CN111672328B - Carboxylated polyacrylonitrile porous membrane for removing fluorine and preparation method thereof - Google Patents
Carboxylated polyacrylonitrile porous membrane for removing fluorine and preparation method thereof Download PDFInfo
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
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Abstract
The invention discloses a carboxylated polyacrylonitrile porous membrane for removing fluorine and a preparation method thereof, wherein the preparation method comprises the following steps: performing carboxylation reaction on polyacrylonitrile porous membrane substrate materials with different structures to obtain a carboxylated polyacrylonitrile porous membrane; and carrying out acid activation reaction on the carboxylated polyacrylonitrile porous membrane to obtain the carboxylated polyacrylonitrile porous membrane for removing fluorine. The invention has the advantages that: the preparation method of the carboxylated polyacrylonitrile porous membrane for removing fluorine provided by the invention has the advantages of simple process, higher process controllability, and capability of carrying out industrial production, and the carboxylated polyacrylonitrile porous membrane for removing fluorine can be prepared by adopting two steps.
Description
Technical Field
The invention belongs to the technical field of material preparation, and particularly relates to a carboxylated polyacrylonitrile porous membrane for removing fluorine and a preparation method thereof.
Background
The fluorine element is a trace vital element in a human body, and the ingestion of a proper amount of fluorine can help the human body to maintain the health of bones and teeth, but the long-term excessive ingestion of fluorine is unfavorable for the health of the human body, for example, the fluorine disease is caused. The human body mainly takes in fluorine element through drinking water, the fluorine is taken as one of the most abundant anions in underground water in the world, and China, India, Sri Lanka and east Africa are all provided with serious problems related to high-fluorine water, so that the removal of the fluorine in the drinking water has important research significance.
At present, the main treatment methods for removing fluorine in drinking water comprise a precipitation solidification method, a membrane technology treatment method, an ion exchange method and an adsorption method. Among them, the adsorption method is the most potential fluorine removal method in terms of cost, convenience of operation, adsorption amount, reusability, and the like. In recent years, researchers at home and abroad research and develop a plurality of novel adsorption materials, such as aluminum-based adsorbents, calcium-based adsorbents, metal oxide composite materials, carbon materials, low-cost materials such as soil and biopolymer-based materials. However, currently all adsorbents exist in short sheets for practical large-scale applications. Therefore, the development of a novel adsorbent which has high adsorption capacity, low cost, no secondary pollution and can be repeatedly used has important practical significance and application prospect.
The nanofiber porous membrane is a novel porous membrane material, and due to the high porosity, the low curvature factor and the controllable pore size, the influence of internal concentration polarization on water flux can be effectively reduced, and the nanofiber porous membrane has a good application prospect in the field of water treatment. The development of a functional porous membrane adsorbent material for removing fluorine by combining a membrane treatment technology and an adsorption method is an important research direction for removing fluorine in drinking water.
Disclosure of Invention
In order to solve the above technical problems, the present invention aims to provide a carboxylated polyacrylonitrile porous membrane for fluorine removal and a preparation method thereof.
In order to achieve the above object, the present invention adopts the following technical solutions:
a preparation method of carboxylated polyacrylonitrile porous membrane for removing fluorine comprises the following steps:
the method comprises the following steps: performing carboxylation reaction on polyacrylonitrile porous membrane substrate materials with different structures to obtain a carboxylated polyacrylonitrile porous membrane;
step two: and carrying out acid activation reaction on the carboxylated polyacrylonitrile porous membrane to obtain the carboxylated polyacrylonitrile porous membrane for removing fluorine.
Preferably, the polyacrylonitrile porous membrane base material is prepared by using a non-solvent thermally induced phase separation method or a biaxial stretching method.
Preferably, in the step one, the carboxylation reaction process is to stir and heat the solution in strong alkaline solution at 40-80 ℃ for 0.5-3 h at regular time, and the stirring frequency is 1-2 min every 10 min.
Preferably, the strong alkaline solution is sodium hydroxide or potassium hydroxide solution; the mass concentration range of sodium hydroxide or potassium hydroxide in the strong alkaline solution is 5-30 wt%; the solvent of the strong alkaline solution is a mixed solution of deionized water and ethanol or methanol; the volume ratio of the deionized water to the ethanol or the methanol in the mixed solution is (0-1) to (1-0).
Preferably, in the second step, the acidic activation reaction process is to stir and heat the mixture in a strong acidic solution at 40-80 ℃ for 0.5-3 h at regular time, and the stirring frequency is 1-2 min every 10 min.
Preferably, the solute of the strong acid solution is hydrochloric acid or sulfuric acid solution, and the solvent is deionized water; the pH value range of the strong acid solution is 0-6.
Preferably, the carboxylated polyacrylonitrile porous membrane is washed with water after the acidic activation reaction in the second step.
The carboxylated polyacrylonitrile porous membrane for removing fluorine prepared by the preparation method.
