Method for preparing catalyst based on Fenton iron sludge and activated sludge, prepared catalyst and application

Abstract

The invention relates to the field of water treatment, and particularly discloses a method for preparing a catalyst based on Fenton iron sludge and activated sludge, the prepared catalyst and application, the method comprises the following steps: S1, crushing and sieving Fenton iron sludge, activated sludge and a binder; s2, mixing the sieved Fenton iron mud, activated sludge and binder with a pore-forming agent and carbon powder, and then adding a transition metal salt solution to prepare a primary mixture; s3, the primary mixture is dried after being formed, a blank is formed and then subjected to pyrolysis treatment, and the catalyst is prepared; the invention also discloses the catalyst prepared by the method and application of the catalyst in water treatment. According to the application, resource utilization of the Fenton iron sludge and the activated sludge is realized, the problem of enrichment of organic matters and heavy metals in wastewater in a current Fenton iron sludge resource technology is solved, the prepared catalyst can be used for catalyzing ozone, hydrogen peroxide or persulfate to degrade the organic matters in the wastewater, and the preparation method of the catalyst is simple.

Description

Technical Field

[0001] The present application relates to the field of water treatment, and more specifically, to a method for preparing a catalyst based on Fenton iron sludge and activated sludge, the obtained catalyst and its application. Background Art

[0002] The Fenton oxidation technology is commonly used for the treatment of refractory organic wastewater. Its basic principle is to generate strongly oxidizing hydroxyl radicals through the reaction of Fe 2+ and H2O2 under acidic conditions, and mineralize the organic matter into CO2 and H2O. After the reaction, it is necessary to add alkali to adjust the pH to neutral or alkaline to convert the generated ferric ions into iron hydroxide, and add a flocculant to remove it by precipitation or flotation. This method has a high removal efficiency for refractory organic matter, but the iron sludge contains a large amount of organic matter and heavy metals, which belongs to hazardous waste and needs to be treated secondary, such as incineration, landfill or cement solidification, etc. This not only significantly increases the treatment cost, but also causes long-term waste of iron resources. Therefore, developing an efficient resource recovery and utilization technology for Fenton iron sludge is of great significance for promoting the Fenton technology.

[0003] For example, Chinese Patent with the application publication number CN110877956A discloses a device and method for treating Fenton iron sludge. This method reduces ferric iron in the iron sludge to ferrous iron by iron-reducing bacteria and then adds acid solution. After solid-liquid separation, the acid solution rich in ferrous iron can be recycled to the Fenton reactor. This method can effectively reduce the consumption of ferrous iron salts. However, this method will cause the concentration of heavy metals, aluminum and organic matter in the recovered ferrous iron acid solution to continuously enrich, ultimately affecting the Fenton reaction effect and the biological activity of iron-reducing bacteria.

[0004] Chinese Patent with the application publication number CN105836987A discloses a method for the resource utilization of Fenton iron sludge. This method first adds sulfuric acid to the iron sludge to completely convert the iron hydroxide in the iron sludge into ferric sulfate solution. Subsequently, after diluting the solution, it is introduced into the anode chamber of the diaphragm electrolytic cell for electro-oxidation to remove organic matter, and then introduced into the cathode chamber for electro-reduction to reduce ferric iron to ferrous iron ions. After the reaction, industrial-grade ferrous sulfate is obtained by concentrating and crystallizing under the protection of inert gas. However, this method has a limited removal rate of heavy metals, affecting the quality of ferrous sulfate products, and the two-step electrolysis method consumes too much electric energy.

[0005] Chinese Patent with the authorization announcement number CN102849803B discloses a method for the recycling of Fenton reaction catalysts. This method adds concentrated sulfuric acid to the iron sludge after centrifugal dehydration and controls [SO4 2- / [Fe] tThe ratio is within 1.15 - 1.35 to enable full polymerization reaction. Subsequently, deionized water is added under stirring, and the pH is adjusted to be between 1.0 - 1.5 to obtain a polymeric ferric sulfate solution that can be recycled for the flocculation process. However, this method still fails to solve the problems of organic matter and heavy metal accumulation.

[0006] Chinese Patent with the publication number CN106810204A discloses a Fenton iron sludge integrated anode and cathode ceramsite and a method for preparing ceramsite using Fenton iron sludge. In this method, Fenton iron sludge, clay, fly ash, and a pelletizing agent are mixed in a certain ratio and then pelletized. After drying at room temperature, it is sintered at 600 °C to prepare the Fenton iron sludge integrated anode and cathode ceramsite, which can be used for micro-electrolysis treatment of organic matter and also as a filler for biological filters and sulfurization reaction beds. However, when the ceramsite prepared by this method is used for iron-carbon micro-electrolysis treatment of wastewater, the iron dissolution rate is fast, the service life is short, and it is easy to cause the packing to cake.

