An acid-resistant nanofiltration membrane, its preparation method and application

Abstract

The present invention relates to the field of membrane separation technology, and particularly relates to an acid-resistant nanofiltration membrane, a preparation method thereof and an application. The preparation method of the acid-resistant nanofiltration membrane comprises the following steps: coating an aqueous solution on a cleaned base membrane, and removing the excess aqueous solution on the surface to obtain a first coating; then coating an oil-phase solution on the first coating for interfacial polymerization reaction, removing the excess oil-phase solution on the surface after the reaction is completed, and then performing heat treatment; the aqueous solution comprises a polyamine monomer and water; the oil-phase solution comprises a sulfonyl chloride monomer and a mixed solvent; the mixed solvent is composed of a non-polar solvent and a polar aprotic ether solvent. The nanofiltration membrane obtained by the above preparation method has excellent acid resistance and salt rejection performance.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane separation, and particularly relates to an acid-resistant nanofiltration membrane, a preparation method thereof, and an application thereof. Background Art

[0002] Nanofiltration is a pressure-driven membrane separation process between ultrafiltration and reverse osmosis. The membrane pore size is in the nanometer range, and it has a good removal effect on multivalent ions and organic substances with a molecular weight of 200 - 1000. Nanofiltration membranes have been widely used in many fields such as water purification, wastewater treatment, and material separation.

[0003] The acid-resistant nanofiltration membrane solves the problem of the unstable hydrolysis of the polyamide structure of conventional nanofiltration membranes in a strong acidic environment and can be stable in a strong acidic environment of 20 wt% sulfuric acid. This membrane material shows great potential in the application of treating acid-containing waste liquid, especially in the separation and recovery of metal ions and acids. It can effectively recover valuable metal resources, reduce the discharge of acidic waste liquid, and help the steel, coal, printing and other industries achieve green development.

[0004] In currently disclosed materials, sulfonyl chloride monomers are mainly dissolved in traditional non-polar solvents such as isoparaffin or n-hexane, but their solubility is weak, making it difficult to ensure a high monomer concentration, thus limiting the rate of interfacial polymerization. And some commonly used ethylene glycol monomethyl ether, toluene, acetone, etc., although they are helpful for dissolving sulfonyl chloride monomers, some have poor miscibility with isoparaffin, and some have a certain swelling effect on the base membrane, presenting certain difficulties in practical applications. Based on the above background, to solve the problems of poor solubility of sulfonyl chloride monomers and too low concentration of organic phase monomers to form a dense membrane layer, the present invention provides a preparation method of an acid-resistant nanofiltration membrane. Summary of the Invention

[0005] The first object of the present invention is to provide a preparation method of an acid-resistant nanofiltration membrane, with simple steps and easy for large-scale production.

[0006] The second object of the present invention is to provide an acid-resistant nanofiltration membrane with excellent acid resistance and salt rejection rate.

[0007] The third object of the present invention is to provide an application of an acid-resistant nanofiltration membrane with broad application prospects.

[0008] To achieve the above objects, the technical solution adopted by the present invention is:

[0009] A preparation method of an acid-resistant nanofiltration membrane, comprising the following steps:

[0010] Coat an aqueous solution on a cleaned substrate film, and obtain a first coating after removing the excess aqueous solution on the surface; then coat an organic solution on the first coating for interfacial polymerization reaction. After the reaction is completed, remove the excess organic solution on the surface, and then perform heat treatment, that's all.

[0011] The aqueous solution includes polyamine monomers and water; the organic solution includes sulfonyl chloride monomers and a mixed solvent; the mixed solvent consists of a nonpolar solvent and a polar aprotic ether solvent.

[0012] Further, the "cleaned" specifically means placing the substrate film in a pure water environment to remove surface impurities and oil stains, which can enhance the uniformity and denseness of the first coating.

[0013] In the present invention, after removing the excess aqueous solution on the surface, a slightly wet environment is maintained on the film surface, which is beneficial to the smooth progress of the subsequent interfacial polymerization reaction and avoids the formation of defects.

[0014] Further, the concentration of the polar aprotic ether solvent in the mixed solvent is 0.05 - 50 wt%; the aprotic ether solvent is selected from one or more of the compounds containing two or more ether oxygen functional groups.

