio of 1:2 as a transformation liquid under acidic conditions. 3 AlF 6 , and then the high-concentration nickel chloride solution is transformed through multiple cycles, and then the raw material or nickel sulfide of the nickel-iron product is recovered through iron powder reduction or sodium sulfide precipitation. This method realizes the recovery of nickel in calcium-magnesium slag, but due to the introduction and transformation of aluminum salts, the impurity content of Al, Ca and Mg in the product is high, which reduces the product quality or increases the production cost for the subsequent impurity removal process. It is also not suitable for the recovery and treatment of lithium-containing calcium-magnesium slag in the field of waste battery recycling.

[0006] Therefore, there is an urgent need to disclose a method for recovering valuable metals in calcium-magnesium slag with simple process and low production cost. Summary of the invention

[0007] In view of this, the present invention provides a valuable metal recovery method based on lithium-calcium-magnesium slag, which solves the problem of recovering valuable metals such as lithium and nickel, cobalt, and manganese in lithium-calcium-magnesium slag, while ensuring that the process is simple, green and environmentally friendly, and has considerable economic benefits.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A valuable metal recovery method based on lithium-calcium-magnesium slag comprises the following steps:

[0010] 1) mixing lithium-calcium-magnesium slag with acid solution and performing pickling, and obtaining a solution containing nickel, cobalt and manganese and a lithium-containing pickling slag after the pickling;

[0011] 2) mixing the lithium-containing pickling slag with an acid solution and a soluble sodium salt to perform a first sodium salt transformation to obtain a first lithium-containing transformation solution and a lithium-containing transformation slag;

[0012] 3) mixing the lithium-containing transformation slag with an acid solution and a soluble sodium salt to perform a second sodium salt transformation to obtain a second lithium-containing transformation solution and transformation slag;

[0013] 4) neutralizing and removing impurities from the first lithium-containing transformation liquid and the second lithium-containing transformation liquid to obtain a lithium-containing neutralization and impurity-removing liquid and a neutralization and impurity-removing slag;

[0014] 5) evaporating and concentrating the lithium-containing neutralization and impurity-removing liquid to obtain a lithium-containing concentrated liquid and concentrated residue;

[0015] 6) alkalizing and decalcifying the lithium-containing concentrated solution to obtain a lithium-containing purified solution and an alkalized decalcified slag;

[0016] 7) The lithium-containing purified liquid is subjected to soda ash precipitation to obtain battery-grade lithium carbonate, thereby realizing the recovery of valuable metals nickel, cobalt, manganese and lithium.

[0017] Preferably, in step 1), the mass volume ratio of lithium-calcium-magnesium slag to acid solution is 1 g: 1-3 mL;

[0018] The pickling temperature in step 1) is 80-90° C., and the pH value of the pickling is 1-2.

[0019] Preferably, the mass volume ratio of the lithium-containing pickling slag to the acid solution in step 2) is 1 g: 4-6 mL; the mass volume ratio of the lithium-containing transformation slag to the acid solution in step 3) is 1 g: 4-6 mL;

[0020] In the step 2), the mass ratio of the soluble sodium salt to the lithium-containing acid-washing slag is 1 to 4:1; in the step 3), the mass ratio of the soluble sodium salt to the lithium-containing transformation slag is 1 to 4:1;

[0021] The mass concentration of the acid solution in step 2) and step 3) is independently 5 to 15%;

[0022] The reaction temperatures of the first sodium salt transformation and the second sodium salt transformation are independently ≥90° C., and the reaction times are independently 6 to 8 hours.

[0023] Preferably, the soluble sodium salt in step 2) and step 3) independently includes one or more of sodium chloride, sodium sulfate and sodium nitrate;

[0024] The acid solutions in step 1), step 2) and step 3) are independently one or more of sulfuric acid, hydrochloric acid and nitric acid.

[0025] Preferably, the pH value of the system for neutralization and impurity removal in step 4) is 7 to 8, and the time for neutralization and impurity removal is 1 to 2 hours.

