High-flux positively charged acid-resistant nanofiltration membrane, method for preparing same, and use thereof

Abstract

The application relates to a high-flux positively charged acid-resistant nanofiltration membrane, a preparation method and application thereof. The preparation method comprises the following steps: immersing an ultrafiltration base membrane into a prepared aqueous phase solution to react, drying to obtain an ultrafiltration base membrane I; immersing the ultrafiltration base membrane I into an oil phase solution to react, obtaining an ultrafiltration base membrane II; and heat treating the ultrafiltration base membrane II to obtain the high-flux positively charged acid-resistant nanofiltration membrane. The nanofiltration membrane prepared by the application has the advantages of 100%-250% flux increase under the premise of ensuring acid resistance and salt retention rate, the preparation method is simple and easy to realize industrial production, and has wide application prospects; the high-flux positively charged acid-resistant nanofiltration membrane prepared by the application improves the retention rate of multivalent cations and the acid permeation rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of membrane preparation, in particular to a high-flux positively charged acid-resistant nanofiltration membrane, a preparation method and application thereof. BACKGROUND

[0002] Nanofiltration is a membrane separation technology that has emerged in recent years. Due to its own characteristics, it has a high removal effect on organic matter with a molecular weight of 200-1000 Da, and can retain part of the ions beneficial to the human body. At present, nanofiltration has been widely used in water purification, industrial wastewater treatment and other fields. Among them, nanofiltration technology is widely used in strong acid environment, such as heavy metal recovery, acid recovery, biomass separation and water purification in strong acid to be treated liquid (industrial acid extraction waste liquid, acid cleaning liquid, electroplating industry containing acid wastewater, metal industry stripping waste acid liquid, fermentation acid wastewater, etc.), so it is necessary to prepare acid-resistant nanofiltration membrane. In order to improve the rejection rate of multivalent metal ions and the permeation rate of hydrogen ions, it is very important to prepare positively charged acid-resistant nanofiltration membrane. At present, the use of diamine and acyl chloride interfacial polymerization is a common means to prepare nanofiltration membrane (amide nanofiltration membrane), but it is not resistant to strong acid, so most acid-resistant nanofiltration membranes are negatively charged nanofiltration membranes, and the rejection rate of multivalent cations and acid permeability need to be improved, and the flux is low, only 2.0-3.0 LMH / bar. In order to improve the application value of nanofiltration membrane in acid conditions, it is necessary to prepare high-flux positively charged acid-resistant nanofiltration membrane. SUMMARY

[0003] Therefore, one of the main purposes of the present application is to provide a high-flux positively charged acid-resistant nanofiltration membrane, a preparation method and application thereof, so as to at least partially solve at least one of the above technical problems.

[0004] In order to achieve the above-mentioned purpose, as one aspect of the present application, a preparation method of a high-flux positively charged acid-resistant nanofiltration membrane is provided, which comprises the following steps:

[0005] S1: immersing an ultrafiltration base membrane into a prepared aqueous solution to react, and drying to obtain an ultrafiltration base membrane one;

[0006] S2: immersing the ultrafiltration base membrane one into an oil phase solution to react, to obtain an ultrafiltration base membrane two;

[0007] S3: heat treating the ultrafiltration base membrane two to obtain a high-flux positively charged acid-resistant nanofiltration membrane.

[0008] As another aspect of the present application, a high-flux positively charged acid-resistant nanofiltration membrane is also provided.

[0009] As a further aspect of the present application, there is also provided an application of the high-flux positively charged acid-resistant nanofiltration membrane in the field of water purification and industrial wastewater treatment.

[0010] Based on the above technical solution, the high-flux positively charged acid-resistant nanofiltration membrane, its preparation method and application of the present application have at least one of the following advantages over the prior art:

[0011] 1. The technical feature of the present application is to control the oil phase concentration and the heat treatment process, and to coat a composite functional layer with C-N bonds on the surface of the ultrafiltration base membrane by interfacial polymerization, thereby preparing a high-flux (30-150 LMH / MPa) positively charged acid-resistant nanofiltration membrane with a surface Zeta potential of 15-30 mV.

[0012] 2. The nanofiltration membrane prepared in the present application has an increased flux of 20% to 500% under the premise of ensuring acid resistance and salt retention rate, and the preparation method is simple and easy to realize industrial production, and has a wide application prospect.

