CN113509839B - Acid/alkali-resistant composite nanofiltration membrane and preparation method and application thereof - Google Patents

Acid/alkali-resistant composite nanofiltration membrane and preparation method and application thereof Download PDF

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CN113509839B
CN113509839B CN202010271899.6A CN202010271899A CN113509839B CN 113509839 B CN113509839 B CN 113509839B CN 202010271899 A CN202010271899 A CN 202010271899A CN 113509839 B CN113509839 B CN 113509839B
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nanofiltration membrane
composite nanofiltration
preparation
polyamine
layer
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CN113509839A (en
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张杨
刘轶群
潘国元
于浩
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Sinopec Beijing Research Institute of Chemical Industry
China Petroleum and Chemical Corp
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Sinopec Beijing Research Institute of Chemical Industry
China Petroleum and Chemical Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/10—Supported membranes; Membrane supports
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/10—Supported membranes; Membrane supports
    • B01D69/105—Support pretreatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/28—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/30—Chemical resistance
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/02—Synthetic macromolecular fibres
    • B32B2262/0253—Polyolefin fibres
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Abstract

The invention relates to an acid/alkali resistant composite nanofiltration membrane, and a preparation method and application thereof. The composite nanofiltration membrane comprises a bottom layer, a middle porous supporting layer and a surface separation layer, wherein the separation layer is a polyurea separation layer. The polyurea separating layer is obtained by interfacial polymerization of polyamine and polyisocyanate. A large number of intermolecular hydrogen bonds (carbonyl and imino or amino in carbamido) can be formed in the molecular structure of the polyurea, and the molecular structure of the separation layer is more compact due to the existence of the hydrogen bonds, so that the stability of the separation layer in an acid/alkali medium is more improved. The composite nanofiltration membrane can stably run in an aqueous solution with the pH value of 0-14, has high desalination rate and water permeability and strong acid/alkali resistance, and the preparation method is simple and has great industrial application prospect.

Description

Acid/alkali-resistant composite nanofiltration membrane and preparation method and application thereof
Technical Field
The invention relates to the field of functional films, in particular to an acid/alkali resistant composite nanofiltration membrane and a preparation method and application thereof.
Background
Nanofiltration is a pressure-driven membrane separation process between reverse osmosis and ultrafiltration, the pore size range of the nanofiltration membrane is about several nanometers, the removal of monovalent ions and organic matters with the molecular weight less than 200 is poor, and the removal rate of divalent or multivalent ions and organic matters with the molecular weight between 200 and 500 is high. Can be widely used in the fields of fresh water softening, seawater softening, drinking water purification, water quality improvement, oil-water separation, wastewater treatment and recycling, and the classification, purification, concentration and the like of chemical products such as dye, antibiotic, polypeptide, polysaccharide and the like.
At present, most commercial nanofiltration membranes use polysulfone ultrafiltration membranes as a supporting layer, interfacial polymerization of polyamine aqueous phase and polyacyl chloride organic phase is carried out in situ on the upper surface of the ultrafiltration membrane, and the final product is a composite nanofiltration membrane. The common aqueous phase monomer is piperazine or piperazine substituted amine, the organic phase is trimesoyl chloride or a multifunctional acyl halide, as disclosed in patent numbers US4769148 and US4859384, a large amount of unreacted acyl chloride groups are hydrolyzed into carboxylic acid, so that the surface of the nanofiltration membrane is negatively charged, and by utilizing the charge effect, the polypiperazine amide composite nanofiltration membrane has higher retention rate on high-valence anions and adjustable retention rate on monovalent anions. In addition, patent nos. US4765897, US4812270 and US4824574 also provide a method how to convert polyamide composite reverse osmosis membranes into nanofiltration membranes. However, due to the limitation of the material characteristics, the traditional polyamide nanofiltration membrane is degraded in an extreme pH environment, particularly under a strong alkaline condition, and the polyamide nanofiltration membrane is generally used in a pH range of 2 to 11, so that the polyamide nanofiltration membrane can be only used for a neutral medium or a weakly acidic medium close to neutral.
In recent years, researchers have developed various nanofiltration membranes, and various commercial products have appeared. In addition, many new materials, such as sulfonated polyether ketone, sulfonated polyether sulfone, and the like, are also applied to the field of nanofiltration.
