A method for lithium enrichment from low to medium concentration lithium-containing solutions without evaporation

Abstract

The present application belongs to the technical field of resource recycling and reusing, and particularly relates to a method for enriching lithium from a lithium-containing low-concentration solution without evaporation, comprising the following steps: adding a carrier and a carrier activator into the lithium-containing low-concentration solution, and after stirring reaction is completed, solid-liquid separation is performed to obtain a lithium-rich carrier and a lithium-extracted solution; then the lithium-rich carrier is washed with hot water and filtered, water and an elution regenerant are added into the filter cake, and after stirring reaction is completed, solid-liquid separation is performed to obtain a lithium-rich solution with a lithium concentration greater than 10 g / L and a regenerated carrier. The core of the present application is that the present application uses a simpler method than the prior art to realize the enrichment of lithium from a lithium-containing low-concentration solution without evaporation, and the carrier is well recycled and reused, without the need for a complex process, so that the process steps are simplified and the carrier is recycled and reused multiple times.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling and reuse technology, specifically relating to the recycling and reuse of low-concentration lithium-containing solutions for lithium extraction and enrichment, as well as the recycling and reuse of metallic materials. Background Technology

[0002] During lithium carbonate production, solutions with low lithium concentrations (2-3 g / L) are generated. One source is the lithium precipitation solution, which is the solution produced after adding sodium carbonate to a lithium-containing mother liquor (containing 10 g / L of lithium) to precipitate lithium as lithium carbonate. Another source is the low lithium content of the solid raw materials themselves, resulting in a low lithium content in the leachate. The composition of these solutions varies depending on the properties of the raw materials, and they are generally concentrated to a concentration ≥10 g / L. How to recover and reuse this portion of the low-lithium-concentration solution remains to be addressed.

[0003] Currently, solutions with low lithium concentrations are often concentrated by evaporation. This is obviously energy-intensive, and impurities in the solution are concentrated along with the lithium, resulting in a low-purity product obtained from subsequent lithium precipitation. Extraction methods were subsequently developed, using N523 and TBP as extractants to separate lithium from the solution, achieving good purification. However, these extractants are all organic materials, and flammable substances such as sulfonated kerosene are often used as diluents during production, posing stringent safety requirements. Furthermore, since organic matter partially dissolves in the solution system, forming organic wastewater, it increases the difficulty of wastewater treatment. Therefore, current research is more active in the area of ​​inorganic adsorbents. Reported adsorbents include aluminum-based, manganese-based, and titanium-based adsorbents, among others. Aluminum-based adsorbents have achieved large-scale industrial application, while other adsorbents have not yet been widely adopted due to difficulties in preparation, high prices, and high solubility. However, aluminum-based adsorption has a fatal flaw: it only separates lithium and has very limited enrichment capabilities, typically concentrating it from a few hundred milligrams to 1-2 g / L. Further concentration requires evaporation. How to economically and efficiently enrich low- to medium-concentration lithium solutions remains a major challenge for the industry.