[0013] 3. The high-flux positively charged acid-resistant nanofiltration membrane prepared in the present application improves the retention rate of multivalent cations and the acid permeation rate. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a comparison chart of the retention rate of the positively charged acid-resistant nanofiltration membrane in Example 1 (curve a) and the Dow NF270 nanofiltration membrane in Comparative Example 1 (curve b) for 2 g / L MgCl2 with respect to immersion time;

[0015] Figure 2 is a salt retention rate (Figure A) and acid permeation rate (Figure B) chart of the positively charged acid-resistant nanofiltration membrane in Example 1;

[0016] Figure 3 is a flux comparison chart of AMS-A3012 (a) in Comparative Example 2 and the high-flux positively charged acid-resistant nanofiltration membrane (b) in the present embodiment. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings.

[0018] The present application discloses a preparation method of a high-flux positively charged acid-resistant nanofiltration membrane, characterized in that the preparation method comprises the following steps:

[0019] S1: immerse the ultrafiltration base membrane into the prepared aqueous solution and react, and then dry to obtain ultrafiltration base membrane one;

[0020] S2: immerse the ultrafiltration base membrane one into the oil phase solution and react to obtain ultrafiltration base membrane two;

[0021] S3: heat treating the ultrafiltration base film to obtain a high-flux positively charged acid-resistant nanofiltration membrane.

[0022] In step S3, the heat treatment temperature is 20-100℃, for example 70℃, and the heat treatment time is 1-120 minutes, for example 5 minutes.

[0023] In steps S1-S3, the reaction is carried out under normal pressure.

[0024] After step S3, the membrane is rinsed with deionized water and stored in deionized water.

[0025] After step S3, the membrane is treated with citric acid, then rinsed with deionized water and stored in deionized water.

[0026] The concentration of citric acid is 2-15wt%, for example 10wt%, and the treatment time is 1-20 minutes, for example 5 minutes.

[0027] In step S1, the water phase solution is prepared by adding water phase monomer, acid binding agent and surfactant in sequence into deionized water and dispersing them evenly.

[0028] The water phase monomer is any one or a combination of polyethyleneimine, polyvinylamine, polyvinylbenzylamine, polybenzylamine, diethylene triamine and polyethylene polyamine, for example polyethyleneimine, and the molecular weight of the polyethyleneimine is 600-25000, for example 1800.

[0029] The water phase monomer A can also be a mixture of polyethyleneimine with molecular weights of 600, 1800, 10000 and 25000.

[0030] The acid binding agent is any one or several of triethylamine, pyridine, 4-dimethylaminopyridine, N,N-diisopropylethylamine, sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, for example triethylamine.

[0031] The surfactant is any one or several of commonly used surfactants such as sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, cetyl dimethyl benzyl ammonium chloride, octadecyl trimethyl ammonium chloride, trioctylmethyl ammonium chloride, benzyl triethyl ammonium chloride and tetrabutyl ammonium chloride, for example sodium dodecyl sulfonate.

[0032] The concentration of the water phase monomer is 5-25g / L, for example 10g / L.

[0033] The concentration of the acid-binding agent is 0.1-5wt%, for example, 0.5wt%;

[0034] The concentration of the surfactant is 0.02-0.08wt%, for example, 0.05wt%.

[0035] The preparation method of the oil phase solution in the step S2 is as follows: dissolving the cyanuric chloride in an organic solvent; the concentration of the cyanuric chloride is 0.01-5g / L, for example, 2g / L;

[0036] The organic solvent is any one or several of n-hexane, cyclohexane, toluene, benzene, ethyl acetate, for example, n-hexane.

[0037] In the step S1, the ultrafiltration base film is immersed in the prepared water phase solution for 2-15min, for example, 10min.

[0038] The drying method in the step S1 is air drying.

[0039] The reaction time in the step S2 is 20-500s, for example, 180s.

[0040] The reaction temperature in the step S2 is 5-45℃, for example, 10℃; the reaction humidity is 20-80%, for example, 40%.

[0041] The ultrafiltration base film is any one of polyether sulfone, polysulfone, poly-m-phenylenediamine sulfone ultrafiltration membrane, for example, polyether sulfone.

