Preparation method of positively charged acid-resistant nanocomposite nanofiltration membrane

Abstract

The application discloses a preparation method of a positively charged acid-resistant nanocomposite nanofiltration membrane, and comprises the following steps: an in-situ hydrothermal method is used to treat a precursor solution containing a molybdenum source, a sulfur source and an amino compound, so that the amino modification of MoS2 is completed in the process of preparing MoS2, and amino-modified MoS2 nanoparticles are obtained; the amino-modified MoS2 nanoparticles are made into amino-modified MoS2 nanosheets; the amino-modified MoS2 nanosheets and polyethyleneimine are added into water to prepare an aqueous solution; an oil-phase monomer is added into an organic solvent to prepare an oil-phase solution; a polymer ultrafiltration membrane is first immersed in the aqueous solution and then immersed in the oil-phase solution, and interfacial polymerization is carried out; finally, heat treatment is carried out, so that an amino-modified MoS2 / poly-sulfamide composite nanofiltration membrane is obtained. The preparation method provided by the application is simple to operate and does not need special reagents; the prepared composite nanofiltration membrane has excellent nanofiltration separation performance, also shows excellent acid-resistant stability, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology and relates to a method for preparing a positively charged acid-resistant nanocomposite nanofiltration membrane, specifically a method for preparing an aminated MoS2 / polysulfonamide composite nanofiltration membrane. Background Technology

[0002] With industrial development, mining and metallurgy industries generate large amounts of acidic wastewater. Due to its high content of metal ions such as Mg, Fe, and Cu, as well as a large amount of inorganic acids, the harmless treatment of acidic wastewater still faces significant challenges. Nanofiltration membrane separation technology, as a novel separation and purification technology, offers advantages over traditional methods such as neutralization, precipitation, and adsorption, including low energy consumption, high efficiency, and no secondary pollution. It holds promising application prospects for resource recovery from acidic industrial wastewater and is of great significance for improving the utilization of water and metal resources.

[0003] Currently, commercially available nanofiltration membranes such as NF-270, Desal 5DK, and NE-40 mostly use polyamide as the separation layer material. Their preparation process is simple and they offer excellent separation performance, but the amide bonds are easily affected by H+ in acidic environments. + Degradation occurs due to acid attack, leading to damage to the membrane structure and affecting separation performance. Commercially available acid-resistant nanofiltration membranes such as Desal KH and AMS A-3012, which have good acid resistance, generally have low water flux and are difficult to improve in terms of separation efficiency.

[0004] Introducing nanofillers into the separation layer to construct rapid mass transfer channels is an effective strategy for improving the water flux of nanofiltration membranes. Molybdenum disulfide (MoS2) is a two-dimensional nanomaterial with a sandwich structure, possessing high lateral dimensions, atomic-level thickness, ultra-high specific surface area, high mechanical strength, excellent swelling resistance and chemical stability, and clean 2D channels, making it considered an excellent nanofiller.

[0005] Patent CN114210215A discloses a nanofilm composite membrane based on molybdenum disulfide oil phase doping. MoS2 powder is ultrasonically dispersed in a hexane solution of trimesoyl chloride (TMC), followed by interfacial polymerization (IP) with an aqueous piperazine (PIP) solution to obtain a composite nanofiltration membrane with good separation performance. However, on the one hand, because the surface of MoS2 nanosheets is smooth and lacks any functional groups, its compatibility with polymers is poor, causing the nanosheets to easily shift under external forces, thus reducing the stability of the composite nanofiltration membrane. On the other hand, the surface of MoS2 nanosheets is hydrophobic, resulting in poor dispersibility. Therefore, researchers have employed various methods to modify the functional groups of MoS2.

[0006] Patent CN113368688A discloses a two-dimensional nanocomposite membrane of oxidized MoS2. MoS2 nanosheets are oxidized using reagents such as sulfuric acid, potassium permanganate, and hydrogen peroxide, and then ultrasonically exfoliated to obtain hydrophilic O-MoS2 nanosheets. A composite nanofiltration membrane is then prepared via interfacial polymerization, achieving simultaneous improvement in water flux and selectivity. Zhu et al. sulfonated MoS2 powder using toluene and 1,3-propanesulfonyl lactone, and after stirring at 110°C for 24 hours, obtained hydrophilic S-MoS2 nanosheets. These were then doped into a PIP aqueous solution and reacted with a TMC solution via an IP reaction to obtain an S-MoS2 composite nanofiltration membrane, which simultaneously improved water flux and separation selectivity (J.Membr.Sci.,2023,676,121574). Wang et al. first prepared COOH-MoS2 nanoparticles using a chemical conjugation method. They then converted the carboxyl groups in the COOH-MoS2 nanoparticles into acyl chloride groups using thionyl chloride to synthesize acyl chloride@MoS2 nanoparticles. After exfoliation, they obtained hydrophilic acyl chloride@MoS2 nanosheets, which were then doped into a TMC solution and reacted with PIP aqueous solution to obtain an acyl chloride@MoS2 composite nanofiltration membrane, achieving a simultaneous improvement in water flux and selectivity (Sep. Purif. Technol., 2020, 604, 118052).

