A method for preparing a catalyst based on fenton iron mud and activated sludge, the catalyst prepared and applications thereof

Abstract

The application relates to the field of water treatment, and specifically discloses a method for preparing a catalyst based on Fenton iron mud and activated sludge, the prepared catalyst and application, the method comprises the following steps: S1, crushing and sieving Fenton iron mud, activated sludge and a binder; S2, mixing the sieved Fenton iron mud, activated sludge, binder, pore-forming agent and carbon powder, then adding a transition metal salt solution to prepare a primary mixture; S3, drying the primary mixture after shaping to form a blank, then performing pyrolysis treatment to prepare the catalyst; the application also discloses the catalyst prepared by the above method and application of the catalyst in water treatment. The application realizes resource utilization of Fenton iron mud and activated sludge, solves the enrichment problem of organic matters and heavy metals in wastewater in the current Fenton iron mud resource utilization technology, the prepared catalyst can be used for catalyzing ozone, hydrogen peroxide or persulfate to degrade organic matters in wastewater, and the catalyst preparation method is simple.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water treatment, more particularly, it relates to a method for preparing a catalyst based on Fenton iron sludge and activated sludge, the prepared catalyst and application. BACKGROUND

[0002] Fenton oxidation technology is often used for the treatment of refractory organic wastewater. The basic principle is that under acidic conditions, Fe 2+ and H2O2 react to produce strong oxidizing hydroxyl radicals, which mineralize organic matter into CO2 and H2O. After the reaction is completed, the pH needs to be adjusted to neutral or alkaline to convert the generated trivalent iron ions into iron hydroxide, and a flocculating agent is added to remove it by precipitation or air flotation. This method has high removal efficiency for refractory organic matter, but the iron sludge contains a large amount of organic matter and heavy metals, which is a hazardous waste and needs to be treated twice, such as incineration, landfill or cement solidification, etc., which not only significantly increases the treatment cost, but also leads to long-term waste of iron resources. Therefore, developing efficient Fenton iron sludge resource recycling technology is of great significance for the promotion of Fenton technology.

[0003] A device and method for treating Fenton iron sludge are disclosed in Chinese patent with publication number CN110877956A. The method reduces trivalent iron in the iron sludge to divalent iron by iron-reducing bacteria, then adds acid solution, and after solid-liquid separation, the acid solution rich in divalent iron can be reused in the Fenton reactor. This method can effectively reduce the consumption of divalent iron salt. However, this method will cause the concentration of heavy metals, aluminum and organic matter in the recovered divalent iron acid solution to continuously increase, ultimately affecting the Fenton reaction effect and the biological activity of iron-reducing bacteria.

[0004] A method for resource utilization of Fenton iron sludge is disclosed in Chinese patent with publication number CN105836987A. The method first adds sulfuric acid to the iron sludge to completely convert the iron hydroxide in the iron sludge into a sulfuric acid iron solution, then dilutes the solution and passes it into the anode chamber of a diaphragm electrolytic cell to remove organic matter by electro-oxidation, and then passes it into the cathode chamber to reduce trivalent iron to divalent iron ions by electro-reduction. After the reaction is completed, the industrial product ferrous sulfate is prepared by concentrating and crystallizing under the protection of inert gas. However, this method has limited removal rate of heavy metals, which affects the quality of the ferrous sulfate product, and the two-step electrolysis method consumes too much electricity.

[0005] A method for recycling Fenton reaction catalyst is disclosed in Chinese patent with publication number CN102849803B. The method adds concentrated sulfuric acid to the iron sludge after centrifugal dewatering, and controls the [SO4 2- ] / [Fe] tThe ratio of the two is within 1.15-1.35, so that it can fully occur polymerization reaction, then in the state of stirring, deionized water is added, and the pH is adjusted to 1.0-1.5, to obtain a polymeric ferric sulfate solution which can be recycled for flocculation process. However, this method still does not solve the problem of accumulation of organic matter and heavy metals.

[0006] A Chinese patent with publication number CN106810204A discloses a Fenton iron sludge anode-cathode integrated ceramsite and a method for preparing ceramsite using Fenton iron sludge. The method mixes Fenton iron sludge, clay, fly ash and balling agent according to a certain proportion, granulates into balls, dries at room temperature, and sintered at 600℃ to prepare Fenton iron sludge anode-cathode integrated ceramsite, which can be used for micro-electrolysis treatment of organic matter, and also can be used as filler for biological filter and sulfidation reaction bed. However, when the ceramsite prepared by this method is used for iron-carbon micro-electrolysis treatment of wastewater, the iron dissolution speed is fast, the service life is short, and the filler is easy to be hardened.

