Method and device for treating formaldehyde wastewater by wet catalytic oxidation with supported carbon-based microporous graphite catalytic membrane

Abstract

The present application belongs to the technical field of industrial wastewater treatment, and particularly relates to a method and device for treating formaldehyde wastewater by using a supported carbon-based microporous graphite catalytic membrane wet catalytic oxidation process. The method for treating formaldehyde wastewater by using a supported carbon-based microporous graphite catalytic membrane wet catalytic oxidation process comprises a ceramic membrane filtration process and a wet catalytic oxidation reaction process. The catalyst used in the wet catalytic oxidation reaction process is a supported carbon-based microporous graphite catalytic membrane. The catalytic membrane comprises a carbon-based microporous graphite membrane substrate and active components, i.e., noble metals platinum and palladium, supported on the substrate. The method for treating formaldehyde wastewater by using a supported carbon-based microporous graphite catalytic membrane wet catalytic oxidation process can achieve excellent formaldehyde removal effect by preparing a Pt / Pd supported carbon-based microporous graphite catalytic membrane and utilizing the developed pores and high specific surface area of the membrane. In addition, the reaction conditions are mild. The present application also provides a device for treating formaldehyde wastewater.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, specifically relating to a method and apparatus for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane. Background Technology

[0002] Formaldehyde wastewater is widely generated in industries such as resin synthesis, board processing, coatings, textiles, fine chemicals, and pharmaceuticals. It often contains biotoxic substances such as phenols, amino compounds, and resin oligomers, and is characterized by large concentration fluctuations, poor biodegradability, high toxicity, and high treatment difficulty. Direct discharge will severely damage the aquatic environment and endanger human health. These pollutants often coexist in wastewater, increasing the complexity of the treatment process and the difficulty of subsequent biological treatment systems.

[0003] Current mainstream technologies for formaldehyde wastewater treatment include physical adsorption, biochemical methods, chemical oxidation, and membrane separation, but all have significant limitations: adsorption methods have limited capacity, are difficult to regenerate, and have poor selectivity for complex organic pollutants; biochemical methods are easily inhibited by high concentrations of formaldehyde, and salt and toxic intermediates can easily lead to system collapse, resulting in unstable treatment efficiency; traditional chemical oxidation methods consume large amounts of reagents, have high operating costs, and are prone to generating byproducts and secondary pollution.

[0004] Membrane technology has been widely used in industrial wastewater treatment in recent years due to its advantages such as high separation efficiency, compact equipment, ease of continuous operation, and easy coupling with other processes. In particular, membrane technology can easily separate and remove organic pollutants in wastewater, thereby reducing the load on subsequent treatments and improving the operating conditions of the system. However, single membrane separation technology can only achieve pollutant retention and cannot degrade them in situ, and membrane fouling and concentrate treatment problems are prominent.

[0005] Low-temperature wet catalytic oxidation technology is a wastewater treatment technology that lies between ambient temperature wet oxidation technology and medium- and high-pressure wet air oxidation technology. It has advantages such as high degradation efficiency, wide applicability, and mild conditions, and is gradually becoming an important direction for treating recalcitrant organic wastewater.

[0006] CN113000052A discloses a wet oxidation catalyst, its preparation method, and its application, which can efficiently oxidize formaldehyde at room temperature. However, this catalyst uses nickel-iron hydrotalcite as a support and prepares low-load electron-rich Pt wet oxidation catalyst powder through hydrothermal synthesis, liquid-phase reduction, and hydrogen calcination. Pt can promote the oxidation of formaldehyde even with low dosage, thereby improving the catalytic activity of the catalyst and reducing the operating temperature of the catalyst. This not only reduces the production cost of the catalyst but also reduces the cost of formaldehyde removal due to the low operating temperature. This patent uses powder as a catalyst, which is particularly prone to causing the catalyst powder to be lost with the wastewater, resulting in loss and a decrease in catalytic activity, especially in wastewater treatment.

[0007] CN1524613A discloses a highly active wet oxidation catalyst with carbon material as a support and its preparation method. The carbon support is prepared by activation and three-stage roasting of bamboo, coconut shell and coal as raw materials. The catalyst is prepared by spraying and impregnating loaded precious metals such as Pt, Pd and Ru and reducing with hydrogen. It is used for the treatment of high-concentration and recalcitrant organic wastewater. It utilizes the high specific surface area of ​​carbon material to improve the dispersibility of active sites and significantly reduce the amount of precious metals used. However, the catalyst precursor impregnation concentration is high in this method, resulting in high catalyst cost. Moreover, the prepared catalyst is mainly used in medium and high temperature wet oxidation processes at ≥200℃.

[0008] In recent years, catalytic membranes have gradually become a research hotspot, as they can simultaneously achieve separation and degradation in wastewater treatment. CN121422762A discloses a method for preparing a catalytic membrane for organic wastewater treatment. A casting solution is obtained using polyvinylidene fluoride (PVDF), a pore-forming agent, and plant polyphenols as raw materials. Subsequently, a PVDF membrane is obtained through a coating process and a water bath phase inversion. The active components are then loaded using an impregnation method, forming a metallic coating on the membrane surface and the inner walls of the pores. A polyphenol network layer is used to obtain a catalytic membrane. This membrane can achieve coupled filtration and catalytic degradation. The active sites are distributed on the surface and the inner wall of the pores, resulting in high pollutant removal rate, stable circulation, and extremely low metal precipitation. This method uses a casting solution to prepare a PVDF membrane. Although it has the function of retention-catalysis synergy, the PVDF membrane has defects such as narrow pore distribution range, small specific surface area, and poor adsorption performance. In addition, the PVDF membrane has poor regeneration performance.

[0009] In summary, although existing technologies have been extensively studied in areas such as catalytic membranes and wet catalytic oxidation, significant shortcomings remain for formaldehyde wastewater treatment: traditional catalysts are in powder form, making separation and continuous production difficult, and typically require high temperatures and pressures, resulting in high energy consumption; catalytic membranes rely on external oxidants, exhibit poor organic membrane stability, and are not adapted to formaldehyde degradation, making it difficult to balance efficiency and flux. Therefore, developing a deep coupling method of low-temperature wet catalytic oxidation with catalytic membranes for wastewater treatment to improve formaldehyde wastewater treatment efficiency and biodegradability is of significant practical importance. Summary of the Invention

[0010] The purpose of this invention is to overcome the aforementioned defects in the prior art and provide a method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane. This method involves preparing a Pt / Pd supported carbon-based microporous graphite catalytic membrane and applying it to wet catalytic oxidation. Combined with a layered, ordered stacking method, the well-developed pore structure and high specific surface area within the microporous graphite membrane effectively adsorb, retain, and catalytically oxidize organic pollutants in formaldehyde wastewater. The reaction conditions are mild, and the formaldehyde removal effect is excellent. This invention also provides the apparatus used in the method for treating formaldehyde wastewater.