[0004] In the prior art, JP2010035617 discloses a method for producing high-concentration lithium solutions from lithium-containing liquids and a method for producing lithium carbonate. Its concentration step uses soluble phosphates such as sodium phosphate to precipitate lithium in the solution (the principle utilizes the low solubility of lithium phosphate to form lithium phosphate precipitate, i.e., Li). + +PO4 3- =Li3PO4), followed by acid dissolution to obtain a high-concentration lithium-containing solution. This method has a significant drawback: during acid dissolution, phosphate ions from the precipitate also enter the solution (the principle includes H+). + +Li3PO4=HPO42- +3Li + ,2H + +Li3PO4=H2PO4 - +3Li + , 3H + +Li3PO4=H3PO4+3Li + This results in low purity of the obtained lithium solution, requiring complex dephosphorization operations to obtain qualified lithium carbonate products. While the method mentions iron phosphate, no specific examples are available, and its actual effectiveness is unknown. To reduce costs, existing technology JP2011168461A optimizes the above method, with two main improvements: firstly, it proposes dephosphorization treatment of the lithium solution obtained after acid dissolution using metal hydroxides (such as iron hydroxide), i.e., adding metal oxides to the obtained acidic lithium solution to precipitate phosphate ions: Fe(OH)3 + 3H+ + +PO4 3- =3H2O+FePO4, thereby purifying the concentrate and improving the purity of subsequent lithium carbonate preparation; secondly, a method for recycling the obtained iron phosphate precipitate is further proposed: that is, decomposing iron phosphate with sodium hydroxide (NaOH+FePO4=Na3PO4+Fe(OH)3), and filtering to obtain a reusable sodium phosphate solution. Obviously, compared with the aforementioned technology JP2010035617, JP2011168461A has indeed made certain improvements, but its disadvantages are still obvious: (1) The entire process requires multiple pH adjustments, the steps are cumbersome, which will greatly increase the overall equipment investment and is not conducive to industrialization; (2) It involves a separate phosphorus decomposition process, which requires an additional washing process, otherwise the actual recycling rate of iron phosphate will be low, increasing the processing cost of the entire process. Therefore, how to achieve high-quality phosphorus recycling while simplifying the process is the key to realizing a low-cost, non-evaporation-free lithium enrichment process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for enriching lithium from low-concentration lithium-containing solutions without evaporation. This invention features a simple process, eliminates the need for organic matter and evaporation concentration, thus avoiding organic pollution and saving energy. Furthermore, the carrier used in this method can be recycled ferric phosphate waste. This method primarily targets lithium-containing solutions with lithium ion concentrations below 10 g / L, and more specifically, lithium-containing solutions with lithium ion concentrations of 1–3 g / L.

[0006] The core innovation of this invention lies in the fact that it uses a simpler method than existing technologies to achieve lithium enrichment from low-concentration lithium solutions without evaporation, while also effectively recycling and reusing the carrier. It does not require complex processes, simplifies process steps, and enables multiple recycling of the carrier.

[0007] To achieve the objective of this invention, the technical solution is as follows: A method for enriching lithium from low-concentration lithium solutions without evaporation includes the following steps: (1) Add a carrier and a carrier activator to a lithium-containing low-concentration solution, control the reaction temperature at 60ºC~100ºC and react for 1~5h. After the reaction is completed, separate the solid and liquid to obtain a lithium-rich carrier and a lithium-extracted liquid. The carrier is an insoluble phosphate and / or iron phosphate waste residue, and the carrier activator is an alkaline substance. The lithium ion concentration in the lithium-containing low-concentration solution is less than 10g / L. The carrier in step (1) includes one or more of iron phosphate waste residue, iron phosphate, aluminum phosphate, calcium phosphate, magnesium phosphate, and their acidic or basic salts. (2) After washing and removing impurities from the obtained lithium-rich carrier, filter it, add water to the obtained filter cake, and then add the carrier desorption and regeneration agent. The carrier desorption and regeneration agent is an acidic substance. Control the reaction temperature at 60ºC~100ºC and react for 1~5h. After the reaction is completed, separate the solid and liquid to obtain the lithium-rich solution and the regenerated carrier.

[0008] Preferably, the carrier in step (1) includes one or more of the following: ferric phosphate residue, ferric phosphate, aluminum phosphate, calcium phosphate, magnesium phosphate, and their acidic or basic salts.

[0009] Preferably, the iron phosphate waste residue is the iron phosphate waste residue generated during the lithium recovery process of lithium iron phosphate.

[0010] Preferably, the carrier activator in step (1) includes one or more of sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide.

[0011] Preferably, the lithium-containing low-concentration solution in step (1) refers to a solution with a lithium concentration range of 1~6 g / L.

[0012] Preferably, the lithium-containing low-concentration solution mentioned in step (1) refers to a lithium-containing solution with a lithium concentration range of 1~3 g / L.

