CN1321727C - Novel reverse osmosis antioxidant compound membrane of polyamide and its preparing method - Google Patents

Abstract

The invention discloses a novel polyamide reverse osmosis composite membrane and a preparation method thereof. The reverse osmosis composite membrane prepared by the method can achieve better effects on water flux and desalination rate. The invention is to form an ultra-thin functional membrane through polymerization or polycondensation reaction of polymer materials with good hydrophilicity, mechanical stability and other characteristics on the porous support membrane according to certain process steps and controlled certain process conditions. The method for preparing the composite film has a simple process and relatively well-controlled process conditions, thereby reducing costs and further facilitating the popularization and use of high-performance, relatively expensive polymer composite materials. The invention can be widely used in the separation of various liquids, especially in the separation of aqueous solution, and can be used as a process for the preparation of pure water or sewage treatment.

Description

A novel oxidation-resistant polyamide reverse osmosis composite membrane and its preparation method

technical field

The invention belongs to a novel polyamide reverse osmosis composite membrane and a preparation method thereof.

Background technique

The reverse osmosis composite membrane is to deposit an ultra-thin functional layer on the surface of a microporous support membrane with an appropriate pore size. The deposition methods mainly include surface coating, interfacial polycondensation and in-situ polymerization.

Composite membranes have many advantages over asymmetric membranes: it allows each layer to be tailored for optimum performance. The ultra-thin functional layer can be optimized to the ideal permselectivity, and the support membrane can achieve the best strength and pressure tightness. In addition, composite membranes can make materials that are difficult to form asymmetric membranes form ultra-thin films. For example, due to solvent limitations and cross-linked polymers, composite membranes can be formed by in-situ polymerization or interfacial condensation; ultra-thin films can be made of high-performance ( Expensive) new materials.

The salt rejection rate and water flux are two important parameters for evaluating reverse osmosis membranes. The salt rejection rate R is defined as: under certain operating conditions, the difference between the salt concentration of the feed liquid (c _f ) and the salt concentration of the permeate (c _p ) The difference is divided by the feed liquid salt concentration.

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}$

Water flux is defined as: under certain operating conditions, the volume of water passing through a unit membrane area per unit time, and its unit is 1/m ² .h.

The operating conditions adopted in the present invention are: 2000mg/L sodium chloride aqueous solution, the operating pressure is 1.0-1.6MPa, and the operating temperature is 22°C-25°C.

Polyamide has amide functional groups (-CO-NH-), good hydrophilicity, and good mechanical stability, thermal stability and hydrolytic stability, especially suitable for reverse osmosis process. The reverse osmosis membrane obtained by compounding a layer of aromatic polyamide ultra-thin functional layer on the polysulfone support membrane through interfacial polycondensation has become the composite membrane variety with the best comprehensive performance at present.

US Patent 4,277,344 such as Cadotte in 1981 adopts interfacial polycondensation method on the polysulfone supporting membrane by interfacial polycondensation composite layer aromatic polyamide thin film, and this film is that the polysulfone supporting membrane is immersed in the buffer solution of m-phenylenediamine, squeezed dry Finally, cover with trimesoyl chloride solution, rinse after reacting for a period of time, and carry out post-treatment. The ultra-thin functional layer of the film is mainly cross-linked aromatic polyamide, and its chemical structural formula can be expressed as:

In US Patent 4,761,234 in 1988, Uemura et al. used interfacial polycondensation method to use trimethylenetriamine as a crosslinking agent, and reacted with isophthaloyl chloride on a support membrane to compound a layer of aromatic polyamide film, and the desalination rate was greater than 99%. But its used phenylenediamine is difficult to obtain. The chemical structural formula of the aromatic polyamide in the composite ultra-thin functional layer can be expressed as:

In addition, US Patent 5,576,057, US Patent 5,989,426, US Patent 6,162,358, US Patent 6,464,873 and other patents also immerse the polysulfone support membrane in the polyamine aqueous solution, squeeze it dry and then immerse it in the polyacyl chloride solution, rinse and carry out after a period of reaction. Post-processing to get the product.