[0011] The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane of the present invention includes the following steps: (1) The pH of formaldehyde wastewater is adjusted to 3-5 using dilute hydrochloric acid with a concentration of 10-17wt.%. Then, the wastewater temperature is controlled at 15-40℃ and filtered through a ceramic membrane to remove suspended solids, colloidal impurities and macromolecular substances to obtain filtrate. (2) Add oxidant to the filtrate, and after preheating by the main heat exchanger, it enters the wet catalytic oxidation reactor. Catalytic degradation is carried out under the action of sheet-supported carbon-based microporous graphite catalytic membrane. The temperature is controlled at 140-180℃ and the pressure is 0.3-1.0MPa to obtain the treated liquid. After cooling by the main heat exchanger and cooler, it is discharged into the subsequent biochemical system after pH adjustment. The pH should be adjusted to neutral before entering the biochemical system.

[0012] In step (1), the formaldehyde wastewater index before dilute hydrochloric acid treatment is: COD: 8000-15000 mg / L, formaldehyde: 5000-10000 mg / L.

[0013] The supported carbon-based microporous graphite catalytic membrane comprises a carbon-based microporous graphite membrane substrate and active components, the noble metals platinum and palladium, supported on the substrate. Based on 100% mass of the carbon-based microporous graphite membrane substrate before calcination, the carbon-based microporous graphite membrane substrate comprises the following raw materials by mass percentage: phenolic resin: 5-10%, polymethyl methacrylate: 10-17%, coal tar pitch: 30-35%, activated carbon: 40-45%, nano-silicon carbide: 1-2%, boric acid: 1-2%, and hydroxymethyl cellulose: 1-2%. Its preparation method includes the following steps: S1. Phenolic resin, polymethyl methacrylate, coal tar pitch and ethanol are mixed and added to an alumina ball mill jar for mechanical ball milling for 12-36 hours. Then activated carbon is added and ball milling continues for 2-4 hours. After washing with water, filtration and drying are performed to obtain matrix powder material. The amount of ethanol used is twice the mass of the raw materials in S1. S2. The matrix powder material obtained in step S1 is mixed with nano-silicon carbide, boric acid and hydroxymethyl cellulose for 4-8 hours to obtain the mixed powder material. S3. The mixed powder material is mechanically dry-pressed and then sintered in an inert gas atmosphere. After sintering, it is cooled to room temperature to obtain a carbon-based microporous graphite film. S4. Dissolve H2PtCl6 and PdCl2 in a dilute hydrochloric acid / nitric acid mixed acid solution and stir for 8-12 hours to prepare a precursor solution; S5. Immerse the carbon-based microporous graphite membrane obtained in step S3 in the precursor solution of step S4 for 12-24 hours. After immersion, drain the membrane and dry it at 80-120℃. Then, sinter it in an inert gas atmosphere and cool it to room temperature to obtain a supported carbon-based microporous graphite catalytic membrane.

[0014] The oxidant is one or more of hydrogen peroxide, sodium hypochlorite, hypochlorous acid, perchloric acid, and ozone; the amount of oxidant added is 2-5 wt.% of the filtrate feed amount; further, the oxidant is preferably hydrogen peroxide, which is an industrial hydrogen peroxide product with a concentration of 30 wt.%, and the amount of oxidant added is 2-4 wt.% of the filtrate feed amount.

[0015] The feed rate of the wet catalytic oxidation reactor is 500-1000 mL / h, the volume ratio of the filtrate to the carbon-based microporous graphite catalytic membrane is (5-10):1, and the hydraulic residence time in the wet catalytic oxidation reactor is 0.5-4 h; preferably, the volume ratio of the filtrate to the carbon-based microporous graphite catalytic membrane is 7:1, the volume of the filtrate is the total feed volume including the oxidant, and the hydraulic residence time in the wet catalytic oxidation reactor is 0.5-1.5 h.

[0016] The activated carbon used in the carbon-based microporous graphite membrane substrate has a specific surface area of ​​500-1000 m². 2 / g, a regular commercially available product.

[0017] In the precursor solution, the concentrations of H2PtCl6 and PdCl2 are both 0.001-0.005 mol / L, and the concentrations of dilute hydrochloric acid and dilute nitric acid in the dilute hydrochloric acid / nitric acid mixed acid solution are both 2-3 wt.%, with the pH of the dilute hydrochloric acid / nitric acid mixed acid solution < 2; furthermore, when dissolving H2PtCl6 and PdCl2, dilute hydrochloric acid and nitric acid are mixed at a mass ratio of 1:1 to prepare a solution with pH < 2, and then H2PtCl6 and PdCl2 are dissolved while maintaining pH < 2; preferably, the concentrations of H2PtCl6 and PdCl2 in the precursor solution are both 0.002 mol / L.

[0018] In the preparation process of the supported carbon-based microporous graphite catalytic membrane, the inert gas in S3 and S5 is either nitrogen or argon, preferably nitrogen. The sintering procedure in S3 is as follows: First stage, heating to 150-200℃ at a heating rate of 1-3℃ / min and holding for 2-4 hours; Second stage, heating to 400-450℃ at a heating rate of 1-3℃ / min and holding for 4-8 hours; Third stage, heating to 800-1500℃ at a heating rate of 1-3℃ / min and holding for 6-10 hours; Fourth stage, after sintering, cooling to 400-450℃ at a cooling rate of 0.5-2℃ / min and holding for 2-6 hours. The sintering procedure in S5 is as follows: heating to 300-600℃ at a heating rate of 1-3℃ / min and holding for 6-8 hours.

[0019] The apparatus used in the method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane includes a ceramic membrane filter and a wet catalytic oxidation reactor. A static mixer A is installed at the inlet end of the ceramic membrane filter, and the inlet end of static mixer A is connected to the formaldehyde wastewater pipeline and the pH adjuster pipeline. The ceramic membrane filter is connected to the wet catalytic oxidation reactor sequentially through a feed pump and a main heat exchanger. A pipeline connected to the jacket of the main heat exchanger is installed at the top of the wet catalytic oxidation reactor, and the outlet of the main heat exchanger jacket is connected to a cooler. The cooler is connected to a pipeline connected to a biochemical system. A static mixer B is installed before the feed pump, and the inlet end of static mixer B is connected to the oxidant pipeline. An acidity sensor is installed between static mixer B and the feed pump, and a flow sensor is installed between the feed pump and the main heat exchanger. A temperature sensor and a pressure sensor are also installed on the wet catalytic oxidation reactor.