[0007] Therefore, although there are many records of resource recycling of Fenton iron sludge, there are still different degrees of defects, such as accumulation of heavy metals and organic matter, difficulty in controlling preparation conditions, short service life of prepared materials, etc. It is necessary to provide new resource recycling means to solve the problem of enrichment of organic matter and heavy metals in wastewater in the existing resource recycling technology, improve the service life of the prepared catalyst, and simplify the preparation process. SUMMARY

[0008] To realize resource recycling of Fenton iron sludge and activated sludge, solve the problem of enrichment of organic matter and heavy metals in wastewater in the existing resource recycling technology of Fenton iron sludge, improve the service life of the prepared catalyst, and simplify the preparation process, the present application provides a method for preparing a catalyst based on Fenton iron sludge and activated sludge and application thereof.

[0009] In a first aspect, the present application provides a method for preparing a catalyst based on Fenton iron sludge and activated sludge, which adopts the following technical solution:

[0010] A method for preparing a catalyst based on Fenton iron sludge and activated sludge, comprising the following steps:

[0011] S1, crushing and sieving Fenton iron sludge, activated sludge and binder;

[0012] S2, mixing the sieved Fenton iron sludge, activated sludge, binder, pore-forming agent and carbon powder to form a mixture, then adding a transition metal salt solution to prepare a preliminary mixture;

[0013] S3, drying the preliminary mixture after shaping to form a blank, then performing pyrolysis treatment to prepare a catalyst.

[0014] By adopting the technical scheme, the catalyst in the application takes Fenton iron sludge and activated sludge as substrates, and microorganisms in the Fenton iron sludge and the activated sludge undergo pyrolysis and carbonization reactions under anaerobic high-temperature conditions to generate biochar or graphitized carbon with high porosity and excellent adsorption performance; trivalent iron in the Fenton iron sludge is first formed into Fe2O3 in the pyrolysis process, and then partially reduced into FeO and a small amount of iron element with carbon powder as a reducing agent; the pore former decomposes or volatilizes under high temperature to form microporous and mesoporous structures; the added transition metal salt forms corresponding metal oxides after pyrolysis treatment, which are uniformly distributed on the surface of the catalyst and the loading sites inside the pores, and have a synergistic effect with iron oxides and metal oxides formed by heavy metals in the Fenton iron sludge and the activated sludge, so as to catalyze hydrogen peroxide, ozone and persulfate to generate strong oxidizing substances to degrade organic matter in wastewater in a wide pH range.

[0015] The method in the application realizes resource utilization of the Fenton iron sludge and the activated sludge without secondary pollution, the catalyst prepared in the application has a large specific surface area, which is beneficial to diffusion and adsorption of oxidizing agents such as ozone, persulfate and hydrogen peroxide and organic molecules in the catalyst during wastewater treatment, improves the catalytic reaction effect and efficiency, and can also occur Fenton-like reaction as a granular electrode in the electro-catalytic oxidation process.

[0016] Optionally, the binder is selected from one or more of clay, kaolin, attapulgite and bentonite.

[0017] Optionally, the pore former is selected from one or more of polyvinylpyrrolidone, polyethylene glycol, polymethyl methacrylate, ammonium bicarbonate and starch.

[0018] By adopting the technical scheme, the binder in the application is selected from the above clay minerals, the main component of which is silicate, and the binder has excellent adhesion and mechanical properties; after being mixed with the transition metal salt solution, the binder has certain adhesion to bond the initial mixture, and forms a stable ceramic phase with a porous structure under high temperature, thereby improving the mechanical strength, specific surface area, stability and service life of the catalyst.

[0019] The pore former selected in the application can form microporous and mesoporous structures during the preparation of the catalyst, increase the specific surface area of the catalyst, expose more active sites of the catalyst, and improve the catalytic activity of the catalyst.

[0020] Optionally, the transition metal salt solution is one or more of chloride, sulfate, nitrate and acetate 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.

[0021] By adopting the technical scheme, the addition of the transition metal salt solution can ensure the uniformity and concentration of the metal in the catalyst, the generated transition metal oxide can catalyze together with the iron oxide, the degradation of the organic matter is strengthened, the dissolution rate of the iron oxide is reduced, and the service life of the catalyst is improved. In the process of catalytic oxidation degradation of the organic matter in wastewater, the above-mentioned transition metal ions promote the generation of strong oxidizing substances such as hydroxyl radicals, thereby accelerating the degradation of the organic matter, or participating in the electron transfer reaction in the catalytic process, reducing the reaction activation energy, playing a catalytic role, and improving the treatment effect and efficiency.

