Molybdenum sulfide reinforced ultrasonic-assisted phase inversion membrane and preparation method and application thereof

Abstract

The application relates to a molybdenum sulfide quantum dot doped crosslinked ethyl cellulose film prepared by a molybdenum sulfide enhanced ultrasonic assisted phase inversion method and a preparation method and application thereof. The film is a high porosity, uniform porous sponge-like film structure, and the preparation comprises the following steps: (1) putting a proper amount of ethyl cellulose raw material into a polar aprotic solvent to prepare an ethyl cellulose solution; (2) putting a dialdehyde reagent and molybdenum sulfide into the solution and stirring uniformly to prepare a molybdenum sulfide / crosslinked ethyl cellulose casting solution; (3) using a scraper to scrape the casting solution on a support plate to form a liquid film with uniform thickness; (4) opening the ultrasonic switch of a coagulation bath, and placing the support containing the liquid film in the coagulation bath to perform molybdenum sulfide enhanced ultrasonic assisted phase inversion; (5) taking out the film, and immersing the film in water to remove residual solvents; and (6) taking out the film, and performing freeze drying to obtain the film. The molybdenum sulfide / crosslinked ethyl cellulose film has high retention rate and high flux, and can be used as a high-performance separation membrane material.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to molybdenum sulfide-enhanced ultrasound-assisted phase transformation membranes, their preparation methods, and applications. Background Technology

[0002] With rapid industrial development, the natural environment upon which humanity depends for survival has been severely damaged, especially water pollution, which has become a critical problem urgently needing to be solved. Common wastewater treatment methods include filtration, adsorbent removal, distillation, and membrane separation. Among these, membrane separation, including microfiltration, ultrafiltration, nanofiltration, pervaporation desalination, and reverse osmosis, boasts advantages such as high separation precision, simple processes, low energy consumption, and large processing capacity, and has become one of the most widely used wastewater treatment methods. With the ever-increasing demand for wastewater treatment, further improving the treatment capacity of membrane separation methods has become imperative. The key to increasing the treatment capacity of membrane separation lies in improving the preparation technology and quality of the separation membranes; therefore, the development of novel separation membrane preparation technologies has become a focus of research.

[0003] Reported membrane preparation techniques include interfacial polymerization, electrospinning, layer-by-layer (LBL) self-assembly, thermally induced phase inversion (TIPS), and non-solvent-induced phase inversion (NIPS). Among these, the NIPS method utilizes mechanisms such as nodal phase separation and binodal phase separation. It promotes macroscopic phase separation of the polymer / solvent through rapid exchange between the solvent and non-solvent, thereby forming an asymmetric thin film. This method is mature and has been used to prepare various commercial membranes, including polyacrylonitrile (PAN) membranes, polyvinylidene fluoride (PVDF) membranes, and polyethersulfone (PES) membranes. However, during NIPS phase separation, the solvent-non-solvent exchange rate is significantly affected by the compatibility between the two solvents, which severely limits the application scope of the NIPS method. Summary of the Invention

[0004] The purpose of this invention is to provide a molybdenum sulfide-enhanced ultrasound-assisted phase transition membrane, its preparation method, and its application. In this invention, two-dimensional molybdenum sulfide quantum dots sensitive to ultrasound are added to the traditional non-solvent phase transition membrane preparation process, and ultrasound of different intensities is used to assist phase separation, thereby accelerating the exchange rate between the non-solvent and solvent in the system, and thus preparing a high-performance phase-separated thin film material. This includes controlling the ultrasound intensity, i.e., ultrasound power and ultrasound frequency, and studying the relationship between the morphology, tensile strength, membrane flux, membrane rejection rate, etc., of asymmetric porous films and ultrasound conditions. Studies show that as the ultrasound power increases and the ultrasound frequency decreases, the exchange rate between the solvent and non-solvent during non-solvent phase transition is faster, which is beneficial for forming a sponge-like film structure with uniform pores and high porosity. Under ultrasound-assisted phase transition conditions of 100W / 45kHz, with a molybdenum sulfide content of 0.1wt% in the matrix, a Rhodamine B aqueous solution flux of 8574 L / (m³) can be achieved. 2 The preparation of a high-performance ethyl cellulose membrane with a retention rate of 55% (·h) was carried out. This molybdenum sulfide-reinforced ultrasonic-assisted phase inversion membrane, its preparation method, and its application will have significant implications for the development and application of wastewater treatment.

