Preparation method for ceramic membrane having high-efficiency separation and catalytic functions and product prepared therefrom, and use

Abstract

Disclosed in the present invention are a preparation method for a ceramic membrane having high-efficiency separation and catalytic functions and a product prepared therefrom, and a use. A ceramic membrane support is prepared using large-particle-size ceramic particles as raw materials. A transition layer is prepared by a slurry dipping method using transition metal oxide nanofibers as raw materials. A separation membrane layer is prepared by a dip-coating method using small-particle-size ceramic particles as raw materials. A ceramic membrane having a sandwich structure is formed by means of one-step co-firing. In the present invention, the transition layer having high porosity and a large specific surface area is prepared from the transition metal oxide nanofibers, which increases the number of catalytic active sites and enhances permeation flux. The separation membrane layer having uniform pore size distribution and a flat membrane surface is prepared from the small-particle-size ceramic particles, which improves the separation efficiency of particulate matter and organic matter in water and reduces the accumulation of the particulate matter and organic matter in water on the membrane surface, and also prevents the particulate matter and organic matter in water from covering active sites on a catalytic ceramic membrane, thereby simultaneously improving the separation efficiency and the catalytic degradation efficiency of the ceramic membrane.

Description

A method for preparing a ceramic membrane with both high-efficiency separation and catalytic functions, its products and applications

[0001] This invention relates to the field of membrane separation technology, and in particular to a method for preparing a ceramic membrane with both high-efficiency separation and catalytic functions, as well as its products and applications. Background Technology

[0002] New pollutants exist in various types of wastewater, seriously threatening ecological security and human health. Catalytic ceramic membrane coupled with advanced oxidation processes is considered a feasible technology for removing new pollutants from wastewater. However, traditional catalytic ceramic membrane preparation involves loading transition metal nanoparticles into the pores of the ceramic membrane, such as using a metal precursor impregnation method. Because the transition metal nanoparticles have relatively large particle sizes after calcination, the specific surface area and catalytic active sites of the catalytic ceramic membrane are relatively small, resulting in limited reaction efficiency between reactive oxygen species (ROS) and new pollutant molecules, leading to low removal efficiency of new pollutants.

[0003] To address this, existing technologies employ nanofiber catalysts and single-atom catalysts with high specific surface areas as membrane layers, thereby increasing the number of active sites and ROS generation efficiency of the catalytic ceramic membrane, and promoting the efficient removal of new pollutants. However, wastewater often contains various organic substances and small particulate matter, inevitably causing membrane fouling during membrane operation. This leads to the failure of catalytic active sites, reducing the contact efficiency between the catalytic active sites and the oxidant, and severely limiting the efficient removal of new pollutants from wastewater.

[0004] Especially when wastewater contains particulate matter, macromolecular organic matter, and new pollutants simultaneously, the new pollutants are mostly dissolved organic matter, while the particulate matter and macromolecular organic matter are insoluble. Thus, even catalytic ceramic membranes based on nanofiber catalysts and single-atom catalysts, which can efficiently remove new pollutants and alleviate membrane fouling, suffer from low separation efficiency and severe membrane fouling due to the non-planar surface and uneven pore size distribution of nanofiber catalytic ceramic membranes. They cannot simultaneously achieve both high-efficiency separation and catalytic degradation. While single-atom catalytic ceramic membranes have a smooth surface and high catalytic efficiency, enabling efficient removal of new pollutants and separation of particulate matter and macromolecular organic matter, they still cannot prevent the accumulation of particulate matter and macromolecular organic matter on the membrane surface. This accumulation covers some catalytic active sites, reducing their utilization efficiency and inhibiting ROS generation, creating a trade-off between separation efficiency and catalytic function in catalytic ceramic membranes. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a ceramic membrane with both high-efficiency separation and catalytic functions. A high-throughput ceramic membrane support is prepared using large-diameter ceramic particles as raw material. A transition layer is prepared using transition metal oxide nanofibers as raw material via a slurry impregnation method. Based on this, a separation membrane layer is prepared using small-diameter ceramic particles as raw material via a dip-coating method. The transition layer and the separation membrane layer are then co-fired in a one-step process to form a sandwich-structured ceramic membrane with both high-efficiency separation and catalytic functions. Another objective of this invention is to provide products and applications obtained using the above-described method for preparing a ceramic membrane with both high-efficiency separation and catalytic functions.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] The present invention provides a method for preparing a ceramic membrane with both high-efficiency separation and catalytic functions, comprising the following steps:

[0008] (1) Preparation of ceramic membrane support

[0009] Coarse ceramic particles with an average particle size of 5–80 μm were mixed with a pore-forming agent and a binder, and a ceramic membrane support was prepared by dry pressing. The mixture was then calcined at 1300–1650 °C for 2–4 h to obtain a ceramic membrane support with an average pore size of 1–6 μm. The amounts of the pore-forming agent and binder were 5–15 wt% and 0.5–1.2 wt% of the coarse ceramic particles, respectively.

[0010] (2) Preparation of transition layer by slurry impregnation method

[0011] (2-1) Transition metal oxide nanofibers with a diameter of 20–100 nm and an aspect ratio of 20–50 are added to water along with a dispersant and a stabilizer. After stirring, a transition layer slurry with a solid content of 10–20% is obtained. The amounts of the dispersant and stabilizer are 0.2–0.8 wt% and 1.2–2.5 wt% of the transition metal oxide nanofibers, respectively.

[0012] (2-2) The ceramic membrane support is immersed in the transition layer slurry for 10-30 seconds and 1-5 times. The membrane thickness is 60-150 μm. After drying, a ceramic membrane with a transition layer is obtained.

[0013] (3) Preparation of separation membrane layer by dip coating method

[0014] (3-1) Fine ceramic particles with an average particle size ≤500nm, along with a dispersant and a stabilizer, are added to water. After stirring and ultrasonic dispersion, a separation membrane slurry with a solid content of 15-25% is obtained. The amounts of the pore-forming agent and the stabilizer are 0.5-1.5wt% and 1.5-3.5wt% of the fine ceramic particles, respectively.

[0015] (3-2) Immerse the ceramic membrane with the transition layer in the separation membrane slurry, take it out and dry it to obtain a ceramic membrane with the transition layer and the separation membrane layer;

[0016] (4) Preparation of ceramic membranes

[0017] The ceramic membrane with the transition layer and the separation membrane layer is calcined at a temperature of 900-1300℃ for 1-2 hours to obtain a ceramic membrane with both high-efficiency separation and catalytic functions. The ceramic membrane has a porosity of >45% and a pore size of 10-200nm.

[0018] Furthermore, the ceramic particles of the present invention are one or a combination of alumina, zirconium oxide, silicon carbide, and cordierite. The transition metal oxide nanofibers are one or a combination of manganese oxide fibers, titanium dioxide fibers, and iron oxide fibers.

[0019] In the above scheme, the dispersant of the present invention is one or more of Dolapix series dispersants, sodium hexametaphosphate, and polyethyleneimine, wherein polyethyleneimine cannot be mixed with Dolapix series dispersants; the stabilizer is one or a combination of sodium carboxymethyl cellulose, methyl cellulose, and polyvinyl alcohol.

[0020] The product is prepared using the above-mentioned method for preparing ceramic membranes that combine efficient separation and catalysis functions.

[0021] The application of the product described in this invention is as follows: Using the ceramic membrane product coupled with an activated oxidant in a continuous flow process to degrade new pollutants in water, when the concentration of new pollutants is 1–20 mg / L, and the influent TOC is 5–25 mg / L and COD is [missing information]. Mn The concentration was 20–200 mg / L, the turbidity was 0.5–3.0 NTU, and the UV concentration was [missing information]. 254 The diameter is 0.1–1.8 cm. -1 When the molar ratio of oxidant to new pollutant is 1:0.03–0.1, and the membrane flux is 100–150 LMH, the degradation efficiency of the new pollutant is 100% during the continuous catalytic reaction process of 1–24 h, and the TOC of the effluent is 0–1.5 mg / L and COD is 0–1.5 mg / L. Mn The concentration is 0~20 mg / L, the turbidity is 0~1.0, and the UV concentration is... 254 / 0~0.8cm -1 .

