CN111744368A

CN111744368A - Organic/inorganic hybrid membrane material based on ultra-small-size EMT molecular sieve, preparation method and application in water treatment

Info

Publication number: CN111744368A
Application number: CN202010586704.7A
Authority: CN
Inventors: 范黎黎; 孔国栋; 康子曦; 孙道峰
Original assignee: China University of Petroleum East China
Current assignee: China University of Petroleum East China
Priority date: 2020-06-24
Filing date: 2020-06-24
Publication date: 2020-10-09
Anticipated expiration: 2040-06-24
Also published as: CN111744368B

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to an organic/inorganic hybrid membrane material of an EMT type molecular sieve, a preparation method and application of the membrane material in the aspect of dye separation. The invention adopts an interfacial polymerization method to prepare a brand new organic/inorganic hybrid membrane material on a polyether sulfone carrier, and the preparation steps are as follows: (1) preparing an ultra-small-size EMT molecular sieve; 2) preparing an aminated EMT molecular sieve; (3)EMT‑NH₂Preparation of the organic/inorganic hybrid membrane of (1). The material can combine the unique advantages of inorganic nanoparticles, and avoids the phenomenon of retention rate reduction caused by non-selective pores in the traditional TFN membrane.

Description

Organic/inorganic hybrid membrane material based on ultra-small-size EMT molecular sieve, preparation method and application in water treatment

Technical Field

The invention belongs to the technical field of sewage treatment, and particularly relates to an organic/inorganic hybrid membrane material of an EMT type molecular sieve, a preparation method and application of the membrane material in the aspect of dye separation.

Background

The per capita water resource occupancy of China is only 1/4 of the per capita water resource occupancy of the world, and is behind 120 of the world. Moreover, the regional distribution is not uniform, and the water and soil resources are not matched, so that the water resources in China are more in short supply. Aiming at the problem of water resource shortage in China, the recycling of non-traditional water resources (industrial wastewater, municipal sewage and circulating sewage) is very important. The traditional water treatment methods at present comprise an adsorption method, a chemical coagulation method, an electrochemical oxidation method and the like, and the methods have the defects of mature technology, high energy consumption, high equipment investment and complex operation. The emerging membrane separation technology has the characteristics of high efficiency, energy conservation, simple equipment, convenient operation and the like, and is more and more widely applied in the field of water treatment. The membrane separation method is a general name for separation, classification, purification and enrichment methods of double-component or multi-component solute and solvent by using natural or artificial membrane and using external energy or chemical potential difference as driving force. Membrane materials have been extensively studied as a key to membrane separation technology, and various new materials have been prepared as membranes for separation.

Separation membrane materials can be mainly classified into polymeric membranes and inorganic membranes according to composition. The current commercialized polymeric membrane has the advantages of low cost, good flexibility, high separation selectivity and easy processing and molding. But also has poor thermal stability and chemical stability, and has the balance problem of flux and selectivity during separation. This is determined by the sieving mechanism of the membrane, with the selectivity of the reduced pore size membrane increasing, but the flux inevitably decreases.

Inorganic porous membranes generally include ceramic membranes, metal membranes, alloy membranes, silicon carbide membranes, molecular sieve composite membranes, molecular sieve membranes, glass membranes, and the like. Compared with organic films, the material characteristics and the excellent performance of the inorganic film are mainly represented as follows: (1) excellent chemical stability (2) wide temperature application range (3) high separation efficiency, narrow pore size distribution and asymmetric membrane structure, which can significantly improve the removal rate of characteristic pollutants or solutes in a specific molecular weight range; (4) the mechanical strength is high, the device is more suitable for separating complex fluid materials with high viscosity, high solid content and hard particles, and the pretreatment requirement on the materials is relatively low. However, inorganic film materials also face challenges, such as the inorganic materials being brittle and less elastic, which can cause difficulties in the film formation and assembly.