[0042] The molecular weight cut-off of the ultrafiltration base film is 30KDa-100KDa, for example, 30KDa.

[0043] The application further discloses a high-flux positively charged acid-resistant nanofiltration membrane prepared by the preparation method.

[0044] The flux of the high-flux positively charged acid-resistant nanofiltration membrane is 30-150LMH / MPa.

[0045] The surface Zeta potential of the high-flux positively charged acid-resistant nanofiltration membrane is 15-30mV.

[0046] The application further discloses an application of the high-flux positively charged acid-resistant nanofiltration membrane in the fields of water purification and industrial wastewater treatment.

[0047] In an embodiment of the application, for example, the following preparation method is used:

[0048] The application discloses a preparation method of a high-flux positively charged acid-resistant nanofiltration membrane, and belongs to the technical field of membrane preparation.

[0049] In a preferred embodiment of the application, the application adopts the following technical scheme, for example:

[0050] A preparation method of a high-flux positively charged acid-resistant nanofiltration membrane, comprising the following steps:

[0051] (1) configuring a water phase solution: 5-25 g / L of water phase monomers, 0.1-5 wt% of an acid-binding agent and 0.02-0.08 wt% of a surfactant are sequentially added into deionized water, and are uniformly dispersed to configure the water phase solution;

[0052] (2) configuring an oil phase solution: trichloro cyanuric acid is dissolved in a solution of one or more organic solvents, such as n-hexane, cyclohexane, toluene, benzene or ethyl acetate, and the concentration is 0.01-5 g / L;

[0053] (3) an interfacial polymerization process: under normal pressure, an ultrafiltration base film is immersed in the water phase solution for 2-15 min, is taken out and dried, and is then immersed in the oil phase solution for 20-500 s under the condition of 10-60 DEG C and a humidity of 30-90%;

[0054] (4) heat treatment: the membrane obtained in step (3) is subjected to heat treatment, the heat treatment temperature is 30-100 DEG C, and the treatment time is 1-120 min.

[0055] (5) citric acid treatment: the membrane obtained in step (4) is subjected to citric acid treatment, the concentration is 2-15 wt%, the treatment time is 1-20 min, and the high-flux positively charged acid-resistant nanofiltration membrane is obtained.

[0056] The water phase monomers are polyethylene imine, polyethylene amine, polyvinyl aniline, polybenzyl amine, diethylene triamine, polyethylene polyamine and other multifunctional amine substances and any combination thereof, preferably polyethylene imine, the molecular weight is 600-25000, preferably 1800, the polyethylene imine concentration is 5-25 g / L, and the concentration is preferably 10 g / L;

[0057] Further preferably, the water phase monomer is a mixture of polyethyleneimine with molecular weight of 600, 1800, 10000, 25000, etc. in mass, and the concentration is 10 g / L.

[0058] The acid-binding agent is one or more of triethylamine, pyridine, 4-dimethylaminopyridine, N, N-diisopropylethylamine, sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, preferably triethylamine, and the concentration is preferably 0.5 wt%.

[0059] The surfactant is one or more of commonly used surfactants such as sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, cetyl dimethyl benzyl ammonium chloride, octadecyl trimethyl ammonium chloride, trioctylmethyl ammonium chloride, benzyl triethyl ammonium chloride, and tetrabutyl ammonium chloride, preferably sodium dodecyl sulfonate, and the concentration is preferably 0.05 wt%.

[0060] The ultrafiltration base membrane is one of polyether sulfone, polysulfone, poly-m-phenylenediamine, etc., preferably polyether sulfone, and the molecular weight cut-off is 30-100 KDa, preferably 30 KDa.

[0061] The oil phase solvent is preferably n-hexane, and the oil phase concentration is preferably 0.01-1.5 g / L, most preferably 0.1 g / L.

[0062] The temperature in step (3) is 5-45℃, preferably 10℃, and the humidity is 20-80%, preferably 40%.

[0063] The temperature of the heat treatment is preferably 70℃, and the time is 5 min.

[0064] The concentration of citric acid is preferably 10 wt%, and the treatment time is 5 min.

[0065] The technical solutions of the present application are further described and illustrated by specific examples in combination with the accompanying drawings. It should be noted that the following specific examples are only illustrative, and the protection scope of the present application is not limited thereto.