[0007] It can be seen that although there are now multiple records on the resource recovery of Fenton iron sludge, they all have different degrees of defects, such as the accumulation of heavy metals and organic matter, difficult control of preparation conditions, short service life of preparation materials, etc. There is a need to provide new means of resource recovery and utilization to solve the problem of the enrichment of organic matter and heavy metals in wastewater in the existing resource utilization technologies, improve the service life of the prepared catalyst, and simplify the preparation process. Summary of the Invention

[0008] To achieve the resource recovery and utilization of Fenton iron sludge and activated sludge, solve the problem of the enrichment of organic matter and heavy metals in wastewater in the current Fenton iron sludge resource recovery technology, improve the service life of the prepared catalyst, and simplify the preparation process, this application provides a method for preparing a catalyst based on Fenton iron sludge and activated sludge and its application.

[0009] In the first aspect, this application provides a method for preparing a catalyst based on Fenton iron sludge and activated sludge, adopting the following technical scheme: A method for preparing a catalyst based on Fenton iron sludge and activated sludge includes the following steps: S1. Crush Fenton iron sludge, activated sludge, and binder and then screen them. S2. Mix the screened Fenton iron sludge, activated sludge, binder with a pore-forming agent and carbon powder to form a mixed material, and then add a transition metal salt solution to obtain a preliminary mixture. S3. Shape the preliminary mixture and then dry it to form a blank, and then perform pyrolysis treatment to obtain the catalyst.

[0010] By adopting the above technical scheme, the catalyst in the present application uses Fenton iron mud and activated sludge as substrates, and the microorganisms in the activated sludge and Fenton iron mud undergo pyrolysis and carbonization reactions under anaerobic and high-temperature conditions to generate biochar or graphitized carbon with high porosity and excellent adsorption properties; the trivalent iron in the Fenton iron mud first forms Fe2O3 during the pyrolysis process, and then is partially reduced to FeO and a small amount of elemental iron using carbon powder as a reducing agent; the pore-forming agent decomposes or volatilizes at high temperature to form microporous and mesoporous structures; the added transition metal salt forms the corresponding metal oxide after pyrolysis treatment, which is uniformly distributed on the catalyst surface and the loading sites inside the pores, and synergistically acts with the iron oxide and the metal oxide formed by the heavy metals in the Fenton iron mud and activated sludge, and can catalyze hydrogen peroxide, ozone and persulfate to generate strong oxidizing substances in a wide pH range to degrade organic matter in wastewater.

[0011] The method of the present application realizes the resource utilization of Fenton iron mud and activated sludge without secondary pollution. The catalyst prepared in the present application has a large specific surface area, which is beneficial to the diffusion and adsorption of oxidants and organic molecules such as ozone, persulfate and hydrogen peroxide inside the catalyst during wastewater treatment, thereby improving the catalytic reaction effect and efficiency. It can also be used as a particle electrode in the electrocatalytic oxidation process to produce a Fenton-like reaction.

[0012] Optionally, the binder is one or more of clay, kaolin, attapulgite and bentonite.

[0013] Optionally, the pore-forming agent is one or more of polyvinyl pyrrolidone, polyethylene glycol, polymethyl methacrylate, ammonium bicarbonate and starch.

[0014] By adopting the above technical scheme, the binder in this application uses the above-mentioned clay mineral, whose main component is aluminosilicate, which has excellent adhesion and mechanical properties. After mixing with the transition metal salt solution, it has certain adhesion properties to bond the primary mixture, forming a stable ceramic phase at high temperature, presenting a porous structure, and improving the mechanical strength, specific surface area, stability and service life of the catalyst.

[0015] The pore-forming agent selected in the present application can form micropores and mesoporous structures during the catalyst preparation process, increase the specific surface area of ​​the catalyst, expose more active sites of the catalyst, and improve the catalytic activity of the catalyst.

[0016] Optionally, the transition metal salt solution is one or more of chlorides, sulfates, nitrates and acetates of manganese, nickel, cerium, copper, cobalt and molybdenum metals, and the concentration of the transition metal salt in the transition metal salt solution is 0.01-0.50 mol / L.

[0017] By adopting the above technical solution, the addition of the transition metal salt solution can ensure the uniformity and concentration of metal substances in the catalyst. The generated transition metal oxides can act as a catalyst together with iron oxides, strengthening the degradation of organic substances, reducing the dissolution rate of iron oxides, and increasing the service life of the catalyst. When the above transition metal ions are used in the catalytic oxidation degradation of organic substances in wastewater, they promote the generation of strongly oxidizing substances such as hydroxyl radicals, thereby accelerating the degradation of organic substances, or participating in electron transfer reactions during the catalytic process, reducing the reaction activation energy, playing a catalytic role, and improving the treatment effect and efficiency.

[0018] Optionally, the carbon powder is activated carbon powder or fly ash. In a more preferred case, the activated carbon powder is waste activated carbon powder to be regenerated for water treatment.

