Sludge-based iron-based catalyst as well as preparation method and application thereof

Abstract

The invention provides a sludge-based iron-based catalyst and a preparation method and application thereof, and belongs to the technical field of catalysts and sewage treatment. The preparation method of the sludge-based iron-based catalyst comprises the following steps: respectively drying, crushing and sieving Fenton iron sludge and biochemical sludge to obtain a Fenton iron sludge dry material and a biochemical sludge dry material; and mixing the dry Fenton iron sludge material and the dry biochemical sludge material, and then performing pyrolysis under an anaerobic condition to obtain the sludge-based iron-based catalyst. The preparation method is simple, no chemical agent is used, the raw material is waste mud, and the purpose of treating waste with waste is achieved. The prepared catalyst can be used for efficiently degrading landfill leachate MBR effluent.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst and sewage treatment, and in particular to a sludge-based iron-based catalyst and a preparation method and application thereof. Background Art

[0002] With the development of social economy, a large amount of refractory wastewater is produced, which is difficult to treat with general coagulation and biochemical technologies. Advanced oxidation technology is needed for treatment, including Fenton oxidation technology. Fenton oxidation technology can degrade organic matter by producing strong oxidizing hydroxyl radicals, and is considered to be one of the most powerful technologies for treating refractory wastewater. Fenton oxidation technology has the characteristics of wide application range and mild reaction conditions. However, the reaction needs to be carried out under strict acidic conditions and consumes a large amount of reagents. In the end, a large amount of iron-containing sludge (Fenton iron sludge) will be produced, which will bring higher disposal costs and restrict the further promotion and application of Fenton oxidation technology.

[0003] In order to solve the problems of high sludge production and high disposal cost caused by homogeneous Fenton oxidation technology, heterogeneous Fenton oxidation technology, namely Fenton-like oxidation technology, has been widely studied. It has the advantages of a wide pH adaptability range and low sludge production. Among many Fenton-like catalysts, iron-based catalysts have attracted the attention of many researchers because of their non-toxicity, easy availability and high efficiency. However, the preparation process of most iron-based catalysts is relatively complicated, especially nano-scale ones, which involve more reagents. Some are also washed with organic solvents, which have high preparation costs and produce secondary pollution. These shortcomings restrict the application of these catalysts. At present, many Fenton-like catalysts have higher pH adaptability and better catalytic oxidation performance when treating difficult-to-degrade simulated wastewater, but the effect is very poor when applied to actual wastewater. The main reason is that the actual wastewater is complex in composition and contains many macromolecular organic substances. Such substances are difficult to remove from wastewater by catalytic oxidation alone, but can be easily removed from wastewater by coagulation and sedimentation. Therefore, when using Fenton-like methods to treat difficult-to-degrade actual wastewater, the catalyst is required to have a high catalytic oxidation effect and a coagulation and sedimentation effect, so that it has engineering application value.

[0004] When using biochemical technology to treat organic wastewater such as urban domestic sewage, a large amount of biochemical sludge will be produced. The treatment methods for these biochemical sludges are generally landfill or incineration, which are very costly. Biochemical sludge contains a high amount of organic matter and a certain amount of iron, so it can be considered for resource application. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a sludge-based iron-based catalyst and a preparation method and application thereof.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention is a method for preparing a sludge-based iron-based catalyst, comprising the following steps:

[0008] The Fenton iron mud and the biochemical sludge are dried, crushed and sieved respectively to obtain the Fenton iron mud dry material and the biochemical sludge dry material;

[0009] The Fenton iron sludge dry material and the biochemical sludge dry material are mixed, and then fully pyrolyzed under anaerobic conditions to obtain the sludge-based iron-based catalyst.

[0010] The second technical solution of the present invention is a sludge-based iron-based catalyst prepared by the above-mentioned preparation method.

[0011] The third technical solution of the present invention is a method for degrading landfill leachate MBR effluent by continuous Fenton process, comprising the following steps:

[0012] After adjusting the pH of the landfill leachate MBR effluent to be acidic, the effluent was mixed with the above-mentioned sludge-based iron-based catalyst and hydrogen peroxide, stirred for reaction for 1, allowed to stand, and the supernatant was collected;

[0013] Add hydrogen peroxide to the supernatant to carry out stirring reaction 2, then adjust the pH value of the reaction system, coagulate and precipitate, and complete the treatment of the MBR effluent of the landfill leachate;

[0014] The dosage of the sludge-based iron-based catalyst is 1-3 g / L; the turbidity of the supernatant is less than 20 NTU.

