CN116059854A - Preparation method of pollution-resistant nanofiltration membrane - Google Patents
Preparation method of pollution-resistant nanofiltration membrane Download PDFInfo
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- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 11
- 238000001035 drying Methods 0.000 claims description 10
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- 229920006393 polyether sulfone Polymers 0.000 claims description 3
- WZCQRUWWHSTZEM-UHFFFAOYSA-N 1,3-phenylenediamine Chemical compound NC1=CC=CC(N)=C1 WZCQRUWWHSTZEM-UHFFFAOYSA-N 0.000 claims description 2
- CBCKQZAAMUWICA-UHFFFAOYSA-N 1,4-phenylenediamine Chemical compound NC1=CC=C(N)C=C1 CBCKQZAAMUWICA-UHFFFAOYSA-N 0.000 claims description 2
- VILCJCGEZXAXTO-UHFFFAOYSA-N 2,2,2-tetramine Chemical compound NCCNCCNCCN VILCJCGEZXAXTO-UHFFFAOYSA-N 0.000 claims description 2
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims 4
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Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0079—Manufacture of membranes comprising organic and inorganic components
-
- 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
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
-
- 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
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/02—Inorganic material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/10—Catalysts being present on the surface of the membrane or in the pores
-
- 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 a preparation method of a pollution-resistant nanofiltration membrane, which is characterized in that a hydrogel is successfully grafted on the surface of a base membrane by using a polyamine-ultraviolet induced surface catalysis-free radical polymerization method. The hydrogel coating comprises a hydrophobic association network and a metal coordination network, wherein the hydrophobic association network is formed by copolymerizing 2-hydroxyphosphonoacetic acid and polyacrylamide, and the metal coordination network is obtained by coordination of calcium ions by xanthan gum. The method comprises three key steps: (1) Deposition of polyamine-Fe on substrate surface 3+ A coating; (2) Fe is added to 3+ Reduction of ions to Fe 2+ By ultraviolet irradiation with the aid of citric acid as active catalyst; (3) Free radical polymerization is performed in a hydrogel monomer solution at room temperature to grow a hydrogel coating. The composite membrane prepared by the invention effectively improves the membrane separation efficiency and the stain resistance, and is applied to the field of nanofiltration membrane preparation.
Description
Technical Field
The invention belongs to the technical field of membrane separation, and particularly relates to a preparation method of a pollution-resistant nanofiltration membrane.
Background
Filtration (NF) is one of the most important separation methods in the field of wastewater treatment. The filtration technology of the nano-filtration membrane is relatively late in development compared with other membrane separation technologies, the pore diameter of the nano-filtration is between UF and RO, the pore diameter is about 1nm, the boundary between UF and RO is cleared by the appearance of the nano-filtration, the nano-filtration membrane rapidly develops into the hot field with the unique advantages of the nano-filtration membrane, the charged substances can be separated by utilizing the small-range pore-size screening substances and the unique electrical property of the membrane surface, and the nano-filtration membrane has unique separation effect and application prospect due to the screening and the southward effect of the pore diameter.
Although nanofiltration membranes have many advantages in water treatment, membrane equipment reliability is reduced due to membrane pollution caused by concentration polarization and membrane hole blockage, and development of the nanofiltration membranes is greatly limited. Membrane pollution is mainly due to the hydrophobicity of the traditional membrane filtering material, and macromolecules, colloid, electrolyte and the like are extremely easy to be irreversibly deposited on the surface of the membrane or in the membrane holes, so that the membrane flux is continuously reduced, and the membrane separation process cannot be normally carried out. In addition, the membrane pollution accelerates the flux attenuation of the membrane in the use process, increases the energy consumption and severely limits the development of the membrane industry. One effective method for reducing membrane fouling is to improve membrane hydrophilicity, such as blend modification, surface coating, surface graft modification, and the like. Some hydrophilic polymers such as polyvinyl alcohol, chitosan and the like are deposited on the surface of a matrix film through electrostatic spinning to obtain nanofibers, and the prepared composite film has certain hydrophilicity and pollution resistance. However, the blending modification process is complex, the surface coating is easy to fall off, the surface grafting is difficult to obtain a uniform modified film, the electrostatic spinning preparation efficiency is too low, and the mechanical strength of the hydrophilic layer is poor. In recent years, some report crosslinking of reducing membrane pollution by coating or grafting hydrogel on the membrane surface is carried out to construct a hydrophilic gel layer on the polysulfone membrane surface, the hydrophilic gel layer has excellent hydrophilicity and permeability, and excellent anti-pollution capability is shown for an oil-water mixture and bovine serum albumin, and China patent document with publication No. CN113797763A discloses a method for codeposition coating modification of a hydrogel nanofiltration membrane, however, an active layer of the nanofiltration membrane prepared by the coating method is easy to fall off, and is not beneficial to industrialization. At present, many reports and patents on modified nanofiltration membrane materials exist, but the technology for preparing the hydrogel nanofiltration membrane based on a polyamine-ultraviolet induced surface catalysis-free radical polymerization method is not yet reported.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, improve the stability of a nanofiltration membrane and provide a preparation method of a pollution-resistant nanofiltration membrane.
