TWI674142B - An omniphobic membrane and its preparation - Google Patents

Abstract

The invention relates to a fully sparse film and a method for manufacturing the same. The fully sparse film comprises a porous substrate having a pore size of 0.4-2 μm, a surface layer and an interface layer. The interface layer is formed on the porous substrate and Between the surface layers, the structure of the fully sparse film includes a layer of a hierarchical re-entrant structure and the carbon / silicon (C / Si) composition ratio of the fully sparse film is 40-60. Secondly, the present invention also provides a method for manufacturing the fully sparse film.

Description

Completely thin film and manufacturing method thereof

The invention relates to an omniphobic membrane and a method for manufacturing the same, and the application of the omniphobic membrane in thin film distillation. In particular, the fully sparse film provided by the present invention contains zinc oxide nano particles.

In the field of separation technology, thin film distillation belongs to a thermal separation process. Conventional technologies often use porous membranes as a barrier to create a gas-liquid interface in the pores of the membrane to facilitate mass transfer and gas-liquid exchange balance to achieve gas-liquid separation. purpose.

The traditional porous film can be used to treat clean water during the thin film distillation process. However, the wastewater containing trace amounts of surfactants cannot be treated with thin film distillation at all, so its application is greatly limited.

Based on the above technical background, a thin film that can be applied in the thin film distillation process to treat wastewater containing surfactants is a material technology that needs to be developed in order to solve the problem of wastewater containing surfactants in textiles, petrochemicals, etc. Related industries.

In view of the above background of the invention, in order to meet the requirements of the industry, a first object of the present invention is to provide a fully sparse film, which includes a porous substrate with a hole size of 0.4-2 μm, a surface layer and an interface layer. The interface layer is between the porous substrate and the surface layer. The structure of the fully sparse film includes a layered concave re-entrant structure and the carbon / silicon (C / Si) composition ratio of the fully sparse film. It's 40-60.

The fully sparse film provided by the present invention has a special layered recurentent structural structure and contains a high concentration of fluorine (F) on its surface. The degree of hydrophobicity of the aforesaid fully-repellent film is evaluated by measuring the contact angle. The higher the value, the higher the hydrophobicity. The water contact angle of the fully sparse film provided by the present invention is 152.8 ± 1.1 °, and the contact angle of ethanol is 110.3 ± 1.9 °. Compared with the traditional film which is not modified with zinc oxide nano particles, the fully sparse film provided by the present invention has a low surface tension feed liquid when applied in a direct membrane distillation (DCMD) process. Very good anti-wetting effect. Secondly, for the liquid feed is a 1M NaCl solution containing 0.3mM sodium dodecyl sulfate (SDS), during the thin film distillation process using the module equipped with the completely thin film of the present invention, the initial water flux can be maintained during the distillation process. It is proved that the fully sparse film of the present invention also has a special effect for treating low-tension surface-containing saline wastewater.

A second object of the present invention is to provide a method for manufacturing a fully sparse film, the steps of which are described below.

First, a chemical bath deposition method (Chemical Bath Deposition) is used to deposit a metal oxide on a porous substrate, and the pore size of the porous substrate is 0.4-2 μm; a film layer is covered on the metal oxide. Thus, an organic-inorganic hybrid layer is formed on the above porous substrate; and a fluorine-containing polymer is coated on the above-mentioned organic-inorganic hybrid layer, thereby forming the completely sparse film, The structure of the fully sparse film includes a layered concave re-entrant structure and the carbon / silicon (C / Si) composition ratio of the fully sparse film is 40-60.

Specifically, the method for manufacturing a fully sparse film provided by the present invention is to deposit a zinc oxide nanoparticle on a porous glass fiber or a hydrophilic substrate by chemical bath deposition, thereby forming a special The layered concave re-entrant structure is then subjected to the surface fluorination procedure of the structure, and finally the fluorine-containing polymer is used to reduce the surface energy of the film to prepare a fully sparse film according to the present invention.

A third object of the present invention is to provide a method for liquid desalination by thin film distillation.

Specifically, it includes the following steps: providing a separation module, the separation module is equipped with a completely thin film as described in the first object of the present invention; conveying a liquid into the above-mentioned separation module; and performing a thin film distillation process to make the The liquid passes through the completely thin film as described above, thereby achieving a liquid desalting rate greater than 90%.

