Preparation of polysulfone / zeolitic imidazolate framework blended base membrane@ copper ferrocyanide composite membrane and its application in separation of rubidium from salt lake brine

Abstract

This invention discloses the preparation of a polysulfone / zeolite imidazole salt framework blend membrane@copper ferrocyanide composite membrane and its application in rubidium separation in salt lake brine. The invention first prepares the polysulfone / zeolite imidazole salt framework blend membrane using a solvent-inducible phase separation method; then, it utilizes ZIF-8 in the membrane to first enrich Cu. 2+ , with Cu 2+ Using ions as a bridge, the membrane is immersed in a potassium ferrocyanide solution and then co-precipitated in situ to form copper ferrocyanide, thus obtaining a PSF / ZIF-8@KCuFC composite membrane. This composite membrane is Rb + Selective adsorption membranes, assembled into a separation system, can dynamically separate rubidium from salt lake brine. Compared with existing adsorption methods, the process is simple and highly efficient.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation, specifically relating to the preparation of a polysulfone / zeolite imidazole salt framework blend membrane@copper ferrocyanide composite membrane and its application in rubidium separation in salt lake brine. Background Technology

[0002] Rubidium has significant industrial and economic value. However, its extraction is difficult due to the complex composition of salt lake brine. Furthermore, the extraction of rubidium is challenging because of the high K content. + and Rb + Similar size and other physicochemical properties, brine for K extraction + Rb in the old brine + The loss of 99% of rubidium resources results in a severe waste of rubidium resources (Chu WF, et al., Industrial & Engineering Chemistry Research, 2024, 63, 4: 1988; Gao Dandan et al., Salt Lake Research, 2021, 30:1). Currently, there is an urgent need to develop efficient rubidium separation technology in salt lake brine. Membrane separation is a simple and efficient process that allows for dynamic separation. Its application in rubidium separation from salt lake brine would facilitate the resource recovery of rubidium from salt lakes.

[0003] Polysulfone membranes possess excellent resistance to ultraviolet light (aging, oxidation, acid and alkali, hydrolysis) and good mechanical strength, making them suitable for membrane separation in high-altitude salt lake areas with strong ultraviolet radiation and large temperature differences (Smitha B, et al, International Journal of hydrogen Energy, 2008, 33: 4138). However, because this material is a semi-permeable membrane, its molecular backbone contains hard-segment benzene rings, soft-segment ether bonds, and stable sulfone bonds, making it unsuitable for direct use in rubidium separation from salt lake brine. Therefore, researchers improved the hydrophilicity of the membrane using sulfonated polysulfone membranes and graphene oxide, and deposited Rb-resistant polysulfone in situ on this membrane. + KCuFC exhibits selective adsorption properties (Kim YK, et al, Chemical Engineering Journal, 2017, 313:1042), but the presence of carboxyl groups on the composite membrane affects its ability to adsorb Rb. + The selectivity. On the other hand, the topology and structure of the zeolite-like imidazolium ester framework-8 (ZIF-8, pore size approximately 3.4 Å) are similar to those of aluminosilicate zeolites, composed of Zn 2+ It is composed of imidazole ligands. ZIF-8 has advantages such as suitable pore size, good film-forming performance, and abundant active sites, and can be used as an adsorbent to separate Cu. 2+ / Pb 2+ / Hg 2+The adsorption mechanism for heavy metal ions involves a synergistic effect of ion exchange, coordination reactions, surface chemistry, and hydrophobicity (Zhang X, et al, New Journal of Chemistry, 2021, 45: 15876). ZIF-8 and polysulfone hybrid membranes have been used for the separation of H2 / CH4 and H2 / N2 (Fernando CB, et al, Journal of Membrane Science, 2014, 464: 119-126). Based on the properties of KCuFC and ZIF-8, two porous metal-organic framework materials, seeding KCuFC onto a ZIF-8 and polysulfone hybrid membrane could potentially lead to the formation of Rb. + Selective adsorption membranes. This allows for the extraction of rubidium from aqueous solutions using adsorption-coupled membrane separation. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a method for preparing a polysulfone / zeolite imidazole salt framework blend membrane@copper ferrocyanide composite membrane and its application in the separation of rubidium (Rb) from salt lake brine. + With the separation of two metal-organic frameworks, zeolite imidazole salt and copper ferrocyanide, was seeded onto a polysulfone membrane to obtain a heterobimetallic organic framework Rb. + Selective adsorption membrane (PSF / ZIF-8@KCuFC). This membrane is Rb. + Selective adsorption membranes, assembled into a separation system, can dynamically separate rubidium from salt lake brine. Compared with existing adsorption methods, the process is simple and highly efficient.

