A method for treating organic wastewater using a graphene aerogel microchannel reactor

Abstract

The invention discloses a method for treating organic wastewater by using a graphene aerogel microchannel reactor, comprising a microchannel reactor module including a microchannel reaction tube and a light introduction device; each microchannel reactor module is provided with a plurality of microchannel reaction tubes, the microchannel reaction tubes are cylindrical tubular structures, the light introduction device includes a light collecting part, a light transmitting part, and a scattering illuminator, the light collecting part includes a light collector, a Fresnel lens is provided on the light collector, the optical fiber aggregates sunlight through the Fresnel lens and transmits light to the scattering illuminator, and the scattering illuminator is arranged in the light introduction cavity. The method for treating organic wastewater by using a microchannel reactor of the invention has the characteristics of small footprint, large treatment capacity, quick effect, low energy consumption, easy maintenance, etc. The invention utilizes the photocatalytic technology in the chemical conversion method to rapidly oxidize and completely degrade organic pollutants in water. The charge generated by light energy driving can be transferred to the surface of the photocatalytic material and mineralize the macromolecular organic matter near the active center into harmless substances.

Description

Technical Field

[0001] The invention relates to the field of organic wastewater treatment, and in particular to a method for treating organic wastewater using a graphene aerogel microchannel reactor. Background Art

[0002] With the rapid development of modern industrialization, organic wastewater composed of industrial dyes and cleaning wastewater generated by the chemical, pharmaceutical and other industries has greatly aggravated the pollution of global water resources and soil. The negative impact on the ecosystem and the potential harm to public health make it urgent to solve this problem. At present, the methods for purifying organic wastewater generated by industry are mainly divided into adsorption removal, chemical conversion and biodegradation.

[0003] The method of treating organic wastewater by adsorption removal, for example, in the prior art, the application number is: CN201510954497.5 discloses a method for treating high-concentration organic wastewater, which specifically includes the following steps: 1. Preparation of modified zeolite: After roasting magnesium oxide solid for a certain period of time, cooling, and microwave loading with zeolite in a certain ratio, after cooling, the modified zeolite loaded with magnesium oxide is obtained. 2. Treatment of organic wastewater: Adding modified zeolite in a certain ratio to organic wastewater, after a certain reaction time, a good adsorption and removal effect of ammonia nitrogen, phosphorus, etc. in the organic wastewater can be achieved.

[0004] Another example is the method of using biodegradation to treat organic wastewater. For example, application number: CN201310190619.9 discloses a method for biodegrading organic wastewater using microorganisms, which is characterized in that the method includes the following processes: 1) using dry reeds as fillers and biological carriers, 2) using a biological fluidized bed or fixed bed to treat the organic wastewater; the dry reeds are reeds picked after maturity, the reeds are hollow columns, cut into lengths of 1cm-3cm according to specifications; soaked in clean water; the biological fluidized bed or fixed bed The method comprises the following steps: 1) placing soaked reeds in a fluidized bed or fixed bed reactor as biological fillers; 2) introducing organic wastewater with a pH value of 6-9, aerating the same, with a gas-water weight ratio of 4-20:1, and forming biofilms by continuous water inlet, with the bioload on the fillers reaching 9-45 g / L, which is considered successful; 3) the organic wastewater is added with a filler filling rate of 20-50% for the fluidized bed and 100% for the fixed bed, and aeration biochemical treatment is performed, with a COD volumetric load of 0.6-2.7 kgCOD / (m 3 d), hydraulic retention time is 1-6h;

[0005] However, neither physical nor biological methods can completely remove toxic pollutants in organic wastewater, and require high investment and operating costs. In view of the above, it is necessary to propose a method for treating organic wastewater using a graphene aerogel microchannel reactor to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to solve the above technical problems and to provide a method for treating organic wastewater using a graphene aerogel microchannel reactor.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme: a method for treating organic wastewater by a graphene aerogel microchannel reactor, comprising the following steps:

[0008] Step 1: adding sulfuric acid solution to the wastewater in the first Fenton reaction tank, adjusting the pH to 2-4, and adding ferrous sulfate to the first Fenton reaction tank;

[0009] Step 2: The effluent from the first Fenton reaction tank flows by gravity to the second Fenton reaction tank, and hydrogen peroxide is added to the second Fenton reaction tank to form ·OH free radicals to oxidize organic matter in the wastewater; the effluent from the second Fenton reaction tank flows by gravity to the degassing tank, and the aeration pipeline is connected to the first Fenton reaction tank, the second Fenton reaction tank, and the degassing tank;

