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Method for preparing polyvinylidene fluoride composite cellulose acetate forward osmosis membrane

A technology of polyvinylidene fluoride and cellulose acetate, which is applied in the field of membrane separation, can solve the problems of low porosity, low flux, and internal concentration polarization of the support layer, and achieve the reduction of internal concentration polarization and high The effect of high salt rejection rate and high mechanical strength

Active Publication Date: 2012-07-18
NINGBO INST OF MATERIALS TECH & ENG CHINESE ACADEMY OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Since polysulfone is relatively hydrophobic, researchers have added polyethersulfone and sulfonated polyethersulfone to polysulfone to improve the hydrophilicity of the composite forward osmosis membrane and improve its flux, but its flux is still far from Meet practical application requirements
At present, there are more studies on cellulose acetate forward osmosis membrane. The membrane has an asymmetric structure and consists of a dense skin and a porous support layer. However, the skin is thick and the porosity of the support layer is low. The actual flux of the membrane is very low.
In short, the current forward osmosis membranes dedicated to the forward osmosis process are all due to the serious internal concentration polarization phenomenon, and the actual flux is very low. The membrane materials specially used for the forward osmosis process are still in the research and development stage.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] Step (1). Add 300 grams of polyvinylidene fluoride, 300 grams of dimethylformamide, 200 grams of triethyl phosphate and 200 grams of polyethylene glycol into the container in order, and stir for 48 hours at 50 ° C; then depressurize Degassing to 0.05MPa for 5 hours to obtain a uniformly dispersed polyvinylidene fluoride casting solution;

[0026] Step (2). Add 80 grams of cellulose acetate, 150 grams of cellulose triacetate, 750 grams of dimethylformamide, and 20 grams of A-type molecular sieve into the container in order, and stir at 30°C for 24 hours; then reduce the pressure to 0.05 MPa degassing for 5 hours to obtain a uniformly dispersed cellulose acetate casting solution;

[0027] Step (3). Use a scraper with a thickness of 300 microns to evenly scrape the polyvinylidene fluoride casting solution on the non-woven fabric, and then immerse it in a mixed solution of water and dimethylformamide with a volume ratio of 2:8 at 8°C Take it out after 15 seconds, and then ...

Embodiment 2

[0032] Step (1). Add 80 grams of polyvinylidene fluoride, 400 grams of dimethylformamide, 400 grams of dimethylacetamide and 120 grams of polymaleic anhydride into the container in order, and stir for 12 hours at 120 ° C; then reduce Press to 0.1MPa to degas for 10 hours to obtain uniformly dispersed polyvinylidene fluoride casting solution;

[0033] Step (2). Add 350 grams of cellulose acetate, 50 grams of cellulose triacetate, 550 grams of dimethylacetamide, and 50 grams of X-type molecular sieves into the container in order, and stir for 6 hours at 90° C.; then reduce the pressure to 0.1 MPa degassing for 10 hours to obtain a uniformly dispersed cellulose acetate casting solution;

[0034] Step (3). Use a scraper with a thickness of 250 microns to evenly scrape the polyvinylidene fluoride casting solution on the non-woven fabric, and then immerse it in a mixed solution of water and dimethylacetamide with a volume ratio of 2:8 at 15°C Take it out after 10 seconds, and then ...

Embodiment 3

[0039] Step (1). Add 230 grams of polyvinylidene fluoride, 750 grams of triethyl phosphate and 20 grams of polyvinylpyrrolidone into the container in sequence, and stir at 80°C for 24 hours; then reduce the pressure to 0.5MPa and defoam for 15 hours to obtain Uniformly dispersed polyvinylidene fluoride casting solution;

[0040]Step (2). Add 175 grams of cellulose acetate, 20 grams of cellulose triacetate, 800 grams of methylpyrrolidone, and 5 grams of Y-type molecular sieve into the container in order, and stir for 18 hours at 60 ° C; Soak for 15 hours to obtain a uniformly dispersed cellulose acetate casting solution;

[0041] Step (3). Use a scraper with a thickness of 200 microns to evenly scrape the polyvinylidene fluoride casting solution on the non-woven fabric, and then immerse it in a mixed solution of water and triethyl phosphate with a volume ratio of 3:7 at 40°C , take it out after 5 seconds, and then immerse it in a deionized water bath at 40°C; after film format...

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Abstract

The invention relates to a method for preparing a polyvinylidene fluoride composite cellulose acetate forward osmosis membrane. The conventional product has a serious inside concentration polarization phenomenon and low actual flux. The method comprises the following steps of: preparing a polyvinylidene fluoride cast membrane solution from polyvinylidene fluoride and additive; preparing a cellulose acetate cast membrane solution from cellulose acetate, cellulose triacetate and molecular sieve; and uniformly coating the polyvinylidene fluoride cast membrane solution on a non-woven fabric to obtain a hydrophilic polyvinylidene fluoride micro-filtration base membrane, drying or naturally drying in air to form a dry hydrophilic polyvinylidene fluoride membrane, uniformly coating the cellulose acetate cast membrane solution on the dry hydrophilic polyvinylidene fluoride membrane, and thus obtaining the composite forward osmosis membrane. The forward osmosis membrane prepared by the method has high mechanical strength and solvent tolerance, high water flux and high salt intercepting rate, and can be applied in the fields of desalting of seawater and brine, softening of hard water, first-aid water bags and the like.

Description

technical field [0001] The invention belongs to membrane separation technology, and in particular relates to a preparation method of polyvinylidene fluoride composite cellulose acetate forward osmosis membrane. Background technique [0002] Forward osmosis technology is a new type of membrane separation technology developed in recent years. It uses the osmotic pressure difference on both sides of the membrane as the driving force, and has the advantages of low energy consumption, high recovery rate, and low pollution. Forward osmosis technology has broad application prospects in seawater desalination, energy, food processing, industrial wastewater treatment, aerospace and other fields. Strong, high flux, high rejection forward osmosis membrane. The commercialized reverse osmosis membrane has an asymmetric structure, its sub-layer structure is relatively dense, and its porosity is not high. When used in forward osmosis, there is a serious internal concentration polarizat...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01D69/12B01D71/34B01D71/16
Inventor 薛立新刘富丁辉陈景
Owner NINGBO INST OF MATERIALS TECH & ENG CHINESE ACADEMY OF SCI
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