Preparation of ceramic / polymer modified filter membrane and its application in water treatment

Abstract

The application provides preparation of a ceramic / polymer modified filter membrane and application thereof in water treatment, and belongs to the field of membrane materials and water treatment. A calcium salt solution, a sodium hydroxide solution and a phosphate solution are sequentially added into a mixed solvent of oleic acid and ethanol, then the cellulose filter membrane is cleaned and dried, and then the cleaned and dried cellulose filter membrane is reacted in the mixed solution to obtain a calcium phosphate ceramic modified filter membrane; and then the obtained calcium phosphate ceramic modified filter membrane is soaked in a polyethylene imine solution, so that the ceramic / polymer modified filter membrane is obtained. The modified filter membrane can effectively purify complex wastewater containing anionic dyes and cationic dyes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of membrane materials and water treatment, and particularly relates to a preparation of a ceramic / polymer modified filter membrane and application thereof in water treatment. BACKGROUND

[0002] Dyes have the characteristics of rich color and strong coloring power, and are widely used in the textile industry, the ink industry, the cosmetics industry and other industries. The development of the textile and coating industries has increased the demand for synthetic dyes year by year, resulting in a large amount of dye wastewater. According to statistics, a large textile mill produces about 320,000 tons of organic wastewater per day. Dye wastewater has the characteristics of high toxicity and persistence, which poses a safety hazard to normal water use by residents, and therefore it is urgent to propose technologies and materials that can effectively treat dye wastewater.

[0003] Water treatment technology based on membrane separation has the advantages of continuous operation, small area occupation and high water quality, and is an effective solution for treating organic small molecule wastewater. For example, Wasim et al. prepared a polyvinylidene fluoride / carbon nanotube / chitosan filter membrane, and the removal rate of reactive orange 16 reached 91% (Carbohydrate Polymers, 2017, 174, 474); Khajavian et al. prepared a polyvinyl alcohol / chitosan / ZIF-8 filter membrane, and the removal rate of malachite green reached 84.55% (Separation and Purification Technology, 2020, 241, 11675); Nie Huali et al. prepared a polyacrylonitrile / oxidized graphene filter membrane, and the removal rate of malachite green was 78%~94.5%, and the removal rate of methylene blue dye was 70~98%. Although these studies have made certain progress, there are still certain deficiencies, such as the fact that the filter membranes reported so far do not exhibit ideal removal effects for complex wastewater containing anionic / cationic dyes. SUMMARY

[0004] In view of the above problems, the present application provides a preparation of a ceramic / polymer modified filter membrane and application thereof in water treatment, which modifies the cellulose filter membrane by ceramic material modification and polymer molecule modification, so that the obtained modified filter membrane can simultaneously remove anionic / cationic dyes in mixed pollutants.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions.

[0006] The first object of the present application is to protect a preparation method of a ceramic / polymer modified filter membrane, which comprises the following steps:

[0007] 1) calcium salt solution, sodium hydroxide solution and phosphate solution are sequentially added to a mixed solvent of oleic acid and ethanol, and then transferred to a reaction kettle after stirring;

[0008] 2) after washing and drying the cellulose filter membrane, immerse it in the reaction kettle of step 1) to react, and after the reaction, wash and dry the filter membrane to obtain a calcium phosphate ceramic modified filter membrane;

[0009] 3) immerse the calcium phosphate ceramic modified filter membrane obtained in step 2) in a polyethyleneimine solution, and after washing and drying the filter membrane, obtain the ceramic / polymer modified filter membrane.

[0010] Further, the calcium salt solution in step 1) is one or more of calcium chloride, calcium chloride dihydrate, and calcium nitrate tetrahydrate, and the concentration is 1.2-2.0% (w / v).

[0011] Further, the concentration of the sodium hydroxide solution in step 1) is 3-7% (w / v).

[0012] Further, the phosphate salt solution in step 1) is one or more of sodium hexametaphosphate, disodium hydrogen phosphate dodecahydrate, disodium hydrogen phosphate dihydrate, and sodium dihydrogen phosphate dihydrate, and the concentration is 2-5% (w / v).

[0013] Further, the mass ratio of the calcium salt solution, the sodium hydroxide solution, and the phosphate salt solution used in step 1) is 2:2:1.

[0014] Further, the mass ratio of oleic acid and ethanol in the mixed solvent in step 1) is 1:3-3:1.

