Acid and alkali resistant composite filter membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of membrane separation and purification materials, in particular to an acid and alkali resistant composite filter membrane and a preparation method and application thereof. The composite filter membrane comprises a supporting bottom membrane and a separation membrane attached to the surface of the supporting bottom membrane, the separation membrane is at least obtained by performing interfacial polymerization reaction on a water-phase monomer containing a plurality of first groups and an oil-phase monomer containing a plurality of halogen atoms on the surface of the supporting bottom membrane, and the first groups are one or more of amido, hydroxyl and sulfydryl. Groups connected to halogen atoms in the oil-phase monomer are alkyl groups or alkyl groups. Halogen atoms connected to alkyl or alkyl can be subjected to substitution reaction with amido, hydroxyl or sulfydryl to form amido, ether bonds or thioether bonds, and a water-phase monomer and an oil-phase monomer are mutually connected to form a compact cross-linked structure, so that ion screening is realized. The amido, the ether bond and the thioether bond all have good acid and alkali resistance, so that the separation membrane is not easy to decompose in acid and alkali environments and has high acid and alkali resistance.

Description

Technical Field

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

[0002] In industrial production and daily life, the application scenarios of water treatment membrane separation technology are flexible and diverse, and the components of the separation objects are complex and varied, so the separation membranes are often challenged by many factors. For example, ion separation membranes used in wastewater treatment and recycling in industrial fields such as metallurgy, mining, printing and dyeing, and papermaking, strong acid or strong base separation media have put forward strict requirements on the acid-base stability of the chemical structure of the membrane material.

[0003] The membranes commonly used in water treatment are mainly traditional polyamide ion separation membranes, which are prepared based on the Schotten-Baumann type water-oil interfacial polymerization reaction between polyacyl chloride monomers and polyamine monomers. Although the amide bonds generated by this reaction construct a dense cross-linked network structure, they are prone to hydrolysis in strong acid and alkali media, causing serious bond breakage and severe loss of membrane separation performance. On the basis of maintaining excellent ion separation performance, the acid resistance of PA membranes can be enhanced by replacing the monomers in the oil phase solution with fluorinated peraromatic amine monomers, sulfonyl chloride monomers, cyanuric chloride monomers, etc., but alkali resistance is still difficult to achieve. Summary of the invention

[0004] The object of the present invention is to provide a composite filter membrane with excellent ion separation performance and acid and alkali resistance.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a composite filter membrane comprises:

[0007] Providing a supporting base film;

[0008] Allowing water-phase monomers and oil-phase monomers to undergo interfacial polymerization on the surface of the supporting base membrane to form a separation membrane, thereby obtaining the composite filter membrane;

[0009] The water phase monomer contains a plurality of first groups, and the first groups are one or more of amine, hydroxyl and thiol. The oil phase monomer contains a plurality of halogen atoms, and the groups connected to the halogen atoms in the oil phase monomer are all hydrocarbon groups or alkyl groups.

[0010] Optionally, the water phase monomer is provided by an aqueous solution containing the water phase monomer, and the oil phase monomer is provided by an oil solution containing the oil phase monomer.

[0011] After the supporting base film is fully infiltrated by the aqueous solution and excess liquid is removed, the supporting base film contacts with the oily solution, and the interfacial polymerization reaction occurs to form a film;

[0012] Alternatively, after the supporting base film is fully infiltrated by the oily solution and excess liquid is removed, the supporting base film is contacted with the aqueous solution, and the interfacial polymerization reaction occurs to form a film.

[0013] Optionally, the concentration of the aqueous phase monomer in the aqueous solution is any value between 1 g / L and 100 g / L;

[0014] and / or, the concentration of the oil phase monomer in the oily solution is any value between 1 g / L and 10 g / L;

[0015] And / or, the temperature of the interfacial polymerization reaction is any value between 10° C. and 50° C., and the time is any value between 1 hour and 48 hours.

[0016] Optionally, the number of the halogen atoms in the oil phase monomer is any value between 3 and 6.

[0017] Optionally, the aqueous phase monomer includes one or more of polyamines, polyhydroxy compounds and polythiols, and the oil phase monomer is polyalkyl halide and / or polyaryl halogenated aromatic hydrocarbon.

[0018] The polyamines include, but are not limited to, one or more of piperazine and its derivatives, triethylenediamine, 4-aminopiperidine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, o-phenylenediamine and m-phenylenediamine;

[0019] and / or the polyhydroxy compound includes, but is not limited to, one or more of cyclodextrin, catechol, hydroquinone, phloroglucinol, tannic acid, biphenol and resorcinol;

[0020] and / or the polythiol includes, but is not limited to, one or more of phenylenedithiol, isophenylenedithiol, biphenyl-4,4'-dithiol, 1,8-octanedithiol and 1,6-hexanedithiol;

[0021] and / or the polyalkanes include but are not limited to one or more of pentachloropentane, tetrabromoneopentane, and 1,3-diiodo-2,2-bis(iodomethyl)propane;

[0022] And / or the polyhalogenated aromatic hydrocarbon monomer includes one or more of 1,3,5-tri(chloromethyl)benzene, 1,3,5-tri(bromomethyl)benzene, 1,3,5-tri(iodomethyl)benzene, 1,3,5-tri(bromomethyl)-2,4,6-trimethylbenzene, hexa(bromomethyl)benzene, 4,4′-bis(bromomethyl)biphenyl, 1,3,5-trichlorobenzene, 1,3,5-tribromobenzene, 1,3,5-triiodobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,4,5-tetrabromobenzene, perfluorobenzene, hexachlorobenzene and hexabromobenzene.

[0023] In a second aspect, the present invention further provides an acid-base resistant composite filter membrane, comprising a separation membrane and a supporting base membrane, wherein the separation membrane is stacked and combined with the supporting base membrane, and the supporting base membrane is an ultrafiltration membrane.

