High-permeability composite nanofiltration membrane based on sulfydryl-UiO-66 and preparation method thereof

Abstract

The invention discloses a sulfydryl-UiO-66-based high-permeability composite nanofiltration membrane and a preparation method thereof. The preparation method comprises the following steps: (1) preparing a suspension containing sulfydryl-UiO-66 by adopting a solvothermal synthesis method; (2) carrying out centrifugal separation on the suspension in the step (1), washing and drying to obtain a sulfydryl-UiO-66 nano material; (3) preparing a PIP aqueous solution and a TMC n-hexane solution; (4) ultrasonically dispersing sulfydryl-UiO-66 with a certain concentration into a PIP aqueous solution or a TMC n-hexane solution to obtain a corresponding phase suspension; (5) soaking the surface of the PSF ultrafiltration membrane in a PIP aqueous solution or a PIP aqueous phase suspension, and then soaking the surface of the PSF ultrafiltration membrane in an n-hexane solution or an n-hexane organic phase suspension; and (6) carrying out heat treatment on the membrane obtained in the step (5), and cleaning to obtain the sulfydryl-UiO-66 high-permeability composite nanofiltration membrane. The composite nanofiltration membrane provided by the invention has high permeability, high pore structure uniformity and effective separation of cations with similar ion sizes.

Description

Technical Field

[0001] The invention relates to the technical field of nanofiltration membrane materials, and in particular to a high-permeability composite nanofiltration membrane based on mercapto-UiO-66 and a preparation method thereof. Background Art

[0002] Nanofiltration separation technology has been widely used in many fields such as printing and dyeing wastewater treatment, seawater desalination, lithium / magnesium separation, etc. Among them, the thin film composite membrane made by interfacial polymerization (IP) to form a cross-linked polyamide (PA) separation layer on a porous polymer substrate through amine monomers and acyl chloride monomers is the current mainstream nanofiltration membrane type. However, in the IP reaction, the uncontrollable diffusion of amine monomers and the rapid chemical reaction kinetics between amine monomers and acyl chloride monomers will cause the prepared PA layer structure to have a random distribution of polymer chains. The intricate and disordered stacking of PA chains undoubtedly increases the permeation resistance of water molecules, which is not conducive to the improvement of permeability performance. In addition, the pore size of nanofiltration membranes is usually around 0.5-2nm, and the molecular weight cutoff ranges from 200 to 1000Da. There is still a problem of wide pore size distribution and inability to meet the needs of ion separation of similar sizes.

[0003] Therefore, inducing the orderly arrangement of PA chains, developing nanofiltration membrane materials with concentrated pore size distribution and high permeability are still difficult problems in the preparation of nanofiltration membranes. At present, the method of effectively regulating the orderly arrangement of PA chains to achieve uniform pore size distribution can be achieved by affecting the diffusion of monomers. For example, the oil-soluble surfactant dodecyl phosphoric acid can be used to regulate the IP reaction. The amphiphilicity of dodecyl phosphoric acid enables it to be spread in the form of a monolayer at the water / oil interface, thereby promoting the diffusion of amine monomers and regulating the IP reaction. The prepared nanofiltration membrane has more uniform pores and narrower pore size distribution. In addition, the use of porous materials as the intermediate layer can not only achieve the controllable diffusion of water-phase monomers, but also its high porosity and uniform pore size can promote the uniform distribution of water-phase monomers in the intermediate layer, thereby contributing to the uniform distribution of the pore size of the PA layer. It is worth noting that the above strategies all control the IP process by slowing down the reaction or limiting the reaction to a limited space. In the experimental design, the directional arrangement of monolayer molecules at the interface and the preparation of a defect-free intermediate layer are undoubtedly more difficult. Therefore, it is urgent to develop a simple method for regulating the pore size and uniformity of the PA layer.

