Tubular ceramic membrane surface hydrophobic modification method, hydrophobic modified membrane and tubular ceramic membrane

Abstract

The invention relates to the technical field of gas separation membrane materials in a carbon capture technology, in particular to a tubular ceramic membrane surface super-hydrophobic modification method for a carbon dioxide capture membrane contactor, a hydrophobic modified membrane and a tubular ceramic membrane. The tubular ceramic membrane surface hydrophobic modification method comprises the following steps: step B, forming a SiO2 coarsening layer on the surface of a tubular ceramic membrane substrate; step C, forming a polydopamine intermediate bridging layer on the surface of the SiO2 coarsening layer; and step D, forming a polydimethylsiloxane hydrophobic layer on the polydopamine intermediate bridging layer. According to the super-hydrophobic coating disclosed by the invention, the bonding strength and durability of the super-hydrophobic coating are remarkably enhanced by the polydopamine middle layer, and the problem of weak bonding force between a functional layer and a matrix in a traditional super-hydrophobic coating is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of gas separation membrane material technology in carbon capture technology, and particularly to a method for superhydrophobic modification of the surface of a tubular ceramic membrane for a carbon dioxide capture membrane contactor, a hydrophobic modified membrane, and a tubular ceramic membrane. Background Technology

[0002] With increasing global attention to climate change, carbon capture, utilization, and storage (CCLS) technologies are considered a key approach to reducing industrial carbon dioxide emissions. Among numerous carbon capture technologies, membrane absorption technology, combining the advantages of membrane separation and chemical absorption, has demonstrated great potential in the field of carbon capture. Compared with traditional absorption towers, gas separation technology based on membrane contactors offers advantages such as compact equipment, simple operation and installation, and high mass transfer efficiency.

[0003] In membrane contactors, the performance of the membrane material is crucial, being a core component. Ceramic membranes, due to their inherent high strength, excellent chemical inertness, good thermal stability, and long service life, are considered superior to organic polymer membranes in handling high-temperature and corrosive environments such as power plant flue gas. However, unlike the natural hydrophobicity of organic polymer membranes, commercially prepared ceramic membranes (such as alumina and zirconia membranes) typically have surfaces and pore walls rich in hydroxyl groups, exhibiting hydrophilicity. This results in additional diffusion resistance for mass transfer through the ceramic membrane pores. When the pores are wetted by the liquid absorbent, the mass transfer resistance becomes significant, leading to a deterioration in CO2 absorption flux during long-term operation. This phenomenon, where the absorbent wets the membrane pores through capillary action, is called membrane wetting. Therefore, hydrophobic modification of the ceramic membrane surface is key to ensuring its use in membrane contactors and achieving long-term stable operation.

[0004] According to existing literature, the main methods for hydrophobic modification of ceramic membranes include graft polymerization, template method, and chemical vapor deposition. Among these, graft polymerization involves high-cost silanes, and its hydrophobic performance deteriorates over time. The template method uses the desired characteristic structure surface as a template, coating the precursor onto the template surface, followed by demolding after molding; however, the demolding process is cumbersome. Finally, chemical vapor deposition deposits the precursor material in a gaseous state onto a solid surface under specific temperature and pressure to form a thin film; this method is complex and costly. Summary of the Invention

[0005] I. Technical problems to be solved The present invention aims to at least partially solve one of the above-mentioned technical problems.

[0006] II. Technical Solution The first aspect of this invention provides a method for superhydrophobic modification of the surface of a tubular ceramic membrane. This method includes: Step B: A SiO2 roughening layer is formed on the surface of the tubular ceramic membrane substrate; Step C: A polydopamine intermediate bridging layer is formed on the surface of the SiO2 roughened layer; Step D: A polydimethylsiloxane hydrophobic layer is formed on the polydopamine intermediate bridging layer.

[0007] In some embodiments of the present invention, step C includes: sub-step C1, preparing a dopamine Tris-citric acid buffer solution; wherein the concentration of the dopamine Tris-citric acid buffer solution is 1~10 mg / mL, and the pH of the solution is adjusted to 8~9; sub-step C2, immersing the tubular ceramic membrane substrate treated in step B into the dopamine Tris-citric acid buffer solution and reacting it with ultrasonic vibration at room temperature for more than 6 hours; sub-step C3, rinsing and drying the tubular ceramic membrane substrate obtained in sub-step C2, thereby forming a polydopamine intermediate bridging layer on the surface of the SiO2 roughened layer.

[0008] In some embodiments of the present invention, sub-step C1 includes: weighing 4.8456 g of tris(hydroxymethyl)aminomethane, dissolving it in distilled water, adding 2 mL of citric acid solution, and adjusting the volume to 1 L to obtain a Tris-CA buffer solution with pH=8.5; taking 500 mL of the Tris-CA buffer solution, adding 2.5 g of dopamine hydrochloride, and preparing a 5 mg / mL dopamine Tris-citric acid buffer solution; sub-step C2 includes: immersing the tubular ceramic membrane substrate treated in sub-step C1 into the Tris-citric acid buffer solution and reacting it with ultrasonic vibration at room temperature for 8 hours; sub-step C3 includes: rinsing the tubular ceramic membrane substrate treated in sub-step C2 with deionized water and drying it, thereby forming a polydopamine intermediate bridging layer on the surface of the SiO2 roughened layer.

