CN113304622A - POSS/PVDF composite membrane with hydrophobic surface, preparation method and application thereof - Google Patents
POSS/PVDF composite membrane with hydrophobic surface, preparation method and application thereof Download PDFInfo
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Abstract
The disclosure provides a preparation method and application of a POSS/PVDF composite membrane with a surface, wherein the preparation method of the POSS/PVDF composite membrane with the hydrophobic surface comprises the following steps: performing alkali liquor treatment on the polyvinylidene fluoride membrane by using alkali liquor to obtain an alkali-treated polyvinylidene fluoride membrane; dissolving 3-mercaptopropyltriethoxysilane in ethanol to obtain a modified solution; then, modifying the alkali-treated polyvinylidene fluoride membrane by using the modifying liquid to obtain a modified polyvinylidene fluoride membrane; dissolving octavinyl polyhedral oligomeric silsesquioxane in dichloromethane to obtain a solution, and then adding 2-hydroxy-2-methyl propiophenone into the solution to obtain sol; and immersing the modified polyvinylidene fluoride membrane into the sol, and irradiating by adopting an ultraviolet lamp to prepare the POSS/PVDF composite membrane.
Description
Technical Field
The disclosure relates to the technical field of membrane distillation and water treatment, in particular to a POSS/PVDF composite membrane with a hydrophobic surface, a preparation method and application thereof.
Background
The membrane distillation technology is a new liquid separation technology combining the traditional distillation technology and the membrane separation technology. The membrane distillation is a membrane process with phase change, the working principle of the membrane distillation is a membrane distillation process, water molecules of liquid at a hot side are evaporated and vaporized and pass through micropores of a hydrophobic membrane, solutes such as non-volatile ions and molecules in a water phase cannot permeate the hydrophobic membrane, and heat and mass transfer is carried out simultaneously, so that the purposes of solution separation, concentration or purification are realized.
Membrane distillation can generally be operated at atmospheric pressure and at a lower operating temperature, and can utilize cheap energy sources such as geothermal energy, solar energy, hot springs, industrial wastewater waste heat and the like, so that the cost is relatively lower compared with conventional distillation, ultrafiltration, nanofiltration and reverse osmosis. In addition, because only water vapor passes through the membrane pores in the membrane distillation process, the retention rate of non-volatile solutes such as ions and molecules in the original solution can reach 100% theoretically, so the membrane distillation is widely concerned and researched in the treatment of high-salinity and high-organic matter wastewater and wastewater containing radioactivity.
The membrane for membrane distillation is required to have the characteristics of hydrophobicity, low heat conductivity coefficient, thermal stability, chemical stability, strong pollution resistance and the like. However, most of hydrophobic membranes obtained by the existing membrane preparation method have the problems of low porosity, low membrane flux, easy membrane pore wetting and the like, and the development and application of the membrane distillation technology are limited. Therefore, the preparation of the membrane distillation membrane with excellent performances such as high porosity, high flux, super-hydrophobicity and the like is particularly important for effectively improving the anti-wettability and the service life of the membrane, and is one of the key technologies for judging whether the membrane distillation technology can be applied in large-scale industrialization in the future.
The super-hydrophobic surface generally refers to a surface with a contact angle with water of more than 150 degrees and a rolling angle of less than 10 degrees, and has various unique surface properties of self-cleaning, water resistance, ice resistance, oxidation resistance, drag reduction and the like. The preparation of the super-hydrophobic surface mainly comprises the following two ways: constructing a multi-layer micro/nano rough surface, or modifying a low surface energy substance on the surface with a certain roughness. In recent years, various methods of structuring a superhydrophobic surface have been reported, such as a sol-gel method, a template method, an electrospinning method, a plasma treatment method, a chemical vapor deposition method, and the like. However, the above-mentioned methods are difficult to be applied industrially on a large scale due to complicated steps, high technical costs or only a small sample.
Disclosure of Invention
Technical problem to be solved
In view of the above technical problems, the present disclosure provides a POSS/PVDF composite membrane having a hydrophobic surface, a preparation method and applications thereof, in order to at least partially solve one of the above technical problems.
