Single-atom cobalt-doped carbon material confined ceramic membrane, and construction method and application thereof

Abstract

The present application relates to a kind of single-atom cobalt doped carbon material confined ceramic membrane, including ceramic membrane substrate and surface load catalytic layer.Single-atom cobalt doped carbon material confined ceramic membrane and its construction method and application, introduce nano confinement effect into catalytic ozone system, in the process of ceramic membrane confined catalytic ozone water treatment, single-atom cobalt doped reduced graphene oxide catalytic layer, ceramic membrane pore can provide nano space, start the confined reaction of ozone (O3) decomposition, can effectively improve the yield of hydroxyl radical (·OH), overcome mass transfer limit, improve the utilization rate of ·OH, significantly strengthen the removal of new pollutants (ECs), high concentration ·OH generated on membrane surface and interface will also be quickly reacted with natural organic matter (NOM) in membrane pore, in situ reduce and control membrane pollution, single-atom cobalt doped carbon material confined ceramic membrane will provide technical support for the treatment of ECs in our country, promote the development of low-carbon, efficient, green water treatment technology.

Description

Technical Field

[0001] This invention relates to the field of confined ceramic films made of single-atom cobalt-doped carbon materials, specifically to a confined ceramic film made of single-atom cobalt-doped carbon materials, its construction method, and its application. Background Technology

[0002] Emerging pollutants (ECs) in the aquatic environment have attracted widespread attention from scientists worldwide due to their persistence, bioaccumulation, long-distance migration, and uncertainty of risk. In recent years, ECs have been frequently detected in surface water and groundwater, posing a potential threat to the ecological environment and human health. Therefore, it is urgent to develop advanced treatment technologies that can effectively remove ECs from water, continuously reduce environmental risks, and ensure water quality safety.

[0003] Catalytic ozone oxidation technology is considered a feasible method for removing ECs, and its application in drinking water in my country is increasing. In the traditional ozone oxidation process, adding catalysts such as metal oxides and activated carbon can enhance the decomposition of ozone (O3) to generate hydroxyl radicals (·OH) and superoxide radicals (O2). ·- ), singlet oxygen ( 1 Reactive oxygen species (ROS) such as O2 can significantly improve the removal rate of ozone-repellent pollutants. Among these ROS, O3 and O2 are the most abundant. ·- and 1 O2 exhibits selectivity, while O3 tends to attack pollutants with high electron cloud density (such as phenols, alkenes, deprotonated amines, and reduced sulfur groups). ·- It exhibits strong nucleophilicity and reacts rapidly with perfluorooctanoic acid and halogenated hydrocarbons. 1 O2 and O3 have similar selectivity, but O2's oxidizing power is significantly weaker than that of O3. In contrast, ·OH is a non-selective oxidant that can rapidly oxidize pollutants at a diffusion-controlled rate. Therefore, in catalytic ozone systems, ·OH oxidation is the main pathway for the removal of most ozone-repellent ECs, while other ROS contribute less.

[0004] However, the large-scale application of catalytic ozone oxidation technology to the removal of ECs in drinking water faces significant challenges: (1) It is generally believed that the catalyst plays a role only if it adsorbs O3, but due to the mass transfer of O3, the utilization rate of O3 is low, and the yield of ·OH (the number of moles of ·OH produced per mole of O3 decomposition) is usually less than 50%; (2) Since the short-lived ·OH is rapidly quenched by water molecules during the diffusion from the catalyst surface to the solution, the concentration of ·OH generated on the catalyst surface is much higher than the concentration of ·OH in the solution, but due to the mass transfer between ·OH and ECs, the high concentration of ·OH on the catalyst surface cannot be effectively utilized; (3) The catalyst has poor stability, poor reusability, and poor regeneration activity. As the number of times the catalyst is used increases, substances such as natural organic matter (NOM) and carbonates in the water may reduce the catalytic efficiency and change the reaction mechanism. It is difficult for the regenerated catalyst to achieve the treatment efficiency of the fresh catalyst. Therefore, how to efficiently and stably generate and utilize ·OH in actual water treatment is the key issue of catalytic ozone oxidation technology.

