A method for preparing a reverse osmosis composite membrane

Abstract

The application relates to a preparation method of a reverse osmosis composite membrane. The application modifies titanium nitride nanowires to prepare amino titanium nitride nanowires with hydrophilic functions; the amino titanium nitride nanowires are added into an aqueous solution, and are uniformly distributed in a polyamide functional layer of the reverse osmosis composite membrane through an interfacial polymerization reaction. The amino titanium nitride nanowires participate in the interfacial polymerization reaction, crosslink through trimesoyl chloride (TMC), serve as joint positions in the polyamide layer, and the mechanical strength and oxidation resistance of the reverse osmosis composite membrane are enhanced, and the service life is prolonged.

Description

Technical Field

[0001] This invention relates to the field of reverse osmosis membrane technology, and specifically to a method for preparing and applying a reverse osmosis membrane composite membrane. Background Technology

[0002] The core component of reverse osmosis separation technology is the reverse osmosis membrane, which is one of the most widely used and most effective separation membranes in the field of separation membranes.

[0003] The separation mechanism of reverse osmosis membranes mainly includes the dissolution-diffusion mechanism theory, the preferential adsorption-capillary flow theory, and the hydrogen bonding theory. Based on structural characteristics, they can be divided into asymmetric reverse osmosis membranes and composite reverse osmosis membranes. Due to their higher water flux and desalination rate, composite reverse osmosis membranes have superior overall performance compared to asymmetric reverse osmosis membranes, making them the main target of current membrane separation technology development. Currently, interfacial polymerization is the most common method for preparing composite reverse osmosis membranes. Using a porous polysulfone support layer as the base membrane, polyamines and polychlorides undergo interfacial polymerization on the base membrane to form a dense functional layer. Although reverse osmosis is widely used in boiler feedwater, industrial high-salinity wastewater treatment and reuse, pure and ultrapure water preparation, and material pre-concentration due to its advantages such as high separation efficiency, wide impurity removal range, large water production, and no secondary pollution, reverse osmosis membranes exhibit problems such as susceptibility to fouling and corrosion. Membrane fouling and oxidation significantly reduce the water flux and lifespan of reverse osmosis membranes, increasing the cost of continued use. Therefore, the development of fouling-resistant and oxidation-resistant reverse osmosis membranes is also a major direction of modern reverse osmosis membrane research.

[0004] Titanium nitride nanomaterials are considered a novel multifunctional material due to their stable chemical properties, large specific surface area, high surface activity, high strength, and good oxidation resistance. Therefore, in the development of reverse osmosis membranes, titanium nitride nanomaterials can be used to address issues such as unstable mechanical properties and easy oxidation of the separation membrane. Currently, however, the application of titanium nitride nanowires in the manufacture of reverse osmosis membranes has not yet been observed. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing a reverse osmosis composite membrane. This invention modifies titanium nitride nanowires to prepare hydrophilic amino-titanium nitride nanowires; these amino-titanium nitride nanowires are added to an aqueous solution and subjected to interfacial polymerization to achieve uniform distribution within the polyamide functional layer of the reverse osmosis composite membrane. The amino-titanium nitride nanowires participate in the interfacial polymerization reaction and, through crosslinking with trimesoamide (TMC), act as binding sites in the polyamide layer, thereby enhancing the mechanical strength and oxidation resistance of the reverse osmosis composite membrane and extending its service life.

[0006] A method for preparing a reverse osmosis membrane composite membrane includes the following steps:

[0007] (1) Pour titanium nitride nanowires, 2-amino-terephthalic acid, DMF and acetic acid into a beaker and mix them thoroughly by ultrasonic vibration. Then, put them into a polytetrafluoroethylene reactor and heat them to 100-160℃ for 24-36 hours. Separate the solid and liquid, wash the solid repeatedly with deionized water, and dry it to obtain amino titanium nitride nanowires.

[0008] The molar ratio of each raw material is as follows: titanium nitride nanowires: 2-amino-terephthalic acid: acetic acid: N,N-dimethylformamide is 1:3:50:(250-300).