[0015] Further, the polar aprotic ether solvent is selected from one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, dipropylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,4 - dioxane, 1,3 - dioxane.

[0016] The reasonable ratio of the polar aprotic ether solvent and the nonpolar solvent not only significantly improves the solubility of the sulfonyl chloride monomer, but also effectively alleviates the swelling phenomenon of the substrate film, ensuring the uniformity and stability of the interfacial polymerization reaction. Specifically, in this mixed solvent system composed of the polar aprotic ether solvent and the nonpolar solvent, introducing the polar aprotic ether is beneficial to improving the solubility of the acyl chloride monomer, making it evenly distributed in the organic solution and avoiding monomer aggregation, thus ensuring the uniformity of the interfacial polymerization reaction; while the high - proportion nonpolar solvent in the system can inhibit the swelling effect of the substrate film in a weakly polar environment. The reasonable ratio of the two solvents ensures that the sulfonyl chloride monomer is mainly concentrated at the interface to participate in the reaction and will not penetrate excessively into the substrate film, thereby improving the film layer denseness of the interfacial polymerization reaction, reducing the film thickness, and ultimately achieving the purpose of improving the acid resistance and desalination performance of the film.

[0017] Further, the concentration of the sulfonyl chloride monomer in the organic solution is 0.05 - 5 wt%; the sulfonyl chloride monomer is selected from one or more of 1,3,6 - naphthalenetrisulfonyl chloride, 1,3 - benzenedisulfonyl chloride, 1,4 - benzenedisulfonyl chloride, 1,3,5 - benzenetrisulfonyl chloride, 2,6 - naphthalenedisulfonyl chloride, 1,6 - naphthalenedisulfonyl chloride.

[0018] Furthermore, the sulfonyl chloride monomer is 1,3,6-naphthalenetrisulfonyl chloride or 1,3-benzenedisulfonyl chloride.

[0019] The sulfonyl chloride monomer of the present invention and the polyamine monomer in the aqueous solution can form an acid-resistant polysulfonamide layer at the interface. The concentration of the sulfonyl chloride monomer is controlled at 0.05 - 5 wt%, and the excess solution is promptly poured off after coating to promote the interfacial polymerization reaction. The formed polysulfonamide layer is dense, highly acid-resistant, and has good desalination performance and chemical stability.

[0020] Furthermore, the time of the interfacial polymerization reaction is 1 - 300 s; the temperature of the heat treatment is 40 - 150 °C, and the time of the heat treatment is 0.1 - 10 min.

[0021] Furthermore, the temperature of the heat treatment is 90 °C, and the time of the heat treatment is 6 min.

[0022] The time of the interfacial polymerization reaction of the present invention is 1 - 300 s to ensure that the sulfonyl chloride monomer in the organic phase solution can fully contact the polyamine monomer on the surface of the base film and undergo an interfacial polymerization reaction.

[0023] Furthermore, the time of the interfacial polymerization reaction is 20 s.

[0024] Furthermore, the time for coating the aqueous solution on the base film is 1 - 300 s.

[0025] The time for coating the aqueous solution of the present invention on the base film is 1 - 300 s to ensure that the aqueous monomers are uniformly distributed on the film surface and moderately penetrate into the pores, providing reaction sites for the interfacial polymerization.

[0026] Furthermore, the concentration of the polyamine monomer in the aqueous solution is 0.1 - 10 wt%; the polyamine monomer is selected from one or more of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, diaminotoluene, ethylenediamine, propylenediamine, butylenediamine, diaminocyclohexane, piperazine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, and N-aminoethylpiperazine.

[0027] The concentration of the polyamine monomer in the aqueous solution of the present invention is 0.1 - 10 wt%, and this concentration can ensure that a uniform and dense reaction layer is formed on the surface of the base film by the polyamine monomer.

[0028] Furthermore, the concentration of the polyamine monomer in the aqueous solution is 2 - 5 wt%.

[0029] The present invention further defines that the concentration of the aqueous monomer in the aqueous solution is 2 - 5 wt%. This concentration can not only enhance the mechanical strength of the membrane but also not affect the water flux of the membrane.

[0030] Furthermore, the polyamine monomer is piperazine or polyethyleneimine.