[0009] In some embodiments of the present invention, step D includes: sub-step D1, preparing a PDMS solution; wherein the PDMS solution is prepared by mixing Dow Corning Sylgard 184 elastic substrate, curing agent and n-hexane, the mass ratio of elastic substrate to curing agent is 10:1, and the mass concentration of PDMS in the solution is 2~10%; sub-step D2, immersing the tubular ceramic membrane substrate treated in step C into the PDMS solution and then taking it out, the immersion time is 4~6h; sub-step D3, subjecting the tubular ceramic membrane substrate treated in sub-step D2 to heat treatment, wherein the heat treatment temperature is 60~120℃ and the time is 2~4h.

[0010] In some embodiments of the present invention, step B includes: sub-step B1, preparing a suspension slurry; wherein the suspension slurry is formed by dispersing SiO2 nanoparticles in a mixed solvent of ethanol and methanol, the SiO2 nanoparticles being gaseous SiO2 particles with a particle size of 5-20 nm; the pH value being between 8 and 9; sub-step B2, depositing a SiO2 precursor on the surface of a tubular ceramic membrane substrate; the tubular ceramic membrane substrate is immersed and pulled in the suspension slurry, thereby depositing the SiO2 precursor on the surface of the tubular ceramic membrane substrate; sub-step B3, sintering and curing to form a SiO2 roughening layer; the tubular ceramic membrane substrate with the SiO2 precursor deposited on its surface is sintered, thereby forming a cured SiO2 roughening layer on the surface of the tubular ceramic membrane.

[0011] In some embodiments of the present invention, sub-step B1 includes: dispersing silica particles in a mixed solvent of anhydrous ethanol and methanol to form a mixed solution; wherein the volume ratio of anhydrous ethanol to methanol in the mixed solvent is 9:1; the mass ratio of silica particles to the mixed solvent is 1:10; adding ammonia to adjust the pH value of the mixed solution to between 8 and 9; ultrasonically mixing the mixed solution after pH adjustment with an ultrasonic power of 450-600W for 1-2 hours to obtain a suspension slurry; sub-step B2 includes: repeating the immersion and lifting process several times, each immersion and lifting process including: vertically immersing the ceramic membrane into the slurry, lifting it at a speed of 5-10 mm / s after 20-30 seconds, and letting it stand at room temperature for 10-20 minutes; sub-step B3 includes: first pre-baking in an oven at 60-80℃ for 1-2 hours, then placing it in a muffle furnace, raising it to 400℃ at a rate of 3-6℃ / min, holding it at that temperature for 2-4 hours, and then cooling it to room temperature with the furnace to form a stable SiO2 layer.

[0012] In some embodiments of the present invention, step B is preceded by step A, in which the tubular ceramic membrane substrate is sequentially ultrasonically cleaned in deionized water, ethanol, and acetone, and then dried for later use; wherein, during ultrasonic cleaning, the ultrasonic power is 540~750W and the cleaning time is 20~30min; during drying, the drying temperature is 60~80℃ and the drying time is 6~8h; the tubular ceramic membrane substrate is a single-channel tubular membrane with an outer diameter of 12~16mm, an inner diameter of 8~12mm, and a length of 100~600mm, and the main component of the membrane material is aluminum oxide with a pore size of 0.03~1μm; the composition of the tubular ceramic membrane substrate is aluminum oxide; its pore size is between 10~1000nm.

[0013] A second aspect of the present invention provides a hydrophobic modified membrane. The hydrophobic modified membrane comprises: a SiO2 roughened layer formed on the surface of a substrate; a polydopamine intermediate bridging layer formed on the surface of the SiO2 roughened layer; and a polydimethylsiloxane hydrophobic layer formed on the polydopamine intermediate bridging layer.

[0014] In some embodiments of the present invention, the substrate is a tubular ceramic membrane substrate; the surface static water contact angle of the hydrophobic modified membrane is ≥150° and the roll-off angle is ≤10°; the hydrophobic modified membrane is applied in a carbon dioxide capture membrane contactor.

[0015] A third aspect of the present invention provides a tubular ceramic membrane. The tubular ceramic membrane includes: a tubular ceramic membrane substrate; and a hydrophobically modified membrane, including: a SiO2 roughening layer formed on the surface of the tubular ceramic membrane substrate; a polydopamine intermediate bridging layer formed on the surface of the SiO2 roughening layer; and a polydimethylsiloxane hydrophobic layer formed on the polydopamine intermediate bridging layer.

[0016] III. Beneficial Effects As can be seen from the above technical solution, the present invention has at least one of the following beneficial effects compared to the prior art: (1) In this invention, the polydopamine interlayer significantly enhances the bonding strength and durability of the superhydrophobic coating. The abundant catechol groups in the polydopamine molecule can form strong hydrogen bonds with the SiO2 layer and covalently crosslink with the PDMS layer, effectively solving the problem of weak bonding between the functional layer and the substrate in traditional superhydrophobic coatings. Experimental verification shows that the prepared superhydrophobic coating can still maintain complete hydrophobic properties and a contact angle of more than 150° after being subjected to harsh conditions such as water rinsing and mechanical friction, demonstrating excellent mechanical stability and service life.

[0017] It is important to note that in this invention, it is not simply about "having a layer of PDA," but rather about controlling the PDA layer to form a continuous network within a nanometer-thickness (typically between 10 and 50 nm) through specific pH and reaction time, rather than forming a non-uniform, blocky deposition. This controlled thickness ensures that the intermediate bridging layer neither forms an excessively thick, brittle interface leading to cracking and peeling, nor is it so thin that it cannot provide sufficient binding sites for PDMS. In the subsequently cured polydimethylsiloxane layer, PDMS is no longer "applied as a whole sheet," but rather undergoes interfacial coupling with this PDA network, resulting in higher erosion resistance and durability.

