Multi-stage advanced oxidation treatment method and treatment system

Abstract

The invention relates to the field of water treatment, and particularly discloses a multi-stage advanced oxidation treatment method and a treatment system.The treatment method comprises the following steps that S1, after the pH of wastewater is adjusted to be acidic, an inert metal composite catalyst is added for pretreatment, and chain scission is conducted on refractory organic matter; s2, adding ferrite and a hydrogen peroxide solution into the wastewater pretreated in the step S1, and performing Fenton oxidation treatment; s3, carrying out aeration treatment on the wastewater treated in the step S2; s4, adjusting the pH value of the sewage subjected to aeration treatment back to be neutral or alkaline, then adding a flocculating agent for coagulating sedimentation, and then discharging water; the invention further discloses a treatment system for implementing the treatment method. The treatment system comprises a pretreatment unit, an advanced oxidation unit, an aeration unit and a coagulating sedimentation unit which are sequentially communicated in the wastewater flowing direction. According to the present invention, the wastewater treatment effect is further improved, and the excellent COD and chroma removal effect is provided.

Description

Technical Field

[0001] The present application relates to the field of water treatment, and more specifically, to a multi-stage advanced oxidation treatment method and treatment system. Background Art

[0002] With the rapid development of industry, the types and quantities of wastewater are increasing, which contains a large number of organic pollutants that are difficult to biodegrade. Traditional wastewater treatment methods are often difficult to effectively remove these pollutants. Advanced oxidation technology has attracted widespread attention because it can produce strong oxidizing free radicals and thus efficiently decompose organic pollutants.

[0003] More specifically, the basis of advanced oxidation technology lies in the use of catalysts, radiation (such as light radiation, ultrasound, etc.), and sometimes in combination with oxidants, to produce highly active free radicals (generally hydroxyl radicals) in the reaction. These free radicals have extremely high oxidation potentials and can oxidize and degrade large molecular weight, difficult-to-degrade organic matter in water bodies into low-toxic or non-toxic small molecular substances through addition, substitution, electron transfer, bond breaking and other reactions with organic compounds, or even directly degrade them into carbon dioxide and water, thereby achieving complete mineralization of pollutants.

[0004] However, the existing advanced oxidation technology has the problem of unsatisfactory treatment effect when treating complex wastewater using a single treatment method. Summary of the invention

[0005] In order to further improve the wastewater treatment effect, the present application provides a multi-stage advanced oxidation treatment method and treatment system.

[0006] In the first aspect, the present application provides a multi-stage advanced oxidation treatment method, which adopts the following technical solution: A multi-stage advanced oxidation treatment method comprises the following steps: S1. After adjusting the pH of the wastewater to acidic, an inert metal composite catalyst is added for pretreatment to break the chain of the refractory organic matter; S2, adding ferrous salt and hydrogen peroxide solution to the wastewater pretreated in step S1 to perform Fenton oxidation treatment; S3, aeration treatment of the wastewater after treatment in step S2; S4. The pH of the sewage after aeration treatment is adjusted to neutral or alkaline, and then flocculants are added for coagulation and sedimentation before discharge.

[0007] By adopting the above technical scheme, in the present application, the wastewater is first adjusted to an acidic condition, and then an inert metal composite catalyst is added for pretreatment to break the chain of the refractory organic matter, thereby improving the biodegradability of the wastewater and improving the efficiency of the subsequent addition of ferrous salt and hydrogen peroxide solution for Fenton advanced oxidation. Then, ferrous salt and hydrogen peroxide solution are added to generate hydroxyl radicals to oxidatively decompose the organic pollutants in the wastewater, thereby greatly reducing COD. At the same time, due to the oxidative decomposition of organic matter, the chromaticity is also significantly improved. Then, the wastewater after the advanced oxidation is completed is aerated to continue to fully react the Fenton reagent that has not completed the reaction. , further promoting the oxidative decomposition of residual organic matter after the Fenton reaction, thereby further reducing COD and chromaticity, and then adjusting the pH of the aerated sewage to help terminate the Fenton reaction and stabilize the properties of the wastewater, and then adding flocculants for coagulation and sedimentation, promoting the aggregation of suspended matter and colloidal substances in the wastewater into larger particles, which are convenient for removal by coagulation and sedimentation, and further reducing the chromaticity. Finally, in this application, different types of advanced oxidation reactions are carried out in stages, which improves the treatment effect and reduces the treatment cost. The treated wastewater has a lower COD value and chromaticity. The method provided in this application has a better effect on COD removal.

