Application of phytic acid-graphene oxide quantum dot composite as an aqueous monomer in the preparation of polyamide nanofiltration membranes

Abstract

The present invention discloses the application of a phytic acid-graphene oxide quantum dot composite as an aqueous monomer in the preparation of a polyamide nanofiltration membrane. The preparation method of the phytic acid-graphene oxide quantum dot composite includes: preparing an aqueous solution of graphene oxide by a modified Hummers method, then subjecting it to ultrasonic treatment at 450-550 W and performing a heating reaction to obtain a graphene oxide quantum dot solution, and further preparing the phytic acid-graphene oxide quantum dot composite by a solution synthesis method using the graphene oxide quantum dot solution and phytic acid as raw materials. By adding the phytic acid-graphene oxide quantum dot composite to the aqueous monomer, the present invention prepares a phytic acid-graphene oxide quantum dot composite-doped polyamide nanofiltration membrane through interfacial polymerization. Under the test conditions of room temperature and 0.6 MPa, it has a high rejection rate (above 97%) for a 0.2 wt% magnesium sulfate solution, and the pure water flux is 70-80 LHM.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanofiltration membranes, and particularly relates to the application of a phytic acid-graphene oxide quantum dot composite as an aqueous monomer in the preparation of a polyamide nanofiltration membrane. Background Art

[0002] A nanofiltration membrane is a new type of pressure-driven membrane with a pore size between ultrafiltration and reverse osmosis, and can be used for the separation of divalent salts and monovalent salts. Nanofiltration membranes have the characteristics of low operating pressure, high flux, and energy saving. Therefore, nanofiltration membranes are widely used in the fields of bioengineering, medicine, metallurgy, water treatment, electronics, etc. The commonly used industrial nanofiltration membranes are organic nanofiltration membranes, which have many advantages such as high gas permeability, low density, good film-forming property, low cost, and good flexibility. However, organic nanofiltration membranes have disadvantages such as low flux and poor anti-pollution ability in industrial applications. Therefore, it is necessary to modify the organic nanofiltration membranes to improve the flux and anti-pollution property of the membrane layer. In addition, the relatively thick polyamide organic nanofiltration membrane layer greatly increases the liquid transport resistance. Therefore, reducing the thickness of the polyamide organic nanofiltration membrane layer has become a key challenge for further improvement. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide the application of a phytic acid-graphene oxide quantum dot composite as an aqueous monomer in the preparation of a polyamide nanofiltration membrane.

[0004] Another purpose of the present invention is to provide a polyamide nanofiltration membrane.

[0005] The technical solution of the present invention is as follows:

[0006] The application of a phytic acid-graphene oxide quantum dot composite as an aqueous monomer in the preparation of a polyamide nanofiltration membrane, and the preparation method of the phytic acid-graphene oxide quantum dot composite includes: preparing an aqueous solution of graphene oxide by a modified Hummers method, then subjecting it to ultrasonic treatment at 450 - 550W and then carrying out a heating reaction to obtain a graphene oxide quantum dot solution, and then preparing a phytic acid-graphene oxide quantum dot composite by a solution synthesis method using the graphene oxide quantum dot solution and phytic acid as raw materials.

[0007] In a preferred embodiment of the present invention, the preparation method of the phytic acid-graphene oxide quantum dot composite includes:

[0008] (1) Preparing an aqueous solution of graphene oxide by a modified Hummers method, then subjecting it to ultrasonic treatment at 450 - 550W for 25 - 35 min, then reacting at 75 - 85°C for 7 - 9 h, and then carrying out centrifugal washing to obtain a graphene oxide quantum dot solution;

[0009] (2) After uniformly mixing phytic acid and the above-mentioned graphene oxide quantum dot solution, carry out a heating reflux reaction at 60 - 90 °C for 0.8 - 1.2 h to obtain the solution of the phytic acid-graphene oxide quantum dot composite.

[0010] In a preferred embodiment of the present invention, the mass ratio of phytic acid to graphene oxide quantum dots in the phytic acid-graphene oxide quantum dot composite is 1 - 20:1.