[0007] However, existing technologies for hydrophilic modification of MoS2 nanosheets require the use of chemical reagents such as toluene, sulfuric acid, and potassium permanganate, and the procedures are complex and time-consuming. Secondly, most of the prepared composite membranes are composite nanofiltration membranes with polyamide as the separation layer, prepared based on the IP reaction of PIP and TMC. Their amide bonds are easily affected by H+ in acidic environments. + Degradation due to attack by metals disrupts the membrane structure, affecting separation performance. Furthermore, the composite nanofiltration membrane prepared by the IP reaction based on PIP and TMC exhibits a negative surface charge, resulting in poor Donnan effect for high-valence metal ions and consequently poor retention performance. Therefore, introducing hydrophilic MoS2 nanosheets into interfacial polymerization membranes to prepare positively charged, acid-resistant nanocomposite nanofiltration membranes remains a challenge. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for preparing a positively charged, acid-resistant nanocomposite nanofiltration membrane.

[0009] This invention discloses a method for preparing a positively charged, acid-resistant nanocomposite nanofiltration membrane, comprising:

[0010] An in-situ hydrothermal method was used to treat a precursor solution containing a molybdenum source, a sulfur source, and an amino compound, thereby simultaneously modifying the amino group of MoS2 during the preparation of MoS2 to obtain aminated MoS2 nanoparticles; and the aminated MoS2 nanoparticles were then fabricated into aminated MoS2 nanosheets.

[0011] Aminated MoS2 nanosheets and polyethyleneimine were added to water to prepare an aqueous solution; an oil phase monomer was added to an organic solvent to prepare an oil phase solution; a polymer ultrafiltration membrane was first immersed in the aqueous solution and then immersed in the oil phase solution for interfacial polymerization; finally, heat treatment was performed to obtain an aminated MoS2 / polysulfonamide composite nanofiltration membrane.

[0012] As a further improvement of the present invention, the in-situ hydrothermal treatment of the precursor solution containing a molybdenum source, a sulfur source, and an amino compound simultaneously modifies the amino group of MoS2 during the preparation of MoS2, yielding aminated MoS2 nanoparticles; including:

[0013] A molybdenum source and a sulfur source were added sequentially to deionized water at a mass ratio of 1:1 to 1:5 and stirred thoroughly to obtain a solution with a concentration of 7.0 to 9.0 wt%. An amino compound with a mass ratio of 1:2 to 1:10 to the molybdenum source was added to the solution and stirred thoroughly to obtain a precursor solution.

[0014] The precursor solution was transferred into a polytetrafluoroethylene liner, sealed, and placed in a stainless steel reactor. The reaction was carried out at a constant temperature of 100℃ to 300℃ for 10 to 50 hours. After naturally cooling to room temperature, the MoS2 nanoparticles were centrifuged out and washed with deionized water and ethanol alternately to obtain aminated MoS2 nanoparticles.

[0015] As a further improvement of the present invention, the step of forming aminated MoS2 nanoparticles into aminated MoS2 nanosheets includes:

[0016] Aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.1–0.5 wt%. The suspension was sonicated for 2–4 h and then centrifuged at 3000–10000 rpm. The supernatant was collected and dried to obtain aminated MoS2 nanosheets.

[0017] As a further improvement of the present invention, the step of adding aminated MoS2 nanosheets and polyethyleneimine to water to prepare an aqueous solution; and adding an oil phase monomer to an organic solvent to prepare an oil phase solution; comprises:

[0018] Aminated MoS2 nanosheets and polyethyleneimine were added sequentially to deionized water at a mass ratio of 1:200 to 3:200, and stirred thoroughly to obtain an aqueous solution with a total concentration of 0.5 to 5.0 wt%.

[0019] The oil phase monomer is added to an organic solvent and stirred thoroughly to obtain an oil phase solution with a total concentration of 0.1–0.3 wt%.

[0020] As a further improvement of the present invention, the polymer ultrafiltration membrane is first immersed in the aqueous phase solution, then immersed in the oil phase solution for interfacial polymerization; finally, it is heat-treated to obtain an aminated MoS2 / polysulfonamide composite nanofiltration membrane; comprising:

[0021] After thorough cleaning, the polymer ultrafiltration membrane is immersed in an aqueous solution for 1–10 minutes and then removed. After the surface moisture is allowed to air dry naturally, it is immersed in an oil solution for interfacial polymerization for 1–10 minutes. Finally, the polymerized composite membrane is placed in an oven and heat-treated at 30–100°C for 10–30 minutes to obtain an aminated MoS2 / polysulfonamide composite nanofiltration membrane.

[0022] As a further improvement of the present invention, the molybdenum source is a molybdate compound, including one or more of ammonium molybdate and sodium molybdate; the sulfur source is a sulfur-containing compound, including one or more of thiourea, L-cysteine, and ammonium sulfide.

[0023] As a further improvement of the present invention, the amino compound is mainly an amino-containing compound, including one or more of polyethyleneimine, m-phenylenediamine, p-phenylenediamine, diethylenetriamine, and piperazine.

[0024] As a further improvement of the present invention, the polymer ultrafiltration membrane includes one or more of polysulfone, polyethersulfone, and polyvinylidene fluoride.

[0025] As a further improvement of the present invention, the oil phase monomer is mainly an organic compound containing a polysulfonyl chloride structure, including one or more of 1,3-benzene disulfonyl chloride and 1,3,5-benzene trisulfonyl chloride.