[0004] Metal-organic framework materials (MOFs) are one of the most promising membrane modification materials due to their unique structural diversity and rich chemical modifiability. Compared with organic polymer membrane pores, MOFs have a rigid, stable, uniform pore structure that can provide a low-resistance transmission channel for the mass transfer process. Compared with other inorganic nanoporous materials, the controllability of their size and surface chemical properties makes them more compatible with polymers. However, since MOFs mainly exist in powder form, simply mixing polymers with MOFs often results in ineffective regulation of the selective layer formation process. Specifically, the introduction of MOFs only provides additional mass transfer channels in the polymer matrix, and does not play a role in regulating the IP process and thus optimizing the PA layer structure. Summary of the invention

[0005] In order to solve the problems of low permeability and wide pore size distribution caused by disordered stacking of polymer chains in the PA separation layer of nanofiltration membranes in the prior art, and inability to achieve selective screening of ions of similar sizes, the present invention proposes a general strategy of modifying MOF particles by thiol modification, using hydrogen bonds between thiol functional groups and polymerized monomers to adjust the PA structure and narrow the pore size distribution range, and invents a high permeability composite nanofiltration membrane based on thiol-UiO-66 and a preparation method thereof. In the present invention, thiol-UiO-66 is used as a nano-additive, and it is dispersed in an aqueous phase or an organic phase to assist the interfacial polymerization reaction, and the interfacial polymerization diffusion reaction process is adjusted to achieve the effect of orderly arrangement of polymer chains in the polyamide layer of the nanofiltration membrane, reduce permeation resistance, and increase water flux, thereby preparing a composite nanofiltration membrane with high permeability and high pore structure uniformity. It is particularly pointed out that compared with traditional polyamide composite nanofiltration membranes, composite nanofiltration membranes containing thiol-UiO-66 have a better performance on Li + / Mg 2+ The selectivity is significantly improved. Therefore, the introduction of thiol-UiO-66 can not only greatly improve the permeability of the nanofiltration membrane, but also achieve the Li + / Mg 2+ effective separation.

[0006] The present invention is achieved by a method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, comprising the following steps:

[0007] (1) using zirconium chloride solution as a metal source, a dicarboxylic acid containing a thiol group as an organic ligand, a monocarboxylic acid as a particle size regulator, and water or N,N-dimethylformamide as a reaction solvent, and subjecting the mixed solution to a constant temperature reaction for a certain period of time by a solvothermal synthesis method to obtain a suspension containing a thiol-UiO-66 nanomaterial;

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

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

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

[0011] (5) After soaking the surface of a polysulfone (PSF) ultrafiltration membrane with a piperazine aqueous solution or a piperazine aqueous suspension containing thiol-UiO-66 for a certain period of time, the residual aqueous solution or aqueous suspension is removed; then, soaking the surface of a polysulfone (PSF) ultrafiltration membrane with a trimesoyl chloride n-hexane solution or a trimesoyl chloride n-hexane organic suspension containing thiol-UiO-66 for a certain period of time, the residual n-hexane solution or n-hexane organic suspension is removed;

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

[0013] The present invention selects a MOF material, namely, thiol-modified UiO-66 nanomaterial as an additive to prepare a nanofiltration membrane. In the IP process, the thiol functional group in the thiol-UiO-66 material can not only produce hydrogen bond interactions with piperazine (PIP) and trimesoyl chloride (TMC) two-phase monomers, thereby regulating the IP process to prepare a PA layer with orderly arrangement of polymer chains, but also the rigid nanoscale channels of the thiol-UiO-66 also contribute to the selective screening of solutes.

[0014] In the present invention, 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 a PIP monomer or an organic phase containing a TMC monomer to carry out an interfacial polymerization reaction, thereby realizing the preparation of a high permeability composite nanofiltration membrane. The thiol-UiO-66-based high permeability composite nanofiltration membrane prepared by the method of the present invention has higher water / salt permeability and a narrower pore size distribution range than traditional nanofiltration membranes.

[0015] The advantages of the present invention are: (1) the UiO-66 nanomaterial modified with thiol functional groups is used as an additive for the preparation of a composite nanofiltration membrane, and its inherent nanoscale channels have excellent ion screening effects; (2) since the thiol functional groups in thiol-UiO-66 can produce hydrogen bond interactions with the two-phase monomers during the IP process, the PA chains can be arranged in an orderly manner under the induction of hydrogen bonding to form a PA layer structure with uniformly distributed pore sizes.

