A method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant

Abstract

This invention belongs to the field of hydrometallurgy and chemical separation technology, specifically relating to a method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant, comprising the following steps: (1) dissolving the extractant in a diluent to obtain an organic phase; the extractant is tri-n-octylphosphine oxide, and the diluent is an ionic liquid; (2) mixing the organic phase with strontium-containing brine and extracting under stirring at room temperature, obtaining a mixed solution after extraction; (3) separating the mixed solution by centrifugation to obtain a strontium-loaded organic phase and a raffinate aqueous phase; (4) contacting the strontium-loaded organic phase with a back-extraction agent for back-extraction, collecting the aqueous phase after back-extraction to obtain a strontium solution. The extraction system provided by this invention, using tri-n-octylphosphine oxide (TOPO) as the extractant and the ionic liquid [BMpyr][Tf2N] as the diluent, exhibits significantly superior comprehensive performance compared to existing technologies for the extraction of strontium ions from complex brine.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgy and chemical separation technology, specifically relating to a method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant. Background Technology

[0002] Currently, the main technical approaches for recovering strontium from complex brine systems all have significant limitations: adsorption and membrane separation methods are more suitable for low-concentration solutions, but face bottlenecks such as poor selectivity and susceptibility to interference in high-salinity brines with multiple ions; precipitation methods have the lowest selectivity and are almost unusable. Traditional, mature solvent extraction technologies are mainly applied and researched in the treatment of radioactive waste (such as separating strontium from high-level radioactive wastewater). 90 Sr extraction has not been effectively extended to complex industrial brine applications. Therefore, developing a novel extraction method that can fundamentally adapt to the complex chemical environment of brine, possess high selectivity for strontium ions, strong engineering adaptability, and good economic efficiency has become an independent and urgently needed technological field.

[0003] This invention aims to provide a method specifically designed for the efficient extraction of strontium ions from complex brine systems, addressing a core challenge in this field caused by the lack of applicable technologies. Specifically, this method solves three main problems: First, it fills a technological gap by providing a direct and dedicated strontium extraction process for high-salinity, multi-component industrial brines, overcoming the limitation of existing extraction technologies primarily targeting radioactive wastewater and thus unsuitable for such brines. Second, it overcomes the selectivity bottleneck by achieving highly selective separation and enrichment of strontium ions in the presence of numerous competing ions such as sodium and potassium, thus overcoming the low separation efficiency of existing methods. Third, it ensures engineering feasibility by guaranteeing excellent phase separation performance and operational stability in complex brine environments, avoiding problems such as emulsification and third phase formation, thereby enabling the process to have industrial application potential. Summary of the Invention

[0004] In view of the problems and shortcomings of the existing technology, the purpose of this invention is to provide a method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant, comprising the following steps: (1) The extractant is dissolved in a diluent to obtain an organic phase; the extractant is tri-n-octylphosphine oxide and the diluent is an ionic liquid; (2) The organic phase is mixed with strontium-containing brine and extracted under stirring at room temperature. After extraction, a mixture is obtained. (3) The mixture is centrifuged and then separated to obtain a strontium-loaded organic phase and a raffinate aqueous phase; (4) The strontium-loaded organic phase is contacted with the back-extraction agent for back-extraction. After the back-extraction is completed, the aqueous phase is collected to obtain a strontium solution.

[0006] The structural formula of tri-n-octylphosphine oxide is shown below: Preferably, in step (1), the ionic liquid is a quaternary ammonium salt or quaternary phosphonium salt ionic liquid based on bis(trifluoromethanesulfonyl)imide anion.

[0007] More preferably, in step (1), the diluent is 1-butyl-1-methylpyrrolidine bis(trifluoromethanesulfonyl)imine salt ([BMpyr][Tf2N]). This ionic liquid as a diluent is one of the key features of the present invention. Its function is not only to dissolve TOPO, but also to provide excellent phase separation performance and avoid emulsification.

[0008] The structural formula of 1-butyl-1-methylpyrrolidine bis(trifluoromethanesulfonyl)imine salt is shown below: Preferably, in step (1), the concentration of tri-n-octylphosphine oxide in the organic phase is 0.05 to 0.20 mol / L.