Specifically, the above-mentioned desalination rate refers to a sodium chloride blocking rate.

When the completely thin film provided by the present invention is applied in a direct contact membrane distillation (DCMD) procedure, when the liquid feed is a 1M NaCl solution containing 0.3mM sodium dodecyl sulfate (SDS), the surface When the tension is about 31 mN / m, in the process of thin film distillation using the separation module equipped with the fully sparse membrane of the present invention, the initial water flux remains unchanged during the operation of the module, and its desalination rate is greater than 90% . Accordingly, it is proved that the fully sparse film of the present invention has the effect of treating low surface tension salty wastewater, and overcomes the problem bottleneck that cannot be solved by the conventional technology.

Figure 1 is a comparison of the manufacturing process of a conventional film and the fully sparse film of the present invention; the manufacturing process of a conventional film is sequentially treated with fluorosilane on glass fiber to obtain a hydrophobic film 1 (F1), and then fluorine-containing The polymer coating procedure obtains the hydrophobic film 2 (F2); the manufacturing process of the omniphobic film (OMNI) of the present invention is sequentially performed a glass fiber activation procedure to obtain activated glass fibers, deposit zinc oxide, and use a fluorine-containing silane for treatment. Finally, a fluorine-containing polymer coating program is performed to obtain an omniphobic thin film (OMNI) according to the present invention; FIG. 2 is a schematic diagram of the component configuration of a direct-contact thin-film distillation apparatus; and FIG. Figures 3 (a) and 3 (b) are SEM images of hydrophobic membrane 1 (F1) treated with fluorosilane Image diagrams; Figures 3 (c) and 3 (d) are SEM images of the hydrophobic membrane 2 (F2) obtained after treatment with a fluorosilane and then a fluoropolymer coating process; FIG. 3 ( e) and FIG. 3 (f) are SEM image diagrams of the OMNI film provided by the present invention; FIG. 4 is an XPS spectrum; wherein FIG. 4 (a) is an XPS (Survey of unactivated glass fiber) scans) full spectrum; Figure 4 (b) is a carbon XPS spectrum of unactivated glass fiber; Figure 4 (c) is a full XPS (Survey scans) spectrum of a hydrophobic membrane 1 (F1) treated with fluorosilane ; Figure 4 (d) is the carbon XPS spectrum of the hydrophobic membrane 1 (F1) on the surface treated with fluorine-containing silane; Figure 4 (e) is obtained after treatment with fluorine-containing silane and then through the gas-containing polymer coating program Full XPS (Survey scans) spectrum of the hydrophobic membrane 2 (F2); Figure 4 (f) is the carbon XPS of the hydrophobic membrane 2 (F2) obtained after treatment with a fluorosilane and then a fluoropolymer coating process Figure 4; Figure 4 (g) is the XPS (Survey scans) full map of the OMNI of the present invention; and Figure 4 (h) is the carbon XPS spectrum of the OMNI of the present invention; Figure 5 shows the glass fiber and hydrophobicity obtained by XPS analysis. 1. A histogram of the composition atomic concentration of the hydrophobic membrane 2 and the fully sparse membrane of the present invention; FIG. 6 is the water contact between the glass fiber, the hydrophobic membrane 1, the hydrophobic membrane 2 and the fully sparse membrane of the present invention disclosed in this specification. Histogram of contact angle and ethanol contact angle; Figure 7 is the direct contact thin film distillation performance test result of the film disclosed in this specification; Figure 7 (a) is the direct contact thin film distillation performance test of hydrophobic film 1 Result graph; Figure 7 (b) is a direct contact film of hydrophobic membrane 2 Distillation efficiency test result chart; FIG. 7 (c) is a direct contact film distillation efficiency test result chart of the fully sparse film of the present invention; and FIG. 7 (d) is a fully sparse film of the present invention containing 0.3 mM for the feed SDS direct contact thin film distillation efficiency test result chart; and Figure 8 is the action mechanism of the film disclosed in this specification; Figure 8 (a) shows the hole of the traditional glass fiber film due to the interface active agent partially wetting phenomenon And FIG. 8 (b) shows that the pores of the OMNI film of the present invention do not increase the water vapor mass transfer resistance due to the wetting phenomenon of the surface active agent and cause blockage.

