CN115554849A - A preparation method of polyethyleneimine-based positively charged nanofiltration membrane - Google Patents

Abstract

The invention discloses a preparation method of a polyethyleneimine-based positively charged nanofiltration membrane, comprising: (1) mixing branched polyethyleneimine with distilled water to prepare an aqueous phase solution, the concentration of the aqueous phase solution being 1 ~1.5wv%; (2) mixing trimesoyl chloride and an organic solvent to prepare an organic phase solution, the concentration of the organic phase solution is 0.05 ~ 0.1wv%; (3) immersing the nanofiltration base membrane into the aqueous phase solution and then take it out and dry it and then immerse it in the organic phase solution. After the reaction is over, take it out and dry it, and then wash it with an organic solvent; (4) dry and solidify the product after washing with an organic solvent to obtain polyethyleneimine-based positively charged nanofiltration membrane. The preparation method adopts the interfacial polymerization method on the nanofiltration base membrane, and the branched polyethyleneimine in the aqueous phase reacts with the trimesoyl chloride in the organic phase. By optimizing multiple reaction conditions in the interfacial polymerization process, the poly Ethyleneimine based high flux positively charged nanofiltration membrane.

Description

A preparation method of polyethyleneimine-based positively charged nanofiltration membrane

technical field

The invention relates to the technical field of separation membrane preparation, in particular to a preparation method of a polyethyleneimine-based positively charged nanofiltration membrane.

Background technique

Nanofiltration membrane technology is a new type of membrane separation technology between ultrafiltration and reverse osmosis. The molecular weight of the intercepted substance is usually 200-2000Da, and the membrane pore size is 0.5-2nm. It is generally believed that the mechanism of nanofiltration membrane interception includes Donnan effect and pore size sieving effect. The rejection rate for monovalent salts is not high, but it has higher rejection for multivalent ions and organic molecules. Nanofiltration is widely used in sewage treatment, pharmacy, chemical industry, drinking water preparation and other fields due to its advantages of no phase change, low operating pressure compared with reverse osmosis, and low operating cost. According to the surface charge of the membrane, nanofiltration membranes can be divided into positively charged, neutrally charged and negatively charged nanofiltration membranes.

At present, most nanofiltration membranes are mainly prepared by interfacial polymerization of trimesoyl chloride monomer in the organic phase and piperazine monomer in the aqueous phase, and the surface of the obtained membrane material is negatively charged. Negatively charged nanofiltration membranes have a high rejection rate for specific negatively charged pollutants, but when intercepting positively charged substances, the surface of negatively charged nanofiltration membranes is easily polluted due to the Donnan effect. The positively charged nanofiltration membrane can better reduce the pollution on the surface of the nanofiltration membrane caused by the Donnan effect, and has a broader application prospect in the separation of magnesium and lithium in salt lake water and the interception of positively charged dyes.

In recent years, positively charged nanofiltration membranes have been prepared by using positively charged amine groups (primary, secondary or tertiary amines) by introducing positively charged amine-based compounds into the preparation process of polyamide nanofiltration membranes. The interception performance of the filter membrane to magnesium ions has become a research hotspot. CN 114797492 A discloses a hyperbranched polyethyleneimine composite nanofiltration membrane and its preparation method, through a series of reactions to obtain a positively charged hyperbranched hydrophilic structure modified polyethyleneimine, and polyamideimide Interfacial polymerization occurs to form a composite nanofiltration membrane with good comprehensive performance. Compared with branched polyethyleneimine, hyperbranched polyethyleneimine has a higher degree of branching, but the membrane-making method is cumbersome, and the rejection rate and water flux of the prepared nanofiltration membrane for divalent salts still need to be improved. CN 111330447 B discloses a positively charged composite nanofiltration membrane, the positively charged nanofiltration selection layer is provided with positively charged groups by quaternized polyethyleneimine, and the obtained nanofiltration membrane has excellent magnesium chloride and sodium chloride interception Rate. However, the quaternization of polyethyleneimine leads to the reduction of the primary and secondary amine groups of the raw materials, which enhances the steric hindrance effect and reduces the water flux of the nanofiltration membrane.

Therefore, there is an urgent need to develop a nanofiltration membrane with good divalent salt rejection and water flux.

