Preparation method of polyelectrolyte membrane based on silicon oxide nanowire and efficient adsorption of heavy metal ions

Abstract

The application discloses a kind of based on silicon oxide nanowire polyelectrolyte membrane preparation method and high-efficiency adsorption to heavy metal ions, and its technical scheme main points are: a kind of polyelectrolyte membrane preparation method based on silicon oxide nanowire SiO2 NWs, and polyelectrolyte composite membrane can effectively adsorb heavy metal ions.The application is successfully synthesized by using layer-by-layer assembly method (LBL) by suction filtration device, three-dimensional self-supporting membrane with high efficiency, large capacity and controllable morphology.The specific steps include preparation of SiO2 NWs, amination of SiO2 NWs, and suction filtration to form SiO2 NWs membrane combined layer-by-layer self-assembly technology to finally prepare three-dimensional self-supporting polyelectrolyte composite membrane.The application has simple process, safe operation, and certain practical application prospect.The porosity of polyelectrolyte membrane is high, and it has good heavy metal adsorption and desorption capacity, so it is an ideal membrane adsorption material.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a method for preparing a polyelectrolyte membrane from silicon oxide nanowires and its efficient adsorption of heavy metal ions. Background Technology

[0002] With the rapid development of industrialization and urbanization, the problem of heavy metal pollution in water environment has received widespread attention. Heavy metals are widely distributed in the water environment, but excessive intake of heavy metals can cause harm to humans and other organisms [1]. To date, various technologies have been reported for the removal of heavy metals, from chemical precipitation [2], ion exchange [3], electrochemical treatment [4], membrane filtration [5] to adsorption [6]. Among them, adsorption has the advantages of simple process, low cost and high removal efficiency, and is considered an economical wastewater treatment process. Therefore, it is of great significance to design and prepare economical and efficient adsorbents. Many efficient materials have been constructed to remove heavy metals from wastewater, such as nanoparticles [7], covalent organic frameworks [8], hydrogels [9], layered double hydroxides

[10] , etc. However, the adsorption of these adsorbents requires centrifugation, which will cause secondary pollution to the aqueous solution, limiting their application in the field of copper ion removal.

[0003] Compared with traditional adsorbents, membrane adsorption often has the advantages of easy separation, simple operation, and avoidance of secondary environmental pollution

[11] . Due to the coordination effect between heavy metals and nitrogen, the polyvinylidene fluoride membrane was modified with hyperbranched polyamide amine, which greatly improved its adsorption capacity for removing heavy metals

[12] . Pei et al. prepared an adsorption membrane with high mechanical strength by covalently grafting poly(maleic anhydride-acrylic acid) and polyethyleneimine (PEI) polyelectrolyte active layer on cellulose support membrane. The Cu(II) adsorption capacity of the active layer was 194 mg / g

[13] . Shao et al. prepared a polyacrylonitrile / branched PEI nanofiber membrane by simple electrospinning and subsequent hydrothermal method. Its Cu(II) adsorption capacity was 209.53 mg / g

[14] . These studies show that polyelectrolytes with abundant adsorption sites are of great significance for improving adsorption performance. However, the preparation of these materials requires special equipment, takes a long time, and the prepared polyelectrolyte membrane has a dense structure and the adsorption sites can be limited.

[0004] The absorbability is poor. Developing methods for preparing polyelectrolyte adsorption membranes with high porosity and more readily available adsorption sites is crucial for their practical application.

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[0010] [6] K. Li, B. Li, X. Li, A novel material poly(N-acryloyl-L-glycine)-brush grafted N-doped magnetic biochar by surface-initiated RAFTpolymerization for efficient elimination of heavy metal ions,Separation andPurification Technology, 292 (2022).

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[0014]

[10] X. Feng, R. Long, L. Wang, C. Liu, Z. Bai, X. Liu, A review onheavy metal ions adsorption from water by layered double hydroxide and itscomposites, Separation and Purification Technology, 284 (2022).

