A circulating wastewater treatment system based on ozone oxidation

Abstract

This invention discloses a circulating wastewater treatment system based on ozone oxidation, comprising a pressurized dissolved gas tank and a reaction tank. The pressurized dissolved gas tank has multiple sets of liquid spray nozzles at the top and multiple sets of gas spray nozzles at the bottom. Wastewater enters the pressurized dissolved gas tank through the liquid spray nozzles at the top. Ozone enters the pressurized dissolved gas tank through the gas spray nozzles at the bottom after being pressurized by an ozone pressurization system. The pressurized wastewater and pressurized ozone form a convection system within the pressurized dissolved gas tank. The pressurized dissolved gas tank has a contact zone to promote the contact between ozone and wastewater, where the convection gas and water come into contact to form dissolved gas water. The reaction tank has a catalyst release port and multiple dissolved gas water release ports at the bottom, arranged in a ring around the catalyst release port. Dissolved gas water enters the reaction tank through the dissolved gas water release ports, and catalyst particles enter the reaction tank through the catalyst release ports.

Description

Technical Field

[0001] This invention relates to a circulating wastewater treatment system based on ozone oxidation. Background Technology

[0002] Ozone oxidation, as an advanced oxidation technology, has been widely used in water treatment. Ozone possesses strong oxidizing properties; its oxidation potential (2.07 mV) in acidic environments is second only to fluorine (3.06 mV). It primarily removes organic matter through the direct oxidation and decomposition of ozone molecules to generate reactive oxygen species (ROS). However, direct ozone oxidation is selective, and its effect on the oxidative degradation of certain pollutants is not significant. ROS includes various forms such as hydroxyl radicals, singlet oxygen, and superoxide anion radicals, all of which have oxidation potentials exceeding those of ozone molecules, especially hydroxyl radicals, whose oxidation potential can reach 2.80 mV. However, ROS have very short half-lives, and the efficiency of generating ROS from ozone molecules alone is low, requiring highly active catalysts for rapid and stable generation. Therefore, catalytic oxidation technology that generates ROS from ozone has become a current research hotspot.

[0003] Ozone catalysis is mainly achieved through homogeneous and heterogeneous catalysis. Homogeneous catalysis uses soluble metal ions or oxidants as catalysts for the ozone reaction, commonly using Mn. 2+ Fe 2+ Co 2+ Cr 3+ Transition metal ions and oxidants such as H₂O₂ promote ROS generation. Heterogeneous catalysis uses solid catalysts where ozone is adsorbed onto the catalyst surface to generate ROS. ROS is then used to oxidize organic matter also adsorbed on the catalyst surface, or to oxidize organic matter in the surrounding aquatic environment through diffusion. Therefore, heterogeneous catalysis relies on characteristic functional groups or acidic sites on the catalyst surface; these catalytically active sites are the main adsorption or reaction centers. Consequently, related research focuses on supported catalysts to improve the dispersion and stability of catalytically active sites. However, this is still limited by the catalyst's specific surface area and pore size, affecting the mass transfer between ozone molecules and the solid catalyst, thus impacting catalytic oxidation efficiency. In homogeneous catalysis, the catalyst, existing in ionic form, can mix thoroughly with ozone molecules, and the effects of contact area and mass transfer can be ignored to some extent. However, complex separation techniques are required to mitigate secondary pollution of the system by certain catalytic ions.

[0004] Besides the properties and morphology of the catalyst affecting ozone catalytic efficiency, the solubility of ozone molecules also influences the degree of contact between liquid ozone molecules and the catalyst. Currently, ozone catalytic oxidation is mainly achieved through aeration, where ozone gas is introduced into the reaction tank via a blower. As the bubbles rise, they react with the catalyst and water pollutants at the bottom, thus removing pollutants. However, due to the low solubility and slow mass transfer rate of ozone in water, ozone utilization is low. Therefore, to achieve the treatment target, excessive ozone is often required, increasing operating costs and causing environmental impacts due to excessive ozone release. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a circulating wastewater treatment system based on ozone oxidation. This system improves the solubility of ozone molecules in water by increasing the gas-liquid contact and enhances the mass transfer between ozone molecules and solid catalysts by forming micro-nano bubbles, thereby improving catalytic oxidation efficiency and significantly increasing the degradation rate of organic matter in wastewater.

[0006] Technical solution: The circulating wastewater treatment system of the present invention includes a wastewater equalization tank, an ozone generation system, an ozone pressurization system, a pressurized dissolved gas tank, a reaction tank, and a catalyst circulation system; the pressurized dissolved gas tank is provided with multiple sets of liquid spray nozzles at the top and multiple sets of gas spray nozzles at the bottom, and a collection tank is provided below the gas spray nozzles;

[0007] The wastewater in the wastewater equalization tank is pressurized and then enters the pressurized dissolved gas tank through the liquid spray port at the top. The ozone generated by the ozone generation system is pressurized by the ozone pressurization system and then enters the pressurized dissolved gas tank through the gas spray port at the bottom. The pressurized wastewater and pressurized ozone form a convection system inside the pressurized dissolved gas tank. The pressurized dissolved gas tank is equipped with a contact zone to promote the contact between ozone and wastewater. The convection gas and water come into contact in the contact zone to form dissolved gas water, which falls into the collection tank at the bottom of the pressurized dissolved gas tank.

[0008] The bottom of the reaction tank is equipped with a catalyst release port and multiple dissolved gas water release ports, which are arranged in a ring around the catalyst release port. Dissolved gas water in the collection tank enters the reaction tank through the dissolved gas water release port, and catalyst particles enter the reaction tank through the catalyst release port. The top of the reaction tank is equipped with a catalyst particle and water separation device. The separated water is discharged from the reaction tank through the water outlet on the side wall, and the separated catalyst particles are discharged from the reaction tank through the material outlet on the side wall and enter the catalyst circulation system.

