A double-unit three-dimensional ordered structure composite film and a preparation method and application thereof

Abstract

The application discloses a kind of double-element three-dimensional ordered structure composite membrane and its preparation method and application, belong to water treatment membrane separation technical field.Preparation method as follows includes the following steps: first, oleic acid and ethanol are mixed, stirred uniformly, and the aqueous solution of calcium salt, sodium hydroxide and phosphate is added, stirred uniformly, transferred to Teflon reaction kettle, placed in filter membrane to react, the obtained composite filter membrane is washed, dried and treated to obtain calcium phosphate composite membrane;Second, copper sulfate, dopamine hydrochloride, tris (hydroxymethyl) aminomethane and hydrogen peroxide are dissolved in water;Then, the calcium phosphate composite membrane is soaked in the above aqueous solution for a period of time, washed, dried, and the above process can be repeated to control the loading amount of polydopamine;Finally, the obtained composite membrane is washed and dried to obtain a double-element three-dimensional ordered structure composite membrane.The double-element three-dimensional ordered structure composite membrane disclosed by the application can effectively remove organic pollutants in water.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of membrane water treatment, and particularly relates to a double-unit three-dimensional ordered structure composite membrane and a preparation method and application thereof. BACKGROUND

[0002] Currently, the pollution of organic wastewater is increasingly serious. Organic matters such as dyes and antibiotics have the characteristics of persistence and high toxicity, which has attracted great attention from relevant departments of the state. For example, the New Pollutant Control Action Plan issued in China in 2022 pointed out that the monitoring and treatment of antibiotics in the environment should be strengthened.

[0003] In order to effectively remove organic pollutants in wastewater, people have proposed and applied various water remediation technologies, such as membrane filtration, adsorption, photocatalytic degradation, catalytic reduction, etc. Compared with traditional distillation, evaporation and degradation methods, filtration methods represented by advanced membrane technology and adsorption methods represented by various adsorbents are widely used because of their simple operation. For example, nanofiltration membranes and reverse osmosis membranes have attracted strong interest due to their low energy consumption and high efficiency. However, nanofiltration and reverse osmosis membranes usually require high pressure and have low water flux, which limits their practical application, and these problems need to be solved. Adsorption methods also have problems such as complex recovery and poor reusability. Combining adsorbents with porous membranes can take advantage of both and avoid their shortcomings.

[0004] Zhu et al. obtained a polydopamine / polyacrylonitrile membrane, which has good removal effect on various dyes, but the agglomeration of polydopamine leads to low water flux (J. Colloid Interface Sci., 2018, 523, 86). Ye et al. constructed an ultrafiltration membrane by co-deposition of dopamine and tobramycin, which has a removal rate of >98.0% for various reactive dyes (molecular weight <1000 Da), but the water flux is not good, with a maximum of only 60.8 L m −2 h −1 bar −1 . Dopamine and tobramycin are only deposited on the surface of the ultrafiltration membrane to form agglomerated particles, and the advantages of high adsorbability of dopamine cannot be fully utilized (Desalination., 2024, 117482).

[0005] Currently, conventional adsorption membranes are mostly planar disordered structures, which leads to agglomeration of adsorbents, few adsorption sites, and low removal efficiency. In the face of these problems, the present application discloses a double-unit three-dimensional ordered structure, which is designed by multiple levels and multiple components to obtain an adsorption membrane with high removal rate and high flux. The innovative three-dimensional ordered structure of the present application effectively inhibits the agglomeration of adsorbents on the membrane surface, increases the adsorption sites, and improves the separation effect of the adsorption membrane on organic pollutants, thereby providing a new design idea for the development of new high-quality adsorption membranes. SUMMARY

[0006] The present application aims at the key problems of existing adsorption membranes, and aims to provide a double-monomer three-dimensional ordered structure composite membrane and a preparation method and application thereof. The method of the present application first obtains a calcium phosphate composite membrane, and then disperses polydopamine particles on the surface of the calcium phosphate composite membrane, effectively inhibits particle agglomeration, increases the surface adsorption site, and improves the pollutant removal rate.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A preparation method of a double-monomer three-dimensional ordered structure composite membrane, comprising the following steps:

[0009] (1) Mix oleic acid and ethanol, stir uniformly, add calcium salt aqueous solution, sodium hydroxide aqueous solution, and phosphate aqueous solution, stir uniformly, transfer to a Teflon reaction kettle, put into a filter membrane for reaction, wash, dry and treat the obtained composite filter membrane to obtain a calcium phosphate composite membrane;

[0010] (2) Mix copper sulfate aqueous solution, dopamine hydrochloride aqueous solution, and tris(hydroxymethyl) aminomethane aqueous solution, and add hydrogen peroxide to prepare an aqueous solution 1;

[0011] (3) Soak the calcium phosphate composite membrane obtained in step (1) in the aqueous solution 1 obtained in step (2) for a period of time, wash and dry, repeat the above process to control the loading amount of polydopamine, and finally wash and dry the obtained composite membrane to obtain a double-monomer three-dimensional ordered structure composite membrane.