[0026] Preferably, the mass concentration of Li in the lithium-containing concentrated solution in step 5) is ≥20 g / L;

[0027] The concentrated residue is a soluble sodium salt, which is recycled to step 2) and step 3).

[0028] Preferably, the alkalinization and decalcification in step 6) is to first adjust the pH value of the lithium-containing concentrated solution, then mix it with soda ash, carry out an alkalinization and decalcification reaction, and complete the alkalinization and decalcification.

[0029] Preferably, the pH value of the adjusted lithium-containing concentrated solution is 12-13; the mass volume ratio of soda ash to lithium-containing concentrated solution is 1g:200-300mL;

[0030] The temperature of the alkaline decalcification reaction is 70-80° C., and the time of the alkaline decalcification reaction is 30-60 minutes.

[0031] Preferably, the soda ash lithium precipitation in step 7) is to mix the lithium-containing purification liquid with soda ash or soda ash solution to carry out soda ash lithium precipitation reaction to complete the soda ash lithium precipitation.

[0032] Preferably, the molar ratio of lithium to sodium carbonate in the lithium-containing purification solution in the mixed system is 1:1 to 1.5; the mass concentration of the soda ash solution is 230 to 270 g / L;

[0033] The temperature of the soda ash lithium precipitation reaction is 85-95° C., and the time of the soda ash lithium precipitation reaction is 1-2 hours.

[0034] The reaction equation of step 1) is:

[0035] M(OH) 2 +2H + ===M 2+ +2H 2 O(M 2+ Represents Ni 2+ 、Co 2+ , Mn 2+ )

[0036] The reaction equations of step 2) and step 3) are:

[0037] LiNa 2 AlF 6 +Na + = = = =Na 3 AlF 6 +Li +

[0038] The reaction equation of step 6) is:

[0039] Ca 2+ +2OH - ===Ca(OH) 2 ↓

[0040] Ca 2++CO 3 2- ===CaCO 3 ↓

[0041] The reaction equation of step 7) is:

[0042] 2Li + +CO 3 2- ===Li 2 CO 3 ↓

[0043] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0044] In the present invention, the calcium-magnesium slag is firstly recovered by pickling, and the recovery rates of Ni and Co are more than 98%, and the recovery rate of Mn is more than 80%. The pickling solution enters the ternary impurity removal extraction system to further recover nickel, cobalt and manganese; the lithium-containing pickling slag is then converted into sodium salt twice to recover lithium, and the Li recovery rate is more than 99%. The lithium-containing conversion solution can obtain lithium carbonate after impurity removal and lithium precipitation, and its product quality meets the requirements of battery-grade lithium carbonate (YS / T582-2013). The present invention avoids the disadvantages of high calcium and magnesium impurity content of the conversion solution produced by converting and recovering valuable metals in the calcium-magnesium slag using traditional soluble calcium-magnesium salt solution, complicated subsequent impurity removal process, and high impurity removal cost, and the method of the present invention can separate most of the lithium from nickel, cobalt and manganese, further solving the problem of subsequent separation and high separation cost of lithium-nickel-cobalt-manganese mixed solution, and the lithium recovery rate is more than 99%, with the advantages of simple operation, low energy consumption, green environmental protection, high recovery rate, suitable for industrial large-scale production, and has good social value and considerable economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0046] Figure 1 It is the XRD diagram (Intensity—strength, degree—degree) of the lithium-containing acid-washed slag obtained in Examples 1 to 4 of the present invention. DETAILED DESCRIPTION

[0047] The present invention provides a valuable metal recovery method based on lithium-calcium-magnesium slag, comprising the following steps:

[0048] 1) mixing lithium-calcium-magnesium slag with acid solution and performing pickling, and obtaining a solution containing nickel, cobalt and manganese and a pickling slag containing lithium after the pickling;

[0049] 2) mixing the lithium-containing pickling slag with an acid solution and a soluble sodium salt to perform a first sodium salt transformation to obtain a first lithium-containing transformation solution and a lithium-containing transformation slag;