[0066] The chemicals and raw materials used in the following examples are commercially available or self-made by known preparation methods. The molecular weight in the present application is weight average molecular weight.

[0067] Example 1

[0068] Take 5 g of polyethylene imine with a molecular weight of 1800, 1.0 g of triethylamine, 0.15 g of sodium dodecyl sulfonate, add deionized water to 500 ml, and fully disperse and stir for 12 hours; take 0.1 g of cyanuric chloride, dissolve it in 500 ml of n-hexane solvent, fully stir for 12 hours; first immerse the polyether sulfone ultrafiltration membrane soaked in deionized water in the aqueous solution for 10 min, take it out and dry, immerse it in the oil phase solution at 25°C for 2 min, and heat treat it at 30°C for 120 min, then wash it with deionized water, and measure its flux at room temperature, which is 40 LMH / MPa, measure its rejection rate to 2 g / L MgCl2, which is 91%, and its surface Zeta potential is 16 mV, immerse the high-flux positively charged acid-resistant nanofiltration membrane in 3 wt% hydrochloric acid at 25°C, and measure the curve of its rejection rate to 2 g / L MgCl2 changing with time, as shown in curve a in Figure 1 FIG. 6, the results show that the rejection rate of the positively charged acid-resistant nanofiltration membrane to MgCl2 does not decrease significantly with time, indicating that the high-flux positively charged acid-resistant nanofiltration membrane has good acid resistance.

[0069] Measure the acid permeability and Mg 2+ ion rejection rate of the high-flux positively charged acid-resistant nanofiltration membrane to 3% HCl and 2 g / L MgCl2. As shown in Figure 2 FIG. 7, columnar chart A is the rejection rate of the high-flux positively charged acid-resistant nanofiltration membrane to Mg 2+ ions, with a rejection rate of 90%; columnar chart B is the acid permeability chart of the high-flux positively charged acid-resistant nanofiltration membrane, with an acid permeability of 99%.

[0070] Example 2

[0071] Take 1.25 g of polyethylene imine with a molecular weight of 600, 1800, 10000, and 25000, respectively, 1.0 g of sodium hydroxide, 0.15 g of sodium dodecyl benzene sulfonate, add deionized water to 500 ml, and fully disperse and stir for 12 hours; take 0.025 g of cyanuric chloride, dissolve it in 500 ml of n-hexane solvent, fully stir for 12 hours; first immerse the polysulfone ultrafiltration membrane soaked in deionized water in the aqueous solution for 10 min, take it out and dry, immerse it in the oil phase solution at 25°C for 3 min, and heat treat it at 70°C for 5 min, then wash it with deionized water, and measure its flux at room temperature, which is 80 LMH / MPa, measure its rejection rate to 2 / L MgCl2, which is 92%, and its surface Zeta potential is 26 mV.

[0072] Example 3

[0073] Take 1.25 g of polyethyleneimine with molecular weight of 600, 1800, 10000, 25000, 1.0 g of sodium hydroxide, 0.15 g of sodium dodecyl benzene sulfonate, add deionized water to 500 ml, and fully disperse and stir for 12 hours; take 0.025 g of trichloro cyanuric chloride, dissolve it in 500 ml of n-hexane solvent, fully stir for 12 hours; first immerse the polysulfone ultrafiltration membrane soaked in deionized water in the aqueous solution for 10 min, take it out and dry, immerse it in the oil phase solution at 25℃ for 3 min, heat treat it at 70℃ for 5 min, then clean it with 10 wt% citric acid for 5 min, and then clean it with deionized water again, measure its flux at room temperature, which is 150 LMH / MPa, measure its rejection rate to 2 / L MgCl2, which is 92%, and the Zeta potential on its surface is 18 mV.

[0074] Example 4

[0075] Take 1.25 g of polyethyleneimine with molecular weight of 600, 1800, 10000, 25000, 1.0 g of sodium hydroxide, 0.15 g of sodium dodecyl benzene sulfonate, add deionized water to 500 ml, and fully disperse and stir for 12 hours; take 0.025 g of trichloro cyanuric chloride, dissolve it in 500 ml of n-hexane solvent, fully stir for 12 hours; first immerse the polysulfone ultrafiltration membrane soaked in deionized water in the aqueous solution for 10 min, take it out and dry, immerse it in the oil phase solution at 25℃ for 3 min, heat treat it at 70℃ for 5 min, then clean it with 10 wt% citric acid for 5 min, and then clean it with deionized water again, measure its flux at room temperature, which is 150 LMH / MPa, measure its rejection rate to 2 / L MgCl2, which is 92%, and the Zeta potential on its surface is 18 mV.