[0019] By adopting the above technical solution, on the one hand, the added carbon powder in the present application can adjust the valence state of metal oxides generated during the pyrolysis process, thereby regulating the active components of the catalyst. On the other hand, it is beneficial to form a porous structure during the pyrolysis process of the catalyst, and can also assist in dispersing metal oxide particles, regulating the mechanical strength, thermal stability and conductivity of the catalyst, and reducing the preparation cost of the catalyst.

[0020] Optionally, in step S2, the mass ratio of the addition of activated sludge, Fenton iron sludge, carbon powder, pore-forming agent and binder is (10 - 70):10:(0.5 - 3):(0.05 - 1):(20 - 50).

[0021] Optionally, the mass ratio of the addition of the transition metal salt solution to the mixed material is (8 - 12):10.

[0022] By adopting the above technical solution, when the above addition amounts are used, the structural stability of the catalyst particles and the concentration of iron oxides in the catalyst are ensured, and the catalytic effect of the finally prepared catalyst is better.

[0023] Optionally, in step S3, the pyrolysis temperature of the pyrolysis treatment is 620 - 800 °C, and the pyrolysis time is 2 - 3 h.

[0024] By adopting the above technical solution, when the above pyrolysis parameters are used, it is helpful for iron hydroxide and metal salts to form corresponding metal oxides.

[0025] Optionally, in step S3, during the pyrolysis treatment, the atmosphere is a low-oxygen environment, and the pyrolysis atmosphere is oxygen with a volume ratio of 1:(2 - 3) and a volume fraction of 3 - 5% and the balance being an inert gas.

[0026] By adopting the above technical solution, when the above-mentioned atmosphere pyrolysis treatment is carried out, ferric hydroxide and metal salts in the iron sludge can be converted into corresponding metal oxides. And under the reduction of carbon powder, some metal oxides are reduced to metal oxides with lower valence states. Different metal oxides can synergistically catalyze oxidants such as ozone and hydrogen peroxide to generate more strong oxidation media, improving the degradation efficiency of organic matter.

[0027] In the final step S3, first, preliminary drying is carried out at room temperature for pretreatment, which can prevent the catalyst from breaking or cracking during the subsequent pyrolysis sintering process, affecting the structural stability. Then, the pyrolysis time, temperature, and atmosphere are controlled, which can convert the organic matter in the Fenton iron sludge and activated sludge into biochar, and can also ensure that the generated biomass carbon and carbon powder will not be over-graphitized, causing damage to the pore structure, decomposition of functional groups, or even conversion into ash.

[0028] Optionally, the specific operation of the pyrolysis treatment in step S3 is as follows: First, in a nitrogen atmosphere, the temperature is raised to 300 - 350 °C, and preliminary pyrolysis is carried out for 40 - 60 min; then the temperature is raised to 620 - 800 °C, and pyrolysis treatment is carried out for 30 - 40 min. Finally, oxygen is introduced, and it is treated for 1 - 2 h in an atmosphere where the volume fraction of oxygen is 3 - 5%, and the balance is nitrogen with a nitrogen volume ratio of 3:(7 - 8).

[0029] By adopting the above technical solution and the above pyrolysis treatment regime, first, preliminary pyrolysis is carried out to remove volatile components, and then the temperature is continuously raised for pyrolysis treatment, which helps to further stabilize and carbonize the catalyst structure, improve the catalytic activity. By regulating the atmosphere at different stages, ferric hydroxide and metal salts in the blank are converted into metal oxides, and then the reduction of carbon powder at high temperature is used to reduce some metal oxides to metal oxides with lower valence states, improving the catalytic activity.

[0030] During the preparation of the catalyst, a carbon-containing inactive substance, namely carbon deposition, will form on the surface, clogging the active sites or pores of the catalyst, reducing the effective specific surface area, and lowering the catalyst activity. In this application, the final treatment in a mixed atmosphere of oxygen and nitrogen also helps to remove the carbon deposits accumulated on the catalyst surface.

[0031] Optionally, after the pyrolysis treatment in step S3, the blank after pyrolysis treatment is post-treated. The specific operation is as follows: First, it is impregnated in a dilute acid solution, then impregnated in a polarity-improving solution, and finally impregnated in a mixed solution of ethylenediamine, PAMAM, and aminosilane, and then dried to obtain the catalyst, where the polarity-improving solution is selected as n-hexane and benzoic acid with a mass ratio of 1:(0.2 - 0.3).

[0032] By adopting the above technical solution, the blank after pyrolysis treatment is first impregnated in a dilute acid solution to remove impurities and carbon deposits on the surface of the blank and optimize the surface pore structure, and then impregnated in a polarity-improving liquid to affect the polarity of the catalyst. In this way, the polar catalyst can more easily interact with polar organic molecule, thereby enhancing the adsorption effect. This adsorption helps to enrich organic molecules on the surface of the catalyst, providing favorable conditions for subsequent oxidative degradation. Finally, it is treated in a mixed solution of aminosilane, ethylenediamine and PAMAM to introduce amino groups on the surface of the catalyst. As a nucleophilic functional group, the amino group can enhance the contact and adsorption between the catalyst and organic pollutants. By introducing amino groups, the catalyst can more effectively adsorb and degrade organic pollutants. In addition, the amino group may also promote the activation of oxidants such as hydrogen peroxide and ozone on the surface of the catalyst, thus contributing to the oxidative degradation process.