[0020] Preferably, the wet catalytic oxidation reactor includes an outer shell and multiple internal catalytic oxidation tubes. The catalytic oxidation tubes are vertically fixed by a support plate, and catalytic membranes and catalytic membrane partitions are alternately arranged inside the tubes. The bottom and top of the catalytic oxidation tubes are supported by catalyst support grids. The top and bottom of adjacent catalytic oxidation tubes are connected by connecting elbows. A formaldehyde wastewater inlet is provided at the bottom and a formaldehyde wastewater outlet is provided at the top. A heating medium inlet and a heating medium outlet are provided on the shell side of the wet catalytic oxidation reactor, and a drain outlet is also provided. A temperature sensor is installed on the outer shell at the corresponding location of the heating medium space through a temperature sensor interface, and a pressure sensor is installed on the pipe of the formaldehyde wastewater outlet at the top through a pressure sensor interface.

[0021] The assembly method of the catalytic oxidation tube is as follows: A layer of catalytic membrane and a layer of catalytic membrane separator are alternately stacked inside the tube. The catalytic membrane separator consists of a high-temperature resistant fluorosilicone rubber ring and a stainless steel porous mesh. During installation, a metal rod is used to smoothly push the rubber ring, with a small amount of high-temperature inert grease applied to its outer side, into the tube. The outer edge of the rubber ring is tightly sealed against the inner wall of the tube. Then, the stainless steel porous mesh is placed inside to effectively block short-circuiting of wastewater. The bottom and top of the catalytic oxidation tube are supported and compacted by catalyst support grids to complete the filling. The catalyst support grids are porous, perforated, and transparent stainless steel plate structures. Grooves are provided at corresponding positions on the catalytic tube, and ring springs are used to fix the catalyst support grids. The stainless steel porous mesh can be replaced with porous structures of other thicknesses to adjust the volume of the catalytic membrane in the catalytic oxidation tube, thereby adjusting the amount of catalytic membrane used.

[0022] Preferably, the ceramic membrane filter is also connected to a cleaning fluid line for periodic cleaning of the internal ceramic membrane.

[0023] Preferably, the supported carbon-based microporous graphite catalytic membrane comprises a carbon-based microporous graphite membrane substrate and active components, the noble metals platinum and palladium, supported on the substrate; based on 100% of the mass of the carbon-based microporous graphite membrane substrate before calcination, the carbon-based microporous graphite membrane substrate comprises the following raw materials by mass percentage: phenolic resin: 5-10%, polymethyl methacrylate: 10-17%, coal tar pitch: 30-35%, activated carbon: 40-45%, nano-silicon carbide: 1-2%, boric acid: 1-2%, and hydroxymethyl cellulose: 1-2%; its preparation method includes the following steps: S1. Phenolic resin, polymethyl methacrylate, coal tar pitch and ethanol are mixed and added to an alumina ball mill jar for mechanical ball milling for 12-36 hours. Then activated carbon is added and ball milling continues for 2-4 hours. After washing with water, filtration and drying at 80°C are carried out to obtain matrix powder material. The amount of ethanol used is twice the mass of the raw materials in S1. S2. The matrix powder material obtained in step S1 is mixed with nano-silicon carbide, boric acid and hydroxymethyl cellulose for 4-8 hours to obtain the mixed powder material. S3. The mixed powder material is mechanically dry-pressed into a circular sheet shape with a thickness of 8 mm and a dry-pressing strength of 60 MPa. Then, it is sintered in a nitrogen atmosphere. In the first stage, the temperature is increased to 180℃ at a heating rate of 2℃ / min and held for 3 hours. In the second stage, the temperature is increased to 425℃ at a heating rate of 2℃ / min and held for 6 hours. In the third stage, the temperature is increased to 1200℃ at a heating rate of 2℃ / min and held for 8 hours. In the fourth stage, after sintering, the temperature is decreased to 400℃ at a cooling rate of 1℃ / min and held for 6 hours. Then, it is naturally cooled to room temperature to obtain a carbon-based microporous graphite film. S4. Prepare a mixed acid solution with pH < 2 by mixing dilute hydrochloric acid and nitric acid at a mass ratio of 1:1. Then, dissolve H2PtCl6 and PdCl2, maintaining the pH < 2, and continue stirring for 10 hours to prepare a precursor solution. The concentrations of H2PtCl6 and PdCl2 are both 0.002 mol / L, and the concentrations of dilute hydrochloric acid and dilute nitric acid in the mixed acid solution are 3 wt.%. S5. The carbon-based microporous graphite membrane obtained in S3 is immersed in the precursor solution in S4 for 18 hours. After immersion, it is drained and dried at 100°C. Then, under a nitrogen atmosphere, the temperature is raised to 400°C at a rate of 2°C / min and held for 7 hours. After sintering, it is naturally cooled to room temperature to obtain the supported carbon-based microporous graphite catalytic membrane.

[0024] Furthermore, after optimization and adjustment of reaction conditions and operating parameters, the above method and catalytic membrane are also applicable to the treatment of other high-concentration, recalcitrant organic wastewater.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The supported carbon-based microporous graphite catalytic membrane of the present invention utilizes the well-developed microporous structure and high specific surface area of ​​the carbon-based microporous graphite matrix to improve the dispersibility of active components and enhance the adsorption capacity of pollutants. At the same time, the Pt / Pd active components can effectively catalyze the decomposition of oxidants to generate active free radicals, which solves the problem that traditional powder catalysts are easily lost with wastewater and the catalytic activity decreases. Moreover, the concentration of precursors is controlled during the preparation process, reducing the amount of precious metals used and making the cost more controllable.

[0026] (2) The method for treating formaldehyde wastewater of the present invention adopts a deep coupling of a supported carbon-based microporous graphite catalytic membrane and low-temperature wet catalytic oxidation. The reaction conditions are mild and can rapidly degrade formaldehyde and coexisting toxic pollutants such as phenols and amino compounds. The microporous structure of the catalytic membrane enables the interception and adsorption of pollutants. At the same time, the layered and orderly stacked catalytic membrane design increases the contact area between the catalytic membrane and the wastewater, improves the mass transfer efficiency and catalytic degradation effect, and has excellent formaldehyde removal effect. It can also improve the biodegradability of wastewater and solve the limitations of traditional treatment technologies such as low efficiency, many by-products, and secondary pollution.

[0027] (3) The device used in the method for treating formaldehyde wastewater of the present invention has a reasonable structural design and combines ceramic membrane filtration, catalytic oxidation and heat exchange cooling functions to achieve continuous wastewater treatment; at the same time, the ceramic membrane can be cleaned regularly to extend its service life and meet the treatment needs of formaldehyde wastewater. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the apparatus used in the wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane according to the present invention. Figure 2 This is a schematic diagram of the structure of the wet catalytic oxidation reactor of the present invention; Figure 3 This is an internal assembly diagram of the catalytic oxidation tube inside the wet catalytic oxidation reactor of the present invention; Figure 4 This is a scanning electron microscope image of the surface of the carbon-based microporous graphite film prepared in Example 1 of the present invention; Figure 5 This is a scanning electron microscope image of a cross-section of a carbon-based microporous graphite membrane prepared in Example 1 of the present invention.