[0050] 3) Mixing the lithium-containing transformation slag with acid solution and soluble sodium salt to carry out a second sodium salt transformation to obtain a second lithium-containing transformation liquid and transformation slag, wherein the main component of the obtained transformation slag is Na 3 AlF 6 , contains a small amount of impurities and can be used as raw material for preparing cryolite;

[0051] 4) neutralizing and removing impurities from the first lithium-containing transformation liquid and the second lithium-containing transformation liquid to obtain a lithium-containing neutralization and impurity-removing liquid and a neutralization and impurity-removing slag, wherein the obtained neutralization and impurity-removing slag is mainly aluminum fluoride, which can be used as a raw material for preparing cryolite;

[0052] 5) evaporating and concentrating the lithium-containing neutralization and impurity-removing liquid to obtain a lithium-containing concentrated liquid and concentrated residue;

[0053] 6) alkalizing and decalcifying the lithium-containing concentrated solution to obtain a lithium-containing purified solution and an alkalized decalcified slag, wherein the obtained alkalized decalcified slag is mainly calcium hydroxide and calcium carbonate, which can be used in a defluorination process;

[0054] 7) The lithium-containing purified liquid is subjected to soda ash precipitation to obtain battery-grade lithium carbonate, thereby realizing the recovery of valuable metals nickel, cobalt, manganese and lithium.

[0055] In the present invention, the mass volume ratio of the lithium-calcium-magnesium slag to the acid solution in step 1) is 1g:1-3mL, preferably 1g:1.5-2.5mL, and more preferably 1g:2mL.

[0056] In the present invention, the pickling temperature in step 1) is 80-90°C, specifically 82°C, 84°C, 85°C, 86°C, 88°C; the pH value of the pickling is 1-2, specifically 1.2, 1.4, 1.5, 1.6, 1.8.

[0057] In the present invention, the mass volume ratio of the lithium-containing pickling slag to the acid solution in the step 2) is 1g:4-6mL, preferably 1g:4.5-5.5mL, and more preferably 1g:5mL; the mass volume ratio of the lithium-containing transformation slag to the acid solution in the step 3) is 1g:4-6mL, preferably 1g:4.5-5.5mL, and more preferably 1g:5mL.

[0058] In the present invention, in step 2), the mass ratio of the soluble sodium salt to the lithium-containing pickling slag is 1 to 4:1, preferably 2 to 3:1, and more preferably 2.5:1; in step 3), the mass ratio of the soluble sodium salt to the lithium-containing transformation slag is 1 to 4:1, preferably 2 to 3:1, and more preferably 2.5:1.

[0059] In the present invention, the mass concentration of the acid solution in step 2) and step 3) is independently 5-15%, specifically 6%, 8%, 10%, 12%, 14%.

[0060] In the present invention, the reaction temperatures of the first transformation of the sodium salt and the second transformation of the sodium salt are independently ≥90°C, specifically 92°C, 94°C, 95°C, 96°C, 98°C, and 100°C; the reaction times are independently 6 to 8h, specifically 6.2h, 6.4h, 6.5h, 6.8h, 7h, 7.2h, 7.5h, and 7.8h.

[0061] In the present invention, the soluble sodium salt in step 2) and step 3) independently includes one or more of sodium chloride, sodium sulfate and sodium nitrate.

[0062] In the present invention, the acid solutions in step 1), step 2) and step 3) are independently one or more of sulfuric acid, hydrochloric acid and nitric acid.

[0063] In the present invention, the pH value of the system for neutralization and impurity removal in step 4) is 7-8, specifically 7.2, 7.4, 7.5, 7.6, 7.8; the time for neutralization and impurity removal is 1-2h, specifically 1.2h, 1.4h, 1.5h, 1.6h, 1.8h.

