TWI414346B - A filtration material for desalination - Google Patents

Abstract

The invention provides a filtration material for desalination, comprising: a support layer, and a desalination layer formed on the support layer, wherein the desalination layer is a fiber composite filtration membrane, and at least one of the fiber composite filtration membrane comprises a water-swellable polymer.

Description

Desalting filter material

The present invention relates to a desalination filter material, and more particularly to a desalination filter material composed of a water-swellable polymer.

All major plants around the world are actively developing various desalting filter materials for seawater, industrial water and wastewater. In addition to high-efficiency treatment of water salts and the desire to reduce operating pressure, low-energy consumption can reduce the cost of clean water treatment.

U.S. Patent No. 4,828,700 discloses the use of a polymethyl methacrylate series of polymers for crosslinking reaction to prepare a seawater desalination film having a desalination condition of 250 psi, a flux of 9.1 GFD and a desalting rate of 97.9% in 2000 ppm of brine.

U.S. Patent No. 5,464,538 discloses an ethylene monomer containing a positive ion which is subjected to a crosslinking reaction to produce a film which also has a desalination condition of 2,500 ppm of brine at a pressure of 400 psi, a 3.59 GFD flux and a 91.8% salt rejection.

U.S. Patent No. 5,755,964 discloses a filter material which utilizes an amine compound to treat the surface of the RO membrane to increase the wettability of the membrane so that the RO membrane has a desalting condition of 2000 psi in 2000 ppm saline, 48 GFD flux up to nanofiltration. The level of material (nanofilteration).

However, the conventional desalting filter material is mainly a nonporous polymeric thin film which needs to be operated under high pressure conditions. Therefore, if a hydrophilic desalination filter material can be proposed, it is helpful to reduce the operating pressure. And improve the desalination filtration effect.

The present invention provides a filter medium for desalination, comprising: a support layer; and a desalination layer formed on the carrier layer, wherein the desalting layer is a composite fiber membrane And a composite fiber membrane comprising at least one water-swellable polymer.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

The present invention provides a filter medium for deslination consisting of a support layer and a desalting layer formed on the carrier layer, wherein the carrier layer is used to carry the desalting layer, and the desalting layer is A fiber composite membrane comprising at least one water-swellable polymer. The term "water-swellable polymer" as used herein means that the polymer itself can be expanded by absorbing water, and the polymer can absorb a large amount of water without causing it to dissolve in water to deform its structure. The water swellable polymer is a non-water soluable polymer composed of hydrophilic monomers and hydrophobic monomers. In addition, the water-moisturizing polymer may also be a water soluable polymer which reduces water decomposability via a suitable crosslinking reaction but still retains water wettability.

The carrier layer comprises one or more porous materials, wherein the porous material comprises a cellouse ester, a polysulfone, a polyacrylonitrile (PAN), a polyvinylidene fluoride (polyvinylidene fluoride). PVDF), polyetheretherketone (PEK), polyester (PET), polyimide (PI), chlorinated polyvinyl chloride (PVC) or styrene-acrylonitrile copolymer (styrene acrylnitrile, SAN), etc., and the carrier layer can be synthesized by itself or commercially available. Further, the porous material can be present in the form of a nonwoven fabric, a woven fabric or an open pores material.

In one embodiment, the desalting filter material uses two carrier layers, the bottom layer is polyester (PET), the upper layer is polyacrylonitrile (PAN) or polysulfone, and the carrier layer can be woven or The form of non-woven fabric exists, preferably in the form of non-woven fabric.

The hydrophilic monomer of the water-swellable polymer may be an ionic monomer or a non-ionic monomer.

The ionic monomer includes a cationic monomer and an anionic monomer, and the cationic monomer includes acryloxyethyltrimethyl ammonium chloride, propylene oxyethylate Acryloxyethyltrimethyl benzyl ammonium chloride, methacryloxyethyltrimethyl ammonium chloride, methacryloxyethyltrimethyl-p-toluenesulfonate (methacryloethyltrimethyl p-toluenesulfonate), methacryloyloxyethyl dimethylbenzyl ammonium chloride, dimethylaminoethyl acrylate, tert-butylamine ethyl T-butylaminoethyl methacrylate, vinyl imidazole or vinyl pyridine.