(II) technical scheme
In order to solve the technical problem, the technical scheme of the disclosure is as follows:
as one aspect of the present disclosure, there is provided a method for preparing a POSS/PVDF composite membrane having a hydrophobic surface, comprising:
performing alkali liquor treatment on the polyvinylidene fluoride membrane by using alkali liquor to obtain an alkali-treated polyvinylidene fluoride membrane;
dissolving 3-mercaptopropyltriethoxysilane in ethanol to obtain a modified solution; then, modifying the alkali-treated polyvinylidene fluoride membrane by using the modifying liquid to obtain a modified polyvinylidene fluoride membrane;
dissolving octavinyl polyhedral oligomeric silsesquioxane in dichloromethane to obtain a solution, and then adding 2-hydroxy-2-methyl propiophenone into the solution to obtain sol;
and immersing the modified polyvinylidene fluoride membrane into the sol, and irradiating by adopting an ultraviolet lamp to prepare the POSS/PVDF composite membrane.
According to an embodiment of the present disclosure, the alkali liquor treatment of the polyvinylidene fluoride membrane with alkali liquor comprises:
soaking the polyvinylidene fluoride membrane in the alkali liquor for 2-10h at the temperature of 20-60 ℃, and then drying at the temperature of 60-100 ℃ to obtain the alkali-treated polyvinylidene fluoride membrane.
According to an embodiment of the present disclosure, wherein the alkali solution is a sodium hydroxide solution;
the concentration of the sodium hydroxide solution is 2-6 mol.L-1。
According to the embodiment of the disclosure, the modifying treatment of the alkali-treated polyvinylidene fluoride membrane by using the modifying solution to obtain the modified polyvinylidene fluoride membrane comprises,
and soaking the alkali-treated polyvinylidene fluoride membrane in the modification solution for 2-10h at the temperature of 20-60 ℃, and then drying at the temperature of 60-100 ℃ to obtain the modified polyvinylidene fluoride membrane.
According to the embodiment of the disclosure, the concentration of the modifying solution is 0.1-0.5 mol.L-1。
According to an embodiment of the present disclosure, the method for preparing the sol comprises the steps of dissolving octavinyl polyhedral oligomeric silsesquioxane in dichloromethane to obtain a solution, adding 2-hydroxy-2-methyl propiophenone into the solution to obtain the sol,
adding the octavinyl polyhedral oligomeric silsesquioxane into the dichloromethane, and stirring at the rotating speed of 100-500r/min for 2-10 h; then, ultrasonically dispersing for 2-10h at 20-40 ℃ to dissolve the octavinyl cage-type silsesquioxane to obtain the solution; adding the 2-hydroxy-2-methyl propiophenone into the solution, and stirring at the rotating speed of 100-500r/min for 2-10h to obtain the sol.
According to the embodiment of the disclosure, the weight fraction of the octavinyl cage-type silsesquioxane in the solution is 1-5%;
the mass ratio of the octavinyl cage-type silsesquioxane to the 2-hydroxy-2-methyl propiophenone is 1: 5-20.
According to the embodiment of the disclosure, the irradiation power of the ultraviolet lamp is 250W, and the irradiation time is 20-100 min;
the distance between the ultraviolet lamp and the modified polyvinylidene fluoride membrane is 20-100 cm.
As another aspect of the disclosure, a POSS/PVDF composite membrane obtained by the preparation method is provided.
As a third aspect of the present disclosure, there is provided a use of a POSS/PVDF composite membrane in membrane distillation.
(III) advantageous effects
According to the preparation method provided by the disclosure, the click reaction is initiated by ultraviolet irradiation, and the OVPOSS is grafted on the surface of the PVDF membrane, so that not only is the roughness of the membrane surface increased, but also the surface energy of the membrane is reduced, and the surface of the prepared POSS/PVDF composite membrane is super-hydrophobic.
The preparation method of the POSS/PVDF composite membrane provided by the disclosure has the advantages of simple process, easily controllable process and convenience for industrial application; in addition, the preparation method provided by the disclosure has the advantages of easily obtained raw materials, simple equipment, no need of expensive treatment equipment and low preparation cost; in addition, the preparation method provided by the disclosure has the advantages of high efficiency, rapidness, no fluorine solvent, environmental friendliness, wide application and the like.
The POSS/PVDF composite membrane prepared by the method provided by the disclosure has good anti-pollution and anti-wetting characteristics on the premise of ensuring flux, greatly prolongs the service life of the membrane, and promotes the industrial application of the membrane distillation technology.
Drawings
FIG. 1 is a scanning electron micrograph and contact angle schematic of a POSS/PVDF composite membrane prepared in example 1 of the present disclosure;
FIG. 2 is a graph of the anti-fouling test of a POSS/PVDF composite membrane prepared in example 1 of the present disclosure and a commercial PVDF membrane;
FIG. 3 is a graph of the anti-wetting test of POSS/PVDF composite membranes prepared in example 1 of the present disclosure versus commercial PVDF membranes.
