A high permeability composite nanofiltration membrane based on mercapto-UiO-66 and a preparation method thereof

Abstract

The application discloses a kind of based on sulfhydryl-UiO-66 high permeability composite nanofiltration membrane and preparation method thereof, steps are as follows: (1) using solvent hot synthesis method to prepare the suspension containing sulfhydryl-UiO-66;(2) the suspension of step (1) is centrifuged, after washing and drying, obtain sulfhydryl-UiO-66 nanomaterial;(3) preparation PIP aqueous solution and TMC n-hexane solution;(4) a certain concentration sulfhydryl-UiO-66 is ultrasonically dispersed in PIP aqueous solution or TMC n-hexane solution, obtain corresponding phase suspension;(5) PIP aqueous solution or PIP aqueous phase suspension is immersed PSF ultrafiltration membrane surface, subsequently n-hexane solution or n-hexane organic phase suspension is soaked PSF ultrafiltration membrane surface;(6) the membrane obtained in step (5) is heat treated and cleaned, obtain sulfhydryl-UiO-66 high permeability composite nanofiltration membrane.The composite nanofiltration membrane of the application has high permeability, high pore structure uniformity, and the effective separation of ion size similar cation.

Description

Technical Field

[0001] This invention relates to the field of nanofiltration membrane materials technology, and in particular to a high-permeability composite nanofiltration membrane based on mercapto-UiO-66 and its preparation method. Background Technology

[0002] Nanofiltration technology has been widely applied in various fields such as dyeing and printing wastewater treatment, seawater desalination, and lithium / magnesium separation. Among these, the membrane composite membrane produced by interfacial polymerization (IP), which involves forming a cross-linked polyamide (PA) separation layer on a porous polymer substrate using amine monomers and acyl chloride monomers, is currently the mainstream nanofiltration membrane type. However, in the IP reaction, the uncontrolled diffusion of amine monomers and the rapid chemical reaction kinetics between amine and acyl chloride monomers lead to a random distribution of polymer chains in the prepared PA layer structure. This intricate and disordered PA chain stacking undoubtedly increases the permeation resistance of water molecules, hindering the improvement of permeation performance. Furthermore, nanofiltration membranes typically have pore sizes of around 0.5-2 nm and a molecular weight cutoff range of 200-1000 Da, still exhibiting a wide pore size distribution, which cannot meet the requirements for separating ions of similar sizes.

[0003] Therefore, inducing the ordered arrangement of PA chains and developing nanofiltration membrane materials with concentrated pore size distribution and high permeability remains a challenge in nanofiltration membrane preparation. Currently, methods to effectively regulate the ordered arrangement of PA chains to achieve uniform pore size distribution can be achieved by influencing monomer diffusion. For example, the oil-soluble surfactant dodecyl phosphoric acid can be used to regulate the IP reaction. The amphiphilic nature of dodecyl phosphoric acid allows it to spread in a monolayer at the water / oil interface, thereby promoting the diffusion of amine monomers and regulating the IP reaction. The resulting nanofiltration membrane has more uniform pores and a narrower pore size distribution. In addition, using porous materials as an interlayer not only enables controllable diffusion of aqueous monomers, but its high porosity and uniform pore size can also promote the uniform distribution of aqueous monomers in the interlayer, thus contributing to the uniform pore size distribution of the PA layer. It is worth noting that the above strategies all control the IP process by slowing down the reaction or confining the reaction to a limited space. However, in experimental design, the directional arrangement of monolayer molecules at the interface and the preparation of a defect-free interlayer are undoubtedly quite difficult. Therefore, there is an urgent need to develop a simple method for controlling the pore size and uniformity of PA layers.

[0004] Metal-organic frameworks (MOFs) are one of the most promising membrane modification materials due to their unique structural diversity and rich chemical modifiability. Compared with the pores of organic polymer membranes, MOFs have rigid and stable uniform pore structures that can provide low resistance transport channels for mass transfer processes. Compared with other inorganic nanoporous materials, the controllability of their size and surface chemical properties makes them have better compatibility with high molecular polymers. However, since MOFs mainly exist in the form of powders, simply mixing polymers with MOFs often causes ineffective adjustment to the formation process of the selective layer. Specifically, the introduction of MOFs only provides additional mass transfer channels in the polymer matrix, and does not play a role in adjusting the IP process to optimize the structure of the PA layer. SUMMARY

[0005] To solve the problem of low permeability, wide pore size distribution and inability to achieve selective screening of ions with similar sizes caused by the disordered accumulation of polymer chains in the PA separation layer of the nanofiltration membrane in the prior art, a general strategy is proposed for adjusting the PA structure and narrowing the pore size distribution range by modifying MOF particles with thiol groups and using the hydrogen bonding between thiol functional groups and polymer monomers. A thiol-UiO-66-based high-permeability composite nanofiltration membrane and a preparation method thereof are invented. In the present invention, thiol-UiO-66 is used as a nano-additive to assist the interfacial polymerization reaction by dispersing it in the aqueous or organic phase, to adjust the interfacial polymerization diffusion reaction process, achieve the effect of ordered arrangement of polymer chains in the polyamide layer of the nanofiltration membrane, reduce the permeation resistance and improve the water flux, and thus prepare a composite nanofiltration membrane with high permeability and uniform pore structure. It is particularly pointed out that, compared with traditional polyamide composite nanofiltration membranes, the composite nanofiltration membrane containing thiol-UiO-66 has significantly improved selectivity for Li + / Mg 2+ Therefore, the introduction of thiol-UiO-66 not only greatly improves the permeability of the nanofiltration membrane, but also effectively separates Li + / Mg 2+ with similar ion sizes.