[0005] To achieve the above objectives, one of the technical solutions of the present invention is: a molybdenum sulfide-enhanced ultrasound-assisted NIPS phase transition method, specifically comprising the following steps:

[0006] (1) After dissolving the polymer in an organic solvent, a certain amount of molybdenum sulfide and crosslinking agent are added to the polymer solution to form a uniform and transparent casting solution.

[0007] (2) Use a scraper to apply the above casting liquid onto a clean support plate to form a liquid film of a certain thickness;

[0008] (3) The support plate containing a liquid film of a certain thickness is placed in a coagulation bath with adjustable ultrasonic intensity to carry out a full phase transformation and form a separation membrane material.

[0009] Further, in step (1), the polymer is a common polymer that can be used to make films using the NIPS method, such as: polysulfone, polyethersulfone, polyacrylonitrile, cellulose ester, polyimide, ethyl cellulose, polyether amide, polyether ether ketone, polyvinylidene fluoride, polytetrafluoroethylene, isotactic polypropylene, etc.; preferably, the polymer is ethyl cellulose, polyvinylidene chloride, polyimide, etc.; more preferably, ethyl cellulose.

[0010] Furthermore, in step (1), the solvent is a polar aprotic solvent that can dissolve the polymer.

[0011] Furthermore, in step (1), the crosslinking agent is a dialdehyde crosslinking reagent, which is one or a mixture of two or more of glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, etc.

[0012] Furthermore, in step (1), without adding molybdenum sulfide to the casting solution system, an ultrafiltration membrane with certain separation performance can be formed by ultrasonic-assisted / non-ultrasonic phase inversion method; preferably, adding a small amount of molybdenum sulfide to the casting solution system greatly improves the separation performance of the filter membrane formed by ultrasonic-assisted / non-ultrasonic phase inversion method; more preferably, adding molybdenum sulfide to the casting solution system to enhance and assist the ultrasonic phase inversion process can form a microfiltration membrane with better separation performance.

[0013] The molybdenum sulfide accounts for 0 to 2% of the polymer mass; preferably, the molybdenum sulfide accounts for 0.1% to 2% of the polymer mass.

[0014] Further, in step (3), the ultrasonic conditions are: ultrasonic power 0-100W, ultrasonic frequency 0-100kHz; preferably, the ultrasonic conditions are: ultrasonic power 40-100W, ultrasonic frequency 45-100kHz.

[0015] Furthermore, in step (3), the coagulation bath is one or two or more mixed solvents such as deionized water, anhydrous ethanol, and anhydrous methanol.

[0016] The second technical solution of the present invention is: a molybdenum sulfide quantum dot-doped cross-linked ethyl cellulose membrane, wherein the membrane is prepared by any of the above-mentioned molybdenum sulfide-enhanced ultrasound-assisted phase transformation methods, specifically including the following steps:

[0017] (1) Preparation of ethyl cellulose solution: An appropriate amount of ethyl cellulose raw material is added to a polar aprotic solvent to prepare an ethyl cellulose solution. The polar aprotic solvent is one or a mixture of two or more reagents such as N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide. The mass concentration of the ethyl cellulose / polar aprotic solvent solution is 2-50 wt%.

[0018] (2) Preparation of molybdenum sulfide / crosslinked ethyl cellulose casting solution: A certain amount of molybdenum sulfide and dialdehyde crosslinking agent are added to the ethyl cellulose solution obtained in step (1), and the mixture is stirred thoroughly to prepare molybdenum sulfide / crosslinked ethyl cellulose casting solution. Among them, the dialdehyde crosslinking agent is one or a mixture of two or more of glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, etc., and the mass ratio of each substance is ethyl cellulose: polar aprotic solvent: dialdehyde crosslinking agent: molybdenum sulfide = 1:2~50:0.1~5:0.001~0.020. The stirring temperature is 60±5℃, the stirring speed is 100~800 rpm, and the stirring time is 2~24h until a uniform transparent solution is formed. Then, the solution is taken out and allowed to stand at room temperature for 24~48h to degas, thus obtaining the molybdenum sulfide / crosslinked ethyl cellulose casting solution.