[0033] Optionally, in the post-treatment process, the dilute acid solution is a hydrochloric acid solution with a mass concentration of 5-10%. The impregnation treatment in the dilute acid solution lasts for 10-20 minutes, the impregnation time in the polarity-improving liquid is 30-40 minutes, and the impregnation pressure is 0.4-0.6 MPa. The mixed solution is prepared by mixing ethylenediamine, PAMAM, aminosilane and water in a mass ratio of 1:(0.3-0.4):(0.6-0.8):(4-6). The impregnation time is 40-60 minutes, and the impregnation temperature is 45-60 °C.

[0034] By adopting the above technical solution, the above impregnation treatment can endow the catalyst with stronger adsorption performance and catalytic performance, which helps to improve the oxidative degradation of organic matter in wastewater by oxidants.

[0035] In the second aspect, the present application provides a catalyst, adopting the following technical solution: A catalyst prepared by the method.

[0036] By adopting the above technical solution, the catalyst prepared by the method in the present application has a rich pore structure and good adsorption performance. Moreover, it is prepared based on Fenton iron sludge and activated sludge, so that the pore structure of the catalyst is loaded with rich iron oxides and other metal oxides, which can catalyze ozone, hydrogen peroxide or persulfate to generate hydroxyl radicals with extremely strong oxidation ability, and oxidize and decompose organic matter in wastewater into carbon dioxide and water, solving the problem of enrichment of organic matter and heavy metals during the treatment of Fenton iron sludge at present.

[0037] In the third aspect, the present application provides an application of a catalyst, adopting the following technical solution: An application of a catalyst in water treatment.

[0038] By adopting the above technical solutions, the method in the present application not only realizes the resource reuse of Fenton iron sludge and activated sludge, but also solves the problem of enrichment of organic matter and heavy metals in existing resource utilization technologies. The organic matter is carbonized to form biochar to construct a porous structure, and a catalyst with a porous structure is prepared. Moreover, the iron in the Fenton iron sludge, the heavy metals in the Fenton iron sludge and activated sludge, and the added transition metal salts form metal oxides after pyrolysis to synergistically enhance the efficiency and achieve efficient catalysis.

[0039] In summary, the present application has the following beneficial effects: 1. The method in the present application realizes the resource reuse of Fenton iron sludge and activated sludge, and also solves the pollution of Fenton iron sludge and activated sludge solid waste. The organic matter is carbonized to form biochar to construct a porous structure, and a catalyst with a porous structure is prepared. Moreover, the iron in the Fenton iron sludge and the added transition metal salts form metal oxides after pyrolysis, which are evenly distributed inside and on the surface of the catalyst, with good catalytic effect and long service life. 2. The catalyst prepared by the present application has good adsorption performance and can be used to efficiently catalyze ozone, hydrogen peroxide or persulfate to generate strongly oxidizing hydroxyl radicals or sulfate radicals to degrade organic matter in wastewater. Description of the Drawings

[0040] Figure 1 is the effect diagram of the catalytic ozone oxidation degradation of TOC by catalysts with different Mn contents in the method of Example 1 of the present application; Figure 2 is the effect diagram of the catalytic ozone oxidation degradation of TOC by catalysts with different Mn and Ni contents in the method of Example 4 of the present application; Figure 3 is the effect diagram of the catalytic ozone oxidation degradation of TOC by catalysts with different Cu contents in the method of Example 5 of the present application; Figure 4 is the effect diagram after the Mn(0.20mol / L)-Ni(0.20 mol / L) catalyst in the method of Example 4 of the present application is recycled multiple times; Figure 5 is the crystallization state diagram of the catalyst prepared in Example 5 of the present application detected by XRD. Detailed Embodiments

[0041] The following further describes the present application in detail with reference to embodiments. It should be specifically noted that: for those not specifying specific conditions in the following embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. Except for special instructions, the raw materials used in the following embodiments can all be obtained from ordinary commercial sources.

[0042] In this application, the blank material after the initial mixture is formed in method step S3 can be spherical or columnar particles. When it is columnar particles, its length is 3 - 10 mm.

[0043] In the following examples, the activated sludge is the activated sludge concentrated in the secondary sedimentation tank of the biochemical treatment process. The organic matter content in the activated sludge is 29.6%, the microorganism content is 35.8%, and the rest are water and inorganic substances such as aluminate; the Fenton iron sludge is the iron-containing sludge generated by the Fenton oxidation process. The organic matter content in the Fenton iron sludge is 40.5%, the iron content is 25.8%, the water content is 32.6%, and the rest are metals such as copper and zinc.