[0006] The present invention is achieved in this way. A preparation method of a thiol-UiO-66-based high-permeability composite nanofiltration membrane comprises the following steps:

[0007] (1) Using a zirconium chloride solution as a metal source, a dicarboxylic acid containing thiol groups as an organic ligand, a monocarboxylic acid as a particle size regulator, and water or N,N-dimethylformamide as a reaction solvent, the mixed solution is subjected to solvothermal synthesis at a certain temperature for a certain time to obtain a suspension containing thiol-UiO-66 nanomaterials;

[0008] (2) centrifuging the suspension containing the thiol-UiO-66 nanomaterial obtained in step (1), washing with a reaction solvent and an alcohol solvent, and drying in an oven at a certain temperature to obtain the thiol-UiO-66 nanomaterial;

[0009] (3) preparing a piperazine (PIP) aqueous solution with a certain concentration and a trimesoyl chloride (TMC) n-hexane solution with a certain concentration;

[0010] (4) ultrasonic dispersing the thiol-UiO-66 nanomaterial with a certain concentration in the piperazine aqueous solution or the trimesoyl chloride n-hexane solution of step (3) to obtain a corresponding phase suspension containing the thiol-UiO-66;

[0011] (5) immersing the piperazine aqueous solution or the piperazine aqueous phase suspension containing the thiol-UiO-66 on the surface of a polysulfone (PSF) ultrafiltration membrane for a certain time, and then removing the residual aqueous solution or aqueous phase suspension; subsequently immersing the trimesoyl chloride n-hexane solution or the trimesoyl chloride n-hexane organic phase suspension containing the thiol-UiO-66 on the surface of the polysulfone (PSF) ultrafiltration membrane for a certain time, and then removing the residual n-hexane solution or n-hexane organic phase suspension;

[0012] (6) heat treating the membrane obtained in step (5) at a certain temperature for a certain time, and then washing with a n-hexane solvent to obtain a thiol-UiO-66 high-permeability composite nanofiltration membrane.

[0013] In the present application, a MOF material, i.e., a thiol-modified UiO-66 nanomaterial, is selected as an additive to prepare a nanofiltration membrane. In the IP process, the thiol functional groups in the thiol-UiO-66 material can not only produce hydrogen bond interactions with the two-phase monomers of piperazine (PIP) and trimesoyl chloride (TMC), thereby adjusting the IP process to prepare a PA layer with ordered arrangement of polymer chains, but also the rigid nanoscale channels of the thiol-UiO-66 can also help the selective screening of solutes.

[0014] In the present application, in order to prepare a PA separation layer structure with uniform pore size distribution, the thiol-UiO-66 nanomaterial is dispersed in an aqueous phase containing PIP monomers or an organic phase containing TMC monomers to perform an interfacial polymerization reaction, thereby realizing the preparation of a high-permeability composite nanofiltration membrane. The high-permeability composite nanofiltration membrane based on the thiol-UiO-66 prepared by the method of the present application has higher water / salt permeability and a narrower pore size distribution range than traditional nanofiltration membranes.

[0015] The advantages of the present application are: (1) the thiol-functional modified UiO-66 nanomaterial is used as an additive for the preparation of a composite nanofiltration membrane, and the nanoscale channel itself has excellent ion sieving effect; (2) the thiol functional groups in the thiol-UiO-66 can interact with the two-phase monomers through hydrogen bonding during the IP process, so that the PA chains can be orderly arranged under the induction of hydrogen bonding, forming a PA layer structure with uniform pore size distribution.

[0016] Further, in the step (1), the concentration of the zirconium chloride solution is 0.01-0.1 mmol / mL; the dicarboxylic acid containing thiol is one of 2-mercaptosuccinic acid (MSA), 2,3-dimercaptosuccinic acid (DMSA), and 2,5-dimercaptoterephthalic acid, and the concentration is 0.1-10 mmol / mL; the monocarboxylic acid is one of formic acid or glacial acetic acid, and the volume ratio of the monocarboxylic acid to the reaction solvent is 3:20-100.

[0017] Further, the conditions required for preparing thiol-UiO-66 nanomaterials with different pore sizes and specific surface areas are different, for the preparation of UiO-66-DMSA nanomaterials, the dicarboxylic acid containing thiol is preferably 2,3-dimercaptosuccinic acid, the solvent is preferably water, the monocarboxylic acid is preferably formic acid, the concentration of the zirconium chloride solution is preferably 0.01 mmol / mL, the concentration of 2,3-dimercaptosuccinic acid is preferably 10 mmol / mL, and the volume ratio of formic acid to water is preferably 3:100.