In order to achieve the above purpose, the invention adopts the following technical scheme: a preparation method of a pollution-resistant nanofiltration membrane comprises the following steps:
(1) Deposition of polyamine coating:
pouring polyamine solution with the mass fraction of 0.2-0.4% on the surface of the base film, keeping for 20-50 min, and then washing and drying to obtain the base film deposited with the polyamine coating;
(2)Fe 2+ preparation of the catalyst:
weighing citric acid and ferric salt, adding water, and adding alkaline solution to adjust the pH value to be 3-5 to obtain mixed solution; then soaking the base film of the deposited polyamine coating prepared in the step (1) in the mixed solution for 30-60 min, and finally exposing the base film to ultraviolet light for 20-5 min0min to generate Fe in situ 2+ The method comprises the steps of carrying out a first treatment on the surface of the Wherein the mass fraction of the citric acid in the mixed solution is 0.2-0.5%, and the mass fraction of the ferric salt is 0.2-1%;
(3) Preparation of hydrogel monomer solution:
weighing xanthan gum and sodium dodecyl sulfate, dissolving in water, adding 2-hydroxyphosphonoacetic acid solution and polyacrylamide into the above solution, stirring, adding CaCl under stirring 2 Obtaining hydrogel monomer solution; wherein the mass fraction of the xanthan gum in the hydrogel monomer solution is 0.2-2%, the mass fraction of the sodium dodecyl sulfate is 4-10%, the mass fraction of the 2-hydroxyphosphonoacetic acid is 1-4%, the mass fraction of the polyacrylamide is 2-10%, and the CaCl is as follows 2 The mass fraction of (2) is 0.1-1%;
(4) Preparation of hydrogel coating on a base film:
immersing the base film after ultraviolet irradiation into a hydrogel monomer solution for free radical polymerization reaction for 5-10 min so as to grow a uniform hydrogel coating, washing and drying to obtain the pollution-resistant nanofiltration membrane.
Preferably, the polyamine in the step (1) is one or more of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, diethylenetriamine, triethylenetetramine or polyethyleneimine; the base membrane is polysulfone, polyethersulfone, polypropylene or polyacrylonitrile.
Preferably, the ferric salt in step (2) is FeCl 3 、Fe 2 (SO 4 ) 3 Or Fe (NO) 3 ) 3 One or more of the following.
Preferably, the alkaline solution in the step (2) is KOH, naOH or Ba (HO) 2 One or more of (a) and (b).
Preferably, the concentration of the alkaline solution in the step (2) is 0.5 to 2mol/L.
Preferably, the intensity of the ultraviolet light in the step (2) is 12-18 mW/cm 2 . The ultraviolet light wavelength range is 350-380 nm.