[0018] (2) In this invention, instead of the conventional method of "directly brushing a layer of PDMS onto a ceramic film," PDMS is dip-coated and cured onto a surface with PDA activity to obtain a continuous, dense, elastic, low surface energy layer. The technical effects are reflected in three aspects: ① The cured layer has extremely low surface energy, which makes the membrane surface exhibit typical superhydrophobic behavior (high contact angle, low roll-off angle), reducing the residence of liquid in the pores; ② After being bridged by PDA, the PDMS layer exhibits significantly improved adhesion and peel resistance. It is not easy to swell and peel off in alkaline amine absorbents and high-temperature environments, thus avoiding the problem of "peeling after a period of operation" of traditional PDMS coated films. ③PDMS's flexible buffering properties against thermal stress and water flow erosion stress are superior to those of existing rigid and brittle fluorinated silane self-assembled layers. As a result, the membrane maintains a stable and effective separation interface under long-term carbon dioxide absorption conditions.

[0019] (3) In this invention, a stable and reliable multilayer superhydrophobic structure is constructed on the surface of a ceramic film using a three-step method. First, smaller gaseous SiO2 nanoparticles are used to form a uniform nanoscale rough structure on the substrate surface by precisely controlling the impregnation-pulling speed and sintering temperature. Then, the spontaneous polymerization of polydopamine in a weakly alkaline buffer solution is utilized to construct an intermediate bridging layer with strong adhesion. Finally, a low surface energy hydrophobic coating layer is formed by adjusting the ratio of PDMS to curing agent and the curing conditions. This multilayer structure design ensures a strong bond between the functional layers and significantly improves the stability of the superhydrophobic coating.

[0020] (4) The superhydrophobic ceramic membrane prepared in this invention exhibits excellent hydrophobic properties and self-cleaning ability. Test results show that its static water contact angle can reach more than 150° and the roll-off angle is less than 10°, fully meeting the superhydrophobic standard. This is mainly due to the combined effect of the uniform micro-nano structure constructed by SiO2 nanoparticles and the low surface energy characteristics of PDMS, which makes water droplets exhibit a typical Cassie-Baxter state on the membrane surface, greatly reducing surface adhesion. In practical applications, this characteristic makes it difficult for pollutants to adhere to the membrane surface, and even if pollutants are deposited, they are easily carried away by the rolling water droplets, exhibiting excellent self-cleaning effect.

[0021] (5) The preparation process of the present invention has outstanding advantages such as mild conditions, controllable parameters, and wide applicability. The entire process is carried out under relatively mild conditions, with the highest processing temperature not exceeding 400°C, and avoids the investment in complex equipment. In addition, the raw materials used are all commercially available, and the solvents can be recycled, which has good prospects for industrial application and economic benefits. Attached Figure Description

[0022] Figure 1 This is a flowchart of the superhydrophobic modification method for the surface of a tubular ceramic membrane according to an embodiment of the present invention. Detailed Implementation

[0023] To enhance the anti-wetting ability and long-term operational stability of carbon capture in ceramic membranes, this invention involves sintering gaseous SiO2 nanoparticles onto the ceramic membrane surface and introducing PDA as an intermediate layer, followed by adhering a PDMS coating to the surface. This method improves the bonding ability between the organic hydrophobic coating and the ceramic membrane surface, while the deposited SiO2 nanoparticles maintain the original gas mass transfer flux, reduce mass transfer resistance, and improve the carbon capture efficiency of the ceramic membrane.

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0025] The first aspect of this invention provides a method for superhydrophobic modification of the surface of a tubular ceramic membrane. In an exemplary embodiment of this invention, a method for superhydrophobic modification of the surface of a tubular ceramic membrane for use in a carbon dioxide capture membrane contactor is provided. Those skilled in the art will understand that, in addition to its use in carbon dioxide capture membrane contactors, the method for superhydrophobic modification of the surface of a tubular ceramic membrane of this invention can also be applied to other application scenarios, which will not be elaborated here.

[0026] Figure 1 This is a flowchart illustrating the superhydrophobic modification method for the surface of a tubular ceramic membrane according to an embodiment of the present invention. Figure 1 As shown, the superhydrophobic modification method for the surface of the tubular ceramic membrane in this embodiment includes: Step A: Pre-cleaning of the tubular ceramic membrane substrate; Step B: A SiO2 roughening layer is formed on the surface of the tubular ceramic membrane substrate; Step C: A polydopamine intermediate bridging layer is formed on the surface of the SiO2 roughened layer; Step D: A polydimethylsiloxane hydrophobic layer is formed on the polydopamine intermediate bridging layer.

[0027] This invention constructs a stable and reliable multilayer superhydrophobic structure on a ceramic film surface using a three-step method. First, smaller fumed SiO2 nanoparticles are used, and a uniform nanoscale rough structure is formed on the substrate surface by precisely controlling the impregnation-pulling speed and sintering temperature. Then, utilizing the spontaneous polymerization property of polydopamine in a weakly alkaline buffer solution, a highly adhesive intermediate bridging layer is constructed. Finally, by adjusting the ratio of PDMS to n-hexane and the curing conditions, a low surface energy hydrophobic coating layer is formed. This multilayer structure design ensures strong bonding between the functional layers, significantly improving the stability of the superhydrophobic coating.

[0028] The following provides a detailed description of each step in this embodiment.

[0029] In this embodiment, the tubular ceramic membrane substrate is a single-channel tubular membrane with an outer diameter of 12-16 mm, an inner diameter of 8-12 mm, and a length of 100-600 mm. The membrane material is mainly composed of aluminum oxide and silicon dioxide, with a pore size of 0.03-1 μm.