[0008] Optionally, in step S1, the pH value of the wastewater is adjusted to 3-4.

[0009] By adopting the above technical solution, the wastewater is adjusted to a strongly acidic condition, and with the action of an inert metal composite catalyst, active sites can be provided to reduce the activation energy required for the breakage of organic molecules, and difficult-to-degrade organic molecules can be broken down, converting large molecules into small molecules, thereby improving the water treatment effect. Moreover, this pH condition is more conducive to Fenton oxidation.

[0010] Optionally, in step S1, the inert metal composite catalyst is prepared by co-precipitation of an inert metal salt and an iron salt to obtain a composite precipitate, which is then mixed with a phenolic resin and a porous polyester matrix after aging and then calcined in a hydrogen atmosphere, wherein the inert metal salt is selected from one or both of platinum salt and palladium salt.

[0011] By adopting the above technical scheme, the inert metal catalyst prepared in the present application can activate the difficult-to-degrade organic molecules in the wastewater by providing active sites under acidic conditions. These active sites can reduce the activation energy required for the breakage reaction of the organic molecules and increase the activation energy, thereby accelerating the reaction rate. At the same time, the good chemical stability of the inert metal ensures the long-term catalytic activity of the catalyst in an acidic environment. Through the chain scission reaction, the macromolecular organic matter is decomposed into small molecular fragments that are more easily degraded by microorganisms, thereby significantly improving the biodegradability of the wastewater. This treatment method creates more favorable conditions for the subsequent biochemical treatment steps and improves the efficiency and effect of the entire wastewater treatment process.

[0012] Optionally, the inert metal composite catalyst in step S1 is prepared by the following method: 1) Dissolve the inert metal salt and the iron salt in water, and stir to mix to obtain a metal salt solution; 2) adding the prepared metal salt solution dropwise to a sodium hydroxide solution to precipitate metal ions to form a composite precipitate; 3) Filter the obtained composite precipitate and treat it at a constant temperature of 280-320°C for 1-2h, then wash it with water and dry it; 4) mixing the composite precipitate treated in step 3) with a porous polyester matrix, and then mixing with a water-soluble phenolic resin and water, and preparing a mixture after ultrasonic dispersion at 45-55° C. for 20-30 minutes; 5) After filtering the obtained mixture, calcining it in a hydrogen atmosphere at a temperature of 680-750° C. for 2-3 hours to obtain an inert metal composite catalyst.

[0013] By adopting the above technical scheme, the inert metal composite catalyst in the present application is mixed with an inert metal salt, platinum salt or palladium salt and an iron salt and then co-precipitated in a sodium hydroxide solution to form a uniform inert metal-metal composite structure, and then an aging treatment is performed to enhance its structural stability, and then it is mixed with a phenolic resin and a porous polyester matrix and calcined in a hydrogen atmosphere. The phenolic resin plays a certain bonding role, which is beneficial to the loading of the composite precipitate on the porous polyester matrix, and the addition of a water-soluble phenolic resin and water is more conducive to the dispersion of the composite precipitate and the porous polyester matrix in the aqueous solution system. Then, after filtering out the solvent water, it is calcined in a hydrogen atmosphere, so that the platinum or palladium in the composite precipitate is reduced to a nano platinum or palladium catalyst, and the iron salt is also After being reduced to nano-iron, the phenolic resin and porous polyester matrix form a carbon skeleton under high-temperature calcination to realize the loading of the inert metal composite catalyst, thereby increasing the contact area between the inert metal catalyst and the wastewater. Moreover, the carbon skeleton formed after calcination can also form an iron-carbon micro-electrolysis primary cell with iron, and the long-chain or cyclic macromolecular organic matter is opened and broken and degraded through redox reaction, thereby converting it into easily degradable small-molecule organic matter. In combination with an inert metal composite catalyst, the activation energy of the reaction can be reduced, making the reaction easier to proceed. It can significantly improve the activity of the iron-carbon micro-electrolysis reaction while providing more active sites, which has better degradation efficiency for difficult-to-degrade organic matter, improves its biochemical properties, and is more conducive to subsequent Fenton oxidation treatment.

[0014] Optionally, the porous polyester matrix is ​​prepared by the following method: The polyester waste is heated and melted, mixed with polyvinyl alcohol and then hot-pressed to form, and then cut after cooling to obtain polyester microspheres. The polyester microspheres are then washed with water to remove the polyvinyl alcohol, and then dried to obtain a porous polyester matrix.