Detailed Description
For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
In the following examples of the present invention,
POSS is an abbreviation for cage polysilsesquioxane;
OVPOSS is an abbreviation for octavinyl cage silsesquioxane;
PVDF is an abbreviation for polyvinylidene fluoride;
MPTES is an abbreviation for 3-mercaptopropyltriethoxysilane;
HMPF is an abbreviation for 2-hydroxy-2-methylpropiophenone;
DCM is an abbreviation for dichloromethane.
According to an embodiment of the present disclosure, there is provided a method for preparing a POSS/PVDF composite membrane having a hydrophobic surface, including:
performing alkali liquor treatment on the polyvinylidene fluoride membrane by using alkali liquor to obtain an alkali-treated polyvinylidene fluoride membrane;
dissolving 3-mercaptopropyltriethoxysilane in ethanol to obtain a modified solution; then, modifying the alkali-treated polyvinylidene fluoride membrane by using a modifying solution to obtain a modified polyvinylidene fluoride membrane;
dissolving octavinyl polyhedral oligomeric silsesquioxane in dichloromethane to obtain a solution, and then adding 2-hydroxy-2-methyl propiophenone into the solution to obtain sol;
and (3) soaking the modified polyvinylidene fluoride membrane into the sol, and irradiating by adopting an ultraviolet lamp to prepare the POSS/PVDF composite membrane.
According to the preparation method provided by the disclosure, the click reaction is initiated by ultraviolet irradiation, and the OVPOSS is grafted on the surface of the PVDF membrane, so that not only is the roughness of the membrane surface increased, but also the surface energy of the membrane is reduced, and the surface of the prepared POSS/PVDF composite membrane is super-hydrophobic.
The preparation method of the POSS/PVDF composite membrane provided by the disclosure has the advantages of simple process, easily controllable process and convenience for industrial application; in addition, the preparation method provided by the disclosure has the advantages of easily obtained raw materials, simple equipment, no need of expensive treatment equipment and low preparation cost; in addition, the preparation method provided by the disclosure has the advantages of high efficiency, rapidness, no fluorine solvent, environmental friendliness, wide application and the like.
The POSS/PVDF composite membrane prepared by the method provided by the disclosure has good anti-pollution and anti-wetting characteristics on the premise of ensuring flux, greatly prolongs the service life of the membrane, and promotes the industrial application of the membrane distillation technology.
According to the embodiment of the disclosure, the polyvinylidene fluoride membrane is subjected to alkali liquor treatment by adopting alkali liquor, and the alkali liquor treatment comprises the following steps: soaking the polyvinylidene fluoride membrane in alkali liquor for 2-10h at the temperature of 20-60 ℃, and then drying at the temperature of 60-100 ℃ to obtain the alkali-treated polyvinylidene fluoride membrane.
According to an embodiment of the present disclosure, wherein the lye is a sodium hydroxide solution.
According to an embodiment of the present disclosure, the concentration of the sodium hydroxide solution is 2-6 mol.L-1。
According to embodiments of the present disclosure, for example, the concentration of the sodium hydroxide solution may be 2mol · L-1、3mol·L-1、4mol·L-1、5mol·L-1、6mol·L-1And so on.
According to the embodiment of the disclosure, the alkali-treated polyvinylidene fluoride membrane is subjected to modification treatment by using a modification solution to obtain a modified polyvinylidene fluoride membrane, which comprises the following steps: soaking the alkali-treated polyvinylidene fluoride membrane in the modifying solution for 2-10h at the temperature of 20-60 ℃, and then drying at the temperature of 60-100 ℃ to obtain the modified polyvinylidene fluoride membrane.
According to the embodiment of the disclosure, the concentration of the modifying solution is 0.1-0.5 mol.L-1。
According to embodiments of the present disclosure, for example, the concentration of the modifying solution may be 0.1mol · L-1、0.2mol·L-1、0.3mol·L-1、0.4mol·L-1、0.5mol·L-1And so on.
According to an embodiment of the present disclosure, in which octavinyl polyhedral oligomeric silsesquioxane is dissolved in dichloromethane to obtain a solution, and then 2-hydroxy-2-methyl propiophenone is added to the solution to obtain a sol, comprising: adding octavinyl polyhedral oligomeric silsesquioxane into dichloromethane, and stirring at the rotating speed of 100-500r/min for 2-10 h; then, ultrasonically dispersing for 2-10h at 20-40 ℃ to dissolve the octavinyl cage type silsesquioxane to obtain a solution; adding 2-hydroxy-2-methyl propiophenone into the solution, and stirring at the rotating speed of 100-500r/min for 2-10h to obtain sol.