[0013] Preferably, the carrier in step (1) is added at a ratio of 5-200g of carrier per 1L of lithium-containing low-concentration solution. A further preferred ratio is 10-100g of carrier per 1L of lithium-containing low-concentration solution. An even more preferred ratio is 10-50g of carrier per 1L of lithium-containing low-concentration solution.

[0014] Preferably, the carrier activator in step (1) is added at a ratio of 5-400g of alkaline substance required per 1L of lithium-containing low-concentration solution. A further preferred ratio is 10-200g of carrier required per 1L of lithium-containing low-concentration solution. A further preferred ratio is 10-40g of alkaline substance required per 1L of lithium-containing low-concentration solution.

[0015] Preferably, in step (1), the reaction temperature is controlled at 60ºC~100ºC for 1~5 hours. More preferably, in step (1), the reaction temperature is controlled at 60ºC~95ºC for 2~3 hours.

[0016] Preferably, in step (2), the reaction temperature is controlled at 60ºC~100ºC for 1~5 hours. More preferably, in step (2), the reaction temperature is controlled at 80ºC~95ºC for 2~3 hours.

[0017] Preferably, the carrier desorption regenerator in step (2) includes one or more of sulfuric acid, nitric acid, and hydrochloric acid.

[0018] Preferably, the washing and impurity removal in step (2) includes washing multiple times with hot water at a temperature of 40ºC-100ºC. The amount of water used for washing is not specifically required and can be adjusted according to actual conditions.

[0019] Preferably, the water in step (2) is added at a ratio of 1:1 to 5 based on the mass ratio of the filter cake to the water.

[0020] Preferably, the carrier desorption regenerator in step (2) is added at a ratio of m filter cake to m carrier desorption regenerator = 1:0.1~2.

[0021] Preferably, the lithium ion concentration in the lithium-rich solution in step (2) is 10-30 g / L.

[0022] This invention activates the reactivity of a carrier (e.g., an insoluble phosphate) by adding a carrier activator (e.g., an alkaline substance), enabling it to capture lithium in solution. Subsequently, the captured solid phase is analyzed and regenerated (e.g., acid dissolution), causing lithium to precipitate into the liquid phase, thus achieving enrichment. The acid dissolution process is also a carrier regeneration process, therefore, the carrier can be reused.

[0023] Compared with the prior art, the advantages of the present invention are: The method of this invention is simple and easy to operate. It uses a chemical method to replace the traditional evaporation process for lithium concentration, which is different from the traditional high-energy-consuming evaporation concentration method and greatly saves energy.

[0024] The carrier used in this invention is inexpensive and reusable, and does not introduce organic matter during lithium separation. Compared with traditional extraction processes, it does not cause organic pollution.

[0025] During the enrichment process of the method of the present invention, lithium is separated from other alkali metals such as sodium and potassium, as well as from phosphorus, and a high-purity high-lithium solution can be obtained directly.

[0026] The carrier used in this invention is insoluble phosphate, especially iron phosphate, which is readily available. During the lithium recovery process of lithium iron phosphate, iron phosphate waste is generated as waste material. Iron phosphate waste has high purity and contains a large amount of iron ions and phosphate, which can be directly used as a carrier in this invention for utilization and regeneration. Attached Figure Description

[0027] Figure 1 This is a photograph of the regenerated carrier obtained at 40ºC in Example 6; Figure 2 This is a photograph of the regenerated carrier obtained at 80ºC in Example 6. Detailed Implementation

[0028] The detailed structure of the present invention will be further described below with reference to specific embodiments. The insoluble phosphates used in Examples 1-3 of the present invention are commercially available products.

