A valuable metal recovery method based on lithium-containing calcium-magnesium slag

Abstract

The present application belongs to the technical field of valuable metal resource recovery, and specifically discloses a valuable metal recovery method based on lithium, calcium and magnesium-containing slag. The lithium, calcium and magnesium-containing slag is mixed with acid liquid for pickling to obtain a nickel, cobalt and manganese-containing solution and a lithium-containing pickling slag; the lithium-containing pickling slag is mixed with acid liquid and soluble sodium salt for two times of transformation to obtain lithium-containing transformation liquid and transformation slag; the transformation liquid is subjected to neutralization and impurity removal to obtain lithium-containing neutralization and impurity removal liquid and neutralization and impurity removal slag; the lithium-containing neutralization and impurity removal liquid is subjected to evaporation and concentration to obtain lithium-containing concentrated liquid and concentrated slag; the lithium-containing concentrated liquid is subjected to alkalinization and calcium removal to obtain lithium-containing purified liquid, which is then subjected to lithium precipitation with soda ash to obtain battery-grade lithium carbonate, thereby realizing recovery of valuable metals nickel, cobalt, manganese and lithium. The present application can separate most of the lithium from nickel, cobalt and manganese for recovery, with a lithium recovery rate of more than 99%, and has the advantages of simple operation, low energy consumption, green environmental protection, high recovery rate and the like, and is suitable for industrialized large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of valuable metal resource recovery, and particularly relates to a valuable metal recovery method based on lithium-containing calcium-magnesium slag. BACKGROUND

[0002] Currently, in the waste battery recycling enterprises, especially in the ternary battery wet recovery process, 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 in the extraction process, blocking the pipeline and hindering the normal operation of production, chemical unit operations for removing calcium and magnesium from the pre-extraction solution are required. Most enterprises generally use sodium fluoride to remove calcium and magnesium ions in the solution. Due to the removal of calcium and magnesium in the high-concentration Li, Ni, Co and Mn solution, a small part of Li, Ni, Co and Mn ions enter the crystal lattice of sodium fluoride, calcium fluoride and magnesium fluoride to form substitution compounds and interstitial compounds. Among them, Li ions also easily react with Al 3+ , Na + and F - ions in the solution under weak acid conditions to generate LiNa2AlF6 (lithium sodium cryolite) which is difficult to dissolve in water and acid, so that a complex calcium fluoride slag and magnesium fluoride slag containing valuable metal ions is finally formed, which is also called calcium-magnesium slag (lithium-containing calcium-magnesium slag). The metal lithium content is 6% to 7%, the metal nickel content is 5% to 6%, the metal cobalt content is 2% to 3%, and the metal manganese content is 5% to 6%. This process not only causes the loss of valuable metals, but also makes the recovery of valuable metals in this complex calcium-magnesium slag a difficult problem.

[0003] At present, through conventional methods such as dilute acid and soluble calcium-magnesium salt transformation, the valuable metals in the calcium-magnesium slag cannot be effectively recovered. Through the reaction of concentrated acid and calcium-magnesium slag, toxic hydrogen fluoride is generated in the reaction process, polluting the environment and corroding the equipment. In addition, the high-acid valuable metal solution cannot be recovered at low cost, and the calcium and magnesium elements are always circulating in the system, resulting in high treatment cost. By using soluble calcium-magnesium salt transformation, due to the presence of LiNa2AlF6 material, the Li recovery rate is low, the residual lithium content in the slag is high, and it cannot be directly discharged. Therefore, at present, most waste battery recycling enterprises have stored a large amount of calcium-magnesium slag. These calcium-magnesium slag cannot be discarded, and its storage also requires a large amount of space, causing waste of resources. Therefore, how to recover the valuable metals in the calcium-magnesium slag at low cost and without pollution, and solve the problem of calcium-magnesium slag storage, is the focus of research of large enterprises.

