A method for low-base extraction-temperature-controlled pressure stripping of lithium from a lithium-containing solution

Abstract

The application discloses a method for low-alkali extraction-temperature-controlled pressure stripping of lithium from a lithium-containing solution, and belongs to the technical field of hydrometallurgy. The method uses a co-extraction system containing an extraction agent to selectively extract lithium ions from the lithium-containing solution under the condition that the pH is 8-11, removes impurities by washing the lithium-containing solution, and then carries out gas-liquid-liquid three-phase stripping of the lithium-loaded organic phase with an acid gas and an aqueous phase under the condition of temperature control and pressure, the stripping pH is less than 8, and finally, lithium compounds are obtained by removing oil and separating. The application realizes efficient extraction under low-alkali conditions, reduces the alkali consumption, replaces strong acid stripping with an acid gas to avoid equipment corrosion, and makes the stripping efficiency reach more than 99.5% under the condition of temperature control and pressure.

Description

Technical Field

[0001] This invention relates to the fields of hydrometallurgy and lithium resource extraction technology, specifically to a method for lithium extraction from lithium-containing solutions using low-alkali extraction followed by temperature-controlled pressure back-extraction. Background Technology

[0002] Lithium is the lightest metallic element in nature and an important energy metal with wide applications in new energy, aerospace, and nuclear industries. The global demand for lithium resources from the electric vehicle and energy storage industries continues to grow, making the efficient extraction of lithium from lithium-containing solutions of significant economic and strategic importance.

[0003] Solvent extraction is one of the main technical routes for extracting lithium from lithium-containing solutions due to its advantages such as large throughput, high extraction efficiency, excellent selectivity and ease of large-scale operation. However, existing technologies still have many shortcomings.

[0004] Existing technologies mainly suffer from two types of problems: First, the extraction and back-extraction processes for lithium often use strong acid solutions such as hydrochloric acid and sulfuric acid. The excessively high acidity not only increases costs but also generates large amounts of high-salt waste liquid, severely corrodes equipment made of stainless steel and other metals, leading to high equipment costs and safety hazards. CN110656239A discloses an extraction-back-extraction separation and purification method for lithium extraction. This method uses an extraction system containing a composite extractant to extract and separate a lithium-containing solution under pH conditions of 10-13, obtaining a lithium-loaded organic phase. The obtained lithium-loaded organic phase is then subjected to gas-liquid-liquid three-stage back-extraction to obtain a lithium-loaded back-extraction solution. This back-extraction solution is then heat-treated and separated to obtain the lithium product and the separated mother liquor. This method avoids the various problems caused by the use of strong acid solutions in traditional back-extraction processes, and also avoids the cumbersome process of adding sodium carbonate for lithium precipitation, the introduction of sodium salts, and the increased purification difficulty and cost associated with traditional processes. However, to ensure extraction efficiency, this method typically requires strong alkaline conditions (pH=10-13), consuming large amounts of alkaline substances such as sodium hydroxide, resulting in high alkali consumption costs. High alkali consumption not only increases raw material costs but also creates pressure for subsequent wastewater treatment. Secondly, although recent studies have attempted to reduce alkali consumption in the extraction stage and use CO2 for back-extraction in the back-extraction stage to avoid the above problems, CO2 back-extraction stages are mostly conducted at ambient temperature and pressure. While the extraction stage can reduce alkali consumption, its back-extraction yield is too low, thus affecting the overall lithium extraction efficiency and increasing costs, which is detrimental to industrial applications.

[0005] In summary, existing solvent extraction technologies for lithium extraction urgently need breakthroughs in reducing extraction alkali consumption, preventing equipment corrosion, and improving back-extraction yield. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for lithium extraction from lithium-containing solutions using low-alkali extraction followed by temperature-controlled pressure back-extraction. This method can reduce extraction alkali consumption, prevent equipment corrosion, improve back-extraction yield, and reduce production costs.

[0007] This invention provides a method for low-alkali extraction and temperature-controlled pressure back-extraction of lithium from a lithium-containing solution, comprising the following steps: (1) A co-extraction system containing an extractant is used to selectively extract lithium ions from a lithium-containing solution by controlling the pH to 8-11, thereby obtaining a lithium-loaded organic phase. The extractant is one or more of the following: fluoroketone extractants, pyrazolone extractants, a blend of dibenzoylmethane and tributyl phosphate, and β-diketone functionalized ionic liquids. The co-extraction system also includes a co-extractant and a diluent. The co-extractant can be a neutral phosphorus oxide compound (such as tributyl phosphate or trioctylphosphine oxide), and the diluent can be sulfonated kerosene, aviation kerosene, and various organic solvents such as dichloroethane, cyclohexane, benzene, and toluene.