Anionic monomers include acrylic acid, methacrylic acid, itaconic acid, beta-carboxyethyl acrylate, maleic anhydride ( Maleic anhydride), or a sodium salt of the above acid, such as sodium acrylate, sodium 1-allyloxy-2-hydroxypropane sulfonate, allyloxyethoxy Amylium allylpolyethoxy sulfate, sodium styrene sulfonate or 2-acrylamido-2-methyl propane sulfonic acid.

Nonionic monomers include hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, acrylamide, N-hydroxyoxyethyl propylene oxime N-hydroxyethyl acrylamide, polyvinylpyrolidone.

The hydrophobic monomer of the water-repellent polymer includes methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate. , methyl methacrylate, t-butyl methacrylate, styrene or vinylidine fluoride. Further, although the monomers of acrylonitrile and methacrylonitrile are water-soluble, the polymer composed thereof can also be used as a hydrophobic monomer.

In addition, in order to strengthen the mechanical strength of the composite fiber membrane, a cross-linking agent may be added to the cross-linking reaction with the water-moisturizable polymer, and the crosslinking agent may be hydrophilic with the water-soluble polymer. The functional group or hydrophobic functional group is reacted (preferably with a hydrophilic functional group) to reduce the solubility of the water swellable polymer. The crosslinking agent includes an acid anhydride, an epoxy, an isocyanate, an amino resin (a reaction of formaldehyde with melamine, urea or guanamine), and a carbodiimide ( Carbodiimide), aziridine or a derivative as described above.

In one embodiment, the maleic anhydride is crosslinked with a hydroxyl group of a hydrophilic functional group of the water-stable polymer. In another embodiment, the epoxy resin is crosslinked with a carboxyl group, a hydroxyl group or an amine of a hydrophilic functional group of a water-moistible polymer. In another embodiment, the isocyanate is crosslinked with a hydroxyl group of a hydrophilic functional group of a water-swellable polymer. In yet another embodiment, the melamine-formaldehyde resins are crosslinked with hydroxyl, amide, and carboxyl groups of the hydrophilic functional group of the water-soluble polymer. reaction. In another embodiment, the carbodiimide or aziridine is cross-linked with a carboxyl group of a hydrophilic functional group of the water-stable polymer.

In addition to chemical bonds for cross-linking reactions, ionic bonds can also be used for ionic crosslinking, such as multi-chlorinated hydrocarbons. Quaternary ammonium chloride. In one embodiment, the 1,6-dichlorohexane is reacted with an amine group of a hydrophilic functional group of a water-soluble polymer to form a quaternary ammonium salt to achieve a salt ion crosslinking reaction (quaternization reaction). For ionic crosslinking).

In addition, the hydrophilic functional group of the water-moisturizing polymer can also be polymerized with a crosslinkable monomer, such as N-isobutoxymethyl acrylamide. .

In addition, the water swellable polymer may be composed of a modified polymer, such as polyvinyl alcohol, hydroxyethyl cellulose or carboxymethyl cellulose. Wherein the polyvinyl alcohol is a hydrolysis product of polyvinyl acetate, and the hydroxyethoxy cellulose is an addition reaction of ethylene oxide and cellulose. product.

In addition, the composite fiber membrane of the present invention is in the form of a fiber and a binder, wherein the water-swellable polymer can be made into a fiber by a spinning method, and the spinning method includes solution spinning. Or electrospinning. Thereafter, a binder or a dipping method may be used to fill the binder pores in the pores of the web, and press the rollers or plates to densify the structure. A composite fiber membrane can be formed.

The binder may be the water swellable polymer or other polymer of the present invention, and other polymers such as polyvinyl alcohol (PVA), polystyrene (PS), polyacrylamides, Polymethacrylamides, polymethacrylates, polyacrylates, polyesters, hydroxyethyl cellulosic or hydroxypropyl cellulose .

