A mxene-doped silicone pervaporation dehydration membrane and a preparation method thereof

Abstract

A preparation method of an MXene-doped organosilicon pervaporation dehydration membrane, the organosilicon membrane is modified by doping MXene nanosheets in the organosilicon sol, the surface properties of the membrane are regulated by using the hydrophilic groups of the MXene nanosheets, and meanwhile, the MXene is regularly arranged in the organosilicon network to provide a fast transmission channel for water molecules, so that the pervaporation separation performance of the membrane is improved.

Description

Technical Field

[0001] This invention belongs to the field of membrane material preparation technology, specifically relating to an MXene-doped organosilicon pervaporation dehydration membrane and its preparation method. Background Technology

[0002] Alcohol / water separation is a key step in energy-intensive production. Currently, the main separation technologies include specialized distillation (azeotropic distillation, extractive distillation), molecular sieve adsorption, and membrane separation (pervaporization). Pervaporation, as a branch of membrane separation technology, has advantages such as low energy consumption, environmental friendliness, small footprint, and mild operating conditions, making it an ideal choice for the chemical and energy industries to replace traditional separation technologies (such as distillation and adsorption). Furthermore, pervaporation is not limited by vapor-liquid equilibrium, giving it a significant advantage in separating azeotropic mixtures. Organosilicon materials combine the excellent properties of organic and inorganic components, possessing advantages such as high specific surface area, adjustable pore size, good hydrothermal stability, and excellent chemical resistance. They are widely used in gas separation and organic solvent separation (reverse osmosis, pervaporation, nanofiltration, etc.), but have not yet achieved industrial application. With further research on organosilicon membranes, various modification strategies for organosilicon membranes have emerged to meet the needs of various separation systems and further improve membrane separation performance. Doping modification to control membrane pore size is a common approach. The main problems currently existing are the low separation factor and narrow applicability of BTESA silicone membranes for pervaporation dehydration of alcohol / water mixtures. Summary of the Invention

[0003] To address the issues of low separation factor and narrow applicability of BTESA silicone membranes for pervaporation dehydration of alcohol / water mixtures, this invention proposes incorporating MXene two-dimensional nanosheets into BTESA silicone sol. This optimizes the surface properties and network structure of the silicone membrane by utilizing the numerous hydrophilic groups on the MXene surface and the potential for rapid two-dimensional water molecule transport channels formed by the monolayer MXene nanosheets. This results in the preparation of a highly selective pervaporation dehydration silicone membrane.

[0004] MXene is a relatively new type of two-dimensional material. Monolayer MXene has a structure similar to graphene, but with a richer array of functional groups and tunable properties. MXene is typically prepared by selectively etching group A elements (mainly group IIIA or IVA elements) from the Mn+1AXn phase (n = 1, 2, or 3), where M is an early transition metal and X is carbon or carbon. Notably, abundant F, O, and OH functional groups are generated on the outer surface of the MXene two-dimensional nanosheet exfoliation layer during the etching and delamination process. Unlike other two-dimensional materials, the functional terminal groups in MXene are not dependent on any controlled reaction but are generated by the exfoliation process itself. The abundant functional groups in MXene can enhance the hydrophilicity of the membrane, and monolayer MXene nanosheets can be regularly stacked to produce a two-dimensional layered structure, where various Tx groups can create open, narrow nanochannels between adjacent MXene nanosheets. These advantages make MXene a promising material for preparing highly efficient separation membranes.

[0005] To achieve the objective of this invention, the membrane preparation technology solution of this invention is as follows:

[0006] An MXene-doped organosilicon pervaporation dehydration method and its preparation method are disclosed, with the following specific steps:

[0007] (1) Using BTESA as a silicon source precursor, MXene monolayer nanosheet solution was added, and hydrochloric acid was used as a catalyst. The reaction was carried out with water in ethanol solution at a reaction temperature of 40℃ and a reaction time of 2h to prepare BTESA / MXene sol.

[0008] (2) The molar ratio of each component in the organosilicon sol is BTESA:H2O:HCl = 1:

[0009] The ratio of organosilicon precursor in the synthesized organosilicon sol was 60:0.2, and the mass ratio of organosilicon precursor in the sol was 2.5 wt%. (3) Before doping the MXene monolayer nanosheet solution, it needs to be sonicated for 1-2 hours. The membrane was named BTESA / MXene-n according to the different mass ratios of MXene in the hybrid membrane.

