Method for extracting, recovering and extracting lithium under carbonate system

Abstract

The invention provides a method for extracting, recovering and extracting lithium under a carbonate system, which comprises the following steps of: filtering lithium precipitation mother liquor to remove large-particle impurities; carrying out extraction treatment on the filtered lithium precipitation mother liquor to obtain a lithium extraction organic phase; carrying out reverse extraction treatment on the lithium extraction organic phase by adopting a reverse extraction agent to obtain a high-lithium mixed solution; adjusting the pH value of the high-lithium mixed solution to 7-10, and removing impurities through ion exchange resin to obtain a high-lithium solution; according to the method disclosed by the invention, the lithium precipitation mother liquor is subjected to extraction and reverse extraction, and then is subjected to ion exchange to remove calcium and magnesium impurities, so that calcium and magnesium exist in the form of free ions, and the impurities are effectively removed.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction, and particularly to a method for extracting and recovering lithium by extraction in a carbonate system. Background Art

[0002] During the process of lithium precipitation in lithium carbonate production, a large amount of mother liquor is generated. Part of the lithium is dissolved in the mother liquor, and at the same time, due to impurity ions brought by industrial soda ash, there are trace amounts of impurity ions such as calcium and magnesium in the mother liquor for lithium precipitation; currently, the following methods are mainly used for treating the mother liquor for lithium precipitation in industry: (1) Acidification - evaporation concentration - re - precipitation method: After acidification and multiple evaporation concentrations, sodium carbonate is added for secondary lithium precipitation, but there are problems such as large acid consumption, high energy consumption, low lithium recovery rate, and impurity enrichment; (2) Solvent extraction method: Organic extractants such as organophosphorus are used to selectively extract lithium, but in the process of recovering lithium using the extraction method, calcium and magnesium impurities are important factors affecting the quality of high - lithium liquid; (3) Ion exchange method: Manganese - based or titanium - based ion sieves are often used to adsorb lithium, but the adsorption capacity is easily affected by high - concentration competitive ions such as sodium ions in the mother liquor, and a large amount of acid - base wastewater is generated during the resin regeneration process; (4) Membrane separation technology: Such as the combination process of nanofiltration membrane salt separation - reverse osmosis concentration, but it faces technical bottlenecks such as serious membrane fouling, high investment, and high operating costs.

[0003] The existing technologies generally have the following problems: 1) The process flow is complex, the treatment cycle is long, and the equipment investment is large; 2) It is difficult to achieve both high lithium recovery rate and product purity, and the impurity separation efficiency is low; 3) The consumption of chemical reagents is large, the treatment of by - products is difficult, and it is easy to cause secondary pollution; 4) The adaptability to the fluctuation of the mother liquor composition is poor, and the process stability is insufficient.

[0004] Therefore, developing an efficient and environmentally friendly method for extracting lithium and separating impurities from the mother liquor for lithium precipitation has important industrial application value for realizing the high - value utilization of lithium resources and reducing the production cost of lithium carbonate. Summary of the Invention

[0005] In view of the above - mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for extracting and recovering lithium by extraction in a carbonate system, which is used to solve the problem that calcium and magnesium impurities in the existing mother liquor for lithium precipitation cannot be effectively removed.

[0006] Since the mother liquor for lithium precipitation is overall weakly alkaline, calcium and magnesium impurity ions form water - soluble basic salts with carbonate and bicarbonate, and the effective removal of calcium and magnesium impurities in the mother liquor for lithium precipitation cannot be achieved through the resin ion - exchange process.

[0007] To achieve the above - mentioned purpose and other related purposes, the present invention provides a method for extracting and recovering lithium by extraction in a carbonate system, including the following steps:

[0008] S1. Filter the mother liquor for lithium precipitation to remove large - particle impurities;

[0009] S2. Use an organic extractant to extract the lithium-precipitated mother liquor after the treatment in step S1 to obtain a lithium-loaded organic phase and a raffinate solution;

[0010] S3. Use a stripping agent to strip the lithium-loaded organic phase to obtain a high-lithium mixed solution;

[0011] S4. Adjust the pH of the high-lithium mixed solution to 7 - 10, and remove impurities through an ion exchange resin to obtain a high-lithium solution.

