阅读说明：本技术 一种基于陶瓷膜的TiO2超疏水改性方法 (TiO based on ceramic film2Super-hydrophobic modification method ) 是由 贠延滨 董爽爽 李萌 于 2020-05-08 设计创作，主要内容包括：本发明属于膜技术领域,具体涉及基于陶瓷膜的TiO<Sub>2</Sub>超疏水改性方法。本发明的改性方法通过浸涂-煅烧方法得到二氧化钛种子层,并将其牢牢固定在氧化铝陶瓷衬底上；通过水热反应生成二氧化钛纳米棒；最后,将长有二氧化钛纳米棒的陶瓷膜浸泡在PDTS乙醇溶液中进行疏水化处理。通过本发明方法改性后可获得稳定的超疏水表面,与水接触角为152°,具有易清洁特性、优秀的热力和机械稳定性,将改性膜运用于膜蒸馏工艺3h,出水电导率、通量降低速率均小于原膜。(The invention belongs to the technical field of membranes, and particularly relates to TiO based on a ceramic membrane 2 A super-hydrophobic modification method. The modification method of the invention obtains the titanium dioxide seed layer by a dip-coating-calcining method and firmly fixes the titanium dioxide seed layer on the alumina ceramic substrate; titanium dioxide nano-rods are generated through hydrothermal reaction; and finally, soaking the ceramic membrane with the titanium dioxide nano rods in a PDTS ethanol solution for hydrophobization treatment. The stable super-hydrophobic surface can be obtained after modification by the method, the contact angle between the stable super-hydrophobic surface and water is 152 degrees, the stable super-hydrophobic surface has the characteristics of easy cleaning and excellent thermal and mechanical stability, the modified membrane is applied to a membrane distillation process for 3 hours, and the effluent conductivity and the flux reduction rate are both smaller than those of the original membrane.)

1. Ceramic membrane based TiO₂A superhydrophobic modification method, characterized in that the method comprises the steps of:

forming a seed layer, mixing tetrabutyl titanate, acetic acid and absolute ethyl alcohol, stirring to obtain a titanium dioxide seed solution, soaking the ceramic membrane into the titanium dioxide seed solution, then taking out the ceramic membrane, calcining for 2-3 hours at 400-500 ℃, and forming the seed layer on the surface of the ceramic membrane;

performing nano growth, namely mixing tetrabutyl titanate and a hydrochloric acid solution to obtain a growth solution, keeping the growth solution and the ceramic membrane with the surface formed with the seed layer in a high-pressure reaction kettle at the temperature of 130-150 ℃ for 14-16 hours, and forming titanium dioxide nanorods on the surface of the ceramic membrane;

and (3) performing hydrophobic treatment, namely immersing the ceramic membrane with the titanium dioxide nano-rod formed on the surface into a perfluorododecyl triethoxy silane ethanol solution for hydrophobic treatment.

2. Ceramic membrane based TiO according to claim 1₂The super-hydrophobic modification method is characterized in that in the step of forming a seed layer, tetrabutyl titanate is added into an absolute ethyl alcohol and an acetic acid solvent for stirring and dispersing treatment, wherein the volume ratio of the absolute ethyl alcohol to the acetic acid to the tetrabutyl titanate is 30-40: 4-5: 3 to 4.

3. Ceramic membrane based TiO according to claim 1 or 2₂The super-hydrophobic modification method is characterized in that in the step of forming the seed layer, tetrabutyl titanate, acetic acid and absolute ethyl alcohol are dispersed for 10-20 min at the temperature of 30-40 ℃ and the stirring speed of 1000-1500 r/min.

4. Ceramic membrane based TiO according to claim 1₂The super-hydrophobic modification method is characterized in that in the step of 'nano growth', 1-3 parts by volume of tetrabutyl titanate is added into 20-30 parts by volume of hydrochloric acid and 25-35 parts by volume of deionized water and uniformly mixed to obtain the growth solution, wherein the volume fraction of the hydrochloric acid is 30-40%％。

5. Ceramic membrane based TiO according to claim 1 or 4₂The super-hydrophobic modification method is characterized in that in the step of 'nano growth', tetrabutyl titanate is uniformly dispersed at the temperature of 20-30 ℃ and the stirring speed of 500-600 r/min for 20-25 min.

6. Ceramic membrane based TiO according to claim 1₂The super-hydrophobic modification method is characterized in that in the step of hydrophobic treatment, the volume fraction of the perfluorododecyl triethoxysilane ethanol solution is 1-2 vol%.

7. Ceramic membrane based TiO according to claim 1₂The super-hydrophobic modification method is characterized in that in the step of hydrophobic treatment, the ceramic membrane is soaked in a perfluorododecyl triethoxysilane ethanol solution for 20-24 hours.