[0022] Optionally, the carbon powder is activated carbon powder or fly ash, and more preferably, the activated carbon powder is waste activated carbon powder to be regenerated for water treatment.

[0023] By adopting the technical scheme, the carbon powder added in the application can adjust the valence state of the metal oxide generated in the pyrolysis process, thereby adjusting the active component of the catalyst, on the other hand, it is beneficial to the formation of a porous structure of the catalyst in the pyrolysis process, and can also assist in dispersing the metal oxide particles, adjusting the mechanical strength, thermal stability and electrical conductivity of the catalyst, and reducing the preparation cost of the catalyst.

[0024] Optionally, the mass ratio of the activated sludge, Fenton iron sludge, carbon powder, pore-forming agent and binder added in step S2 is (10-70):10:(0.5-3):(0.05-1):(20-50).

[0025] Optionally, the mass ratio of the transition metal salt solution to the mixture is (8-12):10.

[0026] By adopting the technical scheme, the structural stability of the catalyst particles and the concentration of the iron oxide in the catalyst are ensured when the above-mentioned addition amount is adopted, and the catalytic effect of the finally prepared catalyst is better.

[0027] Optionally, the pyrolysis temperature of the pyrolysis treatment in step S3 is 620-800 ℃, and the pyrolysis time is 2-3h.

[0028] By adopting the technical scheme, when the above-mentioned pyrolysis parameters are adopted, it is helpful for the formation of corresponding metal oxides of iron hydroxide and metal salt.

[0029] Optionally, in step S3, during the pyrolysis treatment, the atmosphere is a low-oxygen environment, and the pyrolysis atmosphere is 3-5% oxygen and the remaining amount of inert gas with a volume ratio of 1:(2-3).

[0030] By adopting the above technical scheme, when the above atmosphere pyrolysis treatment is adopted, the iron hydroxide and metal salt in the iron sludge can be converted into corresponding metal oxides, and under the reduction of carbon powder, part of the metal oxides are reduced into lower valence oxides, and different metal oxides can synergistically catalyze more strong oxidizing media generated by oxidizing agents such as ozone and hydrogen peroxide, thereby improving the organic matter degradation efficiency.

[0031] In the final step S3, preliminary drying is first performed at room temperature for pretreatment, which can prevent the catalyst from being broken or cracked in the subsequent pyrolysis sintering process, thereby affecting the structural stability, and then the pyrolysis time and temperature and atmosphere are controlled, so that the organic matters in the Fenton iron sludge and the activated sludge can be converted into biochar, and it can also be ensured that the generated biomass charcoal and carbon powder will not be over-graphitized, thereby causing the destruction of the pore structure and the decomposition of the functional groups or even the conversion into ash.

[0032] Optionally, the pyrolysis treatment in step S3 is specifically as follows:

[0033] First, the temperature is raised to 300-350 DEG C in a nitrogen atmosphere, and preliminary pyrolysis is performed for 40-60 min; then the temperature is raised to 620-800 DEG C, and pyrolysis treatment is performed for 30-40 min; finally, oxygen is introduced, and the oxygen volume ratio is 3-5%, and the remaining amount is nitrogen, and the nitrogen volume ratio is 3: (7-8).

[0034] By adopting the above technical scheme, the pyrolysis treatment system is adopted, preliminary pyrolysis is first performed to remove volatile components, and then the temperature is continuously raised for pyrolysis treatment, which is helpful for further stabilizing and carbonizing the catalyst structure, improving the catalytic activity, and by adjusting the atmosphere at different stages, the iron hydroxide and metal salt in the blank can be converted into metal oxides, and then part of the metal oxides are reduced to lower valence metal oxides by using the reduction effect of carbon powder at high temperature, thereby improving the catalytic activity.

[0035] In the catalyst preparation process, a layer of carbon-containing inactive substance, i.e. carbon deposition, is formed on the surface, which blocks the active sites of the catalyst or the pores of the catalyst, reduces the effective specific surface area, and reduces the catalyst activity. In the present application, the treatment in the oxygen and nitrogen mixed atmosphere also helps to remove the carbon deposits accumulated on the surface of the catalyst.

[0036] Optionally, after the pyrolysis treatment in step S3, the blank after the pyrolysis treatment is subjected to post-treatment, and the specific operation is as follows: first, the blank is immersed in a dilute acid solution, then immersed in a polarity improvement liquid, and finally immersed in a mixed solution of ethylenediamine, PAMAM and aminosilane, and then dried to obtain the catalyst, wherein the polarity improvement liquid is selected from n-hexane and benzoic acid with a mass ratio of 1: (0.2-0.3).

