CN115475539A - MnO 2 Nanowire modified PVDF (polyvinylidene fluoride) film as well as preparation method and application thereof - Google Patents
MnO 2 Nanowire modified PVDF (polyvinylidene fluoride) film as well as preparation method and application thereof Download PDFInfo
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- 239000002070 nanowire Substances 0.000 title claims abstract description 118
- 239000002033 PVDF binder Substances 0.000 title claims abstract description 88
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 239000012528 membrane Substances 0.000 claims abstract description 124
- 239000000243 solution Substances 0.000 claims abstract description 93
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims abstract description 84
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 60
- 229920001661 Chitosan Polymers 0.000 claims abstract description 33
- 239000002243 precursor Substances 0.000 claims abstract description 25
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- 239000011259 mixed solution Substances 0.000 claims abstract description 13
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- 239000010439 graphite Substances 0.000 claims description 26
- 238000006243 chemical reaction Methods 0.000 claims description 18
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 15
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- MCPLVIGCWWTHFH-UHFFFAOYSA-L methyl blue Chemical compound [Na+].[Na+].C1=CC(S(=O)(=O)[O-])=CC=C1NC1=CC=C(C(=C2C=CC(C=C2)=[NH+]C=2C=CC(=CC=2)S([O-])(=O)=O)C=2C=CC(NC=3C=CC(=CC=3)S([O-])(=O)=O)=CC=2)C=C1 MCPLVIGCWWTHFH-UHFFFAOYSA-L 0.000 abstract description 23
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- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 abstract description 9
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
- B01D71/34—Polyvinylidene fluoride
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0079—Manufacture of membranes comprising organic and inorganic components
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/38—Organic compounds containing nitrogen
Abstract
The invention provides MnO 2 A nanowire modified PVDF film, a preparation method and application thereof, belonging to the technical field of film water treatment. By adding MnO 2 Slowly adding the nano-wires into the chitosan solution to form a precursor mixed solution, and filtering the precursor mixed solution by using a PVDF membrane to prepare the MnO 2 Nanowire modified PVDF membranes. Using chitosan and MnO 2 Electrostatic interaction and chemical bond linkage between the nanowires and the PVDF membrane, resulting in MnO 2 The stability of the nanowire modified PVDF film is greatly improved. Prepared MnO 2 Nanowire modified PVDF filmsAfter soaking in deionized water at pH =7, HCl solution at pH =3, and NaOH solution at pH =11 for 7 days and 14 days, there was no significant change in appearance and no significant change in methyl blue retention. With MnO 2 The nano-wire modified PVDF membrane treats methyl blue solution, the retention rate is still high after 10 times of repeated use, and the result shows that MnO is 2 The nanowire modified PVDF film has good reusability. The above properties show that MnO prepared by the present invention 2 The nanowire modified PVDF membrane is expected to be applied to the treatment of industrial wastewater.
Description
Technical Field
The invention belongs to the technical field of membrane method water treatment, and particularly relates to MnO 2 A nanowire modified PVDF film, a preparation method and application thereof.
Background
PVDF membrane is a membrane material widely used in water treatment, and has recently attracted much attention from researchers because of its good chemical stability, thermal stability and excellent mechanical properties. However, the surface of the PVDF membrane has extremely strong hydrophobicity, so that the PVDF membrane is very easy to cause membrane pollution in the actual use process, and the service life of the PVDF membrane is influenced.
One of the main means for solving the membrane pollution problem by functionalizing the surface of the PVDF membrane is to introduce functional groups, including hydrophilic substances, polyelectrolytes, nanoparticles, photocatalysts and the like, into the surface of the PVDF membrane to functionalize the surface of the membrane, so that the modified PVDF membrane has obvious modification effect, strong operability and good use durability, becomes a hotspot of research, and has a lot of research work, such as reports
MnO 2 The nano-wire is an electrochemical material with excellent performance and can be used for catalyzing and degrading organic pollutants in wastewater. Research hopes to reduce MnO 2 The nanowires are loaded on the surface of the PVDF film to obtain MnO 2 Nanowire modified PVDF films. However, due to MnO 2 The combination performance of the nano wire and the PVDF film is poor, and the prepared MnO is subjected to vacuum filtration 2 MnO on product prepared by loading nanowire on surface of PVDF (polyvinylidene fluoride) membrane 2 Nano meterThe thread is easy to fall off and has poor stability.