[0009] (2) The polysulfone-based membrane (PSF) cleaned with polyvinyl alcohol (PVA) was immersed in an aqueous solution with pH=8 for 40s. After removing the excess solution with a rubber roller, it was immersed in an oil solution containing polyacrylamide chloride for 60s. After taking it out, it was dried at 80℃ for 10min to obtain a reverse osmosis composite membrane.

[0010] The aqueous solution comprises, by mass percentage: aminotitanium nitride nanowires (0-3 wt%), m-phenylenediamine (2.5 wt%), triethylamine (0.2 wt%), sodium dodecyl sulfonate (0.3 wt%), and 1,3-diamino-2-propanol (0.1-0.3 wt%).

[0011] The oil phase solution comprises, by mass percentage: a hexane solution of pyromellitic methyl chloride (0.2 wt%) and sodium 1,3-propanesulfonate (0.1 wt%).

[0012] The beneficial effects of this invention compared to the prior art are:

[0013] (1) This invention prepares amino-titanium nitride nanowires by modifying titanium nitride nanowires. This is the first time that nano-titanium nitride materials have been introduced into the preparation of reverse osmosis membranes, significantly improving the stability and oxidation resistance of the reverse osmosis membranes;

[0014] (2) In this invention, the reverse osmosis composite membrane prepared by interfacial polymerization reaction because the amino-titanium nitride nanowires carry hydrophilic amino functional groups has uniform pore spacing and good hydrophilicity.

[0015] (3) In this invention, the amino-titanium nitride nanowires act as binding sites in the polyamide layer and form a cross-linking effect with trimethylolpropionate (TMC), which enhances the mechanical strength and oxidation resistance of the functional layer, avoids the problem of easy oxidation and easy shedding of the polyamide layer, and improves the service life of the reverse osmosis composite membrane. Attached Figure Description

[0016] Figure 1 This is a SEM image of titanium nitride nanowires.

[0017] Figure 2This is the XRD crystal structure diagram of titanium nitride. Detailed Implementation

[0018] The following provides a specific embodiment of the preparation method of the reverse osmosis membrane composite membrane of the present invention.

[0019] Example 1

[0020] Titanium nitride nanowires, 2-amino-terephthalic acid, DMF, and acetic acid are poured into a beaker and thoroughly mixed by ultrasonic vibration. The mixture is then placed in a polytetrafluoroethylene reactor and heated to 100-160℃ for 24-36 hours. Solid-liquid separation is performed, and the solid is repeatedly washed with deionized water and dried to obtain amino-titanium nitride nanowires.

[0021] The molar ratio of each raw material is as follows: titanium nitride nanowires: 2-amino-terephthalic acid: acetic acid: N,N-dimethylformamide is 1:3:50:(250-300).

[0022] A polysulfone-based membrane (PSF) cleaned with PVA was immersed in an aqueous solution of aminotitanium nitride nanowires (1 wt%), m-phenylenediamine (2.5 wt%), triethylamine (0.2 wt%), sodium dodecyl sulfonate (0.3 wt%), and 1,3-diamino-2-propanol (0.1 wt%) at pH 8 for 40 s. After removing excess solution with a rubber roller, it was immersed in an oil solution of n-hexane containing trimesoyl chloride (0.2 wt%) and sodium 1,3-propanesulfonate (0.1 wt%) for 60 s. After removal, it was dried at 80 °C for 10 min to obtain a reverse osmosis composite membrane.

[0023] Example 2

[0024] Except for replacing the content of aminotitanium nitride nanowires with 2wt%, all other conditions were the same as in Example 1, and a reverse osmosis composite membrane was obtained.

[0025] Example 3

[0026] Except for replacing the content of aminotitanium nitride nanowires with 3wt%, all other conditions were the same as in Example 1, resulting in a chemical reverse osmosis composite membrane.

[0027] Example 4

[0028] Except for replacing the 1,3-diamino-2-propanol content with 0.2 wt%, all other conditions were the same as in Example 1, resulting in a reverse osmosis composite membrane.

[0029] Example 5

[0030] Except for replacing the 1,3-diamino-2-propanol content with 0.3 wt%, all other conditions were the same as in Example 1, resulting in a reverse osmosis composite membrane.