The role of the binder is to enhance the mechanical strength of the desalting filter material and to reduce the pores on the surface of the desalination layer.

In addition, other crosslinking agents may be added to the binder to avoid solubilization of the composite fiber membrane and to enhance the mechanical strength of the composite fiber membrane. For example, a methylated melamine-formaldehyde resin, such as hexamethoxymethylmelamine, may be added to the binder to react with the hydroxyl group of the composite fiber membrane to The solubility of the composite fiber membrane is changed (solubility).

In one embodiment, the water-swellable polymer is first formed into fibers by an electrospinning method, and then polyacrylonitrile (PAN) is added as a binder to form a composite fiber membrane.

In another embodiment, polyacrylonitrile (PAN) may be formed into fibers by an electrospinning method, and then a water-swellable polymer may be added as a binder to prepare a composite fiber membrane.

In another preferred embodiment, the water swellable polymer is first formed into a fiber by an electrospinning method, and then another water swellable polymer is used as a binder to form a composite fiber film.

The fiber of the composite fiber membrane of the present invention comprises microfiber or nanofiber, the diameter of the microfiber is about 1 m to 30 m, or 1 m to 15 m, and the diameter of the nanofiber is about 10 Nm~1000 nm, or 50 nm~500 nm.

Since the conventional RO membrane pore size is very small (less than 1 nm), it is usually required to pressurize to 500 psi or even up to 1000 psi to produce water. Compared with the RO membrane, the greatest advantage of the present invention is that the applied pressure is small. The amount of water close to the RO membrane is reached. The desalting filter material of the present invention is subjected to desalination test, and the effluent flow rate is more than 18 L/m ² /hr, the pressure is less than 10 psi, and the desalination efficiency is about 60% to 95%.

Compared with the prior art, the open pores of the fiber composite membrane provided by the present invention can be used as an effective desalting filter membrane, and therefore, the desalination effect can be achieved under low pressure conditions. It should be noted that the desalting filter material of the present invention only needs a carrier layer plus a desalting layer to achieve the effect of desalting filtration, and those skilled in the art can add other conventional membranes according to the needs of practical applications. , semi-permeable membrane or other polymer film.

In summary, since the desalting filter material of the present invention comprises a composite fiber membrane, the composite fiber membrane has a porous property and is effective for desalting reaction, so that at a low pressure, it still has a high flux, and therefore, the desalination effect can be effectively improved. The desalination filter material of the present invention can be applied to a desalination process, wastewater treatment, ultrapure water treatment, water softening or precious metal recovery.

While the invention has been described above in terms of several preferred embodiments, it is not intended to limit the scope of the present invention, and any one of ordinary skill in the art can make any changes without departing from the spirit and scope of the invention. And the scope of the present invention is defined by the scope of the appended claims.

[Examples]

ratio Comparative example 1

Comparative Example 1 consisted of only two layers of carrier, the bottom layer being polyester (PET) non-woven fabric (purchased from Heyou Textile, HO YU TEXTILE CO., LTD), and the upper layer being polyacrylonitrile (PAN). PAN is purchased from TONGHWA synthetic fiber CO. Ltd., having a molecular weight of about 150,000 to 300,000.

Comparative example 2

The material of Comparative Example 1 was used as a carrier layer to prepare a polyacrylonitrile (PAN) cotton web by electrospinning method: 30 g of polyacrylonitrile (PAN) was dissolved in 200 g of N,N-dimethyl After N,N-dimethyl acetamide (DMAc), the voltage is 39 kV, the total throughput is 1000 L/min, the air pressure is 2.8 kg/cm ² , and the distance between the spinning nozzle and the receiving belt is 25 cm. A fiber web having a fiber diameter of about 280 nm to 380 nm and a basis weight of 30 to 60 g/m ² . 3 g polystyrene (PS) (purchased from Aldrich) (adhesive) was dissolved in 27 g of p-xylene, coated on a polyacrylonitrile nanofiber cotton web, and the reaction temperature was 70 ° C for 1 hour. After that, a composite fiber membrane is produced.

