Multi-effect membrane for membrane distillation technology and preparation method thereof

Abstract

The invention provides a multi-effect membrane for a membrane distillation technology and a preparation method of the multi-effect membrane. The preparation method comprises the following steps: taking castor oil as a core layer spinning solution; dissolving aluminum nitrate in absolute ethyl alcohol, uniformly stirring at room temperature to obtain an aluminum nitrate solution with the concentration of 50%, adding nano titanium dioxide particles and particles with core-shell structures, and uniformly stirring to obtain a shell spinning solution; carrying out electrostatic spinning by adopting a coaxial electrostatic spinning method to obtain an electrostatic spinning membrane; and calcining the electrostatic spinning membrane, and naturally cooling to room temperature to obtain the multi-effect membrane for the membrane distillation technology. Nanoparticles with different particle sizes are loaded on the hollow ceramic fiber membrane to form a multi-stage rough (micro-nano) structure, so that the hydrophobicity and oleophobicity are improved, the possibility of membrane wetting is reduced, the service life of the multi-effect membrane is prolonged, the stability of the multi-effect membrane is improved, meanwhile, the hollow ceramic fiber membrane is adopted, the heat preservation effect is very good, and the service life of the multi-effect membrane is prolonged. And heat loss can be effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a multi-effect membrane used in membrane distillation technology and a preparation method thereof. Background Art

[0002] Membrane distillation, as an emerging separation technology, has developed rapidly in recent years. It is favored by many scholars because of its advantages such as high retention rate, simple operation and low operating temperature. Membrane distillation has shown unique advantages in the deep treatment of high-salt organic wastewater. However, inorganic salts in wastewater are easy to scale on the membrane surface, and organic pollutants are easy to adhere to the membrane surface, which will lead to membrane pollution and membrane wetting. Therefore, improving the anti-pollution and anti-wetting properties of membrane materials is a way to achieve large-scale application of membrane distillation technology. Using traditional methods to improve the hydrophobicity of membrane materials cannot solve the problem of organic and oil substances such as surfactants polluting the membrane surface. At present, the method of constructing micro-nano structures on the membrane surface and supplementing fluorination to reduce the surface energy can achieve hydrophobic and oleophobic modification at the same time, but the fluorination agent is toxic, expensive and may affect the pore structure of the base membrane during the modification process, resulting in a decrease in membrane flux. At the same time, since the two cold and hot liquids are in direct contact on both sides of the membrane, if the thermal resistance of the membrane is not large enough, it will cause more heat loss, and it is easy to produce temperature polarization, affecting the performance of the membrane. Therefore, how to prepare a hydrophobic and oleophobic multi-effect membrane without using a fluorinating agent, which can reduce membrane pollution and heat loss while achieving high efficiency interception, is an urgent problem to be solved. Summary of the invention

[0003] Technical problem to be solved: In view of the above-mentioned technical problems, the purpose of the present invention is to provide a multi-effect membrane for membrane distillation technology and a preparation method thereof, wherein nanoparticles of different particle sizes are loaded on a hollow ceramic fiber membrane to form a multi-level rough (micro-nano) structure, thereby improving the hydrophobicity and oleophobicity, and reducing the possibility of membrane wetting, thereby improving the service life and stability of the multi-effect membrane. At the same time, a hollow ceramic fiber membrane is used, which has a very good thermal insulation effect and can effectively reduce heat loss, solving the technical problem that due to direct contact between cold and hot liquids on both sides of the membrane, more heat loss will be caused when the thermal resistance of the membrane is not large enough, and temperature polarization is easily generated, affecting the performance of the membrane.