The document "Acid stable thin-film composite membrane prepared from a polystyrene-1,3,6-trisulfonylchloride (NTSC) and piperazine (PIP)", J.Membr.Sci.,415-416,122-131,2012 ": the sulfonamide material has strong acid resistance, and a composite nanofiltration membrane obtained by interfacial polymerization of a polynary sulfonyl chloride monomer and piperazine can keep stable separation performance in an environment with pH = 0.
Reported in the literature "Sulfonated poly (etherketone) based composite membranes for nanofilamentation of acidic and alkaline media, J.Membr.Sci.,381,81-89,2011": the sulfonated polyether-ether-ketone has acid resistance and strong alkali resistance, a nanofiltration membrane material with excellent interception performance can be obtained through Crosslinking, and the crosslinked polyether-ether-ketone material has strong solvent resistance and can separate dyes (Crosslinking of modified poly (ether ketone) membranes for use in solvent nanofilation, 447,212-221, 2013) in polar solvents such as isopropanol, acetone and the like.
The application of an acid-alkali-resistant and high-temperature-resistant nanofiltration membrane HYDRACoRe70pHT in the recovery of waste alkali liquor in sugar industry, membrane science and technology, 32,11-15,2006 reports: the commercial sulfonated polyether sulfone composite nanofiltration membrane is a HYDRACoRe series developed by Nindon electrician-Heidenen, can be used in strong acid and strong alkali solutions, and is widely applied to the recovery of waste alkali.
The acid-resistant nanofiltration membrane Duracid NF1812C developed by GE company is a three-layer composite structure, and the material of the separation layer is polysulfonamide (patent number US 7138058), which can be kept stable under the conditions of 20% hydrochloric acid, sulfuric acid and phosphoric acid, and can be kept stable under the conditions of 70 ℃ and 20% sulfuric acid.
The nanofiltration membranes capable of stable long-term operation at pH =0 to 14 were reported in patent nos. US5265734, EP0392982 (A3) to be exclusively SelRO MPS34 developed by KOCH, which was first developed by israel scientists and was first applied to pervaporation.
AMS company develops an acid-resistant, alkali-resistant and solvent-resistant composite nanofiltration membrane, and a separation layer is made of polyamine (US 9943811) and is prepared by interfacial polymerization reaction of polyamine and cyanuric chloride or a derivative thereof.
The literature (Journal of Membrane Science 523 (2017) 487-496) and the literature (Journal of Membrane Science 478 (2015) 75-84) report that a polyaniline separation layer is modified on a porous support layer by using an interfacial polymerization method, and the composite nanofiltration Membrane has strong permeation and separation stability in a medium environment with the pH = 0-14.
The literature (Journal of Membrane Science 572 (2019) 489-495) utilizes a phase inversion and post-treatment method to prepare a polyvinylidene fluoride nanofiltration Membrane material which has strong stability in strong acid and strong alkali environments.
Disclosure of Invention
The invention aims to overcome the defects of poor acid resistance and poor alkali resistance of the existing nanofiltration membrane, and provides an acid/alkali resistant composite nanofiltration membrane, a preparation method thereof, and application of the composite nanofiltration membrane and the composite nanofiltration membrane prepared by the method in the field of water treatment.
The composite nanofiltration membrane comprises a bottom layer, a middle porous supporting layer and a surface separation layer, wherein the separation layer is a polyurea separation layer.
The composite nanofiltration membrane comprises a three-layer structure: the bottom layer of the substrate is provided with a porous support layer on one surface, and a dense polyurea separation layer with a cross-linked structure on the other surface.
According to the present invention, the base layer and the porous support layer are not particularly limited, and may be made of various existing materials having a certain strength and capable of being used for a nanofiltration membrane. The bottom layer can be non-woven fabrics, and the material of non-woven fabrics is in polyethylene and polypropylene one or two mixture. The material of the porous support layer is one or a mixture of several of polyethersulfone, polysulfone, polyaromatic ether, polybenzimidazole, polyetherketone, polyetheretherketone, polyacrylonitrile, polyvinylidene fluoride and polyaryletherketone, which can be known to those skilled in the art and will not be described herein again.
The polyurea separating layer is obtained by interfacial polymerization of polyamine and polyisocyanate.
The polyamine comprises at least one of aliphatic polyamine and aromatic amine. The aliphatic polyamine is preferably at least one of piperazine, ethylenediamine, 1,2-propanediamine, 1,4-butanediamine, diethylenetriamine, tetraethylenepentamine, polyethyleneimine, polyethylene polyamine and polyether amine; the aromatic amine is preferably at least one selected from m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene and melamine.