[0064] In the present invention, the neutralization and impurity removal in step 4) can be performed by first mixing the first lithium-containing transformation liquid and the second lithium-containing transformation liquid, and then neutralizing and removing impurities, or the first lithium-containing transformation liquid and the second lithium-containing transformation liquid can be neutralized and removed impurities, and then mixed.

[0065] In the present invention, the mass concentration of Li in the lithium-containing concentrated solution in step 5) is ≥20 g / L, specifically 21 g / L, 22 g / L, or 23 g / L.

[0066] In the present invention, the concentrated residue is a soluble sodium salt, which is reused in step 2) and step 3), and some additional addition is still required after reuse.

[0067] In the present invention, the alkalinization and decalcification in step 6) is to first adjust the pH value of the lithium-containing concentrated solution, then mix it with soda ash, perform alkalinization and decalcification reaction, and complete alkalinization and decalcification.

[0068] In the present invention, the pH value of the adjusted lithium-containing concentrated solution is 12-13, specifically 12.2, 12.4, 12.5, 12.6, 12.8; the adjusted pH value is preferably a solution corresponding to sodium hydroxide, potassium hydroxide or lithium hydroxide and the above-mentioned alkali; the mass volume ratio of soda ash to lithium-containing concentrated solution is 1g:200-300mL, preferably 1g:220-280mL, and further preferably 1g:250mL.

[0069] In the present invention, the temperature of the alkaline decalcification reaction is 70-80° C., specifically 72° C., 74° C., 75° C., 76° C., 78° C. The time of the alkaline decalcification reaction is 30-60 min, specifically 35 min, 40 min, 45 min, 50 min, 55 min.

[0070] In the present invention, the soda ash lithium precipitation in step 7) is to mix the lithium-containing purification liquid with soda ash or soda ash solution to carry out soda ash lithium precipitation reaction to complete the soda ash lithium precipitation.

[0071] In the present invention, the molar ratio of lithium to soda ash in the lithium-containing purification solution in the mixed system is 1:1-1.5, preferably 1:1.1-1.4, and more preferably 1:1.2-1.3; the mass concentration of the soda ash solution is 230-270 g / L, specifically 240 g / L, 250 g / L, and 260 g / L.

[0072] In the present invention, the temperature of the soda ash lithium precipitation reaction is 85-95°C, specifically 86°C, 88°C, 90°C, 92°C, and 94°C; the time of the soda ash lithium precipitation reaction is 1-2h, specifically 1.2h, 1.4h, 1.5h, 1.6h, and 1.8h.

[0073] The technical solutions in the embodiments of the present invention are described clearly and completely 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, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0074] Example 1

[0075] The calcium-magnesium slag was mixed with hydrochloric acid solution at a mass volume ratio of 1g:2mL to obtain a mixed solution with a pH of 2, and pickled at 85°C for 2h to obtain a nickel-, cobalt-, and manganese-containing solution and a lithium-containing pickled slag; the obtained lithium-containing pickled slag was slurried with a mass concentration of 7.5% hydrochloric acid solution at a liquid-solid ratio of 6mL:1g, and then sodium chloride of the same mass as the lithium-containing pickled slag was added for transformation, and the reaction conditions were 90°C for 6h. The lithium-containing transformation slag obtained by the first transformation was transformed again using the above operation, and the recovery rates of lithium and nickel, cobalt, and manganese are shown in Table 1. The lithium-containing transformation solution a and the lithium-containing transformation solution b obtained by the two transformations were mixed, and sodium hydroxide was added to adjust the pH value to 7.2, and the impurity removal was carried out for 1.5h. The obtained impurity removal solution was evaporated and concentrated to increase the Li concentration (mass concentration of 20g / L), and the concentrated slag was a soluble sodium salt, which was reused. The concentrated solution was adjusted to pH 12.5 by adding sodium hydroxide, and then 1g:300mL of soda ash was added to react at 80°C for 60min with the mass volume ratio of the lithium-containing concentrated solution, and filtered to obtain the lithium-containing purified solution and the alkaline decalcified slag. The lithium-containing purified solution was heated and a 250g / L soda ash solution with a molar ratio of 1.1 to the lithium in the lithium-containing purified solution was added to precipitate lithium at 95°C for 1.5h, and lithium carbonate was obtained by centrifugation, washing and drying. The chemical composition of lithium carbonate is shown in Table 2, and its quality meets the requirements of battery-grade lithium carbonate (YS / T582-2013).