[0004] Technical solution: A multi-effect membrane for membrane distillation technology, wherein the multi-effect membrane for membrane distillation technology is a hollow ceramic fiber membrane, and nanoparticles of different particle sizes are loaded on the membrane; The pore size of the hollow ceramic fiber membrane is 0.2-1.0 μm. Furthermore, the nanoparticles with different particle sizes are nano titanium dioxide particles with a particle size of 2-8 nm and particles with a core-shell structure with a particle size of 20-80 nm. Furthermore, the particles with a core-shell structure have nano zirconium dioxide as a core and silicon carbide as a shell, and the shell layer has nano channels. Furthermore, the preparation method of the particles having a core-shell structure is as follows: Step 1: Take 4-5 parts of polycarbosilane, dissolve it in 60 parts of n-hexane, add 15-20 parts of nano zirconium dioxide, place it on a magnetic stirrer and stir until it is uniform, and continue stirring until the n-hexane evaporates completely; Step 2: Drying in a drying oven to obtain polycarbosilane-coated nano zirconium dioxide; Step 3: placing in a low-temperature plasma treatment instrument for treatment to obtain polycarbosilane-coated nano zirconium dioxide with nanochannels on the surface; Step 4: Place in a tube furnace, under the protection of N2 atmosphere, heat to 300℃ at a heating rate of 10℃ / min and keep warm for 2h, continue to heat to 1400-1600℃ at a heating rate of 10℃ / min for pyrolysis, and obtain core-shell particles with nano zirconium dioxide as the core layer and silicon carbide layer with nanochannels on the surface as the shell layer. Furthermore, the processing conditions of the low-temperature plasma treatment instrument are: atmosphere is N2, vacuum degree is 60Pa, power is 44W, and time is 30s. The method for preparing the multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding nano titanium dioxide particles with a particle size of 2-8 nm and particles with a core-shell structure with a particle size of 20-80 nm, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and performing electrospinning by a coaxial electrospinning method to obtain an electrospinning membrane; (4) The electrospun membrane is calcined at 800-1000°C for 1-3h and naturally cooled to room temperature to obtain a multi-effect membrane for membrane distillation technology. Furthermore, the addition amount of the nano titanium dioxide particles with a particle size of 2-8 nm is 300-500 mg / L aluminum nitrate solution. Further, the addition amount of the core-shell structured particles with a particle size of 20-80 nm is 500-700 mg / L aluminum nitrate solution. Further, the coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.5-1.0 mL / h, the shell layer spinning solution spinning rate is 1.5-2.0 mL / h, the spinning voltage is 18-25 kV, the spinning temperature is 20-25 ° C, and the distance from the receiving plate is 20-25 cm. Beneficial effects: 1. The present invention uses nanoparticles of different particle sizes to load on the hollow ceramic fiber membrane to form a multi-level rough (micro-nano) structure, thereby improving the hydrophobicity and oleophobicity and reducing the possibility of membrane wetting, thereby improving the service life and stability of the multi-effect membrane. 2. The present invention adopts a hollow ceramic fiber membrane, which has a very good thermal insulation effect and can effectively reduce heat loss. It solves the technical problem that due to the direct contact between the hot and cold liquids on both sides of the membrane, more heat loss will be caused when the thermal resistance of the membrane is not large enough, and temperature polarization is easily generated, thus affecting the performance of the membrane. 3. The particles with a core-shell structure used in the present invention have nano zirconium dioxide as the core and silicon carbide as the shell (stable support), and the shell has nano channels. The design of the core-shell structure enables it to have low thermal conductivity, thereby reducing the loss of thermal energy and improving the energy utilization rate. The heat-driven process of membrane distillation ensures efficient water vapor separation; the nano channels on the shell help to increase the flux of the membrane and provide a larger mass transfer channel for the membrane, thereby improving the overall mass transfer efficiency. 