Acid-resistant nanofiltration membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of membrane separation, in particular to an acid-resistant nanofiltration membrane as well as a preparation method and application thereof. The preparation method of the acid-resistant nanofiltration membrane comprises the following steps: coating a cleaned base membrane with an aqueous phase solution, and removing the redundant aqueous phase solution on the surface to obtain a first coating; and then coating the oil phase solution on the first coating to carry out interfacial polymerization reaction, removing the redundant oil phase solution on the surface after the reaction is completed, and then carrying out heat treatment. The aqueous phase 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 prepared by the preparation method has excellent acid resistance and salt interception performance.

Description

Technical Field

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

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

[0003] The acid-resistant nanofiltration membrane solves the problem of unstable hydrolysis of polyamide structure in conventional nanofiltration membranes under 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 acidic 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 the currently disclosed data, sulfonyl chloride monomers are mainly dissolved in traditional non-polar solvents such as isoparaffin or n-hexane, but their solubility is relatively weak, and it is difficult to ensure a high monomer concentration, thereby limiting the rate of interfacial polymerization. Although some commonly used ethylene glycol monomethyl ether, toluene and acetone, etc., are helpful to dissolve sulfonyl chloride monomers, some of them have poor mutual solubility with isoparaffin, and some have a certain swelling effect on the base film, which has certain difficulties in practical application. Based on the above background, in order to solve the problem that the solubility of sulfonyl chloride monomer is poor and the organic phase monomer concentration is too low to form a dense film layer, the present invention provides a method for preparing an acid-resistant nanofiltration membrane. Summary of the invention

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

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

[0007] The third purpose of the present invention is to provide an application of an acid-resistant nanofiltration membrane, which has broad application prospects.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: A method for preparing an acid-resistant nanofiltration membrane comprises the following steps: The aqueous solution is coated on the cleaned base film, and the excess aqueous solution on the surface is removed to obtain a first coating layer; the oily solution is then coated on the first coating layer to perform an interfacial polymerization reaction, and the excess oily solution on the surface is removed after the reaction is completed, and then a heat treatment is performed; The aqueous phase solution comprises polyamine monomers and water; the oil phase solution comprises sulfonyl chloride monomers and a mixed solvent; and the mixed solvent consists of a non-polar solvent and a polar aprotic ether solvent.

[0009] Furthermore, the cleaning specifically involves placing the base film in a pure water environment to remove surface impurities and oil stains, which can enhance the uniformity and density of the first coating.

[0010] The invention removes excess aqueous solution from the surface and keeps the membrane surface in a slightly wet environment, which is beneficial to the smooth progress of subsequent interfacial polymerization reaction and avoids the formation of defects.

[0011] Furthermore, the concentration of the polar aprotic ether solvent in the mixed solvent is 0.05-50wt%; the aprotic ether solvent is selected from one or more compounds containing two or more ether oxygen functional groups.

[0012] Furthermore, 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, and 1,3-dioxane.

[0013] The reasonable ratio of polar non-protonic ether solvents and non-polar solvents not only significantly improves the solubility of sulfonyl chloride monomers, but also effectively alleviates the swelling phenomenon of the base membrane, ensuring the uniformity and stability of the interfacial polymerization reaction. Specifically, in this mixed solvent system composed of polar non-protonic ether solvents and non-polar solvents, the introduction of polar non-protonic ethers is conducive to improving the solubility of acyl chloride monomers, making them evenly distributed in the oil phase solution, avoiding monomer aggregation, and thus ensuring the uniformity of the interfacial polymerization reaction; and the high proportion of non-polar solvents in the system can inhibit the swelling effect of the base membrane in a weakly polar environment. The reasonable ratio of the two solvents ensures that the sulfonyl chloride monomers are mainly concentrated at the interface to participate in the reaction and will not excessively penetrate into the base membrane, thereby improving the membrane density of the interfacial polymerization reaction and reducing the membrane thickness, ultimately achieving the purpose of improving the membrane's acid resistance and desalination performance.

[0014] Furthermore, the concentration of the sulfonyl chloride monomer in the oil phase solution is 0.05-5wt%; 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.

[0015] Furthermore, the sulfonyl chloride monomer is 1,3,6-naphthalenetrisulfonyl chloride or 1,3-benzenedisulfonyl chloride.