[0026] As a further improvement of the present invention, the organic solvent includes one or more of n-hexane, n-heptane, and cyclohexane.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention employs an in-situ hydrothermal method to prepare aminated MoS2 nanoparticles in one step, allowing for direct exfoliation of nanosheets in deionized water. This process effectively avoids the use of hazardous chemicals during the modification and exfoliation of MoS2 nanosheets, and reduces the exfoliation time. The introduction of amino groups increases the dispersibility of MoS2 nanosheets in the aqueous monomer phase, and the amino groups can also react with the oil monomer phase, reducing defects in the separation layer and thus improving the nanofiltration performance of the composite nanofiltration membrane. Due to the good chemical stability of MoS2, the composite nanofiltration membrane exhibits good acid stability when used for separation in acidic systems. The preparation method provided by this invention is simple to operate and requires no special reagents. The prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane demonstrates excellent nanofiltration separation performance and excellent acid resistance, showing promising application prospects. Attached Figure Description

[0029] Figure 1 The zeta potential is that of the aminated MoS2 / polysulfonamide composite nanofiltration membrane prepared in Example 1 of this invention.

[0030] Figure 2 The images show surface scanning electron microscope (SEM) images of the aminated MoS2 / polysulfonamide composite nanofiltration membrane prepared in Example 2 of this invention and the MoS2 nanocomposite nanofiltration membrane prepared in the comparative example; wherein, (a) is the MoS2 / polysulfonamide composite nanofiltration membrane and (b) is the aminated MoS2 / polysulfonamide composite nanofiltration membrane.

[0031] Figure 3 The nanofiltration performance of the aminated MoS2 / polysulfonamide composite nanofiltration membranes prepared in Examples 1-8 of this invention and the MoS2 / polysulfonamide composite nanofiltration membranes prepared in the comparative examples is presented.

[0032] Figure 4 The acid stability of the aminated MoS2 / polysulfonamide composite nanofiltration membrane prepared in Example 2 of this invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The present invention will now be described in further detail with reference to the accompanying drawings:

[0035] This invention provides a method for preparing a positively charged, acid-resistant nanocomposite nanofiltration membrane, wherein the positively charged, acid-resistant nanocomposite nanofiltration membrane is an aminated MoS2 / polysulfonamide composite nanofiltration membrane, and the preparation method specifically includes:

[0036] Step 1: In-situ hydrothermal growth of aminated MoS2 and preparation of its nanosheets:

[0037] A molybdenum source and a sulfur source were added sequentially to deionized water at a mass ratio of 1:1 to 1:5 and stirred thoroughly to obtain a solution with a concentration of 7.0 to 9.0 wt%. An amino compound with a mass ratio of 1:2 to 1:10 to the molybdenum source was added to the solution and stirred thoroughly to obtain a precursor solution. The precursor solution was transferred to a polytetrafluoroethylene liner, sealed, and placed in a stainless steel reactor. The reaction was carried out at a constant temperature of 100℃ to 300℃ for 10 to 50 hours. After natural cooling to room temperature, the MoS2 nanoparticles were centrifuged and washed alternately with deionized water and ethanol to obtain aminated MoS2 nanoparticles. The aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.1 to 0.5 wt%. The suspension was sonicated for 2 to 4 hours and then centrifuged at 3000 to 10000 rpm. The supernatant was collected and thoroughly dried to obtain aminated MoS2 nanosheets. Among them, the molybdenum source is a molybdate compound, including one or more of ammonium molybdate and sodium molybdate; the sulfur source is a sulfur-containing compound, including one or more of thiourea, L-cysteine, and ammonium sulfide; the amino compound is mainly an amino-containing compound, including one or more of polyethyleneimine, m-phenylenediamine, p-phenylenediamine, diethylenetriamine, and piperazine.

[0038] Step 2: Preparation of aminated MoS2 / polysulfonamide composite nanofiltration membrane:

[0039] Aminated MoS2 nanosheets and polyethyleneimine were added sequentially to deionized water at a mass ratio of 1:200 to 3:200 and stirred thoroughly to obtain an aqueous solution with a total concentration of 0.5 to 5.0 wt%. Oil phase monomers were added to an organic solvent and stirred thoroughly to obtain an oil phase solution with a total concentration of 0.1 to 0.3 wt%. The thoroughly cleaned polymer ultrafiltration membrane was immersed in the aqueous solution for 1 to 10 minutes and then removed. After the surface moisture was allowed to air dry naturally, it was immersed in the oil phase solution for interfacial polymerization for 1 to 10 minutes. Finally, the polymerized composite membrane was placed in an oven and heat-treated at 30 to 100°C for 10 to 30 minutes to obtain an aminated MoS2 / polysulfonamide composite nanofiltration membrane. The polymer ultrafiltration membrane includes one or more of polysulfone, polyethersulfone, and polyvinylidene fluoride; the oil phase monomer is mainly an organic compound containing a polysulfonyl chloride structure, including one or more of 1,3-benzenedisulfonyl chloride and 1,3,5-benzenetrisulfonyl chloride; the organic solvent includes one or more of n-hexane, n-heptane, and cyclohexane.