4. The present invention also uses nano-titanium dioxide. On the one hand, nano-titanium dioxide can construct a micro-nano structure with particles having a core-shell structure, and on the other hand, it can also construct nano-scale micro-turbulence, significantly enhancing the turbulence of the membrane interface fluid, effectively shortening the local residence time of the interaction between salt ions and the membrane surface, reducing crystal deposition, thereby reducing membrane pollution and maintaining permeation flux. At the same time, nano-titanium dioxide itself also has photocatalytic properties, which can decompose pollutants and reduce membrane pollution. DETAILED DESCRIPTION The present invention proposes a multi-effect membrane for membrane distillation technology and a preparation method thereof. In order to make the purpose, technical scheme and effect of the present invention clearer and more specific, the present invention will be further described in detail with reference to the following examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Example 1 The preparation method of particles with core-shell structure is as follows: Step 1: Take 4 parts of polycarbosilane, dissolve it in 60 parts of n-hexane, add 18 parts of nano zirconium dioxide, place it on a magnetic stirrer and stir until it is uniform, and continue stirring until the n-hexane evaporates completely; Step 2: Drying in a drying oven to obtain polycarbosilane-coated nano zirconium dioxide; Step 3: placing in a low-temperature plasma treatment instrument for treatment, the treatment conditions of the low-temperature plasma treatment instrument are: atmosphere of N2, vacuum degree of 60Pa, power of 44W, time of 30s, to obtain polycarbosilane-coated nano zirconium dioxide with nanochannels on the surface; Step 4: Place in a tube furnace, under the protection of N2 atmosphere, heat to 300℃ at a heating rate of 10℃ / min and keep warm for 2h, continue to heat to 1500℃ at a heating rate of 10℃ / min for pyrolysis, and obtain core-shell particles with nano zirconium dioxide as the core layer and silicon carbide layer with nanochannels on the surface as the shell layer. Example 2 The preparation method of particles with core-shell structure is as follows: Step 1: Take 5 parts of polycarbosilane, dissolve it in 60 parts of n-hexane, add 18 parts of nano zirconium dioxide, place it on a magnetic stirrer and stir until it is uniform, and continue stirring until the n-hexane evaporates completely; Step 2: Drying in a drying oven to obtain polycarbosilane-coated nano zirconium dioxide; Step 3: placing in a low-temperature plasma treatment instrument for treatment, the treatment conditions of the low-temperature plasma treatment instrument are: atmosphere of N2, vacuum degree of 60Pa, power of 44W, time of 30s, to obtain polycarbosilane-coated nano zirconium dioxide with nanochannels on the surface; Step 4: Place in a tube furnace, under the protection of N2 atmosphere, heat to 300℃ at a heating rate of 10℃ / min and keep warm for 2h, continue to heat to 1500℃ at a heating rate of 10℃ / min for pyrolysis, and obtain core-shell particles with nano zirconium dioxide as the core layer and silicon carbide layer with nanochannels on the surface as the shell layer. Example 3 The preparation method of particles with core-shell structure is as follows: Step 1: Take 5 parts of polycarbosilane, dissolve it in 60 parts of n-hexane, add 15 parts of nano zirconium dioxide, place it on a magnetic stirrer and stir until it is uniform, and continue stirring until the n-hexane evaporates completely; Step 2: Drying in a drying oven to obtain polycarbosilane-coated nano zirconium dioxide; Step 3: placing in a low-temperature plasma treatment instrument for treatment, the treatment conditions of the low-temperature plasma treatment instrument are: atmosphere of N2, vacuum degree of 60Pa, power of 44W, time of 30s, to obtain polycarbosilane-coated nano zirconium dioxide with nanochannels on the surface; Step 4: Place in a tube furnace, under the protection of N2 atmosphere, heat to 300℃ at a heating rate of 10℃ / min and keep warm for 2h, continue to heat to 1500℃ at a heating rate of 10℃ / min for pyrolysis, and obtain core-shell particles with nano zirconium dioxide as the core layer and silicon carbide layer with nanochannels on the surface as the shell layer. Example 4 The preparation method of particles with core-shell structure is as follows: Step 1: Take 5 parts of polycarbosilane, dissolve it in 60 parts of n-hexane, add 18 parts of nano zirconium dioxide, place it on a magnetic stirrer and stir until it is uniform, and continue stirring until the n-hexane evaporates completely; Step 2: Drying in a drying oven to obtain polycarbosilane-coated nano zirconium dioxide; Step 3: placing in a low-temperature plasma treatment instrument for treatment, the treatment conditions of the low-temperature plasma treatment instrument are: atmosphere of N2, vacuum degree of 60Pa, power of 44W, time of 30s, to obtain polycarbosilane-coated nano zirconium dioxide with nanochannels on the surface; Step 4: Place in a tube furnace, under the protection of N2 atmosphere, heat to 300℃ at a heating rate of 10℃ / min and keep warm for 2h, and continue to heat to 1400℃ at a heating rate of 10℃ / min for pyrolysis to obtain core layer of nano zirconium dioxide, shell layer of silicon carbide layer with nanochannels on the surface of the core-shell structure particles. Example 5 The preparation method of particles with core-shell structure is as follows: Step 1: Take 5 parts of polycarbosilane, dissolve it in 60 parts of n-hexane, add 18 parts of nano zirconium dioxide, place it on a magnetic