[0031] Further, the base film is selected from one of polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polyimide, polyetherimide, polyacrylonitrile, polyphenylene ether, polyphenylene sulfide, polyether ketone, and polyarylether ketone; the non-polar solvent is selected from one or more of hexane, pentane, heptane, octane, nonane, decane, undecane, dodecane, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M.

[0032] The base films of the present invention all have good mechanical strength and stability, which can provide necessary physical support for the nanofiltration membrane and ensure its stability and durability during operation.

[0033] An acid-resistant nanofiltration membrane is prepared by the above preparation method.

[0034] The application of the above acid-resistant nanofiltration membrane in industrial wastewater treatment.

[0035] The beneficial technical effects of the present invention are as follows:

[0036] The present invention provides a preparation method of an acid-resistant nanofiltration membrane, which involves a new oil-phase solution. The oil-phase solution includes a sulfonyl chloride monomer, a non-polar solvent, and a polar aprotic ether solvent. The reasonable ratio of the polar aprotic ether solvent and the non-polar solvent not only significantly improves the solubility of the sulfonyl chloride monomer, but also effectively alleviates the swelling phenomenon of the base film, ensuring the uniformity and stability of the interfacial polymerization reaction. Specifically, in this mixed solvent system composed of a polar aprotic ether solvent and a non-polar solvent, introducing a polar aprotic ether solvent is beneficial to improving the solubility of sulfonyl chloride, making it evenly distributed in the oil-phase solution and avoiding monomer aggregation, thereby ensuring the uniformity of the interfacial polymerization reaction; while the high proportion of non-polar solvent in the system can inhibit the swelling effect of the base film in a weakly polar environment. The reasonable ratio of the two solvents ensures that sulfonyl chloride mainly concentrates at the interface to participate in the reaction and will not penetrate excessively into the base film, thereby improving the film layer density of the interfacial polymerization reaction and reducing the film thickness, and finally achieving the purpose of improving the acid resistance and desalination performance of the membrane.

[0037] The nanofiltration membrane prepared by the present invention can maintain long-term stable performance in a strong acid environment of 20 wt% sulfuric acid and exhibits excellent desalination performance, and is suitable for industrial wastewater treatment and waste acid recovery. Description of the Drawings

[0038] Figure 1 is the morphology diagram of the nanofiltration membrane obtained in Example 1;

[0039] Figure 2 is the morphology diagram of the nanofiltration membrane obtained in Comparative Example 2;

[0040] Figure 3 is the morphology diagram of the nanofiltration membrane obtained in Comparative Example 3;

[0041] Figure 4 is the infrared spectrum diagram of the nanofiltration membrane obtained in Example 1 before acid treatment;

[0042] Figure 5 is the infrared spectrum diagram of the nanofiltration membrane obtained in Example 1 after acid treatment;

[0043] Figure 6 are the SEM diagrams of the surface of the nanofiltration membrane obtained in Example 1 before and after acid treatment; among them, A is the SEM diagram of the surface of the nanofiltration membrane obtained in Example 1 before acid treatment, and B is the SEM diagram of the surface of the nanofiltration membrane obtained in Example 1 after acid treatment. Detailed implementation manners

[0044] The following content is a further detailed description of the present invention in combination with specific preferred implementation manners. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or replacements can still be made, and all should be regarded as belonging to the protection scope of the present invention. The specific conditions not specified in the examples are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are all conventional products obtained through commercial channels.

[0045] Example 1

[0046] This example provides a preparation method of an acid-resistant nanofiltration membrane, and the specific preparation process is as follows:

[0047] Place the polysulfone substrate membrane in pure water to remove surface impurities and oil stains to obtain a clean substrate membrane; coat the aqueous solution on the clean substrate membrane for 120 s, and remove the excess aqueous solution on the surface to obtain the first coating; then coat the oil phase solution on the first coating for interfacial polymerization reaction for 20 s. After the reaction is completed, remove the excess oil phase solution on the surface, and then perform heat treatment at 90 °C for 6 min, and that's it.

[0048] Among them, the aqueous solution is composed of 2 wt% of polyethyleneimine, 2 wt% of triethylamine, 1 wt% of camphorsulfonic acid, 0.1 wt% of 4-dimethylaminopyridine and water;

[0049] The oil phase solution is composed of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 3 wt% of ethylene glycol dimethyl ether and 97 wt% of Isopar G.