[0076] Example 2

[0077] The calcium-magnesium slag was mixed with sulfuric acid solution at a mass volume ratio of 1g:1.5mL to obtain a mixed solution with a pH of 1.5, and pickled at 80°C for 2h to obtain a nickel-, cobalt-, manganese-containing solution and a lithium-containing pickled slag; the obtained lithium-containing pickled slag was slurried with a 10% sulfuric acid solution at a liquid-solid ratio of 4mL:1g, and then sodium sulfate three times the mass of the lithium-containing pickled slag was added for transformation, and the reaction conditions were 94°C for 7h. The lithium-containing transformation slag obtained by the first transformation was transformed again using the above operation, and the recovery rates of lithium and nickel, cobalt and manganese are shown in Table 1. The lithium-containing transformation solution a and the lithium-containing transformation solution b obtained by the two transformations were mixed, and sodium hydroxide was added to adjust the pH value to 7.6, and the impurity removal was carried out for 2h. The obtained impurity removal solution was evaporated and concentrated to increase the Li concentration (mass concentration of 22g / L), and the concentrated slag was a soluble sodium salt, which was reused. The concentrated solution was adjusted to pH 12 by adding sodium hydroxide, and then 1g:300mL of soda ash was added to the lithium-containing concentrated solution by mass volume ratio at 80°C for 60min, and filtered to obtain a lithium-containing purified solution and an alkaline decalcified slag. The lithium-containing purified solution was heated and a 230g / L soda ash solution with a molar ratio of 1.3 to the lithium in the lithium-containing purified solution was added to precipitate lithium at 95°C for 1.5h, and lithium carbonate was obtained by centrifugation, washing, and drying. The chemical composition of lithium carbonate is shown in Table 2, and its quality meets the requirements of battery-grade lithium carbonate (YS / T582-2013).

[0078] Example 3

[0079] The calcium-magnesium slag was mixed with nitric acid solution at a mass volume ratio of 1g:2mL to obtain a mixed solution with a pH of 2, and pickled at 90°C for 2h to obtain a nickel-, cobalt-, and manganese-containing solution and a lithium-containing pickled slag; the obtained lithium-containing pickled slag was slurried with a nitric acid solution with a mass concentration of 13% at a liquid-solid ratio of 5mL:1g, and then sodium nitrate twice the mass of the lithium-containing pickled slag was added for transformation, and the reaction conditions were 90°C for 6h. The lithium-containing transformation slag obtained by the first transformation was transformed again using the above operation, and the recovery rates of lithium and nickel, cobalt, and manganese are shown in Table 1. The lithium-containing transformation solution a and the lithium-containing transformation solution b obtained by the two transformations were mixed, and sodium hydroxide was added to adjust the pH value to 7.4, and the impurity removal was carried out for 1.5h. The obtained impurity removal solution was evaporated and concentrated to increase the Li concentration (mass concentration of 20g / L), and the concentrated slag was a soluble sodium salt, which was reused. The concentrated solution was adjusted to pH 13 by adding sodium hydroxide, and then 1g:300mL of soda ash was added to react at 70°C for 60min with the mass volume ratio of the lithium-containing concentrated solution, and filtered to obtain the lithium-containing purified solution and the alkaline decalcified slag. The lithium-containing purified solution was heated and a 250g / L soda ash solution with a molar ratio of 1.5 to the lithium in the lithium-containing purified solution was added to sink the lithium at 95°C for 2h, and lithium carbonate was obtained by centrifugation, washing and drying. The chemical composition of lithium carbonate is shown in Table 2, and its quality meets the requirements of battery-grade lithium carbonate (YS / T582-2013).