[0015] The present invention discloses the following technical effects:

[0016] The preparation method of the invention is simple, does not need to add chemical agents, and the raw material is waste mud, thus realizing resource utilization of waste treatment.

[0017] The iron-based catalyst prepared by the present invention has good performance and is applied to Fenton-like catalytic oxidation of refractory organic matter, and its treatment performance can achieve the effect of homogeneous Fenton treatment.

[0018] The present invention realizes a continuous Fenton process. Compared with a two-stage homogeneous Fenton process, the overall process flow is short, thus saving investment and operation costs.

[0019] The method provided by the invention has high feasibility, small investment, low risk, high organic matter removal rate, low mud production and low operating cost, and is worthy of popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 The electron microscope scanning images of the sludge-based iron-based catalyst prepared in the example at a magnification of 5000 times (a), 10000 times (b) and 20000 times (c);

[0022] Figure 2 The present invention is a process flow chart of the continuous Fenton process for degrading landfill leachate MBR effluent. DETAILED DESCRIPTION

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0025] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0026] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0027] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0028] Fenton iron sludge and biochemical sludge are both production wastes with high treatment costs and difficulties. Based on the concept of "treating waste with waste", the present invention utilizes the properties of Fenton iron sludge and biochemical sludge, makes scientific proportions, prepares an iron-based catalyst with good performance, replaces ferrous iron in homogeneous Fenton, and realizes the resource utilization of Fenton iron sludge and biochemical sludge.

[0029] The principle of the present invention is to decompose organic matter in Fenton iron mud and biochemical sludge under high temperature conditions to generate a large amount of reducing gas, and then reduce the trivalent iron in Fenton iron mud to low-valent iron. The method of the present invention can not only treat the refractory organic matter in the sludge, but also obtain a Fenton-like iron-based catalyst with good performance, and then use the prepared iron-based catalyst to treat refractory wastewater, which can achieve a treatment effect equivalent to that of homogeneous Fenton.

[0030] The first aspect of the present invention provides a method for preparing a sludge-based iron-based catalyst, comprising the following steps:

[0031] The Fenton iron mud and the biochemical sludge are dried, crushed and sieved respectively to obtain the Fenton iron mud dry material and the biochemical sludge dry material;

[0032] The Fenton iron sludge dry material and the biochemical sludge dry material are mixed, and then fully pyrolyzed under anaerobic conditions to obtain the sludge-based iron-based catalyst.

[0033] In some embodiments of the present invention, the Fenton iron sludge is a primary homogeneous Fenton iron sludge or other sludge with a high iron content; the iron content in the Fenton iron sludge is greater than or equal to 200 mg / g; the calorific value of the biochemical sludge is greater than or equal to 9000 J / g. The biochemical sludge of the present invention is derived from the filter press sludge of the urban domestic sewage plant, and can also be other biochemical process sludge, as long as the calorific value is greater than or equal to 9000 J / g.

[0034] The present invention does not make any special requirements on the drying temperature and time, and the conventional technical means for drying Fenton iron mud and biochemical sludge by those skilled in the art can be selected, for example: drying at 100° C. in a blast drying oven.

[0035] The present invention does not specifically limit the crushing method, and conventional technical means of those skilled in the art may be used, for example, crushing with a soil crusher or a ball mill.

[0036] In some embodiments of the present invention, the screening is through a 80-300 mesh sieve.

[0037] Since the Fenton iron sludge dry material and the biochemical sludge dry material need to undergo a solid phase reaction later, the smaller the particle size of the Fenton iron sludge dry material and the biochemical sludge dry material, the more complete the reaction. However, the smaller the particle size, the higher the cost. Therefore, the present invention preferably passes through a 100-150 mesh sieve.

[0038] In some embodiments of the present invention, the mass ratio of the Fenton iron sludge dry material to the biochemical sludge dry material is (1-3):1.