The invention uses a polyamine-ultraviolet induced surface catalysis-free radical polymerization method to successfully graft a hydrogel onto the surface of a base film. Such hydrogels include hydrophobic propertiesAn associative network and a metal coordination network, wherein the hydrophobic associative network is formed by copolymerizing 2-hydroxyphosphonoacetic acid-polyacrylamide, the metal coordination network is obtained by xanthan gum coordinated by calcium ions, and a compact hydrogen bond exists between the two networks. Polyamine-citric acid-Fe 3+ Fe of (3) 3+ The ions can be reduced to Fe with the aid of citric acid using ultraviolet radiation 2+ Ions, creating an active viscous catalyst initiation layer. Subsequently, fe in the monomer solution 2+ And S is equal to 2 O 8 2- The ions undergo solid-liquid interface oxidation-reduction reaction to generate free radical anions SO 4 2- . With a significant decrease in the decomposition activation energy, the polymerization of the monomers was initiated at room temperature.
The beneficial effects are that:
the preparation method of the invention can be grafted by various materials, thus improving the stability of the composite nanofiltration membrane.
Compared with the common method, the preparation method has stronger adhesive force, and the coating is not easy to fall off, thereby being beneficial to industrialization.
Drawings
FIG. 1 is a scanning electron microscope image of the nanofiltration membrane prepared in example 1.
Detailed Description
The present invention will be described in further detail with reference to the following specific embodiments. It will be appreciated by those skilled in the art that the following examples are illustrative of the present invention and should not be construed as limiting the scope of the invention.
The composite nanofiltration membrane prepared by the invention can be used for intercepting salt ions, so that the desalination rate, the water flux and the stain resistance are three important parameters for evaluating the composite nanofiltration membrane.
The test conditions for water flux and desalination rate were: the dead-end filtration device had an inorganic salt concentration of 1000mg/L, a test temperature of 25 ℃, ph=7, and a test pressure of 0.6MPa.
The desalination rate is defined as:
wherein R represents the retention rate, C p And C f The concentration of the permeate and the concentration of the feed solution are respectively.
The water flux (LMH) is defined as: water volume per unit time through the active area of the membrane.
The antifouling properties of the films were measured using BSA as a simulated contaminant. Each filtration experiment contained three cycles, each cycle having the following steps: (1) Filtering with pure water for 30min to obtain P 1 The method comprises the steps of carrying out a first treatment on the surface of the (2) Using BSA solution for 1h to obtain P 2 The method comprises the steps of carrying out a first treatment on the surface of the (3) The membrane was rinsed with pure water for 20 minutes, and then filtered with pure water for 30 minutes to obtain P 3 . Membrane flux recovery (FRR) can be obtained by an equation.
Membrane flux recovery (FRR) is defined as:
example 1:
pouring a polyethyleneimine solution with the mass fraction of 0.2% on the surface of a polyethersulfone ultrafiltration membrane for 20min, and then washing and drying to obtain a base membrane deposited with a polyamine coating; weighing citric acid and FeCl 3 Adding water solution, adding 1mol/L KOH solution to stabilize pH at about 4, and adding citric acid 0.2% by mass, feCl 3 Is 0.2% by mass; then soaking the base film deposited with the polyamine coating in the mixed solution for 30min; finally, the base film was exposed to ultraviolet light (380 nm,12 mW/cm) 2 ) 20min to generate Fe in situ 2+ The method comprises the steps of carrying out a first treatment on the surface of the Weighing xanthan gum and sodium dodecyl sulfate, dissolving the xanthan gum and the sodium dodecyl sulfate in an aqueous solution, wherein the mass fraction of the xanthan gum is 0.2%, and the mass fraction of the sodium dodecyl sulfate is 4%; then adding 2-hydroxyphosphonoacetic acid and polyacrylamide into the above solution, stirring, and adding CaCl under stirring 2 The mass fraction of the 2-hydroxyphosphonoacetic acid is 1%, the mass fraction of the polyacrylamide is 2%, and CaCl is used for preparing the catalyst 2 Is 0.1% by mass; immersing the base film after ultraviolet irradiation into a monomer solution for 5min of free radical polymerization reaction to grow a uniform hydrogel coating, washing and drying to obtain the nanofiltration membrane.
An SEM image of the composite nanofiltration membrane prepared in example 1 is shown in fig. 1. The surface of the composite nanofiltration membrane is smooth as can be seen from the figure.
The mass fractions of xanthan gum in examples 2 to 4 were 0.8%, 1.6% and 2%, respectively, and the other conditions were the same as in example 1. The performance of the composite nanofiltration membranes prepared in examples 1 to 4 was tested, and the results are shown in table 1.