[0022] In the above scheme, the oxidant used in this invention is persulfate, hydrogen peroxide, ozone, or peracetic acid; the new pollutants are bisphenol A, ibuprofen, sulfamethoxazole, tetracycline, amoxicillin, and other pharmaceuticals, nursing products, and endocrine disruptors.

[0023] The present invention has the following beneficial effects:

[0024] (1) This invention uses transition metal oxide nanofibers as a transition layer and small-diameter ceramic particles as a separation membrane layer. The transition membrane layer formed by the transition metal oxide nanofibers has high porosity and specific surface area, which increases the number of catalytic active sites, the generation rate of ROS, and the permeate flux. The separation membrane layer formed by the small-diameter ceramic particles has a uniform pore size distribution and a smooth membrane surface, which improves the separation efficiency of particulate matter and organic matter in water and reduces their accumulation on the membrane surface, thus alleviating membrane fouling. At the same time, it avoids the coverage of the active sites of the catalytic ceramic membrane by particulate matter and organic matter in water, thereby achieving a simultaneous improvement in the separation efficiency and catalytic degradation efficiency of the ceramic membrane.

[0025] (2) In this invention, transition metal oxide nanofibers are used as the raw material for the transition layer. They are randomly stacked to form a three-dimensional mesh structure, which effectively prevents the transition layer slurry from leaking into the support. By controlling the number of dip coatings, the thickness of the transition layer can be adjusted, and the preparation of the membrane can be controlled. At the same time, the transition metal oxide nanofibers form an entangled structure, which avoids the generation of membrane cracks and provides a guarantee for the preparation of high-performance separation membranes.

[0026] (3) The present invention uses the slurry impregnation method to prepare the transition layer and the separation membrane layer, and uses the co-firing process of the transition layer and the separation membrane layer to prepare the ceramic membrane, which simplifies the preparation process and reduces the preparation cost of the catalytic ceramic membrane. Attached Figure Description

[0027] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0028] Figure 1 is a scanning electron microscope image of the surface and cross-section of the ceramic membrane prepared in Example 1 of the present invention (a: surface; b: cross-section). Detailed Implementation

[0029] Example 1:

[0030] 1. This embodiment describes a method for preparing a ceramic membrane that combines efficient separation and catalysis functions, the steps of which are as follows:

[0031] (1) Preparation of ceramic membrane support

[0032] 100g of coarse alumina particles with an average particle size of 20μm were mixed with 10g of corn starch and 0.8g of sodium carboxymethyl cellulose. The mixture was then dry-pressed (at a pressure of 12MPa) to prepare a ceramic membrane support. After calcination at 1450℃ for 3h, a ceramic membrane support with an average pore size of 2.5μm was obtained.

[0033] (2) Preparation of transition layer by slurry impregnation method

[0034] (2-1) 10g of titanium dioxide nanofibers with a diameter of 30nm and a length of 800nm, 0.05g of sodium hexametaphosphate, and 0.13g of polyvinyl alcohol were added to 100g of pure water and magnetically stirred for 30min (300r / min) to obtain a transition layer slurry.

[0035] (2-2) The above ceramic membrane support is immersed in the transition layer slurry for 25 seconds and is immersed once. After being taken out and placed in a constant temperature and humidity drying oven (temperature 90℃, humidity 60%), a ceramic membrane with a transition layer is obtained.

[0036] (3) Preparation of separation membrane layer by dip coating method

[0037] (3-1) Add 15g of alumina fine particles with an average particle size of 100nm, 0.08g of polyethyleneimine, and 0.18g of polyvinyl alcohol to 100g of pure water, stir magnetically for 20min (350r / min), and ultrasonically disperse for 5min to obtain the separation membrane slurry.

[0038] (3-2) The ceramic membrane with the transition layer is immersed in the separation membrane slurry for 20 seconds and is immersed once. After being taken out and placed in a constant temperature and humidity drying oven (temperature 80℃, humidity 50%), a ceramic membrane with the transition layer and the separation membrane layer is obtained.