[0050] This embodiment also provides an acid-resistant nanofiltration membrane prepared by the above preparation method.

[0051] Example 2

[0052] This embodiment provides a preparation method of an acid-resistant nanofiltration membrane. The specific preparation process is as follows:

[0053] Place the polysulfone substrate membrane in pure water to remove surface impurities and oil stains, and obtain a clean substrate membrane; coat the aqueous solution on the clean substrate membrane for 120 s, and remove the excess aqueous solution on the surface to obtain the first coating; then coat the oil phase solution on the first coating and carry out an interfacial polymerization reaction for 20 s. After the reaction is completed, remove the excess oil phase solution on the surface, and then heat-treat at 90 °C for 6 min.

[0054] Among them, the aqueous solution is composed of 2 wt% of polyethyleneimine, 2 wt% of triethylamine, 1 wt% of camphorsulfonic acid, 0.1 wt% of 4-dimethylaminopyridine, and water;

[0055] The oil phase solution is composed of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 1 wt% of ethylene glycol dimethyl ether and 99 wt% of Isopar G.

[0056] This embodiment also provides an acid-resistant nanofiltration membrane prepared by the above preparation method.

[0057] Example 3

[0058] This embodiment provides a preparation method of an acid-resistant nanofiltration membrane. The specific preparation process is as follows:

[0059] Place the polysulfone substrate membrane in pure water to remove surface impurities and oil stains, and obtain a clean substrate membrane; coat the aqueous solution on the clean substrate membrane for 120 s, and remove the excess aqueous solution on the surface to obtain the first coating; then coat the oil phase solution on the first coating and carry out an interfacial polymerization reaction for 20 s. After the reaction is completed, remove the excess oil phase solution on the surface, and then heat-treat at 90 °C for 6 min.

[0060] Among them, the aqueous solution is composed of 2 wt% of polyethyleneimine, 2 wt% of triethylamine, 1 wt% of camphorsulfonic acid, 0.1 wt% of 4-dimethylaminopyridine, and water;

[0061] The oil phase solution is composed of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 5 wt% of ethylene glycol dimethyl ether and 95 wt% of Isopar G.

[0062] This embodiment also provides an acid-resistant nanofiltration membrane prepared by the above preparation method.

[0063] Example 4

[0064] This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows:

[0065] Place the polysulfone substrate membrane in pure water to remove surface impurities and oil stains, and obtain a clean substrate membrane; coat the aqueous solution on the clean substrate membrane for 120 s, and remove the excess aqueous solution on the surface to obtain the first coating; then coat the oil phase solution on the first coating for interfacial polymerization reaction for 20 s. After the reaction is completed, remove the excess oil phase solution on the surface, and then perform heat treatment at 90 °C for 6 min to obtain the membrane.

[0066] Among them, the aqueous solution is composed of 2 wt% of polyethyleneimine, 2 wt% of triethylamine, 1 wt% of camphorsulfonic acid, 0.1 wt% of 4-dimethylaminopyridine and water;

[0067] The oil phase solution is composed of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 10 wt% of ethylene glycol dimethyl ether and 90 wt% of Isopar G.

[0068] This embodiment also provides an acid-resistant nanofiltration membrane prepared by the above preparation method.

[0069] Example 5

[0070] This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows:

[0071] Place the polysulfone substrate membrane in pure water to remove surface impurities and oil stains, and obtain a clean substrate membrane;

[0072] Coat the aqueous solution on the clean substrate membrane for 120 s, and remove the excess aqueous solution on the surface to obtain the first coating; then coat the oil phase solution on the first coating for interfacial polymerization reaction for 20 s. After the reaction is completed, remove the excess oil phase solution on the surface, and then perform heat treatment at 90 °C for 6 min to obtain the membrane.

[0073] Among them, the aqueous solution is composed of 2 wt% of polyethyleneimine, 2 wt% of triethylamine, 1 wt% of camphorsulfonic acid, 0.1 wt% of 4-dimethylaminopyridine and water;

[0074] The oil phase solution is composed of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 3 wt% of ethylene glycol diethyl ether and 97 wt% of Isopar G.

[0075] This embodiment also provides an acid-resistant nanofiltration membrane prepared by the above preparation method.