Disclosure of Invention
Based on the above, the invention provides MnO 2 A preparation method of a nanowire modified PVDF film, which aims at solving the problem of MnO in the prior art 2 The combination performance of the nano wire and the PVDF film is poor, and the product stability is poor.
The invention also provides MnO 2 The application of the nanowire modified PVDF membrane in wastewater treatment.
The technical scheme for solving the technical problems is as follows:
MnO (MnO) 2 The preparation method of the nanowire modified PVDF film comprises the following steps:
s01, obtaining MnO 2 A nanowire;
s02, preparing MnO 2 Nano-wire water dispersion for later use; preparing a modified solution for later use; wherein the modifying solution comprises a chitosan solution;
s03, mnO is added 2 Slowly adding the nanowire water dispersion into the modified solution, and fully mixing to obtain a precursor mixed solution;
s04, filtering the precursor mixed solution by using a PVDF membrane to prepare a composite PVDF membrane;
s05, drying the composite PVDF membrane to obtain MnO 2 Nanowire modified PVDF membranes.
Preferably, the modification solution further comprises a graphite oxide water dispersion liquid, and the graphite oxide water dispersion liquid is prepared by dispersing graphite oxide in water.
Preferably, in step S03, the MnO is added 2 Slowly adding the nanowire water dispersion into the modified solution to ensure that MnO is contained in the precursor solution 2 The mass ratio of the nano-wire to the chitosan is (1-3) to 3.
Preferably, in step S03, the MnO is 2 Slowly adding the nanowire water dispersion into the modified solution to ensure that MnO is contained in the precursor solution 2 The mass ratio of the nanowire to the graphite oxide to the chitosan is (1-3) to 3:0.1.
Preferably, in step S03, the MnO is 2 Slowly adding the nanowire water dispersion into the modified solution to ensure that MnO is contained in the precursor solution 2 The mass ratio of the nanowires to the chitosan to the graphite oxide is 3.
Preferably, in step S04, a pressure difference of 5KPa to 20KPa is maintained between two sides of the PVDF membrane when the precursor mixture is filtered by the PVDF membrane.
Preferably, in step S01, the step of "obtaining MnO 2 The nanowire "comprises the following steps:
KMnO 4 Dissolving the powder in an acetic acid solution, heating to a preset temperature, carrying out heat preservation reaction, and obtaining a reaction solution after the reaction is finished;
filtering the reaction solution, and washing a filter cake for at least one time to obtain wet MnO 2 A nanowire;
the wet MnO 2 Drying the nano wire to prepare MnO 2 A nanowire.
MnO (MnO) 2 Nanowire modified PVDF membranes from MnO as described above 2 The preparation method of the nanowire modified PVDF membrane is obtained.
MnO as above 2 The application of the nanowire modified PVDF membrane in water treatment.
Compared with the prior art, the invention has at least the following advantages:
the invention is realized by adding MnO 2 Slowly adding the nano-wires into the chitosan solution to form a precursor mixed solution, and filtering the precursor mixed solution by using a PVDF membrane to prepare the MnO 2 Nanowire modified PVDF membranes. Using chitosan and MnO 2 Electrostatic interaction and chemical bond linkage between the nanowires and the PVDF membrane, resulting in MnO 2 The stability of the nanowire modified PVDF film is greatly improved. Experiments show that the MnO prepared 2 After the nanowire modified PVDF membrane is soaked in deionized water with pH =7, HCl solution with pH =3 and NaOH solution with pH =11 for 7 days and 14 days, the appearance is not obviously changed, and the methyl blue rejection rate is not obviously changed. With MnO 2 The nano-wire modified PVDF membrane treats methyl blue solution, the retention rate is still high after 10 times of repeated use, and the result shows that MnO is 2 Nanowire modificationThe PVDF film has good reusability. The above properties indicate that MnO was prepared according to the present invention 2 The nanowire modified PVDF membrane is expected to be applied to the treatment of industrial wastewater.
Drawings
FIG. 1 shows MnO prepared in example one 2 And the nanowire modified PVDF membrane has the interception effect on methyl blue after being soaked in solutions with different pH values for 7 days and 14 days.
FIG. 2 shows MnO prepared in example two 2 And the nanowire modified PVDF membrane has the interception effect on methyl blue after being soaked in solutions with different pH values for 7 days and 14 days.
FIG. 3 shows MnO prepared in example two 2 Physical image and SEM photographs of the nanowire-modified PVDF membrane.