[0024] Optionally, after being placed in an environment with a pH value of any one of 1 to 4 or 10 to 14 for 7 days, the retention rate of the composite filter membrane for monovalent and / or divalent inorganic salts decays to any one of 0 to 10%.

[0025] Optionally, the separation membrane is formed by interfacial polymerization of water-phase monomers and oil-phase monomers on the surface of the supporting base membrane.

[0026] Optionally, the separation membrane is a polyamine compound, and / or the separation membrane is a polyether compound, and / or the separation membrane is a polysulfide compound.

[0027] Optionally, the chemical structure of the separation membrane includes a first segment, a second segment and a connecting bond, the two ends of the connecting bond are respectively connected to the first segment and the second segment, any one of the first segments is connected to multiple connecting bonds, and the groups on the first segment connected to the connecting bonds are all alkyl groups or hydrocarbon groups, and any one of the second segments is connected to multiple connecting bonds, and the connecting bonds are one or more of amine groups, ether bonds and thioether bonds.

[0028] Optionally, the first segment is a segment formed by removing halogen atoms from an oil phase monomer, the oil phase monomer is a polyalkyl halide and / or a polyaryl halogenated aromatic hydrocarbon, and the groups connected to the halogen atoms in the oil phase monomer are all hydrocarbon groups or alkyl groups, the second segment is a segment formed by removing the first group from an aqueous phase monomer, the aqueous phase monomer includes one or more of polyamines, polyhydroxy compounds and polythiols, and the first group is one or more of amine groups, hydroxyl groups and thiol groups.

[0029] Optionally, the polyamine includes, but is not limited to, one or more of piperazine and its derivatives, triethylenediamine, 4-aminopiperidine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, o-phenylenediamine and m-phenylenediamine;

[0030] and / or the polyhydroxy compound includes, but is not limited to, one or more of cyclodextrin, catechol, hydroquinone, phloroglucinol, tannic acid, biphenol and resorcinol;

[0031] and / or the polythiol includes, but is not limited to, one or more of phenylenedithiol, isophenylenedithiol, biphenyl-4,4'-dithiol, 1,8-octanedithiol and 1,6-hexanedithiol;

[0032] and / or the polyalkanes include but are not limited to one or more of pentachloropentane, tetrabromoneopentane, and 1,3-diiodo-2,2-bis(iodomethyl)propane;

[0033] And / or the polyhalogenated aromatic hydrocarbon monomer includes one or more of 1,3,5-tri(chloromethyl)benzene, 1,3,5-tri(bromomethyl)benzene, 1,3,5-tri(iodomethyl)benzene, 1,3,5-tri(bromomethyl)-2,4,6-trimethylbenzene, hexa(bromomethyl)benzene, 4,4′-bis(bromomethyl)biphenyl, 1,3,5-trichlorobenzene, 1,3,5-tribromobenzene, 1,3,5-triiodobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,4,5-tetrabromobenzene, perfluorobenzene, hexachlorobenzene and hexabromobenzene.

[0034] Optionally, the thickness of the separation membrane is any value between 10 nm and 1000 nm, and the molecular weight cutoff of the composite filter membrane is any value between 100 Da and 2000 Da.

[0035] Optionally, the retention rate of the composite filter membrane for boric acid is any value between 0% and 10%, and / or the basic water flux of the composite filter membrane is 1 L·m -2 ·h -1 bar -1 ~100L·m -2 ·h -1 bar -1 and / or the retention rate of the composite filter membrane for monovalent inorganic salts is any value in the range of 5% to 99% and / or the retention rate of divalent inorganic salts is any value in the range of 20% to 99%.

[0036] Optionally, the supporting base membrane is an acid- and alkali-resistant ultrafiltration membrane, and the supporting base membrane is any one of a polyethersulfone ultrafiltration membrane, a polysulfone ultrafiltration membrane, a polyvinylidene fluoride ultrafiltration membrane, and a polyacrylonitrile ultrafiltration membrane.

[0037] In a third aspect, the present invention also provides the use of the above-mentioned composite filter membrane in any field of seawater desalination, drinking water purification, high-salt wastewater treatment, alkaline wastewater treatment, acid wastewater treatment, and metal ion / boric acid separation.

[0038] In a fourth aspect, the present invention further provides a method for selective separation and extraction of metal ions-boric acid, comprising:

[0039] The solution containing metal ions and boric acid is selectively filtered through the composite filter membrane, so that the metal salt and boric acid therein are respectively enriched on both sides of the composite filter membrane.

[0040] The beneficial effect of the present invention is that the halogen atom connected to the hydrocarbon group or alkyl group can undergo substitution reaction with the amine group, hydroxyl group or thiol group to form an amine group, an ether bond or a thioether bond. The aqueous phase monomer containing multiple first groups and the oil phase monomer containing multiple halogen atoms undergo interfacial polycondensation through the above reaction to obtain a dense cross-linked structure, so that the water flux of the membrane is large and the ion retention rate is high, thereby realizing ion screening. Since the amine group, ether bond and thioether bond all have good acid and alkali resistance, the separation membrane is not easy to decompose in an acid and alkali environment and has high acid and alkali resistance.