[0005] Introducing the nano-confinement effect into the catalytic ozone system is expected to overcome the technical bottleneck of catalytic ozone production, improve the yield and utilization of ·OH, and enhance the reusability of the catalyst and the stability of the system. This invention will develop a single-atom cobalt-doped reduced graphene oxide confined catalyst and load it onto a ceramic membrane as an active material to construct a nano-confined ceramic membrane. Mass transfer is enhanced through both catalyst confinement and membrane pore confinement. The nano-confined ceramic membrane, through the cobalt-doped nano-carbon material catalyst layer and the nanospace provided by the ceramic membrane pores, initiates the confined reaction of O3 decomposition, improving the ·OH yield. ·OH and ECs will undergo a nano-confined reaction during cross-flow filtration, effectively overcoming mass transfer limitations and improving the utilization of ·OH, thereby achieving efficient removal of ECs. In addition, O3 and ROS in the reaction system will react with dissolved organic matter on the membrane surface and in the membrane pores, achieving in-situ control of membrane fouling and increasing the stability of the catalyst layer. Summary of the Invention

[0006] To address the shortcomings of existing catalytic ozone oxidation technologies, this invention provides a single-atom cobalt-doped carbon material confined ceramic membrane, its construction method, and its application. This membrane has the advantage of efficiently and stably generating and utilizing ·OH, thus solving the bottleneck problem of mass transfer limitation in catalytic ozone systems.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a single-atom cobalt-doped carbon material confined ceramic film, comprising a ceramic film substrate and a catalyst layer.

[0008] Furthermore, the ceramic film substrate is composed of aluminum oxide, and the catalyst layer is single-atom cobalt-doped reduced graphene oxide.

[0009] Furthermore, the ceramic membrane substrate has an average pore size of 2-20 nanometers, and the confined space in the catalyst layer is 6-12 angstroms.

[0010] This application further proposes a method for constructing a single-atom cobalt-doped carbon material confined ceramic film, including the aforementioned single-atom cobalt-doped carbon material confined ceramic film, the steps of which are as follows:

[0011] 1) Weigh 2g of graphite and 1g of sodium nitrate, add 50mL of concentrated sulfuric acid, and stir in an ice-water bath;

[0012] 2) Slowly add 6g of potassium permanganate and stir in an ice-water bath;

[0013] 3) Transfer the solution obtained in step 2) to a 30°C water bath and continue stirring;

[0014] 4) Slowly add 100mL of ultrapure water and raise the water bath temperature to 98℃ to carry out the reaction;

[0015] 5) Add hydrogen peroxide solution to remove the remaining KMnO4 in the system until no oxygen is produced;

[0016] 6) Wash the above solids with ultrapure water and dilute hydrochloric acid respectively until the filtrate is neutral;

[0017] 7) The precipitate is dried to obtain graphene oxide powder;

[0018] 8) Weigh 0.1g of graphene oxide powder and 0.1g of melamine, and dissolve them in 48mL of ultrapure water;

[0019] 9) Add 2 mL of ammonia water;

[0020] 10) Transfer the above solution to a reaction vessel and react at 180°C for 10 hours;

[0021] 11) Filter and wash with ultrapure water to remove excess ammonia;

[0022] 12) Dry and filter the precipitate to obtain nitrogen-doped reduced graphene oxide powder;

[0023] 13) Weigh 0.5g of nitrogen-doped reduced graphene oxide powder and 0.015g of cobalt nitrate hexahydrate, and stir evenly for 1h;

[0024] 14) The above solution was sonicated in an ice-water bath for 1 hour, then quickly transferred to a freezer and frozen for 48 hours;

[0025] 15) Place the freeze-dried powder in a tube furnace and calcine it to obtain single-atom cobalt-doped reduced graphene oxide powder.

[0026] 16) Using ultrafiltration or nanofiltration ceramic membranes with pore sizes of 2nm, 5nm, 10nm and 20nm as substrates, single-atom cobalt-doped reduced graphene oxide powder catalysts were uniformly dispersed in ultrapure water, and the catalysts were loaded onto the ceramic membranes by ultrasonication.

[0027] 17) The ceramic membrane is sequentially dried, calcined, and washed with ultrapure water to obtain a ceramic membrane that has been loaded once.

[0028] 18) Repeat the above steps to prepare single-atom cobalt-doped carbon confined ceramic films with different catalyst layer thicknesses.

[0029] Furthermore, the stirring time in step 1) is 1 hour, the stirring time in step 2) is 0.5 hours, and the stirring time in step 3) is 0.5 hours.

[0030] Furthermore, the reaction time in step 4) is 15 minutes.