[0044] Example 1

[0045] A method for preparing a catalyst based on Fenton iron sludge and activated sludge, comprising the following steps: S1. Crush the Fenton iron sludge, activated sludge and binder and then pass through a 100-mesh sieve; S2. Mix the sieved Fenton iron sludge, activated sludge and binder, then mix with a pore-forming agent and carbon powder to form a mixed material. Then add a transition metal salt solution to the mixed material and stir to obtain an initial mixture; Among them, in step S2, the transition metal salt solution is a manganese chloride solution with a concentration of 0.1 mol / L, the binder is clay, the pore-forming agent is polyethylene glycol, the carbon powder is activated carbon powder, and the added mass ratio of the activated sludge, Fenton iron sludge, carbon powder, pore-forming agent and binder is 10:10:1:1:20, and the added mass ratio of the mixed material to the transition metal salt solution is 1:1; S3. Press the initial mixture into a 5-mm spherical material, dry it at room temperature for 24 h to form a blank material. Then heat the blank material in a muffle furnace at a heating rate of 5 °C / min to 700 °C for pyrolysis for 2 h, and control the atmosphere in the furnace to be 5% volume fraction of oxygen and the balance of nitrogen during the pyrolysis process. After the pyrolysis is completed, cool it to room temperature.

[0046] Example 2

[0047] A method for preparing a catalyst based on Fenton iron sludge and activated sludge, comprising the following steps: S1. Crush the Fenton iron sludge, activated sludge and binder and then pass through a 100-mesh sieve; S2. Mix the sieved Fenton iron sludge, activated sludge and binder, then mix with a pore-forming agent and carbon powder to form a mixed material. Then add a transition metal salt solution to the mixed material and stir to obtain an initial mixture; Among them, in step S2, the transition metal salt solution is a nickel sulfate solution with a concentration of 0.01 mol / L, the binder is bentonite, the pore-forming agent is starch, the carbon powder is activated carbon powder, and the mass ratio of the addition of activated sludge, Fenton iron sludge, carbon powder, pore-forming agent and binder is 70:10:0.5:0.05:20, and the mass ratio of the addition of the transition metal salt solution to the mixed material is 8:10; S3. Press the preliminary mixture into pellets with a diameter of 5 mm, dry at room temperature for 24 h to form a green body, then heat the green body in a muffle furnace at a heating rate of 5 °C / min to 620 °C and pyrolyze for 3 h, and control the atmosphere in the furnace during pyrolysis to be oxygen with a volume fraction of 3% and the balance nitrogen during pyrolysis, and cool to room temperature after pyrolysis.

[0048] Example 3

[0049] A method for preparing a catalyst based on Fenton iron sludge and activated sludge, comprising the following steps: S1. Crush Fenton iron sludge, activated sludge and binder and pass through a 100-mesh sieve; S2. Mix the sieved Fenton iron sludge, activated sludge and binder, then mix with a pore-forming agent and carbon powder to form a mixed material, and then add a transition metal salt solution to the mixed material and stir to obtain a preliminary mixture; Among them, in step S2, the transition metal salt solution is a manganese chloride solution with a concentration of 0.5 mol / L, the binder is attapulgite, the pore-forming agent is polyvinylpyrrolidone, the carbon powder is activated carbon powder, and the mass ratio of the addition of activated sludge, Fenton iron sludge, carbon powder, pore-forming agent and binder is 40:10:3:0.5:50, and the mass ratio of the addition of the transition metal salt solution to the mixed material is 12:10; S3. Press the preliminary mixture into pellets with a diameter of 5 mm, dry at room temperature for 24 h to form a green body, then heat the green body in a muffle furnace at a heating rate of 5 °C / min to 800 °C and pyrolyze for 2.5 h, and control the atmosphere in the furnace during pyrolysis to be oxygen with a volume fraction of 5% and the balance nitrogen during pyrolysis, and cool to room temperature after pyrolysis.

[0050] Example 4

[0051] A method for preparing a catalyst based on Fenton iron sludge and activated sludge is carried out according to the method in Example 1, the difference is that the transition metal salt solution in step S2 is a mixed solution of a manganese chloride solution and a nickel sulfate solution with a volume ratio of 1:1, and the concentration of the manganese chloride solution is 0.1 mol / L and the concentration of the nickel sulfate solution is 0.1 mol / L.

[0052] Example 5

[0053] A method for preparing a catalyst based on Fenton iron mud and activated sludge is carried out according to the method in Example 1, except that the transition metal salt solution in step S2 is a copper chloride solution with a concentration of 0.1 mol / L.

[0054] Example 6

[0055] A method for preparing a catalyst based on Fenton iron mud and activated sludge is carried out according to the method in Example 1, except that the specific operation of the pyrolysis treatment in step S3 is as follows: First, in a nitrogen atmosphere, the temperature is raised to 320 °C and preliminarily pyrolyzed for 50 min; then the temperature is raised to 700 °C and pyrolyzed for 30 min, and finally oxygen is introduced and treated in a mixed atmosphere with an oxygen volume fraction of 5% and the balance being nitrogen for 1 h.