The membrane composite membrane is a separation membrane which is formed by taking a microporous membrane or an ultrafiltration membrane as a supporting layer and covering the surface of the microporous membrane or the ultrafiltration membrane with a dense homogeneous membrane with the thickness of only 0.1-0.25 mu m as a barrier polyamide layer. So that the permeation amount of the substance is greatly increased. The membrane has the advantages of keeping the advantages of low cost, easy processability and the like of the polymer membrane, and improving the separation performance of the original material. The initial research was mainly to obtain a separation layer with separation properties on a microfiltration or ultrafiltration membrane substrate by interfacial polymerization between two organic monomers. Although the flux of the composite membrane prepared by the method is greatly improved compared with that of the common polymer membrane, the separation property of the composite membrane is still required to be further improved. The film nano-material composite film prepared by adding some inorganic nano-particles into the polyamide layer can combine the advantages of uniform aperture of inorganic materials and easy preparation of polymer films. However, since the inorganic nanoparticles are not well bonded to the polymer, defects are generated and the selectivity of the film is lowered. The improvement of the membrane performance is realized by changing the monomer in the interfacial polymerization process, and a new idea is provided for solving the problem. At present, some molecules with special properties are used as novel monomers to prepare the thin film composite membrane, but the selection of the monomers is still limited to organic molecules, and the unique advantages of inorganic nanoparticles cannot be further combined.

Disclosure of Invention

The invention relates to an organic/inorganic hybrid membrane material of an EMT type molecular sieve, a preparation method thereof and application thereof in dye separation in aqueous solution.

The invention adopts an interfacial polymerization method to prepare a brand new organic/inorganic hybrid membrane material on a polyether sulfone carrier, and the preparation steps are as follows:

(1) preparation of ultra-small-size EMT molecular sieve

Solution a was prepared by dissolving 9.074g of sodium aluminate (56.2% Al2O3, 39.5% Na2O) and 1.61g of sodium hydroxide in 100.00g of deionized water, then mixing with 44.00g of sodium hydroxide to obtain a clear suspension; solution B was prepared by adding 57.692g of sodium silicate (27% SiO2, 8% Na2O) and 20.00g of sodium hydroxide in a 250mL bottle with 80g of DI water, then stirring until the solution was completely clear; both solutions were cooled in an ice bath (277K); then, slowly adding the solution A into the solution B under vigorous stirring to form turbid suspension; the suspension was stirred continuously for 5 minutes and then kept at 303K over 36 hours, after which the mixture was separated by centrifugation and washed with deionized water until pH 8 to obtain a white powder by freeze drying.

(2) Preparation of aminated EMT molecular sieve

Mixing APTES (H)₂NCH₂CH₂CH₂Si(OC₂H₅)₃) Putting into 150ml round bottom flask with EMT type molecular sieve according to the molar ratio of 2mmol:1g, adding 80ml anhydrous toluene, stirring and refluxing at 110 deg.C for 12h with constant temperature magnetic stirrer, stopping refluxing, cooling, and centrifuging colorless mixed liquid in round bottom flask to obtain white powdery solid. Washed with toluene and filtered to obtain white powder. And putting the white powder into a vacuum drying oven, and performing vacuum drying for 12h at 55 ℃ to obtain the amino functionalized EMT type molecular sieve.

(3)EMT-NH₂Preparation of organic/inorganic hybrid film

Respectively weighing 0.025g, 0.05g and 0.075g of the amino-functionalized EMT type molecular sieve prepared in the step (2) and dissolving in 100ml of water, and carrying out ultrasonic treatment for 20min to prepare aqueous phase solutions A with the concentrations of 0.025% (m/v), 0.05% (m/v) and 0.075% (m/v); weighing 0.02g of trimesoyl chloride, dissolving in 100ml of cyclohexane, and stirring for 5min to prepare an oil phase solution B with the concentration of 0.02% (m/v); and (3) putting 25ml of the solution A into a beaker, putting the cut polyether sulfone base membrane into the bottom of the solution A, slowly introducing the solution B into the beaker of the solution A, standing for reaction for a period of time, slowly pulling the base membrane out of the page, and airing at room temperature.

Has the advantages that:

the invention adopts an interfacial polymerization method to prepare a brand-new organic/inorganic hybrid membrane material on a polyether sulfone carrier, and the material can combine the unique advantages of inorganic nano particles and avoid the phenomenon of retention rate reduction caused by non-selective pores in the traditional TFN membrane. Firstly, the EMT molecular sieve is synthesized under mild conditions (303K), and a structure directing agent is not used, so that the consumption of energy and chemicals can be reduced; secondly, the generation of defects can be reduced as much as possible by constructing the ultra-small EMT molecular sieve; finally, the preparation of the EMT molecular sieve into the membrane by a simple interfacial polymerization method is simple in operation and easy to enlarge.