stirrer and stir until it is uniform, and continue stirring until the n-hexane evaporates completely; Step 2: Drying in a drying oven to obtain polycarbosilane-coated nano zirconium dioxide; Step 3: placing in a low-temperature plasma treatment instrument for treatment, the treatment conditions of the low-temperature plasma treatment instrument are: atmosphere of N2, vacuum degree of 60Pa, power of 44W, time of 30s, to obtain polycarbosilane-coated nano zirconium dioxide with nanochannels on the surface; Step 4: Place in a tube furnace, under the protection of N2 atmosphere, heat to 300℃ at a heating rate of 10℃ / min and keep warm for 2h, continue to heat to 1600℃ at a heating rate of 10℃ / min for pyrolysis, and obtain core-shell particles with nano-zirconium dioxide as the core layer and silicon carbide layer with nano-channels on the surface as the shell layer. Particle size (nm) <![CDATA[Specific surface area (m 2 / g)]]> Example 1 20-70 711.43 Example 2 20-80 715.69 Example 3 30-80 716.31 Example 4 20-80 698.48 Example 5 20-80 727.56 Example 3 and Example 5 were selected for subsequent experiments. Example 6 A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 300 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 600 mg / L of the aluminum nitrate solution of the particles with a core-shell structure prepared in Example 3, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.8 mL / h, the shell layer spinning solution spinning rate is 1.8 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospinning membrane; (4) The electrospun membrane was calcined at 900°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Example 7 A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 400 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 600 mg / L of the aluminum nitrate solution of the particles with a core-shell structure prepared in Example 3, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.8 mL / h, the shell layer spinning solution spinning rate is 1.8 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospinning membrane; (4) The electrospun membrane was calcined at 900°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Example 8 A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 500 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 600 mg / L of the aluminum nitrate solution of the particles with a core-shell structure prepared in Example 3, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.8 mL / h, the shell layer spinning solution spinning rate is 1.8 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospinning membrane; (4) The electrospun membrane was calcined at 900°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Example 9 A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 400 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 500 mg / L of the aluminum nitrate solution of the particles with a core-shell structure prepared in Example 3, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.8 mL / h, the shell layer spinning solution spinning rate is 1.8 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospinning membrane; (4) The electrospun membrane was calcined at 900°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Example 10 A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 400 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 700 mg / L of the aluminum nitrate solution of the particles with a core-shell structure prepared in Example 3, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.8 mL / h, the shell layer spinning solution spinning rate is 1.8 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospinning membrane; (4) The electrospun membrane was calcined at 900°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Embodiment 11 A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 400 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 600 mg / L of the aluminum nitrate solution of the particles with a core-shell structure prepared in Example 3, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.5 mL / h, the shell layer spinning solution spinning rate is 1.5 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospun membrane; (4) The electrospun membrane was calcined at 900°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Example 12 A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 400 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 600 mg / L of the aluminum nitrate solution of the particles with a core-shell structure prepared in Example 3, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 1.0 mL / h, the shell layer spinning solution spinning rate is 2.0 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospun membrane; (4) The electrospun membrane was calcined at 900°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Embodiment 13 A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 400 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 600 mg / L of the aluminum nitrate solution of the particles with a core-shell structure prepared in Example 3, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.8 