[0009] More preferably, the concentration of tri-n-octylphosphine oxide in the organic phase is 0.10–0.15 mol / L.

[0010] Preferably, in step (2), the pH value of the strontium-containing brine is 5 to 8.

[0011] More preferably, the pH value of the strontium-containing brine is 6.

[0012] Preferably, in step (2), the volume ratio of the organic phase to the strontium-containing brine is (0.25~2):1.

[0013] More preferably, the volume ratio of the organic phase to the strontium-containing brine is 1:1.

[0014] Preferably, in step (2), the extraction time is 5 to 10 minutes.

[0015] Preferably, in step (4), the stripping agent is a hydrochloric acid solution.

[0016] More preferably, the concentration of hydrochloric acid in the hydrochloric acid solution is 0.2 to 0.5 mol / L. Excessive hydrochloric acid concentration may cause equipment corrosion, loss of organic phase, and a significant increase in cost.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The extraction system provided by this invention, using tri-n-octylphosphine oxide (TOPO) as the extractant and ionic liquid [BMpyr][Tf2N] as the diluent, exhibits significantly superior comprehensive performance compared to existing technologies for the extraction of strontium ions from complex brine. The extraction system maintains high and stable extraction efficiency for strontium ions over a wide pH range of 5–8 (extraction rate >90% under preferred conditions). This characteristic allows the method to adapt to pH fluctuations in industrial brines of different sources and compositions without the need for precise and expensive pH pre-adjustment, greatly enhancing the robustness and operational flexibility of the process. More importantly, within this pH range, the system exhibits extremely low co-extraction tendency for alkali metal competing ions such as Na⁺ and K⁺, which are abundant in brine, achieving highly selective separation of the target strontium ions and fundamentally solving the technical bottleneck of selective separation under high salinity conditions.

[0018] (2) This invention uses the ionic liquid [BMpyr][Tf2N] as a diluent. This diluent has moderate interfacial tension with the aqueous phase and excellent compatibility with the TOPO extractant. The resulting organic phase has suitable viscosity and a significantly different density from the aqueous phase. Experiments show that after extraction and mixing, the two phases can separate rapidly and clearly within minutes, with a distinct interface and no stable emulsion layer or third phase formation. This characteristic ensures the feasibility of continuous and stable operation of the extraction process, which is a key guarantee for the industrial application of this method. It solves the problems of traditional extraction systems easily emulsifying due to the "salting out" effect of inorganic salts and the presence of surfactants when processing high-salt brine, leading to difficulties in phase separation and operational instability.

[0019] (3) The TOPO of this invention exhibits good solubility in ionic liquid diluents, forming a uniform and stable organic phase, thus avoiding the loss of active ingredients and pipeline blockage caused by crystallization or precipitation of the extractant. Simultaneously, the TOPO molecular structure is stable, and its phosphonoyl (P=O) functional group is not prone to hydrolysis, degradation, or irreversible structural changes in the mild chemical environment of the ionic liquid and during repeated extraction-back-extraction cycles. Preliminary cycling experiments show that after regeneration by dilute acid back-extraction, the extraction performance of the strontium-loaded organic phase in subsequent cycles does not show significant decline, indicating that the extraction system has good long-term stability and economy, reducing operating costs. Attached Figure Description

[0020] Figure 1 The strontium ion extraction rates of Examples 1-7 of this invention; Figure 2 The strontium ion extraction rates of Examples 8-10 and Example 1 of this invention; Figure 3 The strontium ion extraction rates of Examples 11-14 and Example 1 of this invention; Figure 4The strontium ion extraction rates of Comparative Examples 1, 2, and 1 of this invention are shown. Figure 5 The strontium ion extraction rate of Comparative Examples 3-9 and Example 1 of this invention; Figure 6 The strontium ion extraction rates of Comparative Examples 10-14 of this invention; Figure 7 The extraction rate of strontium ions in the extraction-back-extraction experiment of this invention is shown. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] (I) Effect of different TOPO concentrations on strontium extraction performance To investigate the effect of TOPO concentration in the organic phase on strontium ion extraction rate, Examples 1-7 were conducted in this invention. The specific details of Examples 1-7 are as follows: Example 1: A method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant, the specific steps of which are as follows: (1) TOPO was dissolved in [BMpyr][Tf2N] to obtain an organic phase with a TOPO concentration of 0.1 mol / L; (2) Using a simulated solution with an initial pH of 6 to simulate strontium-containing brine, 3 mL of organic phase was mixed with 3 mL of simulated solution and extracted for 5 minutes under stirring at room temperature to obtain a mixed solution; (3) After centrifugation, the mixture is separated into an organic phase loaded with strontium ions and a raffinate aqueous phase. (4) The organic phase loaded with strontium ions is contacted with a 0.2 mol / L HCl solution for back-extraction. After the back-extraction is completed, the aqueous phase is collected to obtain a strontium solution.

