Sewage and wastewater advanced treatment and catalyst recycling method through catalytic ozonation coupling membrane separation

Abstract

The invention discloses an ozone catalytic oxidation coupling membrane separation sewage and wastewater advanced treatment and catalyst recycling method, and belongs to the technical field of sewage and wastewater treatment. The invention aims to solve the problem that the existing ozone powder catalyst is difficult to recover and not easy to reuse. By developing a catalytic ozonation coupling membrane separation process, an integrated process structure and a split process structure and an operation mode are provided, and a backwashing method is utilized, so that recycling of a high-efficiency powder catalyst is realized, and deep treatment and purification of sewage and wastewater are coordinated. According to the method, the high efficiency of ozone oxidation is fully exerted, a large number of hydroxyl free radicals generated by fast catalytic ozonolysis efficiently oxidize and degrade organic matters, the influence of complex water quality can be dealt with, a regular membrane cleaning strategy is adopted, membrane pollution is effectively relieved, the service life of a membrane is prolonged, and the recovery rate and catalytic efficiency of a catalyst are ensured; the device has the advantages of easiness in operation, small occupied area, simple equipment structure, easiness in long-term operation and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and specifically relates to a method for deep treatment of wastewater and catalyst recycling by ozone catalytic oxidation coupled with membrane separation. Background Art

[0002] A large amount of wastewater is released during the production and living processes in cities. Some of the organic pollutants and pathogens are difficult to be degraded by microorganisms and remain in the environment for a long time, posing a serious threat to human hygiene and health. The usual method is to further treat these wastewaters. Among them, ozone oxidation has been widely used due to its high organic matter removal efficiency and simultaneous decolorization and sterilization. In the practice of wastewater treatment projects, heterogeneous catalytic ozone oxidation is usually used to improve ozone utilization efficiency. Powder catalysts have the advantages of large specific surface area and high active site density, which are conducive to catalytic ozone oxidation reactions. However, they have disadvantages such as difficulty in recycling, difficulty in reuse, and easy to cause secondary pollution, which limit their application in ozone catalytic oxidation. Based on this, researchers have proposed a variety of improvement schemes, including (1) granulating the catalyst to form a supported catalyst; (2) introducing magnetic materials; (3) developing a set of easy-to-implement and highly operational methods for efficient recovery of powder catalysts.