The polyisocyanate is preferably at least one selected from m-xylylene diisocyanate, o-xylylene diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, toluene-2,6-diisocyanate, 1,4-phenylene diisocyanate, toluene-2,4-diisocyanate, 4,4 '-methylene bis (phenyl isocyanate), 1,3-phenylene diisocyanate, 3,3' -dichloro-4,4 '-diisocyanate biphenyl, dicyclohexylmethane-4,4' -diisocyanate, trimethylhexamethylene diisocyanate, L-lysine-ethyl ester-diisocyanate, 1,4-cyclohexyl diisocyanate, 4-chloro-6-methyl m-phenylene diisocyanate; more preferably at least one selected from the group consisting of m-xylylene diisocyanate, o-xylylene diisocyanate, 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate, 4,4 '-methylenebis (phenylisocyanate), 3,3' -dichloro-4,4 '-diisocyanate biphenyl, dicyclohexylmethane-4,4' -diisocyanate, and 1,4-cyclohexyl diisocyanate.
The polyamine preferably includes aliphatic polyamines and aromatic amines, more preferably a mixture of polyethyleneimine, polyethylenepolyamine and any two of m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene.
According to the invention, the thicknesses of the bottom layer, the porous support layer and the separation layer are not particularly limited, and can be selected conventionally in the field, but in order to enable the three layers to have better synergistic cooperation, the obtained composite nanofiltration membrane can better have excellent acid and alkali resistance, higher water flux and higher desalination rate, and preferably, the thickness of the bottom layer is 30-150 μm, and preferably 50-120 μm; the thickness of the porous support layer is 10-100 μm, preferably 30-60 μm; the thickness of the polyurea separating layer is 10-500 nm, preferably 50-300 nm.
The invention also aims to provide a preparation method of the acid/alkali resistant composite nanofiltration membrane, which comprises the following steps:
(1) Preparing a porous support layer on one surface of the base layer:
(2) The polyurea separation layer is obtained by interfacial polymerization of a polyamine with a polyisocyanate on the other surface of the porous support layer.
According to the present invention, the method of step (1) may be selected conventionally in the art, and preferably by a phase inversion method, a porous support layer may be obtained by applying a polymer solution of a support layer material to one surface of a substrate layer and performing phase inversion.
The phase inversion process may preferably be: dissolving a polymer material of a support layer in a solvent to obtain a polymer solution with the concentration of 10-20 wt%, and defoaming at the temperature of 20-40 ℃ for 10-180 min; then coating the polymer solution on the bottom layer to obtain an initial membrane, soaking the initial membrane in water with the temperature of 10-30 ℃ for 10-60 min, and carrying out phase inversion layer on the support layer polymer porous membrane.
Among them, the solvent may be N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, or the like.
According to the present invention, the process of contacting the other surface of the porous support layer with the aqueous phase containing the polyamine and the organic phase containing the polyisocyanate in sequence in step (2) comprises: firstly, the porous supporting layer is contacted with water containing polyamine, drained, then contacted with organic phase containing polyisocyanate, and then heat treated.
According to the invention, the polyamine is one or a mixture of more of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, melamine, piperazine, ethylene diamine, 1,2-propane diamine, 1,4-butane diamine, diethylene triamine, tetraethylene pentamine, polyethylene imine and polyether amine; preferably an aliphatic polyamine mixed with an aromatic amine; more preferably a mixture of polyethyleneimine, polyethylenepolyamine, and any two of m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene. The polyisocyanate is one or more of m-xylylene diisocyanate, o-xylylene diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, toluene-2,6-diisocyanate, 1,4-phenylene diisocyanate, toluene-2,4-diisocyanate, 4,4 '-methylene bis (phenyl isocyanate), 1,3-phenylene diisocyanate, 3,3' -dichloro-4,4 '-diisocyanate biphenyl, dicyclohexylmethane-4,4' -diisocyanate, trimethylhexamethylene diisocyanate, m-xylylene diisocyanate, L-lysine ethyl ester-diisocyanate, 1,4-cyclohexyl diisocyanate, 4-chloro-6-methyl m-phenylene diisocyanate.
According to the present invention, the kind of the solvent of the organic phase is not particularly limited as long as the polyisocyanate can be dissolved, and preferably, the solvent of the organic phase is one or more of n-hexane, dodecane, n-heptane, alkane solvent oils (Isopar E, isopar G, isopar H, isopar L and Isopar M).