Contents of the invention

The purpose of the present invention is to provide a preparation method of polyethyleneimine-based positively charged nanofiltration membrane, the preparation method adopts interfacial polymerization method on the nanofiltration base membrane, branched polyethyleneimine in the aqueous phase and organic phase The trimesoyl chloride was reacted, and a polyethyleneimine-based high-flux positively charged nanofiltration membrane was prepared by optimizing multiple reaction conditions in the interfacial polymerization process.

To achieve the above object, the invention provides a preparation method of polyethyleneimine-based positively charged nanofiltration membrane, comprising the following steps:

(1) mixing branched polyethyleneimine with distilled water to prepare an aqueous phase solution, the concentration of the aqueous phase solution being 1 to 1.5wv%;

(2) mixing trimesoyl chloride and an organic solvent to prepare an organic phase solution, the concentration of the organic phase solution being 0.05-0.1wv%;

(3) Immerse the nanofiltration base membrane in the aqueous phase solution, then take it out and dry it and then immerse it in the organic phase solution, take it out and dry it after the reaction, and then wash it with an organic solvent;

(4) drying and solidifying the product washed with an organic solvent to obtain a polyethyleneimine-based positively charged nanofiltration membrane.

In the present invention, the organic solvent is a commonly used organic solvent in the field and is not particularly limited, as long as it can make the concentration of the organic phase dissolved in trimesoyl chloride reach 0.05-0.1wv%, preferably n-hexane.

According to the preparation method of polyethyleneimine-based positively charged nanofiltration membrane of the present invention, the nanofiltration base membrane is made of polyethersulfone. The polyethersulfone-based membrane has good hydrophilicity, can fully absorb the aqueous phase solution, reacts more fully in the subsequent interfacial polymerization process, and has a good film-forming effect. The performance of the nanofiltration membrane formed on this basis is even better.

According to the preparation method of the polyethyleneimine-based positively charged nanofiltration membrane of the present invention, the membrane molecular weight cut-off of the nanofiltration base membrane is greater than 50KDa and less than 150KDa.

The preparation method of the polyethyleneimine-based positively charged nanofiltration membrane of the present invention further includes a pretreatment step before immersing the nanofiltration base membrane in the aqueous phase solution: immersing the nanofiltration base membrane in deionized water for 72 to 99 hours, every Replace the deionized water every 24 to 33 hours.

According to the preparation method of the polyethyleneimine-based positively charged nanofiltration membrane of the present invention, the immersion time of the nanofiltration base membrane in the aqueous phase solution is 5 to 10 minutes.

According to the preparation method of the polyethyleneimine-based positively charged nanofiltration membrane of the present invention, the immersion time of the nanofiltration base membrane in the organic phase solution is 20-180s.

In the preparation method of the polyethyleneimine-based positively charged nanofiltration membrane of the present invention, the curing time is 2 to 3 minutes.

In the preparation method of the polyethyleneimine-based positively charged nanofiltration membrane of the present invention, the drying is rubber roller drying.

The beneficial effects of the present invention are:

Branched polyethyleneimine (bPEI) is a repeating unit polymer composed of ethylenediamine groups, with a branched molecular chain structure (that is, multiple amine groups protruding from multiple positions in the straight chain), The present invention uses branched polyethyleneimine as the water phase solute, because it is a cationic polyelectrolyte rich in primary amine, secondary amine and tertiary amine functional groups, has a high positive charge density and a branched structure, and has good hydrophilicity , which is more conducive to the passage of water molecules through the nanofiltration membrane, so it is beneficial to improve the selectivity of the nanofiltration membrane for positively charged solutes in the solution, and increase the water flux of the prepared nanofiltration membrane. At the same time, the present invention also strictly controls the concentration of the aqueous phase solution and the concentration of the organic phase solution, thereby controlling the reaction process of the interfacial polymerization reaction and selecting a more suitable organic phase solute trimesoyl chloride, so that the polyamide with excellent performance can be formed through the interfacial polymerization reaction. layer, a nanofiltration membrane with good divalent salt rejection and water flux is obtained.

detailed description

The present invention is specifically described below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention, and cannot be interpreted as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and improvements to the present invention according to the above-mentioned content of the present invention. Adjustment.

Branched polyethyleneimine in the following examples was purchased from Shanghai Macklin Biochemical Technology Co., Ltd.

Example 1

A polyethylenimine-based high-flux positively charged nanofiltration membrane and a preparation method thereof, the following steps with no temperature indicated are all carried out at room temperature.