[0019] (3) Coating of the casting solution: Pour the casting solution described in step (2) onto a clean support plate, and use a scraper of a certain thickness to scrape the casting solution flat to form a liquid film of uniform thickness. The support plate is one of glass plate, quartz plate, polytetrafluoroethylene sheet, polyethylene terephthalate sheet, etc. The length of the support plate is 5-10 cm, the width is 5-10 cm, the volume of the poured casting solution is 10-50 mL, and the thickness of the stainless steel scraper is 50-800 μm.

[0020] (4) Molybdenum sulfide-enhanced ultrasound-assisted phase transformation process: Set the ultrasonic bath power and frequency, turn on the ultrasonic bath switch, and place the support plate containing the liquid membrane described in step (3) horizontally in the ultrasonic field containing a certain amount of coagulation bath to carry out molybdenum sulfide-enhanced ultrasound-assisted phase transformation to form a separation membrane material. Among them, the coagulation bath is one or two or more mixed solvents such as deionized water, anhydrous ethanol, and anhydrous methanol; the ultrasonic bath power is 0-100W; the ultrasonic bath frequency is 0-100kHz; the volume of the coagulation bath in the ultrasonic bath is 1-3L; and the ultrasonic time is 0-5min.

[0021] (5) Post-treatment of molybdenum sulfide quantum dot-doped crosslinked ethyl cellulose membrane: The separation membrane material from step (4) is soaked in clean deionized water for several days and repeatedly to fully displace the residual solvent in the membrane. Then, the membrane is placed in a freeze-drying oven for drying. The volume of deionized water used for soaking is 1-3 L, the soaking time is 1-2 days, the number of times is repeated is 3-5, and the freeze-drying time is 16-48 h.

[0022] To ensure the effectiveness of film formation, the support plate is cleaned before film formation. Cleaning can be carried out using conventional techniques in the field. The preferred cleaning operation of this invention is as follows: the support is ultrasonically cleaned in acetone and ethanol respectively, and then dried by blowing with nitrogen.

[0023] Preferably, the support plate is one of a glass plate and a quartz sheet, more preferably a glass plate;

[0024] Preferably, the polar aprotic solvent is one of N-methylpyrrolidone and N,N-dimethylformamide, more preferably N,N-dimethylformamide;

[0025] Preferably, the concentration of the ethyl cellulose / N,N-dimethylformamide solution is 2-50 wt%, more preferably 5-30 wt%.

[0026] Preferably, the dialdehyde crosslinking agent in the molybdenum sulfide / crosslinked ethyl cellulose casting solution is one of glyoxal and glutaraldehyde, more preferably glutaraldehyde. The preferred mass ratio of the substances is ethyl cellulose: polar aprotic solvent: dialdehyde crosslinking agent: molybdenum sulfide = 1:2-5:0.1-0.8:0.001-0.005. The solution preparation conditions are: stirring temperature 60℃, stirring speed 500-600 rpm, stirring time 2-24 h, and room temperature standing degassing time 24-48 h.

[0027] Preferably, the support body has a length of 8-10 cm and a width of 8-10 cm, the volume of the poured casting liquid is 30-50 mL, and the thickness of the stainless steel scraper is 200-500 μm.

[0028] Preferably, the coagulation bath is one of deionized water and anhydrous ethanol, the ultrasonic bath power is 40-100W, the ultrasonic bath frequency is 45-100kHz, and the volume of the coagulation bath in the ultrasonic bath is 2-3L.

[0029] Preferably, the volume of deionized water used for soaking is 2-3L, the soaking time is 2 days, the soaking is repeated 5 times, and the freeze-drying time is 24-48 hours.