8. Ceramic membrane based TiO according to claim 1₂The super-hydrophobic modification method is characterized in that in the step of hydrophobic treatment, a ceramic membrane is soaked in a perfluorododecyl triethoxysilane ethanol solution and then is subjected to heat preservation for 2-3 hours at the temperature of 120-130 ℃.

Technical Field

The invention belongs to the technical field of membranes, and particularly relates to TiO based on a ceramic membrane₂A super-hydrophobic modification method.

Background

The membrane distillation is a technology for mass transfer and heat transfer by combining membrane separation and distillation, and utilizes the vapor pressure at two sides of a membrane as a driving force to push feed liquid vapor at a high-temperature side to permeate through membrane holes to be condensed and collected at a low-temperature side. In the operation process of the membrane distillation process, the polymer membrane has the problems of easy pollution, poor stability, short service cycle and the like, so the research direction of the prior art is shifted to an inorganic membrane. Compared with a polymer membrane, the inorganic ceramic membrane has excellent thermal stability and chemical stability, and can be used in a harsher environment. The membrane material used in membrane distillation must be a hydrophobic membrane to solve the pollution problem generated in actual operation, so that the preparation of the super-hydrophobic membrane is a key link in the membrane distillation technology.

At present, hydrophobic modification of distillation membranes includes modification of the membrane bulk and the membrane surface, bulk modification is mainly performed by means of blending, and surface modification includes surface grafting and surface coating. The methods for obtaining a coating on the surface of a material to increase the roughness are generally: the sol-gel method can obtain films, rough coatings, nanocrystals, composite materials thereof and the like by a sol-gel research technology; chemical vapor deposition, which is a technique for depositing gaseous reactants on a substrate to form a non-volatile solid film, the surface morphology of which is mainly determined by the morphology of the substrate, but can also be controlled by selecting gaseous reactants and adjusting reaction conditions; the phase separation method has the advantages that factors such as the type of a solvent, temperature, solidification time and the like in the phase separation method process have large influence on the size and the shape of holes or bulges on a solid.

Disclosure of Invention

The invention aims to provide TiO based on ceramic membrane₂A super-hydrophobic modification method.

Ceramic membrane based TiO according to embodiments of the invention₂The super-hydrophobic modification method comprises the following steps:

(1) forming a seed layer, mixing tetrabutyl titanate, acetic acid and absolute ethyl alcohol, stirring to obtain a titanium dioxide seed solution, soaking the ceramic membrane into the titanium dioxide seed solution, then taking out the ceramic membrane, calcining for 2-3 hours at 400-500 ℃, and forming the seed layer on the surface of the ceramic membrane;

(2) growing nano, namely mixing tetrabutyl titanate and a hydrochloric acid solution to serve as a growth solution, and carrying out heat preservation on the growth solution and a ceramic membrane with a surface formed seed layer in a high-pressure reaction kettle at 130-150 ℃ for 14-16 hours to form a titanium dioxide nanorod on the surface of the ceramic membrane;

(3) and (3) performing hydrophobic treatment, namely immersing the ceramic membrane with the titanium dioxide nano-rod formed on the surface into a perfluorododecyl triethoxy silane ethanol solution for hydrophobic treatment.

TiO based ceramic membranes according to the invention₂The super-hydrophobic modification method comprises the following steps that (1) a titanium dioxide seed layer is formed on the surface of a ceramic membrane, so that active sites are provided for the subsequent growth of titanium dioxide nanorods, and the binding force between a substrate and the nanorods is increased; in the step (2), regular titanium dioxide nanorods are obtained on the ceramic membrane, so that the roughness of the substrate is increased; in the step (3), a layer of low surface energy coating is coated on the ceramic membrane on which the titanium dioxide nano-rods grow, so that the surface energy is reduced, the hydrophobicity of the ceramic membrane is increased, the long-term self-cleaning effect is realized, and the problems of membrane pollution, wetting and the like in the process operation are reduced.

Ceramic membrane based TiO according to embodiments of the invention₂In the step of 'forming a seed layer', tetrabutyl titanate is added into an absolute ethyl alcohol and an acetic acid solvent for stirring and dispersing treatment, wherein the volume ratio of the absolute ethyl alcohol to the acetic acid to the tetrabutyl titanate is 30-40: 4-5: 3 to 4.

According to the invention, the anhydrous ethanol, the acetic acid and the tetrabutyl titanate are mixed according to a specific proportion, so that the tetrabutyl titanate is slowly hydrolyzed to form colorless and transparent sol, and the phenomenon that the tetrabutyl titanate is hydrolyzed too fast to generate precipitate and block membrane pores in the membrane modification process is effectively avoided.