Drawings

FIG. 1: composition diagrams of M1, M2, M3 and M4 films;

FIG. 2: XRD patterns of the EMT type molecular sieves of examples 1-4;

FIG. 3: XRD diffraction patterns of the organic/inorganic hybrid films M1, M2, M3 in examples 1-3;

FIG. 4: scanning electron micrographs of the films of the organic/inorganic hybrid films M1, M2, M3, M4 of examples 1 to 3;

FIG. 5: examples 1-4 comparative graphs of dye separation performance;

wherein: (a) methyl blue separation performance graphs of M1, M2, M3 and M4;

(b) graph of separation performance of M2 for different types of dyes;

(c) comparison of separation performance of polyamide, TFN-EMT, organic/inorganic hybrid membrane on methyl blue.

In fig. 1: to compare the separation properties of different types of membranes for dyes in aqueous solution, different types of membranes were prepared, including 0.025%, 0.05%, 0.075% molecular sieve concentration of M1, M2, M3 (polymerization time: 10min) and 0.05% concentration of M4 (polymerization time: 20 min).

FIG. 2 is a powder XRD diffraction pattern of the EMT type molecular sieves of examples 1-4, comparing the simulated XRD diffraction patterns, we can speculate that the EMT molecular sieves were successfully obtained by the low temperature hydrothermal method.

FIG. 3 is an XRD diffraction pattern of the organic/inorganic hybrid film in examples 1-3. We can see that three broadened peaks at the same position appear in the XRD spectra of the three films, but it is proved that the broadened peaks are characteristic peaks of PES of the film substrate material, and characteristic peaks representing the presence of the EMT molecular sieve are not found, because the incorporation amount of the EMT molecular sieve is relatively small, so the intensity of the diffraction peaks is much weaker than that of the molecular film itself, and the broadened peaks cannot be detected in the diffraction precision used in the test.

FIG. 4 is a front scanning electron micrograph of M1, M2, M3, M4 prepared in examples 1-3. From the pictures we can clearly see that the surface of M1 is rougher than M2, and as the concentration of molecular sieve increases, the degree of surface roughening also increases. This indicates that the morphology of the membrane can be achieved by varying the concentration of the aqueous molecular sieve solution.

FIG. 5 is a graph comparing the separation performance of dyes in examples 1-4. From comparison in the figure we can see that M1, which has the lowest EMT concentration, has the highest flux, but the rejection is slightly lower compared to other membranes; and the flux of the membrane is gradually reduced with the increase of the EMT concentration, and the retention rate gradually approaches 100%. This is because when the polymerization time is fixed, the thickness of the membrane increases with increasing concentration of molecular sieve, so the rejection rate increases and the flux decreases; comparing the separation properties of M2 membrane to different types of dyes, the retention effect of adding organic/inorganic hybrid membrane to either positive or negative dyes is very good, which shows that the organic/inorganic hybrid membrane fully exerts the sieving performance advantage of inorganic nano particles and avoids the retention rate reduction phenomenon caused by non-selective pores in the traditional TFN membrane.

Detailed Description

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Accordingly, the description herein is of preferred examples for the purpose of illustration only and is not intended to limit the scope of the present invention, so it will be understood that other equivalent implementations and modifications may be made without departing from the spirit and scope of the present invention.

Example 1:

(1) preparation of ultra-small-size EMT molecular sieve

(2) Preparation of aminated EMT molecular sieve

APTES (H2NCH2CH2CH2Si (OC2H5)3) and EMT type molecular sieve are put into a 150ml round-bottom flask according to the molar ratio of 2mmol:1g, 80ml of anhydrous toluene is added, stirring and refluxing are carried out for 12H at 110 ℃ by using a constant-temperature magnetic stirrer, then the refluxing is stopped, cooling is carried out, and a colorless mixed liquid in the round-bottom flask is centrifugally separated to obtain a white powdery solid. Washed with toluene and filtered to obtain white powder. And putting the white powder into a vacuum drying oven, and performing vacuum drying for 12h at 55 ℃ to obtain the amino functionalized EMT type molecular sieve.

(3) Preparation of organic/inorganic hybrid membrane of EMT-NH2

Respectively weighing 0.025g of the amino-functionalized EMT type molecular sieve prepared in the step (2), dissolving the amino-functionalized EMT type molecular sieve in 100ml of water, and performing ultrasonic treatment for 20min to prepare aqueous phase solutions A with the concentration of 0.25% (m/v) respectively; weighing 0.02g of trimesoyl chloride, dissolving in 100ml of cyclohexane, and stirring for 5min to prepare an oil phase solution B with the concentration of 0.02% (m/v); and (3) putting 25ml of the solution A into a beaker, putting the cut polyether sulfone base membrane into the bottom of the solution A, then slowly introducing the solution B into the beaker of the solution A, standing for reaction for 10min, slowly pulling the base membrane out of the page, and airing at room temperature to obtain the M1 membrane.