[0076] Example 6

[0077] This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows:

[0078] Place the polyacrylonitrile-based membrane in pure water to remove surface impurities and oil stains, and obtain a cleaned base membrane; coat the aqueous solution on the cleaned base membrane for 30 s, remove the excess aqueous solution on the surface to obtain a first coating; then coat the oil phase solution on the first coating and carry out an interfacial polymerization reaction for 10 s. After the reaction is completed, remove the excess oil phase solution on the surface, and then heat-treat at 40 °C for 10 min, and that's it.

[0079] Among them, the aqueous solution is composed of 2 wt% of polyethyleneimine, 2 wt% of triethylamine, 1 wt% of camphorsulfonic acid, 0.1 wt% of 4-dimethylaminopyridine and water;

[0080] The oil phase solution is composed of 0.5 wt% of 1,3-benzenedisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 3 wt% of dipropylene glycol dimethyl ether and 97 wt% of Isopar G;

[0081] This embodiment also provides an acid-resistant nanofiltration membrane prepared by using the above preparation method.

[0082] Example 7

[0083] This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows:

[0084] Place the polyacrylonitrile-based membrane in pure water to remove surface impurities and oil stains, and obtain a cleaned base membrane; coat the aqueous solution on the cleaned base membrane for 30 s, remove the excess aqueous solution on the surface to obtain a first coating; then coat the oil phase solution on the first coating and carry out an interfacial polymerization reaction for 10 s. After the reaction is completed, remove the excess oil phase solution on the surface, and then heat-treat at 40 °C for 10 min, and that's it.

[0085] Among them, the aqueous solution is composed of 2 wt% of piperazine, 2 wt% of triethylamine, 1 wt% of camphorsulfonic acid, 0.1 wt% of 4-dimethylaminopyridine and water;

[0086] The oil phase solution is composed of 1 wt% of 1,3-benzenedisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 3 wt% of 1,4-dioxane and 97 wt% of Isopar G;

[0087] This embodiment also provides an acid-resistant nanofiltration membrane prepared by using the above preparation method.

[0088] Example 8

[0089] This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows:

[0090] Place the polyacrylonitrile-based membrane in pure water to remove surface impurities and oil stains, obtaining a clean base membrane; coat the water-phase solution on the clean base membrane for 30 s, and remove the excess water-phase solution on the surface to obtain the first coating; then coat the oil-phase solution on the first coating and carry out an interfacial polymerization reaction for 10 s. After the reaction is completed, remove the excess oil-phase solution on the surface, and then heat-treat it at 40 °C for 10 min, and that's it.

[0091] Among them, the water-phase solution is composed of 2 wt% piperazine, 2 wt% triethylamine, 1 wt% camphorsulfonic acid, 0.1 wt% 4-dimethylaminopyridine, and water;

[0092] The oil-phase solution is composed of 1 wt% 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 5 wt% ethylene glycol dimethyl ether, 5 wt% 1,4-dioxane, and 90 wt% Isopar G;

[0093] This example also provides an acid-resistant nanofiltration membrane prepared by the above preparation method.

[0094] Example 9

[0095] This example provides a preparation method for an acid-resistant nanofiltration membrane. The specific preparation process is as follows:

[0096] Place the polyethersulfone-based membrane in pure water to remove surface impurities and oil stains, obtaining a clean base membrane; coat the water-phase solution on the clean base membrane for 30 s, and remove the excess water-phase solution on the surface to obtain the first coating; then coat the oil-phase solution on the first coating and carry out an interfacial polymerization reaction for 10 s. After the reaction is completed, remove the excess oil-phase solution on the surface, and then heat-treat it at 40 °C for 10 min, and that's it.

[0097] Among them, the water-phase solution is composed of 2 wt% piperazine, 2 wt% triethylamine, 1 wt% camphorsulfonic acid, 0.1 wt% 4-dimethylaminopyridine, and water;

[0098] The oil-phase solution is composed of 0.5 wt% 1,3-benzenedisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 3 wt% ethylene glycol dimethyl ether and 97 wt% Isopar L;

[0099] This example also provides an acid-resistant nanofiltration membrane prepared by the above preparation method.