[0039] The iron content of Fenton iron sludge is much higher than that of biochemical sludge, and the lower calorific value of biochemical sludge (the present invention uses the lower calorific value to measure the organic matter content in the sludge) is much higher than that of Fenton iron sludge. Therefore, in the mixture, if the proportion of Fenton iron sludge is higher, the total iron content will be higher and the lower calorific value will be lower. The mixing ratio of Fenton iron sludge dry material and biochemical sludge dry material can also be estimated based on the total iron content and lower calorific value in the mixture. Generally, the ratio of the total iron content (mg / g) to the lower calorific value (kJ / g) after the two kinds of sludge are mixed is (30-50):1, and about 38:1 is preferred. After the two kinds of sludge are mixed, they are put into pyrolysis under anaerobic and closed conditions. The reducing gas generated by pyrolysis fully reacts with trivalent iron to reduce the trivalent iron to low-valent iron.

[0040] In the present invention, if the mass ratio of the Fenton iron mud dry material to the biochemical sludge dry material exceeds 3:1, after high-temperature pyrolysis, the obtained catalyst will be severely agglomerated, the specific surface area will be reduced, and the catalytic performance will be reduced.

[0041] In some embodiments of the present invention, the anaerobic condition is an inert gas atmosphere, and an oxygen-deficient environment formed by a sealed tank with only a small exhaust hole is also feasible; when it is an inert gas atmosphere, nitrogen is preferred; the flow rate of the nitrogen is 20 to 200 mL / min.

[0042] In some embodiments of the present invention, the pyrolysis temperature is 700°C to 900°C, and the time is 2.5 to 6 hours; the heating rate during pyrolysis is 100°C / 10min.

[0043] In the present invention, when the pyrolysis temperature is lower than 700°C, more organic matter cannot be pyrolyzed, and when it is higher than 900°C, the pyrolysis rate is faster, which is not conducive to the sufficient reaction of the generated reducing gas with the high-valent iron. In addition, within the pyrolysis temperature range and the mass ratio range of the Fenton iron mud dry material and the biochemical sludge dry material, the obtained catalyst will not be agglomerated, is easy to break, and has high catalytic performance.

[0044] In the present invention, full pyrolysis means that the content of gases such as hydrogen and carbon monoxide in the flue gas produced by pyrolysis is very low, almost non-existent. The present invention uses the content of hydrogen in the flue gas less than 0.03% (when the nitrogen flow rate is 20mL / min) as a sign of full pyrolysis. The mass mixing ratio of Fenton iron mud dry material to biochemical sludge dry material is in the range of (1 to 3): 1. It is fully pyrolyzed at 700°C, and the full pyrolysis time is 4h to 5h; it is fully pyrolyzed at 800°C, and the full pyrolysis time is 4h to 4.5h; it is fully pyrolyzed at 900°C, and the full pyrolysis time is 2.5h to 6h. The higher the proportion of biochemical sludge, the longer the time of full pyrolysis, and vice versa. The catalyst prepared under the conditions of the present invention has a volatile content of almost 0 detected by an automatic industrial analyzer, that is, almost all organic matter is pyrolyzed.

[0045] In some embodiments of the present invention, after the pyrolysis is completed, the steps of cooling to room temperature and crushing the obtained product are also included.

[0046] A second aspect of the present invention provides a sludge-based iron-based catalyst prepared by the above-mentioned preparation method.

[0047] The third aspect of the present invention provides a method for degrading landfill leachate MBR effluent by a continuous Fenton process, comprising the following steps:

[0048] After adjusting the pH of the landfill leachate MBR effluent to be acidic, the effluent was mixed with the above-mentioned sludge-based iron-based catalyst and hydrogen peroxide, stirred for reaction for 1, allowed to stand, and the supernatant was collected;

[0049] Add hydrogen peroxide to the supernatant to carry out stirring reaction 2, then adjust the pH value of the reaction system, coagulate and precipitate, and complete the treatment of the MBR effluent of the landfill leachate;

[0050] The dosage of the sludge-based iron-based catalyst is 1-3 g / L; the turbidity of the supernatant is less than 20 NTU.

[0051] In some embodiments of the present invention, the COD of the landfill leachate MBR effluent is 1000-1500 mg / L, the TOC is 300-450 mg / L, and the chromaticity is 3500-6000.