[0011] More preferably, the mass ratio of phytic acid to graphene oxide quantum dots in the phytic acid-graphene oxide quantum dot composite is 5 - 10:1.

[0012] A polyamide nanofiltration membrane includes a polyethersulfone ultrafiltration support layer and an organic nanofiltration membrane layer formed on the polyethersulfone ultrafiltration support layer by interfacial polymerization. In this interfacial polymerization, the aqueous monomer consists of a phytic acid-graphene oxide quantum dot composite and piperazine, the acid acceptor is a polyamine, and the organic monomer is benzene-1,3,5-tricarbonyl chloride. The preparation method of the phytic acid-graphene oxide quantum dot composite includes: preparing an aqueous solution of graphene oxide by a modified Hummers method, then subjecting it to ultrasonic treatment at 450 - 550 W and carrying out a heating reaction to obtain a graphene oxide quantum dot solution, and then using the graphene oxide quantum dot solution and phytic acid as raw materials to prepare the phytic acid-graphene oxide quantum dot composite by a solution synthesis method.

[0013] In a preferred embodiment of the present invention, the preparation method of the phytic acid-graphene oxide quantum dot composite includes:

[0014] (1) Prepare an aqueous solution of graphene oxide by a modified Hummers method, then carry out ultrasonic treatment at 450 - 550 w for 25 - 35 min, then carry out a reaction at 75 - 85 °C for 7 - 9 h, and then carry out centrifugal cleaning to obtain a graphene oxide quantum dot solution;

[0015] (2) After uniformly mixing phytic acid and the above-mentioned graphene oxide quantum dot solution, carry out a heating reflux reaction at 60 - 90 °C for 0.8 - 1.2 h to obtain the solution of the phytic acid-graphene oxide quantum dot composite.

[0016] In a preferred embodiment of the present invention, the mass ratio of phytic acid to graphene oxide quantum dots in the phytic acid-graphene oxide quantum dot composite is 1 - 20:1.

[0017] More preferably, the mass ratio of phytic acid to graphene oxide quantum dots in the phytic acid-graphene oxide quantum dot composite is 5 - 10:1.

[0018] In a preferred embodiment of the present invention, the polyamine is diethylamine or triethylamine.

[0019] In a preferred embodiment of the present invention, the mass ratio of the phytic acid-graphene oxide quantum dot complex to the piperazine is 1-3:1.

[0020] The beneficial effects of the present invention are as follows: By adding the phytic acid-graphene oxide quantum dot complex to the aqueous monomer, a phytic acid-graphene oxide quantum dot complex-doped polyamide nanofiltration membrane is prepared by interfacial polymerization. The preparation of an ultra-thin polyamide organic nanofiltration membrane layer can greatly reduce the liquid transport resistance and improve the flux of the membrane layer. Under the test conditions of room temperature and 0.6 MPa, it has a high rejection rate (above 97%) for a 0.2 wt% magnesium sulfate solution, and the pure water flux is 70-80 LHM. Description of the Drawings

[0021] Figure 1 It is a scanning electron microscope photograph of the organic nanofiltration membrane layer of the graphene oxide polyamide nanofiltration membrane prepared in Comparative Example 1 of the present invention.

[0022] Figure 2 It is a scanning electron microscope photograph of the organic nanofiltration membrane layer of the phytic acid-graphene oxide quantum dot-doped polyamide nanofiltration membrane prepared in Example 1 of the present invention.

[0023] Figure 3 It is a scanning electron microscope photograph of the organic nanofiltration membrane layer of the phytic acid-graphene oxide quantum dot-doped polyamide nanofiltration membrane prepared in Example 2 of the present invention. Detailed Embodiments

[0024] The technical solutions of the present invention are further described and illustrated below through specific embodiments in conjunction with the drawings.