[0015] By adopting the above technical scheme, the present application uses waste materials of production scraps such as polyester fibers or polyester films as polyester raw materials, polyvinyl alcohol as a template, and obtains polyester microspheres after hot pressing and cooling. The polyester microspheres are washed with water to remove the polyvinyl alcohol template, and the porous polyester matrix obtained after drying contains a porous structure, which is then ultrasonically dispersed with the composite precipitate in a mixed solution of a water-soluble phenolic resin and water, so that the composite precipitate can be loaded in the pore structure of the porous polyester matrix. The addition of the water-soluble phenolic resin plays the role of a binder, and during subsequent high-temperature calcination, the porous polyester matrix and the water-soluble phenolic resin will be carbonized to form a porous carbon skeleton, thereby achieving the loading of the composite precipitate, forming a composite structure in which the carbon skeleton is loaded with nano-palladium or nano-platinum and nano-iron, thereby achieving a better catalytic pretreatment effect.

[0016] Optionally, the platinum salt is selected from one or more of chloroplatinic acid, platinum nitrate, and platinum sulfate; The palladium salt is selected from palladium nitrate; the iron salt is selected from one or more of ferric chloride, ferric nitrate and ferric sulfate.

[0017] Optionally, in the inert metal composite catalyst, the added mass ratio of the inert metal salt to the iron salt in step 1) is 1:(0.6-0.8); The amount of sodium hydroxide added in step 2) is 20-30wt% of the amount of the inert metal salt added; In step 4), the addition amount of the composite precipitate to the porous polyester matrix is ​​1:(1-1.2), the addition amount of the water-soluble phenolic resin is 10-20wt% of the porous polyester matrix, and the addition amount of water is 4-5 times the mass of the composite precipitate.

[0018] Optionally, in the preparation of the porous polyester matrix, the mass ratio of polyester waste to polyvinyl alcohol added is 1:(0.2-0.4).

[0019] By adopting the above technical solution and selecting the above addition ratio, the water treatment effect of the inert metal composite catalyst is better.

[0020] Optionally, in step S1, the inert metal composite catalyst and titanium dioxide are mixed in a mass ratio of 1:(0.1-0.2) and then loaded on a porous titanium plate through an adhesive and then added.

[0021] By adopting the above technical scheme, when the inert metal composite catalyst is mixed with titanium dioxide and then loaded on a porous titanium plate, when water flows through, under the coordinated action of the inert metal composite catalyst and titanium dioxide, the titanium dioxide in the titanium dioxide has photocatalytic activity, and its photocatalysis is used to break the chain of difficult-to-degrade large molecular organic matter, degrade it, and convert it into smaller and easy-to-handle molecules. The catalytic effect of the inert metal in the inert metal composite catalyst helps to reduce the activation energy of the above reaction, making it easier to occur, and the iron-carbon micro-electrolysis effect cooperates with the chain breaking to reduce it, which has a better effect on water treatment.

[0022] Optionally, the concentration of the inert metal composite catalyst in step S1 is 150-200 mg / L; In step S2, the molar ratio of hydrogen peroxide to ferrous salt is 1:1, and the concentration of ferrous salt is 80-150 mg / L.

[0023] Optionally, the processing method comprises the following steps: S1. After adjusting the pH of the wastewater to 3-4, an inert metal composite catalyst is added for pretreatment to break the chain of the refractory organic matter; S2, adding ferrous salt to the wastewater pretreated in step S1, and then adding hydrogen peroxide solution to perform Fenton oxidation treatment for 10-20 minutes; S3, the wastewater treated in step S2 is aerated by passing air and reacting for 1-2 hours; S4. After aeration treatment, the pH of the sewage is adjusted to 7-8, and then flocculants are added for coagulation and sedimentation before discharge.

[0024] By adopting the above technical solution, it is usually necessary to first add ferrous salt to fully mix it with the wastewater, and then slowly add hydrogen peroxide. This can ensure that the hydrogen peroxide reacts instantly with a large amount of divalent iron to avoid self-consumption of hydrogen peroxide.

[0025] In the second aspect, the present application provides a multi-stage advanced oxidation treatment system, which adopts the following technical solution: a multi-stage advanced oxidation treatment system, comprising the following steps: including a pretreatment unit, an advanced oxidation unit, an aeration unit and a coagulation and sedimentation unit connected in sequence along the wastewater flow direction.

[0026] By adopting the above technical scheme, when the water treatment system in the present application is used for treatment, the wastewater first enters the pretreatment unit for pretreatment to improve the biodegradability of the wastewater, and then enters the advanced oxidation unit for Fenton oxidation treatment to generate hydroxyl free radicals, oxidatively decompose organic pollutants in the wastewater, and then enters the aeration unit to continue the full reaction of the unreacted reagents and finally perform coagulation and precipitation.