[0076] Comparative Example 1

[0077] Soak the commercially available Dow NF270 nanofiltration membrane in 1 mol / L hydrochloric acid at 50℃, and measure the curve of the rejection rate of MgCl2 with time, as shown in curve b in Figure 1 The results show that the rejection rate of MgCl2 of the commercially available Dow NF270 nanofiltration membrane gradually decreases with time, indicating that the commercially available Dow NF270 has poor acid resistance.

[0078] Comparative Example 2

[0079] Test the flux of the commercially available AMS-A3012 acid-resistant nanofiltration membrane and compare it with the flux of the high-flux positively charged acid-resistant nanofiltration membrane in Example 3, as shown in Figure 3As shown in the middle columnar chart a (AMS-A3012), the membrane flux is only 22 LMH / MPa, while the flux of the columnar chart b (high-flux positively charged acid-resistant nanofiltration membrane) can reach 150 LMH / MPa. It is illustrated that the high-flux positively charged acid-resistant nanofiltration membrane has a great advantage in flux over the A3012 acid-resistant nanofiltration membrane of the AMS company.

[0080] Comparative Example 3

[0081] 1.25 g of polyethyleneimine with molecular weight of 600, 1800, 10000 and 25000, respectively, 1.0 g of sodium hydroxide, 0.15 g of sodium dodecyl benzene sulfonate, and deionized water were weighed, and the mixture was dispersed and stirred for 12 hours. 0.025 g of cyanuric chloride was dissolved in 500 ml of n-hexane solvent, and the mixture was stirred for 12 hours. The polysulfone ultrafiltration membrane immersed in deionized water was immersed in the water phase solution for 10 min, taken out and dried, and then immersed in the oil phase solution at 25°C for 3 min, and washed with deionized water. The flux was measured at room temperature, and was 363 LMH / MPa. The rejection rate to 2 / L MgCl2 was 18%. Compared with Example 2, the nanofiltration membrane after heat treatment greatly improved the salt rejection rate, but the flux decreased to a certain extent.

[0082] The above specific examples further illustrate the purpose, technical solutions and advantages of the present application. It should be understood that the above description is only for specific embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a high-flux positively charged acid-resistant nanofiltration membrane, characterized in that, The preparation method comprises the following steps: S1: immersing the ultrafiltration base film into a prepared aqueous solution for reaction, and drying to obtain an ultrafiltration base film one; S2: immersing the ultrafiltration base film one into an oil phase solution for reaction to obtain an ultrafiltration base film two; S3: heat treating the ultrafiltration base film two to obtain a high-flux positively charged acid-resistant nanofiltration membrane; The preparation method of the aqueous solution in the step S1 is as follows: sequentially adding an aqueous monomer, an acid-binding agent and a surfactant into deionized water, and uniformly dispersing them to obtain the aqueous solution; wherein the aqueous monomer comprises polyethyleneimine; The preparation method of the oil phase solution in the step S2 is as follows: dissolving cyanuric chloride into an organic solvent; the concentration of cyanuric chloride is 0.05 g / L; After the step S3, the obtained high-flux positively charged acid-resistant nanofiltration membrane is treated with citric acid, then washed with deionized water, and stored in the deionized water; The heat treatment temperature in the step S3 is 70 DEG C, and the heat treatment time is 5 min; The concentration of the citric acid is 10 wt%, and the treatment time is 5 min; The aqueous monomer is a mixture of polyethyleneimines with molecular weights of 600, 1800, 10000 and 25000.

2. The production method according to claim 1, wherein The organic solvent is n-hexane; The acid-binding agent is sodium hydroxide; The surfactant is sodium dodecyl sulfonate.

3. The application of the high-flux positively charged acid-resistant nanofiltration membrane prepared by the preparation method of any one of claims 1-2 in the field of water purification and industrial wastewater treatment.

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