[0018] Further, the conditions required for preparing thiol-UiO-66 nanomaterials with different pore sizes and specific surface areas are different, for the preparation of UiO-66-(SH)2 nanomaterials, the dicarboxylic acid containing thiol is preferably 2,5-dimercaptoterephthalic acid, the solvent is preferably N,N-dimethylformamide, the monocarboxylic acid is preferably glacial acetic acid, the concentration of the zirconium chloride solution is preferably 0.1 mmol / mL, the concentration of 2,5-dimercaptoterephthalic acid is preferably 0.1 mmol / mL, and the volume ratio of glacial acetic acid to N,N-dimethylformamide is preferably 3:20.

[0019] Further, in the step (1), the reaction temperature is 100-140℃, and the reaction time is 10-14 hours.

[0020] Further, in the step (2), the alcohol solvent is one of methanol and ethanol, which is cleaned 3-5 times, and the oven temperature is 60-70℃.

[0021] Further, when the prepared thiol-UiO-66 nanomaterial is UiO-66-DMSA, the alcohol solvent is preferably methanol.

[0022] Furthermore, when the prepared mercapto-UiO-66 nanomaterial is UiO-66-(SH)2, the preferred alcohol solvent is ethanol.

[0023] Further, in step (3), the concentration of the piperazine aqueous solution is 0.8–1.2 wt%, and the concentration of the trimesoyl chloride n-hexane solution is 0.1–0.2 w / v.

[0024] Furthermore, in step (4), the concentration of mercapto-UiO-66 in the corresponding phase suspension is 0.02–0.08 w / v.

[0025] Further, in step (5), the time for impregnating the surface of the polysulfone ultrafiltration membrane with piperazine aqueous solution or piperazine aqueous suspension containing mercapto-UiO-66 is 2 to 5 minutes; the time for immersing the surface of the polysulfone ultrafiltration membrane with trimesoyl chloride n-hexane solution or trimesoyl chloride n-hexane organic phase suspension containing UiO-66 is 0.5 to 1 minute.

[0026] Furthermore, in step (6), the heat treatment temperature is 60-70°C and the heat treatment time is 8-12 minutes.

[0027] A high-permeability composite nanofiltration membrane based on thiol-UiO-66 was prepared using the above-described method.

[0028] Furthermore, the obtained mercapto-UiO-66 high-permeability composite nanofiltration membrane achieved a Na2SO4 brine flux of 13.90–21.16 L·m⁻¹ under a pressure of 0.4 MPa. -2 ·h -1 The rejection rate of Na2SO4 is over 95%.

[0029] When mercapto-UiO-66 is ultrasonically dispersed in a solution of trimesoyl chloride and hexane, the resulting mercapto-UiO-66 high-permeability composite nanofiltration membrane exhibits good performance against Li + / Mg 2+ With a selectivity of over 20, it can achieve Mg 2+ With Li + Highly selective separation of cations with similar hydrated ionic radii.

[0030] The advantages and positive effects of this invention are:

[0031] 1. This invention utilizes thiol-functionalized UiO-66 nanomaterials for the preparation of composite nanofiltration membranes, breaking the traditional limitation of wide pore size distribution in the PA layer of nanofiltration membranes (pore size distribution: It can only separate the boundary between monovalent and divalent anions, and prepares a product with a narrow pore size distribution (pore size distribution: ), with high efficiency Li + / Mg2+ Separation selective composite nanofiltration membrane.

[0032] 2、The present application in the interface polymerization process, the mercapto-UiO-66 nanomaterial is influenced by the hydrogen bond interaction with piperazine (PIP) and trimesoyl chloride (TMC) two-phase monomer to affect the polymerization process, and then the polyamide chain is ordered to grow, and the pore size is more uniform, compared with the traditional nanofiltration membrane, the water flux is increased by 14.58-21.21%. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The scanning electron microscope graph of the UiO-66-DMSA nanomaterial obtained from the present application examples 1-8;

[0034] Figure 2 The scanning electron microscope graph of the UiO-66-(SH)2 nanomaterial obtained from the present application examples 9-16;

[0035] Figure 3 The pore size distribution test graph of the UiO-66-DMSA composite nanofiltration membrane obtained from the present application examples 1-8;

[0036] Figure 4 The pore size distribution test graph of the UiO-66-(SH)2 composite nanofiltration membrane obtained from the present application examples 9-16;

[0037] Figure 5 The pore size distribution graph of the composite nanofiltration membrane obtained from the present application comparative example, example 3 and example 11. DETAILED DESCRIPTION

[0038] In order for those skilled in the art to more clearly understand the present application, the present application is further described in detail below in conjunction with examples, but it should be understood that the following examples are only preferred embodiments of the present application, and the scope of protection claimed by the present application is not limited to this.

[0039] The present application provides a preparation method of a high-permeability composite nanofiltration membrane based on mercapto-UiO-66, comprising the following steps:

[0040] (1) taking zirconium chloride solution as a metal source, taking a dicarboxylic acid containing mercapto as an organic ligand, taking a monocarboxylic acid as a particle size regulator, and taking water or N,N-dimethylformamide as a reaction solvent, the mixed solution is reacted at a certain temperature for a certain time by a solvothermal synthesis method to obtain a suspension containing mercapto-UiO-66 nanomaterial;

[0041] The zirconium chloride solution has a concentration of 0.01-0.1 mmol / mL; the dithiol-containing dicarboxylic acid is one of 2-mercaptosuccinic acid (MSA), 2,3-dimercaptosuccinic acid (DMSA) and 2,5-dimercaptoterephthalic acid, and has a concentration of 0.1-10 mmol / mL; the monocarboxylic acid is one of formic acid and glacial acetic acid, and has a volume ratio of 3:20-100 to the reaction solvent.