[0005] The present invention discloses a method for preparing a polysulfone / zeolite imidazole salt framework blend membrane@copper ferrocyanide composite membrane. First, a polysulfone / zeolite imidazole salt framework blend membrane (PSF / ZIF-8) is prepared by a solvent-free induced phase separation method. Then, Cu is enriched in the ZIF-8 layer of the base membrane. 2+ , with Cu 2+ Using ions as a bridge, the membrane is immersed in potassium ferrocyanide solution and then co-precipitated in situ to generate copper ferrocyanide (KCuFC), thus obtaining a PSF / ZIF-8@KCuFC composite membrane.

[0006] Specifically, the steps include the following:

[0007] Step 1: Preparation of PSF / ZIF-8 base film

[0008] The PSF / ZIF-8 mixed matrix membrane was prepared using a solvent-inducible phase separation method (Balkanloo PG, et al, Chemical Engineering Journal, 2024, 496: 153835). In 20 mL of N,N-dimethylformamide, 0.6 g of ZIF-8 and 2.4 g of polysulfone were added sequentially and mixed thoroughly. Then, 1 g of polyvinylpyrrolidone was added as a porogen, and the mixture was allowed to stand for 1 h to remove air bubbles. A 300 μm liquid film was scraped onto a glass plate and immediately transferred to a deionized water bath for phase transformation. After washing, the membrane was vacuum dried to obtain the PSF / ZIF-8 mixed matrix membrane.

[0009] Step 2: Impregnation and enrichment of Cu 2+

[0010] The PSF / ZIF-8 substrate film was immersed in a water-soluble copper salt solution for 1-6 hours to allow the substrate film to be fully enriched with Cu. 2+ When the membrane changes color ( One of the following: sky blue, sapphire blue, dark blue, light blue, or lake blue. After that, remove it, clean it (using one of the following: deionized water, 50% anhydrous ethanol, 50% acetone or 50% ether) and set it aside for later use.

[0011] Step 3: Preparation of PSF / ZIF-8@KCuFC composite membrane

[0012] The Cu enrichment obtained in step 2 2+ The PSF / ZIF-8 precursor membrane is immersed in potassium ferrocyanide solution for 1-8 hours. When the membrane changes color (to one of the following: brick red, rust red, shell yellow red, orange red, scarlet, or wine red), it is removed and cleaned (using one of the following: deionized water, 50% anhydrous ethanol, 50% acetone, or 50% ether) to obtain the PSF / ZIF-8@KCuFC composite membrane.

[0013] In step 2, during the impregnation process, the system temperature is 20-80℃ and the pH value is 2-6.

[0014] In step 2, the water-soluble copper salt is one or more of Cu(NO3)2, CuCl2, CuSO4, and Cu(COOH)2, with a concentration of 0.025 mol / L to 0.1 mol / L.

[0015] In step 3, during the impregnation process, the system temperature is 20-100℃ and the pH value is 2-6.

[0016] In step 3, the concentration of the potassium ferrocyanide solution is 0.025 mol / L-0.1 mol / L.

[0017] During the preparation process, the pH value of the system was adjusted using 0.1 mol / L HCl solution or 0.1 mol / L NaOH solution.

[0018] The present invention relates to the application of polysulfone / zeolite imidazole salt framework blend membrane@copper ferrocyanide composite membrane in rubidium separation in salt lake brine.