Example 1

Making water swellable polymer

10 g of sodium styrene sulfonate, 40 g of 4-vinylpyridine, 7 g of styrene, 50 g of deionized water and 50 g of isopropanol were placed in a reaction flask and heated to 70 ° C under nitrogen. After dissolving 0.2 g of potassium persulfate (KPS) as a starter in 10 mL of deionized water, the mixture was poured into a reaction flask and stirring was continued for 3 hours, after which a product of 50.1 g was obtained by a precipitation purification step, and the yield was 88%.

Example 2

Taking the polymer of the present invention into a nanofiber cotton web

After 36 g of the polymer of the example (1) was dissolved in 200 g of N,N-dimethylacetamide (DMAc), the nanofiber cotton web was prepared by electrospinning: voltage 39 kV, total throughput 1200 L/min, air pressure 5 kg/cm ² , distance from the nozzle to the receiving belt of 20 cm, can produce a diameter of about 70 nm-120 nm, and the basis weight of the cotton net is 60-94 g/ m ² nanofiber cotton mesh.

Example 3

Commercially available polymers are made into nanofiber cotton mesh

30g of polyacrylonitrile (PAN) polymer was dissolved in 200 g of N, N-dimethyl acetamide (DMAc), and the nanofiber cotton web was prepared by electrospinning. : The voltage is 39 kV, the total throughput is 1000 L/min, the air pressure is 2.8 kg/cm ² , and the distance from the nozzle to the receiving belt is 25 cm. The diameter of the nanofiber is about 280 nm-380 nm, and the basis weight is 30~. 60 g/m ² nanofiber cotton mesh.

Example 4

The material of Comparative Example 1 was used as a carrier layer.

The desalting layer was prepared as follows: 3 g of the polymer of Example 1 (adhesive) was dissolved in 27 g of alcohol, and 2.1 g of 1,6-dichlorohexane (crosslinking agent) was added to prepare a homogeneous solution. The nanofiber cotton web of Example 2 was applied and reacted at a temperature of 70 ° C for 4 hours to prepare a composite fiber membrane.

Example 5

The material of Comparative Example 1 was used as a carrier layer.

The desalting layer was prepared as follows: 0.6 g of the polymer of Example 1 (adhesive) was dissolved in 29.4 g of alcohol, and 0.42 g of 1,6-dichlorohexane (crosslinking agent) was added to prepare a homogeneous solution. The nanofiber cotton web of Example 3 was applied and reacted at a temperature of 70 ° C for 4 hours to prepare a composite fiber membrane.

Example 6

The material of Comparative Example 1 was used as a carrier layer.

The desalting layer was prepared as follows: 3 g of a commercially available PS polymer (adhesive) was dissolved in 27 g of p-xylene, and coated on the nanofiber cotton web of Example 2 , and reacted at a temperature of 70 ° C. After 1 hour, a composite fiber membrane was produced.

Example 7

The material of Comparative Example 1 was used as a carrier layer.

The desalting layer was prepared as follows: 3 g of the polymer of Example 1 (adhesive) was dissolved in 27 g of alcohol, and 2.1 g of 1,6-dichlorohexane (crosslinking agent) was added to prepare a homogeneous solution. It was applied to a commercially available polypropylene (PP) cotton web and reacted at a temperature of 70 ° C for 4 hours to prepare a composite fiber membrane.

Example 8

The material of Comparative Example 1 was used as a carrier layer.

The desalting layer was prepared as follows: 10 g of commercially available polyvinyl alcohol (PVA) (Changchun, ChangChun Group) (adhesive) was dissolved in 90 g of water, and 0.01 g of maleic anhydride (MA) was added ( The cross-linking agent was prepared into a uniform solution, and applied to the nanofiber cotton web of Example 3 , and reacted at a temperature of 70 ° C for 4 hours to prepare a composite fiber membrane.

Table 1 shows the desalting efficiencies of Comparative Examples 1 and 2 and Examples 4 to 8. As can be seen from Table 1, the desalting filter material prepared by using the water-stable polymer of the present invention has the best desalting efficiency. The desalting efficiency is 50~95%.