According to the invention, the concentration of polyamine and polyisocyanate in the interfacial polymerization process is not particularly limited as long as the obtained nanofiltration membrane can combine excellent acid and alkali resistance, high water flux and high salt rejection rate, preferably, the content of the polyamine is 0.2-10 wt%, more preferably 0.5-5 wt% in an aqueous phase containing the polyamine; wherein when the polyamine comprises aliphatic polyamine and aromatic amine, the mass ratio of the aliphatic polyamine to the aromatic amine is (0.05-100): 1, preferably (0.1 to 10): 1; the content of the polyisocyanate in the organic phase containing the polyisocyanate is 0.025 to 1% by weight, preferably 0.05 to 0.5% by weight.
According to the present invention, the mass concentration ratio of the polyamine to the polyisocyanate in the interfacial polymerization process is not particularly limited as long as the nanofiltration membrane obtained by the present invention has excellent acid and alkali resistance and high water flux and salt rejection rate, and the mass concentration ratio of the polyamine to the polyisocyanate is preferably (0.5 to 100): 1, more preferably (1 to 50): 1.
according to the invention, in the interfacial polymerization process, the contact time of the porous support layer with the water phase and the organic phase is not particularly limited as long as the obtained nanofiltration membrane has excellent acid and alkali resistance, high water flux and high desalination rate, and preferably, the contact time of the porous support layer with the water phase containing polyamine is 5-100 s, preferably 10-60 s; the time for contacting the polyisocyanate-containing organic phase is 10 to 200 seconds, preferably 20 to 120 seconds.
According to the invention, the post-treatment conditions of the interfacial polymerization are not particularly limited, as long as the monomers can be completely polymerized, and the nanofiltration membrane has excellent acid and alkali resistance, higher water flux and desalination rate, and preferably the heat treatment temperature is 40-150 ℃, and preferably 50-120 ℃; the heat treatment time is 0.5 to 20 minutes, preferably 1 to 10 minutes.
The invention also aims to provide the acid/alkali resistant composite nanofiltration membrane prepared by the preparation method provided by the invention.
The fourth purpose of the invention is to provide the composite nanofiltration membrane with acid/alkali resistance and the application of the composite nanofiltration membrane with acid/alkali resistance obtained by the preparation method in the field of water treatment.
The inventor of the present invention has found through intensive research that, on one hand, the polyurea functional layer provided by the present invention has a molecular structure containing both flexible chain breaks provided by aliphatic amine and stable rigid chain breaks provided by aromatic amine, the flexible chain breaks are beneficial to the improvement of water flux of the membrane, and the rigid chain breaks are beneficial to the improvement of acid/alkali resistance of the membrane, and by adjusting the ratio of the flexible chain breaks to the rigid chain breaks in the molecular structure, the composite nanofiltration membrane material having good water permeability and salt cut-off property and excellent acid/alkali resistance can be prepared. On the other hand, a large number of intermolecular hydrogen bonds (carbonyl and imino or amino groups in urea groups) can be formed in the molecular structure of the polyurea, and the molecular structure of the separation layer is more compact due to the existence of the hydrogen bonds, so that the stability of the separation layer in an acid/alkali medium is improved. The composite nanofiltration membrane can stably run in an aqueous solution with the pH value of 0-14, has high desalination rate and water permeability (water flux), has strong acid/alkali resistance, and has a simple preparation method and great industrial application prospect.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 shows the salt rejection and water flux of the composite nanofiltration membrane prepared in example 1 with H at 20% 2 SO 4 Variation of soaking time in aqueous solution;
figure 2 is a graph of salt rejection and water flux of the composite nanofiltration membrane prepared in example 1 as a function of soaking time in a 20% aqueous NaOH solution;
FIG. 3 is the salt rejection and water flux of the composite nanofiltration membrane prepared in example 1 as a function of the soaking time in a 20% phosphoric acid aqueous solution;
figure 4 is a graph of salt rejection and water flux of the composite nanofiltration membranes prepared in example 1 as a function of soaking time in 20% aqueous HCl.