[0031] Furthermore, the volume fraction of the hydrogen peroxide solution in step 5) is 3%.

[0032] Furthermore, the washing method in step 6) is vacuum filtration.

[0033] Furthermore, the drying temperature in step 7) is 60°C, and the drying time in step 7) is 4 hours.

[0034] Furthermore, the number of water washes in step 11) is 3-5 times, the drying temperature in step 12) is 60℃, the drying time in step 12) is 4 hours, the freezing time in step 14) is 6 hours, the freezing temperature in step 14) is -80℃, the nitrogen protection required in step 15) is 300℃, and the burning time in step 15) is 1 hour.

[0035] Furthermore, the drying temperature in step 17) is 60℃, the drying time in step 17) is 4h, the calcination temperature in step 17) is 300℃, the calcination time in step 17) is 1h, and the number of water washings in step 17) is 3-5 times.

[0036] Furthermore, the application of the single-atom cobalt-doped carbon material confined ceramic membrane in the catalytic ozone degradation of ECs.

[0037] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0038] This single-atom cobalt-doped carbon material confined ceramic membrane, its construction method, and its application introduce the nano-confinement effect into the catalytic ozone system. In the ceramic membrane confined catalytic ozone water treatment process, both the single-atom cobalt-doped reduced graphene oxide catalyst layer and the ceramic membrane pores provide nanoscale spaces, initiating the confined reaction of O3 decomposition and effectively increasing the ·OH yield. Furthermore, ·OH and ECs undergo a nano-confinement reaction during cross-flow filtration, overcoming mass transfer limitations, improving ·OH utilization, and effectively enhancing EC removal. Simultaneously, the high concentration of ·OH generated on the membrane surface and interface reacts rapidly with NOM in the membrane pores, reducing and controlling membrane fouling in situ. This single-atom cobalt-doped carbon material confined ceramic membrane will provide technical support for EC treatment in my country, promoting the development of low-carbon, efficient, and green water treatment technologies. Attached Figure Description

[0039] Figure 1 A schematic diagram illustrating the construction method of confined ceramic films made of single-atom cobalt-doped carbon materials;

[0040] Figure 2 This is a flowchart of the construction method of the present invention;

[0041] Figure 3 The yield of ozone decomposition into hydroxyl radicals catalyzed by a confined ceramic membrane made of single-atom cobalt-doped carbon material is shown in the figure.

[0042] Figure 4 The efficiency of ozone oxidation for the removal of p-chlorobenzoic acid using a confined ceramic membrane made of single-atom cobalt-doped carbon material.

[0043] Figure 5 This is a schematic diagram illustrating the principle of ozone catalysis using a single-atom cobalt-doped carbon material confined ceramic membrane in this invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1:

[0046] Please see Figure 1-5 The single-atom cobalt-doped carbon material confined ceramic film in this embodiment includes a ceramic film substrate and a catalyst layer. The ceramic film substrate is composed of aluminum oxide, and the catalyst layer is single-atom cobalt-doped reduced graphene oxide.

[0047] The ceramic membrane substrate has an average pore size of 2-20 nanometers, and the confinement space in the catalyst layer is 6-12 angstroms.

[0048] This application proposes a method for constructing a confined ceramic film made of single-atom cobalt-doped carbon material, comprising the following steps:

[0049] 1) Weigh 2g of graphite and 1g of sodium nitrate, add 50mL of concentrated sulfuric acid, and stir in an ice-water bath;

[0050] 2) Slowly add 6g of potassium permanganate and stir in an ice-water bath;

[0051] 3) Transfer the solution obtained in step 2) to a 30°C water bath and continue stirring;

[0052] 4) Slowly add 100mL of ultrapure water and raise the water bath temperature to 98℃ to carry out the reaction;

[0053] 5) Add hydrogen peroxide solution to remove the remaining KMnO4 in the system until no oxygen is produced;

[0054] 6) Wash the above solids with ultrapure water and dilute hydrochloric acid respectively until the filtrate is neutral;

[0055] 7) The precipitate is dried to obtain graphene oxide powder;

[0056] 8) Weigh 0.1g of graphene oxide powder and 0.1g of melamine, and dissolve them in 48mL of ultrapure water;

[0057] 9) Add 2 mL of ammonia water;

[0058] 10) Transfer the above solution to a reaction vessel and react at 180°C for 10 hours;

[0059] 11) Filter and wash with ultrapure water to remove excess ammonia;

[0060] 12) Dry and filter the precipitate to obtain nitrogen-doped reduced graphene oxide powder;

[0061] 13) Weigh 0.5g of nitrogen-doped reduced graphene oxide powder and 0.015g of cobalt nitrate hexahydrate, and stir evenly for 1h;

[0062] 14) The above solution was sonicated in an ice-water bath for 1 hour, then quickly transferred to a freezer and frozen for 48 hours;

[0063] 15) Place the freeze-dried powder in a tube furnace and calcine it to obtain single-atom cobalt-doped reduced graphene oxide powder.