[0015] Further, the temperature of the reaction in step 2) is 120-250 ℃, and the time is 12-48 hours.

[0016] Further, the concentration of the polyethyleneimine solution in step 3) is 0.1-2% (w / v), and the molecular weight of the polyethyleneimine used is 10,000-60,000.

[0017] Further, the time of the immersion in step 3) is 5-48 hours.

[0018] Further, the washing in steps 2) and 3) is one or more of water and / or ethanol flushing and ultrasonic cleaning.

[0019] Further, the drying in steps 2) and 3) is one or more of heating drying and normal temperature drying, and the temperature range is 20-100 ℃.

[0020] The second object of the present application is to protect the ceramic / polymer modified filter membrane prepared by the above method.

[0021] A third object of the present application is to protect the use of the ceramic / polymer modified filter membrane in water treatment, in particular for the treatment of wastewater containing both anionic and cationic dyes.

[0022] The present application proposes a filter membrane modification scheme modified by ceramic material and then by polymer molecules, wherein the ceramic material is arranged in nanowire array on the filter membrane, which can increase the specific surface area of the filter membrane and efficiently remove cationic dyes; the polymer molecules can change the surface charge of the filter membrane, so that it is positively charged, thereby efficiently removing anionic dyes; therefore, under the synergistic cooperation of the two, the obtained modified filter membrane can realize efficient purification of complex wastewater containing both anionic dyes and cationic dyes.

[0023] The present application has the following beneficial effects:

[0024] (1) The present application creatively proposes a filter membrane modification strategy, which on one hand increases the removal rate of cationic dyes through ceramic modification, and on the other hand increases the removal rate of anionic dyes through polymer modification, and has high selectivity for both anionic and cationic dyes.

[0025] (2) The present application improves the purification performance of the filter membrane for dye wastewater through component and structure control. On the component, the surface of the calcium phosphate ceramic is negatively charged, and the surface of the polyethyleneimine polymer molecule is positively charged, which can selectively adsorb cationic dyes and anionic dyes respectively; on the structure, the ceramic nanowire array increases the adsorption surface and improves the dispersion degree of the polymer molecules on the filter membrane surface.

[0026] (3) The preparation method provided by the present application has the advantages of easy-to-obtain raw materials, low price, simple instrument and equipment, and simple process operation, and has good economic and environmental benefits. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The scanning electron microscope image of the cellulose filter membrane prepared in Comparative Example 1.

[0028] Figure 2 The scanning electron microscope image of the calcium phosphate ceramic modified filter membrane prepared in Comparative Example 2.

[0029] Figure 3 The scanning electron microscope image of the ceramic / polymer modified filter membrane prepared in the embodiment.

[0030] Figure 4 The infrared spectrum of the ceramic / polymer modified filter membrane prepared in the embodiment. DETAILED DESCRIPTION

[0031] A ceramic / polymer modified filter membrane, the preparation thereof comprises the following steps:

[0032] 1) calcium salt solution, sodium hydroxide solution, phosphate solution were added into the mixed solvent of oleic acid and ethanol (1:3~3:1, w / w) in the order of mass ratio 2:2:1, stirred and then transferred into the reaction kettle;

[0033] 2) after washing and drying, the cellulose filter membrane was immersed in the reaction kettle of step 1), the reaction kettle was placed in the heating device, and reacted at 120~250 ℃ for 12~48 hours. After the reaction was completed, the filter membrane was washed and dried to obtain a calcium phosphate ceramic modified filter membrane;

[0034] 3) the calcium phosphate ceramic modified filter membrane obtained in step 2) was soaked in a polyethyleneimine solution for 5~48 hours, and then the filter membrane was washed and dried to obtain the ceramic / polymer modified filter membrane.

[0035] In step 1), the calcium salt solution is an aqueous solution of one or more of calcium chloride, calcium chloride dihydrate, calcium nitrate tetrahydrate, with a concentration of 1.2~2.0%(w / v). The concentration of the sodium hydroxide solution is 3~7%(w / v). The phosphate solution is an aqueous solution of one or more of sodium hexametaphosphate, disodium hydrogen phosphate dodecahydrate, disodium hydrogen phosphate dihydrate, sodium dihydrogen phosphate dihydrate, with a concentration of 2~5%(w / v).