[0019] Specifically, the steps include the following:

[0020] (1) Brine pretreatment

[0021] Add the pretreatment agent to the salt lake brine, mix thoroughly, adjust the pH of the system to 4-6, maintain the temperature at 10-40℃, stir for 2-8 hours, and then filter out the brine for later use. Adjust the pH of the system using 0.1 mol / L HCl solution or 0.1 mol / L NaOH solution.

[0022] (2) Dynamic adsorption

[0023] Dilute the filtered brine 4-12 times and take 200 mL. Prepare 2-12 sheets (each with an effective area of ​​21 cm²). 2 A PSF / ZIF-8@KCuFC composite membrane containing approximately 4.5 mg of KCuFC was loaded into the membrane module. Rb in the brine was analyzed at 15℃-40℃, pH 4-8, and a peristaltic pump flow rate of 40 mL / min-150 mL / min. + Dynamic cyclic adsorption lasts 2-6 hours. Rb... + When ion concentrations are similar, it indicates that the composite membrane is effective against Rb. + The adsorption reached saturation. The membrane stack was then washed with deionized water for 0.2-2 hours.

[0024] (3) Dynamic desorption

[0025] Rb on PSF / ZIF-8@KCuFC composite membrane was treated with a desorption solution. + Dynamic cyclic desorption was performed for 2-6 hours, and the Rb content in the effluent was... + The concentration dropped to more than 85% of its original level, indicating that Rb on the composite membrane... + Desorption is complete.

[0026] The above process can be repeated to obtain Rb. + Purification solution. Inductively coupled plasma mass spectrometry (ICP-MS) was used to detect Rb in the brine or desorption solution. + The concentration change.

[0027] In step (1), the pretreatment agent is selected from one of montmorillonite, diatomaceous earth, zeolite, or clay. The mass ratio of the pretreatment agent to the brine of the salt lake is 1:10-1:50.

[0028] In step (3), the desorption solution is NH4Cl solution, NH4NO3 solution, or... CH3 COONH 4 One of the solutions, with a concentration of 0.05 mol / L - 0.5 mol / L.

[0029] In step (3) during desorption, the flow rate of the peristaltic pump is 40 mL / min-150 mL / min, and the pH of the system is 1-4 (using 0.1 mol / L HCl solution, HNO3 solution, or...). CH 3 COOH (A type of regulation in solution), with a temperature range of 10℃-40℃.

[0030] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0031] 1. The preparation method of the composite membrane of this invention is simple, environmentally friendly, low-cost, and has good mechanical properties. This invention utilizes a polysulfone / zeolite imidazole salt framework blend base membrane (PSF / ZIF-8) to first enrich Cu in ZIF-8. 2+ , to Cu 2+ Using metal ions (from the KCuFC organic framework) as a bridge, KCuFC is formed in situ by immersion in potassium ferrocyanide solution. This allows for the overlay of two heterogeneous bimetallic organic framework materials, ZIF-8 and KCuFC, onto the same acid- and alkali-resistant polysulfone membrane (PSF / ZIF-8@KCuFC). This composite membrane can dynamically and selectively separate Rb from brine in salt lakes. + .

[0032] 2. This invention will use Rb + Functional adsorbent KCuFC is seeded on the membrane, and Rb in salt lake brine is dynamically separated using an adsorption-coupled ion exchange desorption method. + This process is repeated to obtain rubidium purified solution, which, compared to the original brine, contains less potassium (K). + / Rb + Na + / Rb + and Mg 2+ / Rb + Significantly reduced. This technology is highly operable, has good separation effect, is environmentally friendly, and has good prospects for industrial application. Attached Figure Description