[0008] (2) The lithium-supported organic phase obtained in step (1) is washed with a lithium-containing solution to remove impurity inorganic ions.

[0009] (3) The washed lithium-loaded organic phase, acidic gas and aqueous phase obtained in step (2) are subjected to gas-liquid-liquid three-stage back extraction by controlling temperature, pressurizing and adjusting pH to obtain lithium-loaded back extraction solution.

[0010] (4) The lithium compound is separated from the lithium-containing back-extraction solution obtained in step (3) after oil removal.

[0011] Furthermore, in step (1), the lithium content in the lithium-containing solution is 0.5-30 g / L.

[0012] Furthermore, in step (1), the pH is controlled.

[0013] Furthermore, in step (1), the method of controlling pH is to add an alkaline substance, which is one or more of calcium oxide, sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia, and ammonium carbonate.

[0014] Furthermore, in step (2), the lithium-containing solution is one or more of lithium carbonate solution, lithium chloride solution, lithium sulfate solution, and lithium nitrate solution.

[0015] Furthermore, in step (3), the acidic gas is one or more of carbon dioxide, sulfur dioxide, sulfur trioxide, and hydrogen chloride.

[0016] Furthermore, in step (3), the back-extraction temperature is 0-40℃.

[0017] Furthermore, in step (3), the back-extraction pressure is 0.5-8 MPa.

[0018] Furthermore, in step (3), the back-extraction pH is <8.

[0019] Furthermore, in step (4), the lithium compound is one or more of lithium carbonate, lithium sulfate, and lithium chloride.

[0020] This invention first employs a co-extraction system with a specific extractant. By controlling the pH, lithium ions can be extracted from a lithium-containing solution with low alkalinity to obtain a lithium-loaded organic phase. The lithium-loaded organic phase is then washed with the lithium-containing solution to remove impurity inorganic ions. The washed lithium-loaded organic phase, acidic gas, and aqueous phase are then subjected to gas-liquid-liquid three-stage back-extraction by controlling the temperature, pressure, and pH to obtain a lithium-loaded back-extraction solution. Finally, lithium compounds are separated from the lithium-containing back-extraction solution.

[0021] The beneficial effects of this invention are as follows: First, it significantly reduces extraction alkali consumption. This invention achieves efficient lithium extraction at pH 8-11 by employing a synergistic extraction system with a specific extractant, eliminating the need for large amounts of alkali added to pH 10-13 as in traditional processes, thus reducing alkali usage. Due to the lower pH value, cheaper alkaline substances such as sodium carbonate and ammonia can be used instead of more expensive alkalis like caustic soda, further reducing production costs.

[0022] Secondly, it avoids equipment corrosion caused by strong acids. This invention uses carbon dioxide, sulfur dioxide, sulfur trioxide, or hydrogen chloride gas instead of traditional strong acids (hydrochloric acid, sulfuric acid) for back-extraction, avoiding the corrosion of equipment by strong acids, which helps to extend the service life of equipment and reduce maintenance costs.

[0023] Third, the back-extraction efficiency is high. While reducing the consumption of extraction alkali, this invention utilizes temperature and pressure control and pH control < 8 for back-extraction, which increases the utilization rate of acidic gas. The mixed fluid composed of acidic gas and water fully contacts the lithium-supported organic phase, and the back-extraction efficiency can reach over 99.5%. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process flow for the method of low-alkali extraction and temperature-controlled pressure back-extraction of lithium from lithium-containing solution according to the present invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0026] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field. Example 1

[0027] This embodiment provides a method for lithium extraction from a lithium-containing solution using low-alkali extraction followed by temperature-controlled pressure back-extraction, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps: Using a lithium-containing solution (lithium content 0.5 g / L) as raw material, the organic phase of a co-extraction system of thiophenecarboxyltrifluoroacetone, tributyl phosphate, and sulfonated kerosene was added to an extraction tank and mixed with the lithium-containing solution for extraction. Under the condition of pH=8 of the extraction system, the volume ratio of the organic phase to the aqueous phase was controlled at 1:4. After three stages of extraction, the phases were separated and equilibrium was reached. The lithium extraction rate in this process was 99.68%.