Claims (19)

A salt-rejecting filtration material comprising: a support layer; and a desalination layer formed on the carrier layer, wherein the desalting layer is a composite fiber membrane (fiber) Composite membrane), and the composite fiber membrane comprises at least one water-swellable polymer, wherein the composite fiber membrane is in the form of a fiber and a binder, and the fiber Including microfiber or nanofiber. The desalination filter material of claim 1, wherein the carrier layer comprises one or more layers of porous material. The desalination filter material according to claim 1, wherein the porous material comprises a cellouse ester, a polysulfone, a polyacrylonitrile (PAN), a polyvinglidene fluoride. , PVDF), polyetheretherketone (PEK), polyester (PET), polyimide (PI), chlorinated polyvinyl chloride (PVC) or styrene-acrylonitrile copolymer Styrene acrylnitrile (SAN). The desalination filter material according to claim 1, wherein the water-swellable polymer is composed of hydrophilic monomers and hydrophobic monomers, wherein the water is hydrophilic. The singular monomer includes an ionic monomer or a non-ionic monomer, and the ionic monomer includes a cationic single Bulk and anionic monomers. The desalting filter material according to claim 4, wherein the cationic monomer comprises acryloxyethyltrimethyl ammonium chloride, propylene oxyethyl trimethyl benzyl chloride Acryloxyethyltrimethyl benzyl ammonium chloride, methacryloxyethyltrimethyl ammonium chloride, methacryloxyethyltrimethyl p-toluenesulfonate, Methacryloyloxyethyl dimethylbenzyl ammonium chloride, dimethylaminoethyl acrylate, t-butylaminoethyl Methacrylate), vinyl imidazole or vinyl pyridine. The desalting filter material according to claim 4, wherein the anionic monomer comprises acrylic acid, methacrylic acid, itaconic acid, β-carboxyl Beta-carboxyethyl acrylate, maleic anhydride or the sodium salt of the above acid. The desalting filter material according to claim 4, wherein the nonionic monomer comprises hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, Acrylamide, N-hydroxyethylethyl decylamine (N-hydroxyethyl) Acrylamide or polyvinylpyrolidone. The desalting filter material according to claim 4, wherein the hydrophobic monomer comprises methyl acrylate, ethyl acrylate, butyl acrylate, and acrylic acid-2-B. 2-ethylhexyl acrylate, methyl methacrylate, t-butyl methacrylate, styrene or vinylidine fluoride. The desalting filter material according to claim 1, wherein the water-moisturizable polymer can be cross-linked with a crosslinking agent. The desalting filter material according to claim 9, wherein the crosslinking agent comprises an acid anhydride, an epoxy, an isocyanate, an aminoplast resin, an alkoxy group. Alkoxymethyl acrylamide, carbodiimide, aziridine or a derivative thereof. The desalting filter material according to claim 10, wherein the acid anhydride is cross-linked with a hydroxyl group of the water-moisturizable polymer. The desalting filter material according to claim 10, wherein the epoxy resin is cross-linked with a carboxyl group, a hydroxyl group or an amine of the water-moisturizable polymer. The desalting filter material according to claim 10, wherein the isocyanate is crosslinked with a hydroxyl group of the water-soluble polymer. a desalting filter material as described in claim 10, The aminoplast resins are crosslinked with a hydroxyl group, a carboxyl group or an amide of the water-soluble polymer. The desalting filter material according to claim 10, wherein the alkoxymethyl acrylamide is crosslinked with a hydroxyl group of the water-wettable polymer. The desalting filter material according to claim 10, wherein the carbodiimide or aziridine is cross-linked with a carboxyl group of the water-stable polymer. The desalting filter material according to claim 9, wherein the crosslinking reaction comprises performing an ion crosslinking reaction. The desalting filter material according to claim 17, wherein the ion crosslinking reaction is carried out by reacting a multi-chlorinated hydrocarbon with an amine of the water-soluble polymer to form a quaternary ammonium salt. salt. The desalting filter material according to claim 1, wherein the water swellable polymer comprises polyvinyl alcohol, carboxymethyl cellulose or hydroxyethyl cellulose. .