[0010] Step 3: The effluent from the degassing tank flows by gravity to the pH adjustment tank, and the sodium hydroxide dosing device is connected to the pH adjustment tank to adjust the pH to 6-8; the effluent from the pH adjustment tank flows by gravity to the coagulation reaction tank, and the PAC (polyaluminium chloride) dosing device is connected to the coagulation reaction tank; the effluent from the coagulation reaction tank flows by gravity to the flocculation reaction tank, and the PAM (polyacrylamide) dosing device is connected to the flocculation reaction tank;

[0011] Step 4: the effluent from the flocculation reaction tank flows by gravity to the inclined tube sedimentation tank; the supernatant effluent from the inclined tube sedimentation tank flows by gravity to the microchannel reactor treatment tank; a plurality of microchannel reactor modules are arranged in the microchannel reactor treatment tank, and the sewage flows through the microchannel reactor modules to photocatalytically degrade the organic sewage;

[0012] The microchannel reactor module comprises a microchannel reaction tube and a light introduction device; each of the microchannel reactor modules is arranged in a matrix and has a plurality of microchannel reaction tubes arranged in parallel, the microchannel reaction tube is a cylindrical tubular structure, and its lower end is a closed mouth, the microchannel reactor tube of the cylindrical tubular structure comprises an outer tube and an inner tube arranged coaxially, at least the inner tube is made of a transparent material, an annular closed ring cavity is formed between the outer tube and the inner tube, a light introduction cavity is formed inside the inner tube, an aerogel porous material modified with graphene is arranged in the closed ring cavity, and the aerogel porous material is modified with PDA / TiO2 / AgCl / Ag to form a photocatalytic material; the closed ring cavity is filled with photocatalytic material, the outer wall of the lower end of the outer tube is provided with a water inlet hole connected to the closed ring cavity, and the upper end of the microchannel reaction tube is provided with a water outlet hole; the water outlet holes of several microchannel reaction tubes converge into the middle water pool;

[0013] Step 5: The intermediate water pool is connected to the quartz sand filter through the intermediate water pump; the water outlet from the filter is connected to the outlet pipe to form a standard discharge.

[0014] Furthermore, the light introduction device includes a light collecting part, a light transmission part, and a scattering illuminator. The light collecting part includes a light collector, on which a Fresnel lens is provided. The light collector adopts a dual-axis structure to track and converge sunlight. The light transmission part adopts an optical fiber, one end of which is connected to the light collector, and the other end is connected to the scattering illuminator. The optical fiber aggregates sunlight through the Fresnel lens and transmits the light to the scattering illuminator. The scattering illuminator is arranged in the light introduction cavity.

[0015] Furthermore, the graphene-modified aerogel porous material is prepared by an acid-base two-step sol-gel method;

[0016] In the first step, EtOH (ethanol), TEOS (ethyl silicate) and an appropriate amount of hydrochloric acid in a volume ratio of 30:1 were mixed to form a precursor solution (so that the pH value of the mixed solution was 3-4), and then stirred at room temperature for 90 minutes; in the second step, graphene oxide powder was dissolved in ethanol; then the dispersed GO sheets were ultrasonically peeled for 1 hour to obtain a GO aqueous dispersion; different masses of GO solution were added to the precursor solution to obtain GO-doped sol;

[0017] After magnetic stirring for 12 h, 1 mol / L ammonia water was added to the pure SiO2 sol and GO / SiO2 sol until the pH value reached 6-7 while being fully hydrolyzed and evenly dispersed. The sol was poured into a mold and aged at room temperature. The wet gel was placed in an ethanol bath at room temperature to remove any residual impurities or moisture. GO / SiO2 aerogel was obtained by supercritical CO2 drying.

[0018] Furthermore, the photocatalytic material is prepared in the following manner:

[0019] Modification of aerogel porous materials by polydopamine (PDA)

[0020] The aerogel porous material was ultrasonically washed in anhydrous ethanol; the washed aerogel porous material was immersed in an aqueous solution of dopamine hydrochloride, and then an aqueous solution of tris(hydroxymethyl)aminomethane was added to the reaction system to make the pH of the aqueous solution equal to 8.5, and stirred for 24 hours; finally, the obtained modified material was rinsed with other substances on the surface under deionized water, and dried at 60°C, which was recorded as aerogel / PDA;

