A method for preparing a ceramic membrane with both efficient separation and catalytic functions, as well as its products and applications

Abstract

The present invention discloses a method for preparing a ceramic membrane with both efficient separation and catalytic functions, as well as the products and applications thereof. The ceramic membrane support is prepared using large-particle ceramic particles as raw materials, a transition layer is prepared using a slurry impregnation method using transition metal oxide nanofibers as raw materials, and a separation membrane layer is prepared using a dip-coating method using small-particle ceramic particles as raw materials. A ceramic membrane with a sandwich structure is formed through a one-step co-firing process. The present invention uses transition metal oxide nanofibers to form a transition layer with high porosity and specific surface area, thereby increasing the number of catalytic active sites and permeation flux. Small-particle ceramic particles are used to form a separation membrane layer with a uniform pore size distribution and a flat membrane surface, thereby improving the separation efficiency of particulate matter and organic matter in water and reducing their accumulation on the membrane surface. This also prevents the particulate matter and organic matter in water from covering the active sites of the catalytic ceramic membrane, thereby achieving simultaneous improvements in both the separation efficiency and catalytic degradation efficiency of the ceramic membrane.

Description

Technical Field

[0001] The present invention relates to the field of membrane separation technology, and in particular to a method for preparing a ceramic membrane with both efficient separation and catalytic functions, as well as a product and application thereof. Background Art

[0002] New pollutants exist in all kinds of sewage and wastewater, posing a serious threat to ecological and environmental safety and human health. Catalytic ceramic membranes coupled with advanced oxidation processes are considered to be a feasible technology for removing new pollutants from sewage and wastewater. However, the preparation of traditional catalytic ceramic membranes is to load transition metal nanopowders inside the membrane pores of the ceramic membrane. For example, the catalytic ceramic membrane is prepared by the metal precursor impregnation method. Since the particle size of the transition metal nanopowders after calcination is relatively large, the specific surface area and catalytic active sites of the catalytic ceramic membrane are relatively small, the reaction efficiency of reactive oxygen species (ROS) with new pollutant molecules is limited, and the efficiency of new pollutant removal is low.

[0003] To this end, existing technologies use nanofiber catalysts and single-atom catalysts with high specific surface areas as membrane layers, thereby increasing the number of active sites in the catalytic ceramic membrane and the efficiency of ROS generation, promoting the efficient removal of new pollutants. However, wastewater often contains various organic matter and small particulate matter, which inevitably causes membrane fouling during membrane operation, leading to the failure of catalytic active sites and reduced contact efficiency between catalytic active sites and oxidants, severely limiting the efficient removal of new pollutants in wastewater.

[0004] Especially when particulate matter, macromolecular organic matter and new pollutants coexist in sewage and wastewater, since new pollutants are mostly soluble organic matter, while particulate matter and macromolecular organic matter are insoluble. In this way, even if the catalytic ceramic membrane prepared based on nanofiber catalysts and single-atom catalysts can efficiently catalytically remove new pollutants in water and alleviate membrane pollution, the membrane surface of the nanofiber catalytic ceramic membrane is non-planar and the pore size distribution is uneven, resulting in low separation efficiency and serious membrane pollution, and it is unable to simultaneously have efficient separation and catalytic degradation functions. Although the single-atom catalytic ceramic membrane has a flat membrane surface and high catalytic efficiency, it can achieve efficient removal of new pollutants and efficient separation of particulate matter and macromolecular organic matter in water, but it still cannot avoid the accumulation of particulate matter and macromolecular organic matter in water on the membrane surface, which in turn covers part of the catalytic active sites, reduces the utilization efficiency of the catalytic active sites, and inhibits the generation efficiency of ROS, resulting in a trade-off between the separation efficiency and catalytic function of the catalytic ceramic membrane. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art by providing a method for preparing a ceramic membrane with both efficient separation and catalytic functions. The method comprises preparing a high-flux ceramic membrane support using large-particle ceramic particles as a raw material, preparing a transition layer using a slurry impregnation method using transition metal oxide nanofibers as a raw material, and then preparing a separation membrane layer using a dip coating method using small-particle ceramic particles as a raw material. The transition layer and separation membrane layer are then co-fired in a single step to form a sandwich-structured ceramic membrane with both efficient separation and catalytic functions. Another object of the present invention is to provide products and applications obtained using this method for preparing a ceramic membrane with both efficient separation and catalytic functions.