Ceramic membrane based TiO according to embodiments of the invention₂In the step of 'forming seed layer', tetrabutyl titanate, acetic acid and absolute ethyl alcohol are stirred at the temperature of 30-40 ℃ and the stirring speed of 1000-1500 r/miDispersing for 10-20 min under n.

If the dispersion temperature of tetrabutyl titanate is too low, the hydrolysis rate becomes slow; if the dispersion speed is too low, the hydrolysis of tetrabutyl titanate is not sufficient and uniform; if the hydrolysis time is reduced, the hydrolysis of tetrabutyl titanate is incomplete. According to the invention, tetrabutyl titanate, acetic acid and absolute ethyl alcohol are dispersed for 10-20 min at the temperature of 30-40 ℃ and the stirring speed of 1000-1500 r/min to obtain uniform and transparent sol, so that a uniform seed layer covering the surface of the ceramic membrane is obtained, and the binding force between the substrate and the nanorods is increased.

And after the ceramic membrane is coated with the seed layer solution, calcining the seed layer solution in a muffle furnace, which is favorable for the close combination of the seed layer on the ceramic membrane, and if the calcining temperature is low and the calcining time is short, the seed layer is easy to fall off on the ceramic membrane, which is not favorable for the growth of the titanium dioxide nano-rods.

Ceramic membrane based TiO according to embodiments of the invention₂In the step of 'nano growth', 1-3 parts of tetrabutyl titanate is added into 20-30 parts of hydrochloric acid and 25-35 parts of deionized water according to the volume parts and uniformly mixed to obtain the growth liquid, wherein the volume fraction of the hydrochloric acid is 30-40%.

Ceramic membrane based TiO according to embodiments of the invention₂The super-hydrophobic modification method comprises the step of nano-growth, wherein tetrabutyl titanate is uniformly dispersed at the temperature of 20-30 ℃ and the stirring speed of 500-600 r/min for 20-25 min.

In the preparation of the growth liquid, tetrabutyl titanate forms a one-dimensional nanorod structure under the acidic condition of hydrochloric acid, and meanwhile, the growth liquid can be further uniformly mixed at a proper dispersion temperature, speed and time, so that titanium dioxide is promoted to form uniform one-dimensional nano in a closed environment.

Ceramic membrane based TiO according to embodiments of the invention₂In the step of super-hydrophobic modification and hydrophobic treatment, the volume fraction of the perfluorododecyl triethoxysilane (PDTS) ethanol solution is 1-2 vol%.

Ceramic membrane based TiO according to embodiments of the invention₂Super-hydrophobic modification methodIn the step of hydrophobic treatment, the ceramic membrane is soaked in a perfluorododecyl triethoxysilane ethanol solution for 20-24 hours.

Ceramic membrane based TiO according to embodiments of the invention₂In the step of super-hydrophobic modification, after a ceramic membrane is soaked in a perfluorododecyl triethoxysilane ethanol solution, the ceramic membrane is kept at 120-130 ℃ for 2-3 hours.

The invention has the beneficial effects that:

the contact angle between the modified membrane obtained by the modification method and water is more than 150 degrees, the modified membrane has a stable super-hydrophobic surface, is easy to clean, and can solve the pollution problem in membrane distillation operation to a certain extent; based on TiO₂The ceramic membrane modified by the nano-rods has excellent thermal and mechanical stability and can resist acid and alkali; the modified membrane is applied to a membrane distillation process for 3 hours, and the conductivity and flux reduction rate of effluent are both smaller than those of the original membrane.

Drawings

FIG. 1 shows AHC-TiO₂(NR) -PDTS modified membrane surface SEM and effect picture;

FIG. 2 shows the water surface contact angles of AHC-P and TN-AHC-P films;

FIG. 3 shows the pore size distribution of AHC and TN-AHC-P membranes;

FIG. 4 shows the conductivity and permeate flux changes for AHC-P and TN-AHC-P membranes in a membrane distillation run, wherein (a) is the AHC-P membrane and (b) is the TN-AHC-P membrane;

FIG. 5 shows the change of contact angle of TN-AHC-P film when soaked in acidic deionized water.

Detailed Description

Preparation of example 1

Step 1: preparing a seed layer

Weighing 30-40 mL of absolute ethyl alcohol, 4-5 mL of acetic acid and 3-4 mL of tetrabutyl titanate according to the volume parts of tetrabutyl titanate, acetic acid and absolute ethyl alcohol, mixing, dispersing for 10-20 min at the temperature of 30-40 ℃ and the stirring speed of 1000-1500 r/min, and stirring to obtain a transparent colloid.