(1) Soak polyethersulfone (PES) (membrane molecular weight cut-off 100KDa) with a size of 7cm×7cm in deionized water for pretreatment. The soaking time is 72h, and the deionized water needs to be replaced every 24h.

(2) Mix 3 g of branched polyethyleneimine with a relative molecular mass of 800 with 200 ml of distilled water to prepare an aqueous phase solution with a mass volume of 1.5 g/ml.

(3) Mix 0.1 g of trimesoyl chloride and 200 ml of n-hexane solvent to prepare an organic phase solution with a mass volume of 0.05 g/ml.

(4) Take a certain amount of n-hexane as a cleaning solution.

(5) Put the pretreated nanofiltration basement membrane into the aqueous phase solution, take it out after completely immersing it for 5 minutes, and dry the residual water on the surface of the membrane with a rubber roller, then put it into the organic phase solution for interfacial polymerization reaction.

(6) Take it out after 40s, dry it again and put it into the cleaning solution.

(7) Take it out and dry it, put it into a constant temperature drying oven to cure, and obtain a polyethyleneimine-based high-flux nanofiltration membrane after curing for 3 minutes.

(8) Take out the polyethyleneimine-based high-throughput positively charged nanofiltration membrane after drying, and seal it in a water environment for subsequent measurement. Under the pressure of 0.4Mpa, the performance of the prepared polyethyleneimine-based high-flux positively charged nanofiltration membrane was tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of the nanofiltration membrane is 18.1Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 96.4%.

Example 2

A polyethylenimine-based high-flux positively charged nanofiltration membrane and a preparation method thereof, the following steps with no temperature indicated are all carried out at room temperature.

(1) Soak polyethersulfone (PES) (membrane molecular weight cut-off 100KDa) with a size of 7cm×7cm in deionized water for pretreatment. The soaking time is 72h, and the deionized water needs to be replaced every 24h.

(2) Mix 2 g of branched polyethyleneimine with a relative molecular mass of 800 with 200 ml of distilled water to prepare an aqueous phase solution with a mass volume of 1.0 g/ml.

(3) Mix 0.2 g of trimesoyl chloride and 200 ml of n-hexane solvent to prepare an organic phase solution with a mass volume of 0.1 g/ml.

(4) Take a certain amount of n-hexane as a cleaning solution.

(5) Put the pretreated nanofiltration base membrane into the aqueous phase solution, take it out after completely immersing it for 5 minutes, dry the residual water on the surface of the membrane with a rubber roller, and then put it into the organic phase solution for interfacial polymerization reaction.

(6) Take it out after 60s, dry it again and put it into the cleaning solution.

(7) Take it out and dry it, put it into a constant temperature drying oven to cure, and obtain a polyethyleneimine-based high-flux nanofiltration membrane after curing for 3 minutes.

(8) Take out the polyethyleneimine-based high-throughput positively charged nanofiltration membrane after drying, and seal it in a water environment for subsequent measurement. Under the pressure of 0.4Mpa, the performance of the prepared polyethyleneimine-based high-flux positively charged nanofiltration membrane was tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of polyethyleneimine-based high-flux positively charged nanofiltration membrane is 13.0Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 96.1%.

Example 3

A polyethylenimine-based high-flux positively charged nanofiltration membrane and a preparation method thereof, the following steps with no temperature indicated are all carried out at room temperature.

(1) Soak polyethersulfone (PES) (membrane molecular weight cut-off 100KDa) with a size of 7cm×7cm in deionized water for pretreatment. The soaking time is 72h, and the deionized water needs to be replaced every 24h.

(2) Mix 3 g of branched polyethyleneimine with a relative molecular mass of 800 with 200 ml of distilled water to prepare an aqueous phase solution with a mass volume of 1.5 g/ml.

(3) Mix 0.1 g of trimesoyl chloride and 200 ml of n-hexane solvent to prepare an organic phase solution with a mass volume of 0.05 g/ml.

(4) Take a certain amount of n-hexane as a cleaning solution.

(5) Put the pretreated nanofiltration basement membrane into the aqueous phase solution, take it out after completely immersing it for 5 minutes, and dry the residual water on the surface of the membrane with a rubber roller, then put it into the organic phase solution for interfacial polymerization reaction.

(6) Take it out after 60s, dry it again and put it into the cleaning solution.

(7) Take it out and dry it, put it into a constant temperature drying oven to cure, and obtain a polyethyleneimine-based high-flux nanofiltration membrane after curing for 3 minutes.