[0012] Further, the volume ratio between the oleic acid and ethanol and the three aqueous solutions of calcium salt aqueous solution, sodium hydroxide aqueous solution, and phosphate aqueous solution in step (1) is (60-75):(100-115):(290-310).

[0013] Further, the calcium salt in step (1) is one or both of calcium chloride and calcium nitrate.

[0014] Further, the concentration of the calcium salt aqueous solution in step (1) is 1.3-1.7 %(w / v).

[0015] Further, the concentration of the sodium hydroxide aqueous solution in step (1) is 3-7 %(w / v).

[0016] Further, the phosphate in step (1) is one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, and sodium pyrophosphate.

[0017] Further, the concentration of the phosphate aqueous solution in step (1) is 2.5-3.1 %(w / v).

[0018] Further, the volume ratio of the calcium salt aqueous solution, the sodium hydroxide aqueous solution and the phosphate aqueous solution in step (1) is 2:2:1.

[0019] Further, the reaction temperature in step (1) is 150-250℃, and the reaction time is 10-36 hours.

[0020] Further, the filter membrane in step (1) is one or more of cellulose filter membrane, polytetrafluoroethylene filter membrane, polyether sulfone filter membrane and polyacrylonitrile filter membrane.

[0021] Further, the drying method in step (1) is one or more of atmospheric environment drying, normal pressure heating drying and vacuum heating drying, and the corresponding drying conditions are room temperature / 2-48 hours, 20-70℃ / 1-24 hours, 20-70℃ / 50-1000 Pa / 1-24 hours, respectively.

[0022] Further, the concentration of the copper sulfate in step (2) is 0.05-0.11 %(w / v).

[0023] Further, the concentration of the dopamine hydrochloride in step (2) is 0.1-0.3 %(w / v).

[0024] Further, the concentration of the tris(hydroxymethyl)aminomethane in step (2) is 0.09-0.15 %(w / v).

[0025] Further, the volume ratio of the hydrogen peroxide and water in step (2) is 1:(4000-6000).

[0026] Further, the volume ratio of the copper sulfate aqueous solution, the dopamine hydrochloride aqueous solution and the tris(hydroxymethyl)aminomethane aqueous solution in step (2) is 1:2:2.

[0027] Further, the soaking time in step (3) is 6-24 hours, and the soaking frequency is 1-5 times.

[0028] Further, the drying method in step (3) is one or more of atmospheric environment drying, normal pressure heating drying and vacuum heating drying, and the drying conditions are room temperature / 2-48 hours, 20-70℃ / 1-24 hours, 20-70℃ / 50-1000 Pa / 1-24 hours, respectively.

[0029] In the bi-unit three-dimensional ordered structure composite membrane prepared according to the above steps, the calcium phosphate array is used as a polydopamine adsorbent loading site to form a three-dimensional ordered structure, which sufficiently improves the dispersibility of the polydopamine particles; in addition, the calcium phosphate array is grown in situ on the filter membrane fibers and does not block the filter membrane pore structure, thereby maintaining a high water flux.

[0030] A dibasic three-dimensional ordered structure composite membrane prepared by the above method.

[0031] Application of the above-mentioned dibasic three-dimensional ordered structure composite membrane in water treatment of organic pollutants.

[0032] The present application has the advantages of:

[0033] (1) The present application innovatively proposes a design strategy for a dibasic three-dimensional ordered structure composite membrane, which ingeniously disperses polydopamine particles on a calcium phosphate composite membrane, inhibits the agglomeration of the particles, and increases the surface adsorption sites, thereby exhibiting performance far superior to that of a conventional planar disordered structure composite membrane. In addition, the obtained adsorption membrane exhibits ideal removal rates for anionic dyes and cationic dyes, and has a wide range of applications.

[0034] (2) The adsorption membrane preparation method provided by the present application has the advantages of easy availability of raw materials, low price, simple instruments and equipment, and simple process operation, and has good environmental benefits. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A scanning electron microscope image of the dibasic three-dimensional ordered structure composite membrane prepared in Example 1.