FIG. 4 is MnO prepared in example two 2 Water contact angle of nanowire modified PVDF films.
FIG. 5 shows MnO prepared in example two 2 The nanowire modified PVDF membrane has the flux and rejection rate for methyl blue with different concentrations.
FIG. 6 shows MnO prepared in example two 2 And (3) a line graph of the repeatability test of the nano-wire modified PVDF membrane on the methyl blue retention rate.
FIG. 7 is a bar graph of pure water flux for five different composite membranes prepared in one example.
Fig. 8 is a bar graph of flux and rejection for methyl blue solution for five different composite membranes prepared in one example.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The technical solutions of the present invention will be further described below with reference to the following embodiments of the present invention, and the present invention is not limited to the following specific embodiments.
In one embodiment of the invention, a MnO 2 The preparation method of the nanowire modified PVDF film comprises the following steps:
s01, obtaining MnO 2 A nanowire;
s02, preparing MnO 2 Nano-wire water dispersion for later use; preparing a modified solution for later use; wherein the modifying solution comprises a chitosan solution;
s03, mnO is added 2 Slowly adding the nanowire water dispersion into the modified solution, and fully mixing to obtain a precursor mixed solution;
s04, filtering the precursor mixed solution by using a PVDF membrane to prepare a composite PVDF membrane;
s05, drying the composite PVDF membrane to obtain MnO 2 Nanowire modified PVDF membranes.
In one embodiment, mnO is obtained in step S01 2 The method of nanowires comprises the steps of:
mixing KMnO 4 Dissolving the powder in an acetic acid solution, heating to a preset temperature, carrying out heat preservation reaction, and obtaining a reaction solution after the reaction is finished;
filtering the reaction solution, and washing a filter cake for at least one time to obtain wet MnO 2 A nanowire;
the wet MnO 2 Drying the nano wire to prepare MnO 2 A nanowire.
For example, 6g of KMnO is accurately weighed 4 Powdered and dissolved in 100mL of 0.4M CH 3 Stirring the COOH solution at room temperature until the COOH solution is completely dissolved, adding the solution into a polytetrafluoroethylene reaction kettle, and then placing the reaction kettle in an oven to be heated to 140 ℃ for reaction. After the reaction is finished, taking the high-pressure reaction kettle out of the oven, naturally cooling to room temperature, pouring out the obtained product, and obtaining MnO after suction filtration, washing and drying 2 A nanowire.
In one embodiment, step S02, the modified solution is chitosan solution, and MnO is finally prepared 2 The load substances on the nanowire modified PVDF membrane are chitosan and MnO 2 A nanowire. In the use of chitosan and MnO 2 Electrostatic interaction and chemical bond linkage between the nanowires and the PVDF membrane, resulting in MnO 2 The stability of the nanowire modified PVDF film is greatly improved.
However, experiments have shown that when MnO is finally prepared 2 The load substances on the nanowire modified PVDF membrane are only chitosan and MnO 2 When the nano wire is used, the average pure water flux is only 248.5 L.m -2 ·h -1 And the treatment requirement of industrial wastewater cannot be met.
In order to solve the above technical problem, in a preferred embodiment, the modification solution is a mixed solution of a chitosan solution and an aqueous graphite oxide dispersion. Preferably, the mass ratio of chitosan to graphite oxide in the mixed solution is 0.1.
Experiments have shown that when MnO is finally prepared 2 The load substances on the nanowire modified PVDF membrane are chitosan, graphite oxide and MnO 2 When the nano-wire is used, on one hand, the stability of the composite film can be further enhanced through electrostatic interaction and chemical bond linkage between the chitosan and the graphite oxide, and on the other hand, the graphite oxide and MnO are linked 2 The assembly process of the nano-wires constructs a water channel for forming the composite membrane, endows the composite membrane with high water flux, and ensures that the average pure water flux reaches 2507.2 L.m -2 ·h -1 . Moreover, the graphite oxide lamellar structure is beneficial to further improving the rejection rate of the composite membrane.
In some embodiments, in step S03, the MnO is modified 2 Slowly adding the nanowire water dispersion into the modified solution to ensure that MnO is contained in the precursor solution 2 The mass ratio of the nano wire to the chitosan is (1-3) to 1.
In some preferred embodiments, in step S03, the MnO is modified 2 Slowly adding the nanowire water dispersion into the modified solution to ensure that MnO is contained in the precursor solution 2 The mass ratio of the nanowire to the graphite oxide to the chitosan is (1-3) to 3:0.1. Most preferably, mnO 2 The mass ratio of the nanowire to the graphite oxide to the chitosan is 3.