[0029] In the diagram: 1. Ceramic membrane filter; 2. Wet catalytic oxidation reactor; 201. Outer shell; 202. Formaldehyde wastewater inlet; 203. Catalytic oxidation pipe; 204. Connecting elbow; 205. Support plate; 206. Formaldehyde wastewater outlet; 207. Drain; 208. Temperature sensor interface; 209. Heating medium outlet; 210. Heating medium inlet; 211. Pressure sensor interface; 212. Catalyst support grid; 213. Catalytic membrane; 214. Catalytic membrane partition; 3. Formaldehyde wastewater pipeline; 4. pH adjuster pipeline; 5. Oxidant pipeline; 6. Main heat exchanger; 7. Cooler; 8. Cleaning fluid pipeline; 9. Biochemical system; 10. Feed pump; 11. Acidity sensor; 12. Flow sensor; 13. Static mixer A; 14. Static mixer B. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to the embodiments and comparative examples. Unless otherwise specified, the raw materials used in the embodiments and comparative examples are all conventional commercial raw materials, and solid raw materials are preferably commercially available powder products. Unless otherwise specified, the process methods used are conventional methods in the art, and all percentages involved are mass percentages. The formaldehyde wastewater indicators before dilute hydrochloric acid treatment used in the embodiments and comparative examples of the present invention are: COD of 12779 mg / L, formaldehyde content of 7530 mg / L, and B / C ratio of 0.2.

[0031] The raw materials and apparatus used in the examples and comparative examples are described below: Phenolic resin: 2123 thermosetting phenolic resin powder, 180 mesh, Jiangsu Langsheng New Material Technology Co., Ltd.; Coal tar pitch: Coal-based pitch powder, Hebei Fengtaiyuan Energy Technology Co., Ltd.; Nano-silicon carbide: 500nm, Shanghai McLean Biotechnology Co., Ltd.; Boric acid: purity 99.5 wt.%, Laiyang Kangde Chemical Co., Ltd.; Hydroxymethyl cellulose: viscosity 300-800 mPa·s, Sinopharm Chemical Reagent Co., Ltd. Ceramic membrane filter: α-alumina-based ceramic membrane filter with a filtration accuracy of 1μm.

[0032] like Figures 1-3As shown, the apparatus used in the method of wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane includes a ceramic membrane filter 1 and a wet catalytic oxidation reactor 2. A static mixer A13 is installed at the inlet end of the ceramic membrane filter 1, and the inlet end of the static mixer A13 is connected to the formaldehyde wastewater pipeline 3 and the pH adjuster pipeline 4. The ceramic membrane filter 1 is connected to the wet catalytic oxidation reactor 2 sequentially through a feed pump 10 and a main heat exchanger 6. The top of the wet catalytic oxidation reactor 2 is fitted with a jacket connecting to the main heat exchanger 6. The main heat exchanger 6 is connected to the jacket outlet of the main heat exchanger 6 and the cooler 7. The cooler 7 is connected to the biochemical system 9. A static mixer B14 is installed before the feed pump 10. The inlet of the static mixer B14 is connected to the oxidant pipeline 5. An acidity sensor 11 is installed between the static mixer B14 and the feed pump 10. A flow sensor 12 is installed between the feed pump 10 and the main heat exchanger 6. A temperature sensor and a pressure sensor are also installed on the wet catalytic oxidation reactor 2. The ceramic membrane filter 1 is also connected to the cleaning liquid pipeline 8.

[0033] The wet catalytic oxidation reactor 2 includes an outer shell 201 and multiple internal catalytic oxidation tubes 203. The catalytic oxidation tubes 203 are vertically fixed by a support plate 205. Catalytic membranes 213 and catalytic membrane partitions 214 are alternately arranged inside the tubes. The bottom and top ends of the catalytic oxidation tubes 203 are supported by catalyst support grids 212. The top and bottom of adjacent catalytic oxidation tubes 203 are connected by connecting elbows 204. A formaldehyde wastewater inlet 202 is provided at the bottom and a formaldehyde wastewater outlet 206 is provided at the top. A heating medium inlet 210 and a heating medium outlet 209 are provided on the shell side of the wet catalytic oxidation reactor 2, and a drain outlet 207 is also provided. A temperature sensor is installed on the outer shell 201 at the corresponding position of the heating medium space through a temperature sensor interface 208, and a pressure sensor is installed on the pipe of the formaldehyde wastewater outlet 206 at the top through a pressure sensor interface 211.

[0034] The assembly method of the catalytic oxidation tube 203 is as follows: a layer of catalytic membrane 213 and a layer of catalytic membrane separator 214 are alternately stacked in the tube. The catalytic membrane separator 214 is composed of a high-temperature resistant fluorosilicone rubber ring and a stainless steel porous mesh. During installation, a metal rod is used to smoothly push the rubber ring with a small amount of high-temperature inert grease applied to the outside into the tube. The outer edge of the rubber is tightly sealed to the inner wall of the tube. Then, the stainless steel porous mesh is placed in to effectively block the short flow of wastewater bypass. The bottom and top of the catalytic oxidation tube 203 are supported and pressed tightly by the catalyst support grid 212 to complete the filling. The catalyst support grid 212 is a porous and transparent stainless steel plate structure. The corresponding position of the catalytic tube is provided with a groove, and the catalyst support grid 212 is fixed by a ring spring.

[0035] The following embodiments and comparative examples were all carried out using the above-described apparatus.

[0036] The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane includes the following steps: (1) Formaldehyde wastewater with COD of 8000-15000 mg / L and formaldehyde concentration of 5000-10000 mg / L is mixed with 10-17 wt.% dilute hydrochloric acid delivered by pH adjuster pipeline 4 through static mixer A13 to adjust the pH to 3-5, and then enters ceramic membrane filter 1. The wastewater temperature is controlled at 15-40℃ for filtration to remove suspended solids, colloidal impurities and macromolecular substances to obtain filtrate; (2) The filtrate is mixed again with hydrogen peroxide transported by oxidant pipeline 5 through static mixer B14. The amount of hydrogen peroxide added is 2-5 wt.% of the filtrate feed amount. It is transported by feed pump 10 to main heat exchanger 6 for preheating to 110-140℃. Then it enters wet catalytic oxidation reactor 2 through formaldehyde wastewater pipeline 3. The feed rate of wet catalytic oxidation reactor 2 is 500-1000 mL / h. The volume ratio of filtrate to catalytic membrane 213 is 7:1. The hydraulic residence time in wet catalytic oxidation reactor 2 is 1-2h. Catalytic degradation reaction is carried out at 140-180℃ and 0.5-1.0 MPa. The treated liquid after reaction enters main heat exchanger 6 to recover heat, then is cooled by cooler 7, and discharged into subsequent biochemical system after pH adjustment.