[0030] Preferably, the molybdenum sulfide quantum dot-doped crosslinked ethyl cellulose membrane has a high porosity and a uniform sponge-like pore structure.

[0031] The third technical solution of the present invention is: the application of any of the above-mentioned molybdenum sulfide quantum dot-doped cross-linked ethyl cellulose membranes or molybdenum sulfide quantum dot-doped cross-linked ethyl cellulose membranes prepared by any of the above-mentioned methods in the fields of microfiltration separation, efficient heavy metal ion removal, and fuel cell membranes; preferably, the application in microfiltration separation.

[0032] The molybdenum sulfide quantum dot-doped crosslinked ethyl cellulose membrane of this invention has a main structure of biomass-based ethyl cellulose ring structure, which is environmentally friendly, uses inexpensive raw materials, has a stable framework structure, and is highly rigid. After crosslinking with dialdehyde reagents, it exhibits strong mechanical properties. The molybdenum sulfide quantum dot-doped crosslinked ethyl cellulose membrane not only undergoes chemical crosslinking modification but also hydrophilic blending modification. That is, the hydroxyl groups on the ethyl cellulose molecular chain undergo acetalization with dialdehyde reagents to form chemical crosslinking points. Molybdenum sulfide doping can be hydrophilic modified, making it easy to prepare a high-porosity, uniform sponge-like membrane with a stable framework structure, high mechanical properties, and good hydrophilicity. This provides a potential polymer material for microfiltration separation, efficient heavy metal ion removal, and fuel cell membranes.

[0033] The terms "molybdenum sulfide quantum dot-doped cross-linked ethyl cellulose membrane", "molybdenum sulfide-doped cross-linked ethyl cellulose membrane", "molybdenum sulfide / cross-linked ethyl cellulose blend membrane", and "molybdenum sulfide quantum dot / cross-linked ethyl cellulose blend membrane" in this invention refer to the same thing.

[0034] All raw materials or reagents involved in this invention are commercially available.

[0035] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined with each other to obtain various preferred embodiments of the present invention. Attached Figure Description

[0036] Figure 1 This invention relates to the cross-linked ethyl cellulose prepared by this invention, and molybdenum sulfide / cross-linked ethyl cellulose before and after ultrasonication. 1 1H NMR spectra, from bottom to top: ethyl cellulose (EC) 140 ), cross-linked ethyl cellulose (non-US X-EC) 140 ), non-ultrasonic vulcanized molybdenum / crosslinked ethyl cellulose (non-US MoS2 / X-EC) 140 ) and ultrasonically treated molybdenum sulfur / crosslinked ethyl cellulose (US-MoS2 / X-EC) 140 )of 1 H NMR spectrum;

[0037] Figure 2 These are the XRD patterns of cross-linked ethyl cellulose before and after ultrasound, molybdenum sulfide / cross-linked ethyl cellulose before and after ultrasound, and pure molybdenum sulfide prepared according to this invention. From bottom to top, they are: non-US X-EC membrane (uncross-linked ethyl cellulose membrane) 140 ), ultrasonically cross-linked ethyl cellulose membrane (US X-EC) 140 ), non-ultrasonic vulcanized molybdenum / crosslinked ethyl cellulose membrane (non-US MoS2 / X-EC) 140 ), ultrasonically treated molybdenum sulfide / crosslinked ethyl cellulose membrane (US-MoS2 / X-EC) 140 XRD pattern of pure molybdenum sulfide powder;

[0038] Figure 3 These are tensile curves of cross-linked ethyl cellulose before and after ultrasound preparation, and molybdenum sulfide / cross-linked ethyl cellulose before and after ultrasound preparation, as shown in this invention. From bottom to top, the cross-linked ethyl cellulose membrane after ultrasound preparation (US X-EC) is shown. 140 ), ultrasonically treated molybdenum sulfide / crosslinked ethyl cellulose membrane (US-MoS2 / X-EC) 140 ), non-ultrasonic crosslinked ethyl cellulose membrane (non-US X-EC) 140 ), non-ultrasonic vulcanized molybdenum / crosslinked ethyl cellulose membrane (non-US MoS2 / X-EC) 140 The stretching curve of )