[0023] The method for preparing the simulated liquid is as follows: 1) Weighing: Accurately weigh 0.055g (accurate to 0.001g) of anhydrous strontium chloride and 10.005g (accurate to 0.01g) of sodium chloride using an analytical balance; 2) Dissolving: Add approximately 80 mL of deionized water to a 100 mL beaker. First, add the weighed sodium chloride to the beaker and stir until completely dissolved (sodium chloride dissolves relatively quickly, so stirring may be necessary). Then add the weighed anhydrous strontium chloride and continue stirring until completely dissolved. The solution should be clear and transparent. 3) Volume Adjustment: Carefully transfer the solution from the beaker to a 100 mL volumetric flask along a glass rod. Rinse the beaker and glass rod 2-3 times with a small amount of deionized water, transferring the rinsing solution into the volumetric flask each time. Slowly add water to about 1 cm below the graduation mark on the volumetric flask, then use a dropper to add water dropwise until the lowest point of the meniscus is tangent to the graduation mark. Tighten the stopper and invert the volumetric flask at least 10 times to mix thoroughly. The concentration of strontium ions is 302.5 ppm, and the concentration of sodium ions is 39360 ppm.

[0024] Example 2: The content of Example 2 is basically the same as that of Example 1, except that in step (1), the TOPO concentration is 0.025 mol / L.

[0025] Example 3: The content of Example 3 is basically the same as that of Example 1, except that in step (1), the TOPO concentration is 0.05 mol / L.

[0026] Example 4: The content of Example 4 is basically the same as that of Example 1, except that in step (1), the TOPO concentration is 0.075 mol / L.

[0027] Example 5: The content of Example 5 is basically the same as that of Example 1, except that in step (1), the TOPO concentration is 0.125 mol / L.

[0028] Example 6: The content of Example 6 is basically the same as that of Example 1, except that in step (1), the TOPO concentration is 0.15 mol / L.

[0029] Example 7: The content of Example 7 is basically the same as that of Example 1, except that in step (1), the TOPO concentration is 0.175 mol / L.

[0030] The concentration of strontium ions in the aqueous raffinate of Examples 1-7 was determined, and the strontium ion extraction rate was calculated. The formula for calculating the strontium ion extraction rate is as follows: , In the formula, C0: initial concentration of the aqueous phase before extraction; V0: initial volume of the aqueous phase before extraction; C e : Residual concentration in the aqueous phase after extraction; V e Volume of aqueous phase after extraction.

[0031] The strontium ion extraction rates of Examples 1-7 of this invention were calculated, and the results are shown in the figure. Figure 1 .

[0032] Depend on Figure 1It is evident that the extraction rate of strontium ions increases significantly with increasing TOPO concentration. When the TOPO concentration is below 100 mmol / L, the extraction rate increases rapidly; within the concentration range of 100-150 mmol / L, the extraction rate tends to stabilize, reaching a maximum of over 89%. Considering both extraction efficiency and economics, the preferred TOPO concentration range is 100-150 mmol / L, with the optimal concentration being 100 mmol / L.

[0033] (II) Effect of different pH values ​​on strontium extraction performance To investigate the effect of pH value of strontium-containing brine on strontium ion extraction rate, Examples 8-10 of this invention were conducted. The specific contents of Examples 8-10 are as follows: Example 8: The content of Example 8 is basically the same as that of Example 1, except that in step (2), the pH value of the simulation solution is adjusted to 5 with 0.1 mol / L hydrochloric acid or ammonia solution.