Detailed Description
The following describes the embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
In the following examples and comparative examples:
(1) The water flux of the composite nanofiltration membrane is obtained by testing the following method: the composite nanofiltration permeable membrane is put into a membrane pool, after prepressing for 0.5 hour under 1.2MPa, the water permeability of the nanofiltration membrane within 1 hour is measured under the conditions of the pressure of 2.0MPa and the temperature of 25 ℃, and the water permeability is calculated by the following formula:
j = Q/(A.t), wherein J is water flux, Q is water permeability (L), and A is effective membrane area (m) of the composite nanofiltration membrane 2 ) T is time (h);
(2) The salt rejection of the composite nanofiltration membrane is obtained by testing the following method: loading the composite nanofiltration membrane into a membrane pool, prepressing for 0.5h under 1.2MPa, measuring the concentration change of the magnesium sulfate raw water solution with initial concentration of 2000ppm and the magnesium sulfate in the permeate liquid within 1h under the conditions of pressure of 2.0MPa and temperature of 25 ℃, and calculating by the following formula:
R＝(C p -C f )/C p x 100%, wherein R is the salt rejection, C p Is the concentration of magnesium sulfate in the stock solution, C f The concentration of magnesium sulfate in the permeate;
(3) And (3) testing the acid resistance of the composite nanofiltration membrane: the composite nanofiltration membrane membranes are respectively soaked in a solution containing 20 mass percent of H 2 SO 4 20% by mass of HCl and 20% by mass of H 3 PO 4 Soaking the composite nanofiltration membrane in the aqueous solution for 6 months, and then testing the change of the water flux and the salt rejection rate of the composite nanofiltration membrane every other week;
(4) And (3) testing alkali resistance of the composite nanofiltration membrane: the composite nanofiltration membrane is soaked in an alkali aqueous solution containing 20 mass percent of NaOH for 6 months, and then the changes of the water flux and the salt rejection rate of the composite nanofiltration membrane are tested every other week.
In addition, in the following examples and comparative examples:
branched polyethyleneimine (weight average molecular weight 25000), piperazine, m-phenylenediamine, 1,3,5-triaminobenzene, p-phenylenediamine, tetraethylenepentamine, diethylenetriamine, m-xylylene diisocyanate, 1,6-hexamethylene diisocyanate, toluene-2,6-diisocyanate, 1,4-phenylene diisocyanate, toluene-2,4-diisocyanate, polyethylene polyamine, 4,4' -methylenebis (phenyl isocyanate), 1,3-phenylene diisocyanate, 3,3' -dichloro-4,4 ' -diisocyanate biphenyl, o-xylylene diisocyanate, 4-chloro-6-methyl-m-phenylene diisocyanate, isophorone diisocyanate, 1,4-cyclohexyl diisocyanate, and the like are available from Bailingwei Tech Co., ltd, and other chemical reagents are available from pharmaceutical group Chemicals Ltd.
The supporting layer is prepared by adopting a phase inversion method, and the method comprises the following specific steps:
dissolving a certain amount of polysulfone (the number average molecular weight is 80000) in N, N-dimethylformamide to prepare a polysulfone solution with the concentration of 18 weight percent, and defoaming at 25 ℃ for 120min; then, the polysulfone solution was coated on a polyethylene nonwoven fabric (75 μm thick) using a doctor blade to obtain an initial film, which was then soaked in water at a temperature of 25 ℃ for 60min so that the polysulfone layer on the surface of the polyester nonwoven fabric was phase-converted into a porous film, and finally washed with water 3 times to obtain a film having a total thickness of 115 μm.
Example 1
Contacting the upper surface of the polysulfone supporting layer with an aqueous solution containing 1wt% of m-phenylenediamine and 1wt% of polyethyleneimine, and discharging liquid after contacting for 60s at 25 ℃; then, the upper surface of the supporting layer is contacted with Isopar E solution containing 0.2 weight percent of 4,4' -methylene bis (phenyl isocyanate) for 60s at the temperature of 25 ℃ and then discharged; and then, putting the membrane into an oven, and heating for 3min at 70 ℃ to obtain the composite nanofiltration membrane. The thickness of the separating layer was 215nm as measured by scanning electron microscopy.
Soaking the obtained composite nanofiltration membrane N1 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and pressure of 2.0MPa 4 The salt rejection of (2) is shown in Table 1. The membranes were immersed in 20 mass% of H, respectively 2 SO 4 20% by mass of HCl and 20% by mass of H 3 PO 4 And 20 mass percent NaOH in water solution for 6 months, and then testing the change of the water flux and the salt rejection rate of the composite nanofiltration membrane every other week, and the results are shown in figures 1-4.