[0039] Figure 4 It is the non-US X-EC prepared in Example 1. 140 SEM image of the upper surface of the phase inversion film;

[0040] Figure 5 US X-EC prepared in Example 2 140 SEM image of the upper surface of the phase inversion film;

[0041] Figure 6 It is the non-US MoS2 / X-EC prepared in Example 3 140 SEM image of the upper surface of the phase inversion film;

[0042] Figure 7 The US MoS2 / X-EC prepared in Example 4 140 SEM image of the upper surface of the phase inversion film;

[0043] Figure 8 The US MoS2 / X-EC prepared in Example 5 140 Cross-sectional SEM image of the phase transformation membrane;

[0044] Figure 9 This invention prepares non-US X-EC. 140 US X-EC 140 non-US MoS2 / X-EC 140 US MoS2 / X-EC 140 Separation performance diagram of phase inversion membrane;

[0045] Figure 10 The US MoS2 / X-EC prepared in Example 6 140 EDS energy dispersive spectroscopy (EDS) spectrum of the phase transformation film;

[0046] Figure 11 The US MoS2 / X-EC prepared in Example 7 140 EDS energy dispersive spectroscopy (EDS) spectrum of the phase transformation film;

[0047] Figure 12 It is the US MoS2 / X-EC prepared in Example 8 140 Cross-sectional SEM image of the phase transformation membrane. Detailed Implementation

[0048] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of protection claimed in the present invention. Unless otherwise specified, the operations involved in the following embodiments are conventional operations in the art.

[0049] Example 1

[0050] non-US X-EC without ultrasound 140 The preparation method of the phase transformation membrane includes the following steps:

[0051] Step 1: Weigh 10g of ethyl cellulose (purchased from Aladdin, catalog number: E110673-500g) with 140 repeating units and place it in a clean 100mL beaker. Then, measure 50mL of N,N-dimethylformamide into the beaker using a graduated cylinder. Stir thoroughly at room temperature until the system forms a homogeneous and transparent solution, thus preparing a 17.4wt% ethyl cellulose / DMF solution. Next, use a clean dropper to draw 50% glutaraldehyde crosslinking agent (density 1.063g / cm³). 3 5 mL of the solution was slowly added dropwise to the above solution, and stirred to form a homogeneous solution. The solution was then placed in a water bath at 60℃ and 600 rpm and stirred thoroughly for 24 hours. Afterward, it was removed and allowed to stand at room temperature for 48 hours to remove bubbles, thus preparing the cross-linked ethyl cellulose / DMF casting solution. The mass ratio of ethyl cellulose:DMF:glutaraldehyde was 1:4.74:0.27.

[0052] Step 2: Place a clean 10cm × 10cm glass plate on a horizontal experimental table. Slowly pour 50mL of the above casting solution. Using a 500μm thick stainless steel spatula, slowly spread the casting solution to form a uniform liquid film. Quickly and horizontally immerse the glass plate containing the liquid film into a 3L clean deionized water bath (room temperature) for a complete phase inversion for 5 minutes. Use clean tweezers to remove the floating film and soak it in another 3L of clean deionized water for 2 days, repeating the soaking process 3 times. Each time, change the clean deionized water to fully displace the residual solvent inside the film. Then, place the film in a freeze-drying oven to dry for 24 hours to prepare the non-ultrasonicated non-US X-EC. 140 Phase transformation membrane.

[0053] non-US X-EC without ultrasound 140 Phase inversion membrane and raw material ethyl cellulose, its 1 See HNMR image Figure 1 XRD pattern can be found Figure 2 See the stretch curve diagram. Figure 3 SEM image of the upper surface of the film is shown below. Figure 4 See the separation performance diagram. Figure 9 .