[0016] Furthermore, in the step (1), the concentration of the zirconium chloride solution is 0.01 to 0.1 mmol / mL; the dicarboxylic acid containing a thiol group is one of 2-mercaptosuccinic acid (MSA), 2,3-dimercaptosuccinic acid (DMSA), and 2,5-dimercaptoterephthalic acid, and the concentration is 0.1 to 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 to 100.

[0017] Furthermore, 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 a thiol group 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] Furthermore, the preparation conditions of thiol-UiO-66 nanomaterials with different pore sizes and specific surface areas are different. 2 In the preparation of nanomaterials, the dicarboxylic acid containing a thiol group 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] Furthermore, in the step (1), the reaction temperature is 100 to 140° C., and the reaction time is 10 to 14 hours.

[0020] Furthermore, in the step (2), the alcohol solvent is one of methanol and ethanol, and the washing is performed 3 to 5 times respectively, and the oven temperature is 60 to 70°C.

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

[0022] Furthermore, the prepared thiol-UiO-66 nanomaterial is UiO-66-(SH) 2 When, the alcohol solvent is preferably ethanol.

[0023] Furthermore, in the 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 the step (4), the concentration of thiol-UiO-66 in the corresponding phase suspension is 0.02 to 0.08 w / v%.

[0025] Furthermore, in the step (5), the time for soaking the surface of the polysulfone ultrafiltration membrane with the piperazine aqueous solution or the piperazine aqueous suspension containing thiol-UiO-66 is 2 to 5 minutes; the time for soaking the surface of the polysulfone ultrafiltration membrane with the trimesoyl chloride n-hexane solution or the trimesoyl chloride n-hexane organic 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 min.

[0027] A high-permeability composite nanofiltration membrane based on mercapto-UiO-66 is prepared by adopting the above preparation method.

[0028] Furthermore, the obtained thiol-UiO-66 high permeability composite nanofiltration membrane has a Na 2 SO 4 The brine flux reached 13.90~21.16L·m -2 ·h -1 , to Na 2 SO 4 The interception rate is over 95%.

[0029] When thiol-UiO-66 was ultrasonically dispersed in a hexane solution of trimesoyl chloride, the resulting thiol-UiO-66 high permeability composite nanofiltration membrane had a high permeability to Li + / Mg 2+ The selectivity is as high as 20 or more, which can achieve Mg 2+ With Li + Highly selective separation of cations with similar hydrated ionic radii.

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

[0031] 1. The present invention uses the UiO-66 nanomaterial modified with thiol functional groups for the preparation of composite nanofiltration membranes, breaking the wide pore size distribution of the PA layer of the traditional nanofiltration membrane (pore size distribution: ), can only separate the boundary of monovalent / divalent anions, and prepare a narrow pore size distribution (pore size distribution: ), with high efficiency + / Mg 2+ Separation selective composite nanofiltration membrane.

[0032] 2. In the interfacial polymerization process of the present invention, the thiol-UiO-66 nanomaterial affects the polymerization process by generating hydrogen bond interactions with piperazine (PIP) and trimesoyl chloride (TMC) two-phase monomers, thereby making the polyamide chain grow in an orderly manner and making the pore size more uniform. Compared with the traditional nanofiltration membrane, the water flux is increased by 14.58-21.21%. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a scanning electron microscope image of the UiO-66-DMSA nanomaterial obtained in Example 1-8 of the present invention;

[0034] Figure 2 UiO-66-(SH) obtained in Examples 9-16 of the present invention 2 SEM images of nanomaterials;

[0035] Figure 3 This is a pore size distribution test diagram of the UiO-66-DMSA composite nanofiltration membrane obtained in Examples 1-8 of the present invention;

[0036] Figure 4 UiO-66-(SH) obtained in Examples 9-16 of the present invention 2 Pore ​​size distribution test diagram of composite nanofiltration membrane;

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

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

[0039] The embodiment of the present invention provides a method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, comprising the following steps:

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

[0041] The concentration of the zirconium chloride solution is 0.01-0.1 mmol / mL; the dicarboxylic acid containing a thiol group 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.