[0015]

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[0016]

[12] H. Sun, Z. Ji, Y. He, L. Wang, J. Zhan, L. Chen, Y. Zhao,Preparation of PAMAM modified PVDF membraneand its adsorption performance forcopperions, Environ Res, 204 (2022) 111943.

[0017]

[13] X. Pei, L. Gan, Z. Tong, H. Gao, S. Meng, W. Zhang, P. Wang, Y.Chen, Robust cellulose-based composite adsorption membrane for heavy metal removal, J HAZARD MATER,406 (2021) 124746.

[0018]

[14] H. Shao, D. Yin, D. Li, Q. Ma, W. Yu, X. Dong, SimultaneousVisual Detection and Removal of Cu2+ with Electrospun Self-SupportingFlexible Amidated Polyacrylonitrile / Branched Polyethyleneimine NanofiberMembranes, ACS Appl Mater Interfaces, 13 (2021) 49288-49300. Summary of the Invention

[0019] The purpose of this invention is to provide a simple, safe, and low-cost method for preparing polyelectrolyte membranes from silica nanowires and its applications.

[0020] The method for preparing a polyelectrolyte membrane from silica nanowires provided by this invention includes the following steps:

[0021] (1) Preparation of silica nanowires: Polyvinylpyrrolidone (PVP) was dissolved in an alcohol solution; deionized water, sodium citrate solution and ammonia were added and shaken well; silicon source and long-chain silane were added and shaken well. The reaction was carried out for 1 to 24 hours, and the reaction products were separated; washed with anhydrous ethanol or water to obtain silica nanowires (SiO2 NWs).

[0022] (2) Aminoation of silica nanowires: The obtained silica nanowires were dried and further calcined in a tube furnace. The calcined SiO2 NWs were mixed with alcohol, and ultrapure water, aminosiloxane (APTES), and ammonia were added. The mixture was shaken and centrifuged to obtain aminoized silica nanowires.

[0023] (3) Preparation of SiO2 NWs-based polyelectrolyte membrane by layer-by-layer self-assembly: The membrane is assembled in a vacuum filtration device, and polyacrylic acid (PAA) and polyethyleneimine (PEI) are repeatedly added to the membrane; after washing with buffer solution, the membrane is cross-linked to obtain a three-dimensional self-supporting polyelectrolyte composite membrane.

[0024] The method for preparing polyelectrolyte membranes based on SiO2 NWs is characterized by the following:

[0025] PAA has a molecular weight of 5,000 to 100,000 and a concentration of 1 to 5 mg / L.

[0026] The method for preparing polyelectrolyte membranes based on SiO2 NWs is characterized in that the buffer solution is morpholine ethanesulfonic acid (MES), with a pH of 4-6 and a concentration of 0.5 M.

[0027] The method for preparing polyelectrolyte membranes based on SiO2 NWs is characterized in that the molecular weight of the PEI is 10,000~60,000 and the concentration is 1~5 mg / L.

[0028] A method for preparing polyelectrolyte membranes based on SiO2 NWs, characterized in that the membrane has a diameter of 5~25 mm and a thickness of 80~800 µm.

[0029] The method for preparing polyelectrolyte membranes based on SiO2 NWs is characterized in that the pressure of the decompression is 0.2~0.9 bar.

[0030] The SiO2 NWs@(PEI / PAA)n polyelectrolyte composite membrane obtained by the SiO2 NWs-based polyelectrolyte membrane preparation method is characterized by assembling PAA / PEI onto the surface of SiO2 NWs through layer-by-layer self-assembly technology, and controlling the flux and thickness of the polyelectrolyte membrane by changing the molecular weight, concentration, pH of PEI and PAA, and the amount of SiO2 NWs used.

[0031] The application of SiO2 NWs@(PEI / PAA)n polyelectrolyte composite membrane in heavy metal adsorption and separation is characterized by improving the removal efficiency of heavy metals through a vacuum integrated device; and by increasing the number of polyelectrolyte layers, controlling the adsorption amount of heavy metals by the SiO2 NWs@(PEI / PAA)n polyelectrolyte composite membrane, and establishing the correlation law between the structure, characteristics and adsorption performance of the material.