[0012] Preferably, the lithium-precipitated mother liquor is the solution after lithium precipitation using industrial soda ash; the lithium ion concentration in the lithium-precipitated mother liquor is 1.2 - 2.5 g / L, the sodium ion concentration is 30 - 60 g / L, the chloride ion concentration is 50 - 90 g / L, the carbonate ion concentration is 7 - 12 g / L, the calcium ion and magnesium ion concentration is 1 - 100 ppm, and the pH is 9.5 - 14.

[0013] Preferably, in step S1, the filtration is carried out using a plate and frame filter press.

[0014] Preferably, in step S1, the temperature of the lithium-precipitated mother liquor is 15 - 40 °C.

[0015] Preferably, in step S2, the flow rate ratio of the organic extractant to the lithium-precipitated mother liquor is 0.8 - 1.2:0.8 - 1.

[0016] Preferably, in step S3, the stripping agent is selected from one or more of hydrochloric acid, sulfuric acid, and nitric acid dilution solutions, and the [H + concentration range is 3 - 6 mol / L.

[0017] Preferably, the flow rate ratio of the stripping agent to the lithium-loaded organic phase is 1 - 2:10 - 20.

[0018] Preferably, after the stripping treatment in step S3, a stripped organic phase is also obtained, and the stripped organic phase is suitable for recycling to the extraction treatment step in step S2.

[0019] Preferably, in step S4, one or more of sodium hydroxide, lithium hydroxide, and potassium hydroxide solutions are used to adjust the pH value.

[0020] Preferably, in step S4, the ion exchange resin is an aminomethylphosphonic acid-based chelating resin.

[0021] Preferably, after the ion exchange resin in step S4 is saturated in adsorption, it is regenerated by acid for recycling.

[0022] As described above, the method for extracting and recovering lithium by extraction under a carbonate system of the present invention has the following beneficial effects:

[0023] The method for extracting and recovering lithium in a carbonate system according to the present invention separates carbonate through preliminary extraction and stripping, avoiding the phenomenon of resin "penetration", and making calcium and magnesium ions exist in the form of free ions. Then, ion exchange resin is used to remove calcium and magnesium impurity ions, solving the problems of resin blockage and ineffective removal of calcium and magnesium impurities in the prior art, improving the separation efficiency of calcium and magnesium, and further improving the quality of the prepared lithium salt products. Brief Description of the Drawings

[0024] Figure 1 It is a process flow chart for separating calcium and magnesium in the lithium precipitation mother liquor for lithium extraction according to the present invention. Detailed Embodiments

[0025] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0026] When a numerical range is disclosed herein, the above range is considered continuous and includes the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein. For example, the specified range from "1 to 10" should be considered to include any and all sub-ranges between the minimum value 1 and the maximum value 10. Exemplary sub-ranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0027] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combined steps or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; moreover, unless otherwise specified, the numbers of the method steps are only convenient tools for identifying the method steps, rather than limiting the arrangement order of the method steps or the scope in which the present invention can be implemented. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope in which the present invention can be implemented.

[0028] In this industry, the extraction method for lithium extraction from salt lake brine generally adopts the process of adsorption first and then extraction. For details, please refer to CN116024440B. Since calcium and magnesium ions are preferentially extracted by the extractant over lithium ions, occupying the extraction positions, the extraction efficiency decreases. Therefore, the process of adsorption first and then extraction, or the process of separating calcium and magnesium by membrane method first and then extraction, is generally used for lithium extraction from salt lakes by extraction method (for details, please refer to CN117658281A. This method is only applicable to the case of high impurity content and cannot effectively remove impurities when the impurity content is low).