[0034] Example 9: The content of Example 9 is basically the same as that of Example 1, except that in step (2), the pH value of the simulation solution is adjusted to 7 using 0.1 mol / L hydrochloric acid or ammonia solution.

[0035] Example 10: The content of Example 10 is basically the same as that of Example 1, except that in step (2), the pH value of the simulation solution is adjusted to 8 using 0.1 mol / L hydrochloric acid or ammonia solution.

[0036] The concentration of strontium ions in the aqueous raffinate of Examples 8-10 and Example 1 was determined, and the strontium ion extraction rate was calculated. The results are shown in [Figure Number]. Figure 2 .

[0037] Depend on Figure 2 It can be seen that the system of the present invention maintains a high extraction rate of over 80% for strontium ions within a wide pH range of 5 to 8, especially with the extraction rate remaining stable at around 84% between pH 6 and 8. This indicates that the extraction system is not sensitive to changes in the acidity or alkalinity of the aqueous phase, has good adaptability, and does not require precise pH pretreatment of high-salinity brine.

[0038] (III) Effect of the volume ratio (O / A) of organic phase to strontium-containing brine on strontium extraction performance To investigate the effect of the volume ratio of organic phase to strontium-containing brine on the strontium ion extraction rate, Examples 11-14 of this invention were conducted. The specific details of Examples 11-14 are as follows: Example 11: The content of Example 11 is basically the same as that of Example 1, except that in step (2), the volume ratio of the organic phase to the strontium-containing brine is 1:4.

[0039] Example 12: The content of Example 12 is basically the same as that of Example 1, except that in step (2), the volume ratio of the organic phase to the strontium-containing brine is 1:3.

[0040] Example 13: The content of Example 13 is basically the same as that of Example 1, except that in step (2), the volume ratio of the organic phase to the strontium-containing brine is 1:2.

[0041] Example 14: The content of Example 14 is basically the same as that of Example 1, except that in step (2), the volume ratio of the organic phase to the strontium-containing brine is 2:1.

[0042] The concentration of strontium ions in the aqueous raffinate of Examples 11-14 and Example 1 was determined, and the strontium ion extraction rate was calculated. The results are shown in [Figure number missing]. Figure 3 .

[0043] Depend on Figure 3 It can be seen that the single-stage extraction rate of strontium ions gradually increases with the increase of the organic phase ratio. When the volume ratio of organic phase to strontium-containing brine is 1:1, the extraction rate is approximately 86%. The results indicate that the single-stage extraction depth can be effectively controlled by adjusting the ratio to meet the process requirements of different enrichment factors.

[0044] (iv) Effects of different extractants on strontium extraction performance To investigate the effect of different extractants on the extraction rate of strontium ions, Comparative Example 1 and Comparative Example 2 were conducted in this invention. The specific contents of Comparative Example 1 and Comparative Example 2 are as follows: Comparative Example 1: The content of Comparative Example 1 is basically the same as that of Example 1, except that in step (1), the extractant is trialkylphosphine oxide (TRPO, a mixed alkylphosphine oxide).

[0045] Comparative Example 2: The content of Comparative Example 2 is basically the same as that of Example 1, except that in step (1), the extractant is tributylphosphine oxide (TBPO).

[0046] The concentration of strontium ions in the aqueous raffinate of Comparative Examples 1, 2, and 1 was determined, and the strontium ion extraction rate was calculated. The results are shown in [Figure number missing]. Figure 4 .

[0047] Depend on Figure 4It was found that, under the same ionic liquid diluent and operating conditions, the extraction rates of strontium ions using TRPO and TBPO as extractants were significantly lower than those using the TOPO system (for example, the extraction rate of TBPO was less than 40%). This comparative result indicates that not all organophosphorus oxides possess efficient extraction capabilities for strontium ions in ionic liquid systems. The specific long carbon chain (n-octyl) structure in the TOPO molecule and its synergistic effect in [BMpyr][Tf2N] are key to achieving highly selective extraction.