(4) Characterization of the membranes

And performing powder XRD diffraction pattern test on the EMT molecular sieve powder, and performing SEM and methylene blue separation performance test on the prepared membrane. The separation performance test is shown in table 1.

Table 1: dye separation Performance test

Flux is the volume of water permeated per unit of membrane area per unit time.

Example 2

(1) Preparation of ultra-Small size EMT-type molecular sieves according to example 1, step 1

(2) Aminated EMT molecular sieves prepared according to example 1, step 2

(3) Respectively weighing 0.05g of the amino-functionalized EMT type molecular sieve prepared in the step (2), dissolving the amino-functionalized EMT type molecular sieve in 100ml of water, and performing ultrasonic treatment for 20min to prepare aqueous phase solutions A with the concentration of 0.05% (m/v) respectively; weighing 0.02g of trimesoyl chloride, dissolving in 100ml of cyclohexane, and stirring for 5min to prepare an oil phase solution B with the concentration of 0.02% (m/v); and (3) putting 25ml of the solution A into a beaker, putting the cut polyether sulfone base membrane into the bottom of the solution A, then slowly introducing the solution B into the beaker of the solution A, standing for reaction for 10min, slowly pulling the base membrane out of the page, and airing at room temperature to obtain the M2 membrane.

(4) And performing a powder XRD diffraction pattern test on the EMT molecular sieve powder, and performing a separation performance test on the prepared membrane by SEM, methylene blue, crystal violet and methyl blue. The separation performance test is shown in table 2.

Table 2: dye separation Performance test

	Retention (%)	Flux (L.m)^-2·h-1·bar^-1)
			Methylene blue	99.7	107.5
Crystal violet	99.5	110.3
			Methyl blue	99.8	109.7

And (3) preparing the aminated EMT molecular sieve according to the preparation method, changing the standing reaction time in the step (3), after standing reaction for 20min, slowly pulling the base membrane out of the page, and airing at room temperature to obtain the M4 membrane.

Example 3

(2) Aminated EMT molecular sieves prepared according to example 1, step 2

(3) Respectively weighing 0.075g of the amino-functionalized EMT type molecular sieve prepared in the step (2), dissolving the amino-functionalized EMT type molecular sieve in 100ml of water, and carrying out ultrasonic treatment for 20min to prepare aqueous phase solutions A with the concentrations of 0.075% (m/v); weighing 0.02g of trimesoyl chloride, dissolving in 100ml of cyclohexane, and stirring for 5min to prepare an oil phase solution B with the concentration of 0.02% (m/v); and (3) putting 25ml of the solution A into a beaker, putting the cut polyether sulfone base membrane into the bottom of the solution A, then slowly introducing the solution B into the beaker of the solution A, standing for reaction for 10min, slowly pulling the base membrane out of the page, and airing at room temperature to obtain the M3 membrane.

(4) And performing powder XRD diffraction pattern test on the EMT molecular sieve powder, and performing SEM and methyl blue separation performance test on the prepared membrane. The separation performance test is shown in table 3.

Table 3: dye separation Performance test

Example 4

(2) Aminated EMT molecular sieves prepared according to example 1, step 2

(3) Respectively weighing 0.05g of the amino-functionalized EMT type molecular sieve prepared in the step (2), dissolving the amino-functionalized EMT type molecular sieve in 100ml of water, and performing ultrasonic treatment for 20min to prepare aqueous phase solutions A with the concentration of 0.05% (m/v) respectively; weighing 0.02g of trimesoyl chloride, dissolving in 100ml of cyclohexane, and stirring for 5min to prepare an oil phase solution B with the concentration of 0.02% (m/v); and (3) putting 25ml of the solution A into a beaker, putting the cut polyether sulfone base membrane into the bottom of the solution A, slowly introducing the solution B into the beaker of the solution A, standing for reaction for 20min, slowly pulling the base membrane out of the page, and airing at room temperature to obtain the M3 membrane.

(4) And performing powder XRD diffraction pattern test on the EMT molecular sieve powder, and performing SEM and methyl blue separation performance test on the prepared membrane. The separation performance test is shown in table 4.