[0029] However, due to the different environmental system of the carbonate system, the overall alkalinity of the mother liquor for lithium precipitation is relatively high. Under the condition of high alkalinity, the solubility of calcium carbonate is lower than that of calcium hydroxide, resulting in difficulty for the adsorption resin to adsorb and separate calcium ions in the mother liquor for lithium precipitation.

[0030] The present invention provides a method for extracting and recovering lithium under a carbonate system, comprising the following steps:

[0031] S1. Filter the mother liquor for lithium precipitation to remove large particle impurities;

[0032] S2. Extract the mother liquor for lithium precipitation processed in step S1 with an organic extractant to obtain a lithium-loaded organic phase and a raffinate solution;

[0033] S3. Back-extract the lithium-loaded organic phase with a back-extractant to obtain a high-lithium mixed solution;

[0034] S4. Adjust the pH of the high-lithium mixed solution to 7-10, 7-8, 8-9 or 9-10, and remove impurities through an ion exchange resin to obtain a high-lithium solution.

[0035] In the method for extracting and recovering lithium under a carbonate system of the present invention, the mother liquor for lithium precipitation is the solution after precipitating lithium with industrial soda ash; the lithium ion concentration in the mother liquor for lithium precipitation is 1.2-2.5 g / L, 1.2-1.5 g / L, 1.5-2.0 g / L or 2.0-2.5 g / L, the sodium ion concentration is 30-60 g / L, 30-40 g / L, 40-50 g / L or 50-60 g / L, the chloride ion concentration is 50-90 g / L, 50-60 g / L, 60-70 g / L, 70-80 g / L or 80-90 g / L, the carbonate ion concentration is 7-12 g / L, 7-8 g / L, 8-9 g / L, 9-10 g / L, 10-11 g / L or 11-12 g / L, the calcium and magnesium ion concentrations are both 1-100 ppm, 1-20 ppm, 20-40 ppm, 40-60 ppm, 60-80 ppm or 80-100 ppm, and the pH is 9.5-14, 9.5-10, 10-11, 11-12, 12-13, 13-14, etc.

[0036] Among them, when the lithium precipitation mother liquor has a relatively high alkalinity, acid can be added to reduce the alkalinity to avoid emulsification of the extractant.

[0037] In the method for extracting and recovering lithium under a carbonate system according to the present invention, the filtration described in step S1 is carried out using a plate and frame filter press.

[0038] Furthermore, the pore size of the filter cloth of the plate and frame filter press is 800 - 1200 mesh, 800 - 900 mesh, 900 - 1000 mesh, 1000 - 1100 mesh or 1100 - 1200 mesh. Large particle impurities in the mother liquor are removed by filtration separation.

[0039] In the method for extracting and recovering lithium under a carbonate system according to the present invention, the temperature of the lithium precipitation mother liquor in step S1 is 15 - 40 °C. For example, it is 15 - 20 °C, 20 - 25 °C, 25 - 30 °C, 30 - 35 °C or 35 - 40 °C.

[0040] In the method for extracting and recovering lithium under a carbonate system according to the present invention, the volume ratio of the organic extractant to the lithium precipitation mother liquor in step S2 is 0.8 - 1.2:0.8 - 1. For example, it is 0.8 - 0.9:0.8 - 1, 0.9 - 1.0:0.8 - 1, 1.0 - 1.1:0.8 - 1, 1.1 - 1.2:0.8 - 1, 1 - 1.2:0.8 - 0.9 or 1 - 1.2:0.9 - 1. The present invention does not make specific limitations on the organic extractant, and those skilled in the art can select according to the actual situation as long as the extraction of lithium in the lithium precipitation mother liquor can be achieved. In the examples and comparative examples of the present invention, the extractant is selected from the components disclosed in Example 1 of Publication No. CN 118241039 A.

[0041] In the method for extracting and recovering lithium under a carbonate system according to the present invention, the stripping agent in step S3 is selected from one or more of hydrochloric acid, sulfuric acid, and nitric acid dilution solutions, and the [H + concentration range is 3 - 6 mol / L. For example, it is 3 - 4 mol / L, 4 - 5 mol / L or 5 - 6 mol / L.