[0027] In summary, this application has the following beneficial effects: 1. In the present application, the wastewater is first adjusted to an acidic condition, and then an inert metal composite catalyst is added for pretreatment to break the chain of the refractory organic matter, thereby improving the biodegradability of the wastewater and improving the efficiency of the subsequent addition of ferrous salt and hydrogen peroxide solution for Fenton advanced oxidation. Then, ferrous salt and hydrogen peroxide solution are added to generate hydroxyl radicals to oxidatively decompose the organic pollutants in the wastewater, thereby greatly reducing COD. At the same time, due to the oxidative decomposition of organic matter, the chromaticity is also significantly improved. Then, the wastewater after the advanced oxidation is completed is aerated, and the Fenton reagent that has not completed the reaction continues to fully react, and further The oxidation and decomposition of residual organic matter after the Fenton reaction is promoted, thereby further reducing COD and chromaticity. Then, the pH of the aerated sewage is adjusted back to help terminate the Fenton reaction and stabilize the properties of the wastewater. Then, a flocculant is added for coagulation and sedimentation to promote the aggregation of suspended matter and colloidal substances in the wastewater into larger particles, which are convenient for removal by coagulation and sedimentation, thereby further reducing the chromaticity. Finally, in this application, different types of advanced oxidation reactions are performed in stages, thereby improving the treatment effect and reducing the treatment cost. The treated wastewater has a lower COD value and chromaticity. The method provided in this application has a better effect on COD removal. 2. The inert metal catalyst prepared in the present application can activate the difficult-to-degrade organic molecules in the wastewater by providing active sites under acidic conditions. These active sites can reduce the activation energy required for the breakage reaction of the organic molecules and increase the activation energy, thereby accelerating the reaction rate. At the same time, the good chemical stability of the inert metal ensures the long-term catalytic activity of the catalyst in an acidic environment. Through chain scission reactions, large molecular organic matter is decomposed into small molecular fragments that are more easily degraded by microorganisms, thereby significantly improving the biodegradability of the wastewater. This treatment method creates more favorable conditions for subsequent biochemical treatment steps and improves the efficiency and effect of the entire wastewater treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of the structure of the processing system in Example 1 of the present application; Figure 2 is a schematic diagram of the structure of the pre-processing unit in Example 1 of the present application; In the figure, 1. high-efficiency mixer; 2. pretreatment unit; 3. advanced oxidation unit; 4. aeration unit; 5. coagulation and sedimentation unit; 6. water inlet pipe; 7. water outlet pipe. DETAILED DESCRIPTION

[0029] The present application is further described in detail below in conjunction with the examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0030] The titanium dioxide in the following examples is rutile titanium dioxide; The platinum-palladium catalyst is a platinum-palladium catalyst from Jiangxi Huihua Technology Co., Ltd., with a CAS number of 1344; The adhesive in the following preparation example is epoxy adhesive with brand E-128 from Bezos Polymer New Materials (Dongguan) Co., Ltd.; the water-soluble phenolic resin is water-soluble phenolic resin with CAS number 9003-35-4 from Shandong Lingchuang Biotechnology Co., Ltd.

[0031] The following preparation examples are preparation examples of inert metal composite catalysts: Preparation Example 1 A method for preparing an inert metal composite catalyst comprises the following steps: 1) dissolving an inert metal salt chloroplatinic acid and an iron salt ferric chloride in water, stirring and mixing to obtain a metal salt solution, wherein the added mass ratio of chloroplatinic acid to ferric chloride is 1:0.7, and the added amount of water is 4 times the mass of chloroplatinic acid; 2) adding the prepared metal salt solution dropwise to a sodium hydroxide solution to precipitate the metal ions to form a composite precipitate, wherein the amount of sodium hydroxide added is 25 wt% of the amount of the inert metal salt added; 3) The filter cake obtained by filtration is a composite precipitate, and then the composite precipitate is treated at a constant temperature of 300°C for 1.5h, and then washed with water and dried; 4) The composite precipitate treated in step 3) is mixed with a porous polyester matrix in a mass ratio of 1:1.1, and then mixed with a water-soluble phenolic resin and water, and ultrasonically dispersed at 50° C. for 25 minutes to obtain a mixture, wherein the amount of the water-soluble phenolic resin added is 15wt% of the porous polyester matrix, and the amount of water added is 4.5 times the mass of the composite precipitate; 5) The filter cake obtained after filtering the obtained mixture was calcined in a hydrogen atmosphere at a calcination temperature of 710° C. for 2.5 h to obtain an inert metal composite catalyst.