[0048] (v) Effect of different diluents on strontium extraction performance To investigate the effect of different diluents on the strontium ion extraction rate, comparative examples 3-14 were conducted in this invention. The specific details of comparative examples 3-14 are as follows: Example 15: A method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant, the specific steps of which are as follows: (1) TOPO was dissolved in [BMpyr][Tf2N] to obtain an organic phase with a TOPO concentration of 0.052 mol / L; (2) Using a simulated solution with an initial pH of 6 to simulate strontium-containing brine, 3 mL of organic phase was mixed with 3 mL of simulated solution and extracted for 5 minutes under stirring at room temperature to obtain a mixed solution; (3) After centrifugation, the mixture is separated into an organic phase loaded with strontium ions and a raffinate aqueous phase. (4) The organic phase loaded with strontium ions is contacted with a 0.2 mol / L HCl solution for back-extraction. After the back-extraction is completed, the aqueous phase is collected to obtain a strontium solution.

[0049] The method for preparing the simulated liquid is as follows: 1) Weighing: Accurately weigh 0.055g (accurate to 0.001g) of anhydrous strontium chloride and 10.005g (accurate to 0.01g) of sodium chloride using an analytical balance; 2) Dissolving: Add approximately 80 mL of deionized water to a 100 mL beaker. First, add the weighed sodium chloride to the beaker and stir until completely dissolved (sodium chloride dissolves relatively quickly, so stirring may be necessary). Then add the weighed anhydrous strontium chloride and continue stirring until completely dissolved. The solution should be clear and transparent. 3) Volume Adjustment: Carefully transfer the solution from the beaker to a 100 mL volumetric flask along a glass rod. Rinse the beaker and glass rod 2-3 times with a small amount of deionized water, transferring the rinsing solution into the volumetric flask each time. Slowly add water to about 1 cm below the graduation mark on the volumetric flask, then use a dropper to add water dropwise until the lowest point of the meniscus is tangent to the graduation mark. Tighten the stopper and invert the volumetric flask at least 10 times to mix thoroughly. The concentration of strontium ions is 302.5 ppm, and the concentration of sodium ions is 39360 ppm.

[0050] Comparative Example 3: Comparative Example 3 is basically the same as Example 15, except that in step (1), the diluent is [C 12 MIm][Tf2N].

[0051] Comparative Example 4: The content of Comparative Example 4 is basically the same as that of Example 15, except that in step (1), the diluent is [OMIm][Tf2N].

[0052] Comparative Example 5: The content of Comparative Example 5 is basically the same as that of Example 15, except that in step (1), the diluent is [BzMIm][Tf2N].

[0053] Comparative Example 6: The content of Comparative Example 6 is basically the same as that of Example 15, except that in step (1), the diluent is [B4MPy][Tf2N].

[0054] Comparative Example 7: The content of Comparative Example 7 is basically the same as that of Example 15, except that in step (1), the diluent is [BMPy][Tf2N].

[0055] Comparative Example 8: The content of Comparative Example 8 is basically the same as that of Example 1, except that in step (1), the diluent is [AMIm][Tf2N].

[0056] Comparative Example 9: The content of Comparative Example 9 is basically the same as that of Example 15, except that in step (1), the diluent is [BMIm][Tf2N].

[0057] Comparative Example 10: The content of Comparative Example 10 is basically the same as that of Example 15, except that in step (1), the diluent is n-octanol.

[0058] Comparative Example 11: The content of Comparative Example 11 is basically the same as that of Example 15, except that in step (1), the diluent is dichloromethane.

[0059] Comparative Example 12: The content of Comparative Example 12 is basically the same as that of Example 15, except that in step (1), the diluent is n-hexane.

[0060] Comparative Example 13: The content of Comparative Example 13 is basically the same as that of Example 15, except that in step (1), the diluent is ethyl acetate.

[0061] Comparative Example 14: The content of Comparative Example 14 is basically the same as that of Example 15, except that in step (1), the diluent is cyclohexane.

[0062] The concentration of strontium ions in the aqueous raffinate of Comparative Examples 3-14 and Example 15 was determined, and the strontium ion extraction rate was calculated. The results are shown in [Figure number missing]. Figure 5 and Figure 6 .