[0006] The purpose of the present invention is achieved through the following technical solutions:

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

[0008] (1) Preparation of ceramic membrane support

[0009] A ceramic membrane support is prepared by dry pressing after mixing coarse ceramic particles with an average particle size of 5 to 80 μm with a pore-forming agent and a binder. The ceramic membrane support is calcined at 1300 to 1650° C. for 2 to 4 hours to obtain a ceramic membrane support with an average pore size of 1 to 6 μm. The pore-forming agent and binder are used in amounts of 5 to 15 wt% and 0.5 to 1.2 wt% of the coarse ceramic particles, respectively.

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

[0011] (2-1) adding transition metal oxide nanofibers having a diameter of 20 to 100 nm and an aspect ratio of 20 to 50, a dispersant, and a stabilizer to water, and stirring to obtain a transition layer slurry having a solid content of 10 to 20%; the dispersant and stabilizer are used in amounts of 0.2 to 0.8 wt% and 1.2 to 2.5 wt% of the transition metal oxide nanofibers, respectively;

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

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

[0014] (3-1) adding fine ceramic particles having an average particle size of ≤500 nm, a dispersant, and a stabilizer to water, stirring and ultrasonically dispersing the particles to obtain a separation membrane slurry having a solid content of 15-25%; the pore-forming agent and stabilizer are used in amounts of 0.5-1.5 wt% and 1.5-3.5 wt% of the fine ceramic particles, respectively;

[0015] (3-2) immersing a ceramic membrane having a transition layer in a separation membrane layer slurry, taking it out and drying it, thereby obtaining a ceramic membrane having a transition layer and a separation membrane layer;

[0016] (4) Preparation of ceramic membrane

[0017] The ceramic membrane with the transition layer and the separation membrane layer is calcined at a temperature of 900-1300°C and a holding time of 1-2 hours to obtain a ceramic membrane with both efficient separation and catalytic functions, with a porosity of more than 45% and a pore size of 10-200 nm.

[0018] Furthermore, the ceramic particles of the present invention are one or a combination of aluminum oxide, 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 the Dolapix series dispersants, sodium hexametaphosphate, and polyethyleneimine, wherein polyethyleneimine is not compatible with the Dolapix series dispersants; the stabilizer is one or a combination of sodium carboxymethyl cellulose, methyl cellulose, and polyvinyl alcohol.

[0020] The product is made using the above-mentioned method for preparing a ceramic membrane with both high-efficiency separation and catalytic functions.

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

[0022] In the above scheme, the oxidants used in the present invention are persulfate, hydrogen peroxide, ozone, and peracetic acid; the new pollutants are bisphenol A, ibuprofen, sulfamethoxazole, tetracycline, amoxicillin and other medicines and care products, and endocrine disruptors.

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

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

[0025] (2) The transition metal oxide nanofibers of the present invention serve as the raw material for the transition layer. They are randomly stacked to form a three-dimensional grid structure, effectively preventing 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, enabling controllable membrane preparation. Furthermore, the transition metal oxide nanofibers form an entangled structure, preventing cracks in the membrane and providing a guarantee for the preparation of high-performance separation membranes.

[0026] (3) The present invention utilizes a slurry impregnation method to prepare the transition layer and the separation membrane layer, and adopts a co-firing process of the transition layer and the separation membrane layer to prepare the ceramic membrane, thereby simplifying the preparation process and reducing the preparation cost of the catalytic ceramic membrane. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 1 These are scanning electron microscope photos of the surface and cross-section of the ceramic membrane prepared in Example 1 of the present invention (a: surface; b: cross-section). DETAILED DESCRIPTION

[0029] Example 1:

[0030] 1. This embodiment provides a method for preparing a ceramic membrane with both efficient separation and catalytic functions, the steps of which are as follows:

[0031] (1) Preparation of ceramic membrane support

[0032] 100 g of alumina coarse particles with an average particle size of 20 μm were mixed with 10 g of corn starch and 0.8 g of sodium carboxymethyl cellulose. A ceramic membrane support was prepared by dry pressing (pressure of 12 MPa). The mixture was calcined at 1450°C for 3 h to obtain a ceramic membrane support with an average pore size of 2.5 μm.