[0037] Example 1 The supported carbon-based microporous graphite catalytic membrane comprises a carbon-based microporous graphite membrane substrate and active components, the noble metals platinum and palladium, supported on the substrate. Based on 100% mass of the carbon-based microporous graphite membrane substrate before calcination, the carbon-based microporous graphite membrane substrate comprises the following raw materials by mass percentage: phenolic resin: 5%, polymethyl methacrylate: 10%, coal tar pitch: 35%, activated carbon: 45%, nano-silicon carbide: 2%, boric acid: 1%, and hydroxymethyl cellulose: 2%. Its preparation method includes the following steps: S1. Phenolic resin, polymethyl methacrylate, coal tar pitch and ethanol are mixed and added to an alumina ball mill jar for mechanical ball milling for 12 hours. Then activated carbon is added and ball milling is continued for 3 hours. After washing with water, filtration and drying at 80°C, the matrix powder material is obtained. The amount of ethanol used is twice the mass of the raw materials in S1. S2. The matrix powder material obtained in step S1 is mixed with nano-silicon carbide, boric acid and hydroxymethyl cellulose for 6 hours to obtain the mixed powder material. S3. The mixed powder material was mechanically dry-pressed into a circular sheet shape with a thickness of 8 mm and a dry-pressing strength of 60 MPa. It was then sintered under a nitrogen atmosphere. The first stage involved heating at a rate of 2℃ / min to 180℃ and holding for 3 hours; the second stage involved heating at a rate of 2℃ / min to 425℃ and holding for 6 hours; the third stage involved heating at a rate of 2℃ / min to 1200℃ and holding for 8 hours; and the fourth stage, after sintering, cooling at a rate of 1℃ / min to 400℃ and holding for 6 hours, followed by natural cooling to room temperature to obtain a carbon-based microporous graphite membrane. The SEM image of the carbon-based microporous graphite membrane is shown below. Figure 4 , Figure 5 ; S4. Prepare a mixed acid solution with pH < 2 by mixing dilute hydrochloric acid and nitric acid at a mass ratio of 1:1. Then, dissolve H2PtCl6 and PdCl2, maintaining the pH < 2, and continue stirring for 10 hours to prepare a precursor solution. The concentrations of H2PtCl6 and PdCl2 are both 0.002 mol / L, and the concentrations of dilute hydrochloric acid and dilute nitric acid in the mixed acid solution are 3 wt.%. S5. Immerse the carbon-based microporous graphite membrane obtained in step S3 in the precursor solution of S4 for 18 hours. After immersion, drain and dry at 100°C. Then, under a nitrogen atmosphere, maintain a heating rate of 2°C / min to raise the temperature to 400°C and hold for 7 hours. After sintering, allow it to cool naturally to room temperature to obtain the supported carbon-based microporous graphite catalytic membrane.

[0038] In use, the supported carbon-based microporous graphite catalytic membrane 213 is placed in the tube with alternating layers of catalytic membrane 213 and catalytic membrane partition 214. The bottom and top of the catalytic oxidation tube 203 are supported and compacted by the catalyst support grid 212 to complete the filling and then proceed with the subsequent formaldehyde wastewater treatment.

[0039] The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane includes the following steps: (1) Formaldehyde wastewater with COD of 12779 mg / L, formaldehyde concentration of 7530 mg / L, and B / C ratio of 0.2 is mixed with 10 wt.% dilute hydrochloric acid delivered by pH adjuster pipeline 4 through static mixer A13 to adjust the pH to 5, and then enters ceramic membrane filter 1. The wastewater temperature is controlled at 40℃ for filtration to remove suspended solids, colloidal impurities and macromolecular substances to obtain filtrate. (2) The filtrate is mixed again with hydrogen peroxide transported by oxidant pipeline 5 through static mixer B14. The amount of hydrogen peroxide added is 2wt.% of the filtrate feed amount. It is transported by feed pump 10 to main heat exchanger 6 for preheating to 140°C. Then it enters wet catalytic oxidation reactor 2 through formaldehyde wastewater pipeline 3. The feed rate of wet catalytic oxidation reactor 2 is 800mL / h. The volume ratio of filtrate to catalytic membrane 213 is 7:1. The hydraulic residence time in wet catalytic oxidation reactor 2 is 1.5h. Catalytic degradation reaction is carried out at 160°C and 0.5MPa. The treated liquid after reaction enters main heat exchanger 6 to recover heat, then is cooled by cooler 7, and discharged into subsequent biochemical system after pH adjustment.

[0040] Example 2 The supported carbon-based microporous graphite catalytic membrane comprises a carbon-based microporous graphite membrane substrate and active components, the noble metals platinum and palladium, supported on the substrate. Based on 100% mass of the carbon-based microporous graphite membrane substrate before calcination, the substrate comprises the following raw materials by mass percentage: phenolic resin: 7%, polymethyl methacrylate: 14%, coal tar pitch: 33%, activated carbon: 42%, nano-silicon carbide: 1%, boric acid: 2%, and hydroxymethyl cellulose: 1%. Its preparation method includes the following steps: S1. Phenolic resin, polymethyl methacrylate, coal tar pitch and ethanol are mixed and added to an alumina ball mill jar for mechanical ball milling for 36 hours. Then activated carbon is added and ball milling continues for 2 hours. After washing with water, filtration and drying at 80°C, the matrix powder material is obtained. The amount of ethanol used is twice the mass of the raw materials in S1. S2. The matrix powder material obtained in step S1 is mixed with nano-silicon carbide, boric acid and hydroxymethyl cellulose for 4 hours to obtain the mixed powder material. S3. The mixed powder material is mechanically dry-pressed into a circular sheet shape with a thickness of 8 mm and a dry-pressing strength of 60 MPa. Then, it is sintered in a nitrogen atmosphere. In the first stage, the temperature is increased to 180℃ at a heating rate of 2℃ / min and held for 3 hours. In the second stage, the temperature is increased to 425℃ at a heating rate of 2℃ / min and held for 6 hours. In the third stage, the temperature is increased to 1200℃ at a heating rate of 2℃ / min and held for 8 hours. In the fourth stage, after sintering, the temperature is decreased to 400℃ at a cooling rate of 1℃ / min and held for 6 hours. Then, it is naturally cooled to room temperature to obtain a carbon-based microporous graphite film. S4. Prepare a mixed acid solution with pH < 2 by mixing dilute hydrochloric acid and nitric acid at a mass ratio of 1:1. Then, dissolve H2PtCl6 and PdCl2, maintaining the pH < 2, and continue stirring for 10 hours to prepare a precursor solution. The concentrations of H2PtCl6 and PdCl2 are both 0.002 mol / L, and the concentrations of dilute hydrochloric acid and dilute nitric acid in the mixed acid solution are 3 wt.%. S5. Immerse the carbon-based microporous graphite membrane obtained in step S3 in the precursor solution of S4 for 18 hours. After immersion, drain and dry at 100°C. Then, under a nitrogen atmosphere, maintain a heating rate of 2°C / min to raise the temperature to 400°C and hold for 7 hours. After sintering, allow it to cool naturally to room temperature to obtain the supported carbon-based microporous graphite catalytic membrane.