Preferably, the thickness of the carboxylated polyacrylonitrile porous membrane for removing fluorine is 30-400 mu m, the air permeability is 10-100 s/100cc, and the specific surface area is 5-40 m2/g。
The preparation method of the carboxylated polyacrylonitrile porous membrane for removing fluorine provided by the invention has the advantages of simple process, higher process controllability, and capability of carrying out industrial production, and the carboxylated polyacrylonitrile porous membrane for removing fluorine can be prepared by adopting two steps.
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FIG. 1 is a scanning electron micrograph of a carboxylated polyacrylonitrile porous membrane for fluorine removal prepared in example 1 of the present invention;
FIG. 2 is a scanning electron micrograph of a carboxylated polyacrylonitrile porous membrane for fluorine removal prepared in example 2 of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and the embodiments.
A preparation method of carboxylated polyacrylonitrile porous membrane for removing fluorine comprises the following steps:
the method comprises the following steps: preparing polyacrylonitrile porous membrane base materials with different structures by using a non-solvent thermally-induced phase separation method or a biaxial stretching method, and performing carboxylation reaction to obtain a carboxylated polyacrylonitrile porous membrane; the carboxylation reaction process is to stir and heat in strong alkaline solution at 40-80 ℃ for 0.5-3 h at regular time, wherein the stirring frequency is 1-2 min every 10min, and the strong alkaline solution is sodium hydroxide or potassium hydroxide solution; the mass concentration range of sodium hydroxide or potassium hydroxide in the strong alkaline solution is 5-30 wt%; the solvent of the strong alkaline solution is a mixed solution of deionized water and ethanol or methanol; the volume ratio of the deionized water to the ethanol or the methanol in the mixed solution is (0-1) to (1-0).
In the invention, the method for preparing the polyacrylonitrile porous membrane substrate material with different structures by the non-solvent thermally-induced phase separation method or the biaxial stretching method adopts the method in the patent with the application number of 201811572039.5 and the invention name of polyacrylonitrile nano-fiber porous membrane and the preparation method thereof.
Step two: carrying out an acid activation reaction on the carboxylated polyacrylonitrile porous membrane, and washing the carboxylated polyacrylonitrile porous membrane after carrying out the acid activation reaction to obtain the carboxylated polyacrylonitrile porous membrane for removing fluorine; the acid activation reaction process is to stir and heat the mixture for 0.5 to 3 hours in a strong acid solution at the temperature of 40 to 80 ℃ at regular time, wherein the stirring frequency is 1 to 2 minutes every 10 minutes; the solute of the strong acid solution is hydrochloric acid or sulfuric acid solution, and the solvent is deionized water; the pH value range of the strong acid solution is 0-6.
Carboxyl conversion in the activation process is a key factor for improving the fluorine removal capacity, and the appropriate acidic activation treatment conditions can enable-COONa to be completely converted into-COOH, so that a protonated amine group is formed, and the carboxyl and the protonated amine group react with fluorine ions to finally obtain the carboxylated polyacrylonitrile porous membrane with higher fluorine removal capacity.
The carboxylated polyacrylonitrile porous membrane for removing fluorine prepared by the preparation method has the thickness of 30-400 microns, the air permeability of 10-100 s/100cc and the specific surface area of 5-40 m2(ii) in terms of/g. The above carboxylated polyacrylonitrile porous membrane for fluorine removal needs to be subjected to an acidic activation treatment before use.
Example 1
A preparation method of carboxylated polyacrylonitrile porous membrane for removing fluorine comprises the following steps: preparing a polyacrylonitrile nano fiber porous membrane by a biaxial stretching method, wherein the stretching temperature is 130 ℃, and the transverse and longitudinal stretching ratios are both 2; reacting the obtained polyacrylonitrile nano-fiber porous membrane in a 20 wt% sodium hydroxide aqueous solution at 60 ℃ for 1h under the water bath heating condition, stirring at regular time during the reaction, wherein the stirring frequency is 1min every 10min, and performing a carboxylation reaction to prepare the carboxylated polyacrylonitrile nano-fiber porous membrane; step two: reacting the carboxylated polyacrylonitrile nano-fiber porous membrane in a hydrochloric acid solution with the pH value of 2 at 60 ℃ for 1.5h under the water bath heating condition, stirring regularly during the reaction, and stirring for 1min every 10min at the stirring frequency to activate the acidity; and (3) washing the acid activated carboxylated polyacrylonitrile nano fiber porous membrane to prepare the carboxylated polyacrylonitrile porous membrane for removing fluorine.
And (3) carrying out fluorine removal performance test and Scanning Electron Microscope (SEM) characterization on the finally obtained carboxylated polyacrylonitrile nano-fiber porous membrane, wherein the SEM characterization result is shown in figure 1, and the measurement results of air permeability, porosity, specific surface area and fluorine adsorption amount are shown in table 1. As can be seen from FIG. 1, the obtained carboxylated nanofiber membrane porous membrane retains the three-dimensional connected network structure of the polyacrylonitrile nanofiber porous membrane, the pore diameter of the porous membrane is less than 1 μm, and the diameter of the nanofiber is 100 nm.