The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. In order to thoroughly understand the present invention, detailed steps and their composition will be proposed in the following description. Obviously, the practice of the present invention is not limited to the specific details familiar to those skilled in the art. On the other hand, well-known components or steps are not described in detail to avoid unnecessary limitations of the present invention. The preferred embodiments of the present invention will be described in detail as follows. However, in addition to these detailed descriptions, the present invention can also be widely implemented in other embodiments, and the scope of the present invention is not limited, which is subject to the scope of subsequent patents. .

According to a first embodiment of the present invention, the present invention provides a fully sparse film, which includes a porous substrate having a pore size of 0.4-2 μm, and a surface layer. And an interface layer, the interface layer is between the porous substrate and the surface layer, and the structure of the fully sparse film includes a layered concave re-entrant structure and the carbon / silicon of the fully sparse film ( The C / Si) composition ratio is 40-60.

In one embodiment, the porous substrate includes glass fibers.

In an embodiment, the interface layer includes a film layer and a metal oxide, and the film layer covers the metal oxide; and the metal oxide is deposited on the porous substrate described above; specifically, the film layer is mainly It consists of a fluorosilane.

In one embodiment, the surface layer includes a fluorine-containing polymer, and the fluorine-containing polymer includes a copolymer of poly (vinylidene fluoride-co-hexafluoropropylene) and polytetrafluoroethylene (PTFE). Or polyvinylidene fluoride (PVDF).

In one embodiment, the film layer includes a fluorine-containing silane, and the fluorine-containing silane includes perfluorodecyltriethoxysilane (1H, 1H, 2H, 2H-Perfluorodecyltriethoxysilane; FAS17) or a polyhedral siloxane oligomer ( polyhedral oligomeric silsesquioxane; POSS).

In one embodiment, the metal oxide includes zinc oxide.

In one embodiment, the size of the metal oxide is 200-400 nm.

In one embodiment, the completely thin film is assembled in a distillation device, which includes a distillation device with a desalting rate greater than 94%, an air-spaced film distillation device, or a scavenging film distillation device.

According to a second embodiment of the present invention, the present invention provides a method for manufacturing a fully sparse film according to the first embodiment, which includes the following steps: Step 1: Use a chemical bath deposition method to deposit a metal oxide in a porous On the substrate, the pore size of the porous substrate is 0.4-2 μm; step two: covering a film layer on the metal oxide, thereby forming an organic-inorganic mixed layer on the porous substrate; and step 3: Coating a fluorine-containing polymer on the above-mentioned organic-inorganic mixed layer, thereby forming the fully sparse film. The structure of the fully sparse film includes a layered concave re-entrant structure and the fully sparse film. The carbon / silicon (C / Si) composition ratio is 40-60.

In one embodiment, the porous substrate includes glass fibers.

In one embodiment, the metal oxide includes zinc oxide.

In one embodiment, the size of the metal oxide is 200-400 nm.

In one embodiment, the film layer includes a fluorine-containing silane, and the fluorine-containing silane includes perfluorodecyltriethoxysilane (FAS17) or polyhedral siloxane oligomer (POSS).

In one embodiment, the fluorine-containing polymer comprises a copolymer of poly (vinylidene fluoride-co-hexafluoropropylene), polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF).

In a specific embodiment, as shown in FIG. 1, the manufacturing steps of the OMNI of the present invention are sequentially using KMnO4 to activate glass fibers at 84 ° C. Dimensional film (GF); chemical bath deposition method is used at 96 ° C with zinc nitrate as the main raw material to react and deposit zinc oxide on the activated glass fiber, and then use fluorosilane to perform surface treatment at 40 ° C, and finally perform fluoropolymer The coating procedure results in the omnipossible membrane (OMNI) of the present invention.

According to a third embodiment of the present invention, the present invention provides a method for liquid desalination by thin film distillation, which includes the following steps: Step 1: Provide a separation module, the separation module device is as described in the first embodiment of the present invention Step 2: Send a liquid to the above separation module; and Step 3: Perform a thin film distillation process to pass the liquid through the completely thin film according to the first embodiment of the present invention, thereby achieving liquid desalination. The rate is greater than 90%.