[0041] In use, the supported carbon-based microporous graphite catalytic membrane 213 is placed in the tube with alternating layers of catalytic membrane 213 and catalytic membrane partition 214. The bottom and top of the catalytic oxidation tube 203 are supported and compacted by the catalyst support grid 212 to complete the filling and then proceed with the subsequent formaldehyde wastewater treatment.

[0042] The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane includes the following steps: (1) Formaldehyde wastewater with COD of 12779 mg / L, formaldehyde concentration of 7530 mg / L, and B / C ratio of 0.2 is mixed with 15 wt.% dilute hydrochloric acid delivered by pH adjuster pipeline 4 through static mixer A13 to adjust the pH to 4, and then enters ceramic membrane filter 1. The wastewater temperature is controlled at 30℃ for filtration to remove suspended solids, colloidal impurities and macromolecular substances to obtain filtrate; (2) The filtrate is mixed again with hydrogen peroxide transported by oxidant pipeline 5 through static mixer B14. The amount of hydrogen peroxide added is 4 wt.% of the filtrate feed amount. It is transported by feed pump 10 to main heat exchanger 6 for preheating to 120°C. Then it enters wet catalytic oxidation reactor 2 through formaldehyde wastewater pipeline 3. The feed rate of wet catalytic oxidation reactor 2 is 500 mL / h. The volume ratio of filtrate to catalytic membrane 213 is 7:1. The hydraulic residence time in wet catalytic oxidation reactor 2 is 1 h. Catalytic degradation reaction is carried out at 140°C and 0.3 MPa. The treated liquid after reaction enters main heat exchanger 6 to recover heat, then is cooled by cooler 7, and discharged into subsequent biochemical system after pH adjustment.

[0043] Example 3 The supported carbon-based microporous graphite catalytic membrane comprises a carbon-based microporous graphite membrane substrate and active components, the noble metals platinum and palladium, supported on the substrate. Based on 100% mass of the carbon-based microporous graphite membrane substrate before calcination, the carbon-based microporous graphite membrane substrate comprises the following raw materials by mass percentage: phenolic resin: 10%, polymethyl methacrylate: 17%, coal tar pitch: 30%, activated carbon: 40%, nano-silicon carbide: 1%, boric acid: 1%, and hydroxymethyl cellulose: 1%. Its preparation method includes the following steps: S1. Phenolic resin, polymethyl methacrylate, coal tar pitch and ethanol are mixed and added to an alumina ball mill jar for mechanical ball milling for 24 hours. Then activated carbon is added and ball milling is continued for 4 hours. After washing with water, filtration and drying at 80°C are carried out to obtain matrix powder material. The amount of ethanol used is twice the mass of the raw materials in S1. S2. The matrix powder material obtained in step S1 is mixed with nano-silicon carbide, boric acid and hydroxymethyl cellulose for 6 hours to obtain the mixed powder material. S3. The mixed powder material is mechanically dry-pressed into a circular sheet shape with a thickness of 8 mm and a dry-pressing strength of 60 MPa. Then, it is sintered in a nitrogen atmosphere. In the first stage, the temperature is increased to 180℃ at a heating rate of 2℃ / min and held for 3 hours. In the second stage, the temperature is increased to 425℃ at a heating rate of 2℃ / min and held for 6 hours. In the third stage, the temperature is increased to 1200℃ at a heating rate of 2℃ / min and held for 8 hours. In the fourth stage, after sintering, the temperature is decreased to 400℃ at a cooling rate of 1℃ / min and held for 6 hours. Then, it is naturally cooled to room temperature to obtain a carbon-based microporous graphite film. S4. Prepare a mixed acid solution with pH < 2 by mixing dilute hydrochloric acid and nitric acid at a mass ratio of 1:1. Then, dissolve H2PtCl6 and PdCl2, maintaining the pH < 2, and continue stirring for 10 hours to prepare a precursor solution. The concentrations of H2PtCl6 and PdCl2 are both 0.002 mol / L, and the concentrations of dilute hydrochloric acid and dilute nitric acid in the mixed acid solution are 3 wt.%. S5. Immerse the carbon-based microporous graphite membrane obtained in step S3 in the precursor solution of S4 for 18 hours. After immersion, drain and dry at 100°C. Then, under a nitrogen atmosphere, maintain a heating rate of 2°C / min to raise the temperature to 400°C and hold for 7 hours. After sintering, allow it to cool naturally to room temperature to obtain the supported carbon-based microporous graphite catalytic membrane.

[0044] In use, the supported carbon-based microporous graphite catalytic membrane 213 is placed in the tube with alternating layers of catalytic membrane 213 and catalytic membrane partition 214. The bottom and top of the catalytic oxidation tube 203 are supported and compacted by the catalyst support grid 212 to complete the filling and then proceed with the subsequent formaldehyde wastewater treatment.

[0045] The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane includes the following steps: (1) Formaldehyde wastewater with COD of 12779 mg / L, formaldehyde concentration of 7530 mg / L, and B / C ratio of 0.2 is mixed with 17 wt.% dilute hydrochloric acid delivered by pH adjuster pipeline 4 through static mixer A13 to adjust the pH to 3, and then enters ceramic membrane filter 1. The wastewater temperature is controlled at 15℃ for filtration to remove suspended solids, colloidal impurities and macromolecular substances, and obtain filtrate. (2) The filtrate is mixed again with hydrogen peroxide transported by oxidant pipeline 5 through static mixer B14. The amount of hydrogen peroxide added is 3 wt.% of the filtrate feed amount. It is transported by feed pump 10 to main heat exchanger 6 for preheating to 110°C. Then it enters wet catalytic oxidation reactor 2 through formaldehyde wastewater pipeline 3. The feed rate of wet catalytic oxidation reactor 2 is 1000 mL / h. The volume ratio of filtrate to carbon-based microporous graphite catalytic membrane 213 is 7:1. The hydraulic residence time in wet catalytic oxidation reactor 2 is 0.5 h. Catalytic degradation reaction is carried out at 180°C and 1.0 MPa. The treated liquid after reaction enters main heat exchanger 6 to recover heat, then is cooled by cooler 7, and discharged into subsequent biochemical system after pH adjustment.

[0046] Comparative Example 1 The difference between this comparative example and Example 3 is that the effective component in the matrix powder material is activated carbon, while the other raw materials, dosages, and formaldehyde wastewater treatment methods are the same as in Example 3.