(8) Take out the polyethyleneimine-based high-throughput positively charged nanofiltration membrane after drying, and seal it in a water environment for subsequent measurement. Under the pressure of 0.4Mpa, the performance of the prepared polyethyleneimine-based high-flux nanofiltration membrane was tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of polyethyleneimine-based high-flux positively charged nanofiltration membrane is 19.9Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 96.2%.

Example 4

A polyethylenimine-based high-flux positively charged nanofiltration membrane and a preparation method thereof, the following steps with no temperature indicated are all carried out at room temperature.

(1) Soak polyethersulfone (PES) (membrane molecular weight cut-off 100KDa) with a size of 7cm×7cm in deionized water for pretreatment. The soaking time is 72h, and the deionized water needs to be replaced every 24h.

(2) Mix 3 g of branched polyethyleneimine with a relative molecular mass of 800 with 200 ml of distilled water to prepare an aqueous phase solution with a mass volume of 1.5 g/ml.

(3) Mix 0.1 g of trimesoyl chloride and 200 ml of n-hexane solvent to prepare an organic phase solution with a mass volume of 0.05 g/ml.

(4) Take a certain amount of n-hexane as a cleaning solution.

(5) Put the pretreated nanofiltration basement membrane into the aqueous phase solution, take it out after completely immersing it for 5 minutes, and dry the residual water on the surface of the membrane with a rubber roller, then put it into the organic phase solution for interfacial polymerization reaction.

(6) Take it out after 40s, dry it again and put it into the cleaning solution.

(7) Take it out and dry it and put it into a constant temperature drying oven to solidify, and obtain a nanofiltration membrane with high selectivity after solidifying for 2 minutes.

(8) Take out the polyethyleneimine-based high-throughput positively charged nanofiltration membrane after drying, and seal it in a water environment for subsequent measurement. Under the pressure of 0.4Mpa, the performance of the prepared polyethyleneimine-based high-flux positively charged nanofiltration membrane was tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of polyethyleneimine-based high-flux positively charged nanofiltration membrane is 17.2Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 97.5%.

Example 5

A polyethylenimine-based high-flux positively charged nanofiltration membrane and a preparation method thereof, the following steps with no temperature indicated are all carried out at room temperature.

(1) Soak polyethersulfone (PES) (membrane molecular weight cut-off 100KDa) with a size of 7cm×7cm in deionized water for pretreatment. The soaking time is 72h, and the deionized water needs to be replaced every 24h.

(2) Mix 3 g of branched polyethyleneimine with a relative molecular mass of 800 with 200 ml of distilled water to prepare an aqueous phase solution with a mass volume of 1.5 g/ml.

(3) Mix 0.1 g of trimesoyl chloride and 200 ml of n-hexane solvent to prepare an organic phase solution with a mass volume of 0.05 g/ml.

(4) Take a certain amount of n-hexane as a cleaning solution.

(5) Put the pretreated nanofiltration basement membrane into the aqueous phase solution, take it out after completely immersing it for 5 minutes, and dry the residual water on the surface of the membrane with a rubber roller, then put it into the organic phase solution for interfacial polymerization reaction.

(6) Take it out after 120s, dry it again and put it into the cleaning solution.

(7) Take it out and dry it, put it into a constant temperature drying oven to cure, and obtain a polyethyleneimine-based high-flux nanofiltration membrane after curing for 3 minutes.

(8) Take out the polyethyleneimine-based high-throughput positively charged nanofiltration membrane after drying, and seal it in a water environment for subsequent measurement. Under the pressure of 0.4Mpa, the performance of the prepared polyethyleneimine-based high-flux positively charged nanofiltration membrane was tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of polyethyleneimine-based high-flux positively charged nanofiltration membrane is 13.2Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 98.3%.

Example 6

A polyethylenimine-based high-flux positively charged nanofiltration membrane and a preparation method thereof, the following steps with no temperature indicated are all carried out at room temperature.

(1) Soak polysulfone (PSF) (membrane molecular weight cut-off 100KDa) with a size of 7cm×7cm in deionized water for pretreatment. The soaking time is 72h, and the deionized water needs to be replaced every 24h.

(2) Mix 3 g of branched polyethyleneimine with a relative molecular mass of 800 with 200 ml of distilled water to prepare an aqueous phase solution with a mass volume of 1.5 g/ml.

(3) Mix 0.1 g of trimesoyl chloride and 200 ml of n-hexane solvent to prepare an organic phase solution with a mass volume of 0.05 g/ml.