[0039] (4) Preparation of ceramic membranes

[0040] The ceramic membrane with the transition layer and separation membrane layer was calcined in an electric furnace at 1100℃ for 2 hours to obtain a ceramic membrane with both high-efficiency separation and catalytic functions (see Figure 1). The ceramic membrane had a porosity of 50% and an average pore size of 30 nm.

[0041] 2. In this embodiment, the ceramic membrane-activated persulfate continuous flow process degrades ibuprofen in ultrapure water, with an influent TOC of 5.5 mg / L and COD of [missing value]. Mn The concentration was 25.5 mg / L, the turbidity was 0.72 NTU, and the UV concentration was... 254 It is 0.21cm -1 When the persulfate concentration was 0.8 mM, the ibuprofen concentration was 10 mg / L, and the membrane flux was 100 LMH, the degradation efficiency of ibuprofen was 100% for 12 consecutive hours of catalytic reaction, and the TOC of the effluent was 0.5 mg / L and COD was [not specified]. Mn The concentration was 5.8 mg / L, the turbidity was 0.51 NTU, and the UV concentration was... 254 It is 0.13cm -1 .

[0042] Example 2:

[0043] This embodiment describes a method for preparing a ceramic membrane that combines efficient separation and catalysis functions, the steps of which are as follows:

[0044] (1) Preparation of ceramic membrane support

[0045] 100g of coarse alumina particles with an average particle size of 40μm were mixed with 10g of corn starch and 0.8g of sodium carboxymethyl cellulose. The mixture was then dry-pressed (at a pressure of 12MPa) to prepare a ceramic membrane support. After calcination at 1550℃ for 2h, a ceramic membrane support with an average pore size of 3.2μm was obtained.

[0046] (2) Preparation of transition layer by slurry impregnation method

[0047] (2-1) 10g of manganese oxide nanofibers with a diameter of 40nm and a length of 900nm, 0.05g of sodium hexametaphosphate, and 0.13g of polyvinyl alcohol were added to 100g of pure water and magnetically stirred for 30min (300r / min) to obtain a transition layer slurry.

[0048] (2-2) The above ceramic membrane support is immersed in the transition layer slurry for 25 seconds and is immersed once. After being taken out and placed in a constant temperature and humidity drying oven (temperature 90℃, humidity 60%), a ceramic membrane with a transition layer is obtained.

[0049] (3) Preparation of separation membrane layer by dip coating method

[0050] (3-1) Add 15g of alumina fine particles with an average particle size of 200nm, 0.08g of polyethyleneimine, and 0.18g of polyvinyl alcohol to 100g of pure water, stir magnetically for 20min (350r / min), and ultrasonically disperse for 5min to obtain the separation membrane slurry.

[0051] (3-2) The ceramic membrane with the transition layer is immersed in the separation membrane slurry for 20 seconds and is immersed once. After being taken out and placed in a constant temperature and humidity drying oven (temperature 80℃, humidity 50%), a ceramic membrane with the transition layer and the separation membrane layer is obtained.

[0052] (4) Preparation of ceramic membranes

[0053] The ceramic membrane with the transition layer and separation membrane layer was calcined in an electric furnace at 1200℃ for 2 hours to obtain a ceramic membrane with both high-efficiency separation and catalytic functions. The ceramic membrane has a porosity of 55% and an average pore size of 50 nm.

[0054] 2. The ceramic membrane activated persulfate continuous flow process prepared in this embodiment degrades bisphenol A in surface water, with an influent turbidity of 2.1 NTU, TOC of 15 mg / L, and COD of [missing information].Mn 120 mg / L, UV 254 It is 1.2cm -1 When the persulfate concentration was 1.0 mM, the ibuprofen concentration was 15 mg / L, and the membrane flux was 120 LMH, the degradation efficiency of bisphenol A was 100% during a continuous 12-hour catalytic reaction. The turbidity of the effluent was 0.5 NTU, the TOC was 1.5 mg / L, and the COD was [not specified]. Mn 25 mg / L, UV 254 It is 0.21cm -1 .