[0021] Preparation of TiO2 modified aerogel porous materials

[0022] Ammonium fluorotitanate and boric acid were dissolved in deionized water with a mass ratio of ammonium fluorotitanate: boric acid: deionized water = 1:1:100; then, the aerogel / PDA was immersed in the mixed solution and continuously oscillated for 4 hours at 40°C; finally, the prepared TiO2-modified aerogel porous material was washed with deionized water for several times and dried at 80°C for subsequent experiments, which was recorded as aerogel / PDA / TiO2;

[0023] Preparation of TiO2 / AgCl / Ag modified aerogel porous materials

[0024] In order to prepare the PDA / TiO2 / AgCl / Ag modified aerogel porous material, the prepared aerogel / PDA / TiO2 aerogel porous material was soaked in a 0.9wt% silver nitrate aqueous solution for 30min, and then zinc chloride was added to the solution, the mass ratio of zinc chloride to silver nitrate was 0.3-0.4:1, and gently stirred for 30min. Then, the sample was reduced with a xenon lamp for 30min to form Ag / AgCl in situ on the surface of aerogel / PDA / TiO2: the prepared PDA / TiO2 / AgCl / Ag modified aerogel porous material was rinsed with deionized water and dried overnight in a vacuum, which was recorded as aerogel / PDA / TiO2 / AgCl / Ag.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: the method for treating organic wastewater using a graphene aerogel microchannel reactor of the present invention has the characteristics of small footprint, large treatment capacity, quick effect, low energy consumption, and easy maintenance. The present invention utilizes the photocatalytic technology in the chemical conversion method to quickly oxidize and completely degrade organic pollutants in water. After the photocatalyst absorbs ultraviolet light, the charge generated by light energy can be transferred to the surface of the photocatalytic material and mineralize the macromolecular organic matter near the active center into harmless substances, or they can recombine and dissipate energy. The present invention combines a microreactor with a high specific surface area and a small characteristic length with a photocatalyst. The photocatalytic microreactor thus developed not only has a large specific surface area, fully optimizes the distribution of light inside the microreactor, but also strengthens the mass transfer between phases. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a process for treating organic wastewater using a graphene aerogel microchannel reactor according to the present invention;

[0027] Figure 2 It is a structural schematic diagram of the microchannel reaction tube in the present invention;

[0028] Figure 3 The morphology of graphene-modified aerogel porous material observed by scanning electron microscope;

[0029] Figure 4This is a scanning electron microscope observation of the surface of the aerogel porous material skeleton coated with polydopamine;

[0030] In the figure: 1. the first Fenton reaction tank; 2. sulfuric acid solution; 3. ferrous sulfate; 4. the second Fenton reaction tank; 5. hydrogen peroxide; 6. degassing tank; 7. aeration pipeline; 8. pH adjustment tank; 9. sodium hydroxide dosing device; 10. coagulation reaction tank; 11. polyaluminium chloride dosing device; 12. flocculation reaction tank; 13. polyacrylamide dosing device; 14. inclined tube sedimentation tank; 15. microchannel reactor treatment tank; 16. microchannel reactor module; 17. microchannel reaction tube; 18. light introduction device; 19. closed mouth; 20. outer tube; 21. inner tube; 22. closed ring cavity; 23. light introduction cavity; 24. aerogel porous material; 25. water inlet hole; 26. water outlet hole; 27. intermediate water tank; 28. quartz sand filter; 29. ​​light collecting part; 30. light transmission part; 31. scattering illuminator; 32. light collector; 33. Fresnel lens. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0032] A method for treating organic wastewater using a graphene aerogel microchannel reactor comprises the following steps:

[0033] Step 1: Add sulfuric acid solution 2 to the wastewater in the first Fenton reaction tank 1, adjust the pH to 2-4, and add ferrous sulfate 3 to the first Fenton reaction tank 1; ferrous sulfate 3 has oxidation, precipitation and deodorization effects, and can remove organic matter, heavy metal ions and odorous substances in sewage and improve water quality. Ferrous sulfate 3 has certain oxidizing properties and can oxidize certain organic substances into harmless compounds. This oxidation can effectively remove pollutants such as organic matter and dyes in sewage and purify water quality. At the same time, the oxidation of ferrous sulfate 3 can also degrade toxic and harmful substances and improve the biodegradability of water bodies.

[0034] Ferrous sulfate 3 can react with odorous substances such as hydrogen sulfide in sewage to generate non-volatile sulfides, thereby reducing the odor of sewage. This deodorization effect can improve the working environment of sewage treatment plants and reduce odor pollution during sewage treatment.