[0037] By adopting the technical scheme, the blank after pyrolysis treatment is first immersed in a dilute acid solution to remove impurities and accumulated carbon on the surface of the blank and optimize the surface pore structure, and then immersed in a polarity improvement liquid to affect the polarity of the catalyst, so that the polar catalyst is more easily interacted with polar organic molecules, thereby enhancing the adsorption effect, which helps to enrich organic molecules on the surface of the catalyst, providing favorable conditions for subsequent oxidative degradation. Finally, the catalyst is treated in a mixed solution of aminosilane, ethylenediamine and PAMAM to introduce amino groups on the surface of the catalyst. Amino groups, as nucleophilic functional groups, 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, amino groups can also promote the activation of oxidizing agents such as hydrogen peroxide and ozone on the surface of the catalyst, thereby facilitating the oxidative degradation process.

[0038] Optionally, in the post-treatment process, the dilute acid solution is a hydrochloric acid solution with a mass concentration of 5-10%, the immersion treatment in the dilute acid solution is performed for 10-20 min, the immersion time in the polarity improvement liquid is 30-40 min, the immersion pressure is 0.4-0.6 MPa, the mixed solution is prepared by mixing ethylenediamine, PAMAM and aminosilane with water in a mass ratio of 1:(0.3-0.4):(0.6-0.8):(4-6), the immersion time is 40-60 min, and the immersion temperature is 45-60℃.

[0039] By adopting the above technical scheme, the above immersion treatment can make the catalyst have stronger adsorption performance and catalytic performance, which helps to improve the oxidative degradation of oxidizing agents on organic matter in wastewater.

[0040] In the second aspect, the application provides a catalyst, which adopts the following technical scheme:

[0041] A catalyst prepared by the method.

[0042] By adopting the above technical scheme, the catalyst prepared by the method in the application has a rich pore structure and good adsorption performance. Moreover, the catalyst is prepared based on Fenton iron mud and activated sludge, so that the catalyst pore structure 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 oxidizing ability, thereby oxidizing and decomposing organic matter in wastewater into carbon dioxide and water, solving the problem of enrichment of organic matter and heavy metals during Fenton iron mud treatment.

[0043] In the third aspect, the application provides an application of a catalyst, which adopts the following technical scheme:

[0044] An application of a catalyst in water treatment.

[0045] By adopting the technical scheme, the method in the application realizes resource recycling of Fenton iron sludge and activated sludge, and solves the enrichment problems of organic matters and heavy metals in the existing resource recycling technology, utilizes carbonization of the organic matters to form biochar to realize construction of a porous structure, and prepares a catalyst with a porous structure, and the iron in the Fenton iron sludge and the heavy metals in the Fenton iron sludge and the activated sludge and the added transition metal salt form metal oxides after pyrolysis to realize synergistic effect and high-efficiency catalysis.

[0046] In summary, the application has the following beneficial effects:

[0047] 1. The method in the application realizes resource recycling of Fenton iron sludge and activated sludge, solves the pollution of Fenton iron sludge and activated sludge solid waste, utilizes carbonization of the organic matters to form biochar to realize construction of a porous structure, and prepares a catalyst with a porous structure, and the iron in the Fenton iron sludge and the added transition metal salt form metal oxides after pyrolysis, which are uniformly distributed inside and on the surface of the catalyst, and have good catalytic effect and long service life.

[0048] 2. The catalyst prepared by the application has good adsorption performance and can be used for high-efficiency catalysis of ozone, hydrogen peroxide or persulfate to generate hydroxyl radicals or sulfate radicals with strong oxidation, and degradation of organic matters in wastewater. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 is an effect diagram of catalysis of ozone oxidation and degradation of TOC by the catalyst with different Mn contents in the method in Example 1 of the application;

[0050] Figure 2 is an effect diagram of catalysis of ozone oxidation and degradation of TOC by the catalyst with different Mn and Ni contents in the method in Example 4 of the application;

[0051] Figure 3 is an effect diagram of catalysis of ozone oxidation and degradation of TOC by the catalyst with different Cu contents in the method in Example 5 of the application;

[0052] Figure 4 is an effect diagram of the Mn(0.20 mol / L)-Ni(0.20 mol / L) catalyst in the method in Example 4 of the application after multiple cycles;

[0053] Figure 5 is a crystallization state diagram of the catalyst prepared in Example 5 of the application detected by XRD. DETAILED DESCRIPTION

[0054] The application is further described in detail in combination with the examples, and it is particularly stated that: in the following examples, the specific conditions are not specified, and the conventional conditions or the conditions recommended by the manufacturers are adopted, and the raw materials used in the following examples can be obtained from ordinary commercial sources unless otherwise specified.