In one embodiment, the liquid includes seawater, an aqueous alkaline halide solution, wastewater containing a surfactant, or an aqueous solution having a surface tension of less than 30 mN / m.

Table 1 is the unactivated glass fiber disclosed in this specification; the surface is treated with fluorosilane (FAS17) for hydrophobic membrane 1 (F1); the fluorosilane (FAS17) is first treated, and then the fluoropolymer is coated Analysis of the elemental composition of the hydrophobic membrane 2 (F2) obtained by the cloth program and the omniphobic membrane (OMNI) of the present invention. The experimental data is calculated based on the analysis results of XPS.

The glass fibers, hydrophobic membranes 1, hydrophobic membranes 2 and omnidirectional membranes (OMNI) without surface treatment disclosed in this specification are analyzed for surface elemental composition using XPS (X-ray photoelectron) spectroscopy. The bonding energies of an XPS scan range from 0 to 1200 electron volts. The position of the absorption peak at about 105 electron volts corresponds to the Si 2p orbital region; the position of the absorption peak at about 288 electron volts corresponds to the C1s orbital region; the position of the absorption peak at about 535 electron volts corresponds to the O1s orbital region; the absorption peak is at About 688 electron volts corresponds to the F1s orbital region and the absorption peak at about 1033 electron volts corresponds to the Zn 2p orbital region.

According to the results of XPS analysis, the absorption peak of C1s is used to identify polymers. When the carbon atoms on the surface of the film are mainly in the form of metal carbonate, absorption peaks appear at 280-290 electron volts in the XPS spectrum. When the fluorinated thin film of the present invention is subjected to surface fluorination modification, the analysis result of XPS spectrum proves that the FAS17 used is successfully grafted on the surface of the film, and the XPS data is CF ₂ -CH ₂ (289.48 electron volts) ), CF ₂ -CF ₂ (292 electron volts), and CF ₃ -CF ₂ (293.87 electron volts). Secondly, the carbon atom absorption peak can also be observed between 284 and 288 electron volts, which proves that the polymer coating procedure successfully coated the fluorine-containing polymer on the surface of the film.

The data of the element survey scan on the surface of the thin film are full-spectrum data obtained by scanning the following sections with high-resolution XPS: C1s (279-296 electron volts), O1s (525-545 electron volts), Zn 2p (1015-1052 electron volts) ), Si 2p (95-115 electron volts) and F1s (678-698 electron volts). Among them, the F / C ratio is the highest in the omniphobic film (OMNI) of the present invention, and its value is 0.91; and the F / C values of the glass fiber and the hydrophobic membrane 1 and the hydrophobic membrane 2 without surface treatment are 0, 0.4, and 0.84, respectively. Based on this, it was proved that the fluorine-containing hydrophobic functional group was grafted on the surface of the glass fiber. XPS pattern elemental analysis also proves that ZnO is present in the fully sparse films of the present invention. The F / C of the XPS analysis of the glass fiber without modification is 0, indicating that the surface has no fluorine and therefore exhibits hydrophilicity. However, the surface energy of the thin film after fluorinated modification or after fluorinated modification and fluorine-containing polymer treatment is reduced due to the presence of fluorine, so it exhibits hydrophobic properties.

In summary, the fully sparse film of the present invention has a special layered hierarchical re-entrant structure and has the highest fluorine concentration. At the same time, the ZnO nano particles greatly increase the contact surface area of the film, so it can effectively Increasing the coating amount of fluorine-containing polymers makes the C / Si ratio increase to 40-60, which is more hydrophobic than traditional thin films. Secondly, when the thin film of the present invention is applied to thin film distillation, it can overcome the difficulties of the existing technology, and simultaneously achieve liquid desalination and treat low-surface-tension salt-containing wastewater. Therefore, it has an unexpected effect compared with the traditional hydrophobic film.

The following examples are based on the content described in the above embodiment. Experience, and based on this detailed description of the present invention.