[0016] 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 0.05-5wt%, and the excess solution is promptly poured off after coating to promote the interfacial polymerization reaction. The generated polysulfonamide layer is dense, acid-resistant, and has good desalination performance and chemical stability.

[0017] Furthermore, the interfacial polymerization reaction time is 1-300s; the heat treatment temperature is 40-150°C, and the heat treatment time is 0.1-10min.

[0018] Furthermore, the heat treatment temperature is 90° C. and the heat treatment time is 6 minutes.

[0019] The interfacial polymerization reaction time of the present invention is 1-300 seconds to ensure that the sulfonyl chloride monomer in the organic phase solution can fully contact with the polyamine monomer on the surface of the base film and undergo interfacial polymerization reaction.

[0020] Furthermore, the interfacial polymerization reaction time is 20s.

[0021] Furthermore, the aqueous solution is coated on the base film for a time period of 1-300 seconds.

[0022] The aqueous solution of the present invention is coated on the base membrane for 1-300 seconds to ensure that the aqueous monomer is evenly distributed on the membrane surface and appropriately penetrates into the pores, providing reaction sites for interfacial polymerization.

[0023] Furthermore, the concentration of the polyamine monomer in the aqueous solution is 0.1-10wt%; 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.

[0024] The concentration of the polyamine monomer in the aqueous solution of the present invention is 0.1-10 wt %, which can ensure that the polyamine monomer forms a uniform and dense reaction layer on the surface of the base film.

[0025] Furthermore, the concentration of the polyamine monomer in the aqueous solution is 2-5 wt %.

[0026] The present invention further limits the concentration of the aqueous phase monomer in the aqueous phase solution to 2-5 wt %, which can enhance the mechanical strength of the membrane without affecting the water flux of the membrane.

[0027] Furthermore, the polyamine monomer is piperazine or polyethyleneimine.

[0028] Furthermore, 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 polyaryletherketone; and the non-polar solvent is selected from one of hexane, pentane, heptane, octane, nonane, decane, undecane, dodecane, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M.

[0029] The base membranes of the present invention have good mechanical strength and stability, and can provide necessary physical support for the nanofiltration membrane, thereby ensuring its stability and durability during operation.

[0030] An acid-resistant nanofiltration membrane is prepared by adopting the preparation method.

[0031] Application of the above acid-resistant nanofiltration membrane in industrial wastewater treatment.

[0032] The beneficial technical effects of the present invention are: The present invention provides a method for preparing an acid-resistant nanofiltration membrane, which involves a new oil phase solution, which includes a sulfonyl chloride monomer, a non-polar solvent, and a polar non-protonic ether solvent. The reasonable ratio of the polar non-protonic 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 basement membrane, ensuring the uniformity and stability of the interfacial polymerization reaction. Specifically, in this mixed solvent system composed of polar non-protonic ether solvents and non-polar solvents, the introduction of polar non-protonic ethers is beneficial to improving the solubility of sulfonyl chloride, making it evenly distributed in the oil phase solution, avoiding monomer aggregation, thereby ensuring the uniformity of the interfacial polymerization reaction; and a high proportion of non-polar solvents in the system can inhibit the swelling effect of the basement membrane in a weakly polar environment. The reasonable ratio of the two solvents ensures that the sulfonyl chloride is mainly concentrated at the interface to participate in the reaction, and will not excessively penetrate into the basement membrane, thereby improving the film layer density of the interfacial polymerization reaction, and reducing the membrane thickness, and finally achieving the purpose of improving the acid resistance and desalination performance of the membrane.

[0033] The nanofiltration membrane prepared by the present invention can maintain long-term stable performance in a strong acid environment of 20wt% sulfuric acid and exhibits excellent desalination performance, and is suitable for industrial wastewater treatment and waste acid recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a morphology diagram of the nanofiltration membrane obtained in Example 1; Figure 2 This is a morphology diagram of the nanofiltration membrane obtained in Comparative Example 2; Figure 3 This is a morphology diagram of the nanofiltration membrane obtained in Comparative Example 3; Figure 4is 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 1 are SEM images of the surface of the nanofiltration membrane obtained in Example 1 before and after acid treatment; wherein 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. DETAILED DESCRIPTION

[0035] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is 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 also be made, all of which should be deemed to belong to the protection scope of the present invention. The specific conditions not indicated in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are conventional products obtained through commercial channels.