[0042] The conditions required for preparing the thiol-UiO-66 nanomaterials with different pore sizes and specific surface areas are different. In this embodiment, for the preparation of the UiO-66-DMSA nanomaterial, the dithiol-containing dicarboxylic acid is preferably 2,3-dimercaptosuccinic acid, the solvent is preferably water, the monocarboxylic acid is preferably formic acid, the concentration of the zirconium chloride solution is preferably 0.01 mmol / mL, the concentration of 2,3-dimercaptosuccinic acid is preferably 10 mmol / mL, and the volume ratio of formic acid to water is preferably 3:100. For the preparation of the UiO-66-(SH)2 nanomaterial, the dithiol-containing dicarboxylic acid is preferably 2,5-dimercaptoterephthalic acid, the solvent is preferably N,N-dimethylformamide, the monocarboxylic acid is preferably glacial acetic acid, the concentration of the zirconium chloride solution is preferably 0.1 mmol / mL, the concentration of 2,5-dimercaptoterephthalic acid is preferably 0.1 mmol / mL, and the volume ratio of glacial acetic acid to N,N-dimethylformamide is preferably 3:20.

[0043] The reaction temperature is 100-140℃, and the reaction time is 10-14 hours. In this embodiment, the reaction temperature is preferably 120℃, and the reaction time is preferably 12 hours.

[0044] (2) The suspension containing the thiol-UiO-66 nanomaterial obtained in step (1) is centrifuged, washed with the reaction solvent and an alcoholic solvent respectively, and dried in an oven at a certain temperature to obtain the thiol-UiO-66 nanomaterial;

[0045] The alcoholic solvent is one of methanol and ethanol, and is washed for 3-5 times, and the oven temperature is 60-70℃. In this embodiment, when the prepared thiol-UiO-66 nanomaterial is UiO-66-DMSA, the alcoholic solvent is preferably methanol; when the prepared thiol-UiO-66 nanomaterial is UiO-66-(SH)2, the alcoholic solvent is preferably ethanol; the washing is performed for 3 times, and the oven temperature is 65℃.

[0046] (3) A piperazine (PIP) aqueous solution with a certain concentration and a trimesoyl chloride (TMC) n-hexane solution with a certain concentration are prepared;

[0047] The concentration of the piperazine aqueous solution is 0.8-1.2 wt%, and the concentration of the trimesoyl chloride n-hexane solution is 0.1-0.2 w / v%. In this embodiment, the concentration of the piperazine aqueous solution is preferably 1 wt%, and the concentration of the trimesoyl chloride n-hexane solution is preferably 0.15 w / v%.

[0048] (4) ultrasonic dispersion of a certain concentration of thiol-UiO-66 nanomaterial in the piperazine aqueous solution or the trimesoyl chloride n-hexane solution of step (3) to obtain a corresponding phase suspension containing thiol-UiO-66;

[0049] The concentration of the thiol-UiO-66 in the corresponding phase suspension is 0.02-0.08 w / v%.

[0050] (5) immersion of the piperazine aqueous solution or the piperazine aqueous phase suspension containing thiol-UiO-66 on the surface of a polysulfone (PSF) ultrafiltration membrane for a certain period of time, and then removal of the residual aqueous solution or the aqueous phase suspension; followed by immersion of the trimesoyl chloride n-hexane solution or the trimesoyl chloride n-hexane organic phase suspension containing thiol-UiO-66 on the surface of the polysulfone (PSF) ultrafiltration membrane for a certain period of time, and then removal of the residual n-hexane solution or the n-hexane organic phase suspension;

[0051] The immersion time of the piperazine aqueous solution or the piperazine aqueous phase suspension containing thiol-UiO-66 on the surface of the polysulfone ultrafiltration membrane is 2-5 min, and the immersion time of the trimesoyl chloride n-hexane solution or the trimesoyl chloride n-hexane organic phase suspension containing thiol-UiO-66 on the surface of the polysulfone ultrafiltration membrane is 0.5-1 min. In this embodiment, the immersion time of the piperazine aqueous solution or the piperazine aqueous phase suspension containing thiol-UiO-66 on the surface of the polysulfone ultrafiltration membrane is preferably 3 min, and the immersion time of the trimesoyl chloride n-hexane solution or the trimesoyl chloride n-hexane organic phase suspension containing thiol-UiO-66 on the surface of the polysulfone ultrafiltration membrane is preferably 1 min.

[0052] (6) heat treatment of the membrane obtained in step (5) at a certain temperature for a certain period of time, followed by solvent cleaning to obtain a thiol-UiO-66 high-permeability composite nanofiltration membrane.

[0053] The heat treatment temperature is 60-70℃, and the heat treatment time is 8-12 min. In this embodiment, the heat treatment temperature is preferably 65℃, and the heat treatment time is preferably 10 min.

[0054] In order to better understand the above-mentioned embodiments of the present application, the following specific examples are further described.