[0055] The green body after the shaping of the initial mixture in step S3 in the method provided in the application can be spherical or columnar particles, and when it is columnar particles, the length is 3-10 mm.

[0056] The activated sludge in the following examples is selected from the concentrated activated sludge in the secondary sedimentation tank of a biochemical treatment process, and the organic matter content in the activated sludge is 29.6%, the microbial content is 35.8%, and the rest is water and inorganic substances such as aluminate; the Fenton iron sludge is the iron-containing sludge generated in the Fenton oxidation process, and 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 is metals such as copper and zinc.

[0057] Example 1

[0058] A method for preparing a catalyst based on Fenton iron sludge and activated sludge, comprising the following steps:

[0059] S1, crushing the Fenton iron sludge, activated sludge and binder and then passing them through a 100-mesh sieve;

[0060] S2, mixing the sieved Fenton iron sludge, activated sludge and binder, then mixing them with a pore former and carbon powder to form a mixture, and then adding a transition metal salt solution to the mixture and stirring to obtain an initial mixture;

[0061] 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 former is polyethylene glycol, the carbon powder is activated carbon powder, and the mass ratio of the activated sludge, Fenton iron sludge, carbon powder, pore former and binder is 10:10:1:1:20, and the mass ratio of the mixture to the transition metal salt solution is 1:1;

[0062] S3, the initial mixture is press-formed into a 5-mm ball, dried at room temperature for 24 h to form a green body, and then the green body is heated to 700℃ at a heating rate of 5℃ / min in a muffle furnace for pyrolysis for 2 h, and the atmosphere in the furnace is controlled to be 5% oxygen and the rest nitrogen during pyrolysis, and the temperature is cooled to room temperature after pyrolysis.

[0063] Example 2

[0064] A method for preparing a catalyst based on Fenton iron sludge and activated sludge, comprising the following steps:

[0065] S1, crushing the Fenton iron sludge, activated sludge and binder and then passing them through a 100-mesh sieve;

[0066] S2, mixing the sieved Fenton iron sludge, activated sludge and binder, then mixing them with a pore former and carbon powder to form a mixture, and then adding a transition metal salt solution to the mixture and stirring to obtain an initial mixture;

[0067] 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 active 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 transition metal salt solution to the mixture is 8:10.

[0068] S3, the initial mixture is pressure formed into a 5mm ball, dried at room temperature for 24h to form a blank, and then the blank is heated to 620℃ at a heating rate of 5℃ / min in a muffle furnace for pyrolysis for 3h, and the atmosphere in the furnace during pyrolysis is controlled to be 3% oxygen and the balance nitrogen by volume, and after pyrolysis, the temperature is cooled to room temperature.

[0069] Example 3

[0070] A method for preparing a catalyst based on Fenton iron sludge and active sludge, comprising the following steps:

[0071] S1, crushing the Fenton iron sludge, active sludge and binder and then passing through a 100 mesh sieve;

[0072] S2, mixing the sieved Fenton iron sludge, active sludge and binder, then mixing with the pore forming agent and carbon powder to form a mixture, then adding a transition metal salt solution to the mixture and stirring to obtain an initial mixture;

[0073] 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, and the carbon powder is activated carbon powder, and the mass ratio of the active sludge, Fenton iron sludge, carbon powder, pore forming agent and binder is 40:10:3:0.5:50, and the mass ratio of the transition metal salt solution to the mixture is 12:10.

[0074] S3, the initial mixture is pressure formed into a 5mm ball, dried at room temperature for 24h to form a blank, and then the blank is heated to 800℃ at a heating rate of 5℃ / min in a muffle furnace for pyrolysis for 2.5h, and the atmosphere in the furnace during pyrolysis is controlled to be 5% oxygen and the balance nitrogen by volume, and after pyrolysis, the temperature is cooled to room temperature.

[0075] Example 4

[0076] A method for preparing a catalyst based on Fenton iron sludge and active sludge, according to the method in Example 1, the difference is that in step S2, the transition metal salt solution is a mixed solution of manganese chloride solution and 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.

[0077] Example 5

[0078] A method for preparing a catalyst based on Fenton iron sludge and activated sludge is carried out according to the method in Example 1, except that the transition metal salt solution in step S2 is selected as a copper chloride solution with a concentration of 0.1 mol / L.

[0079] Example 6

[0080] A method for preparing a catalyst based on Fenton iron sludge and activated sludge is carried out according to the method in Example 1, except that the specific operation of pyrolysis treatment in step S3 is: first, in a nitrogen atmosphere, the temperature is raised to 320℃, and the initial pyrolysis is 50min; then the temperature is raised to 700℃, and the pyrolysis treatment is 30min, and finally oxygen is introduced, and the mixed gas atmosphere with oxygen volume ratio of 5% and nitrogen as the balance is treated for 1h.