[0004] The valuable metal in the calcium-magnesium slag is leached by soluble magnesium salt transformation under acidic conditions in the invention patent application CN109735709A, the leaching solution is separated into nickel, cobalt and manganese and lithium by a precipitant, the nickel, cobalt and manganese slag is prepared into ternary precursor by acid dissolution, calcium and magnesium removal and extraction. The crude lithium solution is prepared into battery-grade lithium carbonate by magnesium removal through alkalization and lithium precipitation by soda. The method realizes the recovery of valuable metals in the calcium-magnesium slag, and the recovery effect is good. However, the process needs to introduce magnesium salt, and the consumption of acid and alkali is large. The calcium and magnesium impurities in the nickel, cobalt and manganese slag acid solution are high, and further calcium and magnesium removal is needed, which produces new calcium-magnesium slag and increases the cost. Moreover, the LiNa2AlF6 in the calcium-magnesium slag is not transformed and recovered.

[0005] The invention patent application CN105838893A realizes the recovery of nickel in the calcium-magnesium slag by transforming the valuable metal fluoride in the calcium-magnesium slag into more difficultly soluble Na3AlF6 by using a mixed solution of aluminum chloride and sodium chloride with a molar ratio of 1:2 as the transformation liquid under acidic conditions, and recycling the transformation for multiple times to obtain a high-concentration nickel chloride solution, and then recovering nickel-iron products or nickel sulfide by iron powder reduction or sodium sulfide precipitation. However, the process needs to introduce aluminum salt and transformation, and the Al, Ca and Mg impurities in the product are high, which reduces the product quality or increases the production cost of the subsequent impurity removal process. Moreover, the process is not suitable for the recovery and treatment of lithium-containing calcium-magnesium slag in the waste battery recycling field.

[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

[0007] Therefore, the present application provides a valuable metal recovery method based on lithium-containing calcium-magnesium slag, which solves the problem of recovering lithium and nickel, cobalt and manganese in lithium-containing calcium-magnesium slag, and ensures simple process, green environmental protection and considerable economic benefits.

[0008] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

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

[0010] 1) mixing the lithium-containing calcium-magnesium slag with an acid solution for acid washing, and obtaining a nickel, cobalt and manganese-containing solution and a lithium-containing acid washing residue after the acid washing is completed;

[0011] 2) mixing the lithium-containing acid washing residue with an acid solution and a soluble sodium salt for sodium salt first transformation, and obtaining a first lithium-containing transformation liquid and a lithium-containing transformation residue;

[0012] 3) mixing the lithium-containing transformation residue with an acid solution and a soluble sodium salt for sodium salt second transformation, and obtaining a second lithium-containing transformation liquid and a transformation residue;

[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 recovering valuable metals such as nickel, cobalt, manganese and lithium.

[0017] Preferably, the mass volume ratio of lithium-calcium-magnesium slag to acid solution in step 1) 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 to 6 mL; the mass volume ratio of the lithium-containing transformation slag to the acid solution in step 3) is 1 g: 4 to 6 mL;

[0020] In step 2), the mass ratio of the soluble sodium salt to the lithium-containing pickling slag is 1 to 4:1; in 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 temperature of the first sodium salt transformation and the second sodium salt transformation are independently ≥90° C., and the reaction time is independently 6 to 8 hours.

[0023] Preferably, the soluble sodium salt in step 2) and step 3) independently comprises 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 neutralization and impurity removal system in step 4) is 7 to 8, and the neutralization and impurity removal time 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 reused in steps 2) and 3).

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

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

[0030] The temperature of the alkaliization and calcium removal reaction is 70-80℃, and the time of the alkaliization and calcium removal reaction is 30-60min.

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

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

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

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

[0035] M(OH)2+2H + ===M 2+ +2H2O(M 2+ represents Ni 2+ , Co 2+ , Mn 2+ )

[0036] The reaction equation of step 2) and step 3) is:

[0037] LiNa2AlF6+Na + ===Na3AlF6+Li +

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

[0039] Ca 2+ +2OH - ===Ca(OH)2↓

[0040] Ca 2+ +CO3 2- ===CaCO3↓

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

[0042] 2Li + +CO3 2-Li2CO3

[0043] Compared with the prior art, the application has the following beneficial effects:

[0044] In the application, the calcium-magnesium slag is first subjected to acid pickling to recover nickel, cobalt and manganese, the recovery rate of Ni and Co is above 98%, and the recovery rate of Mn is above 80%, the acid pickling solution enters a ternary impurity removal extraction system to further recover nickel, cobalt and manganese, the lithium-containing acid pickling slag is further subjected to two sodium salt transformations to recover lithium, the recovery rate of Li is above 99%, the lithium carbonate can be prepared by removing impurities and precipitating lithium from the lithium-containing transformation solution, and the product quality meets the requirements of the battery-grade lithium carbonate (YS / T 582-2013). The application avoids the shortcomings of the traditional soluble calcium-magnesium salt solution transformation to recover valuable metals in the calcium-magnesium slag, which leads to high calcium-magnesium impurity content in the produced transformation solution, complicated subsequent impurity removal procedures and high impurity removal cost, and the method can separate most of the lithium from nickel, cobalt and manganese for recovery, further solves the problems of subsequent separation and high separation cost of the lithium-nickel-cobalt-manganese mixed solution, the recovery rate of lithium is above 99%, and the method has the advantages of simple operation, low energy consumption, green environmental protection, high recovery rate and the like, is suitable for industrial large-scale production, and has good social value and considerable economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only constitute the embodiments of the application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings.

[0046] Figure 1 The XRD graph (Intensity-intensity, degree-degree) of the lithium-containing acid pickling slag obtained in the embodiments 1-4 of the application. DETAILED DESCRIPTION

[0047] The application provides a valuable metal recovery method based on lithium-containing calcium-magnesium slag, which comprises the following steps:

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

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

[0050] 3) mixing the lithium-containing transformation residue with an acid solution and a soluble sodium salt to perform a second sodium salt transformation, and obtaining a second lithium-containing transformation solution and a transformation residue, wherein the main component of the transformation residue is Na3AlF6, and the transformation residue contains a small amount of impurities and can be used as a raw material for preparing cryolite.

[0051] 4) neutralizing and impurity-removing 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 residue, wherein the neutralization and impurity-removing residue is mainly aluminum fluoride and 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 a concentrated residue;

[0053] 6) alkalinizing and calcium-removing the lithium-containing concentrated liquid to obtain a lithium-containing purified liquid and an alkalinizing and calcium-removing residue, wherein the alkalinizing and calcium-removing residue is mainly calcium hydroxide and calcium carbonate and can be used in a defluorination process;

[0054] 7) soda lithium precipitation is performed on the lithium-containing purified liquid to obtain a battery-grade lithium carbonate, and the valuable metals nickel, cobalt, manganese and lithium are recycled.

[0055] In the present application, the mass-volume ratio of the lithium-containing calcium-magnesium residue to the acid liquid in step 1) is 1 g: 1-3 mL, preferably 1 g: 1.5-2.5 mL, and further preferably 1 g: 2 mL.

[0056] In the present application, the temperature of the acid pickling in step 1) is 80-90℃, and specifically can be 82℃, 84℃, 85℃, 86℃, 88℃; and the pH value of the acid pickling is 1-2, and specifically can be 1.2, 1.4, 1.5, 1.6, 1.8.

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

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

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

[0060] In the present application, the reaction temperature of the sodium salt first transformation and the sodium salt second transformation is independently ≥ 90℃, and specifically can be 92℃, 94℃, 95℃, 96℃, 98℃, 100℃; the reaction time is independently 6-8h, and specifically can be 6.2h, 6.4h, 6.5h, 6.8h, 7h, 7.2h, 7.5h, 7.8h.

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

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

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

[0064] In the present application, the neutralization and impurity removal in the step 4) can be performed after mixing the first lithium-containing transformation liquid and the second lithium-containing transformation liquid, or can be performed before mixing the first lithium-containing transformation liquid and the second lithium-containing transformation liquid.

[0065] In the present application, the mass concentration of Li in the lithium-containing concentrated liquid in the step 5) is ≥ 20g / L, and specifically can be 21g / L, 22g / L, 23g / L.

[0066] In the present application, the concentrated residue is a soluble sodium salt, which is reused in the step 2) and the step 3), and still needs to be partially added additionally after reuse.