[0029] Example 1 A method for non-evaporative enrichment of lithium from low-concentration lithium solutions involves taking 1 L of a lithium solution containing 2.13 g / L of lithium, adding 20 g of ferric phosphate, stirring until homogeneous, then adding 16 g of sodium hydroxide, controlling the temperature at 80ºC, reacting for 2 h, filtering to obtain a filter cake of 40.94 g (48.7% water content), and determining that the lithium content of the post-lithiation solution is 226 mg / L. Calculations show that, based on a 20 g dry basis, the apparent lithium loading in the carrier reaches 95.2 mg / g. The filter cake is washed three times with hot water at 95°C, then 100 mL of water is added to the filter cake, stirred until homogeneous, and then 8 mL of concentrated sulfuric acid (98% concentration) is added. The reaction continues for 3 h, controlling the reaction temperature at 95ºC. After completion, the solution is filtered to obtain a 14.69 g / L lithium-rich solution and regenerated ferric phosphate.

[0030] Table 1. Comparison of composition between low-concentration lithium-containing solutions and lithium-rich solutions. raw material 2.13g / L 20.54g / L 2.77g / L After enrichment 14.69g / L 0.234 g / L 0.032g / L The regenerated iron phosphate in Example 1 can be reused as a carrier for the next lithium enrichment. After being reused 8 times using the method in Example 1, the apparent lithium loading in the carrier is still >90 mg / g. Example 2

[0031] A method for non-evaporative enrichment of lithium from low-concentration lithium solutions involves taking 1 L of a lithium solution containing 2.21 g / L of lithium, adding 20 g of aluminum phosphate, stirring until homogeneous, then adding 14 g of sodium hydroxide, controlling the temperature at 60ºC, reacting for 2 h, filtering to obtain a filter cake of 42.58 g (54.83% water content), and determining that the lithium content of the extracted solution is 794.9 mg / L. Calculations show that, based on a 20 g dry basis, the apparent lithium loading in the carrier reaches 70.76 mg / g. The filter cake is washed three times with hot water at 80 °C, then 50 mL of water is added to the filter cake, stirred until homogeneous, and then 6 mL of concentrated sulfuric acid (98% concentration) is added. The reaction continues for 2 h, controlling the reaction temperature at 95ºC. After completion, the solution is filtered to obtain a 17.38 g / L lithium-rich solution and regenerated aluminum phosphate.

[0032] Table 2 Comparison of composition between low-concentration lithium-containing solutions and lithium-rich solutions raw material 2.21g / L 11.2 g / L 3.88 g / L After enrichment 17.38g / L 0.325 g / L 0.07 g / L In Example 2, the regenerated aluminum phosphate can be reused as a carrier for the next lithium enrichment. After being reused 8 times using the method in Example 1, the apparent lithium loading in the carrier is still >70 mg / g. Example 3

[0033] A method for non-evaporative enrichment of lithium from low-concentration lithium solutions involves taking 1L of the lithium-containing solution from Example 2, adding 10g of ferric phosphate regenerated from Example 1, and then adding 10g of aluminum phosphate regenerated from Example 2. After stirring evenly, 12g of sodium hydroxide is added, and the temperature is controlled at 90ºC. After reacting for 2 hours, the solution is filtered to obtain a filter cake of 41.24g (50.44% water content). The lithium content of the extracted solution is measured to be 523.3mg / L. Calculations show that, based on a 20g dry basis, the apparent lithium loading in the carrier reaches 84.33mg / g. The filter cake is washed three times with hot water at 95°C. Then, 60mL of water is added to the filter cake, and after stirring to disperse it evenly, 20mL of hydrochloric acid (36% concentration) is added. The reaction continues for 2 hours, with the reaction temperature controlled at 95ºC. After completion, the solution is filtered to obtain a 16.45g / L lithium-rich solution and the regenerated carrier (including ferric phosphate and aluminum phosphate).

[0034] Table 3. Comparison of composition between low-concentration lithium-containing solutions and lithium-rich solutions. raw material 2.21g / L 11.2 g / L 3.88 g / L After enrichment 16.45g / L 0.284 g / L 0.054 g / L Example 4

[0035] Ferric phosphate waste residue is used as the carrier of this invention. The ferric phosphate waste residue is generated during the lithium recovery process from lithium iron phosphate.