[0030] In step A of this embodiment, the tubular ceramic membrane substrate is ultrasonically cleaned in deionized water, ethanol, and acetone in sequence, and then dried for later use. During ultrasonic cleaning, the ultrasonic power is 540~750W and the cleaning time is 20~30min. During drying, the drying temperature is 60~80℃ and the drying time is 6~8h.

[0031] Those skilled in the art will understand that pre-cleaning ensures a clean surface and unobstructed pores on the tubular ceramic membrane substrate, resulting in more uniform silica deposition, PDA film formation, and PDMS curing, thus preventing localized delamination. However, this invention is not limited thereto. In other embodiments of this invention, if the surface of the tubular ceramic membrane substrate is sufficiently clean, this step can be omitted, and the invention can still be achieved.

[0032] In step B of this embodiment, a SiO2 roughening layer is formed on the surface of the tubular ceramic film substrate. Step B further includes: Sub-step B1, preparing the suspension slurry, specifically includes: Silica particles are dispersed in a mixed solvent of anhydrous ethanol and methanol to form a mixed solution; wherein the volume ratio of anhydrous ethanol to ethylene glycol in the mixed solvent is 9:1; and the mass ratio of silica particles to the mixed solvent is 1:10. Adjust the pH of the mixed solution to between 8 and 9 by adding ammonia dropwise. The pH-adjusted mixed solution was ultrasonically mixed for 1-2 hours using an ultrasonic power of 450-600W to obtain a suspension slurry. The suspension slurry is formed by dispersing SiO2 nanoparticles in a mixed solvent of ethanol and ethylene glycol. The SiO2 nanoparticles are gaseous SiO2 particles with a particle size of 5-20 nm and a pH value between 8 and 9. Sub-step B2 involves depositing a SiO2 precursor on the surface of a tubular ceramic film substrate; Specifically, this includes repeating the immersion and lifting process several times. Each immersion and lifting process includes: vertically immersing the ceramic membrane into the slurry, lifting it at a speed of 5-10 mm / s after 20-30 seconds, and letting it stand at room temperature for 10-20 minutes.

[0033] Sub-step B3 involves sintering and solidification to form a coarsened SiO2 layer. Specifically, the process involves: first, pre-drying in an oven at 60-80℃ for 1-2 hours, then placing it in a muffle furnace and heating it to 400℃ at a rate of 3-6℃ / min, holding it at that temperature for 2-4 hours, and then cooling it to room temperature with the furnace to form a stable SiO2 layer.

[0034] In this embodiment, it is not simply a matter of "creating a layer of SiO2 on the surface of a ceramic film," but rather constructing a surface morphology with micro- and nano-scale roughness using nanoscale silica particles, and then fixing this morphology to the surface of a ceramic substrate by high-temperature sintering. This rough layer provides the micro- and nano-structural basis required for superhydrophobicity, resulting in a typical composite gas-solid interface on the final surface. On the other hand, this rough layer provides a high specific surface area and a large number of adsorption / complexation sites for subsequent PDA attachment, improving the spreading uniformity of the bridging layer.

[0035] It is important to note that, because this layer and the ceramic matrix form a "quasi-inorganic" bond after sintering, rather than relying solely on physical adsorption, its mechanical strength and chemical corrosion resistance are far superior to the fragile monolayers in existing technologies that rely on the self-assembly of fluorinated silanes. Therefore, this roughened layer is not merely decorative roughness, but a stable "long-life skeleton layer" that can withstand high-alkali environments and high-shear erosion. This is precisely what is lacking in existing CO2 membrane contactors using polypropylene membranes, PTFE membranes, or fluorinated silane-treated ceramic membranes.

[0036] Furthermore, a suspension slurry is obtained through ultrasonic dispersion, and SiO2 precursors are formed through multiple impregnation and pulling processes. These controlled processes avoid nanoparticle aggregation, cracking, or local detachment, ensuring the continuity and stability of the roughened layer; at the same time, they provide high reproducibility, enabling the same method to stably replicate similar roughened morphologies on different batches of membrane tubes with different geometries.

[0037] In step C of this embodiment, a polydopamine intermediate bridging layer is formed on the surface of the SiO2 roughened layer. Step C further includes: Sub-step C1: Prepare a dopamine Tris-citric acid buffer solution with a concentration of 1~10 mg / mL and adjust the pH of the solution to 8~9. Specifically, 4.8456 g of tris(hydroxymethyl)aminomethane was weighed and dissolved in distilled water, 2 mL of citric acid solution was added, and the volume was adjusted to 1 L to obtain a Tris-CA buffer solution with pH=8.5; 500 mL of the Tris-CA buffer solution was taken and 2.5 g of dopamine hydrochloride was added to prepare a 5 mg / mL dopamine Tris-citric acid buffer solution.

[0038] Sub-step C2 involves immersing the tubular ceramic membrane substrate treated in step B into a dopamine Tris-citric acid buffer solution and reacting it with ultrasonic vibration at room temperature for more than 6 hours. Specifically, the tubular ceramic membrane substrate treated in sub-step C1 was immersed in Tris-citric acid buffer solution and subjected to ultrasonic oscillation at room temperature for 8 hours.

[0039] In sub-step C3, the tubular ceramic film substrate obtained in sub-step C2 is rinsed and dried to form a polydopamine intermediate bridging layer on the surface of the SiO2 roughened layer.