[0010] (n=0.1%, 0.2%, 0.3%, 0.5%)

[0011] (4) The BTESA / MXene organosilicon mixed sol was coated onto a ceramic support with a silica-zirconia nano-transition layer by wiping method, and calcined at 250°C in a nitrogen atmosphere for 30 min. This process was repeated 2-3 times to prepare the BTESA / MXene organosilicon film.

[0012] (5) The silicon dioxide-zirconia transition layer is prepared by applying silicon dioxide-zirconia sol onto the ceramic support by hot coating method, calcining at 550°C for 15-20 min, and repeating the process 8-12 times.

[0013] (6) The prepared BTESA / MXene hybrid membrane was used for pervaporation dehydration tests of ethanol / water, isopropanol-water, and n-butanol / water systems, and the membrane separation performance was evaluated using permeation flux J and separation factor α.

[0014] (7) The formulas for calculating permeation flux and separation factor are as follows:

[0015]

[0016] Where J is the total permeate flux (kg m⁻²h⁻¹), Q is the mass of the permeate (kg), A is the membrane surface area (m²), and t is the permeation time (h). yi and yj are the mass fractions of components i and j in the permeate, and xi and xj are the mass fractions of components i and j in the feed solution.

[0017] The beneficial effects of this invention are as follows:

[0018] This invention provides an MXene-doped organosilicon pervaporation dehydration membrane and its preparation method. The organosilicon membrane is modified by doping MXene nanosheets into the organosilicon sol. The surface properties of the membrane are regulated by the hydrophilic groups of the MXene nanosheets. At the same time, the regular arrangement of MXene in the organosilicon network provides a fast transport channel for water molecules, thereby improving the pervaporation separation performance of the membrane. Attached Figure Description

[0019] Figure 1 Schematic diagram of the pervaporation performance of BTESA membrane and BTESA / MXene-0.2% membrane in different alcohol-water systems at 170℃;

[0020] Figure 2 Schematic diagram of Fourier transform infrared spectra of BTESA / MXene hybrid films with different MXene nanosheet contents;

[0021] Figure 3 Schematic diagram of water contact angle for BTESA / MXene hybrid films with different MXene nanosheet contents;

[0022] Figure 4 XRD patterns of BTESA / MXene hybrid films with different MXene nanosheet contents;

[0023] Figure 5 Schematic diagram of water vapor adsorption in BTESA / MXene hybrid membranes with different MXene nanosheet contents;

[0024] Figure 6 This is a schematic diagram of the surface electron microscope of BTESA / MXene hybrid films with different MXene nanosheet contents. Detailed Implementation

[0025] To make the technical features of the present invention more apparent and understandable, the following detailed description is provided in conjunction with specific embodiments of the present invention.

[0026] Example 1

[0027] (1) 0.5 g of BTESA precursor was uniformly dispersed in 17.95 g of ethanol solution. A mixed solution of 0.01 g hydrochloric acid and 1.54 g water was added at a molar ratio of BTESA:H2O:HCl = 1:60:0.2. Then, 1 ml of a 0.5 mg / ml MXene monolayer nanosheet / ethanol solution was added. The above solution was stirred and reacted in a water bath at 40 °C for 2 h to obtain a 2.5 wt% BTESA / MXene organosilicon sol.

[0028] (3) The above-mentioned BTESA / MXene mixed organosilicon sol was diluted to 0.25 wt% with ethanol solvent. To ensure the uniformity of the sol, the mixed sol was ultrasonically dispersed in an ultrasonic machine for 30 min before use. The diluted sol was applied to the prepared ceramic support with a silica-zirconia nano-transition layer by hot coating. The coated membrane was calcined in a tube furnace at 250°C with nitrogen continuously flowing through it for 30 min. This process was repeated 3 times to prepare the BTESA / MXene-0.1% hybrid membrane. The prepared membrane was used for pervaporation dehydration test of the n-butanol / water system.

[0029] Example 2

[0030] The difference between this embodiment and Embodiment 1 is that the doping amount of MXene nanosheets in step 2) is adjusted to 0.2wt%, and the volume of the MXene nanosheet doping solution in step 2) is 2ml. The remaining steps are the same as in Embodiment 1, and the film of this embodiment is obtained. This film is denoted as BTESA / MXene-0.2%.