[0035] like Figure 1 As shown, ferrous sulfate 3 is added to sewage in the form of a solution for treatment. The dosage is 10-50 ml per cubic meter of water.

[0036] Step 2: The effluent from the first Fenton reaction tank 1 flows by gravity to the second Fenton reaction tank 4, and the effluent from the second Fenton reaction tank 4 flows by gravity to the degassing tank 6. Hydrogen peroxide 5 is added to the second Fenton reaction tank 4, and the dosage of hydrogen peroxide 5 is 1-10% to form OH free radicals to oxidize organic matter in the wastewater; hydrogen peroxide 5 mainly plays the role of removing organic pollutants in wastewater treatment, especially removing COD (chemical oxygen demand) in water. Hydrogen peroxide 5 has strong oxidizing properties and can decompose organic matter in water by oxidation, converting it into carbon dioxide and water, thereby reducing the COD content of organic matter in the water. Figure 1 As shown, in order to make the first Fenton reaction tank 1 and the second Fenton reaction tank 4 react evenly, air can be forced into the sewage to make the sewage in the tank contact with the air for oxygenation, stir the liquid, accelerate the transfer of oxygen in the air to the liquid, prevent the suspended objects in the tank from sinking, strengthen the contact between the organic matter in the tank and the microorganisms and dissolved oxygen, and oxidize and decompose the organic matter in the sewage.

[0037] Step 3: The effluent from the degassing tank 6 flows by gravity to the pH adjustment tank 8, and the sodium hydroxide dosing device 9 is connected to the pH adjustment tank 8 to adjust the pH to 6-8; the effluent from the pH adjustment tank 8 flows by gravity to the coagulation reaction tank 10, and the PAC (polyaluminium chloride) dosing device is connected to the coagulation reaction tank 10. PAC is mainly composed of aluminium hydroxide, aluminium chloride and aluminium oxide. It has the characteristics of good coagulation effect, small dosage and convenient use. The working principle of polyaluminium chloride in sewage treatment is mainly to destabilize suspended matter, organic matter, heavy metal ions and other substances in the water through the effects of electrical neutralization, adsorption bridging and net capture and sweeping, so as to condense into large particles, thereby settling or floating and separating. Specifically, polyaluminium chloride decomposes in water to produce cations with high charge density, which can quickly react with colloidal particles or organic matter in water to neutralize them, making these substances lose stability.

[0038] The effluent from the coagulation reaction tank 10 flows by gravity to the flocculation reaction tank 12. The PAM (polyacrylamide) dosing device is connected to the flocculation reaction tank 12. The dosage of polyacrylamide is controlled to be 0.01~10g / m 3 ; Polyacrylamide is because its molecular chain contains some functional groups, and the solid particles suspended in the water can be filled or adsorbed by the intermolecular charges. Therefore, polyacrylamide can accelerate the sedimentation of suspended particles, significantly accelerate the clarification of the solution, and promote filtration.

[0039] Step 4: The effluent from the flocculation reaction tank 12 flows by gravity to the inclined tube sedimentation tank 14; the supernatant effluent from the inclined tube sedimentation tank 14 flows by gravity to the microchannel reactor treatment tank 15; Figure 1 As shown, the sludge at the bottom of the inclined tube sedimentation tank 14 is connected to the filter press through a sludge pump; the effluent from the filter press is connected to the wastewater regulating tank, the filter press filters and separates the precipitated sludge from the water, and the separated wastewater is then sent to the wastewater regulating tank.

[0040] A number of microchannel reactor modules 16 are provided in the microchannel reactor treatment tank 15, and the sewage flows through the microchannel reactor modules 16 to photocatalytically degrade the organic sewage; after passing through the aforementioned Fenton reaction tank, coagulation reaction tank 10, and flocculation reaction tank 12, most of the organic matter in the wastewater is separated and purified, and the clarity and fluidity of the wastewater after flocculation and sedimentation are improved; however, the wastewater still contains some untreated organic matter. The microchannel reactor module 16 is arranged in this embodiment to improve the long-term operation stability of the system and to improve the performance of photocatalytic degradation of organic wastewater at a higher wastewater flow rate.