Contents of the invention

The purpose of the present invention is to prepare a novel reverse osmosis composite membrane, the composite membrane ultra-thin functional layer contains amide functional group (-CO-NH-), also contains urea functional group (-NH-CO-NH-) or amine The carbamate functional group (-OCO-NH-) improves the hydrophilicity of the ultra-thin functional layer. In addition, there are phenolic groups and aminomethyl groups on the aromatic ring of the polyamine, which is beneficial to enhance the oxidation resistance of the ultra-thin functional layer. The chemical structural formula of the ultra-thin functional layer aromatic polyamide can be expressed as:

In the formula, X is -NH-CO-NH- or (-OCO-NH-); Y corresponds to -NH ₂ or -OH, and may also be -COOH; Z is -CH ₂ NH ₂ .

The present invention relates to a new type of polyamide reverse osmosis composite membrane. On the porous support membrane, the aromatic ring contains phenolic groups and aliphatic polyamines and modified aromatic polyacyl chlorides are compounded in a polyamine solution for interfacial polycondensation. Thin layer of aromatic and aliphatic polyamide.

The above novel polyamide reverse osmosis composite membrane, the aromatic ring contains a phenolic group and aliphatic dibasic or tribasic amines, including at least 2,4,6-triaminomethylphenol, 2,6-diaminomethylphenol One of basephenol and 2,4-diaminomethylphenol and its corresponding derivatives.

In the above novel polyamide reverse osmosis composite membrane, the modified aromatic polyacyl chloride includes at least one of 5-oxoformyl chloride-isophthaloyl chloride and trimesoyl chloride.

In the above-mentioned novel polyamide reverse osmosis composite membrane, the aromatic ring contains phenol groups and the weight ratio of the aliphatic polyamine to the modified aromatic polyacyl chloride is from 0.1:1 to 10:1.

The above novel polyamide reverse osmosis composite membrane contains 0.1% to 1% dispersant CNF in the polyamine solution for interfacial polycondensation, and CNF is a sulfonated product of naphthalene, cresol and formaldehyde condensation products.

The above novel polyamide reverse osmosis composite membrane, the support membrane is dissolved in N,N-dimethylacetamide with 16% Udel P3500 polysulfone, 0.3% water and 0.1% surfactant, and coated with Obtained on polyester non-woven fabric, then immersed in water to gel and remove the solvent; wherein the surfactant includes at least alkylphenol polyoxyethyl ester phosphate, sodium dodecylsulfonate and alkylphenol polyoxyethylene One of the ester phosphates.

The preparation method of the new polyamide reverse osmosis composite membrane is to immerse the polysulfone support membrane in the above polyamine solution on one side, and carry out the interfacial polymerization reaction on one side with the modified polyacyl chloride solution to form the interfacial polymerization reaction of the polyamide active layer It is only carried out on the surface of the polysulfone supporting membrane, and the composite membrane is dried in the air for 1 to 3 minutes, then heat-treated, and then rinsed to obtain a reverse osmosis composite membrane.

In the preparation method of the above novel polyamide reverse osmosis composite membrane, the heat treatment includes two steps, the first step is to treat at 40-70°C for 3-5 minutes, and the second step is to treat at 70-110°C for 3-5 minutes. minute.

In the preparation method of the above-mentioned novel polyamide reverse osmosis composite membrane, the rinsing includes two steps, the first step is rinsing for 10-40 minutes in a pure aqueous solution with a methanol weight ratio of 15% at 30-60°C, and the second step Rinse in pure water at 30-60°C for 10-40 minutes.

In the preparation method of the above novel polyamide reverse osmosis composite membrane, the organic solvent used in the modified multi-acid chloride solution is one of trifluorotrichloroethane, n-hexane, heptane and undecane.