[0055] In the following examples and comparative examples:

[0056] Zirconium chloride, analytical pure, purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.;

[0057] 2,3-dimercaptobutyric acid, purity ≥98%, purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.;

[0058] 2,5-dimercaptoterephthalic acid, purity ≥ 97%, purchased from Shanghai Aladdin Biochem Technology Co., Ltd.;

[0059] 2-mercaptosuccinic acid, purity ≥ 98%, purchased from Shanghai Aladdin Biochem Technology Co., Ltd.;

[0060] Anhydrous piperazine (PIP), analytical pure, purchased from Shanghai Aladdin Biochem Technology Co., Ltd.;

[0061] Trimesoyl chloride (TMC), analytical pure, purchased from Shanghai Aladdin Biochem Technology Co., Ltd.;

[0062] N-hexane, analytical pure, purchased from Tianjin Kermel Chemical Reagent Co., Ltd.;

[0063] N,N-dimethylformamide (DMF), analytical pure, purchased from Tianjin Kermel Chemical Reagent Co., Ltd.;

[0064] Glacial acetic acid, analytical pure, purchased from Shanghai Aladdin Biochem Technology Co., Ltd.;

[0065] Formic acid, analytical pure, purity ≥ 96%, purchased from Shanghai Aladdin Biochem Technology Co., Ltd.;

[0066] Poly sulfone (PSF) ultrafiltration membrane, self-made in the laboratory, the pure water permeation flux is 150-200 L·m -2 ·h -1 , and the bovine serum protein rejection rate is 97.5-98.5%.

[0067] Example 1:

[0068] A preparation method of a high-permeability composite nanofiltration membrane based on mercapto-UiO-66, comprising the following steps:

[0069] (1) 5 mL of 2,3-dimercaptosuccinic acid (DMSA) aqueous solution with a concentration of 10 mmol / mL is mixed with 5 mL of ZrCl4 aqueous solution with a concentration of 0.01 mmol / mL, 300 μL of formic acid is added and mixed, and then placed in a 120℃ oven for constant temperature reaction for 12 hours;

[0070] (2) After the reaction is completed, the obtained suspension containing mercapto-UiO-66 nanomaterial is centrifuged and separated, the solid obtained by centrifugal separation is washed with water and methanol for 3 times respectively, and dried in a 65℃ oven to obtain mercapto-UiO-66-DMSA nanomaterial;

[0071] (3) Prepare a PIP aqueous solution with a concentration of 1 wt% and a TMC n-hexane solution with a concentration of 0.15 w / v%;

[0072] (4) ultrasonic dispersion of thiol-UiO-66-DMSA nanomaterials with a concentration of 0.02 w / v% in the TMC n-hexane solution obtained in step (3) to obtain a TMC n-hexane organic phase suspension containing thiol-UiO-66-DMSA;

[0073] (5) after the PIP aqueous solution in step (3) is immersed on the surface of the PSF ultrafiltration membrane for 3 min, the residual aqueous solution is removed, and then the TMC n-hexane organic phase suspension containing thiol-UiO-66-DMSA in step (4) is immersed on the surface of the PSF ultrafiltration membrane for 1 min, and the residual n-hexane organic phase suspension is removed;

[0074] (6) the membrane obtained in step (5) is heat treated at 65°C for 10 min, and after washing with n-hexane, a thiol-UiO-66-DMSA high-permeability composite nanofiltration membrane is obtained.

[0075] Example 2:

[0076] A preparation method of a thiol-UiO-66 high-permeability composite nanofiltration membrane, which is different from example 1 in that in step (4), the concentration of thiol-UiO-66-DMSA nanomaterials in the organic phase suspension is 0.04 w / v%, and the rest of the conditions remain unchanged.

[0077] Example 3:

[0078] A preparation method of a thiol-UiO-66 high-permeability composite nanofiltration membrane, which is different from example 1 in that in step (4), the concentration of thiol-UiO-66-DMSA nanomaterials in the organic phase suspension is 0.06 w / v%, and the rest of the conditions remain unchanged.

[0079] Example 4:

[0080] A preparation method of a thiol-UiO-66 high-permeability composite nanofiltration membrane, which is different from example 1 in that in step (4), the concentration of thiol-UiO-66-DMSA nanomaterials in the organic phase suspension is 0.08 w / v%, and the rest of the conditions remain unchanged.

[0081] Example 5:

[0082] A preparation method of a high-permeability composite nanofiltration membrane based on mercapto-UiO-66, which is different from example 1 in that in step (4), the mercapto-UiO-66-DMSA nanomaterial with a concentration of 0.02 w / v% is ultrasonically dispersed in the PIP aqueous solution obtained in step (3) to obtain a piperazine aqueous phase suspension containing mercapto-UiO-66-DMSA; in step (5), the piperazine aqueous phase suspension containing mercapto-UiO-66-DMSA in step (4) is immersed on the surface of the PSF ultrafiltration membrane for 3 min, and then the residual aqueous phase suspension is removed, followed by immersing the surface of the PSF ultrafiltration membrane in the TMC n-hexane solution in step (3) for 1 min, and then removing the residual n-hexane solution; the remaining conditions remain unchanged.

[0083] Example 6:

[0084] A preparation method of a high-permeability composite nanofiltration membrane based on mercapto-UiO-66, which is different from example 5 in that in step (4), the concentration of the mercapto-UiO-66-DMSA nanomaterial in the aqueous phase suspension is 0.04 w / v%, and the remaining conditions remain unchanged.