Claims

1. A method for preparing a ceramic membrane with high separation and catalytic functions, characterized in that Includes the following steps: (1) Preparation of ceramic membrane support Coarse ceramic particles with an average particle size of 5–80 μm were mixed with a pore-forming agent and a binder, and a ceramic membrane support was prepared by dry pressing. The mixture was then calcined at 1300–1650 °C for 2–4 h to obtain a ceramic membrane support with an average pore size of 1–6 μm. The amounts of the pore-forming agent and binder were 5–15 wt% and 0.5–1.2 wt% of the coarse ceramic particles, respectively. (2) Preparation of transition layer by slurry impregnation method (2-1) Transition metal oxide nanofibers with a diameter of 20–100 nm and an aspect ratio of 20–50 are added to water along with a dispersant and a stabilizer. After stirring, a transition layer slurry with a solid content of 10–20% is obtained. The amounts of the dispersant and stabilizer are 0.2–0.8 wt% and 1.2–2.5 wt% of the transition metal oxide nanofibers, respectively. (2-2) The ceramic membrane support is immersed in the transition layer slurry for 10-30 seconds and 1-5 times. The membrane thickness is 60-150 μm. After drying, a ceramic membrane with a transition layer is obtained. (3) Preparation of separation membrane layer by dip coating method (3-1) Fine ceramic particles with an average particle size ≤500nm, along with a dispersant and a stabilizer, are added to water. After stirring and ultrasonic dispersion, a separation membrane slurry with a solid content of 15-25% is obtained. The amounts of the pore-forming agent and the stabilizer are 0.5-1.5wt% and 1.5-3.5wt% of the fine ceramic particles, respectively. (3-2) Immerse the ceramic membrane with the transition layer in the separation membrane slurry, take it out and dry it to obtain a ceramic membrane with the transition layer and the separation membrane layer; (4) Preparation of ceramic membranes The ceramic membrane with the transition layer and the separation membrane layer is calcined at a temperature of 900-1300℃ for 1-2 hours to obtain a ceramic membrane with both high-efficiency separation and catalytic functions. The ceramic membrane has a porosity of >45% and a pore size of 10-200nm.

2. The method for preparing a ceramic membrane with high separation and catalytic functions according to claim 1, characterized in that: The ceramic particles are one or a combination of alumina, zirconium oxide, silicon carbide, and cordierite.

3. The method for preparing a ceramic membrane with high separation and catalytic functions according to claim 1, characterized in that: The transition metal oxide nanofibers are one or a combination of manganese oxide fibers, titanium dioxide fibers, and iron oxide fibers.

4. The method for preparing a ceramic membrane with both high-efficiency separation and catalytic functions according to claim 1, characterized in that: The dispersant is one or more of Dolapix series dispersants, sodium hexametaphosphate, and polyethyleneimine, wherein polyethyleneimine cannot be mixed with Dolapix series dispersants; the stabilizer is one or a combination of sodium carboxymethyl cellulose, methyl cellulose, and polyvinyl alcohol.

5. Products prepared using the method for preparing ceramic membranes with both high-efficiency separation and catalytic functions as described in any one of claims 1-4.

6. Use of a product according to claim 5, characterized in that: The ceramic membrane product is used in a continuous flow process coupled with an oxidant to degrade new pollutants in water. When the concentration of new pollutants is 1–20 mg / L, and the influent TOC is 5–25 mg / L, COD… Mn The concentration was 20–200 mg / L, the turbidity was 0.5–3.0 NTU, and the UV concentration was [missing information]. 254 The diameter is 0.1–1.8 cm. -1 When the molar ratio of oxidant to new pollutant is 1:0.03 to 0.1 and the membrane flux is 100 to 150 LMH, the degradation efficiency of new pollutants is 100% during the continuous catalytic reaction process of 1 to 24 hours, and the turbidity of the membrane effluent is less than 1 NTU.

7. Use according to claim 6, characterized in that: The oxidizing agents are persulfate, hydrogen peroxide, ozone, and peracetic acid; the new pollutants are bisphenol A, ibuprofen, sulfamethoxazole, tetracycline, amoxicillin, and other pharmaceuticals, nursing products, and endocrine disruptors.