[0054] Example 2

[0055] Ultrasound-assisted US X-EC 140 The preparation method of the phase transformation membrane is the same as in Example 1, except that:

[0056] Step 2: Before scraping the casting solution into a uniformly thick liquid film, set the ultrasonic bath power to 80W, the ultrasonic bath frequency to 100kHz, and the volume of deionized water in the ultrasonic bath to 3L. Turn on the ultrasonic bath. After the casting solution has been scraped into a uniformly thick liquid film, quickly and horizontally immerse the glass plate containing the liquid film into the ultrasonic bath for ultrasonic phase inversion for 5 minutes.

[0057] US X-EC after ultrasound 140 The phase transformation film, its XRD pattern is shown in the figure. Figure 2 See the stretch curve diagram. Figure 3 SEM image of the upper surface of the film is shown below. Figure 5 See the separation performance diagram. Figure 9 .

[0058] Example 3

[0059] Non-US MoS2 / X-EC without ultrasound 140 The preparation method of the phase transformation membrane is the same as in Example 1, except that:

[0060] In step 1, after preparing a 17.4 wt% ethyl cellulose / DMF solution, and before adding the glutaraldehyde crosslinking agent, 10 mg of molybdenum sulfide powder (MoS2, purchased from Aladdin, catalog number: M104967-100g) was weighed and added to the above solution, wherein the ratio of ethyl cellulose:DMF:glutaraldehyde:molybdenum sulfide = 1:4.74:0.27:0.001 (mass ratio). The amounts of each substance used were: 10 g ethyl cellulose, 50 mL DMF, 5 mL glutaraldehyde, and 10 mg molybdenum sulfide.

[0061] Non-US MoS2 / X-EC without ultrasound 140 Phase transformation membrane, its 1 See HNMR image Figure 1 XRD pattern can be found Figure 2 See the stretch curve diagram. Figure 3 SEM image of the upper surface of the film is shown below. Figure 6 See the separation performance diagram. Figure 9 .

[0062] Depend on Figure 3 It can be seen that after adding molybdenum sulfide to the ethyl cellulose / DMF solution, the tensile modulus of the film prepared by the phase inversion method increased from 2.81 MPa to 3.622 MPa, and the elongation at break increased from 7.4% to 12.2%.

[0063] Depend on Figure 9 It can be seen that after adding molybdenum sulfide to the ethyl cellulose / DMF solution, the flux of the Rhodamine B aqueous solution in the membrane prepared by the phase inversion method increased from 5450 L / (m²) to 1000 L / (m²). 2 The efficiency was increased from 6753 L / (m³) to 6753 L / (m³).2 (h), the retention rate ranged from 15% to 22%.

[0064] Example 4

[0065] Weakly cross-linked molybdenum sulfide-enhanced ultrasound-assisted phase transition membrane US MoS2 / X-EC 140 The preparation method is the same as in Example 3, except that:

[0066] Step 2: Before scraping the casting solution into a uniformly thick liquid film, set the ultrasonic bath power to 80W, the ultrasonic bath frequency to 100kHz, and the volume of deionized water in the ultrasonic bath to 3L. Turn on the ultrasonic bath. After the casting solution has been scraped into a uniformly thick liquid film, quickly and horizontally immerse the glass plate containing the liquid film into the ultrasonic bath for ultrasonic phase inversion for 5 minutes.

[0067] US MoS2 / X-EC after ultrasound 140 Phase transformation membrane, its 1 See H NMR spectrum Figure 1 XRD pattern can be found Figure 2 SEM image of the upper surface of the film is shown below. Figure 7 .

[0068] Depend on Figure 4 , Figure 5 , Figure 6 and Figure 7 It can be seen that after adding molybdenum sulfide to the ethyl cellulose / DMF solution, the membrane prepared by further ultrasonic-assisted phase inversion has uniformly dispersed MoS2 particles inside, and the pore size of the membrane is significantly increased.

[0069] Example 5

[0070] Strongly cross-linked molybdenum sulfide-enhanced ultrasound-assisted phase transition membrane US MoS2 / X-EC 140 The preparation method is the same as in Example 4, except that:

[0071] In step 1, the ratio of ethyl cellulose: DMF: glutaraldehyde: molybdenum sulfide is 1:4.74:0.54:0.001 (mass ratio). The amounts of each substance are: 10g ethyl cellulose, 50mL DMF, 10mL glutaraldehyde, and 10mg molybdenum sulfide.