[0047] Comparative Example 2 The difference between this comparative example and Example 3 is that the catalytic oxidation tube is directly filled with α-alumina microspheres of equal volume, and the microspheres are loaded using the platinum-palladium catalyst loading step in Example 3. The other formaldehyde wastewater treatment methods are the same as in Example 3.

[0048] Comparative Example 3 The difference between this comparative example and Example 3 is that, based on the mass of the carbon-based microporous graphite membrane substrate before calcination as 100%, the carbon-based microporous graphite membrane substrate includes the following raw materials by mass percentage: phenolic resin: 15%, polymethyl methacrylate: 17%, coal tar pitch: 30%, activated carbon: 35%, nano silicon carbide: 1%, boric acid: 1%, and hydroxymethyl cellulose: 1%; the remaining raw materials and processes are the same as in Example 3.

[0049] The carbon-based microporous graphite membrane obtained after sintering in this comparative example had a low yield. During the sintering process, the membrane shrank severely and warped and deformed, making it unsuitable for subsequent loading of active components.

[0050] The wastewater treatment results obtained at each stage in the formaldehyde wastewater treatment process of the above embodiments and comparative examples are shown in Table 1 below. The water flux of the supported carbon-based microporous graphite catalytic membranes prepared in Examples 1-3 and Comparative Example 3 before and after loading was tested. The test method was as follows: a disc-shaped supported carbon-based microporous graphite catalytic membrane or a carbon-based microporous graphite membrane was loaded into a single-tube fixed-bed reactor, sealed at both ends, with a membrane thickness of 8 mm and a diameter of 25 mm. First, nitrogen was used for purging for 15 min, followed by the introduction of pure water at 0.10 MPa and 25°C. After stabilization for 10 min, the measurement stage was initiated, and the stable permeate volume V was recorded. The pure water flux F was calculated using the formula: F = V / (A·t), where the unit of F is L / (m³). 2 ·h), V is the permeate volume (L), and A is the effective membrane area (m²). 2 ), t is the transmission time (h), the test was repeated three times, and the average value was taken. The test results are shown in Table 2.

[0051] Table 1. Formaldehyde wastewater treatment results of the comparative examples.

[0052] Table 2. Pure water flux test results for Examples 1-3 and Comparative Example 3

[0053] As shown in Tables 1 and 2, Examples 1, 2, and 3 all employed Pt / Pd bimetallic supported carbon-based microporous graphite catalytic membranes. Combined with ceramic membrane pretreatment and a low-temperature wet catalytic oxidation process, these membranes demonstrated excellent overall treatment performance for high-concentration formaldehyde wastewater. The data in Table 2, along with... Figure 1 and Figure 2 In summary, the carbon-based microporous graphite membrane exhibits a well-developed microporous structure, which effectively improves the uniformity of the dispersion of the active metal components and enhances the catalyst's adsorption and enrichment capacity for formaldehyde and organic pollutants. Pure water flux testing verifies that the catalytic membrane maintains good water permeability even after loading the active components. Relying on microporous adsorption and the synergistic catalytic effect of the Pt / Pd bimetallic compounds, efficient and deep oxidative degradation of formaldehyde can be achieved. Simultaneously, the alternating stacking of sheet-like catalytic membranes within the reactor prevents wastewater bypass and short-circuiting, improving mass transfer and catalytic contact efficiency. Ultimately, this results in formaldehyde degradation, a significant reduction in COD, and an increase in the wastewater B / C ratio from 0.2 to 0.4, leading to a substantial improvement in biodegradability.

[0054] Compared with Example 3, Comparative Example 1 only used activated carbon as a carrier and did not use phenolic resin, coal tar pitch, nano silicon carbide, etc. to construct a carbon-based microporous graphite framework. The active component Pt / Pd was unevenly loaded and easily lost, and the synergistic effect of adsorption and catalysis was lacking, which led to low formaldehyde removal rate, limited COD degradation, and no significant improvement in B / C ratio.

[0055] Compared with Example 3, Comparative Example 2 uses α-alumina microspheres to replace the carbon-based microporous graphite catalytic membrane. The specific surface area of ​​the alumina microspheres is much lower than that of the carbon-based membrane, resulting in an insufficient number of active sites. Furthermore, the packing method is prone to channeling and short-circuiting, leading to insufficient contact between the wastewater and the catalyst and low mass transfer efficiency. With a feed rate of 1000 mL / h and a reaction time of 0.5 h, the treatment capacity is limited. Although it has a certain catalytic effect, the treatment effect is significantly lower than that of the membrane structure example.

[0056] Compared with Example 3, Comparative Example 3 had a higher proportion of phenolic resin (15%) and polymethyl methacrylate (PMMA) (17%) in the matrix formulation, while the proportion of activated carbon decreased to 35%. The imbalance between binder and pore-forming agent led to excessive membrane shrinkage and warping during sintering, resulting in a significant decrease in adsorption performance and active component loading. The synergistic function of catalysis and separation also failed. Furthermore, the data in Table 2 showed that the increased proportion of phenolic resin caused blockage of the microporous structure, which could not provide sites for the subsequent loading of active components, resulting in poor formaldehyde and COD degradation and high concentration of pollutants in the effluent.

[0057] Based on the above treatment process, fatigue experiments were conducted on Example 3 and Comparative Example 2. That is, under the condition of keeping the reaction conditions unchanged, a continuous experiment was carried out with a liquid inlet rate of 1000 mL / h. The formaldehyde concentration and COD of the effluent were continuously monitored to evaluate the stability of the catalytic membrane and the loss of active components. After 50 hours of continuous operation, the results are shown in Table 3.

[0058] Table 3. Results of fatigue test

[0059] As shown in Table 3, the supported carbon-based microporous graphite catalytic membrane used in Example 3 maintained a high degradation efficiency after 50 hours of continuous operation. The carbon-based graphite membrane carrier was firmly bonded to the precious metal active components, the membrane structure was stable, the loss of active components was low under continuous water flow, and the catalytic membrane did not show obvious deactivation.

[0060] Comparative Example 2 uses α After 50 hours of operation, the COD of the effluent supporting the alumina microspheres increased to 10753 mg / L and the formaldehyde level reached 5084 mg / L. The degradation efficiency of COD and formaldehyde decreased significantly, and the catalytic activity was significantly reduced. This result indicates that the interaction between the alumina microspheres and the active components is weak. Under high temperature, high pressure and hydraulic scouring, the active components are rapidly detached and dissolved, and the effective catalytic sites are continuously reduced, eventually leading to severe fatigue and deactivation of the catalyst.