(4) Take a certain amount of n-hexane as a cleaning solution.

(5) Put the pretreated nanofiltration basement membrane into the aqueous phase solution, take it out after completely immersing it for 5 minutes, and dry the residual water on the surface of the membrane with a rubber roller, then put it into the organic phase solution for interfacial polymerization reaction.

(6) Take it out after 120s, dry it again and put it into the cleaning solution.

(7) Take it out and dry it, put it into a constant temperature drying oven to cure, and obtain a polyethyleneimine-based high-flux nanofiltration membrane after curing for 3 minutes.

(8) Take out the polyethyleneimine-based high-throughput positively charged nanofiltration membrane after drying, and seal it in a water environment for subsequent measurement. Under the pressure of 0.4Mpa, the performance of the prepared polyethyleneimine-based high-flux positively charged nanofiltration membrane was tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of polyethyleneimine-based high-flux positively charged nanofiltration membrane is 13.0Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 95%.

Comparative example 1

A polyethylenimine-based high-flux positively charged nanofiltration membrane and a preparation method thereof, the following steps with no temperature indicated are all carried out at room temperature.

(1) Soak polyethersulfone (PES) (membrane molecular weight cut-off 100KDa) with a size of 7cm×7cm in deionized water for pretreatment. The soaking time is 72h, and the deionized water needs to be replaced every 24h.

(2) Mix 4 g of branched polyethyleneimine with a relative molecular mass of 800 with 200 ml of distilled water to prepare an aqueous phase solution with a mass volume of 2 g/ml.

(3) Mix 0.6 g of trimesoyl chloride and 200 ml of n-hexane solvent to prepare an organic phase solution with a mass volume of 0.3 g/ml.

(4) Take a certain amount of n-hexane as a cleaning solution.

(5) Put the pretreated nanofiltration basement membrane into the aqueous phase solution, take it out after completely immersing it for 5 minutes, and dry the residual water on the surface of the membrane with a rubber roller, then put it into the organic phase solution for interfacial polymerization reaction.

(6) Take it out after 60s, dry it again and put it into the cleaning solution.

(7) Take it out and dry it, put it into a constant temperature drying oven to cure, and obtain a polyethyleneimine-based high-flux nanofiltration membrane after curing for 3 minutes.

(8) Take out the polyethyleneimine-based high-throughput positively charged nanofiltration membrane after drying, and seal it in a water environment for subsequent measurement. Under the pressure of 0.4Mpa, the performance of the prepared polyethyleneimine-based high-flux positively charged nanofiltration membrane was tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of polyethyleneimine-based high-flux positively charged nanofiltration membrane is 5.6Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 97.0%.

Comparative example 2

A polyethylenimine-based high-flux positively charged nanofiltration membrane and a preparation method thereof, the following steps with no temperature indicated are all carried out at room temperature.

(1) Soak polyethersulfone (PES) (membrane molecular weight cut-off 100KDa) with a size of 7cm×7cm in deionized water for pretreatment. The soaking time is 72h, and the deionized water needs to be replaced every 24h.

(2) Mix 1 g of branched polyethyleneimine with a relative molecular mass of 800 with 200 ml of distilled water to prepare an aqueous phase solution with a mass volume of 0.5 g/ml.

(3) Mix 0.8 g of trimesoyl chloride and 200 ml of n-hexane solvent to prepare an organic phase solution with a mass volume of 0.4 g/ml.

(4) Take a certain amount of n-hexane as a cleaning solution.

(5) Put the pretreated nanofiltration basement membrane into the aqueous phase solution, take it out after completely immersing it for 5 minutes, and dry the residual water on the surface of the membrane with a rubber roller, then put it into the organic phase solution for interfacial polymerization reaction.

(6) Take it out after 60s, dry it again and put it into the cleaning solution.

(7) Take it out and dry it and put it into a constant temperature drying oven for curing. After curing for 3 minutes, a polyethyleneimine-based high-flux positively charged nanofiltration membrane is obtained.

(8) Take out the polyethyleneimine-based high-throughput positively charged nanofiltration membrane after drying, and seal it in a water environment for subsequent measurement. Under the pressure of 0.4Mpa, the performance of the prepared polyethyleneimine-based high-flux positively charged nanofiltration membrane was tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of polyethyleneimine-based high-flux positively charged nanofiltration membrane is 6.6Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 96.7%.