[0031] Example 3

[0032] The difference between this embodiment and Embodiment 1 is that the doping amount of MXene nanosheets in step 2) is adjusted to 0.3wt%, and the volume of the MXene nanosheet doping solution in step 2) is 3ml. The remaining steps are the same as in Embodiment 1, and the film of this embodiment is obtained. This film is denoted as BTESA / MXene-0.3%.

[0033] Example 4

[0034] The difference between this embodiment and Embodiment 1 is that the doping amount of MXene nanosheets in step 2) is adjusted to 0.5wt%, and the volume of the MXene nanosheet doping solution in step 2) is 5ml. The remaining steps are the same as in Embodiment 1, and the film of this embodiment is obtained. This film is denoted as BTESA / MXene-0.5%.

[0035] Comparative Example 1

[0036] The difference between this comparative example and Example 1 is that no MXene material was added, and a BTESA primary membrane was prepared. BTESA sol was obtained by directly reacting the BTESA:H2O:HCl in a ratio of 1:60:0.2 at 40°C in a water bath for 2 hours. This sol was then diluted to 0.25 wt% and coated onto a support to obtain the membrane of this comparative example, which is designated as the BTESA primary membrane.

[0037] Comparative Example 2

[0038] The only difference between this comparative example and Example 1 is the coating method. The prepared BTESA / MXene sol is coated onto the surface of the support by dip-coating to obtain a BTESA / MXene-0.1% hybrid film.

[0039] Comparative Example 3

[0040] The only difference between this comparative example and Example 1 is the coating method. The prepared BTESA / MXene sol is coated onto the surface of the support by spin coating to obtain a BTESA / MXene-0.1% hybrid film.

[0041] Comparative Example 4

[0042] This embodiment is basically the same as the steps in Embodiment 1, the only difference being that the BTESA precursor is replaced with the bis(triethoxysilyl)biphenyl (BTESBPh) precursor.

[0043] The membranes prepared in Examples 1-4 and Comparative Example 1 were used for pervaporation dehydration tests on a butanol / water system. The specific implementation steps were performed according to the corresponding steps in Separation and Purification Technology, 2024, 344:12710. The feed solution composition was 95% butanol and 5% water. The feed solution temperature was controlled at 70°C. The obtained data are recorded in Table 1.

[0044] Table 1. Pervaporation and dehydration performance of BTESA / MXene membranes with different MXene doping concentrations

[0045] membrane Total flux (kgm -2 h -1 )]]> separation factor Example 1 1.21 395 Example 2 1.00 716 Example 3 1.85 370 Example 4 2.14 213 Comparative Example 1 1.85 171

[0046] As shown in Table 1, with the increase of MXene doping concentration, the flux of the BTESA / MXene hybrid matrix membrane first decreases and then increases, while the separation factor first increases and then decreases. When the MXene doping concentration is between 0.1 wt% and 0.3 wt%, the separation factor of BTESA / MXene increases, while the permeation flux decreases. According to the dissolution-diffusion mechanism, the increase in the separation factor mainly comes from the increase in dissolution selectivity and diffusion selectivity. MXene has good hydrophilicity, which can be seen from the water contact angle test characterization. Previous reports have indicated that higher hydrophilicity is more conducive to water adsorption. The doping of hydrophilic MXene increases the hydrophilicity of the membrane, making water preferentially permeate the membrane, i.e., increasing dissolution selectivity. In addition, the presence of interlayer nanochannels in MXene restricts the diffusion of water molecules and almost prevents n-butanol from passing through, improving the diffusion selectivity of the membrane, thus increasing the separation factor. However, the doping of MXene also increases the transport path of permeating molecules, which increases selectivity but also reduces flux. When the doping amount of MXene is further increased, due to the inherent compatibility issues of the mixed matrix membrane, MXene agglomerates on the membrane surface, forming non-selective defects, which leads to a decrease in the separation factor and an increase in the permeation flux.