According to the embodiment of the disclosure, the weight fraction of the octavinyl cage-type silsesquioxane in the solution is 1-5%.
For example, the mass fraction of octavinyl cage silsesquioxane in solution may be 1%, 2%, 3%, 4%, 5%, etc., in accordance with embodiments of the present disclosure.
According to the embodiment of the disclosure, the mass ratio of the octavinyl polyhedral oligomeric silsesquioxane to the 2-hydroxy-2-methyl propiophenone is 1: 5-20.
According to embodiments of the present disclosure, for example, the mass ratio of octavinyl polyhedral oligomeric silsesquioxane to 2-hydroxy-2-methylpropiophenone is 1: 5, 1: 8, 1: 10, 1: 15, 1: 20, and so forth.
According to the embodiment of the disclosure, the irradiation power of the ultraviolet lamp is 250W, and the irradiation time is 20-100 min.
According to embodiments of the present disclosure, the ultraviolet lamp is at a distance of 20-100cm from the modified polyvinylidene fluoride membrane.
According to an embodiment of the present disclosure, the uv lamp spectral energy distribution is centered at 365 nm.
According to the embodiment of the disclosure, after the ultraviolet lamp irradiation is finished, ethanol is washed for 1min and dried at 60 ℃ to obtain the POSS/PVDF composite membrane.
According to the embodiment of the disclosure, the POSS/PVDF composite membrane is obtained by the preparation method.
According to an embodiment of the present disclosure, there is provided a use of a POSS/PVDF composite membrane in membrane distillation.
The disclosure is further illustrated by the following specific examples:
example 1
A preparation method of POSS/PVDF composite membrane with hydrophobic surface comprises,
(1) alkali treatmentPreparation of PVDF membrane: immersing PVDF film in 2 mol. L-1And treating the PVDF membrane at the temperature of 20 ℃ for 2 hours to introduce hydroxyl groups into the surface of the PVDF membrane, thereby obtaining the alkali-treated PVDF membrane.
(2) Preparation of modified PVDF membrane: dissolving MPTES in ethanol, and stirring to obtain modified solution with concentration of 0.1mol · L-1(ii) a And (2) soaking the alkali-treated PVDF membrane obtained in the step (1) in a modifying solution at 20 ℃ for 2h, taking out, washing with ethanol, and drying at 60 ℃ for 2h to obtain the modified polyvinylidene fluoride membrane.
(3) Preparing sol: adding OVPOSS into DMC, magnetically stirring for 2h at the rotating speed of 100r/min, then performing ultrasonic dispersion for 2h at the temperature of 20 ℃, and fully dissolving the OVPOSS in the DMC to obtain an OVPOSS/DMC solution with the mass fraction of 1%; and then, adding HMPF (high molecular weight polyethylene) serving as a photoinitiator into the OVPOSS/DMC solution, and magnetically stirring for 2 hours at the rotating speed of 100r/min to obtain sol, wherein the mass ratio of the OVPOSS to the HMPF is 1: 5.
(4) Preparing an OVPOSS/PVDF composite membrane: immersing the modified PVDF membrane in the step (2) into the sol in the step (3), irradiating for 20min at a position 20cm away from an ultraviolet lamp, and initiating a mercapto-vinyl click reaction through ultraviolet irradiation to graft OVPOSS on the surface of the modified PVDF membrane; and then, taking the grafted PVDF membrane out of the sol, washing the PVDF membrane for 1min by using ethanol, and drying the PVDF membrane at the temperature of 60 ℃ to obtain the OVPOSS/PVDF composite membrane.
OVPOSS/PVDF composite membranes from example 1 were tested:
the contact angle and the rolling angle of the OVPOSS/PVDF composite film in example 1 were measured, and the results are shown in fig. 1.
FIG. 1 is a scanning electron micrograph and contact angle schematic of an OVPOSS/PVDF composite membrane prepared in example 1 of the present disclosure.
As can be seen from FIG. 1, the membrane water contact angle of the OVPOSS/PVDF composite membrane in example 1 is 152.5 degrees, and the rolling angle is 9.8 degrees, which indicates that the OVPOSS/PVDF composite membrane has better hydrophobicity.
② the modified super-hydrophobic membrane (i.e. OVPOSS/PVDF composite membrane) prepared in the example 1 is subjected to anti-fouling performance test:
the modified superhydrophobic membrane and the PVDF membrane were subjected to a direct contact membrane distillation experiment (DCMD) for 150 hours using a mixed solution of 100g/L sodium chloride, 2.22g/L calcium chloride and 50mg/L humic acid as a feed solution, and the flux and conductivity of the DCMD were varied with time as shown in FIG. 2.