[0025] The modified Hummers method in the following comparative examples and examples specifically includes:

[0026] (1) Take a 1000 mL beaker, wash and dry it, add 3 g of flake graphite, slowly add 360 mL of concentrated sulfuric acid (98% H2SO4) and 40 mL of concentrated phosphoric acid (95% H3PO4) under magnetic stirring, and then slowly add 18 g of potassium permanganate (KMnO4) in batches; move the beaker to a 50 °C oil bath and stir for 12 h. Take out the beaker and let it cool naturally to room temperature. Slowly pour the reaction solution onto the ice cubes of 400 mL of dilute hydrogen peroxide (containing 18 mL of 30% H2O2), and the solution turns bright yellow;

[0027] (2) The above solution is subjected to cross-flow filtration using a tubular ceramic membrane with a pore size of 0.05 μm for impurity removal to obtain a graphene oxide solution after impurity removal. Its basic principle is to utilize the pore size screening effect of the ceramic membrane, that is, the filtration pore size of the tubular ceramic membrane is smaller than the size of the GO sheets, so that the GO sheets cannot flow out through the tubular ceramic membrane, but instead circulate back to the feed liquid bucket with the liquid in the pipeline. This not only does not clog the membrane pores and ensures the smoothness of the membrane pores, but also crushes and exfoliates the larger-sized GO sheets; the filtration pore size of the tubular ceramic membrane is larger than the size of the impurity ions in the GO solution, enabling acid radicals and metal ions such as H + 、K + 、Mn 2+ etc. to easily pass through the pores of the tubular ceramic membrane and be discharged. By repeating this cycle, the separation of GO from waste acid, K + 、and Mn 2+ etc. metal ions is achieved, as well as the collection of the GO solution, completing the washing and impurity removal of GO;

[0028] (3) Dilute or concentrate according to the required concentration to obtain graphene oxide aqueous solutions with different concentrations.

[0029] Comparative Example 1

[0030] (1) Use the above modified Hummers method to prepare a graphene oxide aqueous solution with a concentration of 10 mg / mL;

[0031] (2) Stir evenly 10 mg / mL graphene oxide aqueous solution and 0.1 wt% piperazine aqueous solution (where the mass ratio of graphene oxide to piperazine is 1:1), add 1 wt% PEG1000 and 1 wt% diethylamine, and ultrasonicate for 30 min to prepare a uniform aqueous solution;

[0032] (3) Immerse 20KD polyethersulfone after ethanol and water washing in a 0.2 wt% TMC n-hexane solution, take it out after reacting at room temperature for 10 min, soak it in water and blow it dry with an air gun; then immerse it in the above aqueous solution, take it out after reacting at room temperature for 10 min, soak it in water and blow it dry with an air gun, repeat this step once, then place it in a cool place to air dry and put it into a 50 °C oven for heat treatment for 15 min, and then cool it with the furnace to prepare a graphene oxide polyamide nanofiltration membrane, and the thickness of the organic nanofiltration membrane layer is 200 nm (as Figure 1 shown).

[0033] The graphene oxide-doped polyamide nanofiltration membrane prepared in this comparative example is tested at room temperature and a pressure of 0.6 MPa, with a pure water flux of 46 LHM and a rejection rate of 96.3% for a 0.2 wt% magnesium sulfate solution.

[0034] Comparative Example 2

[0035] (1) Prepare an aqueous solution of graphene oxide quantum dots with a concentration of 10 mg / mL using the above modified Hummers method. The graphene oxide is sonicated for 30 min by a high-power ultrasonic instrument (500 w), then reacted in a reaction kettle at 80 °C for 8 h, and then a uniform 10 mg / mL graphene oxide quantum dot solution is obtained through centrifugal washing;

[0036] (2) Stir evenly an aqueous solution of 10 mg / mL graphene oxide quantum dots and a 1:1 aqueous solution of 0.1 wt% piperazine (where the mass ratio of graphene oxide quantum dots to piperazine is 1:1), add 1 wt% PEG1000 and 1 wt% diethylamine, and sonicate for 30 min to prepare a uniform aqueous solution;

[0037] (3) Immerse the 20KD polyethersulfone after being washed with ethanol and water in a 0.2 wt% TMC n-hexane solution, take it out after reacting at room temperature for 10 min, soak it in water and blow it dry with an air gun; then immerse it in the above aqueous solution, take it out after reacting at room temperature for 10 min, soak it in water and blow it dry with an air gun, repeat this step once, and then place it in a cool place to dry and then put it in an oven at 50 °C for heat treatment for 15 min, and then cool it with the furnace to prepare a graphene oxide quantum dot-doped polyamide nanofiltration membrane.