[0042] The conditions required for preparing thiol-UiO-66 nanomaterials with different pore sizes and specific surface areas are different. In this embodiment, for the preparation of UiO-66-DMSA nanomaterials, the dicarboxylic acid containing a thiol group 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 UiO-66-(SH) 2 In the preparation of nanomaterials, the dicarboxylic acid containing a thiol group 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°C, and the reaction time is 10-14 hours. In this embodiment, the preferred reaction temperature is 120°C, and the reaction time is 12 hours.

[0044] (2) centrifugally separating the suspension containing the thiol-UiO-66 nanomaterial obtained in step (1), washing it with a reaction solvent and an alcohol solvent respectively, and drying it in an oven at a certain temperature to obtain the thiol-UiO-66 nanomaterial;

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

[0046] (3) preparing a certain concentration of piperazine (PIP) aqueous solution and a certain concentration of trimesoyl chloride (TMC) n-hexane solution;

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

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

[0050] (5) After soaking the surface of a polysulfone (PSF) ultrafiltration membrane with a piperazine aqueous solution or a piperazine aqueous suspension containing thiol-UiO-66 for a certain period of time, the residual aqueous solution or aqueous suspension is removed; then, soaking the surface of a polysulfone (PSF) ultrafiltration membrane with a trimesoyl chloride n-hexane solution or a trimesoyl chloride n-hexane organic suspension containing thiol-UiO-66 for a certain period of time, the residual n-hexane solution or n-hexane organic suspension is removed;

[0051] The time for soaking the surface of the polysulfone ultrafiltration membrane with the piperazine aqueous solution or the piperazine aqueous suspension containing thiol-UiO-66 is 2 to 5 minutes, preferably 3 minutes in this embodiment. The time for soaking the surface of the polysulfone ultrafiltration membrane with the trimesoyl chloride n-hexane solution or the trimesoyl chloride n-hexane organic suspension containing UiO-66 is 0.5 to 1 minute, preferably 1 minute in this embodiment.

[0052] (6) The membrane obtained in step (5) is heat-treated at a certain temperature for a certain time, and then washed with a solvent to obtain a thiol-UiO-66 high permeability composite nanofiltration membrane.

[0053] The heat treatment temperature is 60-70° C., and the heat treatment time is 8-12 minutes. In this embodiment, the preferred heat treatment temperature is 65° C., and the heat treatment time is 10 minutes.

[0054] In order to better understand the above-mentioned embodiments of the present invention, they are further described below with reference to specific examples.

[0055] In the following embodiments and comparative examples:

[0056] Zirconium chloride, analytical grade, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

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

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

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

[0060] Anhydrous piperazine (PIP), analytical grade, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0061] Trimesoyl chloride (TMC), analytical grade, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0062] n-Hexane, analytical grade, was purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.;

[0063] N,N-Dimethylformamide (DMF), analytical grade, was purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.;

[0064] Glacial acetic acid, analytical grade, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

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

[0066] Polysulfone (PSF) ultrafiltration membrane, homemade in the laboratory, pure water permeation flux is 150-200 L·m -2 ·h -1 The retention rate of bovine serum albumin is 97.5-98.5%.

[0067] Embodiment 1:

[0068] A method for preparing a thiol-UiO-66 high permeability composite nanofiltration membrane comprises the following steps:

[0069] (1) Mix 5 mL of 10 mmol / mL 2,3-dimercaptosuccinic acid (DMSA) aqueous solution with 5 mL of 0.01 mmol / mL ZrCl 4 The aqueous solutions were mixed, 300 μL of formic acid was added and mixed, and then placed in a 120°C oven for constant temperature reaction for 12 hours;

[0070] (2) After the reaction is completed, the obtained suspension containing the thiol-UiO-66 nanomaterial is centrifuged, and the solid obtained by centrifugation is washed three times with water and methanol respectively, and dried in an oven at 65° C. to obtain the thiol-UiO-66-DMSA nanomaterial;

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

[0072] (4) ultrasonically dispersing the thiol-UiO-66-DMSA 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-DMSA;

[0073] (5) soaking the surface of the PSF ultrafiltration membrane with the PIP aqueous solution in step (3) for 3 minutes, removing the residual aqueous solution, and then soaking the surface of the PSF ultrafiltration membrane with the TMC n-hexane organic phase suspension containing thiol-UiO-66-DMSA in step (4) for 1 minute, and removing the residual n-hexane organic phase suspension;

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

[0075] Embodiment 2:

[0076] A method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, which is different from Example 1 in that: in step (4), the concentration of thiol-UiO-66-DMSA nanomaterial in the organic phase suspension is 0.04w / v%, and the other conditions remain unchanged.