[0063] from Figure 5 and Figure 6 It can be seen that, compared with organic solvents, ionic liquids, as diluents, significantly enhance the extraction capacity of TOPO for strontium, with effects far superior to traditional molecular solvents such as n-octanol, dichloromethane, and ethyl acetate. This is likely because ionic liquids participate in the extraction mechanism (such as ion exchange), rather than simply physical dissolution. Figure 5 It can be seen that the structure of the cation has a decisive influence on the extraction performance. Under the conditions of this application, the pyrrolidone cation ([BMPyr]) exhibits the best synergistic effect with TOPO, which is most favorable for the selective extraction of strontium. Short-chain ionic liquids are more conducive to strontium extraction. Excessively long alkyl chains (such as C12) may lead to an increase in the viscosity of the ionic liquid or alter the micropolar environment, completely inhibiting the extraction of strontium by TOPO, but having a smaller impact on sodium. This provides a basis for optimizing the structure of ionic liquids to improve extraction efficiency.

[0064] (vi) Cyclic stability performance To investigate the stability of the extraction system of this invention, an extraction-back-extraction cycle experiment was conducted. The specific experimental method is as follows: (1) TOPO was dissolved in [BMpyr][Tf2N] to obtain an organic phase with a TOPO concentration of 0.125 mol / L; (2) Strontium-containing brine was simulated using a simulated solution with an initial pH of ≈6. 3 mL of the organic phase was mixed with 3 mL of the simulated solution and extracted for 5 minutes under stirring at room temperature to obtain a mixed solution. The preparation method of the simulated solution was the same as in Example 1; (3) The mixed solution was centrifuged to separate the strontium-loaded organic phase and the raffinate phase; (4) The strontium-loaded organic phase was contacted with a 0.2 mol / L HCl solution for back-extraction. After back-extraction, the organic phase was collected and mixed with 3 mL of the simulated solution for extraction-back-extraction experiments. This process was repeated 4 times. The strontium ion extraction rate was calculated for each extraction-back-extraction experiment. The calculation results are shown in […]. Figure 7 .

[0065] Depend on Figure 7The cyclic experiments show that the extraction performance of the strontium-loaded organic phase did not significantly decrease after regeneration by dilute acid back-extraction. This is because the TOPO molecule has a stable structure, and its phosphonoacyl (P=O) functional group is not easily hydrolyzed, degraded, or undergoes irreversible structural changes in the mild chemical environment of the ionic liquid and during repeated extraction-back-extraction cycles. This indicates that the extraction system has good long-term stability and economy, reducing operating costs.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention based on the concept of the present invention, without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant, characterized in that, Includes the following steps: (1) The extractant is dissolved in a diluent to obtain an organic phase; the extractant is tri-n-octylphosphine oxide and the diluent is an ionic liquid; (2) The organic phase is mixed with strontium-containing brine and extracted under stirring at room temperature. After extraction, a mixture is obtained. (3) The mixture is centrifuged and then separated to obtain a strontium-loaded organic phase and a raffinate aqueous phase; (4) The strontium-loaded organic phase is contacted with the back-extraction agent for back-extraction. After the back-extraction is completed, the aqueous phase is collected to obtain a strontium solution.

2. The method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant according to claim 1, characterized in that, In step (1), the ionic liquid is a quaternary ammonium salt or quaternary phosphonium salt ionic liquid based on bis(trifluoromethanesulfonyl)imide anion.

3. The method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant according to claim 2, characterized in that, The ionic liquid is 1-butyl-1-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt.

4. The method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant according to claim 1, characterized in that, In step (1), the concentration of tri-n-octylphosphine oxide in the organic phase is 0.05 to 0.20 mol / L.

5. The method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant according to claim 4, characterized in that, The concentration of tri-n-octylphosphine oxide in the organic phase is 0.10–0.15 mol / L.

6. The method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant according to claim 1, characterized in that, In step (2), the pH value of the strontium-containing brine is 5 to 8.

7. The method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant according to claim 1, characterized in that, In step (2), the volume ratio of the organic phase to the strontium-containing brine is (0.25~2):

1.

8. The method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant according to claim 1, characterized in that, In step (4), the stripping agent is a hydrochloric acid solution.

9. The method for extracting strontium ions from brine using tri-n-octylphosphine oxide as an extractant according to claim 8, characterized in that, The concentration of hydrochloric acid in the hydrochloric acid solution is 0.2–0.5 mol / L.

Images