[0056] Example 7

[0057] A method for preparing a catalyst based on Fenton iron mud and activated sludge is carried out according to the method in Example 1, except that the specific operation of the pyrolysis treatment in step S3 is as follows: First, in a nitrogen atmosphere, the temperature is raised to 300 °C and preliminarily pyrolyzed for 60 min; then the temperature is raised to 620 °C and pyrolyzed for 40 min, and finally oxygen is introduced and treated in a mixed atmosphere with an oxygen volume fraction of 3% and the balance being nitrogen for 1 h.

[0058] Example 8

[0059] A method for preparing a catalyst based on Fenton iron mud and activated sludge is carried out according to the method in Example 1, except that the specific operation of the pyrolysis treatment in step S3 is as follows: First, in a nitrogen atmosphere, the temperature is raised to 350 °C and preliminarily pyrolyzed for 40 min; then the temperature is raised to 800 °C and pyrolyzed for 30 min, and finally oxygen is introduced and treated in a mixed atmosphere with an oxygen volume fraction of 5% and the balance being nitrogen for 2 h.

[0060] Example 9

[0061] A method for preparing a catalyst based on Fenton iron mud and activated sludge is carried out according to the method in Example 1, except that after the pyrolysis treatment in step S3, the billet after pyrolysis treatment is also post-treated, and the specific operation is as follows: First, it is impregnated in a hydrochloric acid solution with a mass concentration of 8% at normal temperature and pressure for 15 min, and after filtration, it is then impregnated in a polarity improving liquid at normal temperature for 35 min, and the impregnation pressure is 0.5 MPa, where the polarity improving liquid is a mixture of n-hexane and benzoic acid with a mass ratio of 1:0.2; Finally, after filtration, an atmospheric pressure impregnation treatment is carried out in a mixed solution containing ethylenediamine, PAMAM, and amino-silane KH-550 for 50 min at an impregnation temperature of 50 °C. The mixed solution is prepared by mixing ethylenediamine, PAMAM, amino-silane KH-550, and water in a mass ratio of 1:0.3:0.7:5. After filtration, it is dried to obtain the catalyst.

[0062] Example 10

[0063] A method for preparing a catalyst based on Fenton iron mud and activated sludge is carried out according to the method in Example 1, except that after the pyrolysis treatment in step S3, the pyrolyzed blank is further post-treated. The specific operation is as follows: First, an atmospheric pressure impregnation treatment is carried out in a hydrochloric acid solution with a mass concentration of 5% at normal temperature and pressure for 20 min. After filtration, it is then impregnated in a polarity-improving solution at normal temperature for 30 min with an impregnation pressure of 0.6 MPa. The polarity-improving solution is a mixture of n-hexane and benzoic acid with a mass ratio of 1:0.2. Finally, after filtration, an atmospheric pressure impregnation treatment is carried out in a mixed solution containing ethylenediamine, PAMAM, and amino-silane KH-550 for 40 min at an impregnation temperature of 60 °C. The mixed solution is prepared by mixing ethylenediamine, PAMAM, amino-silane KH-550, and water in a mass ratio of 1:0.3:0.6:4. After filtration, it is dried to obtain the catalyst.

[0064] Example 11

[0065] A method for preparing a catalyst based on Fenton iron mud and activated sludge is carried out according to the method in Example 1, except that after the pyrolysis treatment in step S3, the pyrolyzed blank is further post-treated. The specific operation is as follows: First, an atmospheric pressure impregnation treatment is carried out in a hydrochloric acid solution with a mass concentration of 10% at normal temperature and pressure for 10 min. After filtration, it is then impregnated in a polarity-improving solution at normal temperature for 40 min with an impregnation pressure of 0.4 MPa. The polarity-improving solution is a mixture of n-hexane and benzoic acid with a mass ratio of 1:0.3. Finally, after filtration, an atmospheric pressure impregnation treatment is carried out in a mixed solution containing ethylenediamine, PAMAM, and amino-silane KH-550 for 60 min at an impregnation temperature of 45 °C. The mixed solution is prepared by mixing ethylenediamine, PAMAM, amino-silane KH-550, and water in a mass ratio of 1:0.4:0.8:6. After filtration, it is dried to obtain the catalyst.

[0066] Example 12

[0067] A method for preparing a catalyst based on Fenton iron mud and activated sludge is carried out according to the method in Example 9, except that during post-treatment, it is not impregnated in the polarity-improving solution, and after dilute acid treatment, it is directly impregnated in the mixed solution.

[0068] Comparative Example 1 A method for preparing a catalyst was carried out according to the method in Example 1, except that the transition metal salt solution in step S2 was replaced with water in equal amounts.

[0069] Comparative Example 2 A method for preparing a catalyst was carried out according to the method in Example 1, except that no carbon powder was added in step S2.

[0070] Comparative Example 3 A method for preparing a catalyst was carried out according to the method in Example 1, except that no activated sludge was added in step S1.