[0036] Table 4. Detection results of iron and phosphorus content in ferric phosphate residue. mass percentage 32.456% 18.575% Specific steps: Take 1L of the lithium-containing solution from Example 2, add 18g of the above-mentioned iron phosphate waste residue, stir evenly, add 16g of sodium hydroxide, control the temperature at 90ºC, react for 3h, filter, and obtain 37.13g of filter cake (water content 48.88%). The lithium content of the liquid after lithium extraction is measured to be 276.2mg / L. It can be calculated that, based on 18g dry basis, the apparent lithium loading in the carrier reaches 107.43mg / g. Wash the filter cake three times with hot water at 98℃, then add 51mL of water to the filter cake, stir to disperse evenly, add 9mL of concentrated sulfuric acid (concentration 98%), continue to react for 3h, control the reaction temperature at 95ºC, after completion, filter, and obtain 24.74g / L lithium-rich solution and regenerated carrier.

[0037] Table 5. Comparison of composition between low-concentration lithium-containing solutions and lithium-rich solutions. raw material 2.21g / L 11.2 g / L 3.88 g / L After enrichment 24.74g / L 0.313 g / L 0.032g / L Besides the iron phosphate waste generated during lithium recovery from lithium iron phosphate, other iron phosphate waste can also be used, mainly those with a high content of iron and phosphate ions. The technology for recovering iron phosphate from iron phosphate waste is existing technology and can be recovered using any method in the existing technology. For example, the iron phosphate recovered by the method described in the background patent can be used as the carrier of this invention. Some iron phosphate waste itself has low impurity content and can be directly utilized.

[0038] Example 5: Effect of Load Temperature This embodiment presents a series of experiments to reveal the importance of temperature during the loading process. The specific steps are the same as in Example 1, except that the loading process temperature is controlled at 25ºC, 40ºC, 60ºC, 80ºC, and 95ºC. Table 6 shows that temperature has a significant impact on the concentration process. At low temperatures, especially at 25ºC, the lithium loading is significantly lower than at 95ºC. At 25ºC, not only is the lithium recovery rate low, but the lithium concentration in the subsequent concentrate is also reduced. Furthermore, the lower the loading temperature, the higher the phosphorus concentration in the lithium extraction tail liquid, resulting in greater losses and a greater impact on the performance of the regenerated carrier. Therefore, a loading temperature greater than 60°C is preferable.

[0039] Table 6 Effect of Load Temperature Lithium concentration in lithium extraction tail liquid (mg / L) 713.5 423.3 284.6 226 210.6 Apparent loading (mg / g) 70.83 85.34 92.27 95.2 95.97 Phosphorus concentration in lithium extraction tail liquid (mg / L) 1235.67 773.6 282.7 200.1 192.6 Concentrated lithium concentration (g / L) 10.56 13.11 14.35 14.69 14.84 Example 6: Analysis of the Influence of Temperature This embodiment presents a series of experiments to reveal the importance of the desorption temperature. The specific steps are the same as in Example 1, except that the temperature during the desorption process is controlled at 25ºC, 40ºC, 60ºC, 80ºC, and 95ºC. As shown in Table 7, temperature has a significant impact on the desorption process. Although lithium is enriched at different temperatures, the lower the temperature, the higher the concentration of phosphorus and iron in the concentrate. At 60ºC, the concentrations reach 14.831 g / L and 2.321 g / L, respectively, while at 25ºC, they are as high as 15.945 g / L and 5.013 g / L. The phosphorus concentration is 1200 times higher than at higher temperatures such as 95ºC. The large amount of phosphorus and iron retained in the concentrate leads to two consequences: first, the phosphorus content in the regenerated carrier decreases sharply, resulting in significant performance loss and rendering it unable to function as a carrier; second, the concentrate contains a large amount of phosphorus and iron impurities, failing to achieve the actual separation of lithium.