[0036] Figure 2 A scanning electron microscope image of the planar disordered structure composite membrane prepared in Comparative Example 3. DETAILED DESCRIPTION

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

[0038] A preparation method of a dibasic three-dimensional ordered structure composite membrane, the specific steps of which are as follows:

[0039] (1) Mix oleic acid and ethanol, stir uniformly, add an aqueous solution of calcium salt, sodium hydroxide, and phosphate salt, stir uniformly, transfer to a Teflon reaction kettle, and react with a filter membrane. The obtained composite filter membrane is washed, dried, and treated to obtain a calcium phosphate composite membrane.

[0040] (2) Dissolve copper sulfate, dopamine hydrochloride, tris(hydroxymethyl) aminomethane, and hydrogen peroxide in water.

[0041] (3) Soak the calcium phosphate composite membrane obtained in step (1) in the aqueous solution obtained in step (2) for a period of time, wash and dry, and repeat the above process to control the loading amount of polydopamine. Finally, wash and dry the obtained composite membrane to obtain a dibasic three-dimensional ordered structure composite membrane.

[0042] Example 1

[0043] (1) 68 mL oleic acid and 107 mL ethanol mixed solvent, stirring uniformly; sequentially adding 120 mL calcium chloride dihydrate aqueous solution with a concentration of 1.5 %(w / v), 120 mL sodium hydroxide aqueous solution with a concentration of 5 %(w / v), 60 mL sodium dihydrogen phosphate dihydrate aqueous solution with a concentration of 2.8 %(w / v), stirring uniformly, and transferring to a Teflon reaction kettle;

[0044] (2) The cellulose membrane was cleaned in ethanol by ultrasonic for 5 minutes, dried at 60 ℃ under normal pressure, and then placed in a Teflon reaction kettle, and the solvothermal reaction was carried out after sealing, the reaction temperature was 180 ℃, and the reaction time was 24 hours;

[0045] (3) After the reaction was completed, the obtained calcium phosphate composite membrane was cleaned in ethanol by ultrasonic for 5 minutes, and dried at 60 ℃ under normal pressure;

[0046] (4) 40 mL dopamine hydrochloride aqueous solution with a concentration of 0.2 %(w / v), 40 mL tris(hydroxymethyl)aminomethane aqueous solution with a concentration of 0.12 %(w / v), 20 mL copper sulfate pentahydrate aqueous solution with a concentration of 0.08 %(w / v), and 20 μL hydrogen peroxide (30 wt%) were added to a container;

[0047] (5) The calcium phosphate composite membrane obtained in step (3) was soaked in the solution obtained in step (4), and soaked at normal pressure and room temperature for 12 hours, washed with deionized water, and dried at 60 ℃ under normal pressure;

[0048] (6) The composite membrane obtained in step (5) was soaked in the solution obtained in step (5), and soaked at normal pressure and room temperature for 12 hours, washed with deionized water, and dried at 60 ℃ under normal pressure, to obtain a calcium phosphate / polydopamine bi-motif three-dimensional ordered structure composite membrane.

[0049] Example 2

[0050] The preparation scheme was similar to that of Example 1, except that the volumes of oleic acid and ethanol were 64 mL and 111 mL, respectively.

[0051] Example 3

[0052] The preparation scheme was similar to that of Example 1, except that the volumes of oleic acid and ethanol were 72 mL and 103 mL, respectively.

[0053] Example 4

[0054] The preparation scheme was similar to that of Example 1, except that the concentrations of calcium chloride dihydrate, sodium hydroxide, and sodium dihydrogen phosphate dihydrate aqueous solution were 1.3, 3, and 2.5 %(w / v), respectively.

[0055] Example 5

[0056] The preparation scheme is similar to that of Example 1, except that the concentrations of calcium chloride dihydrate, sodium hydroxide, and aqueous sodium dihydrogen phosphate dihydrate are 1.7, 7, and 3.1% (w / v), respectively.

[0057] Example 6

[0058] The preparation scheme is similar to that of Example 1, except that the concentrations of copper sulfate, dopamine hydrochloride, and aqueous tris(hydroxymethyl)aminomethane are 0.05, 0.1, and 0.09% (w / v), respectively, and the volume of hydrogen peroxide is 10 μL.

[0059] Example 7

[0060] The preparation scheme is similar to that of Example 1, except that the concentrations of copper sulfate, dopamine hydrochloride, and aqueous tris(hydroxymethyl)aminomethane are 0.11, 0.3, and 0.15% (w / v), respectively.

[0061] Comparative Example 1

[0062] The cellulose membrane was ultrasonically cleaned in ethanol for 5 minutes and dried at 60°C under normal pressure.