[0080] Example 4

[0081] The calcium magnesium slag was mixed with hydrochloric acid solution at a mass volume ratio of 1g:2.5mL to obtain a mixed solution with a pH of 2, and pickled at 85°C for 2h to obtain a nickel, cobalt, manganese solution and a lithium pickled slag; the obtained lithium pickled slag was slurried with a mass concentration of 12% hydrochloric acid solution at a liquid-solid ratio of 4mL:1g, and then sodium chloride three times the mass of the lithium pickled slag was added for transformation, and the reaction conditions were 94°C for 8h. The lithium-containing transformation slag obtained by the first transformation was transformed again using the above operation, and the recovery rates of lithium and nickel, cobalt and manganese are shown in Table 1. The lithium-containing transformation solution a and the lithium-containing transformation solution b obtained by the two transformations were mixed, and sodium hydroxide was added to adjust the pH value to 7.8, and the impurity removal was carried out for 1h. The obtained impurity removal solution was evaporated and concentrated to increase the Li concentration (mass concentration of 23g / L), and the concentrated slag was a soluble sodium salt, which was reused. The concentrated solution was adjusted to pH 12.5 by adding potassium hydroxide, and then reacted at 70°C for 40 minutes with a mass volume ratio of 1g:300mL to the lithium-containing concentrated solution, and filtered to obtain a lithium-containing purified solution and an alkaline decalcified slag. The lithium-containing purified solution was heated and a 270g / L soda ash solution with a molar ratio of 1.1 to the lithium in the lithium-containing purified solution was added to precipitate lithium at 85°C for 1.5 hours, and lithium carbonate was obtained by centrifugation, washing, and drying. The chemical composition of lithium carbonate is shown in Table 2, and its quality meets the requirements of battery-grade lithium carbonate (YS / T582-2013).

[0082] Table 1 Recovery values ​​of Examples 1 to 4

[0083] Li% Ni% Co% Mn% Example 1 99.17 98.9 98.55 82.56 Example 2 99.26 98.4 98.21 82.3 Example 3 99.13 98.2 98.24 82.97 Example 4 99.36 98.46 98.43 82.59

[0084] Table 2 Chemical composition of lithium carbonate in Examples 1 to 4

[0085]

[0086] It can be seen from Table 1 and Table 2 that the Ni and Co recovery rates of Examples 1 to 4 are all higher than 98%, the Mn recovery rate is higher than 80%, and the Li recovery rate is above 99%. The prepared lithium carbonates all meet the requirements of battery-grade lithium carbonate (YS / T 582-2013).

[0087] The XRD patterns of the lithium-containing acid-washed slag obtained in Examples 1 to 4 of the present invention are as follows: Figure 1 As shown (the lithium-containing pickling slags in Examples 1 to 4 are respectively recorded as lithium-containing pickling slag-A, lithium-containing pickling slag-B, lithium-containing pickling slag-C, and lithium-containing pickling slag-D), by Figure 1 It can be seen that the main component of pickling slag is LiNa 2 AlF 6 , lithium can be replaced by sodium salt transformation.

[0088] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0089] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A valuable metal recovery method based on lithium-calcium-magnesium slag, characterized in that: The steps include: 1) mixing lithium-calcium-magnesium slag with acid solution and performing pickling, and obtaining a solution containing nickel, cobalt and manganese and a lithium-containing pickling slag after the pickling; 2) mixing the lithium-containing pickling slag with an acid solution and a soluble sodium salt to perform a first sodium salt transformation to obtain a first lithium-containing transformation solution and a lithium-containing transformation slag; 3) mixing the lithium-containing transformation slag with an acid solution and a soluble sodium salt to perform a second sodium salt transformation to obtain a second lithium-containing transformation solution and transformation slag; 4) neutralizing and removing impurities from the first lithium-containing transformation liquid and the second lithium-containing transformation liquid to obtain a lithium-containing neutralization and impurity-removing liquid and a neutralization and impurity-removing slag; 5) evaporating and concentrating the lithium-containing neutralization and impurity-removing liquid to obtain a lithium-containing concentrated liquid and concentrated residue; 6) alkalizing and decalcifying the lithium-containing concentrated solution to obtain a lithium-containing purified solution and an alkalized decalcified slag; 7) The lithium-containing purified liquid is subjected to soda ash precipitation to obtain battery-grade lithium carbonate, thereby realizing the recovery of valuable metals nickel, cobalt, manganese and lithium.