[0040] Specifically, the tubular ceramic film substrate treated in sub-step C2 is rinsed with deionized water and dried to form a polydopamine intermediate bridging layer on the surface of the SiO2 roughened layer.

[0041] In this embodiment, the polydopamine interlayer significantly enhances the bonding strength and durability of the superhydrophobic coating. The abundant catechol groups in the polydopamine molecule can form strong hydrogen bonds with the SiO2 layer and covalently crosslink with the PDMS layer, effectively solving the problem of weak bonding between the functional layer and the substrate in traditional superhydrophobic coatings. Experimental verification shows that the prepared superhydrophobic coating maintains its complete hydrophobic properties and a contact angle of over 150° even after undergoing rigorous testing under conditions such as water rinsing and mechanical friction, demonstrating excellent mechanical stability and service life.

[0042] It is important to note that in this embodiment, it is not simply about "having a layer of PDA," but rather about controlling the PDA layer to form a continuous network within a nanometer-thickness (typically between 10 and 50 nm) through specific pH and reaction time, rather than forming a non-uniform, blocky deposition. This controlled thickness ensures that the intermediate bridging layer neither forms an excessively thick, brittle interface leading to cracking and peeling, nor is it too thin to provide sufficient binding sites for PDMS. In the subsequently cured polydimethylsiloxane layer, PDMS is no longer "applied as a whole sheet," but rather undergoes interfacial coupling with this PDA network, resulting in higher erosion resistance and durability.

[0043] In step D of this embodiment, a polydimethylsiloxane hydrophobic layer is formed on the polydopamine intermediate bridging layer. Step D further includes: Sub-step D1: Prepare the PDMS solution; The PDMS solution is prepared by mixing Dow Corning Sylgard 184 elastic substrate, curing agent and n-hexane, with the mass ratio of elastic substrate to curing agent being 10:1, and the mass concentration of PDMS in the solution being 2-10%. Sub-step D2: Immerse the tubular ceramic membrane substrate treated in step C into PDMS solution and then remove it. The immersion time is 4-6 hours. Sub-step D3 involves heat-treating the tubular ceramic film substrate after sub-step D2, wherein the heat treatment temperature is 60~80℃ and the time is 2~4h.

[0044] In this embodiment, instead of the conventional method of "directly brushing a layer of PDMS onto a ceramic film," PDMS is dip-coated and cured onto a surface with PDA activity to obtain a continuous, dense, elastic, low surface energy layer. The technical advantages are reflected in three aspects: ① The cured layer has extremely low surface energy, which makes the membrane surface exhibit typical superhydrophobic behavior (high contact angle, low roll-off angle), reducing the residence of liquid in the pores; ② After being bridged by PDA, the PDMS layer exhibits significantly improved adhesion and peel resistance. It is not easy to swell and peel off in alkaline amine absorbents and high-temperature environments, thus avoiding the problem of "peeling after a period of operation" of traditional PDMS coated films. ③PDMS provides a more flexible buffer against thermal stress and water flow erosion stress than existing rigid and brittle fluorinated silane self-assembled layers. As a result, the membrane maintains a stable and effective separation interface under long-term carbon dioxide absorption conditions.

[0045] In summary, this embodiment first constructs a robust vapor-phase SiO2 layer, then utilizes the strong adhesion of PDA as an intermediate layer, and finally introduces a hydrophobic PDMS layer, forming a composite structure with hydrophobic stability far superior to traditional coating methods. This structure effectively resists the chemical erosion and physical scouring of alkaline absorbents, enabling the superhydrophobic ceramic membrane to exhibit excellent durability during CO2 capture, significantly delaying membrane wetting, and ensuring the long-term, efficient, and stable operation of the membrane contactor.

[0046] Furthermore, test results show that its static water contact angle can reach over 150° and its roll-off angle is less than 10°, fully meeting the superhydrophobic standard. This is mainly due to the combined effect of the uniform micro-nano structure constructed by SiO2 nanoparticles and the low surface energy characteristics of PDMS, which causes water droplets to exhibit a typical Cassie-Baxter state on the membrane surface, greatly reducing surface adhesion. In practical applications, this characteristic makes it difficult for contaminants to adhere to the membrane surface, and even if contaminants are deposited, they are easily carried away by the rolling water droplets, demonstrating excellent self-cleaning effect.

[0047] Furthermore, the preparation process of this invention has outstanding advantages such as mild conditions, controllable parameters, and wide applicability. The entire process is carried out under relatively mild conditions, with the highest processing temperature not exceeding 400°C, and avoids the investment in complex equipment. In addition, the selected raw materials are all commercially available, and the solvents are recyclable, showing good prospects for industrial application and economic benefits.

[0048] The present invention will now be described in more detail.

[0049] Example 1 This embodiment provides a method for modifying ceramic membranes to be superhydrophobic, as detailed below: First, a primary ceramic membrane is provided, wherein the primary ceramic membrane is in the form of a hollow single-channel membrane with a channel number of 1; the outer diameter of the ceramic membrane tube is 12 mm, the inner diameter is 8 mm, and the length is 100 mm; the main component of the ceramic membrane is aluminum oxide; the pore size of the ceramic membrane is approximately 100 nm.

[0050] Step A, Substrate Pretreatment: Alumina-based tubular ceramic membranes were selected and ultrasonically cleaned in deionized water, ethanol, and acetone for 20 minutes each, and then dried in an 80℃ drying oven for 6 hours for later use.