[0081] Example 7

[0082] A method for preparing a catalyst based on Fenton iron sludge and activated sludge is carried out according to the method in Example 1, except that the specific operation of pyrolysis treatment in step S3 is: first, in a nitrogen atmosphere, the temperature is raised to 300℃, and the initial pyrolysis is 60min; then the temperature is raised to 620℃, and the pyrolysis treatment is 40min, and finally oxygen is introduced, and the mixed gas atmosphere with oxygen volume ratio of 3% and nitrogen as the balance is treated for 1h.

[0083] Example 8

[0084] A method for preparing a catalyst based on Fenton iron sludge and activated sludge is carried out according to the method in Example 1, except that the specific operation of pyrolysis treatment in step S3 is: first, in a nitrogen atmosphere, the temperature is raised to 350℃, and the initial pyrolysis is 40min; then the temperature is raised to 800℃, and the pyrolysis treatment is 30min, and finally oxygen is introduced, and the mixed gas atmosphere with oxygen volume ratio of 5% and nitrogen as the balance is treated for 2h.

[0085] Example 9

[0086] A method for preparing a catalyst based on Fenton iron sludge and activated sludge is carried out according to the method in Example 1, except that after pyrolysis treatment in step S3, the pyrolysis treated blank is further treated, and the specific operation is:

[0087] first, in a hydrochloric acid solution with a mass concentration of 8%, it is immersed and treated at room temperature and normal pressure for 15min, and then filtered and immersed in a polarity improving liquid at room temperature for 35min, and the immersion pressure is 0.5MPa, and the polarity improving liquid is selected as n-hexane and benzoic acid with a mass ratio of 1:0.2;

[0088] After filtration, the catalyst was prepared by normal pressure impregnation treatment in a mixed solution containing ethylenediamine, PAMAM and amino silane KH-550 for 50 min at 50℃, the mixed solution was prepared by mixing ethylenediamine, PAMAM and amino silane KH-550 with water according to a mass ratio of 1:0.3:0.7:5, and the catalyst was obtained after filtration and drying.

[0089] Example 10

[0090] A method for preparing a catalyst based on Fenton iron mud and activated sludge was performed according to the method in Example 1, except that after pyrolysis treatment in step S3, the pyrolysis-treated blank was further treated, and the specific operation was as follows:

[0091] First, the blank was impregnated in a hydrochloric acid solution with a mass concentration of 5% at normal temperature and pressure for 20 min, then impregnated in a polarity improvement liquid at normal temperature for 30 min after filtration, and the impregnation pressure was 0.6 MPa, wherein the polarity improvement liquid was selected from n-hexane and benzoic acid with a mass ratio of 1:0.2;

[0092] After filtration, the catalyst was prepared by normal pressure impregnation treatment in a mixed solution containing ethylenediamine, PAMAM and amino silane KH-550 for 40 min at 60℃, the mixed solution was prepared by mixing ethylenediamine, PAMAM and amino silane KH-550 with water according to a mass ratio of 1:0.3:0.6:4, and the catalyst was obtained after filtration and drying.

[0093] Example 11

[0094] A method for preparing a catalyst based on Fenton iron mud and activated sludge was performed according to the method in Example 1, except that after pyrolysis treatment in step S3, the pyrolysis-treated blank was further treated, and the specific operation was as follows:

[0095] First, the blank was impregnated in a hydrochloric acid solution with a mass concentration of 10% at normal temperature and pressure for 10 min, then impregnated in a polarity improvement liquid at normal temperature for 40 min after filtration, and the impregnation pressure was 0.4 MPa, wherein the polarity improvement liquid was selected from n-hexane and benzoic acid with a mass ratio of 1:0.3;

[0096] After filtration, the catalyst was prepared by normal pressure impregnation treatment in a mixed solution containing ethylenediamine, PAMAM and amino silane KH-550 for 60 min at 45℃, the mixed solution was prepared by mixing ethylenediamine, PAMAM and amino silane KH-550 with water according to a mass ratio of 1:0.4:0.8:6, and the catalyst was obtained after filtration and drying.

[0097] Example 12

[0098] A method for preparing a catalyst based on Fenton iron mud and activated sludge was carried out according to the method in Example 9, except that the post-treatment was not immersed in the polarity improvement liquid, and the diluted acid treatment was directly immersed in the mixed solution.

[0099] Comparative Example 1

[0100] 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 an equal amount of water.