[0042] The stripping agent can be prepared from concentrated acid and pure water.

[0043] In the method for extracting and recovering lithium under a carbonate system according to the present invention, the volume ratio of the stripping agent to the lithium - extracting organic phase is 1 - 2:10 - 20. For example, it is 1 - 1.5:10 - 20, 1.5 - 2:10 - 20, 1 - 2:10 - 12, 1 - 2:12 - 14, 1 - 2:14 - 16, 1 - 2:16 - 18 or 1 - 2:18 - 20.

[0044] In the method for extracting and recovering lithium in a carbonate system according to the present invention, after the back-extraction treatment in step S3, a back-extracted organic phase is also obtained, and the back-extracted organic phase is suitable for being recycled and used in the extraction treatment step of step S2.

[0045] In the method for extracting and recovering lithium in a carbonate system according to the present invention, in step S4, one or more of sodium hydroxide, lithium hydroxide, and potassium hydroxide solutions are used to adjust the pH value.

[0046] In the method for extracting and recovering lithium in a carbonate system according to the present invention, the ion exchange resin in step S4 is an aminomethylphosphonic acid-based chelating resin.

[0047] In the method for extracting and recovering lithium in a carbonate system according to the present invention, after the ion exchange resin in step S4 is saturated in adsorption, it is regenerated by an acid for recycling.

[0048] Further, the acid regeneration of the ion exchange resin in step S4 uses one of hydrochloric acid, sulfuric acid, and nitric acid dilution solutions, with the [H + concentration range of 1 - 1.5 mol / L. For example, it can be 1 - 1.1 mol / L, 1.1 - 1.2 mol / L, 1.2 - 1.3 mol / L, 1.3 - 1.4 mol / L, or 1.4 - 1.5 mol / L.

[0049] Example 1

[0050] A method for extracting and recovering lithium in a carbonate system, as Figure 1 shown, in the lithium precipitation mother liquor, the lithium ion content is 1.55 g / L, the sodium ion content is 46.7 g / L, the chloride ion content is 70.2 g / L, the carbonate content is 6.8 g / L, the calcium ion content is 12 ppm, the magnesium ion content is 23 ppm, and the pH is 10.2; the method includes the following steps:

[0051] S1. Filter the lithium precipitation mother liquor through a plate and frame filter press to remove large particle impurities;

[0052] S2. Perform extraction treatment on the lithium precipitation mother liquor after the treatment in step S1, where the mother liquor flow rate is 20 m 3 / h, and the organic extractant flow rate is 18 m 3 / h, to obtain a lithium-extracted organic phase and a raffinate solution;

[0053] S3. Perform back-extraction treatment on the lithium-extracted organic phase with a back-extraction agent, where the [H + is 5 mol / L and the flow rate is 0.85 m 3 / h; obtain a high-lithium mixed solution with a pH of 4.5, where the lithium ion concentration is 35.8 g / L, the sodium ion concentration is 6.55 g / L, the calcium ion concentration is 0.28 g / L, the magnesium ion concentration is 0.53 g / L, and the lithium extraction yield is 98.16%;

[0054] S4. Adjust the pH of the high-lithium mixed solution to 8.5 with 32 wt% lye at a temperature of 26°C; obtain a high-lithium solution by impurity removal through ion exchange resin, with a calcium ion content of 0.6 ppm and a magnesium ion content of 0.2 ppm. The comprehensive lithium recovery rate after impurity removal is 97.82%.

[0055] Example 2

[0056] A method for extracting and recovering lithium under a carbonate system. In the lithium precipitation mother liquor, the lithium ion content is 1.82 g / L, the sodium ion content is 55.3 g / L, the chloride ion content is 85.2 g / L, the carbonate ion content is 7.88 g / L, the calcium ion content is 5 ppm, the magnesium ion content is 11 ppm, and the pH is 11.3. The method includes the following steps:

[0057] S1. Filter the lithium precipitation mother liquor through a plate and frame filter press to remove large particle impurities.