[0041] The microchannel reactor module 16 includes a microchannel reaction tube 17 and a light introduction device 18. Figure 1 As shown, the number of microchannel reactor modules 16 can be increased or decreased in the microchannel reactor treatment tank 15 according to the required treatment amount, so the device has flexible assembly, and the number of modules can be increased or decreased according to the amount of wastewater to be treated, and the modules are arranged in parallel; specifically, each of the microchannel reactor modules 16 is arranged in a matrix and has a plurality of microchannel reaction tubes 17 arranged in parallel, such as Figure 2 Shown is a schematic diagram of a microchannel reactor module 16, Figure 2 Only two adjacent microchannel reaction tubes 17 are shown schematically. The microchannel reaction tube 17 is a cylindrical tubular structure with a closed opening 19 at the lower end. In actual use, the lower part of the module is completely immersed in the microchannel reactor treatment tank 15, and the closed opening 19 at the lower end blocks the wastewater from entering the light introduction cavity 23. The microchannel reactor tube with a cylindrical tubular structure includes a coaxially arranged outer tube 20 and an inner tube 21, and an annular closed ring cavity 22 is formed between the outer tube 20 and the inner tube 21. The inner tube 21 forms a light introduction cavity 23. The closed ring cavity 22 is provided with an aerogel porous material 24 modified with graphene, and the aerogel porous material 24 is modified with PDA / TiO2 / AgCl / Ag to form a photocatalytic material; the photocatalytic material is filled in the closed ring cavity 22 until The inner tube 21 is made of transparent material. In actual use, the upper mouth of the microchannel reaction tube 17 can be made of light-transmitting material, so that natural light can be irradiated into the light introduction cavity 23. In actual use, it is not easy to directly irradiate sunlight into the light introduction cavity 23 under natural conditions, and the irradiation time is short. In order to solve this problem, an artificial light source or a natural light source can be introduced into the light introduction cavity 23 by using a light introduction device 18. The interior of the light introduction cavity 23 is connected to the outside atmosphere. The outer wall of the lower end of the outer tube 20 is provided with a water inlet hole 25 connected to the closed ring cavity 22, and the upper end of the microchannel reaction tube 17 is provided with a water outlet hole 26; therefore, the water inlet hole 25 can press the wastewater into the water inlet hole 25 by using the pressure generated by the liquid level height of the wastewater in the microchannel reactor treatment tank 15, such as Figure 2As shown, the upper ends of the microchannel reaction tubes 17 are connected in parallel, and negative pressure is generated in the main pipe. In actual use, a water pump can be used to generate negative pressure to provide a driving force for liquid flow in the microchannel reaction tubes 17, so that wastewater is sucked in from the water inlet 25 and catalytically degraded by the photocatalytic material on organic matter, and finally flows out through the water outlet 26. The water outlets 26 of several microchannel reaction tubes 17 converge into the middle water pool 27; as another embodiment, the negative pressure can also be formed by a vacuum pump, and the wastewater flows through the microchannel reaction tubes 17 in the same way.

[0042] Specifically, in this step, if Figure 1 , 2 As shown, the light introduction device 18 includes a light collecting part 29, a light transmission part 30, and a scattering illuminator 31. The light collecting part includes a light collector 32, on which a Fresnel lens 33 is provided. The light collector 32 uses a dual-axis structure to track and converge sunlight. The light transmission part 30 uses an optical fiber, one end of which is connected to the light collector 32, and the other end is connected to the scattering illuminator 31. The optical fiber aggregates sunlight through the Fresnel lens 33 and transmits the light to the scattering illuminator 31. The scattering illuminator 31 is arranged in the light introduction cavity 23. The light collector 32 uses a dual-axis structure to drive the head to form a swinging motion, and always makes the Fresnel lens 33 face the sunlight, so as to collect the light as much as possible, so that the light converges to the optical fiber end in the light collector 32, and the light is respectively introduced into each microchannel reaction tube 17 by using the optical fiber, so at least the inner tube 21 is made of transparent material, so that the photocatalytic material can be irradiated by light.

[0043] In this step, the graphene-modified aerogel porous material 24 is prepared by an acid-base two-step sol-gel method; silica aerogel is an amorphous solid material with a porous three-dimensional network structure, and has excellent physical properties, such as large specific surface area, low density, high porosity and low thermal conductivity. The fragility of the aerogel framework originates from the fragility of the inter-particle connection region, which is formed by the condensation and reprecipitation of silica particles during gelation and aging; in order to improve the mechanical properties of the aerogel and avoid network shrinkage; it is modified by graphene oxide.

[0044] Graphene oxide (GO) is an ideal nanofiller due to its unique two-dimensional structure and excellent properties.