[0009] The ozone generation system includes a pure oxygen storage tank and an ozone generator; pure oxygen is used as the gas source to ensure ozone concentration, the ozone generator has an intake flow rate of 3-5 L / min, and the ozone concentration valve of the ozone generator is adjusted to control the outlet ozone concentration to 30-40 mg / L.

[0010] The ozone pressurization system includes an air compressor, a pneumatic plunger pump, and an ozone storage tank. The compressed air generated by the air compressor drives the ozone gas as a plunger pump, compressing the ozone pressure to 0.4-0.6 MPa and storing it in the ozone storage tank. The pressure is maintained at 0.4-0.6 MPa, and then the ozone enters the pressurized dissolved gas tank through the gas spray port at the bottom of the pressurized dissolved gas tank. The gas flow rate is 1-5 L / min.

[0011] Ozone gas is pressurized using a plunger pump, and the pressurized ozone gas and pressurized wastewater come into convective contact within a pressurized dissolved gas tank. According to Henry's Law, the saturated concentration of ozone gas in the liquid phase is directly proportional to the gas phase pressure. In this invention, the pressurized dissolved gas tank has a pressure of 0.6 MPa, while the conventional aeration release pressure is generally 0.3 MPa, which increases the liquid phase solubility. Simultaneously, because the gas and wastewater are in direct contact, the high specific heat capacity of the water can alleviate the heat generation during gas pressurization, preventing the accelerated self-decomposition of ozone at high temperatures. Furthermore, the pressurized dissolved gas tank is equipped with a contact zone to promote the contact between ozone and wastewater. This structure increases the turbulence at the gas-liquid contact surface. Based on the gas-liquid mass transfer equation, increasing the turbulence reduces the contact area between the gas and liquid phases, thereby increasing the gas-liquid mass transfer rate of ozone molecules, accelerating the transfer of ozone molecules from the gas phase to the liquid phase, and improving the solubility of ozone molecules in the water.

[0012] In this process, pressurized wastewater and pressurized ozone form a convection system within a pressurized dissolved air tank, which is pressurized to 0.5 MPa. The contact zone, designed to enhance the contact between ozone and wastewater, is at least two-thirds the height of the pressurized dissolved air tank. This contact zone includes two 316 stainless steel wire meshes fixed to the side walls of the tank, and multiple elliptical chlorinated polyvinyl chloride (PVC) balls placed between the wire meshes. The stacked PVC balls create gaps, allowing gas and water to pass only through these gaps, thus maximizing the contact between ozone and wastewater. The dissolved air falls into a collection tank at the bottom of the pressurized dissolved air tank, which is connected to the bottom of the reaction tank via a pipe. The pressurized dissolved air is released through a release port at the bottom of the reaction tank. The PVC balls fill approximately two-thirds of the contact zone's volume.

[0013] The system comprises 6 to 8 dissolved air water release ports, arranged in a circular pattern around the catalyst release port. Under pressure differential, the pressurized dissolved air water rapidly forms micro- and nano-bubbles. These bubbles contact the microcrystalline catalyst, where a large amount of reactive oxygen species (ROS) generated by the catalysis oxidizes and removes COD from the wastewater. On one hand, the small particle size of the formed micro- and nano-bubbles results in a longer hydraulic retention time than conventional aeration methods, allowing for sufficient contact with the catalyst and continuous ROS generation. On the other hand, as the micro- and nano-bubbles rise, they fluidize the microcrystalline catalyst, causing it to slowly ascend to the top of the reaction tank.

[0014] The separation device is a scraper installed on the top of the reaction tank. The scraper is connected to an external drive mechanism and rotates under the drive mechanism. The height of the lower edge of the scraper is the same as the height of the water outlet of the reaction tank. The scraper scrapes the microcrystalline catalyst on the water surface into the catalyst collection tank connected to the discharge port on the side wall of the reaction tank.

[0015] The catalyst circulation system comprises a catalyst collection tank, a catalyst cleaning tank, and a catalyst circulation tank connected in sequence. The bottom of the collection tank is funnel-shaped, and the catalyst enters the center of the catalyst cleaning tank from the bottom of the funnel. The cleaning tank has a spiral structure inside. After cleaning, the catalyst enters the catalyst circulation tank and is then pumped into the catalyst release port by a screw pump (the catalyst is in a solid-liquid mixed state after cleaning; pumping the catalyst particles with a screw pump achieves better solid-liquid separation and prevents damage to the catalyst particles). At the release port, the microcrystalline catalyst mixes and contacts with pressurized dissolved air water, continuously promoting the generation of ROS during the floating process. When it reaches the top of the reaction tank, it is scraped by a scraper to the catalyst collection tank, thus realizing the circulation of the microcrystalline catalyst.

[0016] The reaction tank is equipped with a baffle at the outlet to prevent catalyst from overflowing; the treated water flows out of the reaction tank through the outlet on the side wall.

[0017] The preparation method of the microcrystalline catalyst includes the following steps:

[0018] (1) Alumina and quartz sand are crushed and ground separately, and 200-300 mesh grinding media are screened out of each. Alumina powder and quartz sand powder are mixed at a mass ratio of 30:70 to obtain a mixture.

[0019] (2) Using carbon powder as a pore-forming agent, the mixture is mixed with carbon powder at a mass ratio of 25 to 30:1 to obtain a premix, and water is added to make it into a slurry; the mass ratio of water to premix is ​​104:100.

[0020] (3) Porous ceramic sphere preforms were prepared by pelletizing: During the forming process, a binder solution was sprayed into the slurry in the pelletizing machine to ensure that the preforms had good mechanical strength; the slurry material was placed in the pelletizer, and the binder solution was sprayed into the pelletizer every 5 seconds. Granulation was stopped after fine particles were formed (observe the changes in the material inside the pelletizer, and stop granulation after the flowing slurry was transformed into granules); preforms with a mesh size of 8-10 (1.7-2.4 mm) were screened out, placed in a cool and ventilated place to air dry naturally for 24 hours, and then placed in a constant temperature drying oven at 110℃ for 12 hours to dry.