[0040] Comparative Examples

[0041] A method for preparing a MoS2 / polysulfonamide composite nanofiltration membrane, comprising:

[0042] (1) Preparation of MoS2 and its nanosheets by in-situ hydrothermal growth

[0043] First, ammonium molybdate and thiourea (mass ratio 1:2) were added sequentially to deionized water and stirred thoroughly to prepare a precursor solution with a concentration of 8.0 wt%. Then, the precursor solution was transferred to a polytetrafluoroethylene liner, sealed, and placed in a stainless steel reactor. The reactor was reacted at 220°C for 30 hours. After natural cooling to room temperature, the MoS2 nanoparticles were centrifuged and cleaned alternately with deionized water and ethanol to obtain the MoS2 nanoparticles.

[0044] The MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.2 wt%. After ultrasonic treatment for 2 hours, the suspension was centrifuged at 7000 rpm for 10 minutes. The supernatant was collected and thoroughly dried to obtain MoS2 nanosheets.

[0045] (2) Preparation of MoS2 / polysulfonamide composite nanofiltration membrane

[0046] First, the MoS2 nanosheets prepared in step (1) and polyethyleneimine were added sequentially to deionized water at a mass ratio of 3:200 and stirred thoroughly to obtain an aqueous solution with a total concentration of 2.0 wt%. Next, 1,3-benzenedisulfonyl chloride was added to n-hexane and stirred thoroughly to obtain an oil solution with a total concentration of 0.15 wt%. Then, the polyethersulfone ultrafiltration membrane was immersed in the aqueous solution for 5 minutes, removed, and allowed to air dry naturally before being immersed in the oil solution for interfacial polymerization for 2 minutes. Finally, the composite membrane was placed in an oven and heat-treated at 60°C for 15 minutes to obtain the MoS2 / polysulfonamide composite nanofiltration membrane.

[0047] The nanofiltration performance of the prepared MoS2 / polysulfonamide composite nanofiltration membrane was tested in a cross-flow nanofiltration unit. The test conditions were: feed solution of 1.0 g / L MgCl2 aqueous solution, test at room temperature, and pressure of 0.4 MPa. The test results showed that the prepared MoS2 / polysulfonamide composite nanofiltration membrane had a MgCl2 rejection rate of 82.1% and a water flux of 93.5 L·m³. -2 ·h -1 ·MPa -1 .

[0048] Example 1

[0049] A method for preparing an aminated MoS2 / polysulfonamide composite nanofiltration membrane, comprising:

[0050] (1) Preparation of aminated MoS2 and its nanosheets by in-situ hydrothermal growth

[0051] First, sodium molybdate and thiourea (mass ratio 1:2) were sequentially added to deionized water and stirred thoroughly to prepare an 8.0 wt% aqueous solution. Polyethyleneimine (mass ratio 1:5 to sodium molybdate) was then added and stirred until homogeneous, yielding a precursor solution. Next, the precursor solution was transferred to a polytetrafluoroethylene (PTFE) liner, sealed, and placed in a stainless steel reactor. The reactor was reacted at 220°C for 30 hours. After natural cooling to room temperature, the MoS2 nanoparticles were centrifuged and cleaned alternately with deionized water and ethanol to obtain aminated MoS2 nanoparticles.

[0052] The aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.2 wt%. After ultrasonic treatment for 2 hours, the suspension was centrifuged at 7000 rpm for 10 minutes. The supernatant was collected and thoroughly dried to obtain aminated MoS2 nanosheets.

[0053] (2) Preparation of aminated MoS2 / polysulfonamide composite nanofiltration membrane

[0054] First, the aminated MoS2 nanosheets prepared in step (1) and polyethyleneimine were added sequentially to deionized water at a mass ratio of 1:200 and stirred thoroughly to obtain an aqueous solution with a total concentration of 2.0 wt%. Next, 1,3-benzenesulfonyl chloride was added to n-hexane and stirred thoroughly to obtain an oil solution with a total concentration of 0.15 wt%. Then, the polyethersulfone ultrafiltration membrane was immersed in the aqueous solution for 5 minutes, removed, and allowed to air dry naturally before being immersed in the oil solution for interfacial polymerization for 2 minutes. Finally, the composite membrane was placed in an oven and heat-treated at 60°C for 15 minutes to obtain the aminated MoS2 / polysulfonamide composite nanofiltration membrane; wherein, the Zeta potential of the aminated MoS2 / polysulfonamide composite nanofiltration membrane is as follows: Figure 1 As shown.

[0055] The prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The test conditions were: feed solution of 1.0 g / L MgCl2 aqueous solution, test at room temperature, and pressure of 0.4 MPa. The test results showed that the prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane had a MgCl2 rejection rate of 94.4% and a water flux of 46.4 L·m³. -2 ·h -1 ·MPa -1 .

[0056] Example 2

[0057] A method for preparing an aminated MoS2 / polysulfonamide composite nanofiltration membrane, comprising:

[0058] (1) Preparation of aminated MoS2 and its nanosheets by in-situ hydrothermal growth

[0059] First, sodium molybdate and thiourea (mass ratio 1:2) were sequentially added to deionized water and stirred thoroughly to prepare an 8.0 wt% aqueous solution. Polyethyleneimine (mass ratio 1:5 to sodium molybdate) was then added and stirred until homogeneous, yielding a precursor solution. Next, the precursor solution was transferred to a polytetrafluoroethylene (PTFE) liner, sealed, and placed in a stainless steel reactor. The reactor was reacted at 220°C for 30 hours. After natural cooling to room temperature, the MoS2 nanoparticles were centrifuged and cleaned alternately with deionized water and ethanol to obtain aminated MoS2 nanoparticles.