Example 2
A preparation method of carboxylated polyacrylonitrile porous membrane for removing fluorine comprises the following steps: the polyacrylonitrile porous membrane is prepared by a non-solvent thermally induced phase separation method, the phase separation temperature is 24 ℃, and the phase separation time is 8 min; reacting the obtained polyacrylonitrile nano-fiber porous membrane in a 15 wt% sodium hydroxide aqueous solution at 65 ℃ for 1h under the water bath heating condition, stirring at regular time during the reaction, wherein the stirring frequency is 1min every 10min, and performing a carboxylation reaction to prepare the carboxylated polyacrylonitrile nano-fiber porous membrane; step two: reacting the carboxylated polyacrylonitrile nano-fiber porous membrane in a hydrochloric acid solution with the pH value of 2 at 60 ℃ for 1.5h under the water bath heating condition, stirring regularly during the reaction, and stirring for 1min every 10min at the stirring frequency to activate the acidity; and (3) washing the acid activated carboxylated polyacrylonitrile nano fiber porous membrane to prepare the carboxylated polyacrylonitrile porous membrane for removing fluorine.
The finally obtained carboxylated polyacrylonitrile nano-fiber porous membrane is subjected to fluorine removal performance test and SEM characterization, wherein the SEM characterization results are shown in figure 2, and the measurement results of air permeability, porosity, specific surface area and fluorine adsorption amount are shown in Table 1. As can be seen from FIG. 2, the obtained carboxylated nano porous membrane retains the loose porous structure of the polyacrylonitrile porous membrane, and the pore diameter of the porous membrane is less than 200 nm.
TABLE 1 porous Membrane Performance measurement results
Sample (I) | Example 1 | Example 2 |
Breathability (s/100cc) | 16 | 46 |
Porosity (%) | 92 | 76 |
Specific surface area (m)2/g) | 21.6 | 5.8 |
Fluorine adsorption amount (mg/g) | 30.7 | 12.7 |
Comparative example 1
Comparative example 1 is a review by Indian scholars on Chemical Reviews, entitled Fluoride in watering Water and defluorination of Water (chem. Rev.2012,112, 2454) 2466.
Comparative example 2
Comparative example 2 is a scientific article published by Chinese scholars in Chemical Engineering Journal entitled "Efficient removal of fluoride from aqueous solutions using 3D flow-like Chemical zinc-magnesium-aluminum alkaline oxide microorganisms" (Chemical Engineering Journal 380(2020) 122459).
Compared with the fluorine removal performance of the comparative example 1 and the comparative example 2, the porous membrane material prepared by the method has excellent fluorine removal capability.
It should be noted that the above-mentioned embodiments do not limit the present invention in any way, and all technical solutions obtained by using equivalent alternatives or equivalent variations fall within the protection scope of the present invention.
Claims (4)
1. A preparation method of carboxylated polyacrylonitrile porous membrane for removing fluorine is characterized by comprising the following steps:
the method comprises the following steps: performing carboxylation reaction on polyacrylonitrile porous membrane substrate materials with different structures to obtain a carboxylated polyacrylonitrile porous membrane; wherein the polyacrylonitrile porous membrane base material is prepared by a biaxial stretching method; wherein the carboxylation reaction process is to stir and heat the solution in strong alkaline solution at 40-80 ℃ for 0.5-3 h at regular time, and the stirring frequency is 1-2 min every 10 min; the strong alkaline solution is sodium hydroxide or potassium hydroxide solution; the mass concentration range of sodium hydroxide or potassium hydroxide in the strong alkaline solution is 5-30 wt%; the solvent of the strong alkaline solution is a mixed solution of deionized water and ethanol or methanol; the volume ratio of the deionized water to the ethanol or the methanol in the mixed solution is (0-1) to (1-0);
step two: carrying out an acid activation reaction on the carboxylated polyacrylonitrile porous membrane to obtain the carboxylated polyacrylonitrile porous membrane for removing fluorine; wherein the acidic activation reaction process is to stir and heat the mixture for 0.5 to 3 hours in a strong acid solution at the temperature of 40 to 80 ℃ at regular time, and the stirring frequency is 1 to 2 minutes every 10 minutes.
2. The method for preparing a carboxylated polyacrylonitrile porous membrane for fluorine removal according to claim 1, characterized in that the strongly acidic solution solute is hydrochloric acid or sulfuric acid, and the solvent is deionized water; the pH value range of the strong acid solution is 0-6.
3. The method for preparing a carboxylated polyacrylonitrile porous membrane for fluorine removal according to claim 1, wherein in the second step, the carboxylated polyacrylonitrile porous membrane is subjected to an acid activation reaction and then washed with water.
4. A carboxylated polyacrylonitrile porous membrane for fluorine removal prepared by the preparation method according to any one of claims 1 to 3.
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JP5062972B2 (en) * | 2005-06-14 | 2012-10-31 | 旭化成ケミカルズ株式会社 | Ion removal apparatus and ion removal method |
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