[0045] Compared with graphene, GO contains a large number of oxygen-containing groups on its surface, which is easy to disperse evenly in common solvents. In addition, the thermal conductivity of GO is relatively low and will not adversely affect the thermal conductivity of silica aerogel. Adding GO can reduce the shrinkage of silica wet gel and enhance the mechanical strength. There is good compatibility between the two elements.

[0046] Specifically: In the first step, EtOH (ethanol), TEOS (ethyl silicate) and an appropriate amount of hydrochloric acid in a volume ratio of 30:1 are mixed to form a precursor solution, and the pH value of the mixed solution is 3-4, and then stirred at room temperature for 90 minutes; in the second step, a certain amount of graphene oxide powder, with a mass fraction of GO of 1%, is dissolved in ethanol; then the dispersed GO sheets are ultrasonically peeled for 1 hour to obtain a GO aqueous dispersion; different masses of GO solution are added to the precursor solution to obtain a doped sol with a GO content ranging from a mass fraction of 1%.

[0047] After magnetic stirring for 12 hours, 1 mol / L ammonia water was added to the pure SiO2 sol and GO / SiO2 sol until the pH value reached 6-7 while being fully hydrolyzed and evenly dispersed. To avoid precipitation of GO powder, the amount of ammonia was controlled to keep the gel time within 10 minutes. The sol was poured into a mold and, after aging at room temperature, the wet gel was placed in an ethanol bath at room temperature to remove residual impurities or moisture. Finally, GO / SiO2 aerogel was obtained by supercritical CO2 drying. Specifically, when the volume ratio of EtOH / TEOS in the precursor solution was 30:1, the GO mass fractions of the prepared aerogels were 1%.

[0048] Furthermore, the photocatalytic material is prepared in the following manner:

[0049] Modification of aerogel porous materials 24 by polydopamine (PDA)

[0050] The morphology of the graphene-modified aerogel porous material 24 was observed by scanning electron microscopy. Figure 3 As shown, it can be found that the surface of its skeleton is relatively smooth. The porous material is improved by polydopamine. PDA can be used as an adhesive coating to make the surface of the porous material rough, which is convenient for the subsequent coating of the material when the aerogel surface is modified. The adhesion and reducing properties of PDA can be used to firmly load the photocatalytic material onto the porous material carrier.

[0051] The aerogel porous material 24 was ultrasonically treated in anhydrous ethanol for 20 minutes, and then the sponge was washed with deionized water for multiple times for subsequent surface modification; the washed aerogel porous material 24 was immersed in 8L of dopamine hydrochloride aqueous solution (2.0 mg / mL), and then 2L of tris(hydroxymethyl)aminomethane aqueous solution (3.0 mg / mL) was added to the reaction system to make the pH of the aqueous solution = 8.5, and stirred for 24 hours; finally, the obtained modified material was rinsed with other substances on the surface under deionized water, and dried at 60°C, which was recorded as aerogel / PDA; Figure 4 As shown, the surface of the porous skeleton was coated with polydopamine, and it can be easily observed that the surface of the porous skeleton became rough, indicating that the polydopamine film was successfully formed on the surface of the skeleton.

[0052] The surface plasmon resonance (SPR) effect of Ag enables them to fully absorb visible light and ultraviolet light in sunlight. However, when Ag / AgCl is used alone as a catalyst, its adsorption capacity is poor. Ag / AgCl can promote the transfer of photogenerated carriers with the assistance of TiO2, which enables it to maintain its stability and photocatalytic properties. This greatly promotes the separation of electron holes in semiconductors and provides more electrons for photocatalytic reactions.

[0053] The photocatalytic microreactor exhibits a relatively high surface area to volume ratio due to its small reaction channel, reduces the molecular transmission distance, and enhances mass transfer, thereby having a better effect in purifying organic wastewater. The reaction rate of the microreactor in this embodiment is more than 100 times faster than that of an ordinary large reactor. The microchannel reaction tube 17 in this embodiment has the advantages of large surface area, simple manufacturing process, and good mass transfer effect.

[0054] Specifically, after the porous material is modified by using PDA, TiO2, AgCl, and Ag are coated on the porous material to form a porous material coated with a photocatalyst.

[0055] Preparation of TiO2 modified aerogel porous material 24

[0056] Ammonium fluorotitanate and boric acid were dissolved in deionized water, and the mass ratio of ammonium fluorotitanate: boric acid: deionized water was 1:1:100. Specifically, 100 g of ammonium fluorotitanate and 100 g of boric acid were dissolved in 10 L of deionized water. Then, the aerogel / PDA was immersed in the mixed solution and continuously oscillated at 40°C for 4 hours. Finally, the prepared TiO2-modified aerogel porous material 24 was washed with deionized water for several times and dried at 80°C for subsequent experiments, which was recorded as aerogel / PDA / TiO2.