And fully soaking the alumina ceramic membrane in a seed layer solution of tetrabutyl titanate, after the alumina ceramic membrane is uniformly soaked, slowly lifting out the liquid level at a constant speed, and calcining the liquid level in a muffle furnace at the temperature of 400-500 ℃ for 2-3 hours.

The above process was repeated 2 times to obtain a "TS-AHC film" with a seed layer attached.

In this example, tetrabutyl titanate is subjected to stirring dispersion treatment, i.e. tetrabutyl titanate is added to a solvent of anhydrous ethanol and acetic acid, and the tetrabutyl titanate, acetic acid and anhydrous ethanol are mixed according to volume portion, preferably, 30mL of anhydrous ethanol, 4mL of acetic acid, 3mL of tetrabutyl titanate, or 35mL of anhydrous ethanol, 4.5mL of acetic acid, 3.5mL of tetrabutyl titanate, or 40mL of anhydrous ethanol, 5mL of acetic acid, 4mL of tetrabutyl titanate.

Tetrabutyl titanate, acetic acid and absolute ethyl alcohol are mixed at the temperature of 30-40 ℃, preferably at the temperature of 30 ℃, 35 ℃ and 40 ℃.

The stirring speed is 1000-1500 r/min, preferably 1000r/min, 1200r/min, 1400r/min and 1500 r/min.

The stirring time is 10-20 min, preferably 10min, 15min and 20 min.

The alumina ceramic membrane is calcined in a muffle furnace at the temperature of 400 ℃, 420 ℃, 450 ℃, 480 ℃ and 500 ℃.

The alumina ceramic membrane is placed in a muffle furnace for calcination, and the time is preferably 2h, 2.5h and 3 h.

Step 2: modified TiO₂Nano-rod

Adding tetrabutyl titanate into a hydrochloric acid solution, and stirring and dispersing at the temperature of 20-30 ℃, at the stirring speed of 500-600 r/min and for 20-25 min to obtain a growth solution.

Will be attached with TiO₂And simultaneously transferring the ceramic membrane and the growth liquid of the seed layer into a high-pressure reaction kettle with 100mL of polytetrafluoroethylene as a lining, and preserving the heat for 14-16 h at the temperature of 130-150 ℃. And when the temperature is reduced to room temperature, taking out the sample, cleaning surface impurities by using deionized water, and then transferring to a muffle furnace for annealing at the annealing temperature of 300-400 ℃ for 1-2 h to obtain the TN-AHC film.

In the embodiment, tetrabutyl titanate and a hydrochloric acid solution are mixed according to the volume, wherein 20-30 mL of hydrochloric acid (the volume fraction of hydrochloric acid is 30% -40%) is added into 25-35 mL of deionized water to obtain the hydrochloric acid solution, and 1-3 mL of tetrabutyl titanate, preferably 1mL of tetrabutyl titanate, 2mL of tetrabutyl titanate and 3mL of tetrabutyl titanate, are added into the hydrochloric acid solution.

The tetrabutyl titanate is dispersed in hydrochloric acid solution, preferably at 20 deg.C, 25 deg.C, and 30 deg.C.

The tetrabutyl titanate is dispersed in the hydrochloric acid solution, and the stirring speed is preferably 500r/min, 600r/min and 550 r/min.

Dispersing tetrabutyl titanate in hydrochloric acid solution, and stirring for 20min, 22min, and 25 min.

The temperature of the ceramic membrane and the growth liquid in the high-pressure reaction kettle is preferably 130 ℃, 140 ℃ and 150 ℃.

The temperature of the ceramic membrane and the growth liquid in the high-pressure reaction kettle is preferably kept for 14h, 15h and 16 h.

The ceramic membrane is annealed in a muffle furnace, preferably at 300 ℃, 350 ℃ and 400 ℃.

The ceramic membrane is annealed in a muffle furnace, and the annealing time is preferably 1h, 1.5h and 2 h.

And step 3: hydrophobizing treatment of fluorosilanes

And (3) immersing the TN-AHC membrane into a 1-2 vol% PDTS ethanol solution, soaking for 20-24 h, taking out, transferring into an oven, and preserving heat at the temperature of 120-130 ℃ for 2-3 h to obtain the TN-AHC-P membrane.

In this embodiment, the TN-AHC membrane is immersed in a 1-2 vol% PDTS ethanol solution, and the concentration of the PDTS ethanol solution is preferably 1 vol%, 1.5 vol%, or 2 vol%.

The TN-AHC membrane is immersed in the PDTS ethanol solution for 20h, 22h and 24h preferably.

The heat preservation temperature in the oven is preferably 120 ℃, 125 ℃ and 130 ℃.

The temperature keeping time in the oven is preferably 2h, 2.5h and 3 h.