[0021] (4) The dried body is placed in a muffle furnace for firing. First, the temperature inside the muffle furnace is raised to 500-600℃ and held at this temperature for 2 hours. Then, the temperature is raised to 1000-1200℃ and held for 2 hours. After turning off the muffle furnace, it is naturally cooled to room temperature and placed in a dry environment for 24 hours to obtain a porous ceramic body.

[0022] (5) The heterogeneous ozone catalyst was prepared by impregnation method: The porous ceramic preform from step (4) was impregnated in the active component solution and shaken in a shaker at a speed of 150-200 r / min for 12 h to reach adsorption equilibrium; after filtration, it was dried in an oven at 110-120℃ and then calcined in a muffle furnace at 550-600℃ for 1 h and aged for 24 h to obtain the microcrystalline catalyst; wherein, the active component solution is a mixed solution of ferric nitrate and manganese nitrate; the volume ratio of the porous ceramic preform to the mixed solution is 1:1.

[0023] In step (2), the granulator rotates at a speed of about 500 to 1000 r / min, and the binder solution is one of the following: a polyvinyl alcohol solution with a mass concentration of 5% to 20%, a polyacrylamide solution with a mass concentration of 0.1% to 1%, or a hydroxyethyl cellulose solution with a mass concentration of 1% to 3%; or any combination of the above.

[0024] The wastewater treatment system of this invention mixes pressurized wastewater with ozone and releases it in a reaction tank coupled with a microcrystalline catalyst. The microcrystalline catalyst is fluidized under the action of micro-nano bubbles and floats to the surface under the action of air flotation, and is then scraped to the collection tank by a surface scraper. The micro-nano bubbles come into contact with the microcrystalline catalyst to generate active oxygen species (ROS), which fully degrades the organic matter in the wastewater.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant effects:

[0026] (1) In the reaction vessel of the present invention, the pressurized dissolved gas water release port is arranged in a circular shape, and the center point is provided with a circulating microcrystalline catalyst release port. The pressurized dissolved gas water can fully drive the catalyst to move to the top in a fluidized state. On the one hand, the micro-nano bubbles have a long residence time in the water and can fully contact the catalyst in the time dimension. On the other hand, under the fluidized state, ozone and catalyst can continuously contact the top of the reaction vessel while enhancing mass transfer, and fully contact the catalyst in the spatial dimension and release ROS, thereby improving ozone utilization and catalytic oxidation efficiency, and significantly improving the degradation rate of organic matter in wastewater. This achieves both the degree of contact between ozone and catalyst under homogeneous catalysis and the recyclability of catalyst under heterogeneous catalysis.

[0027] (2) This invention promotes ozone gas dissolution under pressure and makes full use of the flotation effect under pressure release to enhance mass transfer and catalyst recovery; the microcrystalline catalyst combined with the dispersant enhances particle dispersion, so that the insoluble solid catalyst is uniformly dispersed in the liquid as a dispersion or suspension in the liquid. Under the floating effect of micro and nano bubbles, the catalyst floats to the surface and is scraped to the collection tank by a scraper to realize the recycling of the microcrystalline catalyst.

[0028] (3) In this invention, alumina and quartz sand are used as ceramic matrix materials. The matrix materials are fully mixed by pelletizing to ensure uniform particle size. A binder is added to enhance the adhesion of the powdered aggregate. After screening out the target particle size embryos, high-temperature sintering is carried out to ensure that the particle size range is consistent, which can avoid subsequent particle fluidization stratification or local eddy currents. Pores will be generated during the ceramic sintering process, but too high a temperature will cause the pores to close, and too low a temperature will reduce the strength of the ceramic. By adding carbon powder as a pore-forming agent, the carbon powder can be combusted and gasified in a high-temperature environment to expand into a porous structure inside the melt, ensuring the operating strength of the particles in the fluidized state.

[0029] (4) In this invention, iron and manganese metal oxides are loaded onto porous ceramics by impregnation, and two transition metals are introduced to form a multi-component alloy at the atomic scale. The Si-O-Mn and Si-O-Fe coordination structures formed complement each other to provide electron-rich centers for the adsorption of ozone molecules. This makes the catalyst have more oxygen vacancies and higher electron transfer capacity, thereby improving the catalytic performance. The small particle size and large specific surface area of ​​porous ceramics, as well as the more oxygen vacancies and surface hydroxyl groups formed after loading, make the porous ceramic catalyst have high strength and strong catalytic activity. Attached Figure Description

[0030] Figure 1 This is a system schematic diagram of the wastewater treatment system of the present invention;

[0031] Figure 2 This is a schematic diagram illustrating the principle of vortex cleaning in a catalyst cleaning tank.

[0032] Figure 3This is a schematic diagram showing the arrangement of the dissolved gas water release port and the catalyst release port in the reaction vessel. Detailed Implementation

[0033] like Figures 1-3 As shown, the circulating wastewater treatment system of the present invention includes a wastewater equalization tank, an ozone generation system, an ozone pressurization system, a pressurized dissolved gas tank, a reaction tank, and a catalyst circulation system. The pressurized dissolved gas tank has multiple sets of liquid spray nozzles at the top and multiple sets of gas spray nozzles at the bottom, with a collection tank below the gas spray nozzles. Wastewater from the wastewater equalization tank is pressurized and enters the pressurized dissolved gas tank through the liquid spray nozzles at the top. Ozone generated by the ozone generation system is pressurized by the ozone pressurization system and enters the pressurized dissolved gas tank through the gas spray nozzles at the bottom. The pressurized wastewater and pressurized ozone form a convection system within the pressurized dissolved gas tank. The pressurized dissolved gas tank is equipped with a process to promote contact between ozone and wastewater. In the contact zone, the convective gas and water come into contact to form dissolved gas water, which falls into the collection tank at the bottom of the pressurized dissolved gas tank. The bottom of the reaction tank is equipped with a catalyst release port and multiple dissolved gas water release ports, which are arranged in a circular pattern around the catalyst release port. The dissolved gas water in the collection tank enters the reaction tank from the dissolved gas water release port, and the catalyst particles enter the reaction tank from the catalyst release port. The top of the reaction tank is equipped with a catalyst particle and water separation device. The separated water is discharged from the reaction tank from the water outlet on the side wall, and the separated catalyst particles are discharged from the reaction tank from the material outlet on the side wall and enter the catalyst circulation system. A baffle is installed at the water outlet of the reaction tank to prevent catalyst overflow.