[0036] In step 3), the concentration of the polyethyleneimine solution is 0.1~2%(w / v), and the molecular weight of the polyethyleneimine used is 10000~60000.

[0037] In order to make the content of the application more convenient to understand, the technical solutions of the application will be further described below in combination with specific embodiments, but the application is not limited thereto. Examples

[0038] (1) 10 g of oleic acid and 14 g of ethanol were mixed, and 40 g of calcium chloride dihydrate solution with a concentration of 1.5%(w / v), 40 g of sodium hydroxide solution with a concentration of 5%(w / v), and 20 g of sodium dihydrogen phosphate dihydrate solution with a concentration of 2.8wt% were added under continuous stirring, and then transferred into the reaction kettle after mixing uniformly;

[0039] (2) after ultrasonic cleaning in anhydrous ethanol for 5 minutes, the cellulose filter membrane was heated and dried at 60℃, then immersed in the reaction kettle, the reaction kettle was placed in the heating device, and reacted at 180℃ for 24 hours. After the reaction kettle was cooled with the furnace, the filter membrane was taken out, washed with anhydrous ethanol, immersed in water for ultrasonic cleaning for 5 minutes, and then heated and dried at 60℃ to obtain a calcium phosphate ceramic modified filter membrane;

[0040] (3) Prepare a polyethyleneimine aqueous solution with a concentration of 0.4% (w / v), and make it uniform by ultrasonic or stirring. Soak the ceramic-modified filter membrane obtained in step (2) in the obtained polyethyleneimine aqueous solution for 24 hours, then take out the filter membrane, rinse it clean with water, and heat dry it at 60°C to obtain a ceramic / polymer-modified filter membrane.

[0041] Comparative Example 1

[0042] After ultrasonic cleaning the cellulose filter membrane in anhydrous ethanol for 5 minutes, heat dry it at 60°C to obtain a treated cellulose filter membrane.

[0043] Comparative Example 2

[0044] (1) Mix 10 g of oleic acid and 14 g of ethanol, and under continuous stirring, add 40 g of a calcium chloride dihydrate solution with a concentration of 1.5% (w / v), 40 g of a sodium hydroxide solution with a concentration of 5% (w / v), and 20 g of a sodium phosphate dibasic dihydrate solution with a concentration of 2.8 wt%, and then transfer the mixture to a reaction kettle;

[0045] (2) After ultrasonic cleaning the cellulose filter membrane in anhydrous ethanol for 5 minutes, heat dry it at 60°C, then immerse it in the reaction kettle. Place the reaction kettle in a heating device, and react at 180°C for 24 hours. After the reaction kettle cools with the furnace, take out the filter membrane, rinse it clean with anhydrous ethanol, ultrasonic clean it in water for 5 minutes, and then heat dry it at 60°C to obtain a calcium phosphate ceramic-modified filter membrane.

[0046] Comparative Example 3

[0047] (1) After ultrasonic cleaning the cellulose filter membrane in anhydrous ethanol for 5 minutes, heat dry it at 60°C to obtain a treated cellulose filter membrane;

[0048] (2) Prepare a polyethyleneimine aqueous solution with a concentration of 0.4% (w / v), and make it uniform by ultrasonic or stirring. Soak the cellulose filter membrane obtained in step (2) in the obtained polyethyleneimine aqueous solution for 24 hours, then take out the filter membrane, rinse it clean with water, and heat dry it at 60°C to obtain a polymer-modified filter membrane.

[0049] Comparative Example 4

[0050] (1) Mix 10 g of oleic acid and 14 g of ethanol, and under continuous stirring, add 40 g of a calcium chloride dihydrate solution with a concentration of 1.5% (w / v), 40 g of a sodium hydroxide solution with a concentration of 5% (w / v), and 20 g of a sodium phosphate dibasic dihydrate solution with a concentration of 2.8 wt%, and then transfer the mixture to a reaction kettle;

[0051] (2) The cellulose filter membrane is immersed in anhydrous ethanol and ultrasonically cleaned for 5 minutes, then heated and dried at 60°C, and then immersed in a reaction kettle, which is placed in a heating device, and reacted at 180°C for 24 hours. After the reaction kettle is cooled with the furnace, the filter membrane is taken out, washed with anhydrous ethanol, immersed in water and ultrasonically cleaned for 5 minutes, and then heated and dried at 60°C to obtain a calcium phosphate ceramic modified filter membrane;

[0052] (3) A polyethyleneimine aqueous solution with a concentration of 0.4% (w / v) is prepared, and ultrasonic or stirring is performed to make it uniform. The ceramic modified filter membrane obtained in step (2) is immersed in the obtained polyethyleneimine aqueous solution for 12 hours, and then the filter membrane is taken out, washed with water, and heated and dried at 60°C to obtain a ceramic / polymer modified filter membrane.