[0028] The lithium-supported organic phase obtained in step (1) was washed with lithium bicarbonate solution (lithium content 7 g / L, pH=9), and the volume ratio of organic phase to aqueous phase was controlled at 30:1. The washing was carried out in 3 stages until equilibrium was reached to complete the washing process.

[0029] The lithium-loaded organic phase obtained in step (2) was fed into the back-extraction tower, and acidic gas CO2 and water were introduced. The pressure was controlled at 8 MPa, the temperature at 0 °C, and the pH of the back-extraction system was 6.5. Gas-liquid-liquid three-dimensional back-extraction was carried out to obtain the lithium-loaded back-extraction solution (lithium content of 6.8 g / L) with a back-extraction yield of 99.75%.

[0030] After removing the oil from the back-extraction solution obtained in step (3), it is pyrolyzed, filtered, and dried to obtain solid lithium carbonate. Example 2

[0031] This embodiment provides a method for lithium extraction from a lithium-containing solution using low-alkali extraction followed by temperature-controlled pressure back-extraction, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps: Using a lithium-containing solution (lithium content 4 g / L) as raw material, the organic phase of a co-extraction system of benzoyltrifluoroacetone, tributyl phosphate, and sulfonated kerosene was added to an extraction tank and mixed with the lithium-containing solution for extraction. Under the condition of pH=10 of the extraction system, the volume ratio of the organic phase to the aqueous phase was controlled at 2:1. After three stages of extraction, the phases were separated and equilibrium was reached. The lithium extraction rate in this process was 99.65%.

[0032] The lithium-supported organic phase obtained in step (1) was washed with lithium sulfate solution (lithium content 7 g / L, pH=7), and the volume ratio of organic phase to aqueous phase was controlled at 30:1. The washing was carried out in 3 stages until equilibrium was reached to complete the washing process.

[0033] The lithium-loaded organic phase obtained in step (2) was fed into the back-extraction tower, and acidic gas SO2 and water were introduced. The pressure was controlled at 0.5 MPa, the temperature at 20 °C, and the pH of the back-extraction system was 5. Gas-liquid-liquid three-dimensional back-extraction was carried out to obtain the lithium-loaded back-extraction solution (lithium content of 25 g / L) with a back-extraction yield of 99.62%.

[0034] After removing the oil from the back-extraction solution obtained in step (3), it is oxidized, evaporated, filtered, and dried to obtain solid lithium sulfate. Example 3

[0035] This embodiment provides a method for lithium extraction from a lithium-containing solution using low-alkali extraction followed by temperature-controlled pressure back-extraction, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps: Using a lithium-containing solution (lithium content 30 g / L) as raw material, a blend of dibenzoylmethane and tributyl phosphate (organic phase), sulfonated kerosene, and the lithium-containing solution were added to an extraction tank for mixing and extraction. Under the condition of pH=11, the volume ratio of the organic phase to the aqueous phase was controlled at 15:1. The extraction was performed in three stages until phase separation equilibrium was reached. The lithium extraction rate was 99.55% during this process.

[0036] The lithium-supported organic phase obtained in step (1) was washed with lithium chloride solution (lithium content 7 g / L, pH=5), and the volume ratio of organic phase to aqueous phase was controlled at 30:1. The washing was carried out in 3 stages until equilibrium was reached to complete the washing.

[0037] The lithium-loaded organic phase obtained in step (2) was fed into the back-extraction tower, and hydrogen chloride gas and water were introduced. The pressure was controlled at 4 MPa, the temperature at 40 °C, and the pH of the back-extraction system was 4. Gas-liquid-liquid three-dimensional back-extraction was carried out to obtain the lithium-loaded back-extraction solution (lithium content of 25 g / L) with a back-extraction yield of 99.51%.

[0038] After removing the oil from the back-extraction solution obtained in step (3), it is evaporated, filtered, and dried to obtain solid lithium chloride.

[0039] Comparative Example 1 Compared with Example 1, this comparative example only replaces pH=8 in step (1) of Example 1 with pH=7.5, while the other steps are the same. In this process, the lithium extraction rate is 94.52%, and the overall lithium extraction efficiency is significantly lower than that of Example 1. It can be seen that when the pH drops below 8, the extraction efficiency is low and the economy is poor.

[0040] Comparative Example 2 Compared with Example 1, this comparative example only replaces pH=8 in step (1) of Example 1 with pH=11.5, while the rest of the steps are the same. The lithium extraction rate is 99.72% in this process, but the alkali consumption is greatly increased compared with Example 1, and the overall production cost increases significantly, which verifies the rationality of controlling the extraction pH in the range of 8-11 in this invention.