Fig. 2 is a graph of the anti-fouling test of the modified superhydrophobic film prepared in example 1 of the present disclosure and a PVDF film.
As can be seen from fig. 2, the flux of the PVDF membrane is higher than that of the modified superhydrophobic membrane at the initial stage. However, in the running process of the DCMD experiment, the flux of the PVDF membrane is obviously reduced, meanwhile, the modified super-hydrophobic membrane shows relatively stable flux, and after 20 hours of DCMD anti-pollution test, the flux of the modified super-hydrophobic membrane is greater than that of the PVDF membrane, which shows that the PVDF membrane is poor in hydrophobicity and is more easily polluted. Thus, the modified superhydrophobic film prepared in the example 1 has good antifouling performance.
In the aspect of conductivity, the conductivities of the PVDF membrane and the modified super-hydrophobic membrane are not obviously changed in the whole experimental process, but the conductivity curve of the modified super-hydrophobic membrane is relatively stable, and the conductivity of the modified super-hydrophobic membrane is always 5 mu S-cm-1The conductivity of the resulting mixture was closer to that of pure water (1.54. mu.S cm)-1) The salt rejection rate of the modified super-hydrophobic membrane is always over 99.99 percent. The conductivity of the PVDF membrane is slightly increased compared with that of the modified super-hydrophobic membrane.
③ the modified superhydrophobic film prepared in example 1 (i.e., OVPOSS/PVDF composite film) was subjected to anti-wetting property test:
the modified superhydrophobic membrane and the PVDF membrane were subjected to a direct contact membrane distillation experiment (DCMD) for 2h using sodium chloride solutions containing sodium dodecyl sulfate at different concentrations as a feed solution, and the change in flux and conductivity over time of the DCMD is shown in fig. 3.
The concentration of Sodium Dodecyl Sulfate (SDS) is 0.1mmol/L, 0.2mmol/L and 0.3mmol/L respectively; the concentration of sodium chloride was 35 g/L.
Fig. 3 is a graph of the anti-wetting test of the modified superhydrophobic PVDF membrane prepared in example 1 of the disclosure and a PVDF membrane that has not been treated by the method of the disclosure.
FIG. 3(a) is a graph of flux and conductivity versus time for an unmodified PVDF membrane;
fig. 3(b) is a graph of flux and conductivity versus time for the modified superhydrophobic membrane prepared in example 1.
As can be seen from FIG. 3(b), the flux and conductivity curves of the modified superhydrophobic membrane at SDS concentrations of 0.1mmol/L and 0.2mmol/L are lower and maintained in a more stable state. The stable super-hydrophobic layer is formed on the surface of the modified hydrophobic membrane, so that liquid is effectively prevented from wetting membrane pores, and better membrane distillation flux and lower conductivity can be maintained.
As can be seen from FIG. 3(a), the PVDF membrane has a significant increase in flux at SDS concentrations of 0.1mmol/L, 0.2mmol/L and 0.3mmol/L, and the conductivity rapidly increases as the SDS concentration continues to increase to 0.3mmol/L, indicating that the pores of the membrane are completely wetted at this time, and the unmodified PVDF membrane has poor anti-wetting properties.
Example 2
A preparation method of POSS/PVDF composite membrane with hydrophobic surface comprises,
(1) preparation of alkali-treated PVDF film: immersing PVDF film in 3 mol. L-1And treating the PVDF membrane at 30 ℃ for 4 hours to introduce hydroxyl groups into the surface of the PVDF membrane to obtain the alkali-treated PVDF membrane.
(2) Preparation of modified PVDF membrane: dissolving MPTES in ethanol, and stirring to obtain modified solution with concentration of 0.2 mol.L-l(ii) a And (2) soaking the alkali-treated PVDF membrane obtained in the step (1) in a modifying solution at 30 ℃ for 4 hours, taking out the membrane, washing the membrane with ethanol, and drying the membrane at 70 ℃ for 4 hours to obtain the modified polyvinylidene fluoride membrane.
(3) Preparing sol: adding OVPOSS into DMC, magnetically stirring for 4h at the rotating speed of 200r/min, and then ultrasonically dispersing for 4h at 25 ℃ to fully dissolve the OVPOSS in the DMC to obtain an OVPOSS/DMC solution with the mass fraction of 2%; and then, adding HMPF (high molecular weight polyethylene) serving as a photoinitiator into the OVPOSS/DMC solution, and magnetically stirring for 4 hours at the rotating speed of 200r/min to obtain sol, wherein the mass ratio of the OVPOSS to the HMPF is 1: 8.