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

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

[0035] (2-2) Immersing the ceramic membrane support in the transition layer slurry for 25 seconds and once, removing the support and drying it in a constant temperature and humidity drying oven (temperature 90°C, humidity 60%) to obtain a ceramic membrane with a transition layer;

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

[0037] (3-1) 15 g of alumina fine particles with an average particle size of 100 nm, 0.08 g of polyethyleneimine, and 0.18 g of polyvinyl alcohol were added to 100 g of pure water, magnetically stirred for 20 min (350 rpm), and ultrasonically dispersed for 5 min to obtain a separation membrane slurry;

[0038] (3-2) Immersing the ceramic membrane having the transition layer in the separation membrane layer slurry for 20 seconds and once, removing the membrane and drying it in a constant temperature and humidity drying oven (temperature 80°C, humidity 50%) to obtain a ceramic membrane having a transition layer and a separation membrane layer;

[0039] (4) Preparation of ceramic membrane

[0040] The ceramic membrane with the transition layer and the separation membrane layer was placed in an electric furnace for calcination at a temperature of 1100°C and a holding time of 2 hours to obtain a ceramic membrane with both high efficiency separation and catalytic functions (see Figure 1 The porosity of the ceramic membrane is 50% and the average pore size is 30 nm.

[0041] 2. The ceramic membrane activated persulfate continuous flow process prepared in this example degraded ibuprofen in ultrapure water, with the inlet TOC of 5.5 mg / L and COD Mn is 25.5mg / L, turbidity is 0.72NTU, UV 254 0.21cm -1 When the peroxymonosulfate 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% in the 12 h catalytic reaction, and the TOC of the membrane effluent was 0.5 mg / L and the COD Mn is 5.8mg / L, turbidity is 0.51NTU, UV 254 0.13cm -1 .

[0042] Example 2:

[0043] This embodiment provides a method for preparing a ceramic membrane with both efficient separation and catalytic functions, and the steps are as follows:

[0044] (1) Preparation of ceramic membrane support

[0045] 100 g of alumina coarse particles with an average particle size of 40 μm were mixed with 10 g of corn starch and 0.8 g of sodium carboxymethyl cellulose. A ceramic membrane support was prepared by dry pressing (pressure of 12 MPa). The mixture was calcined at 1550°C for 2 h to obtain a ceramic membrane support with an average pore size of 3.2 μm.

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

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

[0048] (2-2) Immersing the ceramic membrane support in the transition layer slurry for 25 seconds and once, removing the support and drying it in a constant temperature and humidity drying oven (temperature 90°C, humidity 60%) to obtain a ceramic membrane with a transition layer;

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

[0050] (3-1) 15 g of alumina fine particles with an average particle size of 200 nm, 0.08 g of polyethyleneimine, and 0.18 g of polyvinyl alcohol were added to 100 g of pure water, magnetically stirred for 20 min (350 rpm), and ultrasonically dispersed for 5 min to obtain a separation membrane slurry;

[0051] (3-2) Immersing the ceramic membrane having the transition layer in the separation membrane layer slurry for 20 seconds and once, removing the membrane and drying it in a constant temperature and humidity drying oven (temperature 80°C, humidity 50%) to obtain a ceramic membrane having a transition layer and a separation membrane layer;

[0052] (4) Preparation of ceramic membrane

[0053] The ceramic membrane with the transition layer and separation membrane layer was calcined in an electric furnace at 1200°C for 2 hours to produce a highly efficient separation and catalytic ceramic membrane. The membrane had 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 example degrades bisphenol A in surface water, with the inlet TOC of 15 mg / L and COD Mnis 120mg / L, turbidity is 2.1NTU, UV 254 1.2cm -1 When the peroxymonosulfate 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 in the catalytic reaction for 12 hours was 100%, and the TOC in the membrane effluent was 1.5 mg / L and the COD Mn is 20mg / L, turbidity is 0.5NTU, UV 254 0.21cm -1 .