The performance of the composite membrane prepared by this method is obviously better than that of the composite membrane prepared by the conventional immersion interfacial polymerization method, and it is easier to wash out the excess polyamine during the rinsing process.

The following examples give a description of the novel reverse osmosis composite membranes and their desalination performance. However, these examples are provided only by way of illustration and not limitation of the present invention.

Detailed ways

Example 1-2 dissolves N,N-dimethylacetamide with 16% of Udel P3500 polysulfone, 0.3% of water and 0.1% of nonylphenol polyoxyethyl ester phosphate, and coats the polyester nonwoven cloth, and then immersed in water to remove the solvent to obtain a support membrane with a molecular weight cut-off of 20,000-30,000, which is stored in a wet state for future use.

One side of the wet polysulfone support membrane is immersed in an aqueous solution of 2% by weight of polyamine (2,4,6-triaminomethylphenol, 2,6-diaminomethylphenol and 2,4-diaminomethylphenol Aminomethyl phenol) for 2 minutes, and after being squeezed dry by rolling the surface of the support film with a rubber roller, contact with a cyclohexane solution with a weight ratio of 0.1% of polyacyl chlorides on one side to carry out interfacial polymerization reaction for 20-40 seconds. The composite film is dried in the air for 2 minutes, and then undergoes two-step heat treatment: the first step is to treat at 40-70°C for 3-5 minutes, and the second step is to treat at 70-110°C for 3-5 minutes. Then carry out two steps of rinsing again: the first step is to rinse in 30-60 DEG C of methanol weight ratio of 15% aqueous solution for 10-40 minutes, and the second step is to rinse in 30-60 DEG C water for 10-40 minutes. The prepared composite membrane was stored in water, and its desalination performance was tested under the conditions of 2000mg/L sodium chloride aqueous solution, operating pressure of 1.5MPa, and operating temperature of 22°C.

Example   Polyacyl chloride   Polyamine Flux (l/m2.h)   Salt rejection rate 12   Trimesoyl chloride 5-oxoformyl chloride-isophthaloyl chloride 2,4,6-Triaminomethylphenol 2.4,6-Triaminomethylphenol 31.824.0 98.198.8

Embodiment 3-4 is the same as the previous embodiment, according to the method described above, adopting a polyamine weight ratio of 2% aqueous solution (containing 0.2% dispersant CNF, this CNF is the sulfonated product of naphthalene, cresol and formaldehyde condensate ), trimesoyl chloride weight ratio is 0.1% cyclohexane solution to prepare reverse osmosis composite membrane. The prepared composite membrane was stored in water, and its desalination performance was tested under the conditions of 2000mg/L sodium chloride aqueous solution, operating pressure of 1.0MPa, and operating temperature of 22°C.

These several examples are to investigate the low-pressure performance of the membrane and the effect of the dispersant.

Example   Polyacyl chloride   Polyamine Flux (l/m2.h) Salt rejection rate 34   Trimesoyl chloride 5-oxoformyl chloride-isophthaloyl chloride 2,4,6-Triaminomethylphenol 2,4,6-Triaminomethylphenol 20.516.2 98.799.0

Example 5-6 is the same as the reverse osmosis composite membrane of previous examples 1-2, immersed in 20% glycerin aqueous solution for 5 hours, taken out and dried, and after six months in the air, re-immersed in water, at 2000mg/L The sodium chloride aqueous solution was tested for its desalination performance under the conditions of an operating pressure of 1.5 MPa and an operating temperature of 22°C.

These examples are to investigate the stability of performance of this type of film after long-term storage.

Example   Polyacyl chloride Polyamine Flux (l/m ² .h)   Salt rejection rate 56   Trimesoyl chloride 5-oxoformyl chloride-isophthaloyl chloride 2,4,6-Triaminomethylphenol 2,4,6-Triaminomethylphenol 28.625.3 98.298.7

Examples 7-8 are the same as the reverse osmosis composite membranes of the previous examples 1-2. In 2000 mg/L sodium chloride aqueous solution, the operating pressure is 1.5 MPa, and the operating temperature is 22 ° C. Test its desalination and flux performance.