[0038] Test the graphene oxide quantum dot-doped polyamide nanofiltration membrane prepared in this comparative example at room temperature and a pressure of 0.6 MPa. Its pure water flux is 61 LHM, and the rejection rate for a 0.2 wt% magnesium sulfate solution is 97.5%.

[0039] Comparative Example 3

[0040] (1) Stir evenly 200 mg of phytic acid and 100 mL of a 0.1 wt% piperazine aqueous solution, add 1 wt% PEG1000 and 1 wt% diethylamine, and sonicate for 30 min to prepare a uniform aqueous solution;

[0041] (4) Immerse the 20KD polyethersulfone support layer after being washed with ethanol and water in a n-hexane solution of isophthaloyl chloride with a concentration of 0.2 wt%, soak it in water and blow it dry with an air gun after reacting at room temperature for 10 min, and then immerse it in the above aqueous solution, soak it in water and blow it dry with an air gun after reacting at room temperature; repeat this step once;

[0042] (5) Place the material obtained in step (4) in a cool place to dry, then heat-treat it in an oven at 50 °C for 15 min, and then cool it with the furnace to obtain a phytic acid-polyamide nanofiltration membrane.

[0043] Membrane tube performance test: Test the phytic acid-polyamide nanofiltration membrane prepared in this comparative example at room temperature and a pressure of 0.6 MPa. Its pure water flux is 55 LHM, and the rejection rate for a 0.2 wt% magnesium sulfate solution is 98.2%.

[0044] Example 1

[0045] (1) Prepare an aqueous solution of graphene oxide using the above modified Hummers method. The graphene oxide is sonicated for 30 min using a high-power ultrasonic instrument (500 w), then reacted in an 80 °C reaction kettle for 8 h, and then a uniform 10 mg / mL graphene oxide quantum dot solution is obtained through centrifugal washing;

[0046] (2) After uniformly mixing phytic acid and the graphene oxide quantum dot solution (the mass ratio of phytic acid to graphene oxide quantum dots in the graphene oxide quantum dot solution is 5:1), reflux and react at 60 - 90 °C for 1 h to obtain a 20 mg / mL phytic acid-graphene oxide quantum dot composite solution;

[0047] (3) Stir and uniformly mix the above 20 mg / mL phytic acid-graphene oxide quantum dot composite solution and 0.1 wt% piperazine aqueous solution (the mass ratio of the phytic acid-graphene oxide quantum dot composite to piperazine is 1:1), then add 1 wt% PEG1000 and 1 wt% diethylamine, and after ultrasonic treatment, obtain an aqueous solution;

[0048] (4) Immerse the 20KD polyethersulfone support layer after being washed with ethanol and water in a n-hexane solution of 0.2 wt% trimesoyl chloride at room temperature. After reacting for 10 min at room temperature, soak it in water and blow it dry with an air gun, then immerse it in the above aqueous solution, react at room temperature and then soak it in water and blow it dry with an air gun; repeat this step once;

[0049] (5) After air-drying the material obtained in step (5) in a cool place, heat-treat it in an oven at 50 °C for 15 min, and then cool it with the furnace to obtain a phytic acid-graphene oxide quantum dot-doped polyamide nanofiltration membrane, and the thickness of the organic nanofiltration membrane layer is 80 nm (as Figure 2 shown).

[0050] Membrane tube performance test: Test the phytic acid-graphene oxide quantum dot-doped polyamide nanofiltration membrane prepared in this example at room temperature and a pressure of 0.6 MPa. Its pure water flux is 72 LHM, and the rejection rate for a 0.2 wt% magnesium sulfate solution is 98.5%.