[0032] Wherein, the porous polyester matrix in step 4) is prepared by the following method: The polyester waste is heated and melted, mixed with polyvinyl alcohol in a mass ratio of 1:0.3, and then hot-pressed. The mixture is then cooled and cut to obtain polyester microspheres. The polyester microspheres are then rinsed with water to remove the polyvinyl alcohol, and then dried to obtain a porous polyester matrix, wherein the polyester waste is leftover material from the production process of polyester fibers and polyester films.

[0033] Preparation Example 2 A method for preparing an inert metal composite catalyst comprises the following steps: 1) dissolving an inert metal salt chloroplatinic acid and an iron salt ferric chloride in water, stirring and mixing to obtain a metal salt solution, wherein the added mass ratio of chloroplatinic acid to ferric chloride is 1:0.6, and the added amount of water is 3 times the mass of chloroplatinic acid; 2) adding the prepared metal salt solution dropwise to a sodium hydroxide solution to precipitate the metal ions to form a composite precipitate, wherein the amount of sodium hydroxide added is 20 wt% of the amount of the inert metal salt added; 3) The filter cake obtained by filtration is a composite precipitate, and then the composite precipitate is treated at a constant temperature of 280°C for 2 hours, and then washed with water and dried; 4) The composite precipitate treated in step 3) is mixed with a porous polyester matrix in a mass ratio of 1:1, and then mixed with a water-soluble phenolic resin and water, and ultrasonically dispersed at 45° C. for 30 minutes to obtain a mixture, wherein the amount of the water-soluble phenolic resin added is 10wt% of the porous polyester matrix, and the amount of water added is 4 times the mass of the composite precipitate; 5) The filter cake obtained after filtering the obtained mixture was calcined in a hydrogen atmosphere at a calcination temperature of 680° C. for 3 h to obtain an inert metal composite catalyst.

[0034] Wherein, the porous polyester matrix in step 4) is prepared by the following method: The polyester waste is heated and melted, mixed with polyvinyl alcohol in a mass ratio of 1:0.2, and then hot-pressed. The mixture is then cooled and cut to obtain polyester microspheres. The polyester microspheres are then rinsed with water to remove the polyvinyl alcohol, and dried to obtain a porous polyester matrix, wherein the polyester waste is leftover material from the production process of polyester fibers and polyester films.

[0035] Preparation Example 3 A method for preparing an inert metal composite catalyst comprises the following steps: 1) dissolving an inert metal salt of palladium nitrate and an iron salt of ferric chloride in water, stirring and mixing to obtain a metal salt solution, wherein the mass ratio of palladium nitrate to ferric chloride is 1:0.8, and the amount of water added is 5 times the mass of palladium nitrate; 2) adding the prepared metal salt solution dropwise to a sodium hydroxide solution to precipitate the metal ions to form a composite precipitate, wherein the amount of sodium hydroxide added is 30 wt% of the amount of the inert metal salt added; 3) The filter cake obtained by filtration is a composite precipitate, and then the composite precipitate is treated at a constant temperature of 320°C for 1 hour, and then washed with water and dried; 4) The composite precipitate treated in step 3) is mixed with a porous polyester matrix in a mass ratio of 1:1.2, and then mixed with a water-soluble phenolic resin and water, and ultrasonically dispersed at 55° C. for 20 minutes to obtain a mixture, wherein the amount of the water-soluble phenolic resin added is 20wt% of the porous polyester matrix, and the amount of water added is 5 times the mass of the composite precipitate; 5) The filter cake obtained after filtering the obtained mixture is calcined in a hydrogen atmosphere at a calcination temperature of 750° C. for 2 h to obtain an inert metal composite catalyst.

[0036] Wherein, the porous polyester matrix in step 4) is prepared by the following method: The polyester waste is heated and melted, mixed with polyvinyl alcohol in a mass ratio of 1:0.4, and then hot-pressed. The mixture is then cooled and cut to obtain polyester microspheres. The polyester microspheres are then rinsed with water to remove the polyvinyl alcohol, and then dried to obtain a porous polyester matrix, wherein the polyester waste is leftover material from the production process of polyester fibers and polyester films.

[0037] Preparation Example 4 A method for preparing an inert metal composite catalyst is carried out according to the method in Preparation Example 1, except that in step 1), an equal amount of iron salt is replaced by an inert metal salt.

[0038] Preparation Example 5 A method for preparing an inert metal composite catalyst is carried out according to the method in Preparation Example 1, except that no water-soluble phenolic resin is added in step 4).