(4) Preparing an OVPOSS/PVDF composite membrane: immersing the modified PVDF membrane in the step (2) into the sol in the step (3), irradiating for 40min at a position 40 cm away from an ultraviolet lamp, and initiating a mercapto-vinyl click reaction through ultraviolet irradiation to graft OVPOSS on the surface of the modified PVDF membrane; and then, taking the grafted PVDF membrane out of the sol, washing the PVDF membrane for 1min by using ethanol, and drying the PVDF membrane at the temperature of 60 ℃ to obtain the OVPOSS/PVDF composite membrane.
The membrane water contact angle of the OVPOSS/PVDF composite membrane prepared by the embodiment is 153.5 degrees, and the rolling angle is 8.8 degrees. The OVPOSS/PVDF composite membrane is subjected to a 150-hour membrane distillation anti-pollution test by taking sodium chloride, humic acid and calcium chloride as feed liquid (containing 100g/L of sodium chloride, 2.22g/L of calcium chloride and 50mg/L of humic acid) and a 2-hour membrane distillation anti-wetting test by taking sodium chloride and sodium dodecyl sulfate as feed liquid (the concentrations of the sodium dodecyl sulfate are 0.1mmol/L, 0.2mmol/L and 0.3mmol/L respectively, and the concentration of the sodium chloride is 35g/L), so that the flux of the modified membrane is stable, and the phenomenon of membrane pollution or membrane wetting does not occur.
Example 3
A preparation method of POSS/PVDF composite membrane with hydrophobic surface comprises,
(1) preparation of alkali-treated PVDF film: immersing PVDF film in 4 mol. L-1And treating the PVDF membrane at 40 ℃ for 6 hours to introduce hydroxyl groups into the surface of the PVDF membrane, thereby obtaining the alkali-treated PVDF membrane.
(2) Preparation of modified PVDF membrane: dissolving MPTES in ethanol, and stirring to obtain modified solution with concentration of 0.3 mol.L-1(ii) a And (2) soaking the alkali-treated PVDF membrane obtained in the step (1) in a modifying solution at 40 ℃ for 6 hours, taking out the membrane, washing the membrane with ethanol, and drying the membrane at 80 ℃ for 6 hours to obtain the modified polyvinylidene fluoride membrane.
(3) Preparing sol: adding OVPOSS into DMC, magnetically stirring for 6h at the rotating speed of 300r/min, and then ultrasonically dispersing for 6h at 30 ℃ to fully dissolve the OVPOSS in the DMC to obtain an OVPOSS/DMC solution with the mass fraction of 3%; and then, adding HMPF (high molecular weight polyethylene) serving as a photoinitiator into the OVPOSS/DMC solution, and magnetically stirring for 6 hours at the rotating speed of 300r/min to obtain sol, wherein the mass ratio of the OVPOSS to the HMPF is 1: 10.
(4) Preparing an OVPOSS/PVDF composite membrane: immersing the modified PVDF membrane in the step (2) into the sol in the step (3), irradiating for 60min at a position 60cm away from an ultraviolet lamp, and initiating a mercapto-vinyl click reaction through ultraviolet irradiation to graft OVPOSS on the surface of the modified PVDF membrane; and then, taking the grafted PVDF membrane out of the sol, washing the PVDF membrane for 1min by using ethanol, and drying the PVDF membrane at the temperature of 60 ℃ to obtain the OVPOSS/PVDF composite membrane.
The membrane water contact angle of the OVPOSS/PVDF composite membrane prepared by the embodiment is 156.7 degrees, and the rolling angle is 7.1 degrees. The OVPOSS/PVDF composite membrane is subjected to a 150-hour membrane distillation anti-pollution test by taking sodium chloride, humic acid and calcium chloride as feed liquid (containing 100g/L of sodium chloride, 2.22g/L of calcium chloride and 50mg/L of humic acid) and a 2-hour membrane distillation anti-wetting test by taking sodium chloride and sodium dodecyl sulfate as feed liquid (the concentrations of the sodium dodecyl sulfate are 0.1mmol/L, 0.2mmol/L and 0.3mmol/L respectively, and the concentration of the sodium chloride is 35g/L), so that the flux of the modified membrane is stable, and the phenomenon of membrane pollution or membrane wetting does not occur.
Example 4
A preparation method of POSS/PVDF composite membrane with hydrophobic surface comprises,
(1) preparation of alkali-treated PVDF film: immersing PVDF film in 5 mol. L-1And treating the PVDF membrane at 50 ℃ for 8 hours to introduce hydroxyl groups into the surface of the PVDF membrane to obtain the alkali-treated PVDF membrane.
