TWI487620B - Low thermal conductivity membrane and producing method thereof and membrane distillation apparatus - Google Patents

Description

Low thermal conductive film, preparation method thereof and thin film distillation device having the same

The present disclosure relates to the field of thin film distillation technology, and more particularly to a low thermal conductivity film, a process for the same, and a thin film distillation apparatus having the same.

Thin film distillation still needs to overcome the problem of low film flux in water recovery and reuse, and temperature polarization is an important factor in the attenuation of flux. At present, in the thin film distillation system, the temperature polarization phenomenon caused by the heat transfer loss is improved by increasing the crossflow speed and the module design, but at the same time increasing the equipment investment cost and energy consumption. problem.

Therefore, in order to improve the impact of temperature polarization on the system, it is necessary to develop other ways to solve this problem and improve the competitiveness of thin film distillation technology.

The present disclosure provides a method for fabricating a low thermal conductive film, comprising providing a modified and hydrophobic multi-media pore particle; and mixing the modified plurality of intermediate pore particles in a solution having a polymer to obtain electrospinning And electrospinning the electrospinning solution to obtain the low thermal conductive film.

According to the foregoing method, the present disclosure provides a low thermal conductive film comprising a plurality of layers of polymer fibers, each of the polymer fiber layers comprising a plurality of polymer fibers; and a modified plurality of medium pore particles, each of which is located Between the polymer fiber layer layers, at least one of the polymer fibers, or between the plurality of polymer fibers in the polymer fiber layer, and the modified medium particle content in the low heat conductive film is 1 to 50% by weight.

In another aspect, the present disclosure provides a thin film distillation apparatus including a cuvette; and the low thermal conductive film of the present disclosure is disposed in the housing to separate a high greenhouse and a low greenhouse, wherein the high greenhouse It is for injecting water to be treated, and the low greenhouse receives the permeated water produced from the low thermal conductive film.

As can be seen from the above, the present invention can reduce the temperature of the low-heat-conducting nanofiber separation film for thin film distillation by electrospinning by introducing the modified hydrophobic mesopores into the electrospinning solution. The phenomenon of increasing the thermal insulation value of the film.

101‧‧‧Water supply tank

101a‧‧‧ water to be treated

102, 105, 107, 110‧‧‧ pipeline

103, 108‧‧‧

104‧‧‧ 容容

104a‧‧‧High Greenhouse

104b‧‧‧Low thermal conductivity film

104c‧‧‧low greenhouse

106, 111‧‧ ‧ heat exchanger

109‧‧‧Water storage tank

109a‧‧‧ Penetration of water

Fig. 1 is a schematic view showing a thin film distillation apparatus; Fig. 2 is an SEM image showing the pores in the middle hole; Fig. 3 is a TEM image showing the particles in the middle hole; and Fig. 4 is a view showing the pore particles in the modified medium. a film; FIG. 5 shows a low thermal conductive film added with 1 wt% of the modified plurality of void particles; and FIG. 6 shows a low thermal conductive film added with 10 wt% of the modified plurality of void particles; Fig. 7 is a view showing a low thermal conductive film in which 50 wt% of the modified plurality of void particles are added; and Fig. 8 is a graph showing a low thermal conductivity film flux of different amounts of the void particles.

Other embodiments of the present invention will be readily understood by those skilled in the art from this disclosure.

The present disclosure provides a method for producing a low thermal conductive film comprising providing mesoporous particles which are modified to be hydrophobic; and mixing the modified interstitial particles in a solution having a polymer to obtain an electrospinning solution And electrospinning the electrospinning solution to obtain the low thermal conductive film.

The method for producing the pore particles in the present disclosure is not particularly limited, and it can be prepared by a conventional sol-gel method, for example, dispersing a precursor in a solution containing a surfactant to carry out a self-assembly reaction; And removing the surfactant.

In one embodiment, the mesoporous particles are prepared by a sol-gel method using a surfactant formed by a surfactant and an inorganic precursor, such as a diluted ceria precursor (dilute). Silica precursor) performing a self-assembly reaction and removing the surfactant, and the obtained pore particles have a pore diameter of about 2 to 5 nm, a particle diameter of about 0.3 to 4 μm , and a porosity of about 45%. 80%. In addition, if the pore diameter of the mesoporous particles is too large, the particle strength is insufficient to be easily broken. If the particle size of the mesoporous particles is too large, the pinholes are easily blocked during spinning, and the resulting low thermal conductive film pores are too large, and the treatment efficiency is lowered.