Claims

1. A method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane, characterized in that, Includes the following steps: (1) The pH of formaldehyde wastewater is adjusted to 3-5 using dilute hydrochloric acid with a concentration of 10-17wt.%. Then, the wastewater temperature is controlled at 15-40℃ and filtered through a ceramic membrane to remove suspended solids, colloidal impurities and macromolecular substances to obtain filtrate. (2) Add oxidant to the filtrate, preheat it through the main heat exchanger and then enter the wet catalytic oxidation reactor. Catalytic degradation is carried out under the action of sheet-supported carbon-based microporous graphite catalytic membrane. The temperature is controlled at 140-180℃ and the pressure is 0.3-1.0MPa to obtain the treated liquid. After cooling through the main heat exchanger and cooler and adjusting the pH, it is discharged into the subsequent biochemical system. The supported carbon-based microporous graphite catalytic membrane comprises a carbon-based microporous graphite membrane substrate and active components, the noble metals platinum and palladium, supported on the substrate. Based on 100% of the mass of the carbon-based microporous graphite membrane substrate before calcination, the carbon-based microporous graphite membrane substrate comprises the following raw materials by mass percentage: phenolic resin: 5-10%, polymethyl methacrylate: 10-17%, coal tar pitch: 30-35%, activated carbon: 40-45%, nano-silicon carbide: 1-2%, boric acid: 1-2%, and hydroxymethyl cellulose: 1-2%. The preparation process of the supported carbon-based microporous graphite catalytic membrane includes the following steps: S1. Phenolic resin, polymethyl methacrylate, coal tar pitch and ethanol are mixed and added to an alumina ball mill jar for mechanical ball milling for 12-36 hours. Then activated carbon is added and ball milling is continued for 2-4 hours. After washing with water, filtration and drying are performed to obtain the matrix powder material. S2. The matrix powder material obtained in step S1 is mixed with nano-silicon carbide, boric acid and hydroxymethyl cellulose for 4-8 hours to obtain the mixed powder material. S3. The mixed powder material is mechanically dry-pressed and then sintered in an inert gas atmosphere. After sintering, it is cooled to room temperature to obtain a carbon-based microporous graphite film. S4. Dissolve H2PtCl6 and PdCl2 in a dilute hydrochloric acid / nitric acid mixed acid solution and stir for 8-12 hours to prepare a precursor solution; S5. Immerse the carbon-based microporous graphite membrane obtained in step S3 in the precursor solution of step S4 for 12-24 hours. After immersion, drain the membrane and dry it at 80-120℃. Then, sinter it in an inert gas atmosphere and cool it to room temperature after sintering to obtain a supported carbon-based microporous graphite catalytic membrane. The formaldehyde wastewater parameters before dilute hydrochloric acid treatment are: COD: 8000-15000 mg / L, formaldehyde: 5000-10000 mg / L.

2. The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane according to claim 1, characterized in that, The oxidant is one or more of hydrogen peroxide, sodium hypochlorite, hypochlorous acid, perchloric acid, and ozone; the amount of oxidant added is 2-5 wt.% of the filtrate feed.

3. The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane according to claim 1, characterized in that, The feed rate of the wet catalytic oxidation reactor is 500-1000 mL / h, the volume ratio of the filtrate to the supported carbon-based microporous graphite catalytic membrane is (5-10):1, and the hydraulic residence time in the wet catalytic oxidation reactor is 0.5-4 h.

4. The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane according to claim 1, characterized in that, Activated carbon has a specific surface area of ​​500-1000 m². 2 / g.

5. The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane according to claim 1, characterized in that, The mechanically pressed product is in the shape of a disc, with a thickness of 5-10 mm and a dry pressing strength of 30-100 MPa.

6. The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane according to claim 1, characterized in that, In the precursor solution, the concentrations of H2PtCl6 and PdCl2 are both 0.001-0.005 mol / L, and the concentrations of dilute hydrochloric acid and dilute nitric acid in the dilute hydrochloric acid / nitric acid mixed acid solution are both 2-3 wt.%, with a pH < 2.

7. The method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane according to claim 1, characterized in that, The inert gas in steps S3 and S5 is either nitrogen or argon; the sintering procedure in S3 is as follows: in the first stage, the temperature is raised to 150-200℃ at a heating rate of 1-3℃ / min and held for 2-4 hours. The second stage involves heating at a rate of 1-3℃ / min to 400-450℃ and holding for 4-8 hours. The third stage involves heating at a rate of 1-3℃ / min to 800-1500℃ and holding for 6-10 hours. The fourth stage involves cooling at a rate of 0.5-2℃ / min to 400-450℃ and holding for 2-6 hours. The sintering procedure in S5 is as follows: heating at a rate of 1-3℃ / min to 300-600℃ and holding for 6-8 hours.

8. An apparatus used in a method for wet catalytic oxidation treatment of formaldehyde wastewater using a supported carbon-based microporous graphite catalytic membrane according to any one of claims 1-7, characterized in that, The system includes a ceramic membrane filter (1) and a wet catalytic oxidation reactor (2). A static mixer A (13) is installed at the inlet end of the ceramic membrane filter (1). The inlet end of the static mixer A (13) is connected to a formaldehyde wastewater pipeline (3) and a pH adjuster pipeline (4). The ceramic membrane filter (1) is connected to the wet catalytic oxidation reactor (2) sequentially via a feed pump (10) and a main heat exchanger (6). A pipeline connected to the jacket of the main heat exchanger (6) is installed at the top of the wet catalytic oxidation reactor (2). The jacket outlet is connected to the cooler (7), and the cooler (7) is provided with a pipeline connected to the biochemical system (9); a static mixer B (14) is provided before the feed pump (10), the liquid inlet of the static mixer B (14) is connected to the oxidant pipeline (5), an acidity sensor (11) is provided between the static mixer B (14) and the feed pump (10), a flow sensor (12) is provided between the feed pump (10) and the main heat exchanger (6), and a temperature sensor and a pressure sensor are also provided on the wet catalytic oxidation reactor (2); The ceramic membrane filter (1) is also connected to the cleaning liquid pipeline (8); the wet catalytic oxidation reactor (2) includes an outer shell (201) and multiple internal catalytic oxidation tubes (203). The catalytic oxidation tubes (203) are vertically fixed by a support plate (205). Catalytic membranes (213) and catalytic membrane partitions (214) are alternately arranged inside the tubes. The bottom and top of the catalytic oxidation tubes (203) are supported by catalyst support grids (212); the top and bottom of adjacent catalytic oxidation tubes (203) are connected by elbows ( 204) The bottom is provided with a formaldehyde wastewater inlet (202) and the top is provided with a formaldehyde wastewater outlet (206); the shell side of the wet catalytic oxidation reactor (2) is provided with a heating medium inlet (210) and a heating medium outlet (209), and a drain outlet (207) is provided at the same time; a temperature sensor is installed on the shell (201) corresponding to the heating medium space through a temperature sensor interface (208), and a pressure sensor is installed on the pipeline of the top formaldehyde wastewater outlet (206) through a pressure sensor interface (211).

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