[0031] Comparative Example 1

[0032] A polysulfone-based membrane (PSF) cleaned with PVA was immersed in an aqueous solution of titanium nitride nanowires (1 wt%), m-phenylenediamine (2.5 wt%), triethylamine (0.2 wt%), sodium dodecyl sulfonate (0.3 wt%), and 1,3-diamino-2-propanol (0.1 wt%) at pH 8 for 40 s. After removing excess solution with a rubber roller, it was immersed in an oil solution of n-hexane containing trimesoyl chloride (0.2 wt%) and sodium 1,3-propanesulfonate (0.1 wt%) for 60 s. After removal, it was dried at 80 °C for 10 min to obtain a reverse osmosis composite membrane.

[0033] Comparative Example 2

[0034] A polysulfone-based membrane (PSF) cleaned with PVA was immersed in an aqueous solution of m-phenylenediamine (2.5 wt%), triethylamine (0.2 wt%), sodium dodecyl sulfonate (0.3 wt%), and 1,3-diamino-2-propanol (0.1 wt%) at pH 8 for 40 s. After removing excess solution with a rubber roller, it was immersed in an oil solution of n-hexane containing trimesoyl chloride (0.2 wt%) and sodium 1,3-propanesulfonate (0.1 wt%) for 60 s. After removal, it was dried at 80 °C for 10 min to obtain a reverse osmosis composite membrane.

[0035] Membrane performance was tested in Examples 1-5 and Comparative Examples 1-2, specifically according to the reverse osmosis membrane test method (GB / T32373-2015). The basic reverse osmosis membrane test conditions of this invention were: temperature 25℃, operating pressure 1.55MPa, and NaCl aqueous solution concentration 2000ppm, testing the membrane desalination rate, water flux, and mechanical strength. The membrane antioxidant performance test conditions of this invention were: 1000ppm H2O2 solution, adjusted to neutral pH with hydrochloric acid or sodium hydroxide solution, soaked for 12h, then rinsed with pure water, and soaked in pure water for 36h. The remaining test conditions for the reverse osmosis membrane water flux, desalination rate, and mechanical properties were the same as the basic reverse osmosis membrane test conditions.

[0036] Table 1. Changes in flux, desalination rate, and mechanical properties of the reverse osmosis membranes in the examples and comparative examples before and after the oxidation resistance test.

[0037]

[0038]

[0039] As can be seen from the experimental results in Table 1 above, the reverse osmosis composite membrane prepared by the method of the present invention has excellent water flux, desalination rate and oxidation resistance. This is because the amino-titanium nitride nanowires form a crosslinking effect with trimesoamide (TMC) at the charging binding sites of the amide layer, resulting in good oxidation resistance, high water flux and good desalination performance of the desalination layer.

[0040] The above description is only a preferred embodiment of the present invention and should be noted that it is not intended to limit the present invention. Any modifications and refinements made within the concept and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A method for preparing a reverse osmosis composite membrane, characterized in that: The method includes the following steps: (1) Titanium nitride nanowires, 2-amino-terephthalic acid, acetic acid and N,N-dimethylformamide were ultrasonically mixed and placed in a polytetrafluoroethylene reactor. The reaction temperature was 100-160℃ and the time was 24-36h to obtain amino-titanium nitride nanowires. The molar ratio of raw material composition is as follows: titanium nitride nanowires: 2-amino-terephthalic acid: acetic acid: N,N-dimethylformamide is 1:3:50:250~300. (2) Immerse the polysulfone-based film PSF in an aqueous solution for 40 seconds and remove excess solution with a rubber roller; Immerse it in an oil phase solution containing polyacrylamide chloride for 60 seconds, then remove it and dry it at 80°C for 10 minutes to obtain a high-strength oxidation-resistant reverse osmosis membrane. The aqueous solution comprises: 0-3 wt% titanium nitride aminonitride nanowires, 2.5 wt% m-phenylenediamine, 0.2 wt% triethylamine, 0.3 wt% sodium dodecyl sulfonate, and 0.1-0.3 wt% 1,3-diamino-2-propanol; The oil phase solution consists of a hexane solution containing 0.2 wt% pyromellitic acid chloride and 0.1 wt% sodium 1,3-propanesulfonate.

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