[0041] Comparative Example 3 Compared with Example 1, this comparative example only replaces the pressure of 8 MPa in step (3) of Example 1 with 0.2 MPa, while the rest of the steps are the same. The pH of the back-extraction system is 8.5, and the final back-extraction yield is only 68.2%. It can be seen that under the condition of low pressure, the pH of the back-extraction system is >8, and the back-extraction yield is greatly reduced. The pressurization process of the present invention plays a key role in improving the back-extraction yield.

[0042] Comparative Example 4 Compared with Example 1, this comparative example only replaces the pressure of 8MPa in step (3) of Example 1 with 9MPa, while the rest of the steps are the same. The final back-extraction system has a pH of 6.5 and a back-extraction yield of 99.76%. There is no significant difference in pH and yield compared with the back-extraction system of Example 1. However, excessively high pressure requires higher pressure resistance of the equipment, increases the equipment manufacturing cost and operation and maintenance cost, and reduces the overall economic efficiency. This verifies the rationality of controlling the back-extraction pressure in the range of 0.5-8MPa in this invention.

[0043] Comparative Example 5 Compared with Example 1, this comparative example only replaces the temperature of 0°C in step (3) of Example 1 with 45°C. The remaining steps are the same. The final back-extraction system has a pH of 8.3 and a back-extraction yield of only 72.3%. It can be seen that when the temperature exceeds 40°C, the solubility of acidic gas in the aqueous phase decreases and the back-extraction yield decreases significantly.

[0044] Comparative Example 6 Compared with Example 1, this comparative example only replaces the temperature of 0℃ in step (3) of Example 1 with -5℃, and the rest of the steps are the same. The pH of the final back-extraction system is 6.4 and the back-extraction yield is 99.71%, which is not significantly different from the back-extraction result of Example 1. However, too low a temperature will increase the cooling energy consumption, increase the production cost, and reduce the overall economic efficiency, which verifies the rationality of controlling the back-extraction temperature in the range of 0-40℃ in this invention.

[0045] Although embodiments of the present invention have been shown and described above, it is understood that these embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and alterations to the above embodiments within the scope of the present invention without departing from its principles and spirit. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. A method for lithium extraction from a lithium-containing solution using low-alkali extraction-temperature-controlled pressure back-extraction, characterized in that, Includes the following steps: (1) A co-extraction system containing an extractant is used to selectively extract lithium ions from a lithium-containing solution by controlling the pH to 8-11, thereby obtaining a lithium-loaded organic phase; the extractant is one or more of fluoroketone extractants, pyrazolone extractants, a blend of dibenzoylmethane and tributyl phosphate, and β-diketone functionalized ionic liquids; the co-extraction system also includes a co-extractant and a diluent; (2) The lithium-supported organic phase obtained in step (1) is washed with a lithium-containing solution to remove impurity inorganic ions; (3) The washed lithium-loaded organic phase, acidic gas and aqueous phase obtained in step (2) are subjected to gas-liquid-liquid three-stage back extraction by controlling temperature, pressurizing and adjusting pH to obtain lithium-loaded back extraction solution; (4) The lithium compound is separated from the lithium-containing back-extraction solution obtained in step (3) after oil removal.

2. The method according to claim 1, characterized in that: In step (1), the lithium content in the lithium-containing solution is 0.5-30 g / L.

3. The method according to claim 1, characterized in that: In step (1), the method of controlling pH is to add an alkaline substance, which is one or more of calcium oxide, sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia, and ammonium carbonate.

4. The method according to claim 1, characterized in that: The fluoroketone extractant is thiophenecarboxylic acid trifluoroacetone or benzoyltrifluoroacetone.

5. The method according to claim 1, characterized in that: In step (2), the lithium-containing solution is one or more of lithium carbonate solution, lithium chloride solution, lithium sulfate solution, and lithium nitrate solution.

6. The method according to claim 1, characterized in that: In step (3), the acidic gas is one or more of carbon dioxide, sulfur dioxide, sulfur trioxide, and hydrogen chloride.

7. The method according to claim 1, characterized in that: In step (3), the back-extraction temperature is 0-40℃.

8. The method according to claim 1, characterized in that: In step (3), the back-extraction pressure is 0.5-8 MPa.

9. The method according to claim 1, characterized in that: In step (3), the back-extraction pH is <8.

10. The method according to claim 1, characterized in that: In step (4), the lithium compound is one or more of lithium carbonate, lithium sulfate, and lithium chloride.

Images