A method for preparing a single-atom-based catalytic ceramic membrane, its products and applications

Abstract

This invention discloses a method for preparing a single-atom-based catalytic ceramic membrane, its products, and applications. The ceramic membrane is immersed in a single-atom catalyst precursor solution until saturation. The single-atom precursor solution is then vacuum-dried under the confined space of the membrane pores, forming a metal-carbon-nitrogen precursor complex within the pores. The membrane is then subjected to high-temperature calcination under a protective atmosphere to obtain a catalytic ceramic membrane loaded with a single-atom metal. This invention prepares a single-atom-based catalytic ceramic membrane by loading a single-atom catalyst (Mn, Co, Cu, Fe, Ni, Ag, etc.) inside the pores of the ceramic membrane. This fully utilizes the excellent catalytic performance of the single-atom catalyst and the nanoscale space of the ceramic membrane pores. Through coupling / activation of the oxidant, high-efficiency removal of new pollutants is achieved under high permeation flux conditions through nanoscale confined catalysis.

Description

Technical Field

[0001] This invention relates to the field of membrane-based confined catalytic water treatment technology, and in particular to a method for preparing a single-atom-based catalytic ceramic membrane, its products, and applications. Background Technology

[0002] New pollutants present in various types of wastewater pose a serious threat to ecological environment security and human health. Catalytic ceramic membrane coupled with advanced oxidation processes is considered a feasible technology for removing new pollutants from wastewater due to its high redox potential, ability to generate highly oxidizing reactive oxygen species (ROS), nano-confined catalytic effect, and high pollutant removal efficiency. However, the traditional preparation of catalytic ceramic membranes involves loading transition metal nanoparticles into the pores of a ceramic membrane. For example, the prepared ceramic membrane is immersed in a mixed solution including a metal precursor salt and a structure-directing agent using an impregnation method, followed by drying and low-temperature plasma treatment. Because the transition metal nanoparticles have relatively large particle sizes, the specific surface area of ​​the catalytic ceramic membrane is relatively small, and the number of catalytic active sites is limited, resulting in limited reaction efficiency between ROS and new pollutant molecules, thus severely restricting the removal efficiency of new pollutants in wastewater.

[0003] Compared to traditional transition metal nanoparticle catalysts, single-atom catalysts possess tunable electronic structures, near-100% atomic utilization, and numerous atomically dispersed active sites, thus exhibiting superior catalytic performance in removing novel pollutants. However, the application of single-atom catalysts still faces challenges such as difficult catalyst recovery, limited mass transfer between ROS and pollutant molecules, and the inability to achieve continuous catalytic reactions. These issues lead to higher application costs, limiting their large-scale application in the removal of novel pollutants.

[0004] To address these bottlenecks, existing technologies have developed techniques that couple single-atom catalysts to ceramic membranes. For example, by loading single-atom catalysts onto a ceramic substrate to prepare catalytic membranes, the problem of single-atom catalyst recycling has been solved. However, due to the strong hydrophobicity of single-atom catalysts, they are difficult to penetrate into the membrane pores. This has led to the continued use of conventional dip-coating suspension methods for preparing existing single-atom-based catalytic ceramic membranes. This involves first preparing a single-atom catalyst, then forming a coating suspension, and finally preparing the catalytic ceramic membrane through a dip-coating process. This method ultimately results in a single-atom catalytic membrane layer on the ceramic substrate, leading to problems such as uneven pore size distribution, low membrane flux, and high membrane preparation costs. 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 single-atom-based catalytic ceramic membrane. This method involves loading a single-atom catalyst (Mn, Co, Cu, Fe, Ni, Ag, etc.) into the pores of the ceramic membrane to prepare the membrane. This fully utilizes the excellent catalytic performance of the single-atom catalyst and the nanoscale space of the ceramic membrane pores, achieving highly efficient removal of new pollutants under high permeation flux conditions through nano-confined catalysis. Another objective of this invention is to provide products prepared using the above-described method for preparing single-atom-based catalytic ceramic membranes and their applications.