Table 4: dye separation Performance test

	Retention (%)	Flux (L.m)^-2·h^-1·bar^-1)
			Methyl blue	99.7	60.9

Claims

1. A preparation method of an organic/inorganic hybrid membrane material based on an ultra-small-size EMT molecular sieve is characterized by comprising the following preparation steps:

(1) preparation of ultra-small-size EMT molecular sieve

Solution a was prepared by dissolving 9.074g of sodium aluminate and 1.61g of sodium hydroxide in 100.00g of deionized water, then mixing with 44.00g of sodium hydroxide to obtain a clear suspension; solution B was prepared by adding 57.692g of sodium silicate and 20.00g of sodium hydroxide to a 250mL bottle containing 80g of DI water, and then stirring until the solution was completely clear; both solutions were cooled in an ice bath; then, slowly adding the solution A into the solution B under vigorous stirring to form turbid suspension; the suspension was stirred continuously for 5 minutes and then kept at 303K over 36 hours, after which the mixture was separated by centrifugation and washed with deionized water until pH 8 to obtain a white powder by freeze-drying;

(2) preparation of aminated EMT molecular sieve

Placing APTES and EMT type molecular sieve into a 150ml round bottom flask, adding 80ml anhydrous toluene, stirring and refluxing for 12h at 110 ℃ by using a constant-temperature magnetic stirrer, stopping refluxing, cooling, and centrifugally separating colorless mixed liquid in the round bottom flask to obtain white powdery solid; washing with toluene, performing suction filtration to obtain white powder, and putting the white powder into a vacuum drying oven to perform vacuum drying for 12 hours at 55 ℃ to obtain the amino functionalized EMT type molecular sieve;

(3)EMT-NH₂preparation of organic/inorganic hybrid film

Respectively weighing and dissolving the amino-functionalized EMT type molecular sieve prepared in the step (2) in water, and performing ultrasonic treatment for 20min to obtain an aqueous phase solution A; weighing trimesoyl chloride, dissolving the trimesoyl chloride in cyclohexane, and stirring to prepare an oil phase solution B with the concentration of 0.02 percent m/v; and (3) putting the solution A into a beaker, putting the cut polyether sulfone base membrane into the bottom of the solution A, then slowly introducing the solution B into the beaker of the solution A, standing, slowly pulling the base membrane out of the page, and airing at room temperature.

2. The preparation method of the organic/inorganic hybrid membrane material based on the ultra-small-sized EMT molecular sieve according to claim 1, wherein the step (3) is as follows:

respectively weighing 0.025g, 0.05g and 0.075g of the amino-functionalized EMT type molecular sieve prepared in the step (2), dissolving in 100ml of water, and performing ultrasonic treatment for 20min to prepare aqueous phase solutions A with the concentrations of 0.025% m/v, 0.05% m/v and 0.075% m/v respectively; 0.02g of trimesoyl chloride is weighed and dissolved in 100ml of cyclohexane, and the mixture is stirred for 5min to prepare oil phase solution B with the concentration of 0.02 percent m/v; and (3) putting 25ml of the solution A into a beaker, putting the cut polyether sulfone base membrane into the bottom of the solution A, then slowly introducing the solution B into the beaker of the solution A, standing, slowly lifting the base membrane out of the page, and airing at room temperature.

3. The preparation method of the organic/inorganic hybrid membrane material based on the ultra-small-sized EMT molecular sieve in the claim 1, wherein the molar ratio of APTES to EMT molecular sieve in the step (2) is 2mmol:1 g.

4. The method for preparing organic/inorganic hybrid membrane material based on ultra-small-sized EMT molecular sieve according to claim 1, wherein Al in sodium aluminate is Al₂O₃56.2 percent of Na by mass₂The mass percent of O is 39.5%.

5. The preparation method of the organic/inorganic hybrid membrane material based on the ultra-small-sized EMT molecular sieve as claimed in claim 1, wherein SiO in the sodium silicate₂27% by mass of Na₂The mass percent of O is 8%.

6. The method for preparing the organic/inorganic hybrid membrane material based on the ultra-small-sized EMT molecular sieve according to claim 1, wherein the two solutions are both cooled in an ice bath at 277K.

7. Organic/inorganic hybrid membrane material based on ultra-small-sized EMT molecular sieve obtained by the preparation method according to claims 1-3.

8. Use of the ultra-small-sized EMT molecular sieve based organic/inorganic hybrid membrane material according to claim 4 for dye separation.