Example 1: Preparation of Glass Fiber Films with ZnO Nanoparticles Deposited on Surface by Chemical Bath Deposition

In this experiment, chemical bath deposition was used to deposit ZnO on glass fibers (GF). First, using ₄ KMn04 activated glass fibers, the glass fibers with 100ml (containing 250mL of tert-butanol) concentrations 12.7mM KMnO ₄ aqueous solution with a water bath heated to about 84 deg.] C maintained 40 minutes, then washed ₄ KMn04 activated with clean deionized water Fiberglass until the color becomes light orange. After taking out, it was reacted and deposited at 96 ° C for 40 min with 50 mM zinc nitrate (ZnNO ₃ ) aqueous solution (87.5 mL of deionized water) containing 10 mL of triethanolamine and 2.5 mL of ammonium hydroxide, and then it was taken out, washed with deionized water and dried at 100 ° C Overnight, a glass fiber film with ZnO nano particles deposited on the surface was finally obtained.

Example 2: Fluorination Process on Thin Film Surface

The obtained glass fiber film with ZnO nano particles deposited on the surface was immersed in a 1% v / v FAS17 / n-hexane solution, reacted at 40 ° C for 24 hours, and then washed with n-hexane, and then dried at 90 ° C for 2 hours. A film having ZnO nanoparticle deposition on the surface of which was fluorinated by FAS17 was obtained.

Example 3: PVDF-HFP / FAS17 polymer coating process

First, PVDF-HFP particles and 50ml DMF are mixed and stirred until completely dissolved, 0.5ml FAS17 is added, and the stirring is continued for 0.5 hours. The film to be processed is immersed in the above-mentioned PVDF-HFP / FAS17 DMF solution for 1 minute and taken It was taken out and dried at 130 ° C for 1 hour to obtain a film coated with PVDF-HFP / FAS17 on the surface.

Example 4: Preparation of the fully sparse film (OMN1) of the present invention

As shown in Figure 1, first activate glass fibers with KMnO4 and deposit zinc oxide on the glass fibers by chemical bath deposition. The specific steps are described in Example 1. Surface treatment with fluorine-containing silane to obtain glass fibers / zinc oxide / fluorine-containing For the silane composite film, please refer to Example 2 for specific steps. Finally, a fluorine-containing polymer coating process is performed to obtain an omniphobic film (OMNI) of the present invention. For specific steps, refer to Example 3.

Thin film structure identification and analysis

The thin film disclosed in this specification uses the following equipment for identification and analysis of related structures: observation and analysis of the type and microstructure of the thin film using a scanning electron microscope (Nova NanoSEM, FEI, USA); using a contact angle measuring instrument (FTA125 , First Ten Angstroms, USA) Measure the contact angle of water (g = 72.8mN / m) and contact angle of ethanol (g = 22.1mN / m); use X-ray photoelectron spectroscopy (XPS, Thermo Scientific, Theta Probe, UK)) Analyze the elemental composition of the film, the excitation source is monochromatic A1 Kα; the operating conditions are 1.48668k electron volts / 140W, and the pressure of the analysis chamber in which the film sample is placed is 2.0 × 10 ^-9 mBar; The spectrum was further analyzed using software (CasaXPS Version 2.3.16 PR 1.6) and Gaussian-Lorentzian functions to calculate the elemental composition. The background value of the XPS survey scan was based on the position of C 284.6 electron volts.

Direct Contact Membrane Distillation

The device configuration for this test is shown in Figure 2, where the film to be tested is installed in a thin-film module and fixed with a silicone ring; experiments use 1M NaCl aqueous solution at 60 ° C as the feed. The flow rate is 0.5L / min and 20 ° C deionized water is used as permeate. Its flow rate is 0.4L / min. The feed and permeate are continuously circulated on both sides of the test membrane. The effective membrane filtration area is 10.74cm ² ; During the experiment, the surface active agent Sodium dodecyl sulfate (SDS) was fed with 1M NaCl (60 ° C) every two hours to reduce the surface tension of the feed and perform a film performance test. The sequential increase in the concentration was 0.1, 0.2 and 0.3 mM, and the corresponding surface tension of the feed was 42, 33 and 31 mN / m.

The permeate flux of the test film was calculated by the following formula (1).

Formula (1) J = △ W _p / A (△ t )

J : permeate flux (kg / m ² -h)

W _p : Penetration (kg)

A : active membrane surface area (m ² )

△ t : time interval (h)

The salt rejection rate (R _Nacl ; sodium chloride blocking rate) is calculated by the following formula (2): where the Nacl concentration is directly proportional to its conductivity, and the conductivity is measured using a conductivity meter (InoLab, Cond 7110).