[0064] 16) Using ultrafiltration or nanofiltration ceramic membranes with pore sizes of 2nm, 5nm, 10nm and 20nm as substrates, single-atom cobalt-doped reduced graphene oxide powder catalysts were uniformly dispersed in ultrapure water, and the catalysts were loaded onto the ceramic membranes by ultrasonication.

[0065] 17) The ceramic membrane is sequentially dried, calcined, and washed with ultrapure water to obtain a ceramic membrane that has been loaded once.

[0066] 18) Repeat the above steps to prepare single-atom cobalt-doped carbon confined ceramic films with different catalyst layer thicknesses.

[0067] The stirring time in step 1) is 1 hour, the stirring time in step 2) is 0.5 hours, and the stirring time in step 3) is 0.5 hours.

[0068] The reaction time in step 4) is 15 minutes.

[0069] The volume fraction of the hydrogen peroxide solution in step 5) is 3%.

[0070] The washing method in step 6) is vacuum filtration.

[0071] The drying temperature in step 7) is 60℃, and the drying time in step 7) is 4h.

[0072] The number of water washes in step 11) is 3-5 times.

[0073] The drying temperature in step 12) is 60℃, and the drying time in step 12) is 4h.

[0074] The freezing time in step 14) is 6 hours, and the freezing temperature in step 14) is -80°C.

[0075] Step 15) requires nitrogen protection. The burning temperature in step 15) is 300℃ and the burning time in step 15) is 1 hour.

[0076] The drying temperature in step 17) is 60℃, the drying time in step 17) is 4h, the calcination temperature in step 17) is 300℃, the calcination time in step 17) is 1h, and the number of water washings in step 17) is 3-5 times.

[0077] Please see Figure 3-4 , Figure 3 In the figure, CM-0.1, CM-0.5, CM-1, and CM-3 represent the cobalt loading (%), respectively.

[0078] Figure 4 In the figure, CM-0.1, CM-0.5, CM-1, and CM-3 represent the cobalt loading (%).

[0079] The beneficial effects of the above embodiments are as follows:

[0080] The single-atom cobalt-doped carbon material confined ceramic membrane constructed in this embodiment, when applied to a catalytic ozone oxidation system, exhibits significantly better removal efficiency for ECs such as chlorobenzoic acid than conventional powdered heterogeneous catalysts. By introducing the nano-confinement effect into the catalytic ozone system, both the single-atom cobalt-doped reduced graphene oxide catalyst layer and the ceramic membrane pores provide nanoscale spaces during the ceramic membrane-confined catalytic ozone water treatment process. This initiates the confined reaction of O3 decomposition, effectively increasing the ·OH yield. Furthermore, ·OH and ECs undergo a nano-confined reaction during cross-flow filtration, overcoming mass transfer limitations and improving ·OH utilization, effectively enhancing the efficient removal of ECs. Simultaneously, the high concentration of ·OH generated on the membrane surface and interface reacts rapidly with NOM in the membrane pores, reducing and controlling membrane fouling in situ.

[0081] Example 2: Unlike Example 1, in step 8), 0.1g of melamine can be replaced with 0.1g of dicyandiamide. The other steps and parameters are the same as in Example 1.

[0082] Example 3: Unlike Example 1, the nitrogen protection condition in steps 15) and 17) is replaced with argon protection. The other steps and parameters are the same as in Example 1.

[0083] Example 4: Unlike Example 1, in step 16), ultrasound is replaced by vacuum filtration, while the other steps and parameters are the same as in Example 1.