[0071] Comparative Example 4 A method for preparing a catalyst was carried out according to the method in Example 1, except that no pore-forming agent was added in step S2.

[0072] Performance detection Taking phenol-containing wastewater with a TOC (total organic carbon) concentration of 200 mg / L as the treatment object, the pH value of the wastewater was 7.24. The catalyst prepared in Example 1 of the present application was used for catalytic ozonation degradation of the above wastewater. In addition, catalysts prepared by the method in Example 1 of the present application with manganese chloride concentrations of 0.05 mol / L and 0.2 mol / L in step S2 were used for the above ozonation catalytic oxidation degradation treatment of wastewater. In addition, a blank control group was set up without adding a catalyst, and only ozone was used for oxidation degradation treatment of wastewater. The catalyst prepared in Comparative Example 1 was selected to treat the wastewater, and the TOC changes of each group were measured every 5 minutes. The results are as Figure 1 shown.

[0073] It can be seen that when there was no catalyst added in the blank control group, the TOC removal rate of the wastewater was 24.1% after 40 minutes of treatment. When manganese chloride was not added in the preparation method of Comparative Example 1, the TOC removal rate was 42.8%. When the transition metal salt manganese chloride was added during the preparation of the catalyst, the TOC removal rate increased with the increase of the manganese content. When the concentration of the manganese chloride solution was 0.2 mol / L, the TOC removal rate reached 72.24%.

[0074] In addition, in order to consider the influence of the transition metal salt on the catalytic effect of the catalyst, the methods in Example 4 and Example 5 were used to statistically analyze the treatment effect of the above ozonation catalytic oxidation degradation of wastewater, as shown in Figure 2 and Figure 3 shown, Figure 2 is the treatment effect when the transition metal salt solution is a mixture of manganese chloride and nickel sulfate, Figure 3 is the treatment effect when the transition metal salt is copper chloride.

[0075] It can be seen that after adding manganese and nickel transition metal elements simultaneously during the preparation of the catalyst, the catalytic activity of the catalyst for ozone is significantly improved. When the concentrations of both are 0.1 mol / L, the removal rate of TOC reaches 73.16% after 40 minutes of treatment. When the concentration increases to 0.2 mol / L, the removal rate of TOC increases to 78.3%. Moreover, when copper chloride is selected as the metal salt, the catalytic removal effect is better. It can also be seen that the removal rate of TOC increases significantly with the increase of Cu content. When the concentration of copper chloride is 0.2 mol / L, the removal rate of TOC increases to 82.4%.

[0076] In addition, in order to consider the stability of the catalyst, the catalyst prepared according to the method in Example 4 with a manganese chloride concentration of 0.2 mol / L and a manganese sulfate concentration of 0.2 mol / L was subjected to 5 cycles of application, and the influence on the change of TOC during 5 cycles of application was considered. The results are as Figure 4 shown.

[0077] Through Figure 4 it can be seen that the TOC treatment effect of the catalyst prepared in this application is basically the same after multiple cycles of application, and there is no obvious attenuation in the degradation rate and degradation effect of TOC in the wastewater, and the performance is stable.

[0078] Finally, the catalysts prepared in the examples and comparative examples of this application were also subjected to the above-mentioned catalytic ozonation of wastewater. The TOC removal rate after 40 minutes of treatment was statistically analyzed. In addition, the TOC removal rate after 40 minutes of the 10th treatment after 10 cycles of reuse was statistically analyzed. The statistical results are shown in Table 1 below.

[0079] Table 1:

[0080] Referring to Table 1 above, compared with the case of no catalyst added during the catalytic ozonation degradation of wastewater, after adding the catalyst prepared in this application, the organic matter removal effect has been greatly improved. Combining the detection results of Example 1 and Examples 6-8, when a specific pyrolysis treatment system is selected during the preparation of the catalyst, it may have a certain fixation and optimization effect on the porous loading structure of the catalyst and an impact on the formation and distribution of metal oxides. Combining with the solution to the carbon deposition problem of the catalyst, when the catalysts in Examples 6-8 are used for the catalytic ozonation degradation of wastewater, the TOC removal rate has been significantly improved. Combining with the detection results of Examples 9-11, it can be seen that not only the TOC removal rate has been significantly improved, but also the number of cycles of use and stability of the catalyst have been significantly improved. The post-treatment helps to improve the affinity adsorption between the catalyst and organic matter, helps to improve the catalytic activity, and improves the treatment effect. Combining with the detection results of Example 12, when not treated with the polarity improvement liquid, the treatment effect is reduced.