[0033] Figure 1 For PSF / ZIF-8(a) and ZIF-8 (illustration), PSF / ZIF-8 / Cu 2+ (b), PSF / ZIF-8@KCuFC (c) and magnified (inset), field emission scanning electron microscope (FE-SEM) images of the surface (d) and cross section (inset) of PSF / ZIF-8@KCuFC. Figure 1In (a), the ZIF-8 particles in the inset are approximately cubic, and the ZIF-8 particles in the PSF / ZIF-8 mixed base film are uniformly distributed. Figure 1 In (b), when PSF / ZIF-8 is immersed in Cu 2+ After solution (PSF / ZIF-8 / Cu) 2+ The surface structure of ZIF-8 collapsed, and its morphology diverged into a petal shape (illustration). Figure 1 In (c), PSF / ZIF-8 / Cu 2+ Immersed in potassium ferrocyanide, the Cu on it 2+ Cubic nano-KCuFC particles were formed by co-precipitation with K4(Fe(CN)6), and the original petal-like morphology disappeared. A large number of nanoparticles were modified on the film in a cluster-like manner (PSF / ZIF-8@KCuFC). Figure 1 In (d), the composite membrane material exhibits a 3D hierarchical porous structure with a membrane thickness of 100-120µm.

[0034] The morphology of ZIF-8 is affected by the Cu in the solution. 2+ The effect of concentration. This is because in tetrahedral coordination, Cu... 2+ (0.71Å) and Zn 2+ The ion size is comparable to (0.74 Å). When Cu in solution 2+ At lower concentrations, it can react with Zn. 2+ During normal ion exchange, when Cu in the reaction solution... 2+ At higher concentrations, Cu 2+ It interacts with the imidazole ligand in ZIF-8, causing the structure of ZIF-8 to collapse due to a high degree of ion exchange reaction (Yang W, et al, Journal of Solid State Chemistry, 2023, 326: 124217). This structural change allows it to load more nano-KCuFC particles on its surface, resulting in more adsorbent per unit area of ​​the film, which is beneficial for the adsorption of Rb. + .

[0035] Figure 2 The elemental distribution (EDS) of the PSF / ZIF-8@KCuFC composite film is shown. The composite film contains K, Fe, Zn, N, and Cu elements, which are uniformly distributed. The Cu / Zn ratio is relatively large at 16, which may be due to the presence of Zn in the ZIF-8 layer of the composite film. 2+ Cu 2+ Meanwhile, the in-situ generated KCuFC covers the ZIF-8 surface in the composite film.

[0036] Figure 3 for PSF / ZIF-8(a), PSF / ZIF-8@Cu2+ (b) PSF / ZIF-8@KCuFC (c) Adsorption of Rb + Post-(d) and desorbed Rb + The X-ray diffraction (XRD) pattern of the ZIF-8 crystal is shown in curve a. In curve a, the diffraction peaks of ZIF-8 crystal are located at 7.32 (011), 10.37° (002), 12.71° (112), 18.01° (222), 22.12° (114), 24.48° (233), and 26.66° (134) (Abdi J, et al, Chemical Engineering Journal, 2017, 326: 1145), indicating the formation of the PSF / ZIF-8 hybrid substrate film. In curve b, the ZIF-8 peaks originally located at 12.71° (112) and 26.66° (134) are significantly enhanced (Zhang L, et al, The Journal of Physical Chemistry C, 2011, 115, 7967). Due to Cu 2+ Interference, Zn metal skeleton in ZIF-8 2+ Cu 2+ The exchange causes the surface crystal structure of ZIF-8 on the hybrid substrate to disintegrate (Schubert DM, et al, Inorganica Chimica Acta, 2009, 362: 4832; Yang W, et al, Journal of Solid State Chemistry, 2023, 326: 124217). In curve c, when PSF / ZIF-8@Cu 2+ Immersed in K4[Fe(CN)6] solution, the Cu on it 2+ In-situ co-precipitation with K4(Fe(CN)6) formed PSF / ZIF-8@KCuFC within the mixed substrate film; characteristic peaks of KCuFC were observed at 17.69° (200), 24.68° (220), and 36.38° (400) (Zhang H, et al, ACS Applied Materials & Interfaces, 2020, 12: 33173; Ru J, et al, ACS Applied Materials & Interfaces, 2023, 2:17902); while PSF / ZIF-8@Cu 2+ The original peak at 12.71° (112) disappeared, and the peak at 26.66° (134) and the peak of KCuFC at 24.68° (220) broadened due to overlap. Curves d and e show that the PSF / ZIF-8@KCuFC composite membrane material adsorbs Rb+ Post-desorption Rb + The diffraction peaks after the curve are consistent with those in curve c, indicating that the membrane material is effective in separating Rb. + The structure is stable during the process. Furthermore, the size of the nano-KCuFC deposited on PSF / ZIF-8@KCuFC is approximately 11.3 nm, calculated using the Scherrer equation.