[0039] Preparation Example 6 A method for preparing an inert metal composite catalyst is carried out according to the method in Preparation Example 1, except that in step 3), after washing and drying, step 5) is directly carried out without step 4).

[0040] Example 1 A multi-stage advanced oxidation treatment system, such as Figure 1 As shown, it includes a high-efficiency mixer 1, a pretreatment unit 2, an advanced oxidation unit 3, an aeration unit 4 and a coagulation and sedimentation unit 5 which are arranged in sequence along the flow direction of the wastewater, wherein the high-efficiency mixer 1 is connected to a water inlet pipe 6, the coagulation and sedimentation unit 5 is connected to a water outlet pipe 7, the advanced oxidation unit 3 is provided with a ferrous salt dosing pipe and a hydrogen peroxide dosing pipe, an aeration pipe is provided at the bottom of the aeration unit 4, the aeration pipe is connected to an air source, and aeration holes are opened on the aeration pipe. In this application, the air source is air.

[0041] This embodiment also discloses a multi-stage advanced oxidation treatment method, which is implemented by the multi-stage advanced oxidation treatment system, and includes the following steps: S1, the wastewater first enters the high-efficiency mixer 1 through the water inlet pipe 6, and acid is added to adjust the pH value of the wastewater to 3, and then the wastewater enters the pretreatment unit 2, the inert metal composite catalyst prepared in Preparation Example 1 is directly added to the pretreatment unit 2 and pretreated for 40 minutes under stirring conditions to break the chain of the refractory organic matter, and the concentration of the inert metal composite catalyst in the pretreatment unit 2 is maintained at 180 mg / L; S2, after the wastewater pretreated in step S1 enters the advanced oxidation unit 3, firstly, ferrous salt is added through the ferrous salt dosing pipe, and then hydrogen peroxide solution is added through the hydrogen peroxide dosing pipe, and Fenton oxidation treatment is performed for 15 minutes, wherein the molar ratio of hydrogen peroxide to ferrous salt is 1:1, and the concentration of ferrous salt is 100 mg / L; S3, the wastewater treated in step S2 enters the aeration unit 4 and is aerated with air for 1.5 hours; S4, the pH value of the sewage after aeration treatment is adjusted to 7, and then enters the coagulation and sedimentation unit 5, and after adding flocculants for coagulation and sedimentation, the water is discharged through the outlet pipe 7, wherein the flocculants are polyaluminium chloride.

[0042] Example 2 A multi-stage advanced oxidation treatment method comprises the following steps: S1, the wastewater first enters the high-efficiency mixer 1 and adds acid to adjust the pH value of the wastewater to 3, and then the wastewater enters the pretreatment unit 2, the inert metal composite catalyst prepared in Preparation Example 2 is directly added into the pretreatment unit 2 and pretreated for 30 minutes under stirring conditions to break the chain of the refractory organic matter, and the concentration of the inert metal composite catalyst in the pretreatment unit 2 is maintained at 150 mg / L; S2, after the wastewater pretreated in step S1 enters the advanced oxidation unit 3, firstly, ferrous salt is added through the ferrous salt dosing pipe, and then hydrogen peroxide solution is added through the hydrogen peroxide dosing pipe, and Fenton oxidation treatment is performed for 10 minutes, wherein the molar ratio of hydrogen peroxide to ferrous salt is 1:1, and the concentration of ferrous salt is 80 mg / L; S3, the wastewater treated in step S2 enters the aeration unit 4 and is aerated with air for 1 hour; S4, the pH value of the sewage after aeration treatment is adjusted to 7, and then enters the coagulation and sedimentation unit 5, and after adding flocculants for coagulation and sedimentation, the water is discharged through the outlet pipe 7, wherein the flocculants are polyaluminium chloride.

[0043] Example 3 A multi-stage advanced oxidation treatment method comprises the following steps: S1, the wastewater first enters the high-efficiency mixer 1 and adds acid to adjust the pH value of the wastewater to 4, and then the wastewater enters the pretreatment unit 2, the inert metal composite catalyst prepared in Preparation Example 3 is directly added into the pretreatment unit 2 and pretreated for 50 minutes under stirring conditions to break the chain of the refractory organic matter, and the concentration of the inert metal composite catalyst in the pretreatment unit 2 is maintained at 200 mg / L; S2, after the wastewater pretreated in step S1 enters the advanced oxidation unit 3, firstly, ferrous salt is added through the ferrous salt dosing pipe, and then hydrogen peroxide solution is added through the hydrogen peroxide dosing pipe, and Fenton oxidation treatment is performed for 20 minutes, wherein the molar ratio of hydrogen peroxide to ferrous salt is 1:1, and the concentration of ferrous salt is 150 mg / L; S3, the wastewater treated in step S2 enters the aeration unit 4 and is aerated with air for 2 hours; S4, the pH value of the sewage after aeration treatment is adjusted to 8, and then enters the coagulation and sedimentation unit 5, and after adding flocculants for coagulation and sedimentation, the water is discharged through the outlet pipe 7, wherein the flocculant is polyaluminium chloride.