These several examples are to investigate the stability of the long-term operation of this type of membrane performance. Example 7 is the initial performance, and Example 8 is the performance after 60 days of continuous operation.

Example   Polyacyl chloride polyamine Flux (l/m ² .h) Salt rejection rate 78   Trimesoyl chloride 5-oxoformyl chloride-isophthaloyl chloride 2,4,6-Triaminomethylphenol 2,4,6-Triaminomethylphenol 29.526.5 98.098.4

Example 9-10 is the same as the reverse osmosis composite membrane of previous examples 1-2. After the membrane is immersed in the aqueous solution of NaClO of pH=8,500mg/L for 48 hours, its desalination rate drops from 98.1%, 98.8% to 97.6% respectively. and 98.4. The test conditions are: 2000mg/L sodium chloride aqueous solution, the operating pressure is 1.5MPa, and the operating temperature is 22°C.

Claims (8)

1. A novel polyamide reverse osmosis composite membrane is characterized in that, on the porous support membrane, contains a phenolic group and aliphatic dibasic or tribasic amines on the aromatic ring, at least including 2,4,6-triaminomethyl One of 2,6-diaminomethylphenol, 2,4-diaminomethylphenol and their corresponding derivatives and at least one of 5-oxoformyl chloride-isophthaloyl chloride and trimesoyl chloride A mixed aromatic and aliphatic polyamide thin layer is compounded in a solution containing 0.1%---1% dispersant CNF for interfacial polycondensation. 2. novel polyamide reverse osmosis composite membrane as claimed in claim 1, is characterized in that, the weight ratio that contains phenol group and aliphatic polyamine and described modified aromatic polyacyl chloride is from 0.1: 1 to 10:1. 3. The novel polyamide reverse osmosis composite membrane as claimed in claim 1, wherein the dispersant CNF for interfacial polycondensation is a sulfonated product of naphthalene, cresol and formaldehyde condensate. 4. novel polyamide reverse osmosis composite membrane as claimed in claim 1, is characterized in that, described supporting membrane is soluble in N with 16% Udel P3500 polysulfone, 0.3% water and 0.1% surfactant , N-dimethylacetamide, coated on polyester non-woven fabric, then immersed in water to gel and remove the solvent; wherein the surfactant includes at least alkylphenol polyoxyethyl ester phosphate, dodecane One of sodium base sulfonate and alkylphenol polyoxyethyl ester phosphate. 5. A preparation method of a novel polyamide reverse osmosis composite membrane, characterized in that, one side of the polysulfone support membrane is immersed in the polyamine solution of the above-mentioned claim 1, and the single side interface polymerization reaction is carried out with the modified polyacyl chloride solution The interfacial polymerization reaction to form the polyamide active layer is only carried out on the surface of the polysulfone support membrane, and the composite membrane is dried in the air for 1 to 3 minutes, then heat-treated, and then rinsed to obtain a reverse osmosis composite membrane. 6. the preparation method of novel polyamide reverse osmosis composite membrane as claimed in claim 5 is characterized in that, described heat treatment comprises two steps, and the first step is to process at 40-70 ℃ for 3-5 minutes, the second The first step is to treat at 70-110°C for 3-5 minutes. 7. the preparation method of novel polyamide reverse osmosis composite membrane as claimed in claim 5 is characterized in that, described rinsing comprises two steps, and the first step is that the methanol weight ratio of 30-60 ℃ is 15% pure Rinse in aqueous solution for 10-40 minutes, and the second step is to rinse in pure water at 30-60°C for 10-40 minutes. 8. the preparation method of novel polyamide reverse osmosis composite membrane as claimed in claim 5 is characterized in that, the used organic solvent of modified polybasic acid chloride solution is trifluorotrichloroethane, normal hexane, heptane and undecane kind of.