[0072] In step 2, the ultrasonic bath power is set to 100W, the ultrasonic bath frequency is 45kHz, and the volume of deionized water in the ultrasonic bath is 3L.

[0073] The tensile curve of the obtained molybdenum sulfide-enhanced ultrasound-assisted phase transformation film is shown in the figure. Figure 3 See cross-sectional SEM image. Figure 8 See the separation performance diagram. Figure 9 .

[0074] The strongly cross-linked molybdenum sulfide-enhanced ultrasound-assisted phase transition membrane USMoS2 / X-EC prepared in this embodiment 140 The tensile strength reached a maximum of 2.09 MPa, and the flux of the membrane to Rhodamine B aqueous solution was 8574 L / (m²). 2 (h), with a retention rate of 55%.

[0075] The separation performance test procedure is as follows: A uniform, defect-free membrane region is placed in an ultrafiltration cup, and a transmembrane pressure difference of 0.5 bar is applied. Pre-pressurize for 30 minutes, then record the time required to add 10 mL of water using a stopwatch. Calculate the membrane flux using the formula: J = V / (S·t), where J is the membrane's pure water flux (L·m³). -2 h -1 V is the total volume of water that permeates through a given membrane surface (L), and S is the effective overpass area of ​​the membrane during the separation test (m²). 2 The effective radius is r = 2.1 cm, and t is the time (h) for the liquid to flow through the separation membrane during a single separation test. The flux of the Rhodamine B aqueous solution is obtained, and the concentration of the filtrate is measured using an ultraviolet absorption spectrometer. The rejection rate R = (C0 - C) is then calculated. t ) / C0·100%, where R is the membrane pair (10 mg·L). -1 The rejection rate of the RB / H2O solution, C0 being the initial feed concentration (10 mg·L⁻¹). -1 ), C t The concentration of the permeate after the separation test.

[0076] Example 6

[0077] High-content molybdenum sulfide-enhanced ultrasound-assisted phase transformation membrane US MoS2 / X-EC 140 The preparation method is the same as in Example 4, except that:

[0078] In step 1, the ratio of ethyl cellulose: DMF: glutaraldehyde: molybdenum sulfide is 1:4.74:0.27:0.004 (mass ratio). The amounts of each substance are as follows: 10g ethyl cellulose, 50mL DMF, 5mL glutaraldehyde, and 40mg molybdenum sulfide.

[0079] The EDS image of the obtained molybdenum sulfide-enhanced ultrasound-assisted phase transformation film is shown in the figure. Figure 10 .

[0080] Example 7

[0081] High-content, high-ultrasound-effect molybdenum sulfide-enhanced ultrasound-assisted phase transformation membrane US MoS2 / X-EC 140 The preparation method is the same as in Example 4, except that:

[0082] In step 1, the ratio of ethyl cellulose: DMF: glutaraldehyde: molybdenum sulfide is 1:4.74:0.27:0.004 (mass ratio). The amounts of each substance are as follows: 10g ethyl cellulose, 50mL DMF, 5mL glutaraldehyde, and 40mg molybdenum sulfide.

[0083] In step 2, the ultrasonic bath power is set to 100W, the ultrasonic bath frequency is set to 100kHz, and the volume of deionized water in the ultrasonic bath is set to 3L.

[0084] The EDS image of the obtained molybdenum sulfide-enhanced ultrasound-assisted phase transformation film is shown in the figure. Figure 11 .

[0085] Example 8

[0086] A thicker, high-content, and highly ultrasonically enhanced molybdenum sulfide-reinforced ultrasound-assisted phase transition membrane, US MoS2 / X-EC. 140 The preparation method is the same as in Example 4, except that:

[0087] In step 1, the ratio of ethyl cellulose: DMF: glutaraldehyde: molybdenum sulfide is 2:4.74:0.27:0.004 (mass ratio). The amounts of each substance are as follows: 20g ethyl cellulose, 50mL DMF, 5mL glutaraldehyde, and 40mg molybdenum sulfide.