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

[0007] The present invention provides a method for preparing a single-atom-based catalytic ceramic membrane, comprising the following steps:

[0008] (1) Preparation of precursor solution for single-atom-based metal catalyst

[0009] (1-1) Melamine is added to dimethyl sulfoxide (DMSO) in a mass-to-volume ratio of melamine: cyanuric acid: dimethyl sulfoxide = 1g: 1g: 20-40mL. The mixture is stirred and dissolved to obtain solution A. Cyanuric acid is added to dimethyl sulfoxide (DMSO) in a mass-to-volume ratio of 1g: 1g: 20-40mL to obtain solution B.

[0010] (1-2) Take a metal nitrate solution with a concentration of 10-20 g / L based on the mass of metal, and take two equal portions of the above solution A and solution B; according to the volume ratio of nitrate solution: solution A = 1:2-5, add the metal nitrate solution to solution A and stir evenly, then add solution B and stir evenly to obtain a single-atom-based metal catalyst precursor solution.

[0011] (2) Preparation of single-atom-based catalytic ceramic membranes

[0012] The ceramic membrane is placed in the precursor solution and vacuum-pressed to allow it to fully absorb the precursor solution until saturation. After being removed and vacuum-dried once, the excess single-atom metal catalyst particles on the surface of the ceramic membrane are washed away with dimethyl sulfoxide (DMSO) solution. Then, a second vacuum drying is performed to obtain a completely dry ceramic membrane loaded with single atoms. The membrane is then calcined at 400–600°C under a protective atmosphere for 3–6 hours to obtain a single-atom-based catalytic ceramic membrane.

[0013] Furthermore, the metal nitrate described in this invention is one of the following: iron nitrate (Fe(NO3)3·9H2O), cobalt nitrate (Co(NO3)2·6H2O), nickel nitrate (Ni(NO3)2), manganese nitrate (Mn(NO3)2·6H2O), silver nitrate (AgNO3), and copper nitrate (Cu(NO3)2).

[0014] Further, in step (2) of the present invention, the vacuum pressure is applied at a vacuum level of 0.5–1.0 MPa for 20–30 minutes. The first vacuum drying is performed at a vacuum level of 0.8 MPa and a temperature of 60–100°C for 2–4 hours; the second vacuum drying is performed at a vacuum level of 0.9 MPa and a temperature of 80–100°C for 3–5 hours.

[0015] In the above scheme, the average pore size of the ceramic membrane of the present invention is 50-500 nm.

[0016] Another objective of this invention is achieved through the following technical solution:

[0017] The product obtained using the above-described method for preparing single-atom-based catalytic ceramic membranes.

[0018] The application of the single-atom-based catalytic ceramic membrane product of this invention is as follows: Using the single-atom-based catalytic ceramic membrane product coupled with an activated oxidant in a continuous flow process to degrade new pollutants in ultrapure water, when the concentration of new pollutants is 1–10 mg / L, the molar ratio of oxidant to new pollutants is 1:0.02–0.10, and the membrane flux is 100–150 LMH, the degradation efficiency of new pollutants is 100% during a continuous catalytic reaction of 5–7 hours.

[0019] In the above scheme, the oxidant used in the application of this invention is persulfate, hydrogen peroxide, ozone, or peracetic acid. The new pollutants include bisphenol A, ibuprofen, sulfamethoxazole, acetaminophen, carbamazepine, and other pharmaceuticals, nursing products, and endocrine disruptors.

[0020] The present invention has the following beneficial effects:

[0021] (1) This invention loads a single-atom catalyst into the pores of a ceramic membrane, making full use of the excellent catalytic performance of the single-atom catalyst and the nanoscale space of the ceramic membrane pores. Since the single-atom catalyst is fixed inside the ceramic membrane pores, it will not flow with the water when it flows through, thus effectively solving the bottleneck problem of difficult recovery and practical utilization of single-atom catalyst powder. At the same time, the single-atom catalyst does not form a new separation layer, and the permeation resistance is small. The high specific surface area of ​​the ceramic membrane is effectively utilized, which greatly improves the reactive sites of the catalytic ceramic membrane and its utilization efficiency and ROS yield. It breaks through the trade-off between the permeation flux of the catalytic ceramic membrane and the catalytic removal efficiency of pollutants, and realizes the efficient removal of new pollutants under high permeation flux conditions.