[0100] Example 10

[0101] This example provides a preparation method for an acid-resistant nanofiltration membrane. The specific preparation process is as follows:

[0102] Place the polyacrylonitrile-based membrane in pure water to remove surface impurities and oil stains, and obtain a clean base membrane; coat the aqueous solution on the clean base membrane for 30 s, and remove the excess aqueous solution on the surface to obtain the first coating; then coat the oil phase solution on the first coating and carry out an interfacial polymerization reaction for 10 s. After the reaction is completed, remove the excess oil phase solution on the surface, and then heat-treat at 40 °C for 10 min, and that's it.

[0103] Among them, the aqueous solution is composed of 2 wt% of polyethyleneimine, 2 wt% of triethylamine, 1 wt% of camphorsulfonic acid, 0.1 wt% of 4-dimethylaminopyridine, and water;

[0104] The oil phase solution is composed of 0.5 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 3 wt% of ethylene glycol dimethyl ether and 97 wt% of n-hexane;

[0105] This example also provides an acid-resistant nanofiltration membrane prepared by the above preparation method.

[0106] Example 11

[0107] This example provides a preparation method of an acid-resistant nanofiltration membrane, and the specific preparation process is as follows:

[0108] Place the polyethersulfone-based membrane in pure water to remove surface impurities and oil stains, and obtain a clean base membrane; coat the aqueous solution on the clean base membrane for 30 s, and remove the excess aqueous solution on the surface to obtain the first coating; then coat the oil phase solution on the first coating and carry out an interfacial polymerization reaction for 10 s. After the reaction is completed, remove the excess oil phase solution on the surface, and then heat-treat at 40 °C for 10 min, and that's it.

[0109] Among them, the aqueous solution is composed of 2 wt% of piperazine, 2 wt% of triethylamine, 1 wt% of camphorsulfonic acid, 0.1 wt% of 4-dimethylaminopyridine, and water;

[0110] The oil phase solution is composed of 1 wt% of 1,3-benzenedisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 3 wt% of ethylene glycol dimethyl ether and 97 wt% of Isopar M;

[0111] This example also provides an acid-resistant nanofiltration membrane prepared by the above preparation method.

[0112] Comparative Example 1

[0113] The difference between Comparative Example 1 and Example 1 is that: the oil phase solution is composed of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a solvent, and the solvent is Isopar G. The specific preparation conditions of the nanofiltration membrane are the same as those in Example 1.

[0114] Comparative Example 2

[0115] The difference between Comparative Example 2 and Example 1 is that: the oil-phase solution consists of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent consists of 3 wt% of ethylene glycol monomethyl ether and 97 wt% of Isopar G, and the specific preparation conditions of the nanofiltration membrane are the same as those in Example 1.

[0116] Comparative Example 3

[0117] The difference between Comparative Example 3 and Example 1 is that: the oil-phase solution consists of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent consists of 3 wt% of acetone and 97 wt% of Isopar G, and the specific preparation conditions of the nanofiltration membrane are the same as those in Example 1.

[0118] Test Example 1

[0119] A complete nanofiltration membrane was not made under the conditions of Comparative Example 1. Therefore, in this test example, the morphologies of the nanofiltration membranes obtained in Example 1 and Comparative Examples 2-3 were observed, and the results are shown in Figures 1-3 .

[0120] Figure 1 is the morphology diagram of the nanofiltration membrane obtained in Example 1; Figure 2 is the morphology diagram of the nanofiltration membrane obtained in Comparative Example 2; Figure 3 is the morphology diagram of the nanofiltration membrane obtained in Comparative Example 3. It can be observed from Figures 1-3 that the nanofiltration membrane obtained in Example 1 of the present invention has obvious stratification and good uniformity and denseness, while the membrane layer of the nanofiltration membrane obtained in Comparative Example 2 has poor denseness, and the bottom membrane of the nanofiltration membrane obtained in Comparative Example 3 shows a collapse phenomenon due to swelling.

[0121] Test Example 2

[0122] The nanofiltration membrane obtained in Example 1 was immersed in 20 wt% sulfuric acid for acid treatment for 100 days, and the infrared spectra of the membrane before and after acid treatment and the surface morphology of the membrane were collected. The infrared spectra are shown in Figures 4-5 , and the surface morphology is shown in Figure 6 .