: NaCl concentration of feed (mol / m ³ )

： Concentration of NaCl (mol / m ³ )

Membrane Morphologies

The surface type of the thin film disclosed in this specification was observed and analyzed with a scanning electron microscope (SEM). As shown in Fig. 3, Figs. 3 (a) to 3 (d) are the hydrophobic membrane 1 and the hydrophobic membrane 2 which have not been modified using the chemical bath deposition method, and Figs. 3 (e) and 3 ( f) is the omniphobic thin film (OMNI) of the present invention; according to the SEM image, it is obvious that ZnO deposited on the glass fiber can be observed from Figure 3 (e) and Figure 3 (f), and its size is about 271.3 ± 30.6nm; meanwhile, SEM showed that after chemically depositing ZnO nano-particles, its thin film structure was transformed into a layered concave re-entrant structure. Secondly, after the polymer coating procedure of the present invention, the ZnO nano particles can be strengthened to be fixed on the glass fiber. During the thin film distillation process, the ZnO nano particles are not easy to fall off the glass fiber, which makes the present invention The structure of the fully-thinned thin film is more stable, which improves the industrial applicability and stability of performance during operation of the fully-thinned thin film of the present invention.

Film composition analysis

Unactivated glass fibers, hydrophobic Membrane 1, Hydrophobic Membrane 2 and Omni Thin Film (OMNI) use the XPS (X-ray photoelectron) spectroscopic analysis technique to analyze the surface element composition. The bonding energy of the XPS scan ranges from 0 to 1200 electron volts. The specific spectra are shown in Figure 4 (a), Figure 4 (c), Figure 4 (e), and Figure 4 (g). . The position of the absorption peak at about 105 electron volts corresponds to the Si 2p orbital region; the position of the absorption peak at about 288 electron volts corresponds to the C1s orbital region; the position of the absorption peak at about 535 electron volts corresponds to the O1s orbital region; the absorption peak is at About 688 electron volts corresponds to the F1s orbital region and the absorption peak at about 1033 electron volts corresponds to the Zn 2p orbital region.

According to the results of XPS analysis, the absorption peak of C1s is used to identify polymers. When the carbon atoms on the surface of the film are mainly in the form of metal carbonate, absorption peaks appear at 280-290 electron volts in the XPS spectrum. When the film of the present invention is subjected to surface fluorination modification, the analysis result of XPS spectrum proves that the fluorine-containing silane (FAS17) used is successfully grafted on the surface of the film, and the XPS data thereof is CF ₂ -CH ₂ ( 289.48 electron volts), CF ₂ -CF ₂ (292 electron volts), and CF ₃ -CF ₂ (293.87 electron volts). Second, the carbon atom absorption peak can also be observed between 284 and 288 electron volts, which proves that the polymer coating program successfully coated the fluorine-containing polymer on the surface of the film. The specific map is shown in Figure 4 (f ) And Figure 4 (h).

Film surface element The full scan data is obtained by scanning the following intervals at high resolution: C1s (279-296 electron volts), O1s (525-545 electron volts), Zn 2p (1015-1052 electron volts), Si 2p (95 -115 electron volts) and F1s (678-698 electron volts). As shown in FIG. 5, the F / C ratio is the highest of the OMNI of the present invention, and its value is 0.91; and the F / C value of the glass fiber and the hydrophobic membrane 1 and the hydrophobic membrane 2 without surface treatment It is 0, 0.4 and 0.84 respectively; it is proved that the fluorine-containing hydrophobic functional group is grafted on the surface of the glass fiber. XPS pattern elemental analysis also proves that ZnO is present in the fully sparse films of the present invention. The F / C of the XPS analysis of the untreated glass fiber is 0, indicating that the surface is free of fluorine. However, the surface energy of the thin film after fluorinated modification or after fluorinated modification and polymer treatment is reduced due to the presence of fluorine, so it exhibits hydrophobic properties.

The C / Si ratio of the completely sparse film of the present invention is 45, which is mainly because the completely sparse film of the present invention has a very high surface area. Compared with untreated glass fiber (C / Si = 4.77), hydrophobic membrane 1 (C / Si = 6.1) and hydrophobic membrane 2 (C / Si = 4.53), the fully sparse film of the present invention can be clearly compared. It has an unexpected effect in increasing the contact surface area.