[0077] Embodiment 3:

[0078] A method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, which is different from Example 1 in that: in step (4), the concentration of thiol-UiO-66-DMSA nanomaterial in the organic phase suspension is 0.06w / v%, and the other conditions remain unchanged.

[0079] Embodiment 4:

[0080] A method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, which is different from Example 1 in that: in step (4), the concentration of thiol-UiO-66-DMSA nanomaterial in the organic phase suspension is 0.08w / v%, and the other conditions remain unchanged.

[0081] Embodiment 5:

[0082] A preparation method based on thiol-UiO-66 high permeability composite nanofiltration membrane, which is different from Example 1 in that: in step (4), a thiol-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 suspension containing thiol-UiO-66-DMSA; in step (5), the piperazine aqueous suspension containing thiol-UiO-66-DMSA in step (4) is immersed in the surface of a PSF ultrafiltration membrane for 3 minutes, and then the residual aqueous suspension is removed, and then the surface of the PSF ultrafiltration membrane is immersed in the TMC n-hexane solution in step (3) for 1 minute, and then the residual n-hexane solution is removed; and the other conditions remain unchanged.

[0083] Embodiment 6:

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

[0085] Embodiment 7:

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

[0087] Embodiment 8:

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

[0089] Embodiment 9:

[0090] (1) Mix 20 mL of 0.1 mmol / mL 2,5-dimercaptoterephthalic acid in DMF with 20 mL of 0.1 mmol / mL ZrCl 4 100 mL of DMF solution was added, 6 mL of glacial acetic acid was 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 solid containing the thiol-UiO-66 nanomaterial is centrifuged, and the solid obtained by centrifugation is washed three times with DMF and anhydrous ethanol, respectively, and dried in an oven at 65° C. to obtain thiol-UiO-66-(SH) 2 Nanomaterials;

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

[0093] (4) Add 0.02w / v.% of thiol-UiO-66-(SH) 2 The nanomaterial is ultrasonically dispersed in the TMC n-hexane solution obtained in step (3) to obtain a thiol-UiO-66-(SH) 2 TMC hexane organic phase suspension;

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

[0095] (6) The membrane obtained in step (5) was heat treated at 65°C for 10 min, and then washed with n-hexane to obtain thiol-UiO-66-(SH) 2 High permeability composite nanofiltration membrane.

[0096] Embodiment 10:

[0097] A method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, which is different from that in Example 9 in that: in step (4), the thiol-UiO-66-(SH) 2 The concentration of nanomaterials was 0.04 w / v%, and the other conditions remained unchanged.

[0098] Embodiment 11:

[0099] A method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, which is different from that in Example 9 in that: in step (4), the thiol-UiO-66-(SH) 2 The concentration of nanomaterials was 0.06 w / v%, and the other conditions remained unchanged.

[0100] Embodiment 12:

[0101] A method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, which is different from that in Example 9 in that: in step (4), the thiol-UiO-66-(SH) 2 The concentration of nanomaterials was 0.08 w / v%, and the other conditions remained unchanged.

[0102] Embodiment 13:

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

[0104] Embodiment 14:

[0105] A method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, which is different from Example 13 in that: in step (4), the thiol-UiO-66-(SH) 2 The concentration of nanomaterials was 0.04 w / v%, and the other conditions remained unchanged.

[0106] Embodiment 15:

[0107] A method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, which is different from Example 13 in that: in step (4), the thiol-UiO-66-(SH) 2 The concentration of nanomaterials was 0.06 w / v%, and the other conditions remained unchanged.