[0032] This invention provides a method for preparing SiO2 NWs@(PEI / PAA)n polyelectrolyte composite membranes through layer-by-layer self-assembly. More specifically, it describes a method for synthesizing high-porosity, three-dimensionally self-supporting polyelectrolyte adsorption membranes using electrostatic adsorption on a vacuum filtration device. This method is simple, safe to operate, and has promising practical applications. The prepared polyelectrolyte membrane exhibits a large adsorption capacity and high adsorption efficiency. The flux and thickness of the polyelectrolyte membrane can be controlled by varying the molecular weight and concentration of PEI and PAA, the pH value, and the amount of SiO2 NWs used. The adsorption capacity of the SiO2 NWs@(PEI / PAA)n polyelectrolyte composite membrane for heavy metals can be controlled by increasing the number of polyelectrolyte layers. Simultaneously, the heavy metal ions adsorbed by the polyelectrolyte membrane are reduced to form metal nanoparticles, endowing it with additional catalytic function, making it an ideal membrane material for adsorption separation and recyclability. Attached Figure Description

[0033] Figure 1 shows an electron microscope image of SiO2 NWs and the formed polyelectrolyte composite membrane.

[0034] Figure 2 The graph shows the flux and adsorption capacity of the SiO2 NWs@(PEI / PAA)n polyelectrolyte composite membrane as a function of the number of polyelectrolyte layers.

[0035] Figure 3 shows the breakthrough curves of copper ions at different concentrations in SiO2 NWs@ (PEI / PAA)4.

[0036] Figure 4 shows the infrared spectral characterization of the SiO2 NWs@ (PEI / PAA)n polyelectrolyte composite membrane.

[0037] Figure 5 shows the cycling performance of SiO2 NWs@(PEI / PAA)4. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1: 50 mg of SiO2 NWs were dissolved in 10 mL of ethanol, ammonia and APTES were added, and the mixture was rotated for 10 h. 2.4 mL of the above nanowire solution was taken, and 10 mL of PAA (Mn=5000, pH=5) at a concentration of 1 mg / L and 5 mL of 5 mg / L 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) were added. Crosslinking was carried out for 2 h, and the mixture was assembled into a membrane using a vacuum filtration device. 20 mL of PEI (Mn=10000, pH=5) at a concentration of 1 mg / L was added, and the mixture was filtered through a filtration device for 10–30 min. 20 mL of MES at a concentration of 0.5 M was added. The above operation was repeated to form a SiO2 NWs@(PEI / PAA)n polyelectrolyte composite membrane. Finally, EDC was added for crosslinking, followed by MES cleaning. The throughput time was recorded, and the flux was calculated.

[0040] The obtained polyelectrolyte composite membrane was placed in simulated heavy metal-contaminated wastewater. The changes in heavy metal ion concentration before and after adsorption were measured by atomic absorption spectrophotometer, and the adsorption capacity and removal rate of heavy metal ions by the polyelectrolyte membrane were calculated.

[0041] The polyelectrolyte membrane, after adsorption of heavy metal ions, was desorbed using an acidic desorption solution. The change in heavy metal ion concentration before and after desorption was measured using an atomic absorption spectrophotometer, and the desorption rate was calculated. The membrane was then recycled. The stability of the polyelectrolyte membrane after several cycles of use was determined.

[0042] Example 2: 50 mg of SiO2 NWs was dissolved in 10 mL of ethanol, ammonia and APTES were added, and the mixture was rotated for 10 h. 2.4 mL of the above nanowire solution was taken, and 10 mL of PAA (Mn=250000, pH=6) at a concentration of 1 mg / L and 5 mL of 5 mg / L EDC were added. Crosslinking was carried out for 2 h, and the mixture was assembled into a membrane using a vacuum filtration device. 20 mL of PEI (Mn=60000, pH=6) at a concentration of 1 mg / L was added, and the mixture was filtered through a filtration device after 10-30 min. 20 mL of MES at a concentration of 0.5 M was added. The above operations were repeated to form a SiO2 NWs@(PEI / PAA)6 polyelectrolyte composite membrane. Finally, EDC was added for crosslinking.