[0051] Step B, Vapor Phase SiO2 Layer Deposition: Weigh vapor phase SiO2 (particle size 12nm) and disperse it in anhydrous ethanol-methanol mixed solvent (volume ratio 9:1) at a mass ratio of 1:10. Add 0.5% ammonia water (concentration 28%) to adjust the pH to 8.5, and ultrasonically mix for 1 hour to form a uniform suspension slurry. Vertically immerse the pretreated ceramic membrane into the slurry and pull it out at a speed of 10mm / s. Let it stand at room temperature for 10 minutes, and then pre-bake it in an oven at 80℃ for 1.5 hours. Subsequently, place the sample in a muffle furnace, heat it to 400℃ at a rate of 5℃ / min, hold it at that temperature for 2 hours, and cool it with the furnace to form a stable SiO2 layer.

[0052] Step C, PDA adhesion layer preparation: Weigh 4.8456 g of tris(hydroxymethyl)aminomethane (Tris) and dissolve it in an appropriate amount of distilled water. Add 2 mL of citric acid (CA) solution and bring the volume to 1 L to obtain a Tris-CA buffer solution with pH=8.5. Take 500 mL of this buffer solution and add 2.5 g of dopamine hydrochloride to prepare a 5 mg / mL dopamine-Tris-citric acid buffer solution. Immerse the ceramic membrane obtained in step S2 into this solution and react with shaking at room temperature for 8 hours. After the reaction is complete, a PDA-modified ceramic membrane is obtained.

[0053] Step D, Preparation of the PDMS hydrophobic layer: Dow Corning Sylgard 184 elastomer substrate and curing agent were dissolved in n-hexane at a mass ratio of 10:1 to prepare a PDMS solution with a total mass concentration of 2%. The ceramic membrane obtained in step S3 was immersed in the PDMS solution for 4 hours, followed by pre-curing at 120°C for 2 hours to obtain a superhydrophobic ceramic membrane.

[0054] After sample preparation, a static contact angle test was performed using the bottom drop method. The static contact angle of the constructed superhydrophobic surface was found to be 153.3°. The resulting sample was then cut into small segments for acid stability, alkali stability, and thermal stability tests.

[0055] Example 2 The difference between Example 2 and Example 1 is that the concentration of polydopamine in the dopamine Tris-citric acid buffer solution is reduced, resulting in a more uniform loading of polydopamine. Specifically, Example 2 includes: Step A, Substrate Pretreatment: Alumina-based tubular ceramic membranes were selected and ultrasonically cleaned in deionized water, ethanol, and acetone for 20 minutes each, and then dried in an 80℃ drying oven for 6 hours for later use.

[0056] Step B, deposition of vapor-phase SiO2 layer: Fumed silica (12 nm particle size) was weighed and dispersed in anhydrous ethanol-methanol mixed solvent (9:1 volume ratio) at a mass ratio of 1:10. 0.5% ammonia (28% concentration) was added dropwise to adjust the pH to 8.5. The mixture was ultrasonically mixed for 1 hour to form a uniform suspension slurry. The pretreated ceramic membrane was vertically immersed in the slurry and pulled out at a speed of 10 mm / s. After standing at room temperature for 10 minutes, it was pre-dried in an oven at 80℃ for 1.5 hours. Subsequently, the sample was placed in a muffle furnace and heated to 400℃ at a rate of 5℃ / min, held at that temperature for 2 hours, and then cooled with the furnace to form a stable SiO2 layer.

[0057] Step C, PDA adhesion layer preparation: Weigh 4.8456 g of tris(hydroxymethyl)aminomethane (Tris) and dissolve it in an appropriate amount of distilled water. Add 2 mL of citric acid (CA) solution and bring the volume to 1 L to obtain a Tris-CA buffer solution with pH=8.5. Take 500 mL of this buffer solution and add 1 g of dopamine hydrochloride to prepare a 2 mg / mL dopamine-Tris-citric acid buffer solution. Immerse the ceramic membrane obtained in step S2 into this solution and react with shaking at room temperature for 8 hours. After the reaction is complete, rinse with deionized water and dry to obtain a PDA-modified ceramic membrane.

[0058] Step D, Preparation of PDMS hydrophobic layer: A PDMS solution with a total mass concentration of 2% was prepared by dissolving Dow Corning Sylgard 184 elastomer substrate and curing agent in n-hexane at a mass ratio of 10:1. The ceramic membrane obtained in step S3 was immersed in the PDMS solution for 4 hours, followed by pre-curing at 120°C for 2 hours to obtain a superhydrophobic ceramic membrane.

[0059] The static contact angle of the constructed superhydrophobic surface was tested using the bottom drop method, and the results are shown in the figure. It can be seen that the static contact angle is 160.0°. The obtained sample was then cut into small segments for acid stability, alkali stability, and thermal stability tests.

[0060] Example 3 The difference between Example 3 and Example 1 is that the concentration of the suspension slurry is increased, thereby increasing the silica loading. Specifically, Example 3 includes: Step A, Substrate Pretreatment: Select an alumina-based tubular ceramic membrane, and ultrasonically clean it in deionized water, ethanol, and acetone for 20 minutes each, then dry it in an 80℃ drying oven for 6 hours for later use.

[0061] Step B, Vapor Phase SiO2 Layer Deposition: Weigh fumed silica (12nm particle size) and disperse it in anhydrous ethanol-methanol mixed solvent (9:1 volume ratio) at a mass ratio of 1:7. Add 0.5% ammonia (28% concentration) dropwise to adjust the pH to 8.5, and ultrasonically mix for 1 hour to form a uniform suspension slurry. Vertically immerse the pretreated ceramic membrane into the slurry and pull it out at a speed of 10mm / s. Let it stand at room temperature for 10 minutes, and then pre-bake it in an 80℃ oven for 1.5 hours. Subsequently, place the sample in a muffle furnace, heat it to 400℃ at a rate of 5℃ / min, hold it at that temperature for 2 hours, and cool it with the furnace to form a stable SiO2 layer.