[0037] Figure 4 for ZIF-8(a), PSF(b), PSF / ZIF-8(c), PSF / ZIF-8@Cu 2+ (d) FT-IR spectra of PSF / ZIF-8@KCuFC (e). In curve a, the characteristic infrared peak of ZIF-8 is located at 419 cm⁻¹. -1 (Zn–N) and 994 cm -1 (C–N), and 800 cm -1 1000-1350 cm -1 and 1350-1500 cm -1 (Imidazole ring) (Balkanloo PG, et al, 2024, Chemical Engineering Journal, 496:153835). In curve b, 800-900 cm⁻¹ -1 and 1489-1586 cm -1 These are the stretching vibration peaks of CH and C on the benzene ring, respectively, at 1242 cm⁻¹. -1 The peaks are for the asymmetric stretching vibration of COC, at 1110 and 1151 cm⁻¹. -1 The peaks represent the symmetric and asymmetric stretching vibrations of the OSO molecule (Qiu B, et al, Journal of Membrane Science, 2022, 644: 120183). Curve c shows almost all the characteristic peaks in ZIF-8 (a) and PSF (b), indicating the formation of a PSF / ZIF-8 mixed substrate film. In curve d, due to the Cu on ZIF-8... 2+ and Zn 2+ Ion exchange and coordination reactions between them, located at 419 cm -1 The absorption peak of (Zn–N) is from 419 cm⁻¹ -1 Increased to 425 cm -1 In curve e, except for the peak in curve d, the peak at 2088 cm⁻¹ -1The new peak that appears corresponds to the stretching vibration peak of C≡N in KCuFC on the PSF / ZIF-8@KCuFC composite membrane (Fang M, et al, Applied Organometallic Chemistry, 2022, 36: e6827), indicating that the composite membrane has been formed.

[0038] Figure 5 Figure (A) shows the adsorption of Rb by PSF / ZIF-8@KCuFC. + The X-ray photoelectron spectroscopy (XPS) of the pre-adsorption composite film shows the presence of Cu, Fe, K, S, O, and C elements, indicating the formation of the PSF / ZIF-8@KCuFC film. (B) The figure shows the XPS of Rb in PSF / ZIF-8@KCuFC before (a) and after (b), and after (c) desorption. Adsorbed Rb + In the first (a) phase, no Rb peak appeared in the 106 eV-116 eV range, indicating Rb adsorption. + After (b), located at 110.38 eV (Rb3d 5 / 2 ) and 111.83eV (Rb3d 3 / 2 The characteristic peak of Rb is clearly visible at (c) (Zhang Z, et al, Desalination, 2023, 549: 11633); after desorption (c), the characteristic peak of Rb decreases significantly. The above results indicate that the composite membrane prepared in this invention can be applied to rubidium separation. Detailed Implementation

[0039] The technical solution of the present invention will be further analyzed and explained through specific embodiments below. Example 1:

[0040] 1. Preparation of PSF / ZIF-8@KCuFC composite membrane

[0041] (1) The PSF / ZIF-8 base membrane was immersed in 100 mL of Cu(NO3)2 at pH 4.5, 40℃, and 0.03 mol / L for 4 h to enrich Cu. 2+ Once the membrane turns light blue, remove it, wash it with anhydrous ethanol, and set it aside for later use to obtain PSF / ZIF-8@Cu. 2+ .