[0036] Example 1 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polysulfone base membrane is placed in pure water to remove surface impurities and oil stains to obtain a clean base membrane; the aqueous solution is coated on the clean base membrane for 120 seconds, and the first coating layer is obtained after the excess aqueous solution on the surface is removed; then the oil solution is coated on the first coating layer for interfacial polymerization reaction for 20 seconds, and the excess oil solution on the surface is removed after the reaction is completed, and then heat-treated at 90°C for 6 minutes.

[0037] The aqueous phase solution is composed of 2wt% polyethyleneimine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; 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 dimethyl ether and 97 wt% of Isopar G.

[0038] This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0039] Example 2 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polysulfone base membrane is placed in pure water to remove surface impurities and oil stains to obtain a clean base membrane; the aqueous solution is coated on the clean base membrane for 120 seconds, and the first coating layer is obtained after the excess aqueous solution on the surface is removed; then the oil solution is coated on the first coating layer for interfacial polymerization reaction for 20 seconds, and the excess oil solution on the surface is removed after the reaction is completed, and then heat-treated at 90°C for 6 minutes.

[0040] The aqueous phase solution is composed of 2wt% polyethyleneimine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; The oil phase solution consists of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent consists of 1 wt% of ethylene glycol dimethyl ether and 99 wt% of Isopar G.

[0041] This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0042] Example 3 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polysulfone base membrane is placed in pure water to remove surface impurities and oil stains to obtain a clean base membrane; the aqueous solution is coated on the clean base membrane for 120 seconds, and the first coating layer is obtained after the excess aqueous solution on the surface is removed; then the oil solution is coated on the first coating layer for interfacial polymerization reaction for 20 seconds, and the excess oil solution on the surface is removed after the reaction is completed, and then heat-treated at 90°C for 6 minutes.

[0043] The aqueous phase solution is composed of 2wt% polyethyleneimine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; The oil phase solution consists of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent consists of 5 wt% of ethylene glycol dimethyl ether and 95 wt% of Isopar G.

[0044] This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0045] Example 4 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polysulfone base membrane is placed in pure water to remove surface impurities and oil stains to obtain a clean base membrane; the aqueous solution is coated on the clean base membrane for 120 seconds, and the first coating layer is obtained after the excess aqueous solution on the surface is removed; then the oil solution is coated on the first coating layer for interfacial polymerization reaction for 20 seconds, and the excess oil solution on the surface is removed after the reaction is completed, and then heat-treated at 90°C for 6 minutes.

[0046] The aqueous phase solution is composed of 2wt% polyethyleneimine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; The oil phase solution consists of 0.1 wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent consists of 10 wt% of ethylene glycol dimethyl ether and 90 wt% of Isopar G.

[0047] This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0048] Example 5 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polysulfone base membrane is placed in pure water to remove surface impurities and oil stains to obtain a clean base membrane; The aqueous solution is applied on the cleaned base film for 120 seconds, and the excess aqueous solution on the surface is removed to obtain the first coating; then the oil solution is applied on the first coating to perform interfacial polymerization reaction for 20 seconds, and the excess oil solution on the surface is removed after the reaction is completed, and then heat-treated at 90°C for 6 minutes.

[0049] The aqueous phase solution is composed of 2wt% polyethyleneimine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; 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 diethyl ether and 97 wt% of Isopar G.

[0050] This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0051] Example 6 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polyacrylonitrile base film is placed in pure water to remove surface impurities and oil stains to obtain a clean base film; the aqueous solution is coated on the clean base film for 30 seconds, and the first coating layer is obtained after the excess aqueous solution on the surface is removed; then the oil solution is coated on the first coating layer for interfacial polymerization reaction for 10 seconds, and the excess oil solution on the surface is removed after the reaction is completed, and then heat-treated at 40°C for 10 minutes.