TABLE 1 Water flux, mgSO, of nanofiltration membranes prepared in examples 1-4 4 Desalination rate and membrane flux recovery rate.
As can be seen from the analysis of Table 1, the composite nanofiltration membranes prepared in examples 1-4 have higher flux and inorganic salt rejection rate, the surface of the composite nanofiltration membrane in the SEM image is smoother, the membrane recovery rate is stably maintained above 90%, and the effectiveness of the nanofiltration membrane preparation method is verified.
Comparative example 1:
comparative example 1 the mass fraction of xanthan gum was 2.5% and the other conditions were the same as in example 1.
The flux of the nanofiltration membrane is 25.3LMH, mgCl 2 The desalination rate was 93.2% and the membrane flux recovery was 92%. At this time, the flux of the nanofiltration membrane is significantly reduced due to excessive crosslinking.
Example 5:
pouring 0.3 mass percent o-phenylenediamine solution on the surface of a polysulfone ultrafiltration membrane for 30min, and then washing and drying to obtain a base membrane deposited with a polyamine coating; weighing citric acid and Fe 2 (SO 4 ) 3 Adding water solution, adding 0.5mol/L NaOH solution to stabilize pH at about 3, citric acid with mass fraction of 0.4%, fe 2 (SO 4 ) 3 Is 0.6% by mass; then soaking the base film deposited with the polyamine coating in the mixed solution for 30min; finally, the base film was exposed to ultraviolet light (365 nm,15mW/cm 2 ) For 30min to generate Fe in situ 2+ The method comprises the steps of carrying out a first treatment on the surface of the Weighing xanthan gum and sodium dodecyl sulfate, dissolving the xanthan gum and the sodium dodecyl sulfate in an aqueous solution, wherein the mass fraction of the xanthan gum is 1%, and the mass fraction of the sodium dodecyl sulfate is 7%; then, adding to the above solutionStirring 2-hydroxy phosphonoacetic acid and polyacrylamide, and adding CaCl under stirring 2 3% of 2-hydroxyphosphonoacetic acid, 6% of polyacrylamide and CaCl 2 Is 0.6% by mass; immersing the base film after ultraviolet irradiation into a monomer solution for 8min of free radical polymerization reaction to grow a uniform hydrogel coating, washing and drying to obtain the nanofiltration membrane.
Examples 6 to 8
The mass fractions of 2-hydroxyphosphonoacetic acid in examples 6 to 8 were 1%,2%,4%, respectively, and the other conditions were the same as in example 5.
The performance of the composite nanofiltration membranes prepared in examples 5 to 8 was tested, and the results are shown in table 2.
TABLE 2 Water flux, mgSO, of nanofiltration membranes prepared in examples 5-8 4 Desalination rate and membrane flux recovery rate.
As can be seen from the analysis of Table 2, the composite nanofiltration membranes prepared in examples 5-8 have higher flux and inorganic salt rejection rate, the surface of the composite nanofiltration membrane in the SEM image is smoother, the membrane recovery rate is stably maintained above 90%, and the effectiveness of the nanofiltration membrane preparation method is verified.
Example 9:
pouring a diethylenetriamine solution with the mass fraction of 0.4% on the surface of a polyacrylonitrile ultrafiltration membrane for 30min, and then washing and drying to obtain a base membrane deposited with a polyamine coating; weighing citric acid and Fe (NO) 3 ) 3 Adding an aqueous solution and adding 2mol/L of Ba (HO) 2 The pH of the solution is stabilized at about 5, the mass fraction of citric acid is 0.5%, fe (NO) 3 ) 3 Is 1% by mass; then soaking the base film deposited with the polyamine coating in the mixed solution for 50min; finally, the base film was exposed to ultraviolet light (350 nm,18mW/cm 2 ) For 30min to generate Fe in situ 2+ The method comprises the steps of carrying out a first treatment on the surface of the Weighing xanthan gum and sodium dodecyl sulfate, dissolving in water solution, wherein the mass fraction of the xanthan gum is 2%, and the twelve isThe mass fraction of the sodium alkyl sulfate is 10%; then adding 2-hydroxyphosphonoacetic acid and polyacrylamide into the above solution, stirring, and adding CaCl under stirring 2 The mass fraction of the 2-hydroxyphosphonoacetic acid is 4%, the mass fraction of the polyacrylamide is 10%, and CaCl is used for preparing the polymer 2 Is 1% by mass; immersing the base film after ultraviolet irradiation into a monomer solution for 10min of free radical polymerization reaction to grow a uniform hydrogel coating, washing and drying to obtain the nanofiltration membrane.