[0041] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of the method for preparing the composite filter membrane shown in Example 1 of the present invention;

[0043] Figure 2 The schematic diagram of the interfacial polymerization reaction principle and molecular structure of the separation membrane shown in the first embodiment of the present invention;

[0044] Figure 3a This is a scanning electron microscope photograph of the surface of the composite filter membrane shown in Example 1 of the present invention;

[0045] Figure 3b is a transmission electron microscope photograph of a cross section of the composite filter membrane shown in Example 1 of the present invention;

[0046] Figure 4 The test graphs are of the basic water flux, the separation flux when separating 1000 ppm monovalent and divalent inorganic salt aqueous solutions, and the salt retention rate of the composite filter membrane shown in Example 1 of the present invention;

[0047] Figure 5 The test graphs are of the basic water flux of the composite filter membrane shown in Example 1 of the present invention after being soaked in a concentrated strong alkali aqueous solution, the separation flux when separating 1000 ppm monovalent and divalent inorganic salt aqueous solutions, and the salt retention rate;

[0048] Figure 6 The test graphs are of the basic water flux of the composite filter membrane shown in Example 1 of the present invention after being soaked in a concentrated strong acid aqueous solution, the separation flux when separating 1000 ppm monovalent and divalent inorganic salt aqueous solutions, and the salt retention rate;

[0049] Figure 7 This is a test diagram of the separation flux and rejection rate of the composite filter membrane shown in Example 1 of the present invention for a 1000 ppm sodium hydroxide or lithium hydroxide aqueous solution;

[0050] Figure 8 This is a test graph of the separation flux and retention rate of the composite filter membrane shown in Example 1 of the present invention for a mixed aqueous solution of lithium chloride and boric acid with a total concentration of 1000 ppm and different lithium / boron mass ratios. DETAILED DESCRIPTION

[0051] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0053] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0055] See also Figure 1 In an embodiment of the present invention, a method for preparing a composite filter membrane is provided, comprising:

[0056] S100, providing a supporting base film.

[0057] S200, forming a separation membrane by interfacial polymerization of water-phase monomers and oil-phase monomers on the surface of the supporting base membrane to obtain a composite filter membrane.

[0058] The aqueous phase monomer contains multiple first groups, and the first groups are one or more of amine, hydroxyl and thiol. The oil phase monomer contains multiple halogen atoms, and the groups connected to the halogen atoms in the oil phase monomer are all hydrocarbon groups or alkyl groups.

[0059] The halogen atoms connected to the hydrocarbon group or alkyl group can undergo substitution reaction with the amine group, hydroxyl group or thiol group to form an amine group, an ether bond or a thioether bond. The aqueous phase monomer containing multiple first groups and the oil phase monomer containing multiple halogen atoms undergo interfacial polycondensation through the above reaction to obtain a dense cross-linked structure, thereby making the membrane have a large water flux and a high ion retention rate, thereby achieving ion screening. Since the amine group, ether bond and thioether bond all have good acid and alkali resistance, the separation membrane is not easy to decompose in an acid and alkali environment and has high acid and alkali resistance.

[0060] In some embodiments, the water phase monomer is provided by an aqueous solution containing the water phase monomer, and the oil phase monomer is provided by an oil solution containing the oil phase monomer.

[0061] After the supporting base film is fully infiltrated by the aqueous solution and the excess liquid is removed, it comes into contact with the oily solution, an interfacial polymerization reaction occurs, and a film is formed;

[0062] Or after the supporting base film is fully infiltrated by the oily solution and the excess liquid is removed, it comes into contact with the aqueous solution, an interfacial polymerization reaction occurs, and a film is formed.

[0063] In some embodiments, the concentration of the aqueous phase monomer in the aqueous solution is any value between 1 g / L and 100 g / L, for example, any value between 1 g / L, 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L and 100 g / L;

[0064] and / or, the concentration of the oil phase monomer in the oily solution is any value in the range of 1 g / L to 10 g / L, for example, any value in the range of 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L and 10 g / L;

[0065] And / or, the temperature of the interfacial polymerization reaction is any value between 10°C and 50°C, for example, it can be any value between 10°C, 20°C, 30°C, 40°C and 50°C, and the time is any value between 1h and 48h, for example, it can be any value between 1h, 3h, 6h, 9h, 13h, 25h, 37h and 48h.

[0066] Adjusting the concentration of the aqueous phase monomer in the aqueous solution, the concentration of the oil phase monomer in the oil solution, and the temperature and time of the reaction contributes to adjusting the separation performance of the resulting separation membrane.

[0067] In some embodiments, the number of halogen atoms in the oil phase monomer is any value between 3 and 6, for example, it can be any value between 3, 4, 5 and 6, so that the water phase monomer and the oil phase monomer are cross-linked into a network structure of a preset density, thereby controlling the separation performance of the membrane.

[0068] In some embodiments, the aqueous phase monomer includes one or more of a polyamine, a polyhydroxy compound, and a polythiol, and the oil phase monomer is a polyalkyl halide and / or a polyaryl halogenated aromatic hydrocarbon.

[0069] Polyamines include, but are not limited to, one or more of piperazine and its derivatives, triethylenediamine, 4-aminopiperidine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, o-phenylenediamine, and m-phenylenediamine;

[0070] and / or polyhydroxy compounds including, but not limited to, one or more of cyclodextrin, catechol, hydroquinone, phloroglucinol, tannic acid, biphenol, and resorcinol;

[0071] and / or polythiols including, but not limited to, one or more of phenylenedithiol, isophenylenedithiol, biphenyl-4,4'-dithiol, 1,8-octanedithiol, and 1,6-hexanedithiol;

[0072] and / or polyalkyl halide including but not limited to one or more of tetrachloropentaene, tetrabromoneopentane, 1,3-diiodo-2,2-bis(iodomethyl)propane;

[0073] and / or the polyhalogenated aromatic hydrocarbon monomers include one or more of 1,3,5-tri(chloromethyl)benzene, 1,3,5-tri(bromomethyl)benzene, 1,3,5-tri(iodomethyl)benzene, 1,3,5-tri(bromomethyl)-2,4,6-trimethylbenzene, hexa(bromomethyl)benzene, 4,4′-bis(bromomethyl)biphenyl, 1,3,5-trichlorobenzene, 1,3,5-tribromobenzene, 1,3,5-triiodobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,4,5-tetrabromobenzene, perfluorobenzene, hexachlorobenzene and hexabromobenzene.