Specifically, the inorganic precursor may be sodium aluminate, tetramethyl ammonium silicate or cerium oxide. As an example of a surfactant, such as an uncharged amine surfactant such as Pluronic P123 as a template, a micelle formed under acidic conditions is formed by reacting an inorganic precursor with a template. The surfactant is removed to form mesopores, and the resulting particle size is μ1 μm . Alternatively, a microelectrode formed by a positively charged tetrapolar ammonium salt such as cetyltrimethylammonium bromide (CTABr) as a template under a basic condition and a positively charged helium oxygen atom via a hydrogen bond The cells are self-assembled and the surfactant is removed to form mesopores.

In another embodiment, the modified pore particles may be made of activated carbon, carbon black, carbon nanotubes, or graphene.

In the preparation of the intermediate pores to make the hydrophobicity, the hydrophobic group may be grafted to the surface of the mesoporous particles and the inner surface of the pore by copolymerization or grafting, wherein the hydrophobic group may be C ₁ -C ₁₀ alkyl, vinyl, propenyl, or phenyl.

The preparation method of the copolymerization method comprises: dispersing a precursor having a hydrophobic group in a solution containing a surfactant to perform a self-assembly reaction, wherein the precursor may be a plurality of species, but at least one of the precursors has a hydrophobic group And removing the surfactant to obtain modified intermediate pore particles grafted with the hydrophobic group on the surface and the inner surface of the pore.

For example, by imparting functionalization to mesoporous particles, introduction of a hydrophobic functional group such as an alkenyl group such as a vinyl group can be carried out by a copolymerization chemical reaction. For example, tetraethoxy decane (TEOS) and vinyl triethoxy decane (TEVS) are used as inorganic precursors, and CTABr is used as a template under alkaline conditions, self-assembled at room temperature, and extracted by ethanol/water. The template was removed, and after filtration, the hydrophobic medium-porous particles having a vinyl group on the surface were obtained.

For example, the introduction of a hydrophobic functional group of a methyl group or another alkyl group is carried out by grafting, for example, by placing mesoporous particles in a hexamethyldioxane (HMDS)/toluene solution and reacting at 100 ° C. After one hour, it was filtered and dried to obtain a hydrophobic medium-containing pore particle containing a methyl group.

The verification of the functional group can be confirmed by Fourier transform infrared spectroscopy (FTIR), and the thermogravimetric analyzer (TGA) can calculate the percentage ratio of the functional group. In addition, the verification of the hydrophobic medium-containing pore particles can be confirmed by delamination of the organic/aqueous solution. Hydrophobic mesoporous particles are present in the upper organic phase.

In the foregoing electrospinning step, the amount of the pore particles mixed in the modified portion is from 1 to 50% by weight of the electrospinning solution to increase the characteristic holding value of the film. Additionally, the polymer used may be selected from at least one of the group consisting of PP, PTFE, PVDF, and polydifluoroethylene-hexafluoropropylene (PVDF-co-HFP).

According to the foregoing method, the present disclosure provides a low thermal conductive film comprising a plurality of layers of polymer fibers, each of the polymer fiber layers comprising a plurality of polymer fibers; and a modified plurality of medium pore particles, the modified plural The mesoporous particles may be located between each of the polymer fiber layer layers, at least one of the polymer fibers, or between the plurality of polymer fibers in the polymer fiber layer, and the modified medium pore particles in the low thermal conductive film The content is about 1 to 50% by weight.

In one embodiment, the polymer fiber can be selected from at least one of the group consisting of PP, PTFE, PVDF, and polyvinylidene fluoride-hexafluoropropylene.

Generally, the material of the modified pore particles may be mainly cerium oxide, activated carbon, carbon black, carbon nanotubes, or graphene. The mesoporous particles have a pore size of about 2 to 5 nm, a particle diameter of about 0.3 to 4 μm , and a porosity of about 45% to 80%.

In one embodiment, the modified pore particles have a hydrophobic group, and the hydrophobic group can be a C ₁ -C ₁₀ alkyl group, a vinyl group, a propylene group, or a phenyl group.

Moreover, in the low thermal conductive film of the present disclosure, it has a plurality of pores having a size of about 0.05 to 1 μm , and the low thermal conductive film has a porosity of about 40% to 81%, and a contact angle of about 120 to 140 degrees. The value is about 0.09 to 0.12 ° C ‧ m ² /W.

In one embodiment, the electrospun low thermal conductive film has a thickness of about 30 to 90 μm . Further, the polymer fibers have a diameter of about 200 to 230 nm.

In another embodiment, the low thermal conductive film comprises a support material formed on one side surface of the low thermal conductive film to be suitable for a thin film distillation apparatus.

The present disclosure provides a thin film distillation apparatus, as shown in FIG. 1, including a cavity 104; and the low thermal conductive film 104b of the present disclosure is disposed in the housing 104 to separate the high greenhouse 104a and the low greenhouse 104c. The high temperature chamber 104a is for injecting water to be treated 101a, and the low temperature chamber 104c receives the permeated water 109a produced from the low thermal conductive film 104b.