[0040] like Figure 1 The image shown is of the regenerated carrier obtained at 40ºC. Figure 2 This is an image of the regenerated carrier obtained at 80ºC. It is easy to see that... Figure 1 The regeneration carrier appears deep red due to its high Fe(OH)3 content, while Figure 2 The resulting color is typically grayish-white, characteristic of iron phosphate. The reason for this is that for the carrier regeneration to occur simultaneously during the desorption process, a certain kinetic barrier needs to be overcome to allow phosphate ions to combine with iron ions. Clearly, low and medium temperatures do not meet this condition, preventing effective collisions between phosphate ions and iron ions for efficient regeneration.

[0041] Table 7. Effect of Temperature on Analysis Concentrated lithium concentration (g / L) 14.28 14.48 14.62 14.55 14.69 Phosphorus concentration in concentrated solution (mg / L) 15945 15159 14831 63.52 13.28 Iron concentration in concentrated solution (mg / L) 5013 4055 2312 572 273

[0042] The specific steps are the same as in Example 1, except that iron phosphate (insoluble phosphate) is replaced with sodium phosphate (soluble phosphate). The lithium content of the lithium-extracting solution is measured to be 287 mg / L. After adding water and acid, the lithium phosphate precipitate is completely dissolved. Although lithium ions are enriched, they are not separated from phosphorus. Sodium phosphate cannot be reused, and soluble phosphate cannot play a carrier role in this invention.

[0043] The specific steps are the same as in Example 1, except that no alkaline substance sodium hydroxide is added, the carrier is not activated, the loading reaction cannot be achieved, and lithium ions cannot be enriched.

[0044] The above description is a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for enriching lithium from low-concentration lithium-containing solutions without evaporation, characterized in that: Includes the following steps: (1) Add a carrier and a carrier activator to a lithium-containing low-concentration solution, control the reaction temperature at 60ºC~100ºC and react for 1~5h. After the reaction is completed, separate the solid and liquid to obtain a lithium-rich carrier and a lithium-extracted liquid; the carrier activator is an alkaline substance; the lithium ion concentration in the lithium-containing low-concentration solution is less than 10g / L; the carrier in step (1) includes iron phosphate waste residue or iron phosphate; the alkaline substance includes one or more of sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide; (2) After washing and removing impurities from the obtained lithium-rich carrier, filter it, add water to the obtained filter cake, and then add a carrier desorption and regeneration agent. The carrier desorption and regeneration agent is an acidic substance. Control the reaction temperature at 60ºC~100ºC and react for 1~5 hours. After the reaction is completed, separate the solid and liquid to obtain a lithium-rich solution and a regenerated carrier. The carrier desorption and regeneration agent is added at a mass ratio of m filter cake: m carrier desorption and regeneration agent = 1:0.1~2. The water is added at a mass ratio of m filter cake: m water = 1:1~5. The acidic substance includes one or more of sulfuric acid and hydrochloric acid.

2. The method for enriching lithium from low-concentration lithium-containing solutions without evaporation according to claim 1, characterized in that: The iron phosphate waste residue is the iron phosphate waste residue generated during the lithium recovery process of lithium iron phosphate.

3. The method for non-evaporative enrichment of lithium from low-concentration lithium-containing solutions according to any one of claims 1-2, characterized in that: The lithium-containing low-concentration solution refers to a solution with a lithium concentration range of 1~6 g / L.

4. The method for non-evaporative enrichment of lithium from low-concentration lithium-containing solutions according to any one of claims 1-2, characterized in that: In step (1), the carrier is added at a ratio of 5-200g of carrier required per 1L of low-concentration lithium solution.

5. The method for non-evaporative enrichment of lithium from low-concentration lithium-containing solutions according to any one of claims 1-2, characterized in that: In step (1), the carrier activator is added at a ratio of 5-400g of alkaline substance required for 1L of lithium-containing low-concentration solution.

6. The method for non-evaporative enrichment of lithium from low-concentration lithium-containing solutions according to any one of claims 1-2, characterized in that: The washing and impurity removal in step (2) includes washing multiple times with hot water at a temperature of 40ºC-100ºC.

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