[0058] S2. Perform extraction treatment on the lithium precipitation mother liquor after the treatment in step S1. The flow rate of the mother liquor is 35 m 3 / h, and the flow rate of the organic extractant is 30 m 3 / h to obtain a lithium-loaded organic phase and a raffinate solution.

[0059] S3. Perform stripping treatment on the lithium-loaded organic phase with a stripping agent. The stripping agent [H + is 4.5 mol / L, and the flow rate is 2.05 m 3 / h; obtain a high-lithium mixed solution with a pH of 3.5, where the lithium ion concentration is 29.2 g / L, the sodium ion concentration is 5.12 g / L, the calcium ion concentration is 0.082 g / L, the magnesium ion concentration is 0.185 g / L, and the lithium extraction recovery rate is 93.97%.

[0060] S4. Adjust the pH of the high-lithium mixed solution to 7.5 with 32 wt% lye at a temperature of 20°C; obtain a high-lithium solution by impurity removal through ion exchange resin, with a calcium ion content of 1.3 ppm and a magnesium ion content of 0.3 ppm. The comprehensive lithium recovery rate after impurity removal is 93.28%.

[0061] Example 3

[0062] A method for extracting and recovering lithium under a carbonate system. In the lithium precipitation mother liquor, the lithium ion content is 1.28 g / L, the sodium ion content is 52.3 g / L, the chloride ion content is 81.6 g / L, the carbonate ion content is 5.34 g / L, the calcium ion content is 2 ppm, the magnesium ion content is 14 ppm, and the pH is 9.8. The method includes the following steps:

[0063] S1. Filter the lithium precipitation mother liquor through a plate and frame filter press to remove large particle impurities.

[0064] S2, extract the lithium precipitate mother liquor after step S1, wherein the mother liquor flow rate is 42m 3 / h, the organic extractant flow rate is 28m 3 / h, to obtain a lithium-extracted organic phase and a raffinate solution;

[0065] S3, using a stripping agent to strip the lithium organic phase, wherein the stripping agent [H + ]6mol / L, flow rate 1.28m 3 / h; the high lithium mixed solution pH is 3.0, wherein the lithium ion concentration is 38.9g / L, the sodium ion concentration is 8.76g / L, the calcium ion concentration is 0.061g / L, the magnesium ion concentration is 0.446g / L, and the extraction lithium yield is 92.62%;

[0066] S4. Using 32wt% alkali solution to adjust the pH of the high-lithium mixed solution to 9.5 and the temperature to 32°C; removing impurities through ion exchange resin to obtain a high-lithium solution, wherein the calcium ion content is 0.3ppm, the magnesium ion content is 0.1ppm, and the comprehensive lithium yield after impurity removal is 91.78%.

[0067] Comparative Example 1

[0068] Comparative Example 1 is different from Example 1 in that the method is as follows: first, ion exchange resin is used for adsorption and impurity removal, then an organic extractant is used for extraction, and a stripping agent is used for stripping treatment. The mother liquor flow rate, organic extractant flow rate, stripping agent flow rate and temperature conditions are the same as those in Example 1. The calcium ion content in the high lithium solution is 232ppm, the magnesium ion content is 412ppm, and the comprehensive lithium yield is 97.06%.

[0069] Comparative Example 2

[0070] Comparative Example 2 Compared with Example 1, the pH of the high-lithium mixed solution in step S4 is not adjusted, and the impurities are directly removed by ion exchange resin; the other conditions are the same as those in Example 1. The calcium ion content of the obtained high-lithium solution is 55ppm, the magnesium ion content is 102ppm, and the comprehensive lithium yield after impurity removal is 97.65%.

[0071] By comparing Example 1 and Comparative Example 1, it can be seen that under a relatively high alkaline environment, at the same alkaline pH value, since the solubility of calcium carbonate is lower than that of calcium hydroxide and there are more carbonate ions in the system, the resin is easily blocked. The present invention separates carbonate by extraction and stripping in the early stage during the adsorption process, thereby avoiding the phenomenon of "penetration" of the resin and improving the separation efficiency of calcium and magnesium.