[0034] Among them, the wastewater is fed into the wastewater regulating tank through the inlet pipe, and the pH of the wastewater in the wastewater regulating tank is adjusted to 7-9. According to formulas (1) to (4), it can be seen that ROS is easily generated in this environment. Then, after being pressurized to 0.4-0.6 MPa by the water pump, it enters the pressurized dissolved gas tank through the liquid spray port at the top of the pressurized dissolved gas tank.

[0035] O3+OH - →O2+HO2 - (1)

[0036] O3+Ho2 - →·O2 - +·OH (2)

[0037] O3+·O2 - →·O2+·O3 - (3)

[0038] H2O+·O3 - →O2+·OH+OH - (4).

[0039] The ozone generation system includes a pure oxygen storage tank and an ozone generator. Pure oxygen is used as the gas source to ensure ozone concentration. The ozone generator's air intake is 3–5 L / min, and the ozone concentration valve is adjusted to control the outlet ozone concentration at 30–40 mg / L. The ozone pressurization system includes an air compressor, a pneumatic plunger pump, and an ozone storage tank. Compressed air generated by the air compressor is used as the driving gas for the plunger pump, compressing the ozone pressure to 0.4–0.6 MPa and storing it in the ozone storage tank. The pressure is maintained at 0.4–0.6 MPa, and then the ozone enters the pressurized dissolved gas tank through the gas spray port at the bottom, with a gas flow rate of 1–5 L / min. The plunger pump pressurizes the ozone gas, and the pressurized ozone gas and pressurized wastewater come into convective contact within the pressurized dissolved gas tank. According to Henry's Law, the liquid-phase saturation concentration of ozone gas is directly proportional to the gas-phase pressure. In this invention, the pressurized dissolved gas tank has a pressure of 0.6 MPa, while the conventional aeration release pressure is generally 0.3 MPa, which can increase the solubility in the liquid phase. At the same time, since the gas is in direct contact with the wastewater, the high specific heat capacity of the water can alleviate the heat generation during gas pressurization and avoid the aggravation of ozone self-decomposition at high temperatures. On the other hand, the pressurized dissolved gas tank is equipped with a contact zone to promote the contact between ozone and wastewater. Its structure can increase the turbulence at the gas-liquid contact surface. Based on the gas-liquid mass transfer equation, increasing the degree of turbulence can reduce the contact area between the gas and liquid phases, thereby increasing the gas-liquid mass transfer rate of ozone molecules, accelerating the transfer of ozone gas phase molecules to the liquid phase, and improving the solubility of ozone molecules in water.

[0040] The system comprises 6 to 8 dissolved air water release ports, arranged in a circular pattern around the catalyst release port. Under pressure differential, the pressurized dissolved air water rapidly forms micro- and nano-bubbles. These bubbles contact the microcrystalline catalyst, where a large amount of reactive oxygen species (ROS) generated by the catalysis oxidizes and removes COD from the wastewater. On one hand, the small particle size of the formed micro- and nano-bubbles results in a longer hydraulic retention time than conventional aeration methods, allowing for sufficient contact with the catalyst and continuous ROS generation. On the other hand, as the micro- and nano-bubbles rise, they fluidize the microcrystalline catalyst, causing it to slowly ascend to the top of the reaction tank.

[0041] The separation device is a scraper installed on the top of the reaction tank. The scraper is connected to an external drive mechanism and rotates under the drive mechanism. The height of the lower edge of the scraper is the same as the height of the water outlet of the reaction tank. The scraper scrapes the microcrystalline catalyst on the water surface into the catalyst collection tank connected to the discharge port on the side wall of the reaction tank.

[0042] The catalyst circulation system comprises a catalyst collection tank, a catalyst cleaning tank, and a catalyst circulation tank connected in sequence. The bottom of the collection tank is funnel-shaped, and the catalyst enters the center point of the catalyst cleaning tank from the bottom of the funnel. The interior of the cleaning tank has a spiral structure, and the catalyst flows along the spiral after entering the center point, which can reduce mutual collisions between catalysts during the cleaning process and extend its service life. After cleaning, the catalyst enters the catalyst circulation tank and is then pumped into the catalyst release port by a screw pump. The microcrystalline catalyst mixes and contacts with pressurized dissolved air water at the release port, continuously promoting the generation of ROS during the floating process. When it reaches the top of the reaction tank, it is scraped by a scraper to the catalyst collection tank, realizing the circulation of the microcrystalline catalyst.

[0043] Example 1

[0044] The method for preparing the microcrystalline catalyst of the present invention includes the following steps:

[0045] (1) Prepare 100g of solid alumina with a purity of 99.99%, place it in a crusher and adjust it to the fine scale. After crushing, filter it through a 200-mesh sieve, collect the filter powder and take 30g for later use.

[0046] (2) Prepare 100g of quartz sand with a purity of 99.99%, place it in a crusher and adjust it to the fine scale. After crushing, filter it through a 200-mesh sieve, collect the filter powder and take 70g for later use.

[0047] (3) Prepare 4g of carbon powder, mix it with the above 30g of alumina powder and 70g of quartz sand powder in a beaker, add 100g of water in several batches to form a slurry, and then put it into a granulator.

[0048] (4) Prepare 500 mL of 0.5% polyacrylamide aqueous solution in a spray bottle, turn on the granulator, spray it into the granulator every 5 seconds, and stop granulation after fine particles are formed; pass it through an 8-mesh sieve and then through a 10-mesh sieve, and keep the preform on the 10-mesh sieve.

[0049] (5) Place the above embryos in a cool and ventilated place to air dry naturally for 24 hours, and then place them in a constant temperature drying oven at 110℃ for 12 hours.