Preferably, in step S04, the pressure difference between the two sides of the PVDF membrane is maintained at 5KPa to 20KPa during the filtration of the precursor mixture using the PVDF membrane.
In yet another embodiment of the present invention, a MnO 2 Nanowire modified PVDF films made from MnO as described above 2 The preparation method of the nanowire modified PVDF membrane is obtained.
In yet another embodiment of the inventionIn the above-described mode, a MnO 2 Use of nanowire modified PVDF membranes in water treatment, in particular MnO as described above 2 The application of the nanowire modified PVDF membrane in industrial sewage treatment.
The technical scheme and technical effects of the present invention are further described below by specific experimental examples.
1. MnO 2 Preparation of nanowire modified PVDF (polyvinylidene fluoride) film
MnO 2 Preparing the nano wire: accurately weighing quantitative KMnO 4 Dissolving the powder in acetic acid solution, stirring at room temperature until the powder is completely dissolved, then placing the powder in an oven, heating to 120 ℃, and reacting at constant temperature for 12 hours. After the reaction is completed, cooling the reaction liquid to room temperature, then carrying out suction filtration and washing on the obtained product by using a vacuum pump, then alternately washing the product for a plurality of times by using deionized water and absolute ethyl alcohol, then placing the solid product obtained after suction filtration in a drying oven at the temperature of 60 ℃ for drying for 12 hours at constant temperature, and finally obtaining alpha-MnO 2 A nanowire.
MnO 2 Preparing a nanowire water dispersion liquid: adding manganese dioxide nanowires into deionized water, performing ultrasonic dispersion, and preparing MnO of 1mg/ml 2 A nanowire aqueous dispersion.
Preparation of chitosan solution: chitosan was added to a 1 wt% dilute acetic acid solution, and the mixture was sufficiently stirred to dissolve chitosan, thereby preparing a 1mg/ml chitosan solution.
Preparing a graphite oxide water dispersion liquid: adding graphite oxide into deionized water, and performing ultrasonic dispersion to form 0.1mg/ml graphite oxide water dispersion.
Comparative example 1
MnO was added under a pressure of about 0.09MPa using vacuum filtration 2 And loading the nanowire aqueous dispersion on a commercial PVDF upper membrane to form a composite membrane A, and drying the composite membrane A in an oven at 60 ℃ for 4h.
Experimental example I
Adding 3ml of MnO 2 Slowly adding the nanowire water dispersion into 3ml of chitosan solution, and carrying out ultrasonic treatment for 30min to obtain a precursor solution. Then, using vacuum filtration, under a pressure of about 0.09MPa, the above was performedAnd loading the precursor solution on a commercial PVDF upper membrane to obtain a composite membrane B, and drying the composite membrane B in an oven at 60 ℃ for 4 hours.
Experimental example two
3ml of chitosan solution was added to 1ml of aqueous graphite oxide dispersion, after ultrasonic dispersion, followed by slow 3ml of MnO 2 Dispersing the nanowire in water, and treating the nanowire for 30min by ultrasonic waves to obtain a precursor solution. Then, using vacuum filtration, the above precursor solution was loaded onto a commercial PVDF upper membrane under a pressure of about 0.09MPa to form composite membrane C, which was dried in an oven at 60 ℃ for 4h.
2. MnO 2 Performance testing of nanowire modified PVDF films
(1) Stability test
And respectively placing the composite membrane A, the composite membrane B and the composite membrane C in deionized water with the pH =7, an HCl solution with the pH =3 and a NaOH solution with the pH =11, soaking for 7 days and 14 days, washing the composite membrane with the deionized water, placing the composite membrane in a 60-degree oven, drying for 4 hours, observing the surface defects of the composite membrane, and testing the rejection rate of the composite membrane to a 40mg/L methyl blue solution.
Please refer to Table 1, the composite membrane A and MnO after soaking 2 The nanowires cannot be stably loaded and are easy to fall off. No matter the composite membrane is soaked in deionized water or acid or alkali, the composite membrane B and the composite membrane C are stably loaded, and no obvious defect exists on the surface.
Referring to fig. 1 and fig. 2, the retention rate of the composite films B and C soaked in different media to the 40mg/L methyl blue solution is maintained above 90% and is substantially maintained.