[0074] An embodiment of the present invention further provides an acid-base resistant composite filter membrane, comprising a separation membrane and a supporting base membrane, wherein the separation membrane and the supporting base membrane are stacked and combined, and the supporting base membrane is an ultrafiltration membrane.

[0075] In some embodiments, after being placed in an environment with a pH value of 1 to 4 or 10 to 14 for 7 days, the retention rate of the composite filter membrane for monovalent and / or divalent inorganic salts decays to any value of 0 to 10%. The environmental pH value can be, for example, any value of 1, 2, 3, 4, 10, 11, 12, 13 and 14. At this time, the environment is highly acidic or alkaline, and the composite filter membrane has been fully in contact with the acidic or alkaline substances in the environment. At this time, the retention rate of the composite filter membrane for monovalent salts and / or divalent inorganic salts decays to any value of 0 to 10%, that is, the retention rate after being placed in a strong acidic environment or a strong alkaline environment is lower than the retention rate before placement by any value of 0 to 10%, for example, it can be any value of 0, 2%, 4%, 6%, 8% and 10%. At this time, it can be determined that the composite filter membrane has high acid and alkali resistance.

[0076] In some embodiments, the separation membrane is formed by interfacial polymerization of water-phase monomers and oil-phase monomers on the surface of the supporting base membrane.

[0077] In some embodiments, the separation membrane is a polyamine compound, and / or the separation membrane is a polyether compound, and / or the separation membrane is a polysulfide ether compound, and the monomers of the separation membrane are connected by amino groups, ether bonds or thioether bonds. At this time, the connecting bonds do not contain groups such as carbon groups that are easily oxidized and decomposed, which helps to improve the separation membrane's tolerance to acids and alkalis.

[0078] In some embodiments, the chemical structure of the separation membrane includes a first segment, a second segment and a connecting bond, the two ends of the connecting bond are respectively connected to the first segment and the second segment, any first segment is connected to multiple connecting bonds, and the groups connected to the connecting bonds on the first segment are all alkyl groups or hydrocarbon groups, and any second segment is connected to multiple connecting bonds, and the connecting bonds are one or more of amine groups, ether bonds and thioether bonds.

[0079] The first segment and the second segment are connected by one or more of an amine group, an ether bond and a thioether bond to achieve cross-linking. Since the first segment and the second segment are not connected by conventional amide or ester bonds in the molecular structure of the separation membrane, that is, the connecting bonds do not contain unsaturated bonds that are easily decomposed, the connecting bonds of the separation membrane are not easy to break when in an acidic or alkaline environment, thereby preventing the separation membrane from being corroded and decomposed by acid and alkali, thereby making the separation membrane suitable for acidic and alkaline environments.

[0080] In some embodiments, the first segment is a segment formed by removing the halogen atom from the oil phase monomer, the oil phase monomer is a polyalkyl halide and / or a polyaryl halogenated aromatic hydrocarbon, and the groups connected to the halogen atom in the oil phase monomer are all hydrocarbon groups or alkyl groups. The second segment is a segment formed by removing the first group from the water phase monomer, the water phase monomer includes one or more of a polyamine, a polyhydroxy compound and a polythiol, and the first group is one or more of an amino group, a hydroxyl group and a thiol group.

[0081] In some embodiments, the polyamine includes, but is not limited to, one or more of piperazine and its derivatives, triethylenediamine, 4-aminopiperidine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, o-phenylenediamine, and m-phenylenediamine;

[0082] and / or polyhydroxy compounds including, but not limited to, one or more of cyclodextrin, catechol, hydroquinone, phloroglucinol, tannic acid, biphenol, and resorcinol;

[0083] and / or polythiols including, but not limited to, one or more of phenylenedithiol, isophenylenedithiol, biphenyl-4,4'-dithiol, 1,8-octanedithiol, and 1,6-hexanedithiol;

[0084] and / or polyalkyl halide including but not limited to one or more of tetrachloropentaene, tetrabromoneopentane, 1,3-diiodo-2,2-bis(iodomethyl)propane;

[0085] and / or the polyhalogenated aromatic hydrocarbon monomers include one or more of 1,3,5-tri(chloromethyl)benzene, 1,3,5-tri(bromomethyl)benzene, 1,3,5-tri(iodomethyl)benzene, 1,3,5-tri(bromomethyl)-2,4,6-trimethylbenzene, hexa(bromomethyl)benzene, 4,4′-bis(bromomethyl)biphenyl, 1,3,5-trichlorobenzene, 1,3,5-tribromobenzene, 1,3,5-triiodobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,4,5-tetrabromobenzene, perfluorobenzene, hexachlorobenzene and hexabromobenzene.

[0086] In some embodiments, the thickness of the separation membrane is any value in the range of 10 nm to 1000 nm, for example, any value in the range of 10 nm, 50 nm, 100 nm, 300 nm, 500 nm, 700 nm and 1000 nm, and the molecular weight cutoff of the composite filter membrane is any value in the range of 100 Da to 2000 Da, for example, any value in the range of 10 Da, 50 Da, 100 Da, 300 Da, 500 Da, 700 Da, 1000 Da, 1500 Da and 2000 Da. By controlling the thickness of the membrane, it is helpful to obtain a specific molecular weight cutoff of the membrane.