[0050] (6) Place the dried green body in a muffle furnace and heat it to 650°C at a heating rate of 100°C every 30 minutes, and maintain this temperature for 2 hours; then continue to heat it to 1100°C at a heating rate of 100°C every 30 minutes, and maintain this temperature for 2 hours; after turning off the muffle furnace, cool it down to 25°C and place it in a 25°C constant temperature drying oven to dry for 24 hours to obtain a porous ceramic green body;

[0051] (7) Take 404g of ferric nitrate nonahydrate and 251g of manganese nitrate tetrahydrate into a 500mL beaker, add distilled water to dissolve them, then transfer them to a 1000mL volumetric flask and make up to the mark; take 50mL of the mixed solution and mix it with about 50mL of embryo and place it in an Erlenmeyer flask.

[0052] (8) Place the conical flask in a shaker and shake it at 150 r / min for 12 h in a 30°C water bath environment; then filter it through a 5 mm filter bag, dry it in an oven at 115°C, and then calcine it in a muffle furnace at 550°C for 1 h; after taking it out, age it at room temperature for 24 h to obtain the microcrystalline catalyst.

[0053] Example 2

[0054] The method for preparing the microcrystalline catalyst of the present invention includes the following steps:

[0055] (1) Prepare 100g of solid alumina with a purity of 99.99%, place it in a crusher and adjust it to the fine scale. After crushing, filter it through a 200-mesh sieve, collect the filter powder and take 30g for later use.

[0056] (2) Prepare 100g of quartz sand with a purity of 99.99%, place it in a crusher and adjust it to the fine scale. After crushing, filter it through a 200-mesh sieve, collect the filter powder and take 70g for later use.

[0057] (3) Prepare 3.3g of carbon powder, mix it with the above 30g of alumina powder and 70g of quartz sand powder in a beaker, add 100g of water in several batches to form a slurry, and then put it into a granulator.

[0058] (4) Prepare 500 mL of 0.5% polyacrylamide aqueous solution in a spray bottle, turn on the granulator, spray it into the granulator every 5 seconds, and stop granulation after fine particles are formed; pass it through an 8-mesh sieve and then through a 10-mesh sieve, and keep the preform on the 10-mesh sieve.

[0059] (5) Place the above embryos in a cool and ventilated place to air dry naturally for 24 hours, and then place them in a constant temperature drying oven at 110℃ for 12 hours.

[0060] (6) Place the dried green body in a muffle furnace and heat it to 700°C at a heating rate of 100°C every 30 minutes, and maintain this temperature for 2 hours; then continue to heat it to 1200°C at a heating rate of 100°C every 30 minutes, and maintain this temperature for 2 hours; after turning off the muffle furnace, cool it down to 25°C and place it in a 25°C constant temperature drying oven to dry for 24 hours to obtain a porous ceramic green body;

[0061] (7) Take 404g of ferric nitrate nonahydrate and 251g of manganese nitrate tetrahydrate into a 500mL beaker, add distilled water to dissolve them, then transfer them to a 1000mL volumetric flask and make up to the mark; take 50mL of the mixed solution and mix it with about 50mL of embryo and place it in an Erlenmeyer flask.

[0062] (8) Place the conical flask in a shaker and shake it at 200 r / min for 12 h in a 25°C water bath environment; then filter it through a 5 mm filter bag, dry it in a 110°C oven, and then calcine it in a 600°C muffle furnace for 1 h; after taking it out, age it at room temperature for 24 h to obtain the microcrystalline catalyst.

[0063] Comparative Example 1

[0064] A method for preparing a microcrystalline catalyst includes the following steps:

[0065] (1) Prepare 100g of solid alumina with a purity of 99.99%, place it in a crusher and adjust it to the fine scale. After crushing, filter it through a 200-mesh sieve, collect the filter powder and take 30g for later use.

[0066] (2) Prepare 100g of quartz sand with a purity of 99.99%, place it in a crusher and adjust it to the fine scale. After crushing, filter it through a 200-mesh sieve, collect the filter powder and take 70g for later use.

[0067] (3) Prepare 4g of carbon powder, mix it with the above 30g of alumina powder and 70g of quartz sand powder in a beaker, add 100g of water in several batches to form a slurry, and then put it into a granulator.

[0068] (4) Prepare 500 mL of 0.5% polyacrylamide aqueous solution in a spray bottle, turn on the granulator, spray it into the granulator every 5 seconds, and stop granulation after fine particles are formed; pass it through an 8-mesh sieve and then through a 10-mesh sieve, and keep the preform on the 10-mesh sieve.

[0069] (5) Place the above embryos in a cool and ventilated place to air dry naturally for 24 hours, and then place them in a constant temperature drying oven at 110℃ for 12 hours.

[0070] (6) The dried preform was placed in a muffle furnace and heated to 650°C at a heating rate of 100°C every 30 minutes and maintained at this temperature for 2 hours. Then, the heating rate was increased by 100°C every 30 minutes and heated to 1100°C and maintained at this temperature for 2 hours. After the muffle furnace was turned off, the temperature was lowered to 25°C and dried in a 25°C constant temperature drying oven for 24 hours to obtain a porous ceramic catalyst.

[0071] Comparative Example 2

[0072] A method for preparing a microcrystalline catalyst includes the following steps:

[0073] (1) Prepare 100g of solid alumina with a purity of 99.99%, place it in a crusher and adjust it to the fine scale. After crushing, filter it through a 200-mesh sieve, collect the filter powder and take 30g for later use.

[0074] (2) Prepare 100g of quartz sand with a purity of 99.99%, place it in a crusher and adjust it to the fine scale. After crushing, filter it through a 200-mesh sieve, collect the filter powder and take 70g for later use.

[0075] (3) Mix the above 30g alumina powder and 70g quartz sand powder in a beaker, add 100g water in several batches to form a slurry, and then put it into a granulator.