[0072] By comparing Example 1 and Comparative Example 2, it can be seen that since the high-lithium solution obtained by stripping is acidic, calcium and magnesium ions cannot be effectively adsorbed by the adsorption resin, and the separation effect of calcium and magnesium impurities is poor.

[0073] In summary, through the process of lithium extraction and impurity removal from the mother liquor after lithium precipitation, the present invention effectively removes calcium and magnesium ions, obtaining a high-purity high-lithium solution, which can meet the production of battery-grade lithium carbonate. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0074] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for extracting and recovering lithium in a carbonate system, characterized in that, It includes the following steps: S1. Filter the lithium precipitation mother liquor to remove large particle impurities; S2. Extract the lithium precipitation mother liquor processed in step S1 with an organic extractant to obtain a lithium-loaded organic phase and a raffinate solution; S3. Back-extract the lithium-loaded organic phase with a back-extractant to obtain a high-lithium mixed solution; S4. Adjust the pH of the high-lithium mixed solution to 7 - 10, and remove impurities through an ion exchange resin to obtain a high-lithium solution.

2. The method for extracting and recovering lithium by extraction under a carbonate system according to claim 1, characterized in that The lithium precipitation mother liquor is the solution after lithium precipitation with industrial soda ash; the lithium ion concentration in the lithium precipitation mother liquor is 1.2 - 2.5 g / L, the sodium ion concentration is 30 - 60 g / L, the chloride ion concentration is 50 - 90 g / L, the carbonate ion concentration is 7 - 12 g / L, the calcium ion and magnesium ion concentration is 1 - 100 ppm, and the pH is 9.5 - 14.

3. The method for extracting and recovering lithium by extraction under a carbonate system according to claim 1, wherein, In step S1, the filtration is carried out using a plate and frame filter press.

4. The method for extracting and recovering lithium in a carbonate system according to claim 3, wherein The filter cloth aperture of the plate and frame filter press is 800 - 1200 mesh.

5. The method for extracting and recovering lithium by extraction under a carbonate system according to claim 1, wherein In step S1, the temperature of the lithium precipitation mother liquor is 15 - 40 °C.

6. The method for extracting and recovering lithium in a carbonate system according to claim 1, characterized in that, In step S2, the flow rate ratio of the organic extractant to the lithium precipitation mother liquor is 0.8 - 1.2:0.8 - 1.

7. The method for extracting and recovering lithium by extraction under a carbonate system according to claim 1, characterized in that, The stripping agent described in step S3 is selected from one or more of hydrochloric acid, sulfuric acid, and nitric acid dilution solutions, and the concentration range of [H + is 3-6 mol / L.

8. The method for extracting and recovering lithium in a carbonate system according to claim 1, characterized in that, The flow rate ratio of the back-extractant to the lithium-loaded organic phase is 1 - 2:10 - 20.

9. The method for extracting and recovering lithium by extraction under a carbonate system according to claim 1, characterized in that, After the back-extraction treatment in step S3, a back-extracted organic phase is also obtained, and the back-extracted organic phase is suitable for recycling in the extraction treatment step of step S2.

10. The method for extracting and recovering lithium in a carbonate system according to claim 1, characterized in that, In step S4, the pH value is adjusted using one or more of sodium hydroxide, lithium hydroxide, and potassium hydroxide solutions.

11. The method for extracting and recovering lithium in a carbonate system according to claim 1, characterized in that, In step S4, the ion exchange resin is an aminomethylphosphonic acid-based chelating resin.

12. The method for extracting and recovering lithium in a carbonate system according to claim 1, wherein After the ion exchange resin in step S4 is saturated in adsorption, it is regenerated with acid for recycling.

13. The method for extracting and recovering lithium by extraction under a carbonate system according to claim 12, wherein In step S4, the acid regeneration of the ion exchange resin uses one of hydrochloric acid, sulfuric acid, and nitric acid dilution solutions, and the [H + concentration range is 1-1.5 mol / L.

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