[0087] In some embodiments, the rejection rate of the composite filter membrane for boric acid is any value between 0 and 10%, for example, any value between 0, 2%, 4%, 6%, 8% and 10%;

[0088] The basic water flux of the composite membrane is 1 L·m -2 ·h -1 bar -1 ~100L·m -2 ·h -1 bar -1 Any value in, for example, 1 L·m-2 ·h -1 bar -1 、3L·m -2 ·h -1 bar -1 、15L·m -2 ·h -1 bar -1 、27L·m -2 ·h -1 bar -1 、50L·m -2 ·h -1 bar -1 、65L·m -2 ·h -1 bar -1 and 100 L·m -2 ·h -1 bar -1 Any value in ;

[0089] and / or the rejection rate of the composite filter membrane for monovalent inorganic salts is any value in the range of 5% to 99%, for example, any value in the range of 5%, 10%, 20%, 30%, 40%, 50%, 70% and 99%;

[0090] And / or the retention rate of the divalent inorganic salt is any value between 20% and 99%, for example, it can be any value between 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 99%.

[0091] By controlling the composite filter membrane's retention rate for boric acid, basic water flux and retention rate for monovalent and / or divalent inorganic salts, it helps to improve the separation membrane's ability to selectively separate and extract metal ions-boric acid, making the separation membrane suitable for selective separation applications of certain salt lake brines, such as lithium / boron separation, and helping to improve the practicality of the separation membrane.

[0092] In some embodiments, the supporting base membrane is an acid- and alkali-resistant ultrafiltration membrane, and the supporting base membrane is any one of a polyethersulfone ultrafiltration membrane, a polysulfone ultrafiltration membrane, a polyvinylidene fluoride ultrafiltration membrane, and a polyacrylonitrile ultrafiltration membrane.

[0093] The embodiments of the present invention also provide the use of the composite filter membrane in any of the fields of seawater desalination, drinking water purification, high-salt wastewater treatment, alkaline wastewater treatment, acid wastewater treatment, and metal ion / boric acid separation. The composite filter membrane is used to separate different ions, thereby being applied in a variety of fields.

[0094] The embodiment of the present invention also provides a method for selective separation and extraction of metal ions-boric acid, comprising:

[0095] The solution containing metal ions and boric acid is selectively filtered through the composite filter membrane, so that the metal salt and boric acid therein are respectively enriched on both sides of the composite filter membrane.

[0096] A solution containing metal ions and boric acid is filtered through a composite filter membrane. After the filtration is completed, the composite filter membrane intercepts the metal ions and allows the boric acid to pass through, thereby achieving selective separation of metal ions and boric acid, so that the composite filter membrane can be effectively used in fields such as lithium extraction and boron removal from salt lakes.

[0097] In some embodiments, the metal salt includes a monovalent metal ion, such as a lithium metal ion.

[0098] The technical solution of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention and do not limit the scope of the present invention. Unless otherwise specified, the raw materials, reagents, reaction devices and testing equipment used in the following examples are conventional and can be commercially obtained; and unless otherwise specified, some of the processes involved are carried out at room temperature, such as a common temperature of 15°C to 35°C and normal pressure.

[0099] Embodiment 1:

[0100] See also Figure 3b The acid-base resistant composite filter membrane shown in a preferred embodiment of the present application includes a supporting base membrane and a separation membrane formed on the surface of the supporting base membrane. Figure 1 and Figure 2 , the preparation method of the composite filter membrane comprises:

[0101] S100, providing a supporting base film.

[0102] S200, forming a separation membrane by interfacial polymerization of water-phase monomers and oil-phase monomers on the surface of the supporting base membrane to obtain a composite filter membrane.

[0103] In step S100, a polyethersulfone ultrafiltration membrane is selected as a supporting bottom membrane and is fully soaked and rinsed with deionized water before use.

[0104] Step S200 includes:

[0105] S210, allowing the aqueous solution containing the aqueous monomer to fully infiltrate the supporting base film, and removing excess liquid;

[0106] S220, bringing the supporting base film soaked with the aqueous solution into contact with the oily solution containing the oily phase monomer to cause an interfacial polymerization reaction and form a film.

[0107] In other embodiments, the oily solution may be used for infiltration first, and then contacted with the aqueous solution.

[0108] In step S210, after removing the residual water on both sides of the polyethersulfone ultrafiltration membrane, the membrane is fully infiltrated with an aqueous solution containing 68.9 g / L of piperazine for 120 seconds, and then the residual aqueous solution on both sides of the polyethersulfone ultrafiltration membrane is wiped off until there are no obvious water drops.

[0109] Step S220 includes:

[0110] S221. Control the film-making environment temperature at 25°C and the humidity at 60%.

[0111] S222. Immerse the wiped ultrafiltration membrane in a n-hexane solution containing 2.1 g / L 1,3,5-tri(bromomethyl)benzene, maintain the ambient temperature at 25°C, and allow the interfacial polymerization reaction to proceed for 24 hours.

[0112] S223. After the interfacial polymerization reaction is completed, the mixture is rinsed with n-hexane to remove unreacted 1,3,5-tri(bromomethyl)benzene, and then post-treated at 60°C and dried for 30 minutes to obtain a polyamine composite filter membrane with a polyethersulfone ultrafiltration membrane as a supporting base membrane.

[0113] Take part of the prepared composite filter membrane and observe its surface and cross-sectional structure using scanning electron microscopy and transmission electron microscopy respectively. Figure 3a and Figure 3b , it can be seen that the composite filter membrane forms a continuous double-layer membrane structure.

[0114] Take part of the prepared composite filter membrane and test its basic water flux and separation flux and salt retention rate for separating 1000ppm of various monovalent and divalent inorganic salt aqueous solutions. The salt retention rate is calculated by testing the conductivity of the filtrate and feed solution. See the test results for details. Figure 4 It can be seen that the composite filter membrane has a large flux and exhibits excellent retention performance for a variety of ions.