[0085] Example 7:

[0086] A preparation method of a high-permeability composite nanofiltration membrane based on mercapto-UiO-66, which is different from example 5 in that in step (4), the concentration of the mercapto-UiO-66-DMSA nanomaterial in the aqueous phase suspension is 0.06 w / v%, and the remaining conditions remain unchanged.

[0087] Example 8:

[0088] A preparation method of a high-permeability composite nanofiltration membrane based on mercapto-UiO-66, which is different from example 5 in that in step (4), the concentration of the mercapto-UiO-66-DMSA nanomaterial in the aqueous phase suspension is 0.08 w / v%, and the remaining conditions remain unchanged.

[0089] Example 9:

[0090] (1) 20 mL of 2,5-dimercaptoterephthalic acid DMF solution with a concentration of 0.1 mmol / mL is mixed with 20 mL of ZrCl4 DMF solution with a concentration of 0.1 mmol / mL, 6 mL of glacial acetic acid is added and mixed, and then placed in a 120°C oven for constant temperature reaction for 12 hours;

[0091] (2) After the reaction is completed, the obtained suspension containing mercapto-UiO-66 nanomaterial is centrifuged to separate the solid, and the obtained solid is washed with DMF and anhydrous ethanol for 3 times respectively, and dried in a 65°C oven to obtain mercapto-UiO-66-(SH)2 nanomaterial;

[0092] (3) preparing PIP aqueous solution with a concentration of 1 wt.% and TMC n-hexane solution with a concentration of 0.15 w / v.%;

[0093] (4) ultrasonic dispersion of thiol-UiO-66-(SH)2 nanomaterial with a concentration of 0.02 w / v.% in the TMC n-hexane solution obtained in step (3) to obtain a TMC n-hexane organic phase suspension containing thiol-UiO-66-(SH)2;

[0094] (5) after the PIP aqueous solution in step (3) is immersed on the surface of the PSF ultrafiltration membrane for 3 min, the residual aqueous solution is removed, and then the TMC n-hexane organic phase suspension containing thiol-UiO-66-(SH)2 in step (4) is immersed on the surface of the PSF ultrafiltration membrane for 1 min, and the residual n-hexane organic phase suspension is removed;

[0095] (6) the membrane obtained in step (5) is heat treated at 65°C for 10 min, and after washing with n-hexane, a thiol-UiO-66-(SH)2 high-permeability composite nanofiltration membrane is obtained.

[0096] Example 10:

[0097] A preparation method of a thiol-UiO-66 high-permeability composite nanofiltration membrane, which is different from example 9 in that in step (4), the concentration of thiol-UiO-66-(SH)2 nanomaterial in the organic phase suspension is 0.04 w / v%, and the rest of the conditions remain unchanged.

[0098] Example 11:

[0099] A preparation method of a thiol-UiO-66 high-permeability composite nanofiltration membrane, which is different from example 9 in that in step (4), the concentration of thiol-UiO-66-(SH)2 nanomaterial in the organic phase suspension is 0.06 w / v%, and the rest of the conditions remain unchanged.

[0100] Example 12:

[0101] A preparation method of a thiol-UiO-66 high-permeability composite nanofiltration membrane, which is different from example 9 in that in step (4), the concentration of thiol-UiO-66-(SH)2 nanomaterial in the organic phase suspension is 0.08 w / v%, and the rest of the conditions remain unchanged.

[0102] Example 13:

[0103] A preparation method of a high permeability composite nanofiltration membrane based on mercapto-UiO-66, which is different from example 9 in that: in step (4), the mercapto-UiO-66-(SH)2 nanomaterial with a concentration of 0.02 w / v% is ultrasonically dispersed in the PIP aqueous solution obtained in step (3) to obtain a piperazine aqueous phase suspension containing mercapto-UiO-66-(SH)2; in step (5), the PSF ultrafiltration membrane surface is immersed in the piperazine aqueous phase suspension containing mercapto-UiO-66-(SH)2 of step (4) for 3 min, then the residual aqueous phase suspension is removed, and then the PSF ultrafiltration membrane surface is immersed in the TMC n-hexane solution in step (3) for 1 min, and then the residual n-hexane solution is removed; the other conditions remain unchanged.

[0104] Example 14:

[0105] A preparation method of a high permeability composite nanofiltration membrane based on mercapto-UiO-66, which is different from example 13 in that: in step (4), the concentration of mercapto-UiO-66-(SH)2 nanomaterial in the aqueous phase suspension is 0.04 w / v%, and the other conditions remain unchanged.

[0106] Example 15:

[0107] A preparation method of a high permeability composite nanofiltration membrane based on mercapto-UiO-66, which is different from example 13 in that: in step (4), the concentration of mercapto-UiO-66-(SH)2 nanomaterial in the aqueous phase suspension is 0.06 w / v%, and the other conditions remain unchanged.

[0108] Example 16:

[0109] A preparation method of a high permeability composite nanofiltration membrane based on mercapto-UiO-66, which is different from example 13 in that: in step (4), the concentration of mercapto-UiO-66-(SH)2 nanomaterial in the aqueous phase suspension is 0.08 w / v%, and the other conditions remain unchanged.