[0101] Comparative Example 2

[0102] 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.

[0103] Comparative Example 3

[0104] 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.

[0105] Comparative Example 4

[0106] 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.

[0107] Performance test

[0108] A phenol-containing wastewater with a TOC (total organic carbon) concentration of 200 mg / L was used as the treatment object, and the pH value of the wastewater was 7.24. The catalyst prepared in Example 1 of the present application was used to catalyze the ozone oxidation degradation of the above wastewater. In addition, catalysts prepared by the method of Example 1 of the present application and with manganese chloride concentrations of 0.05 mol / L and 0.2 mol / L in step S2 were used for the above ozone catalytic oxidation degradation treatment of wastewater. In addition, a blank control group was set up without adding catalyst, and only ozone was used for the oxidation degradation treatment of wastewater. The catalyst prepared in Comparative Example 1 was selected for the treatment of wastewater. The TOC changes of each group were measured at intervals of 5 min, and the results are shown in Table 1. Figure 1

[0109] It can be seen that when the blank control group, i.e., without adding catalyst, the TOC removal rate of the wastewater after 40 min of treatment was 24.1%. When no manganese chloride was added in the preparation method of Comparative Example 1, the TOC removal rate was 42.8%. When manganese chloride transition metal salt was added during the preparation of the catalyst, the TOC removal rate increased with the increase of manganese content. When the concentration of the manganese chloride solution was 0.2 mol / L, the TOC removal rate reached 72.24%.

[0110] ​In addition, in order to consider the influence of transition metal salt on the catalytic effect of the catalyst, the wastewater treatment effect of ozone catalytic oxidation degradation is counted by the method in Example 4 and Example 5, and the results are shown in Figure 2 and Figure 3 , Figure 2 is the treatment effect of the transition metal salt solution selected from the mixture of manganese chloride and nickel sulfate, Figure 3 is the treatment effect of the transition metal salt selected from copper chloride.

[0111] It can be seen that after adding manganese and nickel transition metal elements at the same time when preparing the catalyst, the catalytic activity of the catalyst for ozone is obviously improved. When the concentration of both is 0.1 mol / L, the removal rate of TOC reaches 73.16% after 40 min of treatment. When the concentration increases to 0.2 mol / L, the removal rate of TOC increases to 78.3%. When the metal salt is selected from copper chloride, the catalytic removal effect is better, and it can be seen that the removal rate of TOC is obviously improved 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%.

[0112] In addition, in order to consider the stability of the catalyst, the catalyst prepared according to the method in Example 4 and with the concentration of manganese chloride being 0.2 mol / L and the concentration of manganese sulfate being 0.2 mol / L is applied for 5 cycles. The influence of TOC change after 5 cycles is considered, and the results are shown in Figure 4 .

[0113] It can be seen from Figure 4 that the TOC effect of the catalyst prepared in the application is basically consistent after multiple cycles of application for wastewater treatment. The degradation rate and degradation effect of TOC in wastewater do not show obvious attenuation, and the performance is stable.

[0114] Finally, the catalyst prepared in the examples and comparative examples of the application is also subjected to the above wastewater ozone catalytic oxidation. The removal rate of TOC after 40 min of treatment is counted, and the removal rate of TOC after 40 min of treatment in the 10th cycle after 10 cycles of recycling is counted. The statistical results are shown in Table 1.

[0115] Table 1:

[0116]

[0117] Referring to Table 1, compared with the wastewater treatment by ozone oxidation without adding the catalyst, the removal effect of organic matter is greatly improved after adding the catalyst prepared in the application. According to the detection results of Example 1 and Examples 6-8, when the specific pyrolysis treatment system is selected in the preparation of the catalyst, it may have certain fixing optimization for the porous load structure of the catalyst and influence on the distribution of the metal oxide. In combination with the solution to the carbon deposition problem of the catalyst, the TOC removal rate is obviously improved when the catalyst is used for ozone catalytic oxidation degradation of wastewater treatment in Examples 6-8. According to the detection results of Examples 9-11, it can be seen that not only the TOC removal rate is obviously improved, but also the recycling number and stability of the catalyst are obviously improved. The post-treatment helps to improve the affinity and adsorption between the catalyst and the organic matter, improve the catalytic activity and improve the treatment effect. According to the detection results of Example 12, the treatment effect is reduced when the polar improvement liquid is not treated.