[0115] Take part of the prepared composite filter membrane and place it in a 2 mol / L sodium hydroxide aqueous solution. After soaking it at room temperature for 7 days, rinse it thoroughly with deionized water. -1 , the basic water flux of the membrane was tested under cross-flow separation conditions at a temperature of 25°C, and the separation flux and salt retention rate of 1000ppm inorganic salt aqueous solution. Please refer to the test results Figure 5 It can be seen that after long-term immersion in strong alkali, the composite filter membrane still maintains a relatively good separation flux and ion retention rate, and has excellent strong alkali resistance.

[0116] Take part of the prepared composite filter membrane and place it in a 20w / v% sulfuric acid aqueous solution. After soaking it at room temperature for 7 days, rinse it with deionized water. Then soak it in a 2mol / L sodium hydroxide aqueous solution at room temperature for 1 day. After rinsing the membrane with deionized water, place it in a 2mol / L sodium hydroxide aqueous solution at room temperature. -1 , the basic water flux of the membrane was tested under cross-flow separation conditions at a temperature of 25°C, and the separation flux and salt retention rate of 1000ppm inorganic salt aqueous solution. Please refer to the test results Figure 6 It can be seen that after treatment with strong acid aqueous solution, the composite filter membrane still maintains a relatively good separation flux and ion retention rate, which can prove that the composite filter membrane has excellent strong acid resistance.

[0117] Take two prepared composite filter membranes and filter them at a pressure of 6 bar and a flow rate of 50 L·h -1 The separation flux and retention rate of 1000ppm sodium hydroxide or lithium hydroxide aqueous solution were tested under the cross-flow separation conditions of 25℃. The retention rate was calculated by the sodium content in the filtrate and feed solution tested by inductively coupled plasma emission spectrometry. Figure 7 It can be seen that the composite filter membrane can directly filter the inorganic strong alkali solution and has a better retention effect.

[0118] Take three prepared composite filter membranes and filter them at a pressure of 6 bar and a flow rate of 50 L·h -1 The separation flux and retention rate of the mixed aqueous solution of lithium chloride and boric acid with a total concentration of 1000ppm and a lithium / boron mass ratio of 3 / 1, 1 / 1 or 1 / 3 were tested under the cross-flow separation conditions of 25℃. The retention rates of lithium chloride and boric acid were calculated by the lithium and boron contents in the filtrate and feed solution tested by inductively coupled plasma emission spectrometry. Please refer to the test results for Figure 8 It can be seen that when the lithium / boron mass ratio in the mixed aqueous solution of lithium chloride and boric acid is between 1 / 3 and 3 / 1, the composite filter membrane maintains a better retention rate for lithium chloride and has a higher permeability to boric acid, and can achieve selective separation of lithium and boron.

[0119] Embodiment 2:

[0120] The difference between this embodiment and the first embodiment is that:

[0121] In step S100, a polyvinylidene fluoride ultrafiltration membrane is selected as a supporting bottom membrane;

[0122] In step S210, the membrane is fully infiltrated with an aqueous solution containing 100 g / L piperazine for 10 seconds;

[0123] In step S221, the film-making environment temperature is controlled at 10° C. and the humidity is controlled at 30%;

[0124] In step S222, the substrate is immersed in a n-hexane solution containing 1 g / L of 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene, the ambient temperature is maintained at 10°C, and the interfacial polymerization reaction is carried out for 48 hours.

[0125] Embodiment three:

[0126] The difference between this embodiment and the first embodiment is that:

[0127] In step S100, a polyacrylonitrile ultrafiltration membrane is selected as a supporting bottom membrane;

[0128] In step S210, the membrane is fully infiltrated with an aqueous solution containing 1 g / L piperazine for 600 seconds;

[0129] In step S221, the film-making environment temperature is controlled at 50° C. and the humidity is controlled at 80%;

[0130] In step S222, the substrate is immersed in a n-hexane solution containing 10 g / L of 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene, and the ambient temperature is maintained at 50°C for interfacial polymerization reaction for 1 hour.

[0131] Embodiment 4:

[0132] The difference between this embodiment and the first embodiment is that the water-based monomer is triethylenediamine and the oil-based monomer is pentaene tetrachloride.

[0133] Embodiment five:

[0134] The only difference between this embodiment and the first embodiment is that the water-based monomer is ethylenediamine and the oil-based monomer is 1,3-diiodo-2,2-bis(iodomethyl)propane.

[0135] Embodiment six:

[0136] The only difference between this embodiment and the first embodiment is that the water-based monomer is o-phenylenediamine and the oil-based monomer is 1,2,4,5-tetrachlorobenzene.

[0137] The composite filter membranes obtained in Examples 2 to 6 were subjected to the same tests as in Example 1, which proved that each composite filter membrane formed a continuous double-layer membrane structure, had a large flux and exhibited excellent retention performance for a variety of ions, had excellent resistance to strong acids and alkalis, could directly filter inorganic strong alkali solutions with excellent retention effects, and could achieve selective separation of lithium and boron.

[0138] Embodiment seven:

[0139] The difference between this embodiment and the first embodiment is that:

[0140] Step S100 uses a polyethylene ultrafiltration membrane as a supporting bottom membrane;

[0141] In step S210, the membrane is fully infiltrated with an aqueous solution containing 100 g / L resorcinol and 40 g / L sodium hydroxide for 10 seconds;

[0142] In step S221, the film-making environment temperature is controlled at 40° C. and the humidity is controlled at 30%;

[0143] In step S222, the film is immersed in a n-hexane solution containing 1 g / L of 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene, and the film-forming environment temperature is maintained at 40°C for interfacial polymerization reaction for 48 hours.

[0144] The basic water flux of the composite filter membrane in this embodiment is 2.1m -2 ·h -1 bar -1 The interception rate of the composite membrane for 1000ppm of divalent salt sodium sulfate is 94.5%. The composite membrane has excellent acid and alkali resistance. After being soaked in 2mol / L sodium hydroxide aqueous solution or 20w / v% sulfuric acid aqueous solution for 7 days, the interception rate of 1000ppm of sodium sulfate is 94.2%.