[0076] (4) Prepare 500 mL of 0.5% polyacrylamide aqueous solution in a spray bottle, turn on the granulator, spray it into the granulator every 5 seconds, and stop granulation after fine particles are formed; pass it through an 8-mesh sieve and then through a 10-mesh sieve, and keep the preform on the 10-mesh sieve.

[0077] (5) Place the above embryos in a cool and ventilated place to air dry naturally for 24 hours, and then place them in a constant temperature drying oven at 110℃ for 12 hours.

[0078] (6) Place the dried green body in a muffle furnace and heat it to 650°C at a heating rate of 100°C every 30 minutes, and maintain this temperature for 2 hours; then continue to heat it to 1100°C at a heating rate of 100°C every 30 minutes, and maintain this temperature for 2 hours; after turning off the muffle furnace, cool it down to 25°C and place it in a 25°C constant temperature drying oven to dry for 24 hours to obtain a porous ceramic green body;

[0079] (7) Take 404g of ferric nitrate nonahydrate and 251g of manganese nitrate tetrahydrate into a 500mL beaker, add distilled water to dissolve them, then transfer them to a 1000mL volumetric flask and make up to the mark; take 50mL of the mixed solution and mix it with about 50mL of embryo and place it in an Erlenmeyer flask.

[0080] (8) Place the conical flask in a shaker and shake it at 150 r / min for 12 h in a 30°C water bath environment; then filter it through a 5 mm filter bag, dry it in an oven at 115°C, and then calcine it in a muffle furnace at 550°C for 1 h; after taking it out, age it at room temperature for 24 h to obtain the microcrystalline catalyst.

[0081] Example 3

[0082] For the pre-treated effluent from a dyeing and printing factory in Wuxi City, with a COD of 188 mg / L, pH = 7.3, and color (dilution factor) of 50 times, the wastewater treatment system of this invention was used for decolorization and deep treatment, specifically as follows:

[0083] Step 1: Place the microcrystalline catalyst from Example 1 into the catalyst circulation tank and wait for it to be delivered by the screw pump and released through the catalyst release port.

[0084] Step 2: Open the valve of the pure oxygen storage tank, adjust the ozone generator intake to 5L / min, and adjust the ozone generator current intensity to control the theoretical ozone concentration at the outlet to 36mg / L.

[0085] Step 3: Turn on the air compressor and adjust the pressure valve to ensure that compressed air enters the air-driven plunger pump at a pressure of 0.8 MPa. The plunger pump compresses the ozone generated by the ozone generator and stores it in the ozone storage tank at a pressure of 0.5 MPa.

[0086] Step 4: Wastewater at 10m 3 The water enters the equalization tank at a flow rate of / h, and the pH does not need to be adjusted. After being pressurized to 0.4Mpa by a water pump, it enters the liquid spray port at the top of the pressurized dissolved air tank.

[0087] Step 5: Simultaneously open the ozone storage tank outlet, adjust the flow rate to 2L / min, and let the compressed ozone gas enter the gas release port at the bottom of the pressurized dissolved gas tank.

[0088] Step 6: The pressurized wastewater and pressurized ozone gas come into convective contact in the pressurized dissolved gas tank. When the pressure in the pressurized dissolved gas tank reaches 0.5 MPa, open the outlet of the bottom dissolved gas water collection tank.

[0089] Step 7: Pressurized dissolved air water enters the dissolved air water release port at the bottom of the reaction tank. Under the pressure difference, micro- and nano-bubbles are rapidly formed and rise to the surface, causing the microcrystalline catalyst to fluidize. The hydraulic residence time in the reaction tank is 45 minutes. After the catalyst rises to the top, it is scraped by the catalyst scraper to the collection tank, then enters the cleaning tank for cleaning, and finally enters the circulation tank. The screw pump flow rate is 5 m / s. 3 / h, the recycled microcrystalline catalyst is fed into the release port of the reaction vessel.

[0090] Step 8: The treated wastewater flows out from the side outlet of the reaction tank. The COD of the effluent is 32 mg / L, the removal rate is 82.9%, and the color (dilution factor) is 2 times.

[0091] Example 4

[0092] For the pre-treated effluent from a dyeing and printing factory in Wuxi City, with a COD of 188 mg / L, pH = 7.3, and color (dilution factor) of 50 times, the wastewater treatment system of this invention was used for decolorization and deep treatment, specifically as follows:

[0093] Step 1: Place the microcrystalline catalyst from Example 2 into the catalyst circulation tank and wait for it to be delivered by the screw pump and released through the catalyst release port.

[0094] Step 2: Open the valve of the pure oxygen storage tank, adjust the ozone generator intake to 5L / min, and adjust the ozone generator current intensity to control the theoretical ozone concentration at the outlet to 36mg / L.

[0095] Step 3: Turn on the air compressor and adjust the pressure valve to ensure that compressed air enters the air-driven plunger pump at a pressure of 0.8 MPa. The plunger pump compresses the ozone generated by the ozone generator and stores it in the ozone storage tank at a pressure of 0.5 MPa.

[0096] Step 4: Wastewater at 10m 3 The water enters the equalization tank at a flow rate of / h, and the pH does not need to be adjusted. After being pressurized to 0.4Mpa by a water pump, it enters the liquid spray port at the top of the pressurized dissolved air tank.

[0097] Step 5: Simultaneously open the ozone storage tank outlet, adjust the flow rate to 2L / min, and let the compressed ozone gas enter the gas release port at the bottom of the pressurized dissolved gas tank.

[0098] Step 6: The pressurized wastewater and pressurized ozone gas come into convective contact in the pressurized dissolved gas tank. When the pressure in the pressurized dissolved gas tank reaches 0.5 MPa, open the outlet of the bottom dissolved gas water collection tank.

[0099] Step 7: Pressurized dissolved air water enters the dissolved air water release port at the bottom of the reaction tank. Under the pressure difference, micro- and nano-bubbles are rapidly formed and rise to the surface, causing the microcrystalline catalyst to fluidize. The hydraulic residence time in the reaction tank is 45 minutes. After the catalyst rises to the top, it is scraped by the catalyst scraper to the collection tank, then enters the cleaning tank for cleaning, and finally enters the circulation tank. The screw pump flow rate is 5 m / s. 3 / h, the recycled microcrystalline catalyst is fed into the release port of the reaction vessel.