[0110] Comparative example:

[0111] A preparation method of a composite nanofiltration membrane, comprising the following steps:

[0112] (1) preparing a PIP aqueous solution with a concentration of 1 wt% and a TMC n-hexane solution with a concentration of 0.15 w / v%;

[0113] (2) immersing the PSF ultrafiltration membrane surface in the PIP aqueous solution for 3 min, then removing the residual aqueous solution, then immersing the PSF ultrafiltration membrane surface in the TMC n-hexane solution for 60 s, and then removing the residual organic solution;

[0114] (3) The membrane obtained in step (2) is heat-treated at 65°C for 10 min and then washed with n-hexane to obtain a composite nanofiltration membrane.

[0115] Performance testing

[0116] In this invention, the permeation flux and retention performance of the composite nanofiltration membranes prepared in each embodiment and comparative example were tested using an aqueous solution of Na₂SO₄. Specifically, the desalination performance and water flux were tested using a 1 g / L single-component Na₂SO₄ aqueous solution under a driving pressure of 0.4 MPa, and the concentrations of salt in the feed solution and permeate were measured using a conductivity meter. The test results are shown in Table 1.

[0117] Table 1. Test results of permeation flux and Na2SO4 retention performance of composite nanofiltration membrane

[0118]

[0119] like Figure 1 and Figure 2 As shown, the thiol-UiO-66-DMSA and thiol-UiO-66-(SH)2 nanomaterials prepared according to the method of the present invention both exhibit good uniformity and their particle sizes are not significantly different, being 68.52±6.73 nm and 76.97±8.49 nm, respectively, thus eliminating the influence of the two thiol-UiO-66 particle sizes on the subsequent composite nanofiltration membrane performance. Figure 3 and Figure 4 As shown, the BET pore size distribution test results indicate that the average pore sizes of mercapto-UiO-66-DMSA and mercapto-UiO-66-(SH)2 are respectively... and Therefore, based on the small pore size of both, the prepared composite nanofiltration membrane can retain solutes with particle sizes larger than the MOF pore size.

[0120] As shown in Table 1, all examples (1-16) and the comparative examples exhibit a Na2SO4 retention capacity of over 95%. Regarding membrane flux, all examples (1-16) show varying degrees of improvement compared to the comparative examples, with example 16 reaching 21.16 L·m⁻¹. -2 ·h -1 Compared with the control, this represents an improvement of 47.66%. This indicates that introducing mercapto-UiO-66 nanomaterials into the composite nanofiltration membrane provides a pathway for water molecule transport and promotes the improvement of membrane permeability.

[0121] In addition, to further investigate the retention performance of the prepared composite nanofiltration membrane for ions of similar size, composite nanofiltration membranes with the same amount of thiol-UiO-66 added and meeting the requirement of a Na2SO4 retention rate of more than 97% were selected, namely Examples 3, 7, 11, 15 and the comparative example, to carry out retention experiments of Cu(NO3)2, CuSO4, MgCl2 and LiCl salt solutions. The test results are shown in Table 2.

[0122] Table 2. Test results of separation performance of composite nanofiltration membrane

[0123]

[0124] The test results in Table 2 show that, compared with the comparative examples, Examples 3, 7, 11, and 15 all exhibited varying degrees of improvement in the retention performance of the four salts. For MgCl2 retention, the rate increased from 66.35% in the comparative example to 97.62% in Example 11. For LiCl retention, the rate increased from 19.9% ​​in the comparative example to 44.60% in Example 11.

[0125] To further determine the effective pore size distribution of the composite nanofiltration membrane, positron annihilation lifetime testing was conducted. For example... Figure 5 As shown, the aperture diameters in the comparative examples are concentrated in... Average aperture diameter is The aperture diameter in Example 3 is concentrated in Average aperture diameter is The aperture diameter of Example 11 is concentrated in Average aperture diameter is First, the average pore size of the introduced mercapto-UiO-66 is highly consistent with the average pore size of the polyamide layer, thus eliminating the influence of MOF pore size on the separation accuracy of the polyamide layer. On the other hand, based on... Figure 5 The test results show that the polyamide layer prepared by adding mercapto-UiO-66 has a narrower pore size distribution and a relatively smaller effective pore size, which can achieve precise separation according to different ion sizes. A review of previous research (Nature Communications, 2020, 11, 2015) indicates that Mg... 2+ Cu 2+ and Li + The Stokes diameters are respectively and Therefore, combining Figure 5 The test results show that Examples 3 and 11 can achieve retention rates of over 91% and 97% for Cu(NO3)2 and MgCl2, respectively, and a retention rate of less than 45% for LiCl. + / Mg 2+The high permeability composite nanofiltration membrane based on thiol-UiO-66 obtained in Example 3 and Example 11 has excellent separation performance for MgCl2 and LiCl with a separation ratio of up to 20 or more. It is illustrated that when thiol-UiO-66 is ultrasonically dispersed in a trimesoyl chloride n-hexane solution, the obtained high permeability composite nanofiltration membrane based on thiol-UiO-66 has high selectivity for Li + / Mg 2+ The selectivity is up to 20 or more, and Mg 2+ and Li + ions with similar hydrated ionic radii can be separated with high selectivity.