[0108] Embodiment 16:

[0109] A method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, which is different from Example 13 in that: in step (4), the thiol-UiO-66-(SH) 2 The concentration of nanomaterials was 0.08 w / v%, and the other conditions remained unchanged.

[0110] Comparative Example:

[0111] A method for preparing a composite nanofiltration membrane comprises the following steps:

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

[0113] (2) After soaking the PSF ultrafiltration membrane surface with the PIP aqueous solution for 3 min, the residual aqueous solution was removed, and then the PSF ultrafiltration membrane surface was soaked with the TMC n-hexane solution for 60 s to remove the residual organic solution;

[0114] (3) The membrane obtained in step (2) was 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 the present invention, Na 2 SO 4 The permeation flux and interception performance of the composite nanofiltration membranes prepared in each embodiment and comparative example were tested using 1 g / L of a single component Na 2 SO 4 The desalination performance and water flux of the aqueous solution were tested at a driving pressure of 0.4 MPa, and the salt concentrations of the raw liquid and the permeate were measured using a conductivity meter. The test results are shown in Table 1.

[0117] Table 1 Composite nanofiltration membrane permeation flux and Na 2 SO 4 Retention performance test results

[0118]

[0119] like Figure 1 and Figure 2 As shown, the thiol-UiO-66-DMSA and thiol-UiO-66-(SH) prepared according to the preparation method of the present invention 2 The nanomaterials showed good uniformity and the particle sizes of the two materials were similar, 68.52±6.73nm and 76.97±8.49nm, respectively, which eliminated the influence of the particle sizes of the two thiol-UiO-66 on the performance of the subsequent composite nanofiltration membrane. Figure 3 and Figure 4 As shown in the figure, the BET pore size distribution test results show that thiol-UiO-66-DMSA and thiol-UiO-66-(SH) 2 The average pore diameters of the pores are and Therefore, based on the smaller pore sizes of the two, the prepared composite nanofiltration membrane can intercept solutes with particle sizes larger than the MOF pore size.

[0120] From the data in Table 1, we can see that for Na 2 SO 4 Retention capacity, Examples 1-16 and Comparative Examples for Na 2 SO 4All of them have a retention performance of more than 95%. As for the membrane flux, compared with the comparative example, Examples 1-16 have different degrees of improvement, among which Example 16 reaches 21.16 L·m -2 ·h -1 , which is 47.66% higher than that of the control group. This indicates that the introduction of thiol-UiO-66 nanomaterials into the composite nanofiltration membrane provides a path for the transmission of water molecules and promotes the improvement of membrane permeability.

[0121] In addition, in order to further explore the retention performance of the prepared composite nanofiltration membrane for ions of similar size, the same amount of thiol-UiO-66 was added and the retention capacity of Na 2 SO 4 The composite nanofiltration membrane with a retention rate of more than 97%, that is, Example 3, Example 7, Example 11, Example 15 and the comparative example were used to carry out Cu(NO 3 ) 2 、CuSO 4 MgCl 2 The interception experiment of LiCl salt solution is shown in Table 2.

[0122] Table 2 Composite nanofiltration membrane separation performance test results

[0123]

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

[0125] In order to further determine the effective pore size distribution of the composite nanofiltration membrane, a positron submergence lifetime test was carried out. Figure 5 As shown, the pore diameter of the comparative example is concentrated in The average pore diameter is The pore diameter of Example 3 is concentrated at The average pore diameter is The pore diameter of Example 11 is concentrated at The average pore diameter is First, the average pore size of the introduced thiol-UiO-66 is highly consistent with the average pore size of the polyamide layer, which can eliminate the influence of the MOF pore size on the separation accuracy of the polyamide layer. Figure 5The test results show that the polyamide layer prepared by adding thiol-UiO-66 has a narrower pore size distribution and a relatively small effective pore size, which can achieve precise separation according to the size of different ions. According to previous research work (Nature Communications, 2020, 11, 2015.), Mg 2+ , Cu 2+ and Li + The Stokes diameters are and Therefore, combined with Figure 5 The test results show that both Examples 3 and 11 can achieve the Cu(NO 3 ) 2 and MgCl 2 The retention rate is higher than 91% and 97%, and the retention rate of LiCl is lower than 45%. + / Mg 2+ The separation ratio is as high as 20 or more. The high permeability composite nanofiltration membrane based on thiol-UiO-66 obtained in Example 3 and Example 11 is effective for MgCl 2 It has excellent separation performance with LiCl. It shows that when thiol-UiO-66 is ultrasonically dispersed in a hexane solution of trimesoyl chloride, the obtained thiol-UiO-66 high permeability composite nanofiltration membrane has excellent separation performance for Li + / Mg 2+ The selectivity is as high as 20 or more, which can achieve Mg 2+ With Li + Highly selective separation of cations with similar hydrated ionic radii.