Example 2
Contacting the upper surface of the polysulfone support layer with an aqueous solution containing 3 wt% of 1,3,5-triaminobenzene and 2 wt% of polyethylene polyamine, and draining after contacting for 60s at 25 ℃; then, the upper surface of the supporting layer is contacted with Isopar E solution containing 0.5 weight percent of 3,3 '-dichloro-4,4' -diisocyanate biphenyl, and liquid drainage is carried out after the contact for 60s at 25 ℃; and then, putting the membrane into an oven, and heating for 3min at 70 ℃ to obtain the composite nanofiltration membrane. The thickness of the separating layer was 248nm as measured by scanning electron microscopy.
Soaking the obtained composite nanofiltration membrane N2 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 3
Contacting the upper surface of the polysulfone support layer with an aqueous solution containing 0.3 wt% of p-phenylenediamine and 0.2 wt% of tetraethylenepentamine, and discharging liquid after contacting for 60s at 25 ℃; then, the upper surface of the supporting layer is contacted with Isopar E solution containing 0.05 weight percent of m-xylylene diisocyanate, and the liquid is discharged after the contact for 60s at 25 ℃; and then, putting the membrane into an oven, and heating for 3min at 70 ℃ to obtain the composite nanofiltration membrane. The thickness of the separating layer was 185nm as measured by scanning electron microscopy.
Soaking the obtained composite nanofiltration membrane N3 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 4
Contacting the upper surface of the polysulfone supporting layer with an aqueous solution containing 0.4 wt% of melamine and 0.1 wt% of piperazine, and discharging liquid after contacting for 60s at 25 ℃; then, the upper surface of the supporting layer is contacted with Isopar E solution containing 0.025 weight percent of 1,4-phenyl diisocyanate and is contacted for 60s at 25 ℃ for drainage; and then, putting the membrane into an oven, and heating for 3min at 70 ℃ to obtain the composite nanofiltration membrane. The thickness of the separating layer was 180nm as measured by scanning electron microscopy.
Soaking the obtained composite nanofiltration membrane N4 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 5
The preparation method of the composite nanofiltration membrane is carried out according to the embodiment 1, except that 1,3-phenylene diisocyanate is used to replace 4,4' -methylene bis (phenyl isocyanate) to obtain the composite nanofiltration membrane N5.
Soaking the obtained composite nanofiltration membrane N5 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 6
The preparation of the composite nanofiltration membrane was carried out as in example 1, with the difference that o-xylylene diisocyanate was used instead of 4,4' -methylenebis (phenylisocyanate) to give the composite nanofiltration membrane N6.
Soaking the obtained composite nanofiltration membrane N6 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 7
The preparation of a composite nanofiltration membrane was carried out as in example 1, with the difference that 4,4' -methylenebis (phenyl isocyanate) was replaced with 4-chloro-6-methyl-m-phenylene diisocyanate to give a composite nanofiltration membrane N7.
Soaking the obtained composite nanofiltration membrane N7 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 8
The process was carried out according to example 1 with the difference that isophorone diisocyanate was used instead of 4,4' -methylenebis (phenyl isocyanate) to give a composite nanofiltration membrane N8.
Soaking the obtained composite nanofiltration membrane N8 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane is respectively soaked in aqueous solutions of 20 mass percent of HCl and 20 mass percent of NaOH for 6 months, the water flux and the water flux of the composite nanofiltration membrane are testedThe salt rejection was as shown in Table 1.
Example 9
The preparation of the composite nanofiltration membrane was carried out according to example 1, with the difference that 1,4-cyclohexyl diisocyanate was used instead of 4,4' -methylenebis (phenyl isocyanate) to obtain the composite nanofiltration membrane N9.
Soaking the obtained composite nanofiltration membrane N9 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 10
The preparation of a composite nanofiltration membrane was carried out as in example 1, with the exception that m-phenylenediamine was used in an amount of 0.25 wt%, polyethyleneimine was used in an amount of 2.5 wt%, and 4,4' -methylenebis (phenylisocyanate) was used in an amount of 0.055 wt%, to give a composite nanofiltration membrane N10.
Soaking the obtained composite nanofiltration membrane N10 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 11
Contacting the upper surface of the polysulfone supporting layer with an aqueous solution containing 1wt% of m-phenylenediamine and 1wt% of polyethyleneimine, and discharging liquid after contacting for 60s at 25 ℃; then, the upper surface of the supporting layer is contacted with Isopar E solution containing 0.2 weight percent of toluene-2,6-diisocyanate and is discharged after being contacted for 60s at the temperature of 25 ℃; then, the membrane is placed in an oven and heated at 70 ℃ for 3min to obtain the composite nanofiltration membrane N11. The thickness of the separating layer was 205nm as measured by scanning electron microscopy.