[0003] Patent CN113526649A designs a catalytic ozone oxidation reactor for sewage treatment, in which an iron-based loaded catalyst A and a copper-based loaded catalyst B are sequentially loaded on a supporting grid to catalyze ozone to produce a free radical oxidation reaction to treat sewage. The volume ratio of catalyst A and catalyst B is 60% to 40%: 40% to 60%. Although the problem of solid-liquid separation has been solved for loaded catalysts, they still face many difficulties in the actual preparation and application process. The complex preparation process means that the preparation cost of the catalyst is high, and it is difficult to achieve industrial mass production. The limited specific surface area determines that its ozone utilization efficiency is often not as good as that of a powder catalyst. In addition, due to the addition of a carrier, there may be hidden dangers such as agglomeration of active components, poor dispersion, easy loss, unstable carrier, and excessive metal dissolution, which affect the mass transfer of ozone at the gas-liquid interface. Patent CN114849727A prepares a magnetic loaded ozone catalyst with activated carbon as the carrier and Fe 3+ 、Fe 2+ 、Metal ion Mn 2+ and Cu 2+As the main component, the catalyst is recovered by a magnetic separation device under a magnetic field strength of 0.2 to 5.0 T, and a recovery rate of more than 97.5% is finally achieved. Patent CN219907302U prepares a magnetic biomass fly ash catalyst, which solves the problem of expensive and difficult separation of powdered catalysts, realizes the resource utilization of fly ash solid waste and simultaneous water purification, but the simple use of magnets for adsorption is inefficient and has poor selectivity. Although the introduction of magnetic catalysts is easy to recycle, it also has high requirements for the stability of the catalyst. The supporting continuous magnetic separation device and the complex catalyst preparation process increase the cost and energy consumption. Patent CN107915309A invented a complex process: water mixing, catalytic oxidation reaction, catalyst separation and automatic circulation, clean water storage and pulse backwashing, which realizes the efficient separation and automatic circulation of powdered ozone catalysts. However, the use of centrifugal hydraulic retention pulse separators for solid-liquid separation still faces problems such as complex control and high energy consumption. Patent CN118754249A designs a photocatalytic membrane coupled reactor that continuously circulates powdered photocatalyst TiO2 and wastewater in a water storage tank and a photocatalytic tank to achieve a continuous heterogeneous photocatalytic process. At the same time, the ultrafiltration membrane separation unit is used to complete the replenishment and recovery of the catalyst. The ultrafiltration membrane completes solid-liquid separation through the physical screening effect of tiny pores. The active catalytic components will not be changed during the process. It is an ideal method for intercepting and reusing powdered catalysts. However, due to the lack of a suitable cleaning strategy, the ultrafiltration membrane is bound to cause serious membrane fouling after long-term operation, which greatly reduces the separation performance and shortens the service life. Therefore, the control of membrane fouling in the process is not only related to the effect of membrane separation, but also involves the long-term operating costs of the device and process. Patent CN117682652A proposes an ozone catalytic oxidation treatment device and process for refractory organic wastewater. The process flow includes: submerged ultrafiltration-ozonation catalytic oxidation-membrane separation. Ozone catalytic oxidation is set up in two stages. Hydrogen peroxide is added to the first stage of ozone catalytic oxidation, and a solid powder catalyst is used for the second stage of ozone catalytic oxidation. The mixed liquid of the second stage of ozone catalytic oxidation then enters the inorganic ceramic membrane assembly. Driven by the internal pressure, the wastewater is discharged in compliance with the standards, and the solid powder catalyst mixed concentrate is refluxed to the second stage ozone reactor for recycling. With the help of the antioxidant properties and mesoporous structure of the inorganic ceramic membrane, damage to the membrane material of the organic membrane in an ozone environment is avoided, and catalyst reuse is achieved. However, the addition of hydrogen peroxide increases the investment in operating costs, and the powder catalyst trapped on the membrane surface cannot be effectively recovered, resulting in catalyst loss, reducing the ozone catalytic efficiency, and causing serious membrane blockage.Patent CN112960818A invented a three-phase electrochemical water treatment device for electrochemical-ozone coupled oxidation. The membrane assembly is immersed in the reactor to intercept pollutants and catalysts; aeration at the bottom flushes the membrane surface, and the filter membrane has both forward washing and backwashing functions, realizing continuous and efficient recycling of the catalyst in the reactor and simultaneously mitigating pollution. However, the operating mode is single and cannot cope with complex water quality. In the environment of strong electricity and ozone, the membrane may be corroded.

[0004] In order to remedy the above defects, the present invention has developed a method for deep treatment of wastewater and catalyst recycling by ozone catalytic oxidation coupled with membrane separation. Two process structures and related operating modes are designed. On the premise of deep treatment of wastewater, backwashing is used to recover high-efficiency powdered catalyst, simultaneously alleviating membrane pollution and reducing catalyst loss. Summary of the Invention

[0005] The present invention provides a method for advanced wastewater treatment and catalyst reuse that combines ozone catalytic oxidation with membrane separation. This method achieves the recycling of highly efficient powdered catalysts and synergistically supports advanced wastewater treatment and purification. This method not only fully leverages the high efficiency of ozone oxidation, rapidly catalyzing the large number of hydroxyl radicals generated by ozone decomposition to efficiently oxidize and degrade organic matter, but also proposes both integrated and split process structures to address the impact of complex water quality. Furthermore, corresponding operating modes are provided to guide the long-term operation of the process, further alleviating membrane fouling, extending membrane service life, and ensuring catalyst recovery and catalytic efficiency.