[0081] Combining the detection results of Example 1 and Comparative Example 1, when no transition metal salt solution was additionally added in Comparative Example 1, the TOC removal rate was significantly insufficient. Combining the detection results in Comparative Example 2, the absence of carbon powder in the raw materials would affect the reduction of some metal oxides, thereby affecting the metal valence state distribution and also reducing the treatment effect. Combining the detection results of Comparative Example 3, it can be seen that when no activated sludge was added to the raw materials, the treatment effect was also reduced. On the one hand, the activated sludge pyrolyzed to form biochar as the source of the porous pore structure, and on the other hand, the metals in it could also play a catalytic role. Combining the detection results of Comparative Example 4, when no pore-forming agent was added in Comparative Example 4, the catalytic effect was significantly reduced. The addition of the pore-forming agent was helpful for forming a porous structure, which was conducive to the contact between the organic matter in the wastewater and the catalyst, and helped the catalyst catalyze oxidants such as ozone to form hydroxyl radicals to achieve the oxidation and degradation of the organic matter in the wastewater.

[0082] Finally, the Cu-Fe-based catalyst prepared in Example 5 was analyzed by XRD, and the results are as Figure 5 shown. It can be seen that oxides of iron, aluminum, and copper were detected in the catalyst, which had a synergistic effect on the catalytic oxidation and degradation of organic matter in the wastewater by ozone.

[0083] In summary, the technology of preparing the catalyst using Fenton iron sludge and activated sludge in this application not only provides a green, environmentally friendly, and sustainable solution for the resource utilization of Fenton iron sludge and activated sludge, but also solves the problem of organic matter and heavy metal enrichment in the process of preparing polyferric sulfate. The iron and heavy metals in the iron sludge and activated sludge are converted into oxides and evenly distributed at the catalyst loading sites together with other transition metal oxides, which can synergistically catalyze the oxidation and degradation of organic matter in the wastewater by ozone, hydrogen peroxide, and persulfate. It can also be used as a particle electrode in three-dimensional electrochemistry, with good catalytic effect and good commercial value.

[0084] In this application, no waste is generated during the preparation process of the catalyst. The preparation method is simple, with a large porosity, good catalytic activity, a wide applicable pH range. Using it for wastewater TOC degradation can reduce the consumption of chemicals and lower the water treatment cost.

[0085] This specific embodiment is only an explanation of this application and not a limitation of this application. Those skilled in the art can make non-creative modifications to this embodiment as needed after reading this specification, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A method for preparing a catalyst based on Fenton iron mud and activated sludge, characterized in that: The following steps are involved: S1. Fenton iron sludge, activated sludge and binder are crushed and sieved; S2, mixing the sieved Fenton iron mud, activated sludge, binder, pore former and carbon powder to form a mixed material, and then adding a transition metal salt solution to prepare a primary mixture; S3, forming the primary mixture and drying it to form a blank, which is then subjected to pyrolysis treatment to obtain a catalyst.

2. A method for preparing a catalyst based on Fenton iron mud and activated sludge according to claim 1, characterized in that: The binder is selected from one or more of clay, kaolin, attapulgite and bentonite.

3. The method for preparing a catalyst based on Fenton iron mud and activated sludge according to claim 1, characterized in that: The pore-forming agent is selected from one or more of polyvinyl pyrrolidone, polyethylene glycol, polymethyl methacrylate, ammonium bicarbonate and starch.

4. The method for preparing a catalyst based on Fenton iron mud and activated sludge according to claim 1, characterized in that: The transition metal salt solution is one or more of chlorides, sulfates, nitrates and acetates of manganese, nickel, cerium, copper, cobalt and molybdenum metals, with a concentration of 0.01-0.50 mol / L.

5. The method for preparing a catalyst based on Fenton iron mud and activated sludge according to claim 1, characterized in that: In step S2, the added mass ratio of activated sludge, Fenton iron mud, carbon powder, pore former and binder is (10-70):10:(0.5-3):(0.05-1):(20-50); The added mass ratio of transition metal salt solution to mixed material is (8-12):

10.

6. The method for preparing a catalyst based on Fenton iron mud and activated sludge according to claim 1, characterized in that: The pyrolysis temperature of the pyrolysis treatment in step S3 is 620-800°C, and the pyrolysis time is 2-3h.

7. The method for preparing a catalyst based on Fenton iron mud and activated sludge according to claim 1, characterized in that: During the pyrolysis treatment in step S3, the atmosphere is a low-oxygen environment, and the pyrolysis atmosphere is 3-5% by volume of oxygen and the remainder is an inert gas.

8. The method for preparing a catalyst based on Fenton iron mud and activated sludge according to claim 1, characterized in that: The specific operation of the pyrolysis treatment in step S3 is: First, in a nitrogen atmosphere, the temperature is raised to 300-350°C and the initial pyrolysis is carried out for 40-60 minutes; then the temperature is raised to 620-800°C and the pyrolysis treatment is carried out for 30-40 minutes, and finally oxygen is introduced and the treatment is carried out for 1-2 hours in an atmosphere in which the oxygen volume ratio is 3-5% and the balance is nitrogen.

9. A catalyst, characterized in that: The catalyst is prepared by the method for preparing the catalyst based on Fenton iron mud and activated sludge as claimed in any one of claims 1 to 8.

10. Use of the catalyst as claimed in claim 9 in water treatment.

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