[0063] Comparative Example 2

[0064] (1) 68 mL of an oleic acid and 107 mL of ethanol mixed solvent were stirred uniformly;

[0065] (2) 120 mL of an aqueous calcium chloride dihydrate solution with a concentration of 1.5% (w / v), 120 mL of an aqueous sodium hydroxide solution with a concentration of 5% (w / v), and 60 mL of an aqueous sodium dihydrogen phosphate dihydrate solution with a concentration of 2.8% (w / v) were sequentially added and stirred uniformly, and then transferred to a Teflon reaction kettle;

[0066] (3) The cellulose membrane was ultrasonically cleaned in ethanol for 5 minutes and dried at 60°C under normal pressure, and then placed in the Teflon reaction kettle, sealed, and subjected to a solvothermal reaction at a reaction temperature of 180°C for 24 hours;

[0067] (4) After the reaction was completed, the obtained calcium phosphate composite membrane was ultrasonically cleaned in ethanol for 5 minutes and dried at 60°C under normal pressure.

[0068] Comparative Example 3

[0069] (1) The cellulose membrane was ultrasonically cleaned in ethanol for 5 minutes and dried at 60°C under normal pressure;

[0070] (2) Add 40 mL of 0.2% (w / v) dopamine hydrochloride aqueous solution, 40 mL of 0.12% (w / v) tris(hydroxymethyl)aminomethane aqueous solution, 20 mL of 0.08% (w / v) copper sulfate pentahydrate aqueous solution and 20 μL hydrogen peroxide (30wt%) to the container;

[0071] (3) Immerse the cellulose membrane obtained in step (1) in the solution obtained in step (2) for 12 hours at normal pressure and temperature, rinse with deionized water, and dry at 60°C under normal pressure.

[0072] (4) Immerse the composite membrane obtained in step (3) in the solution obtained in step (2) for 12 hours at normal pressure and temperature, rinse with deionized water, and dry at 60°C under normal pressure to obtain a polydopamine planar disordered structure composite membrane.

[0073] Performance Evaluation

[0074] Pollutant separation experiments were conducted on the composite membranes prepared in the examples and comparative examples. The specific steps are as follows:

[0075] (1) Prepare aqueous solutions of Congo red and methylene blue with a concentration of 10 mg / L respectively, and measure the absorbance of the solutions using a UV-Vis spectrophotometer, denoted as . C 0;

[0076] (2) Place the filter membrane in the sample chamber, draw 10 mL of pollutant aqueous solution with a syringe, connect it to the sample clip, and pass the pollutant solution through the filter membrane using a syringe pump. Set the flow rate of the syringe pump to 120 mL / h.

[0077] (3) After all the pollutant aqueous solution has passed through the filter membrane, the absorbance of the filtrate is measured using a UV-Vis spectrophotometer and recorded as follows: C t The pollutant removal rate is calculated using the following formula:

[0078] Removal rate = (1- C t / C 0)×100%

[0079] Water flux is calculated using the following formula:

[0080] Water flux = V / ( A × t )

[0081] In the formula, V The volume of the pollutant aqueous solution, A Membrane area, t The time it takes for all the pollutant aqueous solution to pass through the filter membrane.

[0082] Results analysis

[0083] Figure 1 Scanning electron microscope image of the dibasic three-dimensional ordered structure composite membrane prepared in Example 1. As can be seen from the figure, the calcium phosphate material presents a vertical array structure of nanowires, and the polydopamine material presents a granular structure. The polydopamine particles are attached to the calcium phosphate array to form a unique dibasic three-dimensional ordered structure composite membrane, which significantly improves the dispersibility of the polydopamine particles.

[0084] Figure 2 Scanning electron microscope image of the planar disordered structure composite membrane prepared in Comparative Example 3. As can be seen from the figure, in the absence of a calcium phosphate array, the polydopamine particles are directly attached to the base membrane fibers, and the agglomeration is more serious, resulting in a large reduction in adsorption sites.

[0085] Table 1 is a comparison of the removal rates of cationic dyes (methylene blue) by the dibasic three-dimensional ordered structure composite membranes prepared in Examples 1-7. The preparation schemes provided in Examples 1-7 are synthetic parameters for control. As can be seen from Table 1, the dibasic three-dimensional ordered structure composite membranes prepared in Examples 1-7 all exhibit high pollutant removal rates. Among them, the preparation scheme and synthetic parameters provided in Example 1 are more optimal, so they are compared with the samples prepared in Comparative Examples.