[0022] (2) The present invention has low preparation cost and good universality. Different types of single-atom catalysts can be loaded into the pores of ceramic membranes. The preparation process is simple and conducive to promoting the large-scale application of single-atom catalysts and catalytic ceramic membranes.

[0023] (3) The single-atom-based catalytic ceramic membrane of this invention couples / activates oxidants such as persulfate, hydrogen peroxide, ozone, and peracetic acid, enabling efficient removal of new pollutants from wastewater. During the catalytic reaction, the ceramic membrane pores loaded with single-atom catalysts can provide nano-confined catalytic space, effectively improving the yield and utilization efficiency of ROS, effectively alleviating membrane fouling while increasing the contact probability between ROS and new pollutant molecules, thus achieving efficient removal of new pollutants from wastewater. Attached Figure Description

[0024] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0025] Figure 1 These are scanning electron microscope (SEM) images of the surface and cross-section of the single-atom manganese-based catalytic ceramic membrane prepared in Example 1 of this invention;

[0026] Figure 2 These are scanning electron microscope (SEM) images of the surface and cross-section of the single-atom iron-based catalytic ceramic membrane prepared in Example 2 of this invention. Detailed Implementation

[0027] Example 1:

[0028] This embodiment describes a method for preparing a single-atom-based catalytic ceramic membrane, the steps of which are as follows:

[0029] (1) Preparation of single-atom catalyst precursor solution

[0030] (1-1) Melamine was added to dimethyl sulfoxide (DMSO) and stirred (at a speed of 250 r / min for 20 min) to dissolve it according to the mass-to-volume ratio of melamine: cyanuric acid: dimethyl sulfoxide = 1 g: 1 g: 30 mL, to obtain solution A; cyanuric acid was added to dimethyl sulfoxide (DMSO) and stirred (at a speed of 250 r / min for 20 min) to dissolve it, to obtain solution B;

[0031] (1-2) Take a manganese nitrate solution with a concentration of 20 g / L based on the mass of metal, and take two equal portions of solution A and solution B; according to the volume ratio of manganese nitrate solution: solution A = 1:3, add manganese nitrate solution to solution A and stir evenly (250 r / min for 30 min), then continue to add solution B and stir to mix (250 r / min for 30 min) to obtain a single-atom manganese catalyst precursor solution;

[0032] (2) Preparation of single-atom-based catalytic ceramic membranes

[0033] A ceramic membrane with an average pore size of 200 nm was placed in the aforementioned precursor solution and vacuum-pressed at 0.6 MPa for 30 min to allow the ceramic membrane to fully absorb the precursor solution until saturation. It was then removed and placed in a vacuum drying oven (0.8 MPa, 70°C) for a first vacuum drying of 3 h. Excess catalyst particles on the ceramic membrane surface were washed away with dimethyl sulfoxide (DMSO) solution, and then placed in a vacuum drying oven (0.9 MPa, 90°C) for a second vacuum drying of 5 h to obtain a completely dried ceramic membrane loaded with single atoms. This membrane was then calcined in a tube furnace at 550°C under a N2 protective atmosphere for 4 h to obtain a single-atom manganese-based catalytic ceramic membrane (see...). Figure 1 ).

[0034] Example 2:

[0035] This embodiment describes a method for preparing a single-atom-based catalytic ceramic membrane, which differs from Embodiment 1 in that:

[0036] 1. In step (1), the mass-to-volume ratio of melamine: cyanuric acid: dimethyl sulfoxide is 1g: 1g: 25mL;

[0037] 2. In step (2), the metal nitrate is ferric nitrate, and the concentration of the ferric nitrate solution is 15 g / L based on the mass of the metal.

[0038] 3. In step (2), the average pore size of the ceramic membrane is 100 nm; the calcination temperature is 500℃, and the holding time is 3 h;

[0039] 4. The prepared material is a single-atom iron-based catalytic ceramic membrane (see...). Figure 2 ).

[0040] like Figure 1 and Figure 2 As shown, in the embodiments of the present invention, the single-atom-based catalytic ceramic membrane has a single-atom catalyst loaded on the surface and cross-section of the ceramic membrane without forming a separate separation membrane layer; and the single-atom catalyst is uniformly distributed inside the membrane pores without clogging the pores and without increasing the permeation resistance.