[0052] The aqueous phase solution is composed of 2wt% polyethyleneimine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; The oil phase solution is composed of 0.5wt% of 1,3-benzenedisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 3wt% of dipropylene glycol dimethyl ether and 97wt% of Isopar G; This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0053] Example 7 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polyacrylonitrile base film is placed in pure water to remove surface impurities and oil stains to obtain a clean base film; the aqueous solution is coated on the clean base film for 30 seconds, and the first coating layer is obtained after the excess aqueous solution on the surface is removed; then the oil solution is coated on the first coating layer for interfacial polymerization reaction for 10 seconds, and the excess oil solution on the surface is removed after the reaction is completed, and then heat-treated at 40°C for 10 minutes.

[0054] The aqueous phase solution is composed of 2wt% piperazine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; 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; This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0055] Example 8 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polyacrylonitrile base film is placed in pure water to remove surface impurities and oil stains to obtain a clean base film; the aqueous solution is coated on the clean base film for 30 seconds, and the first coating layer is obtained after the excess aqueous solution on the surface is removed; then the oil solution is coated on the first coating layer for interfacial polymerization reaction for 10 seconds, and the excess oil solution on the surface is removed after the reaction is completed, and then heat-treated at 40°C for 10 minutes.

[0056] The aqueous phase solution is composed of 2wt% piperazine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; The oil phase solution is composed of 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, 5 wt% of 1,4-dioxane, and 90 wt% of Isopar G; This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0057] Example 9 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polyethersulfone base membrane is placed in pure water to remove surface impurities and oil stains to obtain a clean base membrane; the aqueous solution is coated on the clean base membrane for 30 seconds, and the first coating layer is obtained after removing excess aqueous solution on the surface; then the oil solution is coated on the first coating layer for interfacial polymerization reaction for 10 seconds, and after the reaction is completed, the excess oil solution on the surface is removed, and then heat-treated at 40°C for 10 minutes.

[0058] The aqueous phase solution is composed of 2wt% piperazine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; The oil phase solution is composed of 0.5wt% of 1,3-benzenedisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 3wt% of ethylene glycol dimethyl ether and 97wt% of Isopar L; This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0059] Example 10 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polyacrylonitrile base film is placed in pure water to remove surface impurities and oil stains to obtain a clean base film; the aqueous solution is coated on the clean base film for 30 seconds, and the first coating layer is obtained after the excess aqueous solution on the surface is removed; then the oil solution is coated on the first coating layer for interfacial polymerization reaction for 10 seconds, and the excess oil solution on the surface is removed after the reaction is completed, and then heat-treated at 40°C for 10 minutes.

[0060] The aqueous phase solution is composed of 2wt% polyethyleneimine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; The oil phase solution is composed of 0.5wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent is composed of 3wt% of ethylene glycol dimethyl ether and 97wt% of n-hexane; This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0061] Embodiment 11 This embodiment provides a method for preparing an acid-resistant nanofiltration membrane, and the specific preparation process is as follows: The polyethersulfone base membrane is placed in pure water to remove surface impurities and oil stains to obtain a clean base membrane; the aqueous solution is coated on the clean base membrane for 30 seconds, and the first coating layer is obtained after removing excess aqueous solution on the surface; then the oil solution is coated on the first coating layer for interfacial polymerization reaction for 10 seconds, and after the reaction is completed, the excess oil solution on the surface is removed, and then heat-treated at 40°C for 10 minutes.

[0062] The aqueous phase solution is composed of 2wt% piperazine, 2wt% triethylamine, 1wt% camphorsulfonic acid, 0.1wt% 4-dimethylaminopyridine and water; 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; This embodiment also provides an acid-resistant nanofiltration membrane, which is prepared using the above preparation method.

[0063] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the oil phase solution consists of 0.1 wt % of 1,3,6-naphthalenetrisulfonyl chloride and a solvent, the solvent is Isopar G, and the specific preparation conditions of the nanofiltration membrane are the same as those in Example 1.

[0064] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the oil phase solution consists of 0.1wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent consists of 3wt% of ethylene glycol monomethyl ether and 97wt% of Isopar G, and the specific preparation conditions of the nanofiltration membrane are the same as those in Example 1.

[0065] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the oil phase solution consists of 0.1wt% of 1,3,6-naphthalenetrisulfonyl chloride and a mixed solvent; the mixed solvent consists of 3wt% of acetone and 97wt% of Isopar G, and the specific preparation conditions of the nanofiltration membrane are the same as those in Example 1.