[0042] (2) PSF / ZIF-8@Cu 2+ The membrane was immersed in 100 mL of 0.04 mol / L potassium ferrocyanide (K4(Fe(CN)6)) at pH 5, 30℃ for 4 h. After the membrane turned orange-red, it was removed and washed with anhydrous ethanol to obtain PSF / ZIF-8@KCuFC. The pH of the solution was adjusted with 0.1 mol / L HCl or NaOH.

[0043] 2. Rb in the brine of Qarhan Salt Lake + Separation

[0044] (1) Brine pretreatment. Diatomaceous earth was used as the brine pretreatment agent, and the pretreatment agent to brine mass ratio was 1:20. The pH was adjusted to 5 with 0.1 mol / L HCl, the temperature was 20℃, and the brine was filtered out after stirring for 2 hours.

[0045] (2) Dynamic adsorption process. Dilute the above brine 8 times with deionized water and take 200 mL. Place 10 sheets (effective area 10×21 cm) into the solution. 2 PSF / ZIF-8@KCuFC (10 × 4.5 mg KCuFC) was loaded into the membrane module. Rb in the brine was analyzed at 20°C, pH 6, and a peristaltic pump flow rate of 40 mL / min. + Dynamic cyclic adsorption was performed for 4 hours, followed by washing the membrane stack with deionized water for 0.2 hours.

[0046] (3) Dynamic desorption process. Using 200 mL of 0.5 mol / L NH4Cl at pH 1 (pH adjusted with 0.1 mol / L HCl), a peristaltic pump at a flow rate of 40 mL / min, and a temperature of 35℃, the Rb on PSF / ZIF-8@KCuFC was desorbed. + Dynamic cyclic desorption was performed for 3 hours.

[0047] (4) Repeat steps (2) and (3) 5 times to obtain Rb. + Purification solution. Example 2:

[0048] 1. Preparation of PSF / ZIF-8@KCuFC composite membrane

[0049] (1) The PSF / ZIF-8 base membrane was immersed in 100 mL of 0.08 mol / L CuSO4 at pH 6, 25℃ for 2 h to enrich Cu. 2+ When the membrane shows Lake Blue After coloring, remove the sample, rinse with deionized water, and set aside for later use to obtain PSF / ZIF-8@Cu. 2+ .

[0050] (2) PSF / ZIF-8@Cu 2+ The membrane was immersed in 100 mL of 0.08 mol / L potassium ferrocyanide (K4(Fe(CN)6)) at pH 5, 25℃ for 2 h. After the membrane turned rust red, it was removed and washed with 50% ethanol to obtain the PSF / ZIF-8@KCuFC composite membrane.

[0051] 2. Rb in salt lake brine+ Separation

[0052] (1) Brine pretreatment. Clay was used as the brine pretreatment agent and mixed evenly at a ratio of pretreatment agent to brine of 1:25. The pH was adjusted to 6 with 0.1 mol / L HCl or NaOH, the temperature was 20℃, and the brine was filtered out after stirring for 4 hours.

[0053] (2) Dynamic adsorption process. Dilute the above brine 10 times with deionized water and take 200 mL. Place 12 sheets (effective area 12×21 cm) into the solution. 2 A PSF / ZIF-8@KCuFC composite membrane (containing 12 × 4.5 mg KCuFC) was loaded into the membrane module. Dynamic circulation adsorption with brine was performed for 2.5 h at 30℃, pH 6.5, and a peristaltic pump flow rate of 50 mL / min. After completion, the membrane stack was rinsed with deionized water for 0.2 h.

[0054] (3) Dynamic desorption process. 200 mL of 0.8 mol / L NH4Cl / HCl was used as the desorption solution, and the peristaltic pump flow rate was 60 mL / min. The Rb on the PSF / ZIF-8@KCuFC composite membrane was desorbed. + Dynamic cyclic desorption was performed for 3 hours.