[0051] Example 2

[0052] (1) Prepare an aqueous solution of graphene oxide using the above modified Hummers method. The graphene oxide is sonicated for 30 min using a high-power ultrasonic instrument (500 w), then reacted in an 80 °C reaction kettle for 8 h, and then a uniform 10 mg / mL graphene oxide quantum dot solution is obtained through centrifugal washing;

[0053] (2) Mix phytic acid and graphene oxide quantum dot solution (the mass ratio of phytic acid to graphene oxide quantum dots in the graphene oxide quantum dot solution is 5:1) evenly, and then reflux and react at 60 - 90 °C for 1 h to obtain a 20 mg / mL phytic acid-graphene oxide quantum dot composite solution;

[0054] (3) Stir and mix the above 20 mg / mL phytic acid-graphene oxide quantum dot composite solution and 0.1 wt% piperazine aqueous solution (the mass ratio of the phytic acid-graphene oxide quantum dot composite to piperazine is 2:1) evenly, then add 1 wt% PEG1000 and 1 wt% diethylamine, and after ultrasonic treatment, obtain an aqueous solution;

[0055] (5) Immerse the 20KD polyethersulfone support layer after being washed with ethanol and water in a n-hexane solution of 0.2 wt% trimesoyl chloride, react at room temperature for 10 min, then soak in water and blow dry with an air gun, and then immerse in the above aqueous solution, react at room temperature, and then soak in water and blow dry with an air gun; Repeat this step once;

[0056] (6) Place the material obtained in step (5) in a cool place to air dry, then heat-treat it in an oven at 50 °C for 15 min, and then cool it with the furnace to obtain a phytic acid-graphene oxide quantum dot-doped polyamide nanofiltration membrane, and the thickness of the organic nanofiltration membrane layer is 50 nm (as Figure 3 shown).

[0057] Membrane tube performance test: Test the phytic acid-graphene oxide quantum dot-doped polyamide nanofiltration membrane prepared in this example at room temperature and a pressure of 0.6 MPa. Its pure water flux is 80 LHM, and the rejection rate for a 0.2 wt% magnesium sulfate solution is 97.8%.

[0058] Example 3

[0059] (1) Prepare an aqueous solution of graphene oxide using the above modified Hummers method. The graphene oxide is ultrasonically treated with a high-power ultrasonic instrument (500 w) for 30 min, then reacted in a reaction kettle at 80 °C for 8 h, and then centrifuged and washed to obtain a uniform 10 mg / mL graphene oxide quantum dot solution;

[0060] (2) Mix phytic acid and graphene oxide quantum dot solution (the mass ratio of phytic acid to graphene oxide quantum dots in the graphene oxide quantum dot solution is 20:1) evenly, and then reflux and react at 60 - 90 °C for 1 h to obtain a 20 mg / mL phytic acid-graphene oxide quantum dot composite solution;

[0061] (3) Stir and mix evenly the above-mentioned phytic acid-graphene quantum dot composite solution with a concentration of 20 mg / mL and 0.1 wt% aqueous piperazine solution (the mass ratio of phytic acid-graphene quantum dot composite to piperazine is 1:1), then add 1 wt% PEG1000 and 1 wt% diethylamine, and after ultrasonic treatment, obtain an aqueous solution;

[0062] (5) Immerse the 20KD polyethersulfone support layer after being washed with ethanol and water in a n-hexane solution of trimesoyl chloride with a concentration of 0.2 wt%, react at room temperature for 10 min, then soak in water and blow dry with an air gun, and then immerse in the above aqueous solution, react at room temperature and then soak in water and blow dry with an air gun; Repeat this step once;

[0063] (6) After air-drying the material obtained in step (5) in a cool place, heat-treat it in an oven at 50 °C for 15 min, and then cool it in the furnace to obtain a phytic acid-graphene quantum dot-doped polyamide nanofiltration membrane.

[0064] Membrane tube performance test: Test the phytic acid-graphene quantum dot-doped polyamide nanofiltration membrane prepared in this example at room temperature and a pressure of 0.6 MPa. Its pure water flux is 77 LHM, and the rejection rate for a 0.2 wt% magnesium sulfate solution is 97.2%.