[0118] According to the detection results of Example 1 and Comparative Example 1, the TOC removal rate is obviously insufficient when the transition metal salt solution is not additionally added in Comparative Example 1. According to the detection results of Comparative Example 2, the reduction of part of the metal oxide is affected when the carbon powder is not added in the raw material, thereby affecting the metal valence state distribution and reducing the treatment effect. According to the detection results of Comparative Example 3, it can be seen that the treatment effect is also reduced when the activated sludge is not added in the raw material. On the one hand, the biochar formed after pyrolysis of the activated sludge serves as a source of porous pore structure, and on the other hand, the metal therein can also play a catalytic role. According to the detection results of Comparative Example 4, the catalytic effect is obviously reduced when the pore former is not added in Comparative Example 4. The addition of the pore former helps to form a porous structure, thereby facilitating the contact between the organic matter in the wastewater and the catalyst and helping the catalyst to catalyze the oxidant such as ozone to form hydroxyl radicals to realize the oxidation degradation of the organic matter in the wastewater.

[0119] Finally, the Cu-Fe catalyst prepared in Example 5 is subjected to XRD analysis, and the results are shown in Table 1. Figure 5 As can be seen, the oxides of iron, aluminum and copper are detected in the catalyst, which has a synergistic effect on the catalytic oxidation degradation of organic matter in wastewater by ozone.

[0120] In summary, the catalyst preparation technology using Fenton iron sludge and activated sludge in the application not only provides a green and environmentally friendly and sustainable solution for the resource utilization of Fenton iron sludge and activated sludge, but also solves the problem of enrichment of organic matter and heavy metals in the preparation of polymeric ferric sulfate. The iron and heavy metals in the iron sludge are converted into oxides, which are uniformly distributed with other transition metal oxides at the catalyst load site, can synergistically catalyze the oxidation of organic matter in wastewater by ozone, hydrogen peroxide and persulfate, and can also be used as a particle electrode in three-dimensional electrochemistry, has good catalytic effect and good commercial value.

[0121] The preparation process of the catalyst in the application does not produce waste, the preparation method is simple, the porosity is large, the catalytic activity is good, the pH range is wide, the reagent consumption can be reduced when the catalyst is used for wastewater TOC degradation, and the water treatment cost is reduced.

[0122] The specific embodiments are only an explanation of the application, not a limitation of the application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, but as long as the modifications are within the scope of the claims of the application, they are protected by the patent law.

Claims

1. A method for preparing a catalyst based on Fenton's iron mud and activated sludge, characterized in that, The method comprises the following steps: S1, crushing and sieving Fenton iron mud, activated sludge and a binder; S2, mixing the sieved Fenton iron mud, activated sludge, binder, pore-forming agent and carbon powder to form a mixture, then adding a transition metal salt solution to prepare a primary mixture; S3, drying the primary mixture after shaping to form a blank, and then performing pyrolysis treatment to prepare a catalyst; In the pyrolysis treatment in step S3, the atmosphere is a low-oxygen environment, and the pyrolysis atmosphere is 3-5% oxygen and the balance of inert gas by volume; The carbon powder is activated carbon powder, and the transition metal in the transition metal salt solution is one or more of manganese, nickel and copper.

2. The 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 kaolin, attapulgite and bentonite.

3. The method of claim 1, wherein the catalyst is prepared based on Fenton iron mud and activated sludge. The pore-forming agent is selected from one or more of polyvinylpyrrolidone, 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 chloride, sulfate, nitrate and acetate of manganese, nickel and copper metal, and the concentration is 0.01-0.50 mol / L.

5. The method of claim 1, wherein the catalyst is prepared based on Fenton iron mud and activated sludge. In step S2, the mass ratio of activated sludge, Fenton iron mud, carbon powder, pore-forming agent and binder is (10-70):10:(0.5-3):(0.05-1):(20-50); and the mass ratio of the transition metal salt solution to the mixture is (8-12):

10.

6. The method of claim 1, wherein the catalyst is prepared based on Fenton iron mud and activated sludge. In step S3, the pyrolysis temperature of the pyrolysis treatment is 620-800 ℃, and the pyrolysis time is 2-3 h.

7. The method of claim 1, wherein the catalyst is prepared based on Fenton iron mud and activated sludge. In step S3, the pyrolysis treatment is specifically performed as follows: first, in a nitrogen atmosphere, the temperature is raised to 300-350 ℃, and the initial pyrolysis is performed for 40-60 min; then the temperature is raised to 620-800 ℃, and the pyrolysis treatment is performed for 30-40 min; finally, oxygen is introduced, and the oxygen volume ratio is 3-5%, and the balance is nitrogen atmosphere for 1-2 h.

8. A catalyst characterized by: The catalyst is prepared by the method for preparing a catalyst based on Fenton iron mud and activated sludge according to any one of claims 1-7.

9. The catalyst according to claim 8 is used in the catalytic oxidation degradation of wastewater.

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