(2) Preparation of modified PVDF membrane: dissolving MPTES in ethanol, and stirring to obtain modified solution with concentration of 0.4 mol.L-1(ii) a And (2) then, soaking the alkali-treated PVDF membrane obtained in the step (1) in a modifying solution at 50 ℃ for 8 hours, taking out the membrane, washing the membrane with ethanol, and drying the membrane at 90 ℃ for 8 hours to obtain the modified polyvinylidene fluoride membrane.
(3) Preparing sol: adding OVPOSS into DMC, magnetically stirring for 8h at the rotating speed of 400r/min, and then ultrasonically dispersing for 8h at 35 ℃ to fully dissolve the OVPOSS in the DMC to obtain an OVPOSS/DMC solution with the mass fraction of 4%; and then, adding HMPF (high molecular weight polyethylene) serving as a photoinitiator into the OVPOSS/DMC solution, and magnetically stirring for 8 hours at the rotating speed of 400r/min to obtain sol, wherein the mass ratio of the OVPOSS to the HMPF is 1: 15.
(4) Preparing an OVPOSS/PVDF composite membrane: immersing the modified PVDF membrane in the step (2) into the sol in the step (3), irradiating for 80min at a position 80cm away from an ultraviolet lamp, and initiating a sulfydryl-vinyl click reaction through ultraviolet irradiation to graft OVPOSS on the surface of the modified PVDF membrane; and then, taking the grafted PVDF membrane out of the sol, washing the PVDF membrane for 1min by using ethanol, and drying the PVDF membrane at the temperature of 60 ℃ to obtain the OVPOSS/PVDF composite membrane.
The membrane water contact angle of the OVPOSS/PVDF composite membrane prepared by the embodiment is 158.4 degrees, and the rolling angle is 7.0 degrees. The OVPOSS/PVDF composite membrane is subjected to a 150-hour membrane distillation anti-pollution test by taking sodium chloride, humic acid and calcium chloride as feed liquid (containing 100g/L of sodium chloride, 2.22g/L of calcium chloride and 50mg/L of humic acid) and a 2-hour membrane distillation anti-wetting test by taking sodium chloride and sodium dodecyl sulfate as feed liquid (the concentrations of the sodium dodecyl sulfate are 0.1mmol/L, 0.2mmol/L and 0.3mmol/L respectively, and the concentration of the sodium chloride is 35g/L), so that the flux of the modified membrane is stable, and the phenomenon of membrane pollution or membrane wetting does not occur.
Example 5
A preparation method of POSS/PVDF composite membrane with hydrophobic surface comprises,
(1) preparation of alkali-treated PVDF film: immersing PVDF membrane in 6 mol.L-1And treating the PVDF membrane at 60 ℃ for 10 hours to introduce hydroxyl groups into the surface of the PVDF membrane to obtain the alkali-treated PVDF membrane.
(2) Preparation of modified PVDF membrane: dissolving MPTES in ethanol, and stirring to obtain modified solution with concentration of 0.5 mol.L-1(ii) a And (2) then, immersing the alkali-treated PVDF membrane obtained in the step (1) in a modifying solution at 60 ℃, taking out after immersing for 10h, washing with ethanol, and drying at 100 ℃ for 10h to obtain the modified polyvinylidene fluoride membrane.
(3) Preparing sol: adding OVPOSS into DMC, magnetically stirring for 10h at the rotating speed of 500r/min, and then ultrasonically dispersing for 10h at 40 ℃ to fully dissolve the OVPOSS in the DMC to obtain an OVPOSS/DMC solution with the mass fraction of 5%; and then, adding HMPF (high molecular weight polyethylene) serving as a photoinitiator into the OVPOSS/DMC solution, and magnetically stirring for 10 hours at the rotating speed of 500r/min to obtain sol, wherein the mass ratio of the OVPOSS to the HMPF is 1: 20.
(4) Preparing an OVPOSS/PVDF composite membrane: immersing the modified PVDF membrane in the step (2) into the sol in the step (3), irradiating for 100min at a position 100cm away from an ultraviolet lamp, and initiating a sulfydryl-vinyl click reaction through ultraviolet irradiation to graft OVPOSS on the surface of the modified PVDF membrane; and then, taking the grafted PVDF membrane out of the sol, washing the PVDF membrane for 1min by using ethanol, and drying the PVDF membrane at the temperature of 60 ℃ to obtain the OVPOSS/PVDF composite membrane.