[0067] In the present application, the alkaliization and calcium removal in the step 6) is performed by adjusting the pH value of the lithium-containing concentrated liquid, then mixing with soda ash to perform alkaliization and calcium removal reaction, and completing the alkaliization and calcium removal.

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

[0069] In the present application, the temperature of the alkali calcium removal reaction is 70-80℃, and specifically can be 72℃, 74℃, 75℃, 76℃, 78℃. The time of the alkali calcium removal reaction is 30-60min, and specifically can be 35min, 40min, 45min, 50min, 55min.

[0070] In the present application, the lithium precipitation with soda ash in step 7) is to mix the lithium-containing purified solution with soda ash or a soda ash solution to perform a lithium precipitation with soda ash reaction, and complete the lithium precipitation with soda ash.

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

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

[0073] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0074] Embodiment 1

[0075] The calcium magnesium slag is mixed with hydrochloric acid solution according to a mass-volume ratio of 1g:2mL to obtain a mixture with a pH of 2, and is pickled at 85°C for 2h to obtain a solution containing nickel, cobalt and manganese and a lithium-containing pickling residue; the obtained lithium-containing pickling residue is slurried with a 7.5% hydrochloric acid solution according to a liquid-solid ratio of 6mL:1g, and then sodium chloride with the same mass as the lithium-containing pickling residue is added for transformation, and the reaction condition is 90°C for 6h; the lithium-containing transformation residue obtained by the first transformation is transformed again by using the above operation, and the recovery rates of lithium and nickel, cobalt and manganese are shown in Table 1. The lithium-containing transformation liquid a and lithium-containing transformation liquid b obtained by the two transformations are mixed, and then sodium hydroxide is added to adjust the pH value to 7.2, and impurities are removed for 1.5h to obtain a removal liquid; the removal liquid is concentrated by evaporation to increase the Li concentration (mass concentration is 20g / L), and the concentrated residue is a soluble sodium salt and is reused. The concentrated liquid is adjusted to pH 12.5 by adding sodium hydroxide, and then 1g:300mL of pure alkali is added to the lithium-containing concentrated liquid, and the mixture is reacted at 80°C for 60min, and then filtered to obtain a lithium-containing purified liquid and an alkaliized calcium removal residue. The lithium-containing purified liquid is heated and added with a 250g / L pure alkali solution with a lithium molar ratio of 1.1 to the lithium-containing purified liquid, and then lithium is precipitated at 95°C for 1.5h, and then centrifuged, washed and dried to obtain lithium carbonate, and the chemical composition of the lithium carbonate is shown in Table 2, and the mass thereof meets the requirements of battery-grade lithium carbonate (YS / T582-2013).

[0076] Example 2

[0077] The calcium magnesium slag is mixed with sulfuric acid solution according to a mass-volume ratio of 1g:1.5mL to obtain a mixture with a pH of 1.5, and is pickled at 80°C for 2h to obtain a solution containing nickel, cobalt and manganese and a lithium-containing pickling residue; the obtained lithium-containing pickling residue is slurried with a 10% sulfuric acid solution according to a liquid-solid ratio of 4mL:1g, and then three times the mass of sodium sulfate of the lithium-containing pickling residue is added for transformation, and the reaction condition is 94°C for 7h; the lithium-containing transformation residue obtained by the first transformation is transformed again by using the above operation, and the recovery rates of lithium and nickel, cobalt and manganese are shown in Table 1. The lithium-containing transformation liquid a and lithium-containing transformation liquid b obtained by the two transformations are mixed, and then sodium hydroxide is added to adjust the pH value to 7.6, and impurities are removed for 2h to obtain a removal liquid; the removal liquid is concentrated by evaporation to increase the Li concentration (mass concentration is 22g / L), and the concentrated residue is a soluble sodium salt and is reused. The concentrated liquid is adjusted to pH 12 by adding sodium hydroxide, and then 1g:300mL of pure alkali is added to the lithium-containing concentrated liquid, and the mixture is reacted at 80°C for 60min, and then filtered to obtain a lithium-containing purified liquid and an alkaliized calcium removal residue. The lithium-containing purified liquid is heated and added with a 230g / L pure alkali solution with a lithium molar ratio of 1.3 to the lithium-containing purified liquid, and then lithium is precipitated at 95°C for 1.5h, and then centrifuged, washed and dried to obtain lithium carbonate, and the chemical composition of the lithium carbonate is shown in Table 2, and the mass thereof meets the requirements of battery-grade lithium carbonate (YS / T582-2013).