[0053] Figure 1 The scanning electron microscope image of the cellulose filter membrane prepared in Comparative Example 1 is shown in the figure. As can be seen from the figure, the cellulose filter membrane is composed of long fibers interwoven with each other, and the diameter of the long fibers is 20-30 μm.

[0054] Figure 2 The scanning electron microscope image of the calcium phosphate ceramic modified filter membrane prepared in Comparative Example 2 is shown in the figure. As can be seen from the figure, dense and uniform one-dimensional linear calcium phosphate ceramic grows on the long fibers of the cellulose filter membrane, and the one-dimensional linear calcium phosphate ceramic is vertically arranged on the surface of the fibers. The diameter of the one-dimensional linear calcium phosphate ceramic is nanoscale, which is much smaller than the diameter of the long fibers in the cellulose filter membrane, so it can significantly increase the surface and provide abundant adsorption sites.

[0055] Figure 3 The scanning electron microscope image of the ceramic / polymer modified filter membrane prepared in the example is shown in the figure. As can be seen from the figure, after the modification of the polyethyleneimine polymer, the micro-morphology of the filter membrane does not change significantly, which indicates that the polyethyleneimine is loaded on the ceramic modified filter membrane in the form of molecular modification.

[0056] Figure 4 The infrared spectrum of the ceramic / polymer modified filter membrane prepared in the example is shown in the figure. As can be seen from the figure, the absorption bands at 603, 561, 1030 cm −1 belong to PO4 3− of calcium phosphate, the absorption band at 1370 cm −1 belongs to C-N of polyethyleneimine, and the absorption band at 1560 cm −1 belongs to N-H of polyethyleneimine, which indicates that the calcium phosphate ceramic and the polyethyleneimine polymer are successfully modified on the filter membrane.

[0057] Surface potential analysis:

[0058] The surface potential was tested by using a solid surface Zeta potential tester. The results showed that the Zeta potential of the ceramic modified filter membrane prepared in Comparative Example 2 was -17 mV, because the surface of calcium phosphate was negatively charged, and the Zeta potential of the ceramic / polymer modified filter membrane prepared in the examples was 22 mV, because the surface of polyethyleneimine was positively charged.

[0059] Performance test:

[0060] The filter membranes obtained in the examples and comparative examples were loaded into a filter, and the absorbance of the filtrate was tested by using a UV-visible near-infrared spectrophotometer, denoted as A. C t , so as to investigate the purification effect of the filter membranes on the dye wastewater (the concentrations of the cationic dye methylene blue and the anionic dye congo red in the aqueous solution were both 10 mg / L). The pollutant removal rate was calculated according to the following formula, and the results are shown in Table 1:

[0061] Removal rate = (1- C t / C 0) x 100%.

[0062] Table 1

[0063]

[0064] As can be seen from Table 1, the removal rates of the cellulose filter membrane prepared in Comparative Example 1 on methylene blue and congo red were 83.55% and 45.90% respectively, and the removal rate on the cationic dye was higher than that on the anionic dye, because the cellulose filter membrane surface contained rich hydroxyl groups, so that the surface was negatively charged, but the removal rate was low and the purification efficiency was not high, because the adsorption surface of the long fibers in the cellulose filter membrane was small.

[0065] The removal rates of the ceramic modified filter membrane prepared in Comparative Example 2 on methylene blue and congo red were 92.05% and 24.68% respectively, and the removal rate on the anionic dye was significantly higher than that on the cationic dye, because the calcium phosphate ceramic modification made the surface of the filter membrane negatively charged, and the electrostatic attraction with the cationic dye was stronger.

[0066] The removal rates of the polymer modified filter membrane prepared in Comparative Example 3 on methylene blue and congo red were 13.65% and 93.15% respectively, that is, the purification effect was worse than that of the ceramic / polymer modified filter membrane prepared in the examples, because the one-dimensional linear calcium phosphate ceramic arranged vertically made the polymer molecular loading higher and the dispersion better.