[0084] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0085] This single-atom cobalt-doped carbon material confined ceramic membrane, its construction method, and its application introduce the nano-confinement effect into the catalytic ozone system. In the ceramic membrane confined catalytic ozone water treatment process, both the single-atom cobalt-doped reduced graphene oxide catalyst layer and the ceramic membrane pores provide nanoscale spaces, initiating the confined reaction of O3 decomposition and effectively increasing the ·OH yield. Furthermore, ·OH and ECs undergo a nano-confinement reaction during cross-flow filtration, overcoming mass transfer limitations, improving ·OH utilization, and effectively enhancing EC removal. Simultaneously, the high concentration of ·OH generated on the membrane surface and interface reacts rapidly with NOM in the membrane pores, reducing and controlling membrane fouling in situ. This single-atom cobalt-doped carbon material confined ceramic membrane will provide technical support for EC treatment in my country, promoting the development of low-carbon, efficient, and green water treatment technologies.

[0086] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0087] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for constructing a confined ceramic film made of single-atom cobalt-doped carbon material, characterized in that, A confined ceramic film made of single-atom cobalt-doped carbon material, comprising a ceramic film substrate and a catalyst layer; The ceramic film substrate is composed of aluminum oxide, and the catalyst layer is single-atom cobalt-doped reduced graphene oxide. The ceramic membrane substrate has an average pore size of 2-20 nanometers, and the confinement space in the catalyst layer is 6-12 angstroms. The method for constructing confined ceramic films made of single-atom cobalt-doped carbon materials comprises the following steps: 1) Weigh 2g of graphite and 1g of sodium nitrate, add 50mL of concentrated sulfuric acid, and stir in an ice-water bath; 2) Slowly add 6g of potassium permanganate and stir in an ice-water bath; 3) Transfer the solution obtained in step 2) to a 30°C water bath and continue stirring; 4) Slowly add 100mL of ultrapure water and raise the water bath temperature to 98℃ to carry out the reaction; 5) Add hydrogen peroxide solution to remove the remaining KMnO4 in the system until no oxygen is produced; 6) Wash the above solids with ultrapure water and dilute hydrochloric acid respectively until the filtrate is neutral; 7) The precipitate is dried to obtain graphene oxide powder; 8) Weigh 0.1g of graphene oxide powder and 0.1g of melamine, and dissolve them in 48mL of ultrapure water; 9) Add 2 mL of ammonia water; 10) Transfer the above solution to a reaction vessel and react at 180°C for 10 hours; 11) Filter and wash with ultrapure water to remove excess ammonia; 12) Dry and filter the precipitate to obtain nitrogen-doped reduced graphene oxide powder; 13) Weigh 0.5g of nitrogen-doped reduced graphene oxide powder and 0.015g of cobalt nitrate hexahydrate, and stir evenly for 1h; 14) The above solution was sonicated in an ice-water bath for 1 hour, then quickly transferred to a freezer and frozen for 48 hours; 15) Place the freeze-dried powder in a tube furnace and calcine it to obtain single-atom cobalt-doped reduced graphene oxide powder. 16) Using ultrafiltration or nanofiltration ceramic membranes with pore sizes of 2nm, 5nm, 10nm and 20nm as substrates, single-atom cobalt-doped reduced graphene oxide powder catalysts were uniformly dispersed in ultrapure water, and the catalysts were loaded onto the ceramic membranes by ultrasonication. 17) The ceramic membrane is sequentially dried, calcined, and washed with ultrapure water to obtain a ceramic membrane that has been loaded once. 18) Repeat the above steps to prepare single-atom cobalt-doped carbon confined ceramic films with different catalyst layer thicknesses; The stirring time in step 1) is 1 hour, the stirring time in step 2) is 0.5 hours, the stirring time in step 3) is 0.5 hours, the reaction time in step 4) is 15 minutes, the volume fraction of the hydrogen peroxide solution in step 5) is 3%, the washing method in step 6) is vacuum filtration, the drying temperature in step 7) is 60°C, the drying time in step 7) is 4 hours, and the number of water washes in step 11) is 3-5 times. The drying temperature in step 12) is 60°C, and the drying time in step 12) is 4 hours. The freezing time in step 14) is 6 hours, and the freezing temperature in step 14) is -80°C. Step 15) requires nitrogen protection, the burning temperature in step 15) is 300℃, and the burning time in step 15) is 1 hour. The drying temperature in step 17) is 60℃, the drying time in step 17) is 4h, the calcination temperature in step 17) is 300℃, the calcination time in step 17) is 1h, and the number of water washings in step 17) is 3-5 times.

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