[0145] Embodiment eight:

[0146] The difference between this embodiment and the first embodiment is that:

[0147] Step S100 uses a polyvinylidene fluoride ultrafiltration membrane as a supporting bottom membrane;

[0148] In step S210, the membrane is fully infiltrated with an aqueous solution containing 80 g / L resorcinol and 40 g / L potassium hydroxide for 20 seconds;

[0149] In step S221, the film-making environment temperature is controlled at 60° C. and the humidity is controlled at 30%;

[0150] In step S222, the film is immersed in a n-hexane solution containing 1 g / L of 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene, and the film-forming environment temperature is maintained at 60°C for interfacial polymerization reaction for 48 hours.

[0151] The basic water flux of the composite filter membrane in this embodiment is 2.1m -2 ·h -1 bar -1 The interception rate of the composite membrane for 1000ppm of divalent sodium sulfate is 94.2%. The composite membrane has excellent acid and alkali resistance. After being soaked in 2mol / L sodium hydroxide aqueous solution or 20w / v% sulfuric acid aqueous solution for 7 days, the interception rate of 1000ppm of sodium sulfate is 93.8%.

[0152] The beneficial effects of the present invention are as follows: a novel separation membrane and a composite filter membrane including the separation membrane are obtained, wherein in the chemical formula of the separation membrane, a first segment formed by an oil phase monomer and a second segment formed by an aqueous phase monomer are connected by an amine group, a thioether bond or an ether bond as a connecting bond, and since the connecting bond does not contain an unsaturated bond, the connecting bond is not easy to break even in a harsh acid-base environment, thereby making the separation membrane and the composite filter membrane including the separation membrane have strong acid-base resistance, and can still maintain excellent ion separation performance after being soaked in a 2 mol / L sodium hydroxide aqueous solution or a 20 w / v% sulfuric acid aqueous solution for 7 days under appropriate conditions.

[0153] In addition, the basic water flux of the separation membrane mentioned in some embodiments of the present invention is greater than 2L·m -2 ·h -1 bar -1 , and the retention rate for 1000ppm of various divalent salts is relatively high, between 94% and 99%, and the retention rate for 1000ppm of various monovalent salts is relatively high, between 96% and 98%.

[0154] In addition, the separation membrane of the present invention can directly separate inorganic strong alkali solution under specific conditions, and the interception rate of 1000 ppm of sodium hydroxide or lithium hydroxide is not less than 85%.

[0155] The separation membrane of the present invention can also achieve efficient selective separation of lithium and boron, which cannot be achieved by conventional polyamide nanofiltration membranes and reverse osmosis membranes. Under appropriate conditions, the retention rate of lithium chloride and boric acid mixed solutions with a total concentration of 1000 ppm and different lithium / boron mass ratios can be higher than 94%, while the retention rate of boric acid can be lower than 8%.

[0156] The novel polyamine acid- and alkali-resistant composite filter membrane provided by the present invention has a simple preparation method and is easy to scale up industrially, and has high application value in life and industrial fields such as seawater desalination, drinking water purification, high-salt wastewater treatment, alkaline wastewater treatment, acid wastewater treatment, and lithium extraction and boron removal from salt lakes.

[0157] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0158] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a composite filter membrane, characterized in that: include: Providing a supporting base film; Allowing water-phase monomers and oil-phase monomers to undergo interfacial polymerization on the surface of the supporting base membrane to form a separation membrane, thereby obtaining the composite filter membrane; The water phase monomer contains a plurality of first groups, and the first groups are one or more of amine, hydroxyl and thiol. The oil phase monomer contains a plurality of halogen atoms, and the groups connected to the halogen atoms in the oil phase monomer are all hydrocarbon groups or alkyl groups.

2. The preparation method according to claim 1, characterized in that: The water phase monomer is provided by an aqueous solution containing the water phase monomer, and the oil phase monomer is provided by an oil solution containing the oil phase monomer. After the supporting base film is fully infiltrated by the aqueous solution and excess liquid is removed, the supporting base film contacts with the oily solution, and the interfacial polymerization reaction occurs to form a film; Alternatively, after the supporting base film is fully infiltrated by the oily solution and excess liquid is removed, the supporting base film is contacted with the aqueous solution, and the interfacial polymerization reaction occurs to form a film.

3. The preparation method according to claim 2, characterized in that: The concentration of the aqueous phase monomer in the aqueous solution is any value between 1 g / L and 100 g / L; and / or, the concentration of the oil phase monomer in the oily solution is any value between 1 g / L and 10 g / L; And / or, the temperature of the interfacial polymerization reaction is any value between 10° C. and 50° C., and the time is any value between 1 hour and 48 hours.

4. The preparation method according to claim 1, characterized in that: The number of the halogen atoms in the oil phase monomer is any value between 3 and 6.

5. The preparation method according to claim 4, characterized in that: The aqueous phase monomers include one or more of polyamines, polyhydroxy compounds and polythiols, and the oil phase monomers are polyalkyl halides and / or polyaryl halogenated aromatic hydrocarbons. The polyamines include, but are not limited to, one or more of piperazine and its derivatives, triethylenediamine, 4-aminopiperidine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, o-phenylenediamine and m-phenylenediamine; and / or the polyhydroxy compound includes, but is not limited to, one or more of cyclodextrin, catechol, hydroquinone, phloroglucinol, tannic acid, biphenol and resorcinol; and / or the polythiol includes, but is not limited to, one or more of phenylenedithiol, isophenylenedithiol, biphenyl-4,4'-dithiol, 1,8-octanedithiol and 1,6-hexanedithiol; and / or the polyalkanes include but are not limited to one or more of pentachloropentane, tetrabromoneopentane, and 1,3-diiodo-2,2-bis(iodomethyl)propane; And / or the polyhalogenated aromatic hydrocarbon monomer includes one or more of 1,3,5-tri(chloromethyl)benzene, 1,3,5-tri(bromomethyl)benzene, 1,3,5-tri(iodomethyl)benzene, 1,3,5-tri(bromomethyl)-2,4,6-trimethylbenzene, hexa(bromomethyl)benzene, 4,4′-bis(bromomethyl)biphenyl, 1,3,5-trichlorobenzene, 1,3,5-tribromobenzene, 1,3,5-triiodobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,4,5-tetrabromobenzene, perfluorobenzene, hexachlorobenzene and hexabromobenzene.