[0066] Test Example 1 Comparative Example 1 did not produce a complete nanofiltration membrane under the conditions described above, so this test example observed the morphology of the nanofiltration membranes obtained in Example 1 and Comparative Examples 2-3. The results are shown in Figure 1-3 .

[0067] Figure 1 is a morphology diagram of the nanofiltration membrane obtained in Example 1; Figure 2 This is a morphology diagram of the nanofiltration membrane obtained in Comparative Example 2; Figure 3 This is the morphology of the nanofiltration membrane obtained in Comparative Example 3. Figure 1-3It can be seen that the nanofiltration membrane obtained in Example 1 of the present invention has obvious stratification and good uniformity and density, while the membrane layer density of the nanofiltration membrane obtained in Comparative Example 2 is poor, and the bottom membrane of the nanofiltration membrane obtained in Comparative Example 3 collapses due to swelling.

[0068] Test Example 2 The nanofiltration membrane obtained in Example 1 was immersed in 20 wt % sulfuric acid for acid treatment for 100 days, and 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 Figure 4-5 , surface morphology see Figure 6 .

[0069] Figure 4 This is the infrared spectrum of the nanofiltration membrane obtained in Example 1 before acid treatment. Figure 5 It is the infrared spectrum of the nanofiltration membrane obtained in Example 1 after acid treatment. Figure 6 3 are SEM images of the surface of the nanofiltration membrane obtained in Example 1 before and after acid treatment, wherein 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.

[0070] Depend on Figure 4-6 It can be seen that after being treated with 20wt% sulfuric acid for 100 days, the surface morphology of the nanofiltration membrane obtained by the present invention was not changed. The above results show that the nanofiltration membrane obtained by the present invention has good stability in a strong acid environment.

[0071] Test Example 3 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 salt rejection rate and water flux of each nanofiltration membrane were tested. The results are shown in Table 1.

[0072] Table 1 It can be seen from Table 1 that compared with Comparative Examples 1-3, the nanofiltration membrane obtained in Examples 1-11 can maintain long-term stable performance in a strong acid environment of 20wt% sulfuric acid, showing excellent desalination performance, and is suitable for metal ion recovery and acidic wastewater treatment.

[0073] 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 above with specific implementation schemes. On the basis of the present invention, some modifications or replacements may be made thereto, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of protection claimed by the present invention.

Claims

1. A method for preparing an acid-resistant nanofiltration membrane, characterized in that: The following steps are involved: Applying the aqueous solution on the cleaned base film, and removing excess aqueous solution on the surface to obtain a first coating; Then the oil phase solution is coated on the first coating layer to carry out interfacial polymerization reaction, and after the reaction is completed, the excess oil phase solution on the surface is removed, and then heat treatment is carried out; The aqueous phase solution comprises polyamine monomers and water; the oil phase solution comprises sulfonyl chloride monomers and a mixed solvent; and the mixed solvent consists of a non-polar solvent and a polar aprotic ether solvent.

2. The method for preparing the acid-resistant nanofiltration membrane according to claim 1, characterized in that: The concentration of the polar aprotic ether solvent in the mixed solvent is 0.05-50wt%; the aprotic ether solvent is selected from one or more compounds containing two or more ether oxygen functional groups.

3. The method for preparing the acid-resistant nanofiltration membrane according to claim 2, characterized in that: 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, and 1,3-dioxane.

4. The method for preparing 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 0.05-5wt%; 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.

5. The method for preparing the acid-resistant nanofiltration membrane according to claim 1, characterized in that: The interfacial polymerization reaction time is 1-300s; the heat treatment temperature is 40-150°C, and the heat treatment time is 0.1-10min.

6. The method for preparing the acid-resistant nanofiltration membrane according to claim 1, characterized in that: The time for coating the aqueous solution on the base film is 1-300s.

7. The method for preparing the acid-resistant nanofiltration membrane according to claim 1, characterized in that: The concentration of the polyamine monomer in the aqueous phase solution is 0.1-10wt%, 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.

8. The method for preparing 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 polyaryletherketone; the non-polar solvent is selected from one of n-hexane, pentane, heptane, octane, nonane, decane, undecane, dodecane, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L and Isopar M.

9. An acid-resistant nanofiltration membrane, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. Use of the acid-resistant nanofiltration membrane according to claim 9 in industrial wastewater treatment and waste acid recovery.

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