2. A valuable metal recovery method based on lithium-calcium-magnesium slag according to claim 1, characterized in that: The mass volume ratio of lithium-calcium-magnesium slag to acid solution in step 1) is 1 g: 1-3 mL; The pickling temperature in step 1) is 80-90° C., and the pH value of the pickling is 1-2.

3. A valuable metal recovery method based on lithium-calcium-magnesium slag according to claim 1 or 2, characterized in that: The mass volume ratio of the lithium-containing pickling slag to the acid solution in step 2) is 1 g: 4-6 mL; the mass volume ratio of the lithium-containing transformation slag to the acid solution in step 3) is 1 g: 4-6 mL; In the step 2), the mass ratio of the soluble sodium salt to the lithium-containing acid-washing slag is 1 to 4:1; in the step 3), the mass ratio of the soluble sodium salt to the lithium-containing transformation slag is 1 to 4:1; The mass concentration of the acid solution in step 2) and step 3) is independently 5 to 15%; The reaction temperatures of the first sodium salt transformation and the second sodium salt transformation are independently ≥90° C., and the reaction times are independently 6 to 8 hours.

4. A valuable metal recovery method based on lithium-calcium-magnesium slag according to claim 3, characterized in that: The soluble sodium salt in step 2) and step 3) independently includes one or more of sodium chloride, sodium sulfate and sodium nitrate; The acid solutions in step 1), step 2) and step 3) are independently one or more of sulfuric acid, hydrochloric acid and nitric acid.

5. The method for recovering valuable metals based on lithium-calcium-magnesium slag according to claim 4, characterized in that: The pH value of the neutralization and impurity removal system in step 4) is 7-8, and the neutralization and impurity removal time is 1-2 hours.

6. A valuable metal recovery method based on lithium-calcium-magnesium slag according to claim 5, characterized in that: The mass concentration of Li in the lithium-containing concentrated solution in step 5) is ≥20 g / L; The concentrated residue is a soluble sodium salt, which is recycled to step 2) and step 3).

7. A valuable metal recovery method based on lithium-calcium-magnesium slag according to any one of claims 4 to 6, characterized in that: The alkalinization and decalcification in step 6) is to first adjust the pH value of the lithium-containing concentrated solution, then mix it with soda ash, carry out an alkalinization and decalcification reaction, and complete the alkalinization and decalcification.

8. The method for recovering valuable metals based on lithium-calcium-magnesium slag according to claim 7, characterized in that: The pH value of the adjusted lithium-containing concentrated solution is 12-13; the mass volume ratio of soda ash to lithium-containing concentrated solution is 1 g: 200-300 mL; The temperature of the alkaline decalcification reaction is 70-80° C., and the time of the alkaline decalcification reaction is 30-60 minutes.

9. The method for recovering valuable metals based on lithium-calcium-magnesium slag according to claim 8, characterized in that: The soda ash lithium precipitation in step 7) is to mix the lithium-containing purification liquid with soda ash or soda ash solution to carry out soda ash lithium precipitation reaction to complete the soda ash lithium precipitation.

10. A valuable metal recovery method based on lithium-calcium-magnesium slag according to claim 9, characterized in that: The molar ratio of lithium to sodium carbonate in the lithium-containing purification solution in the mixed system is 1:1-1.5; the mass concentration of the soda ash solution is 230-270 g / L; The temperature of the soda ash lithium precipitation reaction is 85-95° C., and the time of the soda ash lithium precipitation reaction is 1-2 hours.

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