[0062] Step C, PDA adhesion layer preparation: Weigh 4.8456 g of tris(hydroxymethyl)aminomethane (Tris) and dissolve it in an appropriate amount of distilled water. Add 2 mL of citric acid (CA) solution and bring the volume to 1 L to obtain a Tris-CA buffer solution with pH=8.5. Take 500 mL of this buffer solution and add 2.5 g of dopamine hydrochloride to prepare a 5 mg / mL dopamine-Tris-citric acid buffer solution. Immerse the ceramic membrane obtained in step S2 into this solution and react with shaking at room temperature for 8 hours. After the reaction is complete, rinse with deionized water and dry to obtain the PDA-modified ceramic membrane.

[0063] Step D, Preparation of the PDMS hydrophobic layer: Dow Corning Sylgard 184 elastomer substrate and curing agent were dissolved in n-hexane at a mass ratio of 10:1 to prepare a PDMS solution with a total mass concentration of 2%. The ceramic membrane obtained in step S3 was immersed in the PDMS solution for 4 hours, followed by pre-curing at 120°C for 2 hours to obtain a superhydrophobic ceramic membrane.

[0064] The static contact angle of the constructed superhydrophobic surface was tested using the bottom drop method, and the results are shown in the figure. It can be seen that the static contact angle of the constructed superhydrophobic surface is 158.5°. The obtained sample was then cut into small segments for acid stability, alkali stability, and thermal stability tests.

[0065] A second aspect of the present invention also provides a hydrophobic modified membrane. In an exemplary embodiment of the present invention, the hydrophobic modified membrane comprises: a SiO2 roughening layer formed on a substrate surface; a polydopamine intermediate bridging layer formed on the surface of the SiO2 roughening layer; and a polydimethylsiloxane curing layer formed on the polydopamine intermediate bridging layer.

[0066] In this embodiment, the hydrophobic modified membrane is applied in a carbon dioxide capture membrane contactor. The substrate is a tubular ceramic membrane substrate. The surface static water contact angle of the hydrophobic modified membrane is ≥150° and the roll-off angle is ≤10°.

[0067] A third aspect of the present invention also provides a method. In an exemplary embodiment of the present invention, the tubular ceramic membrane comprises: Tubular ceramic membrane substrate; The hydrophobically modified membrane comprises: a SiO2 roughened layer formed on the surface of a tubular ceramic membrane substrate; a polydopamine intermediate bridging layer formed on the surface of the SiO2 roughened layer; and a polydimethylsiloxane hydrophobic layer formed on the polydopamine intermediate bridging layer.

[0068] This concludes the description of the various embodiments of the present invention. Based on the above description, those skilled in the art should have a clear understanding of the present invention.

[0069] It should be noted that for certain implementation methods, if they are not the key content of this invention and are well known to those skilled in the art, they are not described in detail in the accompanying drawings or text due to space limitations. In such cases, they can be understood by referring to the relevant prior art.

[0070] Unless explicitly stated otherwise, the numerical values ​​and ranges mentioned in this invention are approximate and can be changed according to the content of this invention. Specifically, all figures in the specification and claims indicating the content of composition, reaction conditions, etc., should be understood to be modified by the term "about" in all cases, meaning that they include variations of ±10% in certain embodiments.

[0071] Those skilled in the art will understand that in the claims and specification of this invention, the word "comprising" does not exclude the presence of elements (or steps) not listed in the claims. The word "a" or "an" preceding an element (or step) does not exclude the presence of a plurality of such elements (or steps).

[0072] Furthermore, the above embodiments are provided only to enable the invention to meet legal requirements, and the invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein.

[0073] Similarly, it should be understood that, for the sake of brevity, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of invention should not be construed as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, the various inventive aspects consist of fewer than all the features of the preceding single embodiment. Furthermore, embodiments may be used in combination with each other or with other embodiments based on design and reliability considerations; that is, technical features from different embodiments can be freely combined to form more embodiments. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0074] The above specific embodiments have provided a detailed description of the purpose, technical means, and beneficial effects of the present invention. It should be understood that the purpose of the detailed description is to enable those skilled in the art to better understand the present invention, and it is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for hydrophobic modification of the surface of a tubular ceramic membrane, characterized in that, include: Step B: A SiO2 roughening layer is formed on the surface of the tubular ceramic membrane substrate; Step C: A polydopamine intermediate bridging layer is formed on the surface of the SiO2 roughened layer; Step D: A polydimethylsiloxane hydrophobic layer is formed on the polydopamine intermediate bridging layer.

2. The method for hydrophobic modification of the surface of a tubular ceramic membrane according to claim 1, characterized in that, Step C includes: Sub-step C1: Prepare dopamine Tris-citric acid buffer solution; The concentration of the dopamine Tris-citric acid buffer solution is 1~10 mg / mL, and the pH of the solution is adjusted to 8~9; Sub-step C2 involves immersing the tubular ceramic membrane substrate treated in step B into a dopamine Tris-citric acid buffer solution and reacting it with ultrasonic vibration at room temperature for more than 6 hours. In sub-step C3, the tubular ceramic film substrate obtained in sub-step C2 is rinsed and dried to form a polydopamine intermediate bridging layer on the surface of the SiO2 roughened layer.