[0088] In step 2, the ultrasonic bath power is set to 100W, the ultrasonic bath frequency is set to 100kHz, and the volume of deionized water in the ultrasonic bath coagulation bath is set to 3L.

[0089] Cross-sectional SEM images of the obtained molybdenum sulfide-enhanced ultrasound-assisted phase transformation film are shown below. Figure 12 .

[0090] Thin film cross-section scanning electron microscope sample preparation: The thin film is placed in liquid nitrogen for quenching, taken out after a few seconds and cut with a glass cutter, and then sputtered with gold to obtain a thin film cross-section electron microscope sample that can be used for electron microscope inspection.

[0091] Depend on Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 It can be seen that after adding molybdenum sulfide, the membrane pore structure prepared by the further ultrasound-assisted phase transformation method is more permeable and the membrane separation performance is better. It can prepare excellent microfiltration membrane materials with high membrane porosity, lower mass transfer resistance and better hydrophilicity, and uniform sponge-like pores.

[0092] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a molybdenum sulfide quantum dot-doped crosslinked ethyl cellulose membrane, characterized in that, Specifically, the steps include the following: Step 1: Add an appropriate amount of ethyl cellulose raw material to a polar aprotic solvent to prepare an ethyl cellulose solution; Step 2: Add a certain amount of molybdenum sulfide and dialdehyde crosslinking agent to the solution obtained in Step 1, and stir evenly to prepare molybdenum sulfide / crosslinked ethyl cellulose casting solution, and let it stand to remove bubbles; the molybdenum sulfide accounts for 0.1%~2% of the polymer mass; Step 3: Pour the casting liquid obtained in Step 2 onto a clean support plate, and use a scraper of a certain thickness to smooth the casting liquid to form a liquid film of uniform thickness. Step 4: Turn on the ultrasonic switch of the coagulation bath, place the support plate of the liquid-containing membrane from Step 3 horizontally in the coagulation bath, and perform molybdenum sulfide enhanced ultrasonic-assisted phase transformation to form a separation membrane material. Step 5: Take out the film obtained in step 4 and repeatedly soak it in deionized water for a period of time to fully replace the solvent in the film. Step 6: Take out the film obtained in step 5 and freeze-dry it to obtain a molybdenum sulfide quantum dot-doped crosslinked ethyl cellulose film.

2. The method according to claim 1, characterized in that, The ultrasonic conditions are: ultrasonic power 40-100W, ultrasonic frequency 45-100 kHz.

3. The method according to claim 1, characterized in that, The polar aprotic solvent is N-methylpyrrolidone or N,N-dimethylformamide; and / or The dialdehyde crosslinking agent is glyoxal or glutaraldehyde; and / or The coagulation bath is deionized water or anhydrous ethanol.

4. The method according to claim 1, characterized in that, The concentration of the ethyl cellulose / polar aprotic solvent solution is 2~50 wt%; and / or, by mass ratio, the ethyl cellulose:polar aprotic solvent:dialdehyde crosslinking agent:molybdenum sulfide = 1:2~50:0.1~5:0.001~0.

020.

5. The method according to claim 4, characterized in that, The concentration of the ethyl cellulose / polar aprotic solvent solution is 5~30 wt%; and / or, by mass ratio, the ethyl cellulose:polar aprotic solvent:dialdehyde crosslinking agent:molybdenum sulfide = 1:2~5:0.1~0.8:0.001~0.

005.

6. The method according to claim 1, characterized in that, The stirring operation in step 2 includes: stirring at a temperature of 60±5℃ and a speed of 100~800 rpm for 2~24 h; and allowing the mixture to stand for degassing for 24~48 h.

7. The method according to claim 1, characterized in that, The thickness of the scraper in step 3 is 50~800 μm.

8. The method according to claim 7, characterized in that, The thickness of the scraper in step 3 is 200~500 μm.

9. The application of the molybdenum sulfide quantum dot-doped crosslinked ethyl cellulose membrane prepared by the method of any one of claims 1 to 8 in the fields of microfiltration separation, efficient heavy metal ion removal and fuel cell membrane.

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