[0055] (4) Repeat steps (2) and (3) 4 times to obtain Rb. + Purification solution. Example 3:

[0056] 1. Preparation of PSF / ZIF-8@KCuFC composite membrane

[0057] (1) The PSF / ZIF-8 base membrane was immersed in 100 mL of 0.025 mol / L CuCl2 at pH 7, 20℃ for 6 h to enrich Cu. 2 + When the membrane shows Sky blue After coloring, remove the sample, rinse with deionized water, and set aside for later use to obtain PSF / ZIF-8@Cu. 2+ .

[0058] (2) PSF / ZIF-8@Cu 2+ The membrane was immersed in 80 mL of 0.05 mol / L potassium ferrocyanide (K4(Fe(CN)6)) at pH 5, 35℃ for 3 hours. When the membrane showed a light crab shell red color, it was removed and washed with 50% acetone to obtain the PSF / ZIF-8@KCuFC composite membrane.

[0059] 2. Rb in salt lake brine + Separation

[0060] (1) Brine pretreatment. Montmorillonite was used as the brine pretreatment agent, and the pretreatment agent to brine mass ratio was 1:40. The pH was adjusted to 5 with 0.1 mol / L HCl or NaOH, the temperature was 30℃, and the brine was filtered out after stirring for 3 hours.

[0061] (2) Dynamic adsorption process. Dilute the above brine 6 times with deionized water and take 300 mL. Place 12 sheets (effective area 12×21 cm) into the solution. 2 A PSF / ZIF-8@KCuFC composite membrane (containing 12 × 4.5 mg KCuFC) was loaded into the membrane module. Dynamic circulation adsorption with brine was performed for 4 hours at 40℃, pH 7, and a peristaltic pump flow rate of 80 mL / min. After completion, the membrane stack was rinsed with deionized water for 0.3 hours.

[0062] (3) Dynamic desorption process. Using 200 mL of 0.8 mol / L NH4Cl / HCl as the desorption solution, a peristaltic pump with a flow rate of 60 mL / min, and a temperature of 15℃, the Rb on the PSF / ZIF-8@KCuFC composite membrane was desorbed. + Dynamic cyclic desorption was performed for 4 hours.

[0063] (4) Repeat steps (2) and (3) 5 times to obtain Rb. + Purification solution.

[0064] As shown in Table 1, the rubidium recovery rate in the brine using the technology of this invention is greater than 81.39%. The concentration of impurity ions in the obtained purified solution is significantly reduced; Na... + / Rb + All decreased from above 156 to below 0.8; Mg 2+ / Rb + All decreased from above 1197 to below 4.2; K + / Rb + All values ​​decreased from above 269 to below 4.8. This indicates that the composite membrane has a good effect on Rb. + It exhibits excellent selective separation performance.

[0065]

[0066] Example 4: Effects of PSF / ZIF-8@KCuFC and PSF / ZIF-8 on Rb in salt lake brine + Recycling comparison

[0067] This invention compares the effects of PSF / ZIF-8@KCuFC and PSF / ZIF-8 on Rb in salt lake brines. +The separation effect was observed. The methods of Examples 1, 2, and 3 were used respectively (Table 2). As shown in Table 2, the PSF / ZIF-8@KCuFC membrane prepared using the technology of this invention effectively separated Rb from the brine. + The recovery rates were all greater than 81.39%. The PSF / ZIF-8 membrane was used for the recovery of Rb from salt lake brine. + The recoveries were all less than 0.4%, and the selectivity was poor. This indicates that the PSF / ZIF-8@KCuFC composite membrane prepared in this invention has poor selectivity for Rb in salt lake brine. + It exhibits excellent separation performance. However, due to issues related to adsorbent recovery and separation, directly using powdered nano-KCuFC to separate rubidium in brine is not advisable in practical operation.