mL / h, the shell layer spinning solution spinning rate is 1.8 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospinning membrane; (4) The electrospun membrane was calcined at 800°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Embodiment 14 A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 400 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 600 mg / L of the aluminum nitrate solution of the particles with a core-shell structure prepared in Example 3, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.8 mL / h, the shell layer spinning solution spinning rate is 1.8 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospinning membrane; (4) The electrospun membrane was calcined at 1000°C for 2 h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Embodiment 15 A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 400 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 600 mg / L of the aluminum nitrate solution of the particles with a core-shell structure prepared in Example 5, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.8 mL / h, the shell layer spinning solution spinning rate is 1.8 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospinning membrane; (4) The electrospun membrane was calcined at 900°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Comparative Example 1 The difference between this embodiment and embodiment 7 is that the particles with a core-shell structure prepared in embodiment 3 are not used. Specifically, a method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring evenly at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 1000 mg / L of the aluminum nitrate solution and nano-titanium dioxide particles with a particle size of 2-8 nm, stirring evenly, and obtaining a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.8 mL / h, the shell layer spinning solution spinning rate is 1.8 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospinning membrane; (4) The electrospun membrane was calcined at 900°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. Comparative Example 2 The difference between this embodiment and embodiment 7 is that the particles with core-shell structure used do not have nanochannels. The specific preparation method is as follows: A method for preparing a multi-effect membrane for membrane distillation technology comprises the following steps: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring evenly at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding 400 mg / L of the aluminum nitrate solution of nano-titanium dioxide particles with a particle size of 2-8 nm and 600 mg / L of the aluminum nitrate solution of particles with a core-shell structure, stirring evenly, and obtaining a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and using the coaxial electrospinning method to perform electrospinning. The coaxial electrospinning conditions are: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.8 mL / h, the shell layer spinning solution spinning rate is 1.8 mL / h, the spinning voltage is 20 kV, the spinning temperature is 25° C., and the distance between the core layer spinneret and the receiving plate is 23 cm to obtain an electrospinning membrane; (4) The electrospun membrane was calcined at 900°C for 2h and naturally cooled to room temperature to obtain a hollow ceramic fiber membrane with a pore size of 0.2-1.0 μm and loaded with nanoparticles of different particle sizes, that is, a multi-effect membrane for membrane distillation technology. The preparation method of particles with core-shell structure is as follows: Step 1: Take 5 parts of polycarbosilane, dissolve it in 60 parts of n-hexane, add 15 parts of nano zirconium dioxide, place it on a magnetic stirrer and stir until it is uniform, and continue stirring until the n-hexane evaporates completely; Step 2: Drying in a drying oven to obtain polycarbosilane-coated nano zirconium dioxide; Step 3: Place in a tube furnace, under the protection of N2 atmosphere, heat to 300℃ at a heating rate of 10℃ / min and keep warm for 2h, and continue to heat to 1500℃ at a heating rate of 10℃ / min for pyrolysis to obtain core-shell structure particles with nano zirconium dioxide as the core layer and silicon carbide as the shell layer. Determine the contact angles of the multi-effect membrane used in membrane distillation technology in each embodiment to water and ethylene glycol; The results are shown in Table 2 below: Table 2 It can be seen from Table 2 that the multi-effect membrane of the present invention has a super hydrophobic effect, and the contact angle to ethylene glycol reaches a maximum of 146.0°, which is close to super oleophobic (>150°). Determination of kerosene retention rate and salt rejection rate: 50 mg / L kerosene and 4.5 wt% NaCl were used as feed liquids, and a membrane distillation experiment was carried out for 8 hours; and the decrease rate of water flux before and after the membrane distillation experiment was measured (to prove the anti-pollution ability of the membrane). The results are shown in Table 3 below: Table 3