3. The method for hydrophobic modification of the surface of a tubular ceramic membrane according to claim 2, characterized in that, Sub-step C1 includes: Weigh 4.8456g of tris(hydroxymethyl)aminomethane and dissolve it in distilled water. Add 2mL of citric acid solution and bring the volume up to 1L to obtain a Tris-CA buffer solution with pH=8.

5. Take 500 mL of the Tris-CA buffer solution and add 2.5 g of dopamine hydrochloride to prepare a 5 mg / mL dopamine Tris-citric acid buffer solution; Sub-step C2 includes: immersing the tubular ceramic membrane substrate treated in sub-step C1 into the Tris-citric acid buffer solution and reacting it with ultrasonic vibration at room temperature for 8 hours. The sub-step C3 includes: rinsing and drying the tubular ceramic film substrate after sub-step C2 with deionized water, thereby forming a polydopamine intermediate bridging layer on the surface of the SiO2 roughened layer.

4. The method for hydrophobic modification of the surface of a tubular ceramic membrane according to claim 1, characterized in that, Step D includes: Sub-step D1: Prepare the PDMS solution; The PDMS solution is prepared by mixing Dow Corning Sylgard 184 elastic substrate, curing agent and n-hexane, with the mass ratio of elastic substrate to curing agent being 10:1, and the mass concentration of PDMS in the solution being 2-10%. Sub-step D2: Immerse the tubular ceramic membrane substrate treated in step C into PDMS solution and then remove it. The immersion time is 4-6 hours. Sub-step D3 involves heat-treating the tubular ceramic membrane substrate after sub-step D2, wherein the heat treatment temperature is 60~120℃ and the time is 2~4h.

5. The method for hydrophobic modification of the surface of a tubular ceramic membrane according to claim 1, characterized in that, Step B includes: Sub-step B1: Prepare the suspension slurry; The suspension slurry is formed by dispersing SiO2 nanoparticles in a mixed solvent of ethanol and methanol. The SiO2 nanoparticles are gaseous SiO2 particles with a particle size of 5-20 nm and a pH value between 8 and 9. Sub-step B2 involves depositing a SiO2 precursor on the surface of a tubular ceramic film substrate; The tubular ceramic membrane substrate is immersed and pulled in a suspension slurry to deposit SiO2 precursor on the surface of the tubular ceramic membrane substrate; Sub-step B3 involves sintering and solidification to form a SiO2 roughened layer. A tubular ceramic film substrate with a SiO2 precursor deposited on its surface is sintered to form a solidified SiO2 roughening layer on the surface of the tubular ceramic film.

6. The method for hydrophobic modification of the surface of a tubular ceramic membrane according to claim 5, characterized in that, Sub-step B1 includes: Silica particles are dispersed in a mixed solvent of anhydrous ethanol and methanol to form a mixed solution; wherein the volume ratio of anhydrous ethanol to methanol in the mixed solvent is 9:1; and the mass ratio of silica particles to the mixed solvent is 1:

10. Adjust the pH of the mixed solution to between 8 and 9 by adding ammonia dropwise. The pH-adjusted mixed solution was ultrasonically mixed for 1-2 hours using an ultrasonic power of 450-600W to obtain a suspension slurry. Sub-step B2 includes: repeating the immersion and lifting process several times. Each immersion and lifting process includes: vertically immersing the ceramic membrane into the slurry, lifting it at a speed of 5-10 mm / s after 20-30 seconds, and letting it stand at room temperature for 10-20 minutes. Sub-step B3 includes: first, pre-drying in an oven at 60~80℃ for 1~2 hours, then placing it in a muffle furnace and heating it to 400℃ at a rate of 3~6℃ / min, holding it at that temperature for 2~4 hours, and then cooling it to room temperature with the furnace to form a stable SiO2 layer.

7. The method for hydrophobic modification of the surface of a tubular ceramic membrane according to claim 1, characterized in that, Before step B, the method further includes step A, in which the tubular ceramic membrane substrate is ultrasonically cleaned in deionized water, ethanol, and acetone in sequence, and then dried for later use; wherein, in the ultrasonic cleaning, the ultrasonic power is 540~750W and the cleaning time is 20~30min; in the drying, the drying temperature is 60~80℃ and the drying time is 6~8h. The tubular ceramic membrane substrate is a single-channel tubular membrane tube with an outer diameter of 12-16 mm, an inner diameter of 8-12 mm, and a length of 100-600 mm. The main component of the membrane material is aluminum oxide, and the pore size is 0.03-1 μm. The tubular ceramic membrane substrate is composed of aluminum oxide; its pore size is between 10 and 1000 nm.

8. A hydrophobically modified membrane, characterized in that, include: A SiO2 roughening layer is formed on the substrate surface; A polydopamine intermediate bridging layer is formed on the surface of the SiO2 roughened layer; A polydimethylsiloxane hydrophobic layer is formed on the polydopamine intermediate bridging layer.

9. The hydrophobic modified membrane according to claim 8, characterized in that, The substrate is a tubular ceramic membrane substrate; The surface static water contact angle of the hydrophobic modified membrane is ≥150°, and the roll-off angle is ≤10°; The hydrophobic modified membrane is used in a carbon dioxide capture membrane contactor.

10. A tubular ceramic membrane, characterized in that, include: Tubular ceramic membrane substrate; Hydrophobic modified membranes, including: A SiO2 roughening layer is formed on the surface of the tubular ceramic membrane substrate; A polydopamine intermediate bridging layer is formed on the surface of the SiO2 roughened layer; A polydimethylsiloxane hydrophobic layer is formed on the polydopamine intermediate bridging layer.

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