[0006] The present invention provides a method for deep treatment of wastewater and catalyst reuse by ozone catalytic oxidation coupled with membrane separation, which is characterized by comprising ozone catalytic oxidation and membrane separation units. Its principle, process structure, membrane materials and parameters, operation mode, operation parameters, catalyst types and their addition and recovery methods, and treatment efficiency for typical industrial tail water are as follows: ① Principle: The hydroxyl radicals generated by the ozone catalytic oxidation process can effectively degrade organic matter in typical industrial tail water and control membrane pollution; the membrane treatment process can stably retain powdered catalysts, and the elution and reuse of catalyst particles can be achieved by backwashing; ② Process structure: The process has two structures: integrated and split. The integrated structure is as follows: Figure 1 As shown, the membrane assembly is fixed in the ozone catalytic oxidation membrane separation device. A microporous aeration plate is provided at the bottom of the device, which is connected to the ozone generator to realize the gas source input. An outlet pipe is provided on the left side of the top to connect the tail gas destruction device. A water inlet and a feed port are provided at the bottom and top of the left wall respectively. The split structure is shown in FIG. Figure 2As shown in the figure, a backwash liquid reflux pipe is provided on the top right side of the ozone catalytic oxidation device, and a water outlet is provided in the middle of the right wall; ③ Membrane materials and parameters: Due to the advantages of inorganic ceramic membranes such as high mechanical strength, thermal stability and anti-oxidation, the membrane used in the membrane separation unit is an inorganic ceramic membrane, including tubular ceramic membranes and flat ceramic membranes, with a membrane pore size of 40-60 nm and an effective filtration area of ​​0.008-0.014 m 2 ;④ Operation mode: The integrated structure uses a flat ceramic membrane and operates in a batch mode. It is divided into three stages: water inlet, ozone catalytic oxidation membrane separation and backwashing, which are carried out in sequence. The water inlet section is 60 minutes, the ozone catalytic oxidation membrane separation section is completed by ozone catalytic oxidation and dead-end mode membrane separation for 90 minutes, and the backwashing section runs for 30 minutes. The above integrated structure process consists of three groups of treatment units, which operate alternately. Figure 3 The split structure is not limited to the use of flat ceramic membranes or tubular ceramic membranes, and operates in batch mode. It is divided into four stages: water inlet, ozone catalytic oxidation, membrane separation and backwashing, which are carried out in sequence. The water inlet section is 60 minutes, the ozone catalytic oxidation section is 120 minutes, the wastewater is first subjected to ozone catalytic oxidation, and the effluent enters the inorganic ceramic membrane assembly for solid-liquid separation. The membrane separation section operates in cross-flow / dead-end mode for 30 minutes, and the backwash section operates for 30 minutes. The above-mentioned integrated structure process consists of four groups of treatment units, which operate alternately. Figure 4 ; ⑤Operating parameters: ozone concentration is 20-40 mg / L, catalyst dosage is 150-450 mg / L, aeration time is 90-120 min, transmembrane pressure difference is 0.1-0.3 bar, backwash pressure is 0.3-0.5 bar, backwash time is 15-30 min, when using a split structure, the membrane surface velocity of cross-flow filtration is controlled at 800-1000 mL / min; ⑥Catalyst type and its addition and recovery method: solid powder catalysts include metal oxide powder catalysts (CuMn2O4, MnO2-Co3O4, LaCoO3, CuCo2O4, CuFe2O4 and red mud), carbon material powder catalysts (reduced graphene oxide, nitrogen-doped graphene) and composite powder catalysts (CuMn2O4 / graphene, LaCoO3 / carbon nitride, CuMn2O4 / carbon nitride); solid powder catalysts are removed from the reactor before entering the water. Figure 1 and Figure 2 In the integrated structure, the catalyst retained on the membrane surface is washed away by backwashing and returned to the ozone catalytic oxidation device. In the split structure, the catalyst mixture after backwashing is washed away by Figure 2The reflux pipe in the reactor refluxes to the ozone catalytic oxidation device to achieve catalyst recycling; ⑦ Treatment efficiency of typical industrial tail water: The COD removal rate of typical industrial tail water can reach 45-60%, which can ensure that the COD effluent of industrial tail water is less than 50 mg / L, and the recovery rate of powdered catalyst is stable at 75-85%. After backwashing, the water flux of inorganic ceramic membrane can be increased by 25-35%.

[0007] The beneficial effects of this invention are: the powdered catalyst used in this technology can improve ozone oxidation efficiency, effectively remove organic matter, and avoid secondary pollution. The catalyst is also easily recyclable and reusable, with a long service life. The use of ozone catalytic oxidation coupled with a membrane separation process, combined with a reasonable operating mode, can ensure stable effluent and membrane permeation flux, reducing operating costs. This is a promising new technology for advanced wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a diagram of the integrated structure of ozone catalytic oxidation coupled membrane separation according to the present invention;

[0009] Figure 2 This is a diagram of the split structure of the ozone catalytic oxidation coupled membrane separation of the present invention;

[0010] Figure 3 This is a diagram of the integrated operation mode of ozone catalytic oxidation coupled with membrane separation according to the present invention;

[0011] Figure 4 This is a diagram of the integrated operation mode of ozone catalytic oxidation coupled with membrane separation according to the present invention;