Contact angle measurement and analysis of film wetting behavior

The contact angles were measured using water (γ = 72.8mN / m) and ethanol (γ = 22.1mN / m) to evaluate the surface wetting behavior of the film, where water was used to evaluate the hydrophobicity of the film surface; ethanol was Used to evaluate the oleophobicity of the film surface. The specific results are shown in Figure 6. The water contact angles of the hydrophobic film 1, the hydrophobic film 2 and the OMNI thin film disclosed in this specification are all greater than 150 degrees, but when wetting with ethanol, the hydrophobic film 1 cannot be measured. Contact angle, and the hydrophobic membrane 2 was not measured after 20 seconds of wetting When it comes to the contact angle, only the OMNI of the present invention measures the contact angle, and the value is 110.3 ± 1.9 °, which proves that the surface of the omniphobic film of the present invention is extremely difficult to wet the aqueous and oily substances. This also shows that ZnO nano particles play a key role in the wetting behavior of the fully sparse film of the present invention. At the same time, the unique layered concave-angled structure (hierarchical re-entrant) structure only exists in the structure of the fully sparse film of the present invention. The -liquid-gas interface maintains a metastable Cassis thermodynamic state, but cannot produce a wetting effect on the fully sparse film of the present invention. According to this, the layered concave corner structure is also a key technical feature of the fully sparse film of the present invention.

Thin film effectiveness test

The hydrophobic membrane 1, the hydrophobic membrane 2, and the omnidirectional membrane (OMNI) disclosed in this specification are used to perform a membrane performance test using a direct-contact membrane distillation module. The test feed was a 1M NaCl aqueous solution at 60 ° C, the conductivity of which was 80,000 mS / cm; the conductivity of the permeate was 20 mS / cm. The performance test results of hydrophobic membrane 1 are shown in Figure 7 (a). During the initial distillation process, a certain relative flux was maintained (Permeate flux), but after 1 hour, 0.1 mM interface activity was added to the feed. Agent (SDS), the relative water flux immediately decreased sharply, showing that its effectiveness was seriously affected by the feed containing SDS to reduce surface tension. The performance test results of the hydrophobic membrane 2 are shown in Figure 7 (b). During the initial distillation process, a certain relative flux was maintained. After 1 hour, 0.1 mM SDS was added to the feed. Relative water flux It remains the same, but after an additional hour, when the 0.2mM SDS is added to the feed, its relative water flux immediately drops sharply, showing that its effectiveness will still be seriously affected by the feed containing SDS that reduces surface tension. In comparison, the performance test results of the OMNI of the present invention are shown in Figure 7 (c). Even when the feed contains 0.3 mM SDS, the surface tension of the feed is about 31 mN / m, its relative water flux remains unchanged. This proves that the fully sparse film of the present invention has an unexpected effect compared to other modified films.

In order to further confirm the thin film distillation performance of the fully sparse film of the present invention, a 1M NaCl solution containing 0.3 mM SDS was used at the beginning of the feed. The performance test results are shown in Figure 7 (d). During continuous operation, the water flux It still remains unchanged, its value is about 12kg / m ² -h; meanwhile, the blocking rate of sodium chloride is close to 100%.

The above film performance test results can further explain why the permeation flux in the membrane 1 and the membrane 2 is greatly reduced due to the addition of a surfactant (SDS) using the film wetting behavior. However, in the fully sparse film of the present invention, the initial value is always maintained. Relative water flux. As shown in Fig. 8 (a), it shows that the membrane holes of the hydrophobic membrane 1 or 2 are partially wetted by SDS, which makes the porosity blockage of the membrane becomes smaller, which results in a decrease in relative water flux. Due to its layered concave corner structure and low surface energy, the fully sparse film of the invention does not block the porosity of the film due to the addition of surfactant (SDS) to the feed, so the relative water flux can be maintained at all times. Effect of thin film distillation Will not decrease due to feed composition with low surface tension.