[0047] The application system of the BTESA / MXene-0.2 mixed matrix membrane, which exhibits good separation performance, was extended to a (95 / 5wt%) ethanol / water system and a (95 / 5wt%) isopropanol / water system. Its pervaporation performance was as follows: Figure 1 As shown. From Figure 1 It can be seen that, compared with the original BTESA membrane, BTESA / MXene-0.2% significantly increased the separation factors for the ethanol / water, isopropanol / water, and n-butanol / water systems, especially for the isopropanol and n-butanol systems, where the separation factors increased by 3.4 times and 3.2 times, respectively. The flux of the ethanol / water system was not as good as the other two systems, possibly because the molecular size of ethanol is relatively small and it can form clusters with water to pass through the membrane together, increasing the difficulty of separation.

[0048] Following the aforementioned application method, the flux and separation factor of the membranes prepared in Comparative Examples 1-4 were measured at 70°C, and the results are shown in Table 2.

[0049] Table 2 shows the pervaporation dehydration performance of different membranes in the n-butanol / water (95 / 5wt%) system.

[0050] membrane Total flux (kgm -2 h -1 )]]> separation factor Example 1 1.21 395 Comparative Example 1 1.85 171 Comparative Example 2 1.16 459 Comparative Example 3 1.42 324 Comparative Example 4 1.63 286

[0051] Table 2 shows that the coating method has a significant impact on the separation performance of the BTESA / MXene hybrid membrane. This is because different coating methods result in variations in membrane thickness and uniformity. Furthermore, the choice of precursor also affects the separation performance of the hybrid membrane. BTESA / MXene hybrid membranes, due to their sterically hindered phenyl groups, have a larger specific surface area and higher flux. However, their larger pore size weakens their sieving effect on molecules, leading to a decrease in the separation factor.

[0052] The above description of the embodiments sets forth many specific details in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed above.

[0053] Secondly, the term "one embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0054] In summary, this invention provides an MXene-doped organosilicon pervaporation dehydration method and its preparation. The invention selects BTESA, a high-specific-surface-area organosilicon material with rigid acetylene bridges, as a precursor and incorporates hydrophilic MXene two-dimensional nanosheets. By constructing two-dimensional nanochannels, the diffusion selectivity for water molecules is improved, thereby enhancing the separation factor of the BTESA / MXene membrane. By optimizing the composite ratio, a composite membrane material with optimal separation performance is obtained. The optimized membrane is used for alcohol / aqueous solution separation in different systems to explore its further application possibilities.

Claims

1. A method for preparing an MXene-doped organosilicon pervaporation dehydration membrane, characterized in that, The specific steps of this preparation method are as follows: (1) Using BTESA as a silicon precursor, MXene monolayer nanosheet solution was added, and hydrochloric acid was used as a catalyst. The reaction was carried out with water in ethanol solution at a reaction temperature of 40℃ for 2 h to prepare BTESA / MXene. Organosilicon Sol, wherein the doping amount of MXene monolayer nanosheets is 0.1 wt%, 0.2 wt%, 0.3 wt%, or 0.5 wt% of BTESA mass; (2) The molar ratio of each component in the BTESA / MXene organosilicon sol is: BTESA:H2O:HCl=1: The ratio of organosilicon precursor in the synthesized BTESA / MXene organosilicon sol was 60:0.2, and the mass ratio of organosilicon precursor was 2.5 wt%. (3) Before doping the MXene monolayer nanosheet solution, sonicate for 1-2 hours; (4) BTESA / MXene organosilicon sol was coated onto a ceramic support with a silica-zirconia nano-transition layer by a wiping method, and calcined at 250°C in a nitrogen atmosphere for 30 min. This process was repeated 2-3 times to prepare a BTESA / MXene hybrid film. (5) The silica-zirconia transition layer is prepared by applying silica-zirconia sol onto the ceramic support by hot coating method, calcining at 550°C for 15-20 min, and repeating the process 8-12 times. (6) The prepared BTESA / MXene hybrid membrane was used for pervaporation dehydration tests of ethanol / water, isopropanol / water, and n-butanol / water systems, and the membrane separation performance was evaluated by using permeation flux J and separation factor α. (7) The formulas for calculating permeation flux and separation factor are as follows: Where J is the total permeation flux (kg·m). -2 .h -1 Q is the mass of the permeate (kg), and A is the membrane surface area (m²). 2 t is the infiltration time h, y i and y j x represents the mass fractions of components i and j in the permeate. i and x j It represents the mass fractions of components i and j in the raw material solution.

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