Referring to fig. 3, it can be seen from the physical diagram that the material on the composite film C is uniformly distributed and the surface has no obvious structural damage. By observing the surface structure of the composite film C through SEM, the existence of graphite oxide sheets and a large amount of alpha-MnO on the surface of the composite film C can be seen 2 The nanowires are uniformly dispersed.
TABLE 1 MnO 2 Nanowire modified PVDF film stability test results
"/" indicates not tested
(2) Measurement of Water contact Angle and pure Water flux
Referring to fig. 4, the water contact angles of the composite films B and C were measured by a water contact angle tester, and the results showed that the average water contact angle of the composite film B was 32.5 ° and the average water contact angle of the composite film C was 24.8 °.
And (3) carrying out vacuum filtration under the pressure of about 0.09Mpa, carrying out vacuum filtration on the membrane for 30min before a filtration experiment to enable the pressure value to reach 0.09MPa, taking 50ml of pure water, respectively enabling the pure water to pass through the composite membrane B and the composite membrane C under the vacuum filtration condition, and calculating the passing time of the solution so as to calculate the flux of the membrane. The results show that the average pure water flux of the composite membrane B is 248.5 L.m -2 ·h -1 The average pure water flux of the composite membrane C reaches 2507.2 L.m -2 ·h -1 。
(3) Flux and rejection testing for different concentrations of methyl blue
Vacuum filtration is carried out under the pressure of about 0.09MPa, and before the filtration experiment, the membrane is subjected to vacuum filtration for 30min to ensure that the pressure value reaches 0.09MPa. Then 50ml of dye solutions with different concentrations are taken and 2ml of 30% H are respectively added 2 O 2 And respectively enabling the solution to pass through the composite membrane B and the composite membrane C under the vacuum filtration condition, calculating the passing time of the solution, and carrying out an absorbance test on the filtrate by using a spectrophotometer so as to calculate the flux and the rejection rate of the composite membrane B and the composite membrane C.
The results show that as the concentration of the methyl blue solution is increased from 20mg/L to 100mg/L, the rejection rate of the composite membrane B is kept above 85%, and the rejection rate of the composite membrane C is kept above 96%. When the concentration is increased, the dye molecules in the solution are increased, and the flux of the dye is obviously reduced compared with the flux of the dye with low concentration before. The flux of the methyl blue solution of the composite membrane B is 62.4 L.m -2 ·h -1 -102.0L·m -2 ·h -1 . Referring to fig. 5, the effect of the concentration of the dye solution on the performance of composite membrane C is shown. It can be seen that the composite film increases with the concentration of methyl blue solution from 20mg/L to 100mg/LThe retention rate of C is kept above 96%, when the concentration is increased, the dye molecules in the solution are increased, the flux of the dye is obviously reduced compared with the flux of the dye with low concentration, and the flux of the methyl blue solution of the composite membrane C is 398.5 L.m -2 ·h -1 -1025.8L·m -2 ·h -1 。
(4) Reusability test
A 30mg/L solution of methyl blue was selected as the simulated wastewater, and the next filtration was started immediately after the first filtration without any treatment of the membrane, and the membrane was cycled ten times to evaluate its reusability by retention rate.
After 10 times of repeated use, the retention rate of the composite film B on the methyl blue solution is still as high as 80.62 percent. Referring to fig. 6, after 10 times of repeated use, the rejection rate of the composite film C to the methyl blue solution is maintained at 86.74%, which indicates that the composite films B and C have good reusability.
(5) Exploring different contents of alpha-MnO 2 Influence of nano-wire on methyl blue solution retention rate and flux of composite membrane
Composite membranes were prepared according to the formulation shown in table 2, with reference to example two.
TABLE 2 preparation of composite membranes
| M-1 | M-2 | M-3 | M-4 | M-5 | |
| Graphite oxide aqueous dispersion/ |
1 | 1 | 1 | 1 | 1 |
| Chitosan solution/ |
0 | 3 | 3 | 3 | 3 |
| MnO 2 Nanowire Water Dispersion/ |
0 | 0 | 1 | 2 | 3 |
The pure water flux of each composite membrane was tested and the test results are shown in table 3.