The membrane water contact angle of the OVPOSS/PVDF composite membrane prepared by the embodiment is 156.4 degrees, and the rolling angle is 7.7 degrees. The OVPOSS/PVDF composite membrane is subjected to a 150-hour membrane distillation anti-pollution test by taking sodium chloride, humic acid and calcium chloride as feed liquid (containing 100g/L of sodium chloride, 2.22g/L of calcium chloride and 50mg/L of humic acid) and a 2-hour membrane distillation anti-wetting test by taking sodium chloride and sodium dodecyl sulfate as feed liquid (the concentrations of the sodium dodecyl sulfate are 0.1mmol/L, 0.2mmol/L and 0.3mmol/L respectively, and the concentration of the sodium chloride is 35g/L), so that the flux of the modified membrane is stable, and the phenomenon of membrane pollution or membrane wetting does not occur.
The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only illustrative of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.
Claims (10)
1. A preparation method of a POSS/PVDF composite membrane with a hydrophobic surface comprises the following steps:
performing alkali liquor treatment on the polyvinylidene fluoride membrane by using alkali liquor to obtain an alkali-treated polyvinylidene fluoride membrane;
dissolving 3-mercaptopropyltriethoxysilane in ethanol to obtain a modified solution; then, modifying the alkali-treated polyvinylidene fluoride membrane by using the modifying liquid to obtain a modified polyvinylidene fluoride membrane;
dissolving octavinyl polyhedral oligomeric silsesquioxane in dichloromethane to obtain a solution, and then adding 2-hydroxy-2-methyl propiophenone into the solution to obtain sol;
and immersing the modified polyvinylidene fluoride membrane into the sol, and irradiating by adopting an ultraviolet lamp to prepare the POSS/PVDF composite membrane.
2. The method for preparing POSS/PVDF composite membrane with hydrophobic surface according to claim 1,
the method for treating the polyvinylidene fluoride membrane by using the alkali liquor comprises the following steps:
soaking the polyvinylidene fluoride membrane in the alkali liquor for 2-10h at the temperature of 20-60 ℃, and then drying at the temperature of 60-100 ℃ to obtain the alkali-treated polyvinylidene fluoride membrane.
3. The method for preparing POSS/PVDF composite membrane with hydrophobic surface according to claim 1 or 2,
wherein the alkali liquor is sodium hydroxide solution;
the concentration of the sodium hydroxide solution is 2-6 mol.L-1。
4. The method for preparing POSS/PVDF composite membrane with hydrophobic surface according to claim 1,
the alkali treatment polyvinylidene fluoride membrane is modified by the modifying solution to obtain a modified polyvinylidene fluoride membrane, which comprises,
and soaking the alkali-treated polyvinylidene fluoride membrane in the modification solution for 2-10h at the temperature of 20-60 ℃, and then drying at the temperature of 60-100 ℃ to obtain the modified polyvinylidene fluoride membrane.
5. The method for preparing POSS/PVDF composite membrane with hydrophobic surface according to claim 1 or 4,
wherein the concentration of the modifying solution is 0.1-0.5 mol.L-1。
6. The method for preparing POSS/PVDF composite membrane with hydrophobic surface according to claim 1,
wherein the octavinyl polyhedral oligomeric silsesquioxane is dissolved in dichloromethane to obtain a solution, and then 2-hydroxy-2-methyl propiophenone is added into the solution to obtain sol, comprising,
adding the octavinyl polyhedral oligomeric silsesquioxane into the dichloromethane, and stirring at the rotating speed of 100-500r/min for 2-10 h; then, ultrasonically dispersing for 2-10h at 20-40 ℃ to dissolve the octavinyl cage-type silsesquioxane to obtain the solution; adding the 2-hydroxy-2-methyl propiophenone into the solution, and stirring at the rotating speed of 100-500r/min for 2-10h to obtain the sol.
7. The method for preparing POSS/PVDF composite membrane with hydrophobic surface according to claim 1 or 6,
wherein the mass fraction of the octavinyl cage type silsesquioxane in the solution is 1-5%;
the mass ratio of the octavinyl cage-type silsesquioxane to the 2-hydroxy-2-methyl propiophenone is 1: 5-20.
8. The method for preparing POSS/PVDF composite membrane with hydrophobic surface according to claim 1,
the irradiation power of the ultraviolet lamp is 250W, and the irradiation time is 20-100 min;
the distance between the ultraviolet lamp and the modified polyvinylidene fluoride membrane is 20-100 cm.
9. A POSS/PVDF composite membrane obtained by the method of any one of claims 1-8.
10. Use of a POSS/PVDF composite membrane of claim 9 in membrane distillation.
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