[0100] Step 8: The treated wastewater flows out from the side outlet of the reaction tank. The COD of the effluent is 72 mg / L, the removal rate is 61.7%, and the color (dilution factor) is 8 times.

[0101] Example 5

[0102] For the pre-treated effluent from a dyeing and printing factory in Wuxi City, with a COD of 188 mg / L, pH = 7.3, and color (dilution factor) of 50 times, the wastewater treatment system of this invention was used for decolorization and deep treatment, specifically as follows:

[0103] Step 1: Take the microcrystalline catalyst of Comparative Example 1 and place it in the catalyst circulation tank. After being delivered by the screw pump, it will be released through the catalyst release port.

[0104] Step 2: Open the valve of the pure oxygen storage tank, adjust the ozone generator intake to 5L / min, and adjust the ozone generator current intensity to control the theoretical ozone concentration at the outlet to 36mg / L.

[0105] Step 3: Turn on the air compressor and adjust the pressure valve to ensure that compressed air enters the air-driven plunger pump at a pressure of 0.8 MPa. The plunger pump compresses the ozone generated by the ozone generator and stores it in the ozone storage tank at a pressure of 0.5 MPa.

[0106] Step 4: Wastewater at 10m 3 The water enters the equalization tank at a flow rate of / h, and the pH does not need to be adjusted. After being pressurized to 0.4Mpa by a water pump, it enters the liquid spray port at the top of the pressurized dissolved air tank.

[0107] Step 5: Simultaneously open the ozone storage tank outlet, adjust the flow rate to 2L / min, and let the compressed ozone gas enter the gas release port at the bottom of the pressurized dissolved gas tank.

[0108] Step 6: The pressurized wastewater and pressurized ozone gas come into convective contact in the pressurized dissolved gas tank. When the pressure in the pressurized dissolved gas tank reaches 0.5 MPa, open the outlet of the bottom dissolved gas water collection tank.

[0109] Step 7: Pressurized dissolved air water enters the dissolved air water release port at the bottom of the reaction tank. Under the pressure difference, micro- and nano-bubbles are rapidly formed and rise to the surface, causing the microcrystalline catalyst to fluidize. The hydraulic residence time in the reaction tank is 45 minutes. After the catalyst rises to the top, it is scraped by the catalyst scraper to the collection tank, then enters the cleaning tank for cleaning, and finally enters the circulation tank. The screw pump flow rate is 5 m / s. 3 / h, the recycled microcrystalline catalyst is fed into the release port of the reaction vessel.

[0110] Step 8: The treated wastewater flows out from the side outlet of the reaction tank. The COD of the effluent is 121 mg / L, the removal rate is 35.6%, and the color (dilution factor) is 8 times.

[0111] Example 6

[0112] For the pre-treated effluent from a dyeing and printing factory in Wuxi City, with a COD of 188 mg / L, pH = 7.3, and color (dilution factor) of 50 times, the wastewater treatment system of this invention was used for decolorization and deep treatment, specifically as follows:

[0113] Step 1: Take the microcrystalline catalyst of Comparative Example 2 and place it in the catalyst circulation tank. After waiting for the screw pump to deliver it, it will be released through the catalyst release port.

[0114] Step 2: Open the valve of the pure oxygen storage tank, adjust the ozone generator intake to 5L / min, and adjust the ozone generator current intensity to control the theoretical ozone concentration at the outlet to 36mg / L.

[0115] Step 3: Turn on the air compressor and adjust the pressure valve to ensure that compressed air enters the air-driven plunger pump at a pressure of 0.8 MPa. The plunger pump compresses the ozone generated by the ozone generator and stores it in the ozone storage tank at a pressure of 0.5 MPa.

[0116] Step 4: Wastewater at 10m 3 The water enters the equalization tank at a flow rate of / h, and the pH does not need to be adjusted. After being pressurized to 0.4Mpa by a water pump, it enters the liquid spray port at the top of the pressurized dissolved air tank.

[0117] Step 5: Simultaneously open the ozone storage tank outlet, adjust the flow rate to 2L / min, and let the compressed ozone gas enter the gas release port at the bottom of the pressurized dissolved gas tank.

[0118] Step 6: The pressurized wastewater and pressurized ozone gas come into convective contact in the pressurized dissolved gas tank. When the pressure in the pressurized dissolved gas tank reaches 0.5 MPa, open the outlet of the bottom dissolved gas water collection tank.

[0119] Step 7: Pressurized dissolved air water enters the dissolved air water release port at the bottom of the reaction tank. Under the pressure difference, micro- and nano-bubbles are rapidly formed and rise to the surface, causing the microcrystalline catalyst to fluidize. The hydraulic residence time in the reaction tank is 45 minutes. After the catalyst rises to the top, it is scraped by the catalyst scraper to the collection tank, then enters the cleaning tank for cleaning, and finally enters the circulation tank. The screw pump flow rate is 5 m / s. 3 / h, the recycled microcrystalline catalyst is fed into the release port of the reaction vessel.

[0120] Step 8: The treated wastewater flows out from the side outlet of the reaction tank. The COD of the effluent is 103 mg / L, the removal rate is 45.2%, and the color (dilution factor) is 8 times.

[0121] The comparison of Examples 3 to 6 shows that impregnation with iron and manganese can enhance the catalytic effect of the catalyst, while relying solely on the ceramic matrix for catalysis has limited effect on COD removal; at the same time, without the addition of carbon powder, it is difficult to form micropores, resulting in poor loading effect and thus affecting the catalytic removal effect.

[0122] Example 7

[0123] For the pre-treated effluent from a dyeing and printing factory in Wuxi City, with a COD of 188 mg / L, pH = 7.3, and color (dilution factor) of 50 times, a conventional ozone oxidation reaction column was used for decolorization and deep treatment, specifically as follows:

[0124] Step 1: Place the microcrystalline catalyst from Example 1 into the ozone oxidation reaction column, filling it to a height of 1 / 2 of the column.