Soaking the obtained composite nanofiltration membrane N11 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is as followsShown in table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 12
Contacting the upper surface of the polysulfone supporting layer with an aqueous solution containing 1wt% of m-phenylenediamine and 1wt% of polyethyleneimine, and discharging liquid after contacting for 60s at 25 ℃; then, the upper surface of the supporting layer is contacted with Isopar E solution containing 0.2 weight percent of toluene-2,4-diisocyanate, and is contacted for 60s at 25 ℃ for liquid drainage; then, the membrane is placed in an oven and heated at 70 ℃ for 3min to obtain the composite nanofiltration membrane N12. The thickness of the separating layer was 200nm as measured by scanning electron microscopy.
Soaking the obtained composite nanofiltration membrane N12 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 13
Contacting the upper surface of the polysulfone supporting layer with an aqueous solution containing 1wt% of m-phenylenediamine and 1wt% of polyethyleneimine, and discharging liquid after contacting for 60s at 25 ℃; then, the upper surface of the supporting layer is contacted with Isopar E solution containing 0.2 weight percent of 1,6-hexamethylene diisocyanate, and liquid drainage is carried out after the contact for 60s at 25 ℃; then, the membrane was placed in an oven and heated at 70 ℃ for 3min to obtain a composite nanofiltration membrane N13. The thickness of the separating layer was 215nm as measured by scanning electron microscopy.
Soaking the obtained composite nanofiltration membrane N13 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 14
Contacting the upper surface of the polysulfone supporting layer with an aqueous solution containing 0.5 weight percent of polyethyleneimine, and discharging liquid after contacting for 60s at 25 ℃; then, the upper surface of the supporting layer is contacted with Isopar E solution containing 0.025 weight percent of 1,4-phenyl diisocyanate and is contacted for 60s at 25 ℃ for drainage; and then, putting the membrane into an oven, and heating for 3min at 70 ℃ to obtain the composite nanofiltration membrane. The thickness of the separating layer was 188nm as measured by scanning electron microscopy.
Soaking the obtained composite nanofiltration membrane N14 in water for 24h, and measuring water flux and MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
Example 15
Contacting the upper surface of the polysulfone support layer with an aqueous solution containing 0.5wt% of polyethylene polyamine, and discharging liquid after contacting for 60s at 25 ℃; then, the upper surface of the supporting layer is contacted with Isopar E solution containing 4,4' -methylene bis (phenyl isocyanate) with the weight percent of 0.025 for 60s at 25 ℃ and then drained; and then, putting the membrane into an oven, and heating for 3min at 70 ℃ to obtain the composite nanofiltration membrane. The thickness of the separating layer was 193nm as measured by scanning electron microscopy.
Soaking the obtained composite nanofiltration membrane N15 in water for 24h, and measuring water flux and p-MgSO at 25 deg.C and 2.0MPa 4 The salt rejection of (2) is shown in Table 1. After the membrane was immersed in aqueous solutions of 20 mass% HCl and 20 mass% NaOH for 6 months, the water flux and salt rejection of the composite nanofiltration membrane were measured, and the results are shown in table 1.
As can be seen from FIGS. 1 to 4, the composite nanofiltration membrane using polyurea as the separation layer was 20 mass% H 2 SO 4 20% by mass of HCl and 20% by mass of H 3 PO 4 And 20 mass% NaOH in water, and soaking in the above extremely acidic or alkaline solution for more than 200 days for MgSO 4 The retention rate of the catalyst is still kept above 90 percent. The water flux increases significantly with increasing soaking time, indicating swelling of the polyurea cross-linked structure in extremely acidic or alkaline solutions.
TABLE 1 comparison of acid and base resistance of the example and comparative example films
Figure BDA0002443413270000151

Claims (16)

1. The composite nanofiltration membrane with acid/alkali resistance is characterized by comprising a bottom layer, a middle porous supporting layer and a surface separation layer, wherein the separation layer is a polyurea separation layer; the polyurea separation layer is obtained by carrying out interfacial polymerization on polyamine and polyisocyanate, wherein the polyisocyanate is selected from at least one of m-xylylene diisocyanate, o-xylylene diisocyanate, 1,4-phenylene diisocyanate, 4,4 '-methylene bis (phenyl isocyanate), 1,3-phenylene diisocyanate, 3,3' -dichloro-4,4 '-diisocyanate biphenyl, dicyclohexylmethane-4,4' -diisocyanate and 1,4-cyclohexyl diisocyanate; the polyamine comprises aliphatic polyamine and aromatic polyamine, wherein the aliphatic polyamine is selected from at least one of piperazine, diethylenetriamine, tetraethylenepentamine, polyethyleneimine, polyethylene polyamine and polyether amine, and the aromatic polyamine is selected from at least one of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene and melamine; the mass ratio of the aliphatic polyamine to the aromatic amine is (0.1 to 10): 1.