[0057] Preparation of TiO2 / AgCl / Ag modified aerogel porous material 24

[0058] In order to prepare the PDA / TiO2 / AgCl / Ag modified aerogel porous material 24, the prepared aerogel / PDA / TiO2 aerogel porous material 24 was soaked in a 0.9wt% silver nitrate aqueous solution for 30 minutes, and then zinc chloride was added to the solution, the mass ratio of zinc chloride to silver nitrate was 0.3-0.4:1, and gently stirred for 30 minutes. Then, the sample was reduced with a xenon lamp for 30 minutes to form Ag / AgCl in situ on the surface of aerogel / PDA / TiO2: the prepared PDA / TiO2 / AgCl / Ag modified aerogel porous material 24 was rinsed with deionized water and dried overnight in a vacuum, and recorded as aerogel / PDA / TiO2 / AgCl / Ag.

[0059] The microchannel reaction tube 17 can be made of inorganic transparent materials such as silicate glass, or organic transparent materials such as acrylic, PET, PP, PVC, etc., which can transmit light well. The overall structure is as follows: Figure 2 As shown, a cylindrical structure made of transparent material introduces a light source into the internal light introduction cavity 23, and an aerogel porous material 24 coated with a photocatalyst is arranged in the closed ring cavity 22, so that a microchannel is formed in the closed ring cavity 22. Wastewater passes through the aerogel porous material 24 coated with a photocatalyst, and under the irradiation of the light source, the wastewater flows evenly through the photocatalyst, so that the organic matter in the wastewater is degraded.

[0060] According to the test, the wastewater treatment capacity of a single microchannel reaction tube 17 in this embodiment can reach 312.5L / h•m2 at a high flow rate. The reaction tube can be used stably for a long time and is easy to assemble. The modular design can flexibly increase or decrease the modules according to the required processing flow.

[0061] The last one, such as Figure 1 As shown, step five: the intermediate water pool 27 is connected to the quartz sand filter 28 through the intermediate water pump; the filter outlet water is connected to the outlet pipe to form a standard discharge.

[0062] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for treating organic wastewater using a graphene aerogel microchannel reactor, characterized in that: include: The supernatant effluent from the inclined tube sedimentation tank flows by gravity to the microchannel reactor treatment tank; a number of microchannel reactor modules are arranged in the microchannel reactor treatment tank, and the sewage flows through the microchannel reactor modules to photocatalytically degrade the organic sewage; The microchannel reactor module comprises a microchannel reaction tube and a light introduction device; each of the microchannel reactor modules is arranged in a matrix and has a plurality of microchannel reaction tubes arranged in parallel, wherein the microchannel reaction tube is a cylindrical tubular structure with a closed opening at the lower end, and the microchannel reactor tube of the cylindrical tubular structure comprises an outer tube and an inner tube arranged coaxially, at least the inner tube is made of a transparent material, an annular closed ring cavity is formed between the outer tube and the inner tube, a light introduction cavity is formed inside the inner tube, and an aerogel porous material modified with graphene is arranged in the closed ring cavity, and the aerogel porous material is treated with PDA / TiO2 / AgCl / Ag modification forms photocatalytic material; the closed ring cavity is filled with photocatalytic material, the outer wall of the lower end of the outer tube is provided with a water inlet hole connected to the closed ring cavity, and the upper end of the microchannel reaction tube is provided with a water outlet hole, the light introduction device includes a light collecting part, a light transmission part, and a scattering illuminator, the light collecting part includes a light collector, a Fresnel lens is provided on the light collector, the light collector adopts a dual-axis structure to track and converge sunlight, the light transmission part adopts an optical fiber, one end of the optical fiber is connected to the light collector, and the other end is connected to the scattering illuminator, the optical fiber aggregates sunlight through the Fresnel lens and transmits light to the scattering illuminator, and the scattering illuminator is arranged in the light introduction cavity.