[0065] The above is only a preferred embodiment of the present invention, and thus the scope of implementation of the present invention cannot be limited thereby. That is, equivalent changes and modifications made according to the scope of the present invention patent and the content of the specification should still fall within the scope covered by the present invention.

Claims

1. Application of phytic acid-graphene oxide quantum dot composite as an aqueous monomer in the preparation of polyamide nanofiltration membranes, characterized in that: The preparation method of the phytic acid-graphene oxide quantum dot composite includes: preparing an aqueous solution of graphene oxide by a modified Hummers method, then subjecting it to ultrasonic treatment at 450-550 W and carrying out a heating reaction to obtain a graphene oxide quantum dot solution, and then preparing the phytic acid-graphene oxide quantum dot composite by a solution synthesis method using the graphene oxide quantum dot solution and phytic acid as raw materials.

2. The application according to claim 1, wherein: The preparation method of the phytic acid-graphene oxide quantum dot composite includes: (1) Preparing an aqueous solution of graphene oxide by a modified Hummers method, then subjecting it to ultrasonic treatment at 450-550 W for 25-35 min, then reacting at 75-85 °C for 7-9 h, and then carrying out centrifugal washing to obtain a graphene oxide quantum dot solution; (2) After uniformly mixing phytic acid and the above-mentioned graphene oxide quantum dot solution, carrying out a heating reflux reaction at 60-90 °C for 0.8-1.2 h to obtain a solution of the phytic acid-graphene oxide quantum dot composite.

3. The application according to claim 1 or 2, characterized in that: In the phytic acid-graphene oxide quantum dot composite, the mass ratio of phytic acid to graphene oxide quantum dots is 1-20:

1.

4. The application according to claim 3, wherein: In the phytic acid-graphene oxide quantum dot composite, the mass ratio of phytic acid to graphene oxide quantum dots is 5-10:

1.

5. A polyamide nanofiltration membrane, characterized in that: It includes a polyethersulfone ultrafiltration support layer and an organic nanofiltration membrane layer formed on the polyethersulfone ultrafiltration support layer by interfacial polymerization. In this interfacial polymerization, the aqueous phase monomer consists of a phytic acid-graphene oxide quantum dot composite and piperazine, the acid acceptor is a polyamine, and the organic phase monomer is 1,3,5-benzenetricarbonyl chloride. The preparation method of the phytic acid-graphene oxide quantum dot composite includes: preparing an aqueous solution of graphene oxide by a modified Hummers method, then subjecting it to ultrasonic treatment at 450-550 W and carrying out a heating reaction to obtain a graphene oxide quantum dot solution, and then preparing the phytic acid-graphene oxide quantum dot composite by a solution synthesis method using the graphene oxide quantum dot solution and phytic acid as raw materials.

6. The polyamide nanofiltration membrane according to claim 5, wherein: The preparation method of the phytic acid-graphene oxide quantum dot composite includes: (1) Preparing an aqueous solution of graphene oxide by a modified Hummers method, then subjecting it to ultrasonic treatment at 450-550 W for 25-35 min, then reacting at 75-85 °C for 7-9 h, and then carrying out centrifugal washing to obtain a graphene oxide quantum dot solution; (2) After uniformly mixing phytic acid and the above-mentioned graphene oxide quantum dot solution, carrying out a heating reflux reaction at 60-90 °C for 0.8-1.2 h to obtain a solution of the phytic acid-graphene oxide quantum dot composite.

7. The polyamide nanofiltration membrane according to claim 5, characterized in that: In the phytic acid-graphene oxide quantum dot composite, the mass ratio of phytic acid to graphene oxide quantum dots is 1-20:

1.

8. The polyamide nanofiltration membrane according to claim 7, characterized in that: In the phytic acid-graphene oxide quantum dot composite, the mass ratio of phytic acid to graphene oxide quantum dots is 5-10:

1.

9. The polyamide nanofiltration membrane according to claim 5, wherein: The polyamine is diethylamine or triethylamine.

10. A polyamide nanofiltration membrane according to claim 5, wherein: The mass ratio of the phytic acid-graphene oxide quantum dot composite to piperazine is 1-3:1.

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