[0044] Embodiment 4-6 A multi-stage advanced oxidation treatment method is carried out according to the method in Example 1, except that the inert metal composite catalyst in step S1 is the inert metal composite catalyst prepared in Preparation Examples 4-6.

[0045] Example 7 A multi-stage advanced oxidation treatment method is carried out according to the method in Example 1, except that in step S1, the inert metal composite catalyst and titanium dioxide are mixed in a mass ratio of 1:0.1 and then loaded on a porous titanium plate through an adhesive, and then the porous titanium plate is placed in a pretreatment unit 2, and the height of the porous titanium plate is higher than the water inlet of the pretreatment unit 2, and the pretreatment unit 2 adopts a bottom-in and top-out method, so that the wastewater comes into contact with the inert metal composite catalyst and titanium dioxide on the porous titanium plate after entering.

[0046] Example 8 A multi-stage advanced oxidation treatment method is carried out according to the method in Example 1, except that in step S1, an inert metal composite catalyst and titanium dioxide are mixed in a mass ratio of 1:0.2 and loaded on a porous titanium plate through an adhesive, and then the porous titanium plate is placed in a pretreatment unit 2, and the height of the porous titanium plate is higher than the water inlet of the pretreatment unit 2, and the wastewater in the pretreatment unit 2 is in a bottom-in and top-out manner, so that the wastewater comes into contact with the inert metal composite catalyst and titanium dioxide on the porous titanium plate after entering.

[0047] Example 9 A multi-stage advanced oxidation treatment method is carried out according to the method in Example 1, except that the inert metal composite catalyst in step S1 is replaced by an equal amount of platinum-palladium catalyst.

[0048] Comparative Example 1 A multi-stage advanced oxidation treatment method is carried out according to the method in Example 1, except that after the pH of the wastewater in step S1 is adjusted, the wastewater is directly subjected to step S2 operation and enters the Fenton advanced oxidation unit 3 for Fenton oxidation treatment.

[0049] Comparative Example 2 A multi-stage advanced oxidation treatment method is carried out according to the method in Example 1, except that after 105 minutes of Fenton oxidation treatment in step S2, step S4 treatment is directly carried out, and the coagulation and sedimentation unit 5 is entered for treatment, and the aeration treatment in step S3 is not carried out.

[0050] Performance Testing In the present application, the methods in the above-mentioned embodiments and comparative examples are used to treat a certain aquaculture wastewater tail water as the wastewater to be treated. The COD value of the wastewater to be treated is 150 mg / L, and the chromaticity is 120 degrees (Pt-Co). The effluent after the above-mentioned wastewater treatment is tested, and the test results are shown in Table 1 below.

[0051] Table 1: Referring to the test results in Table 1 above, the wastewater is treated by the method provided in the present application, and the COD value and chromaticity of the wastewater after treatment are significantly reduced. Combining the test results of Example 1 and Comparative Example 1, when the wastewater in Comparative Example 1 does not enter the pretreatment tank for pretreatment, the COD value and chromaticity of the final wastewater are high, and the treatment effect is limited by relying only on Fenton oxidation treatment. When direct Fenton oxidation treatment is performed in Comparative Example 2 without aeration treatment, it can be seen that its treatment effect is also significantly reduced, and the use of multi-stage oxidation treatment has a better treatment effect on wastewater. Combined with the test results of Example 1 and Example 9, when the catalyst in the pretreatment unit of Example 9 uses an ordinary platinum-palladium catalyst, its treatment effect is significantly reduced.

[0052] Combining the test results of Example 1 and Example 4, when only platinum is added to the inert metal composite catalyst in Example 4 without adding iron salt, the final treatment effect is also significantly reduced. Combining the test results of Example 5 and Example 6, when the metal composite obtained by precipitation treatment is not subjected to carbon-based coating and other treatments, its water treatment effect is also significantly reduced.