Vacuum filtration is carried out under the pressure of about 0.09MPa, and before the filtration experiment, the membrane is subjected to vacuum filtration for 30min to ensure that the pressure value reaches 0.09MPa. Then 50ml of dye solution with different concentrations are taken and 2ml of 30% H is added respectively 2 O 2 Respectively passing through M-1, M-2, M-3, M-4 and M-5 under a vacuum filtration strip, calculating the passing time of the solution, and performing an absorbance test on the filtrate by using a spectrophotometer to calculate the flux and the rejection rate of each composite membrane. The test results are shown in table 3.
TABLE 3 different amounts of MnO 2 Influence of nano-wire on methyl blue solution retention rate and flux of composite membrane
Referring to FIGS. 7 and 8 together, the pure water flux of the graphite oxide film is 574.42L · m because the graphite oxide film contains a large amount of hydrophilic clusters on the surface thereof -2 ·h -1 . Due to the hydrophobicity of the Chitosan (CS), the pure water flux of the composite membrane M-2 is reduced to 214.27 L.m -2 ·h -1 . With the addition of manganese dioxide, it can be found that the pure water flux of the composite membrane M-3, the composite membrane M-4 and the composite membrane M-5 is significantly increased. Wherein the highest pure water flux of the composite membrane M-5 is 2507.19 L.m -2 ·h -1 . The flux and retention rate of the composite membrane M-1 and the composite membrane M-2 to the methyl blue solution are both lower. When MnO is added 2 Then, the flux and the retention rate are both obviously improved, and the flux and the retention rate of the composite membrane M-5 to the methyl blue solution are 952.70 L.m -2 ·h -1 And 98.19%.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. MnO (MnO) 2 The preparation method of the nanowire modified PVDF membrane is characterized by comprising the following steps:
s01, obtaining MnO 2 A nanowire;
s02, preparing MnO 2 Nano-wire water dispersion for later use; preparing a modified solution for later use; wherein the modifying solution comprises a chitosan solution;
s03, adding the MnO 2 Slowly adding the nanowire water dispersion into the modified solution, and fully mixing to obtain a precursor mixed solution;
s04, filtering the precursor mixed solution by using a PVDF membrane to prepare a composite PVDF membrane;
s05, drying the composite PVDF membrane to obtain MnO 2 Nanowire modified PVDF membranes.
2. The MnO of claim 1 2 The preparation method of the nanowire modified PVDF membrane is characterized in that the modified solution further comprises a graphite oxide water dispersion liquid, and the graphite oxide water dispersion liquid is prepared by dispersing graphite oxide in water.
3. The MnO of claim 1 2 The preparation method of the nanowire modified PVDF membrane is characterized in that in the step S03, mnO is added 2 Slowly adding the nanowire water dispersion into the modified solution to ensure that MnO is contained in the precursor solution 2 The mass ratio of the nano wire to the chitosan is (1-3) to 3.
4. The MnO of claim 2 2 A method for producing a nanowire-modified PVDF film, characterized in that, in step S03, the MnO is treated 2 Slowly adding the nanowire water dispersion into the modified solution to ensure that MnO is contained in the precursor solution 2 The mass ratio of the nanowire to the graphite oxide to the chitosan is (1-3) to 0.1.
5. The MnO of claim 3 2 The preparation method of the nanowire modified PVDF membrane is characterized in that in the step S03, mnO is added 2 Slowly adding the nanowire water dispersion into the modified solution to ensure that MnO is contained in the precursor solution 2 The mass ratio of the nanowires to the chitosan to the graphite oxide is 3.
6. The MnO of claim 1 2 The preparation method of the nanowire modified PVDF membrane is characterized in that in the step S04,and when the precursor mixed solution is filtered by the PVDF membrane, the pressure difference between two sides of the PVDF membrane is kept between 5KPa and 20 KPa.
7. The MnO of any of claims 1-6 2 The preparation method of the nanowire modified PVDF membrane is characterized in that in the step S01, mnO is obtained 2 The nanowire "comprises the following steps:
KMnO 4 Dissolving powder in an acetic acid solution, heating to a preset temperature, carrying out heat preservation reaction, and obtaining a reaction solution after the reaction is finished;
filtering the reaction solution, and washing a filter cake for at least one time to obtain wet MnO 2 A nanowire;
the wet MnO 2 Drying the nano wire to prepare MnO 2 A nanowire.
8. MnO (MnO) 2 Nanowire-modified PVDF membrane, characterized by the MnO according to any of claims 1 to 7 2 The preparation method of the nanowire modified PVDF membrane is obtained.
9. The MnO of claim 8 2 The application of the nanowire modified PVDF membrane in water treatment.
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