[0060] The aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.4 wt%. After ultrasonic treatment for 2 hours, the suspension was centrifuged at 7000 rpm for 10 minutes. The supernatant was collected and thoroughly dried to obtain aminated MoS2 nanosheets.

[0061] (2) Preparation of aminated MoS2 / polysulfonamide composite nanofiltration membrane

[0062] First, the aminated MoS2 nanosheets prepared in step (1) and polyethyleneimine were added sequentially to deionized water at a mass ratio of 2:200 and stirred thoroughly to obtain an aqueous solution with a total concentration of 2.0 wt%. Next, 1,3-benzenedisulfonyl chloride was added to n-hexane and stirred thoroughly to obtain an oil solution with a total concentration of 0.15 wt%. Then, the polyethersulfone ultrafiltration membrane was immersed in the aqueous solution for 5 minutes, removed, and allowed to air dry naturally before being immersed in the oil solution for interfacial polymerization for 2 minutes. Finally, the composite membrane was placed in an oven and heat-treated at 60°C for 15 minutes to obtain the aminated MoS2 / polysulfonamide composite nanofiltration membrane.

[0063] The prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The test conditions were: feed solution was 1.0 g / L MgCl2 aqueous solution, test was conducted at room temperature, and pressure was 0.4 MPa. The test results showed that the prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane had a MgCl2 rejection rate of 93.7% and a water flux of 84.8 L·m⁻¹. -2 ·h -1 ·MPa -1 .

[0064] Example 3

[0065] A method for preparing an aminated MoS2 / polysulfonamide composite nanofiltration membrane, comprising:

[0066] (1) Preparation of aminated MoS2 and its nanosheets by in-situ hydrothermal growth

[0067] First, sodium molybdate and thiourea (mass ratio 1:2) were sequentially added to deionized water and stirred thoroughly to prepare an 8.0 wt% aqueous solution. Polyethyleneimine (mass ratio 1:5 to sodium molybdate) was then added and stirred until homogeneous, yielding a precursor solution. Next, the precursor solution was transferred to a polytetrafluoroethylene (PTFE) liner, sealed, and placed in a stainless steel reactor. The reactor was reacted at 220°C for 30 hours. After natural cooling to room temperature, the MoS2 nanoparticles were centrifuged and cleaned alternately with deionized water and ethanol to obtain aminated MoS2 nanoparticles.

[0068] The aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.2 wt%. After ultrasonic treatment for 2 hours, the suspension was centrifuged at 7000 rpm for 10 minutes. The supernatant was collected and thoroughly dried to obtain aminated MoS2 nanosheets.

[0069] (2) Preparation of aminated MoS2 / polysulfonamide composite nanofiltration membrane

[0070] First, the aminated MoS2 nanosheets prepared in step (1) and polyethyleneimine were added sequentially to deionized water at a mass ratio of 3:200 and stirred thoroughly to obtain an aqueous solution with a total concentration of 2.0 wt%. Next, 1,3-benzenedisulfonyl chloride was added to n-hexane and stirred thoroughly to obtain an oil solution with a total concentration of 0.15 wt%. Then, the polyethersulfone ultrafiltration membrane was immersed in the aqueous solution for 5 minutes, removed, and allowed to air dry naturally before being immersed in the oil solution for interfacial polymerization for 2 minutes. Finally, the composite membrane was placed in an oven and heat-treated at 60°C for 15 minutes to obtain the aminated MoS2 / polysulfonamide composite nanofiltration membrane.

[0071] The prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The test conditions were: feed solution of 1.0 g / L MgCl2 aqueous solution, test at room temperature, and pressure of 0.4 MPa. The test results showed that the prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane had a MgCl2 rejection rate of 94.6% and a water flux of 80.1 L·m³. -2 ·h -1 ·MPa -1 .

[0072] Example 4

[0073] A method for preparing an aminated MoS2 / polysulfonamide composite nanofiltration membrane, comprising:

[0074] (1) Preparation of aminated MoS2 and its nanosheets by in-situ hydrothermal growth

[0075] First, sodium molybdate and thiourea (mass ratio 1:2) were sequentially added to deionized water and stirred thoroughly to prepare an 8.0 wt% aqueous solution. Then, m-phenylenediamine (mass ratio 1:10 to sodium molybdate) was added and stirred until homogeneous, yielding a precursor solution. Next, the precursor solution was transferred to a polytetrafluoroethylene (PTFE) liner, sealed, and placed in a stainless steel reactor. The reactor was reacted at 220°C for 30 hours. After natural cooling to room temperature, the MoS2 nanoparticles were centrifuged and cleaned alternately with deionized water and ethanol to obtain aminated MoS2 nanoparticles.

[0076] The aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.3 wt%. After ultrasonic treatment for 2 hours, the suspension was centrifuged at 7000 rpm for 10 minutes. The supernatant was collected and thoroughly dried to obtain aminated MoS2 nanosheets.