In another embodiment, the thin film distillation apparatus further includes a heat exchanger 106 to maintain the temperature of the water to be treated 101a and its temperature difference from the permeate water 109a. In yet another embodiment, the complex heat exchanger 111 is included to condense the permeate water 109a.

In a specific embodiment, the water to be treated 101a is pumped through the pump 103, flows into the high temperature chamber 104a in the tank 104 via the pipeline 102, and the pipeline 105 can also treat the water to be treated 101a in the high greenhouse 104a. Returned to the water supply tank 101. The water vapor generated in the tank 104 enters the low temperature chamber 104c through the low heat conductive film 104b, and the permeate water 109a is condensed in the low temperature chamber 104c, and is pumped through the pump 108 into the water storage tank 109 via the pipeline 107. The line 110 can also return the water in the water storage tank 109 to the low temperature chamber 104c of the tank 104.

Example Preparation of medium pore particles

Prepared using a conventional sol-gel process comprising a mixed inorganic precursor tetramethylammonium citrate (1 mmole, Aldrich) and cetyltrimethylammonium bromide as a template (CTABr, 0.125) Mume, Aldrich), self-assembly reaction (self assernbly) under alkaline conditions (containing NaOH, 0.3 mmole and water 1197 mmole), and then removing the template to form mesopores. According to the SEM image of Fig. 2 and the TEM image of Fig. 3, the mesoporous particles are mainly between 0.3 and 4 μm and have a pore diameter of 2 to 5 nm.

Preparation of hydrophobic medium pore particles

According to the method for preparing the hydrophobic medium pore particles, different chemical functional groups are grafted into the pores to perform hydrophobic functional modification to prepare hydrophobicity. Medium hole particles.

In the example of introducing a vinyl group, tetraethoxydecane (TEOS, 0.75 mmole, Aldrich) and vinyltriethoxydecane (TEVS, 0.25 mmole, Aldrich) are used as inorganic precursors at a pH of 10 The template was removed by CTABr (0.3 mmole) at 12 °C, and after self-assembly at room temperature, the template was removed by ethanol/water extraction, and dried by filtration to obtain hydrophobic mesoporous particles having a vinyl group on the surface.

In the example of introducing a methyl group, the pore particles (1 g) in the above examples are placed in a hexamethyldioxane (HMDS) / toluene solution (100 ml, volume ratio of 2/1) at 100 After reacting at ° C for one hour, it was filtered and dried to obtain a hydrophobic medium-containing pore particle containing a methyl group.

A hydrophobic functional group -CH ₂ =CH ₂ was obtained via copolymerization, and a weak peak was observed from 1680-1610 cm ^-1 from the FTIR spectrum. The modified medium pore particles having a -CH ₃ functional group at the end were obtained by grafting, and the CH" bending vibration signals of 1455 and 1378 cm ^-1 were observed on the FTIR spectrum.

Preparation of low thermal conductivity film Example 1

A plurality of mesoporous particles modified with a -CH ₂ =CH ₂ chemical functional group are introduced into a material of polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP) and dimethylformamide (DMF). In the electrospinning solution in which the solvent is disposed, 1 wt% of the modified plurality of pores in the plurality of pores are added, and a low thermal conductive film is prepared by an electrospinning technique.

Examples 2 to 4

Examples 2 to 4 are the steps of Example 1, respectively, adding 10% by weight, 20% by weight, and 50% by weight of the modified plurality of intermediate pore particles, and then preparing a low thermal conductive film by an electrospinning technique.

Comparative example 1

In the electrospinning solution prepared by using polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP) as a raw material and dimethylformamide (DMF) as a solvent, no modified plurality of modified pores are added. The particles were subjected to an electrospinning technique to prepare a low thermal conductive film, and the composition thereof is shown in Table 1, and the SEM photographs of the low thermal conductive films are shown in Figs. 4 to 7.

test

The conditions of the thin film distillation system used in this test example include: a high-temperature inlet end and a low-temperature water-producing end, respectively, a prepared 3,000 μS/cm NaCl aqueous solution and deionized water, separated by a film on both sides, and a low-temperature water-producing end and a high-temperature inlet. The water temperature at the water end is 30 ° C and 70 ° C and a sweep speed of 1.1 × 10 ^-2 m / sec. From the data shown in Fig. 8, it is known that when the amount of pore particles added in the modified plural increases from 0 wt% to 50 wt%, the flux of the system rises by about 1.5 times from 8.1 LMH to 11.31 LMH.