2. the composite nanofiltration membrane having acid/alkali resistance according to claim 1, wherein:
the material of the porous supporting layer is at least one of polyether sulfone, polysulfone, polyaromatic ether, polybenzimidazole, polyacrylonitrile, polyvinylidene fluoride and polyaryletherketone.
3. The composite nanofiltration membrane having acid/alkali resistance according to claim 1, wherein:
the thickness of the bottom layer is 30 to 150 mu m; the thickness of the porous supporting layer is 10 to 100 mu m; the thickness of the polyurea separation layer is 10 to 500nm.
4. The composite nanofiltration membrane having acid/alkali resistance according to claim 3, wherein:
the thickness of the bottom layer is 50 to 120 mu m; the thickness of the porous support layer is 30 to 60 micrometers; the thickness of the polyurea separation layer is 50 to 300nm.
5. A method for preparing a composite nanofiltration membrane having acid/alkali resistance according to any one of claims 1~4, comprising the steps of:
(1) Preparing a porous support layer on one surface of the base layer:
(2) The polyurea separation layer is obtained by interfacial polymerization of a polyamine with a polyisocyanate on the other surface of the porous support layer.
6. The preparation method of the composite nanofiltration membrane according to claim 5, wherein the preparation method comprises the following steps:
in the step (2), the other surface of the porous support layer is contacted with an aqueous phase containing polyamine and an organic phase containing polyisocyanate in sequence, and then heat treatment is performed.
7. The preparation method of the composite nanofiltration membrane according to claim 6, wherein the preparation method comprises the following steps:
in a water phase containing polyamine, the content of the polyamine is 0.2 to 10wt%; and/or the presence of a gas in the gas,
the content of the polyisocyanate in the organic phase containing the polyisocyanate is 0.025 to 1wt%.
8. The preparation method of the composite nanofiltration membrane according to claim 7, wherein the preparation method comprises the following steps:
in a water phase containing polyamine, the content of the polyamine is 0.5 to 5wt%; and/or the presence of a gas in the gas,
the content of the polyisocyanate in the organic phase containing the polyisocyanate is 0.05 to 0.5wt%.
9. The preparation method of the composite nanofiltration membrane according to claim 7, wherein the preparation method comprises the following steps:
the mass concentration ratio of the polyamine to the polyisocyanate is (0.5 to 100): 1.
10. the preparation method of the composite nanofiltration membrane according to claim 9, wherein the preparation method comprises the following steps:
the mass concentration ratio of the polyamine to the polyisocyanate is (1 to 50): 1.
11. the preparation method of the composite nanofiltration membrane according to claim 6, wherein the preparation method comprises the following steps:
the contact time of the porous support layer and the water phase containing polyamine is 5 to 100s; and/or the presence of a gas in the gas,
the time for the porous supporting layer to contact with the organic phase containing the polybasic isocyanate is 10 to 200s.
12. The preparation method of the composite nanofiltration membrane according to claim 11, wherein the preparation method comprises the following steps:
the contact time of the porous supporting layer and the water phase containing polyamine is 10 to 60s; and/or the presence of a gas in the gas,
the time for the porous support layer to contact with the organic phase containing the polybasic isocyanate is 20 to 120s.
13. The preparation method of the composite nanofiltration membrane according to claim 6, wherein the preparation method comprises the following steps:
the conditions of the heat treatment include: the heat treatment temperature is 40 to 150 ℃; the heat treatment time is 0.5 to 20 minutes.
14. The preparation method of the composite nanofiltration membrane according to claim 13, wherein the preparation method comprises the following steps:
the conditions of the heat treatment include: the heat treatment temperature is 50 to 120 ℃; the heat treatment time is 1 to 10 minutes.
15. An acid/alkali resistant composite nanofiltration membrane obtained by the preparation method according to any one of claims 5 to 14.
16. Use of the composite nanofiltration membrane with acid/alkali resistance according to any one of claims 1~4 or the composite nanofiltration membrane prepared by the preparation method according to any one of claims 5 to 14 in the field of water treatment.
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