Comparative example 3

A polyethylenimine-based high-flux positively charged nanofiltration membrane and a preparation method thereof, the following steps with no temperature indicated are all carried out at room temperature.

(1) Soak polyethersulfone (PES) (membrane molecular weight cut-off 100KDa) with a size of 7cm×7cm in deionized water for pretreatment. The soaking time is 72h, and the deionized water needs to be replaced every 24h.

(2) Mix 5 g of branched polyethyleneimine with a relative molecular mass of 800 with 200 ml of distilled water to prepare an aqueous phase solution with a mass volume of 2.5 g/ml.

(3) Mix 0.8 g of trimesoyl chloride and 200 ml of n-hexane solvent to prepare an organic phase solution with a mass volume of 0.4 g/ml.

(4) Take a certain amount of n-hexane as a cleaning solution.

(5) Put the pretreated nanofiltration basement membrane into the aqueous phase solution, take it out after completely immersing it for 5 minutes, and dry the residual water on the surface of the membrane with a rubber roller, then put it into the organic phase solution for interfacial polymerization reaction.

(6) Take it out after 60s, dry it again and put it into the cleaning solution.

(7) Take it out and dry it and put it into a constant temperature drying oven for curing. After curing for 3 minutes, a polyethyleneimine-based high-flux positively charged nanofiltration membrane is obtained.

(8) Take out the polyethyleneimine-based high-throughput positively charged nanofiltration membrane after drying, and seal it in a water environment for subsequent measurement. Under the pressure of 0.4Mpa, the performance of the prepared polyethyleneimine-based high-flux positively charged nanofiltration membrane was tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of polyethyleneimine-based high-flux positively charged nanofiltration membrane is 3.1Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 98.4%.

Comparative example 4

Nanofiltration membranes were prepared according to Example 15 of patent CN114797492A.

Under the pressure of 0.4Mpa, the properties of the prepared nanofiltration membrane were tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of the nanofiltration membrane is 5.62Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 97.0%.

Comparative example 5

The preparation method is the same as in Example 1, except that trimesoyl chloride is replaced by phthaloyl chloride.

Under the pressure of 0.4Mpa, the performance of the prepared nanofiltration membrane was tested with pure water and 2000ppm MgCl ₂ respectively. The test results show that the pure water permeability of the nanofiltration membrane is 10.3Lm ^-2 h ^-1 bar ^-1 , and the rejection rate of MgCl ₂ aqueous solution is 95.0%.

Certainly, the present invention also can have other various embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes All changes and modifications should belong to the protection scope of the claims of the present invention.

Claims (8)

1. A preparation method of a polyethyleneimine-based positively-charged nanofiltration membrane is characterized by comprising the following steps:

(1) Mixing branched polyethyleneimine with distilled water to prepare an aqueous phase solution, wherein the concentration of the aqueous phase solution is 1-1.5 wv%;

(2) Mixing trimesoyl chloride and an organic solvent to prepare an organic phase solution, wherein the concentration of the organic phase solution is 0.05-0.1 wv%;

(3) Soaking a nanofiltration base membrane into the water phase solution, taking out and drying the nanofiltration base membrane, then soaking the nanofiltration base membrane into the organic phase solution, taking out and drying the nanofiltration base membrane after the reaction is finished, and then washing the nanofiltration base membrane by using an organic solvent;

(4) And (3) drying and curing the product washed by the organic solvent to obtain the polyethyleneimine positively charged nanofiltration membrane.

2. The method of claim 1, wherein the nanofiltration membrane is made of polyethersulfone.

3. The method of claim 2, wherein the nanofiltration membrane has a membrane cut-off molecular weight of greater than 50kDa and less than 150kDa.

4. The method of claim 1, wherein the pre-treatment step of immersing the nanofiltration membrane in the aqueous solution comprises: and (3) soaking the nanofiltration base membrane into deionized water for 72-99 h, and replacing the deionized water every 24-33 h.

5. The method for preparing a polyethyleneimine-based positively-charged nanofiltration membrane according to claim 1, wherein the nanofiltration base membrane is immersed in an aqueous solution for 5-10 min.

6. The method of claim 1, wherein the soaking time of the nanofiltration membrane in the organic phase solution is 20-180s.

7. The method for preparing a polyethyleneimine-based positively-charged nanofiltration membrane according to claim 1, wherein the curing time is 2-3 min.

8. The method of claim 1, wherein the drying is rubber roller drying.