[0077] (2) Preparation of aminated MoS2 / polysulfonamide composite nanofiltration membrane

[0078] First, the aminated MoS2 nanosheets prepared in step (1) and polyethyleneimine were added sequentially to deionized water at a mass ratio of 2:200 and stirred thoroughly to obtain an aqueous solution with a total concentration of 2.0 wt%. Next, 1,3-benzenedisulfonyl chloride was added to n-hexane and stirred thoroughly to obtain an oil solution with a total concentration of 0.15 wt%. Then, the polyethersulfone ultrafiltration membrane was immersed in the aqueous solution for 5 minutes, removed, and allowed to air dry naturally before being immersed in the oil solution for interfacial polymerization for 2 minutes. Finally, the composite membrane was placed in an oven and heat-treated at 60°C for 15 minutes to obtain the aminated MoS2 / polysulfonamide composite nanofiltration membrane.

[0079] The prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The test conditions were: feed solution was a 1.0 g / L MgCl2 aqueous solution, test at room temperature, and pressure of 0.4 MPa. The test results showed that the prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane had a MgCl2 rejection rate of 88.6% and a water flux of 86.3 L·m³. -2 ·h -1 ·MPa -1 .

[0080] Example 5

[0081] A method for preparing an aminated MoS2 / polysulfonamide composite nanofiltration membrane, comprising:

[0082] (1) Preparation of aminated MoS2 and its nanosheets by in-situ hydrothermal growth

[0083] First, sodium molybdate and L-cysteine ​​(mass ratio 1:2) were sequentially added to deionized water and stirred thoroughly to prepare an 8.0 wt% aqueous solution. Then, m-phenylenediamine (mass ratio 1:10 to sodium molybdate) was added and stirred until homogeneous, yielding a precursor solution. Next, the precursor solution was transferred to a polytetrafluoroethylene (PTFE) liner, sealed, and placed in a stainless steel reactor. The reactor was reacted at 220°C for 30 hours. After natural cooling to room temperature, the MoS2 nanoparticles were centrifuged and cleaned alternately with deionized water and ethanol to obtain aminated MoS2 nanoparticles.

[0084] The aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.1 wt%. After ultrasonic treatment for 2 hours, the suspension was centrifuged at 7000 rpm for 10 minutes. The supernatant was collected and thoroughly dried to obtain aminated MoS2 nanosheets.

[0085] (2) Preparation of aminated MoS2 / polysulfonamide composite nanofiltration membrane

[0086] First, the aminated MoS2 nanosheets prepared in step (1) and polyethyleneimine were added sequentially to deionized water at a mass ratio of 3:200 and stirred thoroughly to obtain an aqueous solution with a total concentration of 2.0 wt%. Next, 1,3-benzenedisulfonyl chloride was added to n-hexane and stirred thoroughly to obtain an oil solution with a total concentration of 0.15 wt%. Then, the polyethersulfone ultrafiltration membrane was immersed in the aqueous solution for 5 minutes, removed, and allowed to air dry naturally before being immersed in the oil solution for interfacial polymerization for 2 minutes. Finally, the composite membrane was placed in an oven and heat-treated at 60°C for 15 minutes to obtain the aminated MoS2 / polysulfonamide composite nanofiltration membrane.

[0087] The prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The test conditions were: feed solution was 1.0 g / L MgCl2 aqueous solution, test was conducted at room temperature, and pressure was 0.4 MPa. The test results showed that the prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane had a MgCl2 rejection rate of 92.5% and a water flux of 78.8 L·m³. -2 ·h -1 ·MPa -1 .

[0088] Example 6

[0089] A method for preparing an aminated MoS2 / polysulfonamide composite nanofiltration membrane, comprising:

[0090] (1) Preparation of aminated MoS2 and its nanosheets by in-situ hydrothermal growth

[0091] First, sodium molybdate and thiourea (mass ratio 1:2) were added sequentially to deionized water and stirred thoroughly to prepare an 8.0 wt% aqueous solution. Then, piperazine was added at a mass ratio of 1:7 to sodium molybdate.

[0092] Continue stirring until homogeneous to obtain a precursor solution. Then, transfer the precursor solution to a polytetrafluoroethylene liner, seal it, and place it in a stainless steel reactor. React at a constant temperature of 220℃ for 30 hours. After naturally cooling to room temperature, centrifuge to remove MoS2 nanoparticles, and wash them alternately with deionized water and ethanol to obtain aminated MoS2 nanoparticles.

[0093] The aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.2 wt%. After ultrasonic treatment for 2 hours, the suspension was centrifuged at 7000 rpm for 10 minutes. The supernatant was collected and thoroughly dried to obtain aminated MoS2 nanosheets.

[0094] (2) Preparation of aminated MoS2 / polysulfonamide composite nanofiltration membrane

[0095] First, the aminated MoS2 nanosheets prepared in step (1) and polyethyleneimine were added sequentially to deionized water at a mass ratio of 2:200 and stirred thoroughly to obtain an aqueous solution with a total concentration of 2.0 wt%. Next, 1,3-benzenedisulfonyl chloride was added to n-hexane and stirred thoroughly to obtain an oil solution with a total concentration of 0.15 wt%. Then, the polyethersulfone ultrafiltration membrane was immersed in the aqueous solution for 5 minutes, removed, and allowed to air dry naturally before being immersed in the oil solution for interfacial polymerization for 2 minutes. Finally, the composite membrane was placed in an oven and heat-treated at 60°C for 15 minutes to obtain the aminated MoS2 / polysulfonamide composite nanofiltration membrane.