[0078] Example 3

[0079] The calcium magnesium slag and nitric acid solution are mixed according to a mass-volume ratio of 1g:2mL to obtain a mixture with a pH of 2, and are pickled at 90°C for 2h to obtain a solution containing nickel, cobalt and manganese and a lithium-containing pickling residue; the obtained lithium-containing pickling residue is slurried with a 13% nitric acid solution according to a liquid-solid ratio of 5mL:1g, and then sodium nitrate is added in an amount of twice the mass of the lithium-containing pickling residue to perform transformation, the reaction conditions being 90°C for 6h, the lithium-containing transformation residue obtained by the first transformation is 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 liquid a and lithium-containing transformation liquid b obtained by the two transformations are mixed, and then sodium hydroxide is added to adjust the pH value to 7.4, and impurities are removed for 1.5h to obtain a removal liquid, the removal liquid is concentrated by evaporation to increase the Li concentration (mass concentration of 20g / L), the concentrated residue is a soluble sodium salt, and is reused. The concentrated liquid is adjusted to a pH of 13 by adding sodium hydroxide, and then pure alkali is added in a mass-volume ratio of 1g:300mL, and the mixture is reacted at 70°C for 60min, and then filtered to obtain a lithium-containing purification liquid and an alkaliized calcium removal residue. The lithium-containing purification liquid is heated and added with a 250g / L pure alkali solution in a lithium molar ratio of 1.5 to the lithium in the lithium-containing purification liquid, and then lithium is precipitated at 95°C for 2h, and then centrifuged, washed and dried to obtain lithium carbonate, the chemical composition of the lithium carbonate is shown in Table 2, and the mass thereof meets the requirements of battery-grade lithium carbonate (YS / T582-2013).

[0080] Example 4

[0081] The calcium magnesium slag and hydrochloric acid solution are mixed according to a mass-volume ratio of 1g:2.5mL to obtain a mixture with a pH of 2, and are pickled at 85°C for 2h to obtain a solution containing nickel, cobalt and manganese and a lithium-containing pickling residue; the obtained lithium-containing pickling residue is slurried with a 12% hydrochloric acid solution according to a liquid-solid ratio of 4mL:1g, and then sodium chloride is added in an amount of three times the mass of the lithium-containing pickling residue to perform transformation, the reaction conditions being 94°C for 8h, the lithium-containing transformation residue obtained by the first transformation is 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 liquid a and lithium-containing transformation liquid b obtained by the two transformations are mixed, and then sodium hydroxide is added to adjust the pH value to 7.8, and impurities are removed for 1h to obtain a removal liquid, the removal liquid is concentrated by evaporation to increase the Li concentration (mass concentration of 23g / L), the concentrated residue is a soluble sodium salt, and is reused. The concentrated liquid is adjusted to a pH of 12.5 by adding potassium hydroxide, and then pure alkali is added in a mass-volume ratio of 1g:300mL, and the mixture is reacted at 70°C for 40min, and then filtered to obtain a lithium-containing purification liquid and an alkaliized calcium removal residue. The lithium-containing purification liquid is heated and added with a 270g / L pure alkali solution in a lithium molar ratio of 1.1 to the lithium in the lithium-containing purification liquid, and then lithium is precipitated at 85°C for 1.5h, and then centrifuged, washed and dried to obtain lithium carbonate, the chemical composition of the lithium carbonate is shown in Table 2, and the mass thereof meets the requirements of battery-grade lithium carbonate (YS / T582-2013).