[0041] Example 3:

[0042] The application of the single-atom-based catalytic ceramic membrane in this embodiment is as follows: The single-atom manganese-based catalytic ceramic membrane prepared in Example 1 is used to activate the persulfate continuous flow process to degrade bisphenol A in ultrapure water. When the persulfate concentration is 1.0 mM, the bisphenol A concentration is 8 mg / L, and the membrane flux is 130 LMH, the degradation efficiency of bisphenol A in the continuous catalytic reaction for 5 hours is 100%.

[0043] Example 4:

[0044] The application of the single-atom-based catalytic ceramic membrane in this embodiment is as follows: The single-atom iron-based catalytic ceramic membrane prepared in Example 2 is used to activate the continuous flow hydrogen peroxide process to degrade carbamazepine in ultrapure water. When the hydrogen peroxide concentration is 0.6 mM, the carbamazepine concentration is 10 mg / L, and the membrane flux is 120 LMH, the degradation efficiency of carbamazepine is 100% during the continuous catalytic reaction for 6 hours.

Claims

1. A method for preparing a single-atom-based catalytic ceramic membrane, characterized in that... Includes the following steps: (1) Preparation of single-atom-based metal catalyst precursor solution (1-1) Melamine is added to dimethyl sulfoxide and stirred and dissolved according to the mass-volume ratio of melamine: cyanuric acid: dimethyl sulfoxide = 1g: 1g: 20-40mL to obtain solution A; cyanuric acid is added to dimethyl sulfoxide and stirred and dissolved to obtain solution B. (1-2) Take a metal nitrate solution with a concentration of 10-20 g / L based on the mass of the metal, and take two equal portions of the above solution A and solution B; according to the volume ratio of nitrate solution: solution A = 1:2-5, add the metal nitrate solution to solution A and stir evenly, then add solution B and stir evenly to obtain a single-atom-based metal catalyst precursor solution; wherein, the metal nitrate is one of iron nitrate, cobalt nitrate, nickel nitrate, manganese nitrate, silver nitrate, and copper nitrate; (2) Preparation of single-atom-based catalytic ceramic membranes The ceramic membrane is placed in the precursor solution and vacuum-pressed until it is saturated. After vacuum drying and washing away excess single-atom metal catalyst particles on the surface of the ceramic membrane with dimethyl sulfoxide solution, a second vacuum drying is performed to obtain a completely dry ceramic membrane loaded with single atoms. Then, it is calcined at 400-600°C under a protective atmosphere for 3-6 hours to obtain a single-atom-based catalytic ceramic membrane.

2. The method for preparing a single-atom-based catalytic ceramic membrane according to claim 1, characterized in that: In step (2), the vacuum pumping is performed at a vacuum level of 0.5 to 1.0 MPa for 20 to 30 minutes.

3. The method for preparing a single-atom-based catalytic ceramic membrane according to claim 1, characterized in that: In step (2), the first vacuum drying is performed at a vacuum of 0.8 MPa and a temperature of 60–100°C for 2–4 hours; the second vacuum drying is performed at a vacuum of 0.9 MPa and a temperature of 80–100°C for 3–5 hours.

4. The method for preparing a single-atom-based catalytic ceramic membrane according to claim 1, characterized in that: The ceramic membrane has an average pore size of 50–500 nm.

5. The product obtained by the method for preparing a single-atom-based catalytic ceramic membrane according to any one of claims 1-4.

6. The application of the product according to claim 5, characterized in that: The single-atom-based catalytic ceramic membrane product is used to couple / activate a continuous flow process for degrading new pollutants in ultrapure water. When the concentration of new pollutants is 1-10 mg / L, the molar ratio of oxidant to new pollutants is 1:0.02-0.10, and the membrane flux is 100-150 LMH, the degradation efficiency of new pollutants is 100% during a continuous catalytic reaction of 5-7 hours. The new pollutants are bisphenol A, ibuprofen, sulfamethoxazole, acetaminophen, or carbamazepine.

7. The application according to claim 6, characterized in that: The oxidant is persulfate, hydrogen peroxide, ozone, or peracetic acid.

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