[0096] The prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The test conditions were: feed solution was 1.0 g / L MgCl2 aqueous solution, test was conducted at room temperature, and pressure was 0.4 MPa. The test results showed that the prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane had a MgCl2 rejection rate of 92.8% and a water flux of 75.6 L·m³. -2 ·h -1 ·MPa -1 .

[0097] Example 7

[0098] A method for preparing an aminated MoS2 / polysulfonamide composite nanofiltration membrane, comprising:

[0099] (1) Preparation of aminated MoS2 and its nanosheets by in-situ hydrothermal growth

[0100] First, sodium molybdate and thiourea (mass ratio 1:2) were added sequentially to deionized water and stirred thoroughly to prepare an 8.0 wt% aqueous solution. Then, piperazine was added in a mass ratio of 1:3 to sodium molybdate.

[0101] Continue stirring until homogeneous to obtain a precursor solution. Then, transfer the precursor solution to a polytetrafluoroethylene liner, seal it, and place it in a stainless steel reactor. React at a constant temperature of 220℃ for 30 hours. After naturally cooling to room temperature, centrifuge to remove MoS2 nanoparticles, and wash them alternately with deionized water and ethanol to obtain aminated MoS2 nanoparticles.

[0102] The aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.5 wt%. After ultrasonic treatment for 2 hours, the suspension was centrifuged at 7000 rpm for 10 minutes. The supernatant was collected and thoroughly dried to obtain aminated MoS2 nanosheets.

[0103] (2) Preparation of aminated MoS2 / polysulfonamide composite nanofiltration membrane

[0104] First, the aminated MoS2 nanosheets prepared in step (1) and polyethyleneimine were added sequentially to deionized water at a mass ratio of 3:200 and stirred thoroughly to obtain an aqueous solution with a total concentration of 2.0 wt%. Next, 1,3-benzenedisulfonyl chloride was added to n-hexane and stirred thoroughly to obtain an oil solution with a total concentration of 0.15 wt%. Then, the polyethersulfone ultrafiltration membrane was immersed in the aqueous solution for 5 minutes, removed, and allowed to air dry naturally before being immersed in the oil solution for interfacial polymerization for 2 minutes. Finally, the composite membrane was placed in an oven and heat-treated at 60°C for 15 minutes to obtain the aminated MoS2 / polysulfonamide composite nanofiltration membrane.

[0105] The prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The test conditions were: feed solution was a 1.0 g / L MgCl2 aqueous solution, test was conducted at room temperature, and pressure was 0.4 MPa. The test results showed that the prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane had a MgCl2 rejection rate of 85.3% and a water flux of 91.2 L·m³. -2 ·h -1 ·MPa -1 .

[0106] Example 8

[0107] A method for preparing an aminated MoS2 / polysulfonamide composite nanofiltration membrane, comprising:

[0108] (1) Preparation of aminated MoS2 and its nanosheets by in-situ hydrothermal growth

[0109] First, sodium molybdate and thiourea (mass ratio 1:2) were sequentially added to deionized water and stirred thoroughly to prepare an 8.0 wt% aqueous solution. Then, p-phenylenediamine (mass ratio 1:8 to sodium molybdate) was added and stirred until homogeneous, yielding a precursor solution. Next, the precursor solution was transferred to a polytetrafluoroethylene (PTFE) liner, sealed, and placed in a stainless steel reactor. The reactor was reacted at 220°C for 30 hours. After natural cooling to room temperature, the MoS2 nanoparticles were centrifuged and cleaned alternately with deionized water and ethanol to obtain aminated MoS2 nanoparticles.

[0110] The aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.4 wt%. After ultrasonic treatment for 2 hours, the suspension was centrifuged at 7000 rpm for 10 minutes. The supernatant was collected and thoroughly dried to obtain aminated MoS2 nanosheets.

[0111] (2) Preparation of aminated MoS2 / polysulfonamide composite nanofiltration membrane

[0112] First, the aminated MoS2 nanosheets prepared in step (1) and polyethyleneimine were added sequentially to deionized water at a mass ratio of 2:200 and stirred thoroughly to obtain an aqueous solution with a total concentration of 2.0 wt%. Next, 1,3-benzenedisulfonyl chloride was added to n-hexane and stirred thoroughly to obtain an oil solution with a total concentration of 0.15 wt%. Then, the polyethersulfone ultrafiltration membrane was immersed in the aqueous solution for 5 minutes, removed, and allowed to air dry naturally before being immersed in the oil solution for interfacial polymerization for 2 minutes. Finally, the composite membrane was placed in an oven and heat-treated at 60°C for 15 minutes to obtain the aminated MoS2 / polysulfonamide composite nanofiltration membrane.

[0113] The prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The test conditions were: feed solution of 1.0 g / L MgCl2 aqueous solution, test at room temperature, and pressure of 0.4 MPa. The test results showed that the prepared aminated MoS2 / polysulfonamide composite nanofiltration membrane had a MgCl2 rejection rate of 89.7% and a water flux of 86.7 L·m³. -2 ·h -1 ·MPa -1 .