The thermal insulation values of the modified low-heat-conducting film were not 0.07 and 0.12 °C ‧ m ² / respectively. W, showing control and reducing the thermal conductivity of the film material will effectively improve the performance of the thin film distillation system. In addition, the low thermal conductivity film is tested in the present invention, the conductivity of the water-producing end is less than 3 μS/cm, and the salt rejection rate is 99.9%. According to the above, the low thermal conductivity film can maintain excellent salt rejection rate in addition to increasing flux. .

101‧‧‧Water supply tank

101a‧‧‧ water to be treated

102, 105, 107, 110‧‧‧ pipeline

103, 108‧‧‧

104‧‧‧ 容容

104a‧‧‧High Greenhouse

104b‧‧‧Low thermal conductivity film

104c‧‧‧low greenhouse

106, 111‧‧ ‧ heat exchanger

109‧‧‧Water storage tank

109a‧‧‧ Penetration of water

Claims (20)

A method for preparing a low thermal conductive film, comprising: providing a modified and hydrophobic multi-media pore particle; and mixing the modified plurality of intermediate pore particles in a solution having a polymer to obtain an electrospinning solution, and electrostatically The electrospinning solution was spun to obtain the low thermal conductive film. The method for producing a low thermal conductive film according to claim 1, wherein the material of the modified void particles is ceria, activated carbon, carbon black, carbon nanotubes, or graphene. The method for producing a low thermal conductive film according to claim 1, wherein the modified pores have a pore size of 2 to 5 nm, a particle diameter of 0.3 to 4 μm , and a porosity of 45% to 80%. The method for preparing a low thermal conductive film according to claim 1 includes preparing the modified plurality of medium pore particles, and the preparation method comprises: dispersing a hydrophobic group precursor in a solution containing a surfactant; And performing the self-assembly reaction; and removing the surfactant to obtain the modified interstitial particles grafted with the hydrophobic group in the surface and the inner surface of the cavity. The method for preparing a low thermal conductive film according to claim 1 includes preparing the modified plurality of medium pore particles, and the preparation method is to graft the hydrophobic group to the surface of the medium pore particle and the pore by a grafting method. In the surface. A method of producing a low thermal conductive film according to claim 4 or 5, wherein the hydrophobic group is a C ₁ -C ₁₀ alkyl group, a vinyl group, a propylene group, or a phenyl group. The method for producing a low thermal conductive film according to claim 1, wherein the modified plurality of void particles are mixed in an amount of from 1 to 50% by weight of the electrospinning solution. The method for producing a low thermal conductive film according to claim 1, wherein the polymer is at least one selected from the group consisting of PP, PTFE, PVDF, and polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP). By. A low thermal conductivity film comprising: a plurality of layers of polymer fibers, each of the polymer fiber layers comprising a plurality of polymer fibers; and a modified plurality of medium pore particles located between each of the polymer fiber layers and at least one polymerized Between the plurality of polymer fibers in the fiber or in the polymer fiber layer, and the modified void particle content in the low heat conductive film is 1 to 50% by weight. The low thermal conductive film of claim 9, wherein the polymer fiber is at least one selected from the group consisting of PP, PTFE, PVDF, and polyvinylidene fluoride-hexafluoropropylene. The low thermal conductive film of claim 9, wherein the material of the modified void particles is ceria, activated carbon, carbon black, carbon nanotubes, or graphene. The low thermal conductive film of claim 9, wherein the modified pore particles have a pore size of 2 to 5 nm, a particle diameter of 0.3 to 4 μm , and a porosity of 45% to 80%. The low thermal conductive film of claim 9, wherein the modified pore particles have a hydrophobic group, and the hydrophobic group is a C ₁ -C ₁₀ alkyl group, a vinyl group, a propylene group, or a phenyl group. . A low thermal conductive film according to claim 9 which has a plurality of pores having a size of 0.05 to 1 μm , and the low thermal conductivity film has a porosity of 40% to 81% and a contact angle of 120 to 140 degrees. Degree, characteristic insulation value is 0.09 ° C. m ² /W to 0.12 ° C. m ² /W. The low thermal conductive film of claim 9 is a thickness of 30 to 90 μm . The low thermal conductive film of claim 9, wherein the polymer fiber has a diameter of 200 to 230 nm. A low thermal conductive film according to claim 9 of the patent application, further comprising a support material formed on one side surface of the low thermal conductive film. A thin film distillation apparatus comprising: a receiving tank; and a low thermal conductive film according to claim 9 of the patent application, which is disposed in the tank to separate the high greenhouse and the low greenhouse, wherein the high greenhouse is for injection to be treated Water, the low temperature system receives the permeated water produced from the low thermal conductivity film. A thin film distillation apparatus according to claim 18, further comprising a heat exchanger for maintaining a temperature of the water to be treated and a temperature difference from the permeated water. A thin film distillation apparatus according to claim 18, further comprising another heat exchanger for condensing the permeated water.