[0123] Figure 4 is the infrared spectrum of the nanofiltration membrane obtained in Example 1 before acid treatment. Figure 5 is the infrared spectrum of the nanofiltration membrane obtained in Example 1 after acid treatment. Figure 6 are the SEM images of the surface of the nanofiltration membrane obtained in Example 1 before and after acid treatment, where A is the SEM image of the surface of the nanofiltration membrane obtained in Example 1 before acid treatment, and B is the SEM image of the surface of the nanofiltration membrane obtained in Example 1 after acid treatment.

[0124] From Figures 4-6It can be seen that after being treated with 20 wt% sulfuric acid for 100 days, the surface morphology of the nanofiltration membrane obtained in the present invention did not change. The above results indicate that the nanofiltration membrane obtained in the present invention has good stability in a strong acid environment.

[0125] Test Example 3

[0126] The nanofiltration membranes obtained in Examples 1-11 and Comparative Examples 1-3 were immersed in 20 wt% sulfuric acid for 100 days, and then the desalination rate and water flux of each nanofiltration membrane were detected. The results are shown in Table 1.

[0127] Table 1

[0128]

[0129]

[0130] It can be seen from observing Table 1 that compared with Comparative Examples 1-3, the nanofiltration membranes obtained in Examples 1-11 can maintain long-term stable performance in a strong acid environment of 20 wt% sulfuric acid, showing excellent desalination performance, and are suitable for metal ion recovery and acid wastewater treatment.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. The basic principles and main features of the present invention have been described with specific implementation schemes above. On the basis of the present invention, some modifications or replacements can be made, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the present invention claimed.

Claims

1. A preparation method of an acid-resistant nanofiltration membrane, characterized in that, It includes the following steps: Coat an aqueous solution on a cleaned base film, and obtain a first coating after removing the excess aqueous solution on the surface; Then coat an oil-phase solution on the first coating for interfacial polymerization reaction. After the reaction is completed, remove the excess oil-phase solution on the surface, and then perform heat treatment; The aqueous solution includes a polyamine monomer and water; the oil-phase solution includes a sulfonyl chloride monomer and a mixed solvent; the mixed solvent is composed of a non-polar solvent and a polar aprotic ether solvent; The non-polar solvent is selected from one or more of Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M; The concentration of the polar aprotic ether solvent in the mixed solvent is 1-10 wt%; The polar aprotic ether solvent is selected from one or more of dipropylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,4-dioxane, and 1,3-dioxane; 2. The preparation method of the acid-resistant nanofiltration membrane according to claim 1, characterized in that, The concentration of the sulfonyl chloride monomer in the oil-phase solution is 0.05-5 wt%; the sulfonyl chloride monomer is selected from one or more of 1,3,6-naphthalenetrisulfonyl chloride, 1,3-benzenedisulfonyl chloride, 1,4-benzenedisulfonyl chloride, 1,3,5-benzenetrisulfonyl chloride, 2,6-naphthalenedisulfonyl chloride, and 1,6-naphthalenedisulfonyl chloride; 3. The preparation method of the acid-resistant nanofiltration membrane according to claim 1, characterized in that, The time of the interfacial polymerization reaction is 1-300 s; the temperature of the heat treatment is 40-150 °C, and the time of the heat treatment is 0.1-10 min; 4. The preparation method of the acid-resistant nanofiltration membrane according to claim 1, characterized in that, The time for coating the aqueous solution on the base film is 1-300 s; 5. The preparation method of the acid-resistant nanofiltration membrane according to claim 1, wherein The concentration of the polyamine monomer in the aqueous solution is 0.1-10 wt%, and the polyamine monomer is selected from one or more of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, diaminotoluene, ethylenediamine, propylenediamine, butylenediamine, diaminocyclohexane, piperazine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, and N-aminoethylpiperazine; 6. The preparation method of the acid-resistant nanofiltration membrane according to claim 1, characterized in that, The base film is selected from one of polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polyimide, polyetherimide, polyacrylonitrile, polyphenylene ether, polyphenylene sulfide, polyether ketone, and polyarylether ketone; 7. A acid-resistant nanofiltration membrane, characterized in that, Prepared by the preparation method according to any one of claims 1-6; 8. Application of the acid-resistant nanofiltration membrane according to claim 7 in industrial wastewater treatment and waste acid recovery.

Images