[0114] in conclusion:

[0115] The introduction of amino groups increases the dispersibility of MoS2 nanosheets in the aqueous monomer phase, and the amino groups can also react with the oil monomer phase, reducing defects in the separation layer (e.g., Figure 2 As shown); thereby improving the nanofiltration separation performance of the composite membrane (e.g. Figure 3 (As shown). The composite membrane prepared in Example 2 had a MgCl2 rejection rate of 93.7% and a water flux of 84.8 L·m. -2 ·h -1 ·MPa -1 Compared with the comparative example, the MgCl2 rejection rate was increased by 11.6%.

[0116] Because MoS2 has good chemical stability, the composite membrane exhibits good acid stability when used for separation in acidic systems (e.g., Figure 4 As shown in the figure, after soaking in 20% sulfuric acid solution for 14 days, the retention rate of MgCl2 in the composite membrane decreased by only 3.7%, proving that it has excellent acid stability.

[0117] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a positively charged, acid-resistant nanocomposite nanofiltration membrane, characterized in that, include: Step 1: A precursor solution containing a molybdenum source, a sulfur source, and an amino compound is treated using an in-situ hydrothermal method to simultaneously modify the amino group of MoS2 during its preparation, yielding aminated MoS2 nanoparticles. These aminated MoS2 nanoparticles are then fabricated into aminated MoS2 nanosheets. Specifically, this includes: The molybdenum source and the sulfur source were added to deionized water in a mass ratio of 1:1 to 1:5 and stirred thoroughly to obtain a solution with a concentration of 7.0 to 9.0 wt%. An amino compound with a mass ratio of 1:2 to 1:10 to the molybdenum source was added to the solution and stirred thoroughly to obtain a precursor solution. The precursor solution was transferred into a polytetrafluoroethylene liner, sealed, and placed in a stainless steel reactor. The reaction was carried out at a constant temperature of 100℃~300℃ for 10h~50h. After naturally cooling to room temperature, the MoS2 nanoparticles were centrifuged and washed with deionized water and ethanol alternately to obtain aminated MoS2 nanoparticles. Aminated MoS2 nanoparticles were added to deionized water to prepare a suspension with a concentration of 0.1-0.5 wt%. The suspension was sonicated for 2-4 hours and then centrifuged at 3000-10000 rpm. The supernatant was collected and dried to obtain aminated MoS2 nanosheets. The molybdenum source is a molybdate compound, including one or more of ammonium molybdate and sodium molybdate; the sulfur source is a sulfur-containing compound, including one or more of thiourea, L-cysteine, and ammonium sulfide; the amino compound is an amino-containing compound, including one or more of polyethyleneimine, m-phenylenediamine, p-phenylenediamine, diethylenetriamine, and piperazine. Step 2: Aminated MoS2 nanosheets and polyethyleneimine are added to water to prepare an aqueous solution; an oil-phase monomer is added to an organic solvent to prepare an oil-phase solution; a polymer ultrafiltration membrane is first immersed in the aqueous solution, then in the oil-phase solution, for interfacial polymerization; finally, heat treatment is performed to obtain an aminated MoS2 / polysulfonamide composite nanofiltration membrane; wherein, the step of immersing the polymer ultrafiltration membrane first in the aqueous solution, then in the oil-phase solution, for interfacial polymerization, and finally heat treatment to obtain the aminated MoS2 / polysulfonamide composite nanofiltration membrane includes: After thorough cleaning, the polymer ultrafiltration membrane is immersed in an aqueous solution for 1-10 minutes and then removed. After the surface moisture is allowed to air dry naturally, it is immersed in an oil solution for interfacial polymerization for 1-10 minutes. Finally, the polymerized composite membrane is placed in an oven and heat-treated at 30-100°C for 10-30 minutes to obtain an aminated MoS2 / polysulfonamide composite nanofiltration membrane. The oil phase monomer is an organic compound containing a polysulfonyl chloride structure, including one or more of 1,3-benzenedisulfonyl chloride and 1,3,5-benzenetrisulfonyl chloride.

2. The method for preparing the positively charged acid-resistant nanocomposite nanofiltration membrane as described in claim 1, characterized in that, The step of adding aminated MoS2 nanosheets and polyethyleneimine to water to prepare an aqueous solution, and adding an oil phase monomer to an organic solvent to prepare an oil phase solution, comprises: Aminated MoS2 nanosheets and polyethyleneimine were added sequentially to deionized water at a mass ratio of 1:200 to 3:200, and stirred thoroughly to obtain an aqueous solution with a total concentration of 0.5 to 5.0 wt%. The oil phase monomer is added to the organic solvent and stirred thoroughly to obtain an oil phase solution with a total concentration of 0.1~0.3wt%.

3. The method for preparing the positively charged acid-resistant nanocomposite nanofiltration membrane according to any one of claims 1 to 2, characterized in that, The polymer ultrafiltration membrane includes one or more of polysulfone, polyethersulfone, and polyvinylidene fluoride.

4. The method for preparing the positively charged acid-resistant nanocomposite nanofiltration membrane according to any one of claims 1 to 2, characterized in that, The organic solvent includes one or more of n-hexane, n-heptane, and cyclohexane.

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