Claims

1. A multi-effect membrane for membrane distillation technology, characterized in that: The multi-effect membrane used in membrane distillation technology is a hollow ceramic fiber membrane, on which nanoparticles of different particle sizes are loaded; The pore size of the hollow ceramic fiber membrane is 0.2-1.0 μm.

2. A multi-effect membrane for membrane distillation technology according to claim 1, characterized in that: The nanoparticles with different particle sizes are nano titanium dioxide particles with a particle size of 2-8 nm and particles with a core-shell structure with a particle size of 20-80 nm.

3. A multi-effect membrane for membrane distillation technology according to claim 2, characterized in that: The particles with a core-shell structure have nano zirconium dioxide as a core and silicon carbide as a shell, and the shell layer has nano channels.

4. A multi-effect membrane for membrane distillation technology according to claim 2, characterized in that: The preparation method of the particles having a core-shell structure is as follows: Step 1: Take 4-5 parts of polycarbosilane, dissolve it in 60 parts of n-hexane, add 15-20 parts of nano zirconium dioxide, place it on a magnetic stirrer and stir until it is uniform, and continue stirring until the n-hexane evaporates completely; Step 2: Drying in a drying oven to obtain polycarbosilane-coated nano zirconium dioxide; Step 3: placing in a low-temperature plasma treatment instrument for treatment to obtain polycarbosilane-coated nano zirconium dioxide with nanochannels on the surface; Step 4: Place in a tube furnace, under the protection of N2 atmosphere, heat to 300℃ at a heating rate of 10℃ / min and keep warm for 2h, continue to heat to 1400-1600℃ at a heating rate of 10℃ / min for pyrolysis, and obtain core-shell particles with nano zirconium dioxide as the core layer and silicon carbide layer with nanochannels on the surface as the shell layer.

5. A multi-effect membrane for membrane distillation technology according to claim 4, characterized in that: The processing conditions of the low-temperature plasma treatment instrument are: atmosphere is N2, vacuum degree is 60Pa, power is 44W, and time is 30s.

6. A method for preparing a multi-effect membrane for membrane distillation technology according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Castor oil is used as the core spinning solution; (2) dissolving aluminum nitrate in anhydrous ethanol, stirring at room temperature to obtain an aluminum nitrate solution with a concentration of 50%, adding nano titanium dioxide particles with a particle size of 2-8 nm and particles with a core-shell structure with a particle size of 20-80 nm, stirring to obtain a shell spinning solution; (3) pouring the core layer spinning solution into the core layer micro pump, pouring the shell layer spinning solution into the shell layer micro pump, and performing electrospinning by a coaxial electrospinning method to obtain an electrospinning membrane; (4) The electrospun membrane is calcined at 800-1000°C for 1-3h and naturally cooled to room temperature to obtain a multi-effect membrane for membrane distillation technology.

7. The method for preparing a multi-effect membrane for membrane distillation technology according to claim 6, characterized in that: The addition amount of the nano titanium dioxide particles with a particle size of 2-8 nm is 300-500 mg / L of aluminum nitrate solution.

8. The method for preparing a multi-effect membrane for membrane distillation technology according to claim 6, characterized in that: The added amount of the core-shell structured particles with a particle size of 20-80 nm is 500-700 mg / L of aluminum nitrate solution.

9. The method for preparing a multi-effect membrane for membrane distillation technology according to claim 6, characterized in that: The coaxial electrospinning conditions are as follows: the core layer spinneret diameter is 0.5 mm, the shell layer spinneret diameter is 1.0 mm, the core layer spinning solution spinning rate is 0.5-1.0 mL / h, the shell layer spinning solution spinning rate is 1.5-2.0 mL / h, the spinning voltage is 18-25 kV, the spinning temperature is 20-25° C., and the distance from the receiving plate is 20-25 cm.

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