2. The method for treating organic wastewater using a graphene aerogel microchannel reactor according to claim 1, characterized in that: The graphene-modified aerogel porous material is prepared by an acid-base two-step sol-gel method; In the first step, EtOH, TEOS and an appropriate amount of hydrochloric acid in a volume ratio of 30:1 are mixed to form a precursor solution, the pH value of the mixed solution is 3-4, and then stirred at room temperature for 90 minutes; in the second step, graphene oxide powder is dissolved in ethanol; then the dispersed GO sheets are ultrasonically peeled for 1 hour to obtain a GO aqueous dispersion; GO solution is added to the precursor solution to obtain a GO-doped sol; After magnetic stirring for 12 h, 1 mol / L ammonia water was added to the pure SiO2 sol and GO / SiO2 sol until the pH value reached 6-7 while being fully hydrolyzed and evenly dispersed. The sol was poured into a mold and aged at room temperature. The wet gel was placed in an ethanol bath at room temperature to remove any residual impurities or moisture. GO / SiO2 aerogel was obtained by supercritical CO2 drying.

3. A method for treating organic wastewater using a graphene aerogel microchannel reactor according to claim 1 or 2, characterized in that: The photocatalytic material is prepared in the following manner: Modification of aerogel porous materials by polydopamine PDA: The aerogel porous material was ultrasonically washed in anhydrous ethanol; the washed aerogel porous material was immersed in an aqueous solution of dopamine hydrochloride, and then an aqueous solution of tris(hydroxymethyl)aminomethane was added to the reaction system to make the pH of the aqueous solution equal to 8.5, and stirred for 24 hours; finally, the obtained modified material was rinsed with other substances on the surface under deionized water, and dried at 60°C, which was recorded as aerogel / PDA; Preparation of TiO2 modified aerogel porous materials: Ammonium fluorotitanate and boric acid were dissolved in deionized water with a mass ratio of ammonium fluorotitanate: boric acid: deionized water = 1:1:100; then the aerogel / PDA was immersed in the mixed solution and continuously oscillated at 40°C for 4 hours; finally, the prepared TiO2-modified aerogel porous material was washed with deionized water for several times and dried at 80°C for subsequent experiments, which was recorded as aerogel / PDA / TiO2; Preparation of TiO2 / AgCl / Ag modified aerogel porous materials: In order to prepare PDA / TiO2 / AgCl / Ag modified aerogel porous material, the prepared aerogel / PDA / TiO2 aerogel porous material was soaked in a 0.9wt% silver nitrate aqueous solution for 30min, and then zinc chloride was added to the solution, the mass ratio of zinc chloride to silver nitrate was 0.3-0.4:1, and gently stirred for 30min. Then, the sample was reduced with a xenon lamp for 30min to in situ form Ag / AgCl on the surface of aerogel / PDA / TiO2: the prepared PDA / TiO2 / AgCl / Ag modified aerogel porous material was rinsed with deionized water and dried in vacuum overnight, and recorded as aerogel / PDA / TiO2 / AgCl / Ag.

4. A method for treating organic wastewater using a graphene aerogel microchannel reactor according to any one of claims 1 to 3, characterized in that: Before the step of allowing the supernatant to flow to the microchannel reactor treatment tank by gravity, the following steps are also included: Step 1: adding sulfuric acid solution to the wastewater in the first Fenton reaction tank, adjusting the pH to 2-4, and adding ferrous sulfate to the first Fenton reaction tank; Step 2: The effluent from the first Fenton reaction tank flows by gravity to the second Fenton reaction tank, and hydrogen peroxide is added to the second Fenton reaction tank to form ·OH free radicals to oxidize organic matter in the wastewater; the effluent from the second Fenton reaction tank flows by gravity to the degassing tank, and the aeration pipeline is connected to the first Fenton reaction tank, the second Fenton reaction tank, and the degassing tank; Step 3: The effluent from the degassing tank flows by gravity to the pH adjustment tank, and the sodium hydroxide dosing device is connected to the pH adjustment tank to adjust the pH to 6-8; the effluent from the pH adjustment tank flows by gravity to the coagulation reaction tank, and the PAC dosing device is connected to the coagulation reaction tank; the effluent from the coagulation reaction tank flows by gravity to the flocculation reaction tank, and the PAM dosing device is connected to the flocculation reaction tank; Step 4: The effluent from the flocculation reaction tank flows by gravity to the inclined tube sedimentation tank; the supernatant effluent from the inclined tube sedimentation tank flows by gravity to the microchannel reactor treatment tank, and the effluent holes of several microchannel reaction tubes converge into the intermediate water tank; After entering the microchannel reactor treatment tank for treatment, it also includes: Step 5: The intermediate water pool is connected to the quartz sand filter through the intermediate water pump; the water outlet from the filter is connected to the outlet pipe to form a standard discharge.

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