Examples 10 to 12
The free radical polymerization times of examples 10 to 12 were 5min,7min and 9min, respectively, and the other conditions were the same as in example 9.
The performance of the composite nanofiltration membranes prepared in examples 9 to 12 was tested, and the results are shown in table 3.
TABLE 3 Water flux, mgSO, of nanofiltration membranes prepared in examples 9-12 4 Desalination rate and membrane flux recovery rate.
As can be seen from the analysis of Table 3, the composite nanofiltration membranes prepared in examples 9-12 have higher flux and inorganic salt rejection rate, the surface of the composite nanofiltration membrane in the SEM image is smoother, the membrane recovery rate is stably maintained above 90%, and the effectiveness of the nanofiltration membrane preparation method is verified.
Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein.
Claims (7)
1. A preparation method of a pollution-resistant nanofiltration membrane comprises the following steps:
(1) Deposition of polyamine coating:
pouring polyamine solution with the mass fraction of 0.2-0.4% on the surface of the base film, keeping for 20-50 min, and then washing and drying to obtain the base film deposited with the polyamine coating;
(2)Fe 2+ preparation of the catalystThe preparation method comprises the following steps:
weighing citric acid and ferric salt, adding water, and adding alkaline solution to adjust the pH value to be 3-5 to obtain mixed solution; then soaking the base film of the deposited polyamine coating prepared in the step (1) in the mixed solution for 30-60 min, and finally exposing the base film to ultraviolet light for 20-50 min to generate Fe in situ 2+ The method comprises the steps of carrying out a first treatment on the surface of the Wherein the mass fraction of the citric acid in the mixed solution is 0.2-0.5%, and the mass fraction of the ferric salt is 0.2-1%;
(3) Preparation of hydrogel monomer solution:
weighing xanthan gum and sodium dodecyl sulfate, dissolving in water, adding 2-hydroxyphosphonoacetic acid solution and polyacrylamide into the above solution, stirring, adding CaCl under stirring 2 Obtaining hydrogel monomer solution; wherein the mass fraction of the xanthan gum in the hydrogel monomer solution is 0.2-2%, the mass fraction of the sodium dodecyl sulfate is 4-10%, the mass fraction of the 2-hydroxyphosphonoacetic acid is 1-4%, the mass fraction of the polyacrylamide is 2-10%, and the CaCl is as follows 2 The mass fraction of (2) is 0.1-1%;
(4) Preparation of hydrogel coating on a base film:
immersing the base film after ultraviolet irradiation into a hydrogel monomer solution for free radical polymerization reaction for 5-10 min so as to grow a uniform hydrogel coating, washing and drying to obtain the pollution-resistant nanofiltration membrane.
2. The process according to claim 1, wherein the polyamine in the step (1) is one or more of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, diethylenetriamine, triethylenetetramine and polyethyleneimine; the base membrane is polysulfone, polyethersulfone, polypropylene or polyacrylonitrile.
3. The process according to claim 1, wherein the trivalent iron salt in step (2) is FeCl 3 、Fe 2 (SO 4 ) 3 Or Fe (NO) 3 ) 3 One or more of the following.
4. The process according to claim 1, wherein the alkaline solution in the step (2) is KOH, naOH or Ba (HO) 2 One or more of (a) and (b).
5. The process according to claim 1, wherein the concentration of the alkaline solution in the step (2) is 0.5 to 2mol/L.
6. The process according to claim 1, wherein the ultraviolet light in step (2) has an intensity of 12 to 18mW/cm 2 。
7. The method according to claim 1, wherein the ultraviolet light in the step (2) has a wavelength ranging from 350 to 380nm.
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