Claims

1. A method for preparing a ceramic membrane with both separation and catalytic functions, characterized in that The following steps are involved: (1) Preparation of ceramic membrane support Coarse ceramic particles with an average particle size of 5 to 80 μm are mixed with a pore former and a binder, and a ceramic membrane support is prepared by dry pressing. The mixture is calcined at 1300 to 1650° C. for 2 to 4 hours to obtain a ceramic membrane support with an average pore size of 1 to 6 μm. The amounts of the pore former and the binder are 5 to 15 wt% and 0.5 to 1.2 wt% of the coarse ceramic particles, respectively. (2) Preparation of transition layer by slurry dipping method (2-1) adding transition metal oxide nanofibers having a diameter of 20 to 100 nm and an aspect ratio of 20 to 50, a dispersant, and a stabilizer to water, and stirring to obtain a transition layer slurry having a solid content of 10 to 20%; the amount of the dispersant and stabilizer used is 0.2 to 0.8 wt% and 1.2 to 2.5 wt% of the transition metal oxide nanofibers, respectively; (2-2) immersing the ceramic membrane support in a transition layer slurry for 10 to 30 seconds, 1 to 5 times, and with a membrane thickness of 60 to 150 μm. After removal and drying, a ceramic membrane with a transition layer is obtained; (3) Preparation of separation membrane layer by dip coating (3-1) adding fine ceramic particles having an average particle size of ≤500 nm, a dispersant, and a stabilizer to water, stirring and ultrasonically dispersing the particles to obtain a separation membrane slurry having a solid content of 15-25%; the pore-forming agent and stabilizer are used in amounts of 0.5-1.5 wt% and 1.5-3.5 wt% of the fine ceramic particles, respectively; (3-2) immersing a ceramic membrane having a transition layer in a separation membrane layer slurry, removing the membrane and drying the membrane to obtain a ceramic membrane having a transition layer and a separation membrane layer; (4) Preparation of ceramic membrane The ceramic membrane having the transition layer and the separation membrane layer is calcined at a temperature of 900 to 1300° C. and a holding time of 1 to 2 hours to obtain a ceramic membrane with both efficient separation and catalytic functions, a ceramic membrane porosity of >45%, and a membrane pore size of 10 to 200 nm.

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

3. The method for preparing a ceramic membrane having both separation and catalytic functions according to claim 1, characterized in that: The transition metal oxide nanofiber is one of manganese oxide fiber, titanium dioxide fiber, iron oxide fiber or a combination thereof.

4. The method for preparing a ceramic membrane having both 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 is not compatible with Dolapix series dispersants; the stabilizer is one or a combination of sodium carboxymethyl cellulose, methyl cellulose, and polyvinyl alcohol.

5. A product obtained by the method for preparing a ceramic membrane having both separation and catalytic functions according to any one of claims 1 to 4.

6. Use of the product according to claim 5, characterized in that: The ceramic membrane product is coupled with the activated oxidant continuous flow process to degrade new pollutants in water. When the concentration of new pollutants is 1-20 mg / L, the TOC of the influent is 5-25 mg / L, and the COD Mn 20~200 mg / L, turbidity 0.5~3.0NTU, UV 254 0.1~1.8cm -1 According to the molar ratio of oxidant: new pollutant = 1: 0.03-0.1, when the membrane flux is 100-150 LMH, the degradation efficiency of new pollutants in the catalytic reaction process of 1-24 hours is 100%, and the TOC of membrane effluent is 0-1.5 mg / L and COD Mn 0~20mg / L, turbidity 0~1.0, UV 254 0~0.8cm -1 .

7. The use according to claim 6, characterized in that: The oxidants are persulfate, hydrogen peroxide, ozone, and peracetic acid; the new pollutants are bisphenol A, ibuprofen, sulfamethoxazole, tetracycline, amoxicillin, and endocrine disruptors.

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