To sum up, the fully sparse film provided by the present invention contains zinc oxide nano particles and has a special layered concave re-ehtrant structure, and has a high C / Si ratio (40-60). The water contact angle of the fully sparse film is 152.8 ± 1.1 °, and the contact angle of ethanol is 110.3 ± 1.9 °; accordingly, the fully sparse film of the present invention has a very good anti-wetting effect. Secondly, compared to traditional films that have not been modified with zinc oxide nano-particles, the fully sparse films provided by the present invention are applied to direct contact membrane distillation (DCMD). The feed liquid has a very good anti-wetting effect. Secondly, for the liquid feed is a 1M NaCl solution containing 0.3 mM surfactant, in the process of thin film distillation using the thin film distillation module equipped with the thin film thin film distillation module of the present invention, the permeate flux can be maintained during the distillation process. And the sodium chloride barrier is also close to 100%, which proves that the fully sparse film of the present invention has a special effect of treating low-surface-tension saline-containing wastewater.

Although the present invention has been described with specific examples, it does not limit the scope of the present invention. As long as it does not deviate from the gist of the present invention, those skilled in the art understand that various modifications or changes can be made without departing from the intention and scope of the present invention. In addition, the abstract and the title are only used to assist the search of patent documents, and are not intended to limit the scope of rights of the present invention.

Claims (14)

A fully sparse film comprising a porous substrate having a pore size of 0.4-2 μm. The porous substrate includes glass fiber, a surface layer, and an interface layer. The interface layer is on the porous substrate and the surface. Between layers, the structure of the fully sparse film includes a layered hierarchical re-entrant structure and the carbon / silicon (C / Si) composition ratio of the fully sparse film is 40-60. According to the fully sparse film described in item 1 of the scope of patent application, the interface layer includes a film layer and a metal oxide, and the film layer covers the metal oxide; and the metal oxide is deposited on the porous substrate described above. on. According to the fully sparse film described in item 1 of the scope of patent application, the surface layer includes a fluorine-containing polymer, and the fluorine-containing polymer includes a copolymer of poly (vinylidene fluoride-co-hexafluoropropylene) ), Polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF). The fully sparse film according to item 3 of the scope of the patent application, the film layer includes a fluorosilane, and the fluorosilane includes perfluorodecyl triethoxysilane (FAS17) or polyhedral siloxane oligomer (POSS ). As described in claim 3, the metal oxide contains zinc oxide. As described in claim 3 of the patent application, the size of the metal oxide is 200-400 nm. As described in item 1 of the patent application, the completely thin film is assembled in a distillation device, which contains a distillation device with a desalination rate greater than 94%, an air-spaced thin film distillation device, or a scavenging thin film distillation. device. A method for manufacturing a fully sparse film, comprising the following steps: (1) using a chemical bath deposition method to deposit a metal oxide on a porous substrate, and the pore size of the porous substrate is 0.4-2 μm; (2) ) Covering a film layer on the metal oxide, thereby forming an organic-inorganic hybrid layer on the porous substrate; and (3) coating a fluorine-containing polymer on the organic-inorganic hybrid layer, thereby The completely sparse film is formed. The structure of the completely sparse film includes a layered hierarchical re-entrant structure and the carbon / silicon (C / Si) composition ratio of the completely sparse film is 40-60. According to the manufacturing method described in item 9 of the patent application scope, the porous substrate includes glass fibers. According to the manufacturing method described in claim 9 of the patent application scope, the metal oxide includes zinc oxide. According to the manufacturing method described in item 9 of the scope of patent application, the size of the metal oxide is 200-400 nm. According to the manufacturing method described in item 9 of the patent application scope, the film layer includes a fluorine-containing silane, and the fluorine-containing silane includes perfluorodecyltriethoxysilane (FAS17) or polyhedral siloxane oligomer (POSS) . According to the manufacturing method described in item 9 of the scope of patent application, the fluorine-containing polymer contains two Poly (vinylidene fluoride-co-hexafluoropropylene), polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF). A method for liquid desalination by thin film distillation, comprising the following steps: (1) providing a separation module, the separation module device is a fully sparse membrane as described in the application patent scope 1-7; (2) conveying a liquid Entering the above-mentioned separation module, the liquid contains seawater, an alkaline halide aqueous solution, wastewater containing a surfactant, or an aqueous solution with a surface tension of less than 30 mN / m; and (3) a thin film distillation process is performed to pass the liquid through, for example, a patent Completely sparse films as described in the range 1-7, thereby achieving a liquid desalting rate greater than 90%.