[0012] Reference numerals

[0013] Among them: 1-water inlet pump; 2-ozone catalytic oxidation membrane separation device / ozone catalytic oxidation device; 3-feed inlet; 4-microporous aeration plate; 5-ozone generator; 6-membrane assembly; 7-membrane assembly circulation pump; 8-backwash water pump; 9-clear water tank. DETAILED DESCRIPTION

[0014] The present invention will be further described in detail with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0015] Specific implementation method 1: This process can be operated in an integrated structure, using a catalytic ozone oxidation coupled membrane separation process to deeply treat the difficult-to-degrade organic matter in industrial tail water while achieving efficient recycling of powdered catalysts and saving operating costs. The ceramic membrane uses a flat ceramic membrane and operates in batch mode and dead-end filtration. The membrane assembly is completely immersed in the water body and achieves solid-liquid separation under pressure, and the wastewater is discharged in compliance with the standards. Afterwards, the clean water from the clear water tank is used for backwashing, the catalyst is washed off and recycled in situ. The specific process flow is divided into three stages: water inlet, ozone catalytic oxidation membrane separation and backwashing. The water inlet section is 60 minutes, the ozone catalytic oxidation membrane separation section is completed by ozone catalytic oxidation and dead-end mode membrane separation simultaneously for 90 minutes, and the backwash section runs for 30 minutes. The alternating operation of the three treatment units can ensure the continuity of water inlet and alleviate the treatment load. Operating parameters: ozone concentration is 20-40 mg / L, catalyst dosage is 150-450 mg / L, aeration time is 90-120 min, transmembrane pressure difference is 0.1-0.3 bar, backwash pressure is 0.3-0.5 bar, and backwash time is 15-30 min.

[0016] Specific embodiment 2: In this embodiment, a split structure is adopted for operation. A flat ceramic membrane is selected as the ceramic membrane. It operates in a batch mode and dead-end filtration mode. The effluent from the catalytic ozone oxidation reactor enters the membrane assembly. At the same time, solid-liquid separation is achieved under the drive of pressure, and the wastewater is discharged after meeting the standards. Afterwards, the clean water from the clean water tank is used for backwashing to elute the catalyst and return the mixed liquid to the catalytic ozone oxidation device to achieve the recycling of high-efficiency powdered catalyst. The specific process flow is divided into four stages: water inlet, ozone catalytic oxidation, membrane separation and backwashing. The water inlet section is 60 minutes, the ozone catalytic oxidation section is 120 minutes, the wastewater is first subjected to ozone catalytic oxidation, and the effluent enters the inorganic ceramic membrane assembly for solid-liquid separation. The membrane separation section operates in dead-end mode for 30 minutes, and the backwash section operates for 30 minutes to ensure the continuity of water inlet. The operating parameters are: ozone concentration is 20-40 mg / L, catalyst dosage is 150-450 mg / L, aeration time is 90-120 minutes, transmembrane pressure difference is 0.1-0.3 bar, backwash pressure is 0.3-0.5 bar, and backwash time is 15-30 minutes.

[0017] Specific implementation method three: In this implementation method, a split structure is adopted for operation. The ceramic membrane uses a tubular ceramic membrane and operates in a batch mode and cross-flow filtration mode. The effluent of the catalytic ozone oxidation reactor enters the membrane assembly and realizes solid-liquid separation under the drive of pressure. The wastewater is discharged after meeting the standards. Afterwards, the clean water in the clear water tank is used for backwashing to elute the catalyst and return the mixed liquid to the catalytic ozone oxidation device to realize the recycling of high-efficiency powder catalyst. The specific process flow is divided into four stages: water inlet, ozone catalytic oxidation, membrane separation and backwashing. The water inlet section is 60 minutes, the ozone catalytic oxidation section is 120 minutes, the wastewater is first subjected to ozone catalytic oxidation, and the effluent enters the inorganic ceramic membrane assembly for solid-liquid separation. The membrane separation section operates in a dead-end mode for 30 minutes, and the backwash section operates for 30 minutes to ensure the continuity of water inlet. At the same time, with the help of the cross-flow membrane operation mode, flushing the membrane surface can further alleviate membrane pollution. Operating parameters: ozone concentration is 20-40 mg / L, catalyst dosage is 150-450 mg / L, aeration time is 90-120 min, transmembrane pressure difference is 0.1-0.3 bar, backwash pressure is 0.3-0.5 bar, backwash time is 15-30 min, membrane surface flow rate is 800-1000 mL / min.