[0067] The removal rates of methylene blue and congo red of the ceramic / polymer modified filter membrane prepared in Comparative Example 4 were 18.07% and 89.10%, respectively; while the removal rates of methylene blue and congo red of the ceramic / polymer modified filter membrane prepared in the embodiment were increased to 20.42% and 95.02%, respectively, because the loading amount of polyethyleneimine was increased with the increase of the soaking time; in addition, the removal rate of the ceramic / polymer modified filter membrane prepared in the embodiment to the anionic dye congo red was significantly higher than that to the cationic dye methylene blue, because the polyethyleneimine polymer made the surface of the filter membrane positively charged, and the electrostatic attraction to the anionic dye was stronger.

[0068] It can also be known from the above data that the selectivity of the ceramic / polymer modified filter membrane prepared in the embodiment to the anionic dye congo red was high, while the selectivity of the ceramic modified filter membrane prepared in Comparative Example 2 to the cationic dye methylene blue was high, and the combination of the ceramic / polymer modified filter membrane prepared in the embodiment and the ceramic modified filter membrane prepared in Comparative Example 2 could effectively remove the mixed pollutants containing coexisting anionic and cationic dyes, and the removal rates of methylene blue and congo red were 86.31% and 87.72%, respectively, which were significantly higher than the effect of the combination of the polymer modified filter membrane prepared in Comparative Example 3 and the ceramic modified filter membrane prepared in Comparative Example 2, proving that the double-layer modification of the present application had a good synergistic effect.

[0069] It is easy for those skilled in the art to understand that the above description is only a preferred example of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a ceramic / polymer modified filter membrane, characterized in that, Includes the following steps: 1) Add calcium salt solution, sodium hydroxide solution, and phosphate solution sequentially to a mixed solvent of oleic acid and ethanol, stir, and then transfer to a reaction vessel; 2) After cleaning and drying the cellulose filter membrane, immerse it in the reaction vessel of step 1) for reaction. After the reaction is completed, clean and dry the filter membrane to obtain nanowire-shaped calcium phosphate ceramic modified filter membrane. 3) The nanowire-shaped calcium phosphate ceramic modified filter membrane obtained in step 2) is immersed in a polyethyleneimine solution, and then the filter membrane is washed and dried to obtain the ceramic / polymer modified filter membrane.

2. The method for preparing a ceramic / polymer modified filter membrane according to claim 1, characterized in that, The calcium salt solution mentioned in step 1) is an aqueous solution of one or more of calcium chloride and calcium nitrate tetrahydrate, with a concentration of 1.2~2.0% w / v.

3. The method for preparing a ceramic / polymer modified filter membrane according to claim 1, characterized in that, The concentration of the sodium hydroxide solution mentioned in step 1) is 3~7% w / v.

4. The method for preparing a ceramic / polymer modified filter membrane according to claim 1, characterized in that, The phosphate solution mentioned in step 1) is an aqueous solution of one or more of sodium hexametaphosphate, disodium hydrogen phosphate dihydrate, and sodium dihydrogen phosphate dihydrate, with a concentration of 2-5% w / v.

5. The method for preparing a ceramic / polymer modified filter membrane according to claim 1, characterized in that, The mass ratio of the calcium salt solution, sodium hydroxide solution, and phosphate solution used in step 1) is 2:2:

1.

6. The method for preparing a ceramic / polymer modified filter membrane according to claim 1, characterized in that, In step 1), the mass ratio of oleic acid to ethanol in the mixed solvent is 1:3 to 3:

1.

7. The method for preparing a ceramic / polymer modified filter membrane according to claim 1, characterized in that, The reaction in step 2) is carried out at a temperature of 120~250 ℃ for 12~48 hours.

8. The method for preparing a ceramic / polymer modified filter membrane according to claim 1, characterized in that, The concentration of the polyethyleneimine solution in step 3) is 0.1-2% w / v, wherein the molecular weight of the polyethyleneimine used is 10,000-60,000.

9. The method for preparing a ceramic / polymer modified filter membrane according to claim 1, characterized in that, The soaking time described in step 3) is 5 to 48 hours.

10. An application of a ceramic / polymer modified filter membrane prepared by any of the methods described in claims 1 to 9 in water treatment.

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