[0053] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A multi-stage advanced oxidation treatment method, characterized in that: The following steps are involved: S1. After adjusting the pH of the wastewater to acidic, an inert metal composite catalyst is added for pretreatment to break the chain of the refractory organic matter; S2, adding ferrous salt and hydrogen peroxide solution to the wastewater pretreated in step S1 to perform Fenton oxidation treatment; S3, aeration treatment of the wastewater after treatment in step S2; S4. The pH of the sewage after aeration treatment is adjusted to neutral or alkaline, and then flocculants are added for coagulation and sedimentation before discharge.

2. A multi-stage advanced oxidation treatment method according to claim 1, characterized in that: In step S1, the pH value of the wastewater is adjusted to 3-4.

3. A multi-stage advanced oxidation treatment method according to claim 1, characterized in that: In step S1, the inert metal composite catalyst is prepared by coprecipitating an inert metal salt and an iron salt to obtain a composite precipitate, which is then mixed with a phenolic resin and a porous polyester matrix after aging and then calcined in a hydrogen atmosphere, wherein the inert metal salt is selected from one or both of platinum salt and palladium salt.

4. A multi-stage advanced oxidation treatment method according to claim 1, characterized in that: The inert metal composite catalyst in step S1 is prepared by the following method: 1) Dissolve the inert metal salt and iron salt in water, stir and mix to obtain a metal salt solution; 2) adding the prepared metal salt solution dropwise into the sodium hydroxide solution to precipitate the metal ions to form a composite precipitate; 3) The composite precipitate is filtered and treated at a constant temperature of 280-320°C for 1-2 hours, then washed with water and dried; 4) Mixing the composite precipitate treated in step 3) with a porous polyester matrix, and then mixing with a water-soluble phenolic resin and water, and preparing a mixture after ultrasonic dispersion at 45-55° C. for 20-30 minutes; 5) After filtering the obtained mixture, calcining it in a hydrogen atmosphere at a calcination temperature of 680-750° C. for 2-3 hours to obtain an inert metal composite catalyst.

5. A multi-stage advanced oxidation treatment method according to claim 4, characterized in that: The porous polyester matrix was prepared by the following method: The polyester waste is heated and melted, mixed with polyvinyl alcohol and then hot-pressed, and then cooled and cut to obtain polyester microspheres. The polyester microspheres are then rinsed with water to remove the polyvinyl alcohol, and then dried to obtain a porous polyester matrix, wherein the added mass ratio of polyester waste to polyvinyl alcohol is 1: (0.2-0.4).

6. A multi-stage advanced oxidation treatment method according to claim 4, characterized in that: The platinum salt is selected from one or more of chloroplatinic acid, platinum nitrate, and platinum sulfate; The palladium salt is selected from palladium nitrate; the iron salt is selected from one or more of ferric chloride, ferric nitrate and ferric sulfate.

7. A multi-stage advanced oxidation treatment method according to claim 4, characterized in that: In the inert metal composite catalyst, the added mass ratio of the inert metal salt to the iron salt in step 1) is 1:(0.6-0.8); The amount of sodium hydroxide added in step 2) is 20-30wt% of the amount of the inert metal salt added; In step 4), the addition ratio of the composite precipitate to the porous polyester matrix is ​​1:(1-1.2), the addition amount of the water-soluble phenolic resin is 10-20wt% of the porous polyester matrix, and the addition amount of water is 4-5 times the mass of the composite precipitate.

8. A multi-stage advanced oxidation treatment method according to claim 1, characterized in that: The concentration of the inert metal composite catalyst in step S1 is 150-200 mg / L; In step S2, the molar ratio of hydrogen peroxide to ferrous salt is 1:1, and the concentration of ferrous salt is 80-150 mg / L.

9. A multi-stage advanced oxidation treatment method according to claim 1, characterized in that: The processing method comprises the following steps: S1. After adjusting the pH of the wastewater to 3-4, an inert metal composite catalyst is added for pretreatment to break the chain of the refractory organic matter; S2, adding ferrous salt to the wastewater pretreated in step S1, and then adding hydrogen peroxide solution to perform Fenton oxidation treatment for 10-20 minutes; S3, the wastewater treated in step S2 is aerated by passing air and reacting for 1-2 hours; S4. After aeration treatment, the pH of the sewage is adjusted to 7-8, and then flocculants are added for coagulation and sedimentation before discharge.

10. A multi-stage advanced oxidation treatment system for implementing a multi-stage advanced oxidation treatment method, characterized in that: It comprises a pretreatment unit (2), an advanced oxidation unit (3), an aeration unit (4) and a coagulation and sedimentation unit (5) which are sequentially connected along the flow direction of the wastewater.

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