[0043] Example 3: 50 mg of SiO2 NWs were dissolved in 10 mL of ethanol, ammonia and APTES were added, and the mixture was rotated for 10 h. 4.8 mL of the above nanowire solution was taken, and 10 mL of PAA (Mn=250000, pH=4) at a concentration of 1 mg / L and 5 mL of 5 mg / L EDC were added. Crosslinking was carried out for 2 h, and the mixture was assembled into a membrane using a vacuum filtration device. 20 mL of PEI (Mn=60000, pH=4) at a concentration of 1 mg / L was added, and the mixture was filtered through a filtration device after 10-30 min. 20 mL of MES at a concentration of 0.5 M was added. The above operations were repeated to form a SiO2 NWs@(PEI / PAA)4 polyelectrolyte composite membrane. Finally, EDC was added for crosslinking.

[0044] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a polyelectrolyte membrane based on SiO2 NWs, characterized in that... The specific steps are as follows: (1) Preparation of silica nanowires: Polyvinylpyrrolidone (PVP) was dissolved in an alcohol solution; deionized water, sodium citrate solution and ammonia were added and shaken well; silicon source and long-chain silane were added and shaken well. The reaction was carried out for 1 to 24 hours, and the reaction products were separated; the products were washed with anhydrous ethanol or water to obtain silica nanowires (SiO2 NWs). (2) Aminoation of silica nanowires: The obtained silica nanowires were dried and further calcined in a tube furnace. The calcined SiO2 NWs were mixed with alcohol, and ultrapure water, aminosiloxane and ammonia were added. The mixture was shaken and centrifuged to obtain aminoized silica nanowires. (3) Preparation of polyelectrolyte membrane based on SiO2 NWs by layer-by-layer self-assembly method: The membrane is assembled in a vacuum filtration device, and the obtained membrane is repeatedly added with polyacrylic acid PAA solution and polyethyleneimine PEI solution; After washing with buffer solution and cross-linking, a three-dimensional self-supporting polyelectrolyte composite membrane is obtained.

2. The method for preparing polyelectrolyte membranes based on SiO2 NWs as described in claim 1, characterized in that... The PAA has a molecular weight of 5,000 to 100,000 and a concentration of 1 to 5 mg / L.

3. The method for preparing polyelectrolyte membranes based on SiO2 NWs as described in claim 1, characterized in that... The buffer solution is morpholine ethanesulfonic acid (MES), with a pH of 4-6 and a concentration of 0.5 M.

4. The method for preparing a polyelectrolyte membrane based on SiO2 NWs as described in claim 1, characterized in that... The PEI has a molecular weight of 10,000 to 60,000 and a concentration of 1 to 5 mg / L.

5. The method for preparing a polyelectrolyte membrane based on SiO2 NWs as described in claim 1, characterized in that... The membrane has a diameter of 5-75 mm and a thickness of 80-1800 µm.

6. The method for preparing a polyelectrolyte membrane based on SiO2 NWs as described in claim 1, characterized in that... The pressure for pressure reduction is 0.2~0.9 bar.

7. The SiO2NWs@(PEI / PAA)n polyelectrolyte composite membrane obtained by the method for preparing SiO2 NWs-based polyelectrolyte membranes as described in any one of claims 1 to 6, characterized in that... PAA / PEI was assembled onto the surface of SiO2 NWs using LBL technology. By changing the molecular weight, concentration, pH of PEI and PAA, and the amount of SiO2 NWs used, the flux and thickness of the polyelectrolyte membrane were controlled.

8. The application of the SiO2 NWs@(PEI / PAA)n polyelectrolyte composite membrane according to claim 7 in the adsorption and separation of heavy metals, characterized in that... By using an integrated decompression device, the removal efficiency of heavy metals is improved; by increasing the number of polyelectrolyte layers, the adsorption capacity of SiO2 NWs@(PEI / PAA)n polyelectrolyte composite membrane for heavy metals is controlled, and the correlation between the material's structure, properties, and adsorption performance is established.

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