6. An acid-base resistant composite filter membrane, characterized in that: The invention comprises a separation membrane and a supporting bottom membrane, wherein the separation membrane and the supporting bottom membrane are stacked and combined, and the supporting bottom membrane is an ultrafiltration membrane.

7. The composite filter membrane according to claim 6, characterized in that: After being placed in an environment with a pH value of 1 to 4 or 10 to 14 for 7 days, the retention rate of the composite filter membrane for monovalent and / or divalent inorganic salts decays to any value of 0 to 10%.

8. The composite filter membrane according to claim 7, characterized in that: The separation membrane is formed by allowing water phase monomers and oil phase monomers to react on the surface of the supporting base membrane via an interfacial polymerization reaction.

9. The composite filter membrane according to claim 6, characterized in that: The separation membrane is a polyamine compound, and / or the separation membrane is a polyether compound, and / or the separation membrane is a polysulfide compound.

10. The composite filter membrane according to claim 9, characterized in that: The chemical structure of the separation membrane includes a first segment, a second segment and a connecting bond, wherein the two ends of the connecting bond are respectively connected to the first segment and the second segment, any one of the first segments is connected to a plurality of the connecting bonds, and the groups on the first segment connected to the connecting bonds are all alkyl groups or hydrocarbon groups, and any one of the second segments is connected to a plurality of the connecting bonds, and the connecting bonds are one or more of amine groups, ether bonds and thioether bonds.

11. The composite filter membrane according to claim 10, characterized in that: The first segment is a segment formed by removing the halogen atom from the oil phase monomer, the oil phase monomer is a polyalkyl halide and / or a polyaryl halogenated aromatic hydrocarbon, and the groups connected to the halogen atom in the oil phase monomer are all hydrocarbon groups or alkyl groups. The second segment is a segment formed by removing the first group from the water phase monomer, the water phase monomer includes one or more of polyamines, polyhydroxy compounds and polythiols, and the first group is one or more of amino groups, hydroxyl groups and thiol groups.

12. The composite filter membrane according to claim 11, characterized in that The polyamines include, but are not limited to, one or more of piperazine and its derivatives, triethylenediamine, 4-aminopiperidine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, o-phenylenediamine and m-phenylenediamine; and / or the polyhydroxy compound includes, but is not limited to, one or more of cyclodextrin, catechol, hydroquinone, phloroglucinol, tannic acid, biphenol and resorcinol; and / or the polythiol includes, but is not limited to, one or more of phenylenedithiol, isophenylenedithiol, biphenyl-4,4'-dithiol, 1,8-octanedithiol and 1,6-hexanedithiol; and / or the polyalkanes include but are not limited to one or more of pentachloropentane, tetrabromoneopentane, and 1,3-diiodo-2,2-bis(iodomethyl)propane; And / or the polyhalogenated aromatic hydrocarbon monomer includes one or more of 1,3,5-tri(chloromethyl)benzene, 1,3,5-tri(bromomethyl)benzene, 1,3,5-tri(iodomethyl)benzene, 1,3,5-tri(bromomethyl)-2,4,6-trimethylbenzene, hexa(bromomethyl)benzene, 4,4′-bis(bromomethyl)biphenyl, 1,3,5-trichlorobenzene, 1,3,5-tribromobenzene, 1,3,5-triiodobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,4,5-tetrabromobenzene, perfluorobenzene, hexachlorobenzene and hexabromobenzene.

13. The composite filter membrane according to any one of claims 6 to 12, characterized in that: The thickness of the separation membrane is any value between 10nm and 1000nm, and the molecular weight of the composite filter membrane is any value between 100Da and 2000Da.

14. The composite filter membrane according to any one of claims 6 to 12, characterized in that: The composite filter membrane has a retention rate of boric acid of any value between 0% and 10%, and / or a basic water flux of the composite filter membrane of 1 L·m- 2 ·h -1 bar -1 ~100L·m -2 ·h -1 bar -1 and / or the retention rate of the composite filter membrane for monovalent inorganic salts is any value in the range of 5% to 99% and / or the retention rate of divalent inorganic salts is any value in the range of 20% to 99%.

15. The composite filter membrane according to claim 6, characterized in that: The supporting base membrane is an acid- and alkali-resistant ultrafiltration membrane, and the supporting base membrane is any one of a polyethersulfone ultrafiltration membrane, a polysulfone ultrafiltration membrane, a polyvinylidene fluoride ultrafiltration membrane, and a polyacrylonitrile ultrafiltration membrane.

16. Use of the composite filter membrane according to any one of claims 6 to 15 in any field of seawater desalination, drinking water purification, high-salt wastewater treatment, alkaline wastewater treatment, acid wastewater treatment, and metal ion / boric acid separation.

17. A method for selective separation and extraction of metal ions-boric acid, characterized in that: include: A solution containing metal ions and boric acid is subjected to selective permeation filtration through the composite filter membrane according to any one of claims 6 to 15, so that the metal salt and boric acid therein are respectively enriched on both sides of the composite filter membrane.

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