[0125] Step 2: Pass wastewater into the reaction column from the top, and submerge the catalyst to 5cm above the top.

[0126] Step 3: Open the valve of the pure oxygen storage tank, adjust the ozone generator intake to 5L / min, and adjust the ozone generator current intensity to control the theoretical ozone concentration at the outlet to 36mg / L;

[0127] Step 4: Adjust the ozone generator outlet flow rate to 2L / min, and let the ozone gas enter the gas release port at the bottom of the reaction column;

[0128] Step 5: The generated ozone bubbles rise to the top of the reaction column, and in the process come into contact with the wastewater on the catalyst surface;

[0129] Step 6: After running for 30 minutes, take a sample from the side sampling port of the reaction column. The test results show that the COD of the effluent is 142 mg / L, the removal rate is 24.4%, and the color (dilution factor) is 32 times.

[0130] As demonstrated in Example 7, this invention enhances the solubility of ozone molecules and strengthens the mass transfer between the gas and liquid phases by pressurizing dissolved gas. Furthermore, by combining this with a self-made microcrystalline catalyst, a near-homogeneous system is formed in a fluidized bed, allowing ozone and the catalyst to fully contact and release reactive oxygen species (ROS), promoting the degradation of organic matter and achieving a high COD removal rate. Moreover, this invention utilizes a dissolved gas pressure release device to recover the microcrystalline catalyst, balancing the homogeneity of homogeneous catalysis with the recoverability of heterogeneous catalysis, avoiding the potential pollution impact of homogeneous catalysts on water bodies, and reducing operating costs.

Claims

1. A cyclic wastewater treatment system based on ozone oxidation, characterized by: The application relates to a wastewater treatment device and a preparation method of a catalyst. The preparation method of the catalyst comprises the following steps: (1) respectively crushing and grinding alumina and quartz sand, screening the grinding bodies of 200-300 meshes, mixing the alumina powder and the quartz sand powder according to the mass ratio of 30-35:70, and obtaining a mixture; (2) taking carbon powder as a pore-forming agent, mixing the mixture and the carbon powder according to the mass ratio of 25-30:1 to obtain a premix, and adding water to make the premix into a slurry; the mass ratio of the water to the premix is 104-105:100; (3) placing the slurry material in a granulator, spraying a binder solution into the granulator every 5-10 seconds, stopping granulation when the flowing slurry is changed into a granular state, screening the 8-10 mesh embryos, naturally air-drying the embryos in a cool and ventilated place, and then drying the embryos in a constant-temperature drying box with a temperature of 110-120 DEG C; (4) placing the dried embryos in a muffle furnace for sintering, first increasing the temperature in the muffle furnace to 500-600 DEG C, keeping the temperature at 500-600 DEG C for 2-3 hours, then continuously increasing the temperature to 1000-1200 DEG C, keeping the temperature at 1000-1200 DEG C for 2-3 hours, naturally cooling the muffle furnace to room temperature after turning off the muffle furnace, and obtaining the porous ceramic embryos in a dry environment; (5) immersing the porous ceramic embryos in the active component solution, oscillating in a shaking bed at a speed of 150-200 r / min for 12-14 hours to reach adsorption equilibrium, drying in a 110-120 DEG C oven, and then calcining in a 550-600 DEG C muffle furnace for 1-2 hours to obtain the microcrystalline catalyst; wherein the active component solution is a mixed solution of iron nitrate solution and manganese nitrate solution; and the adding volume ratio of the porous ceramic embryos to the mixed solution is 1:1-2.

2. The recirculating wastewater treatment system of claim 1, wherein: The ozone pressure system compresses the ozone pressure to 0.4-0.6 MPa; and the gas flow rate of the ozone entering the pressurized dissolved air tank from the gas spraying port of the lower part of the pressurized dissolved air tank is 1-5 L / min.

3. The recirculating wastewater treatment system of claim 1, wherein: The pressurized wastewater and the pressurized ozone form a convection system in the pressurized dissolved gas tank, and the pressure in the pressurized dissolved gas tank is kept at not less than 0.5 MPa.

4. The recirculating wastewater treatment system of claim 1, wherein: The contact zone comprises two stainless steel wire meshes fixed on the side wall of the pressurized dissolved gas tank, and a plurality of oval chlorinated polyvinyl chloride balls are arranged between the two wire meshes, and the gaps are formed between the stacked chlorinated polyvinyl chloride balls, so that the gas and water can only pass through the gaps. In the contact zone, the filling volume of the chlorinated polyvinyl chloride balls is 2 / 3 to 3 / 4 of the volume of the contact zone.

5. The recirculating wastewater treatment system of claim 1, wherein: The number of the dissolved gas water release ports is 6 to 8, and the release ports are arranged in a circular manner with the catalyst release port as the center.

6. The recirculating wastewater treatment system of claim 1, wherein: The catalyst circulation system comprises a catalyst collecting tank, a catalyst cleaning tank and a catalyst circulation tank which are connected in sequence; the bottom of the collecting tank is funnel-shaped, and the catalyst enters the center of the catalyst cleaning tank from the funnel-shaped bottom; the cleaning tank is internally provided with a spiral structure; after being cleaned, the catalyst enters the catalyst circulation tank, and then is pumped into the catalyst release port by a screw pump.

7. The recirculating wastewater treatment system of claim 1, wherein: A baffle is arranged at the water outlet of the reaction tank; and the treated water flows out of the reaction tank from the water outlet on the side wall of the reaction tank.

8. The recirculating wastewater treatment system of claim 1, wherein: In step (2), the rotating speed of the granulator is 500 to 1000 r / min, and the binder solution is one of a polyvinyl alcohol solution with a mass concentration of 5% to 20%, a polyacrylamide solution with a mass concentration of 0.1% to 1% or a hydroxyethyl cellulose solution with a mass concentration of 1% to 3%; or a combination of any number of the above solutions.

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