[0018] The specific embodiments described above are only preferred implementations of the present invention, but other aspects and implementations will be obvious to those skilled in the art. Without departing from the principles of the present invention, several variations and improvements may be made, all of which fall within the scope of protection of this application.

Claims

1. A method for deep treatment of wastewater and catalyst recycling by ozone catalytic oxidation coupled with membrane separation, characterized in that It includes ozone catalytic oxidation and membrane separation units. Its principle, process structure, membrane materials and parameters, operation mode, operation parameters, catalyst types and their addition and recovery methods, and treatment efficiency for typical industrial tail water are as follows: ① Principle: The hydroxyl radicals generated by the ozone catalytic oxidation process can effectively degrade organic matter in typical industrial tail water and control membrane fouling; the membrane treatment process can stably retain powdered catalysts, and the catalyst particles can be eluted and reused through backwashing; ② Process structure: The process has two structures: integrated and split. In the integrated structure, the membrane assembly is fixed in the ozone catalytic oxidation membrane separation device. A microporous aeration plate is provided at the bottom of the device, which is connected to the ozone generator to realize the gas source input. An outlet pipe is provided on the left side of the top, which is connected to the tail gas destruction device. The water inlet and feeding port are respectively provided at the bottom and top of the left wall. In the split structure, a backwash liquid reflux pipe is also provided on the right side of the top of the ozone catalytic oxidation device, and a water outlet is provided in the middle of the right wall. ③Membrane materials and parameters: Due to the advantages of inorganic ceramic membranes such as high mechanical strength, thermal stability and anti-oxidation, the membrane used in the membrane separation unit is inorganic ceramic membrane, including tubular ceramic membrane and flat ceramic membrane, with a membrane pore size of 40-60nm and an effective filtration area of ​​0.008-0.014m 2 ; ④ Operation mode: The integrated structure uses a flat ceramic membrane and operates in a batch mode. It is divided into three stages: water inlet, ozone catalytic oxidation membrane separation and backwashing, which are carried out in sequence. The water inlet section is 60 minutes, the ozone catalytic oxidation membrane separation section is completed by ozone catalytic oxidation and dead-end mode membrane separation simultaneously for 90 minutes, and the backwashing section runs for 30 minutes. The above-mentioned integrated structure process consists of three groups of treatment units, which operate alternately; the split structure is not limited to using flat ceramic membranes or tubular ceramic membranes, and operates in a batch mode. It is divided into four stages: water inlet, ozone catalytic oxidation, membrane separation and backwashing, which are carried out in sequence. The water inlet section is 60 minutes, the ozone catalytic oxidation section is 120 minutes, the wastewater is first subjected to ozone catalytic oxidation, and the effluent enters the inorganic ceramic membrane assembly for solid-liquid separation. The membrane separation section operates in a cross-flow / dead-end mode for 30 minutes, and the backwashing section runs for 30 minutes. The above-mentioned integrated structure process consists of four groups of treatment units, which operate alternately; ⑤Operation parameters: ozone concentration is 20-40 mg / L, catalyst dosage is 150-450 mg / L, aeration time is 90-120 min, transmembrane pressure difference is 0.1-0.3 bar, backwash pressure is 0.3-0.5 bar, backwash time is 15-30 min, when using a split structure, the membrane surface velocity of cross-flow filtration is controlled at 800-1000 mL / min; ⑥ Catalyst types and their addition and recovery methods: Solid powder catalysts include metal oxide powder catalysts (CuMn2O4, MnO2-Co3O4, LaCoO3, CuCo2O4, CuFe2O4 and red mud), carbon material powder catalysts (reduced graphene oxide, nitrogen-doped graphene) and composite powder catalysts (CuMn2O4 / graphene, LaCoO3 / carbon nitride, CuMn2O4 / carbon nitride); solid powder catalysts are added from the feeding ports in Figures 1 and 2 before water is introduced; in the integrated structure, the catalyst retained on the membrane surface is eluted by backwashing and returned to the ozone catalytic oxidation device. In the split structure, the catalyst mixture after backwashing is refluxed to the ozone catalytic oxidation device through the reflux pipe in Figure 2, thereby realizing catalyst recycling; ⑦ Treatment efficiency of typical industrial tail water: The COD removal rate of typical industrial tail water can reach 45-60%, which can ensure that the COD effluent of industrial tail water is less than 50 mg / L. The recovery rate of powdered catalyst is stable at 75-85%. After backwashing, the water flux of inorganic ceramic membrane can be increased by 25-35%.

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