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

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high permeability composite nanofiltration membrane based on thiol-UiO-66, characterized in that: The steps include: (1) using zirconium chloride solution as a metal source, a dicarboxylic acid containing a thiol group as an organic ligand, a monocarboxylic acid as a particle size regulator, and water or N,N-dimethylformamide as a reaction solvent, and subjecting the mixed solution to a constant temperature reaction for a certain period of time by a solvothermal synthesis method to obtain a suspension containing a thiol-UiO-66 nanomaterial; (2) centrifugally separating the suspension containing the thiol-UiO-66 nanomaterial obtained in step (1), washing it with a reaction solvent and an alcohol solvent respectively, and drying it in an oven at a certain temperature to obtain the thiol-UiO-66 nanomaterial; (3) preparing a certain concentration of piperazine aqueous solution and a certain concentration of trimesoyl chloride n-hexane solution; (4) ultrasonically dispersing a certain concentration of thiol-UiO-66 nanomaterial in the piperazine aqueous solution or trimesoyl chloride n-hexane solution of step (3) to obtain a corresponding phase suspension containing thiol-UiO-66; (5) After soaking the surface of the polysulfone ultrafiltration membrane with a piperazine aqueous solution or a piperazine aqueous suspension containing thiol-UiO-66 for a certain period of time, the residual aqueous solution or aqueous suspension is removed; then, soaking the surface of the polysulfone ultrafiltration membrane with a trimesoyl chloride n-hexane solution or a trimesoyl chloride n-hexane organic suspension containing thiol-UiO-66 for a certain period of time, the residual n-hexane solution or n-hexane organic suspension is removed; (6) The membrane obtained in step (5) is heat-treated at a certain temperature for a certain time, and washed with n-hexane solvent to obtain a thiol-UiO-66 high permeability composite nanofiltration membrane.

2. The method for preparing a thiol-UiO-66 high permeability composite nanofiltration membrane according to claim 1, characterized in that: In the step (1), the concentration of the zirconium chloride solution is 0.01-0.1 mmol / mL; the dicarboxylic acid containing a thiol group is one of 2-mercaptosuccinic acid, 2,3-dimercaptosuccinic acid, 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.

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

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

5. The method for preparing a thiol-UiO-66 high permeability composite nanofiltration membrane according to claim 1, characterized in that: In the 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 %.

6. The method for preparing a thiol-UiO-66 high permeability composite nanofiltration membrane according to claim 1, characterized in that: In the step (4), the concentration of thiol-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 the step (5), the time for soaking the surface of the polysulfone ultrafiltration membrane with the piperazine aqueous solution or the piperazine aqueous suspension containing thiol-UiO-66 is 2 to 5 minutes; the time for soaking the surface of the polysulfone ultrafiltration membrane with the trimesoyl chloride n-hexane solution or the trimesoyl chloride n-hexane organic suspension containing UiO-66 is 0.5 to 1 minute.

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

9. A high permeability composite nanofiltration membrane based on thiol-UiO-66, characterized in that: The composite nanofiltration membrane is prepared by the preparation method of the thiol-UiO-66 high permeability composite nanofiltration membrane according to any one of claims 1 to 8.

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 has a Na2SO4 brine flux of 13.90-21.16 L·m at a pressure of 0.4 MPa. -2 ·h -1 The retention rate of Na2SO4 is over 95%.

Images