[0086] Table 2 is a comparison of the removal rates of anionic dyes (congo red) and cationic dyes (methylene blue) and water flux data of the dibasic three-dimensional ordered structure composite membranes prepared in Example 1 and the composite membranes prepared in Comparative Examples 1, 2, and 3. As can be seen from Table 2, the removal rate of pollutants by the dibasic three-dimensional ordered structure composite membrane prepared in Example 1 is much higher than that of the comparative examples, and the water flux remains > 380 L m −2 h −1 . The reason for the significant improvement in removal rate is the synergy of the calcium phosphate and polydopamine dibasic elements, as well as the rich adsorption sites of the well-dispersed polydopamine particles. The reason for the stable water flux is that the calcium phosphate array is grown on the base membrane fibers and arranged vertically upward, without damaging the pore structure of the base membrane, so the water flow can quickly pass through the filter membrane.

[0087] Table 1: Removal rate of organic pollutants methylene blue by the composite membrane described in the examples

[0088]

[0089] Table 2: Removal rate of organic pollutants and water flux of the composite membrane described in the examples and comparative examples

[0090]

[0091] The above merely describes preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the present application should be included in the scope of the present application.

Claims

1. A method for preparing a bi-radical three-dimensionally ordered structure composite film, characterized in that, The preparation method comprises the following steps: (1) mixing oleic acid and ethanol, stirring uniformly, adding calcium salt aqueous solution, sodium hydroxide aqueous solution, phosphate aqueous solution, stirring uniformly, transferring to a Teflon reaction kettle, putting into a filter membrane to react, washing and drying the obtained composite filter membrane to obtain a nanowire-shaped calcium phosphate composite membrane; (2) mixing copper sulfate aqueous solution, dopamine hydrochloride aqueous solution and tris(hydroxymethyl)aminomethane aqueous solution, adding hydrogen peroxide to prepare an aqueous solution 1; (3) soaking the nanowire-shaped calcium phosphate composite membrane obtained in step (1) in the aqueous solution 1 obtained in step (2) for a period of time, washing and drying, repeating the above process to control the loading amount of polydopamine, and finally washing and drying the obtained composite membrane to obtain a diunit bimorph three-dimensional ordered structure composite membrane.

2. The method of claim 1, wherein the method is characterized by: In step (1), the volume ratio of the oleic acid and ethanol to the total volume of the three aqueous solutions of calcium salt aqueous solution, sodium hydroxide aqueous solution and phosphate aqueous solution is 60-75:100-115:290-310.

3. The method of claim 1, wherein the method further comprises the step of: In step (1), the calcium salt is one or both of calcium chloride and calcium nitrate, the concentration of the calcium salt aqueous solution is 1.3-1.7% w / v, the concentration of the sodium hydroxide aqueous solution is 3-7% w / v, the phosphate is one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate and sodium pyrophosphate, the concentration of the phosphate aqueous solution is 2.5-3.1% w / v, and the volume ratio of the calcium salt aqueous solution:sodium hydroxide aqueous solution:phosphate aqueous solution is 2:2:

1.

4. The method of claim 1, wherein the method is characterized by: In step (1), the reaction temperature is 150-250°C, and the reaction time is 10-36 hours.

5. The method of claim 1, wherein the method further comprises: In step (1), the filter membrane is one or more of cellulose filter membrane, polytetrafluoroethylene filter membrane, polyether sulfone filter membrane and polyacrylonitrile filter membrane.

6. The method of claim 1, wherein the method further comprises: In step (1), the drying method is one or more of atmospheric environment drying, normal pressure heating drying and vacuum heating drying, and the corresponding drying conditions are room temperature / 2-48 hours, 20-70°C / 1-24 hours, 20-70°C / 50-1000 Pa / 1-24 hours, respectively.

7. The method of claim 1, wherein the method further comprises the step of: In step (2), the concentration of the copper sulfate aqueous solution is 0.05-0.11% w / v, the concentration of the dopamine hydrochloride aqueous solution is 0.1-0.3% w / v, the concentration of the tris(hydroxymethyl)aminomethane aqueous solution is 0.09-0.15% w / v, the volume ratio of hydrogen peroxide to water is 1:4000-6000, and the volume ratio of the copper sulfate aqueous solution:dopamine hydrochloride aqueous solution:tris(hydroxymethyl)aminomethane aqueous solution is 1:2:

2. ​ 8. The method of claim 1, wherein the method further comprises: In step (3), the soaking time is 6-24 hours, and the soaking frequency is 1-5 times.

9. A diunit bimorph three-dimensional ordered structure composite membrane prepared by the method of any one of claims 1-8.

10. Application of the diunit bimorph three-dimensional ordered structure composite membrane of claim 9 in water treatment of organic pollutants.

Images