[0082] Table 1 Recovery rate values of Examples 1-4

[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 of examples 1-4

[0085]

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

[0087] The XRD patterns of the lithium-containing pickling residues obtained from examples 1-4 are shown in Figure 1 (the lithium-containing pickling residues in examples 1-4 are respectively marked as lithium-containing pickling residue-A, lithium-containing pickling residue-B, lithium-containing pickling residue-C, and lithium-containing pickling residue-D). Figure 1 As can be seen from Figure 1, the main component in the pickling residue is LiNa2AlF6, and lithium can be replaced by sodium salt transformation. Figure 1

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

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

Claims

1. A valuable metal recovery method based on lithium-containing calcium-magnesium slag, characterized by, The method comprises the following steps: 1) mixing lithium-containing calcium-magnesium slag with acid solution to perform acid pickling, and obtaining a solution containing nickel, cobalt and manganese and a lithium-containing acid pickling residue after the acid pickling; 2) mixing the lithium-containing acid pickling residue with acid solution and soluble sodium salt to perform sodium salt first transformation, and obtaining first lithium-containing transformation solution and lithium-containing transformation residue; 3) mixing the lithium-containing transformation residue with acid solution and soluble sodium salt to perform sodium salt second transformation, and obtaining second lithium-containing transformation solution and transformation residue; 4) neutralizing and removing impurities from the first lithium-containing transformation solution and the second lithium-containing transformation solution to obtain lithium-containing neutralization and impurity removal solution and neutralization and impurity removal residue; 5) evaporating and concentrating the lithium-containing neutralization and impurity removal solution to obtain lithium-containing concentrated solution and concentrated residue; 6) alkaliizing and removing calcium from the lithium-containing concentrated solution to obtain lithium-containing purified solution and alkaliizing and calcium removal residue; 7) performing soda lithium precipitation on the lithium-containing purified solution to obtain battery-grade lithium carbonate, and realizing recovery of valuable metals nickel, cobalt, manganese and lithium.

2. The method for recovering valuable metals based on lithium-containing calcium-magnesium slag according to claim 1, characterized by, The mass-volume ratio of the lithium-containing calcium-magnesium slag to the acid solution in step 1) is 1g:1-3mL; The temperature of the acid pickling in step 1) is 80-90℃, and the pH value of the acid pickling is 1-2.

3. The method for recovering valuable metals based on lithium-containing calcium-magnesium slag according to claim 1 or 2, characterized in that, The mass-volume ratio of the lithium-containing acid pickling residue to the acid solution in step 2) is 1g:4-6mL, and the mass-volume ratio of the lithium-containing transformation residue to the acid solution in step 3) is 1g:4-6mL; The mass ratio of the soluble sodium salt to the lithium-containing acid pickling residue in step 2) is 1-4:1, and the mass ratio of the soluble sodium salt to the lithium-containing transformation residue in step 3) is 1-4:1; The mass concentration of the acid solution in steps 2) and 3) is independently 5-15%; The reaction temperature of the sodium salt first transformation and the sodium salt second transformation is independently ≥90℃, and the reaction time is independently 6-8h.

4. The method for recovery of valuable metals based on lithium-containing calcium-magnesium slag according to claim 3, characterized in that, The soluble sodium salt in steps 2) and 3) independently comprises one or more of sodium chloride, sodium sulfate and sodium nitrate; The acid solution in steps 1), 2) and 3) independently comprises one or more of sulfuric acid, hydrochloric acid and nitric acid.

5. The method for recovery of valuable metals based on lithium-containing 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 time of the neutralization and impurity removal is 1-2h.

6. The method for recovery of valuable metals based on lithium-containing 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 ≥20g / L; The concentrated residue is a soluble sodium salt, which is recycled to steps 2) and 3).

7. A method for recovery of valuable metals based on lithium-containing calcium-magnesium slag according to any one of claims 4 to 6, characterized in that, The alkaliizing and calcium removal in step 6) is to first adjust the pH value of the lithium-containing concentrated solution, and then mix the lithium-containing concentrated solution with soda to perform alkaliizing and calcium removal reaction to complete the alkaliizing and calcium removal.

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

9. The method according to claim 8, wherein the method is characterized by, The soda lithium precipitation in step 7) is to mix the lithium-containing purified solution with soda or a soda solution to perform soda lithium precipitation reaction to complete the soda lithium precipitation.

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

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