[0068]

Claims

1. A method for preparing a polysulfone / zeolite imidazole salt framework blended base membrane@copper ferrocyanide composite membrane, characterized in that: First, a polysulfone / zeolite imidazole salt framework blend membrane was prepared by a solvent-inducible phase separation method; then, Cu was enriched using ZIF-8 in the membrane. 2+ , with Cu 2+ Using ions as a bridge, the membrane is immersed in potassium ferrocyanide solution and then co-precipitated in situ to generate copper ferrocyanide, thus obtaining a PSF / ZIF-8@KCuFC composite membrane. Specifically, the steps include the following: Step 1: Preparation of PSF / ZIF-8 base film 0.6 g of ZIF-8 and 2.4 g of polysulfone were added sequentially to N,N-dimethylformamide and mixed thoroughly. Then, 1.0 g of polyvinylpyrrolidone was added as a porogen. After thorough mixing, the mixture was allowed to stand to remove air bubbles. The liquid film was then scraped off onto a glass plate and transferred to a deionized water bath for phase transformation. After washing the film, it was vacuum dried to obtain a PSF / ZIF-8 mixed matrix membrane. Step 2: Impregnation and enrichment of Cu 2+ The PSF / ZIF-8 hybrid matrix membrane was immersed in a water-soluble copper salt solution for 1-6 hours to allow the membrane to be fully enriched with Cu. 2+ Once the membrane changes color, remove it, clean it, and set it aside for later use. Step 3: Preparation of PSF / ZIF-8@KCuFC composite membrane The Cu enrichment obtained in step 2 2+ The PSF / ZIF-8 precursor membrane was immersed in potassium ferrocyanide solution for 1-8 hours. After the membrane changed color, it was removed, cleaned, and the PSF / ZIF-8@KCuFC composite membrane was obtained.

2. The preparation method according to claim 1, characterized in that: In step 2, during the impregnation process, the system temperature is 20-80℃ and the pH value is 2-6.

3. The preparation method according to claim 1, characterized in that: In step 2, the water-soluble copper salt is one or more of Cu(NO3)2, CuCl2, CuSO4, and Cu(COOH)2, and the concentration of the water-soluble copper salt solution is 0.025 mol / L-0.1 mol / L.

4. The preparation method according to claim 1, characterized in that: In step 3, during the impregnation process, the system temperature is 20-100℃ and the pH value is 2-6.

5. The preparation method according to claim 1, characterized in that: In step 3, the concentration of the potassium ferrocyanide solution is 0.025 mol / L-0.1 mol / L.

6. The application of the polysulfone / zeolite imidazole salt skeleton blend membrane@copper ferrocyanide composite membrane prepared by the preparation method according to any one of claims 1-5 in the separation of rubidium in salt lake brine.

7. The application according to claim 6, characterized in that... Includes the following steps: (1) Brine pretreatment Add the pretreatment agent to the salt lake brine, mix well, adjust the pH of the system to 4-6 and the temperature to 10-40℃, stir for 2-8 hours, and then filter out the brine for later use. (2) Dynamic adsorption Dilute the filtered brine 4-12 times and take 200 mL; load the PSF / ZIF-8@KCuFC composite membrane into the membrane module, and perform Rb analysis in the brine at 15℃-40℃, pH 4-8, and a peristaltic pump flow rate of 40 mL / min-150 mL / min. + Dynamic cyclic adsorption; (3) Dynamic desorption Rb on PSF / ZIF-8@KCuFC composite membrane was treated with a desorption solution. + Dynamic cyclic desorption was performed for 2-6 hours, and the Rb content in the effluent was... + The concentration dropped to more than 85% of its original level, indicating that Rb on the composite membrane... + Desorption is complete.

8. The application according to claim 7, characterized in that: In step (1), the pretreatment agent is selected from one of montmorillonite, diatomite, zeolite or clay; the mass ratio of the pretreatment agent to the salt lake brine is 1:10-1:

50.

9. The application according to claim 7, characterized in that: In step (3), the desorption solution is one of NH4Cl solution, NH4NO3 solution or CH3COONH4 solution, with a concentration of 0.05 mol / L - 0.5 mol / L.

Images