[0126] The present application successfully prepares a high permeability composite nanofiltration membrane by introducing thiol-UiO-66 into an interfacial polymerization process, wherein the prepared high permeability composite nanofiltration membrane has high Li + / Mg 2+ selectivity, and can be used in the field of lithium extraction from salt lake brine.

[0127] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a high-permeability composite nanofiltration membrane based on thiol-UiO-66, characterized in that, Includes the following steps: (1) Using zirconium chloride solution as the metal source, a dicarboxylic acid containing thiol as the organic ligand, a monocarboxylic acid as the particle size regulator, and water or N,N-dimethylformamide as the reaction solvent, the mixed solution was reacted at a certain temperature for a certain time using a solvothermal synthesis method to obtain a suspension containing thiol-UiO-66 nanomaterials; wherein, the dicarboxylic acid containing thiol is one of 2-mercaptosuccinic acid, 2,3-dimercaptosuccinic acid, and 2,5-dimercaptoterephthalic acid; (2) The suspension containing mercapto-UiO-66 nanomaterials obtained in step (1) is centrifuged, washed with reaction solvent and alcohol solvent respectively, and then dried in an oven at a certain temperature to obtain mercapto-UiO-66 nanomaterials. (3) Prepare a piperazine aqueous solution of a certain concentration and a pyromellitic trimethylol chloride hexane solution of a certain concentration; (4) A certain concentration of mercapto-UiO-66 nanomaterials is ultrasonically dispersed in the piperazine aqueous solution or pyromellitic trimethylol chloride n-hexane solution in step (3) to obtain a corresponding phase suspension containing mercapto-UiO-66; (5) After soaking the surface of the polysulfone ultrafiltration membrane in piperazine aqueous solution for a certain period of time, remove the residual aqueous solution; then soak the surface of the polysulfone ultrafiltration membrane in a suspension of hexane containing mercapto-UiO-66 pyromellitic trichlorohexane for a certain period of time, and remove the residual hexane organic phase suspension. Alternatively, the surface of the polysulfone ultrafiltration membrane is impregnated with a piperazine aqueous suspension containing mercapto-UiO-66 for a certain period of time, and then the residual aqueous suspension is removed; subsequently, the surface of the polysulfone ultrafiltration membrane is soaked in a pyromellitic chlorohexane solution for a certain period of time, and then the residual hexane solution is removed. (6) The membrane obtained in step (5) is heat-treated at a certain temperature for a certain time and then cleaned with n-hexane solvent to obtain a mercapto-UiO-66 high-permeability composite nanofiltration membrane.

2. The method for preparing a high-permeability composite nanofiltration membrane based on thiol-UiO-66 according to claim 1, characterized in that, In step (1), the concentration of zirconium chloride solution is 0.01~0.1 mmol / mL; the concentration of dicarboxylic acid containing thiol group is 0.1~10 mmol / mL; the monocarboxylic acid is one of formic acid or glacial acetic acid, and its volume ratio with the reaction solvent is 3:20~100.

3. The method for preparing a high-permeability composite nanofiltration membrane based on thiol-UiO-66 according to claim 1, characterized in that, In step (1), the reaction temperature is 100~140℃ and the reaction time is 10~14 hours.

4. The method for preparing a high-permeability composite nanofiltration membrane based on thiol-UiO-66 according to claim 1, characterized in that, In step (2), the alcohol solvent is either methanol or ethanol, and the washing is performed 3 to 5 times, with the oven temperature being 60 to 70°C.

5. The method for preparing a high-permeability composite nanofiltration membrane based on thiol-UiO-66 according to claim 1, characterized in that, In step (3), the concentration of the piperazine aqueous solution is 0.8-1.2 wt%, and the concentration of the pyromellitic chlorohexane solution is 0.1-0.2 w / v.

6. The method for preparing a high-permeability composite nanofiltration membrane based on thiol-UiO-66 according to claim 1, characterized in that, In step (4), the concentration of mercapto-UiO-66 in the corresponding phase suspension is 0.02 to 0.08 w / v.

7. The method for preparing a high-permeability composite nanofiltration membrane based on thiol-UiO-66 according to claim 1, characterized in that, In step (5), the time for impregnating the surface of the polysulfone ultrafiltration membrane with piperazine aqueous solution or piperazine aqueous suspension containing mercapto-UiO-66 is 2~5 min; the time for immersing the surface of the polysulfone ultrafiltration membrane with trimesoyl chloride n-hexane solution or trimesoyl chloride n-hexane organic suspension containing mercapto-UiO-66 is 0.5~1 min.

8. The method for preparing a high-permeability composite nanofiltration membrane based on thiol-UiO-66 according to claim 1, characterized in that, In step (6), the heat treatment temperature is 60~70℃ and the heat treatment time is 8~12 min.

9. A high-permeability composite nanofiltration membrane based on thiol-UiO-66, characterized in that, The composite nanofiltration membrane was prepared using the method described in any one of claims 1 to 8 for preparing a high-permeability composite nanofiltration membrane based on thiol-UiO-66.

10. The high-permeability composite nanofiltration membrane based on thiol-UiO-66 according to claim 9, characterized in that, The obtained thiol-UiO-66 high-permeability composite nanofiltration membrane achieved a Na2SO4 brine flux of 13.90–21.16 L·m⁻¹ at a pressure of 0.4 MPa. -2 ·h -1 The rejection rate of Na2SO4 is over 95%.

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