[0052] In some embodiments of the present invention, adjusting the pH of the landfill leachate MBR effluent to be acidic is adjusting the pH to 1-3.

[0053] In some embodiments of the present invention, after adjusting the pH of the landfill leachate MBR effluent to acidic, when it is mixed with the sludge-based iron-based catalyst and hydrogen peroxide, the dosage of hydrogen peroxide is 2-4 mL / L; the mass concentration of the hydrogen peroxide is 30%.

[0054] In some embodiments of the present invention, the stirring reaction 1 is carried out at room temperature, at a stirring rate of 200 to 350 r / min, and for a time of 10 to 120 min.

[0055] In the present invention, after the stirring reaction 1 is completed, the unconsumed catalyst can be recovered by a magnet (the catalyst prepared by the present invention contains a large amount of low-valent iron that can be dissolved by acid, and some of it will be consumed during the Fenton-like reaction, with a general recovery rate of 25-35%) to achieve the recycling of the catalyst.

[0056] In the present invention, after the first catalyst catalytic degradation, the COD removal rate in the supernatant is 75% to 90%, and the residue is 150 to 350 mg / L; the TOC removal rate is 65% to 90%, and the residue is 50 to 85 mg / L. The removal rates of COD and TOC are higher than those of catalysts of other methods in the art (less than 70%), and the amount of sludge produced is about 1 / 3 of that of conventional homogeneous Fenton.

[0057] In some embodiments of the present invention, when hydrogen peroxide is added to the supernatant to carry out stirring reaction 2, the amount of hydrogen peroxide added is 0.3-1.5 mL / L.

[0058] After the organic wastewater is degraded by the continuous Fenton process of the present invention (the process flow is: raw water - pH adjustment - Fenton-like - precipitation - homogeneous Fenton (only adding hydrogen peroxide) - pH adjustment - coagulation - precipitation - effluent), the effluent water quality can directly meet the first-level standard (≤100mg / L) of the national comprehensive sewage discharge standard, and the effluent COD is about 80-95mg / L. Compared with the two-stage homogeneous Fenton process (the process flow is: raw water - pH adjustment - homogeneous Fenton - pH adjustment - coagulation - precipitation - pH adjustment - homogeneous Fenton - pH adjustment - coagulation - precipitation - effluent), two unit operations such as pH adjustment and coagulation after the first-stage Fenton are omitted, saving investment and operating costs. The continuous Fenton process provided by the present invention is suitable for difficult-to-degrade wastewater that requires secondary Fenton treatment.

[0059] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0060] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0061] Materials and wastewater in the embodiments: Fenton iron mud is the first-level Fenton iron mud of the homogeneous Fenton process of the MBR process effluent of a landfill leachate; biochemical sludge is the filter press sludge of a city domestic sewage treatment plant; wastewater is the effluent of the MBR process of a landfill leachate. The physical and chemical properties of the Fenton iron mud after drying and crushing through a 100-mesh sieve (i.e., Fenton iron mud dry material) are: moisture content 8%, calorific value 2.81kJ / g, and iron content 284.24mg / g. The physical and chemical properties of the biochemical sludge after drying and crushing through a 100-mesh sieve (i.e., biochemical sludge dry material) are: moisture content 3.5%, calorific value 10.07kJ / g, and iron content 18.36mg / g. Wastewater quality: COD is 1000-1500mg / L, TOC is 300-450mg / L, chromaticity is 3500-6000, and pH is about 7.

[0062] Example 1

[0063] The mass ratio of Fenton iron sludge dry material to biochemical sludge dry material is 7:3. The mixture is placed in a covered crucible and then pushed into a tube furnace. Then, it is pyrolyzed at 700℃ for 4.5h under the protection of nitrogen with a heating rate of 100℃ / 10min and a flow rate of 150mL / min. After the pyrolysis is fully completed, it is cooled to room temperature, and the prepared catalyst is put into a sealed bag and crushed by hand to obtain a sludge-based iron-based catalyst (hereinafter referred to as catalyst).

[0064] Take 1L of wastewater (COD is 1100mg / L, TOC is 310mg / L) and pour it into a 2L beaker. Use mechanical stirring at a stirring rate of 200r / min, adjust the pH to 2, then add 2.5g / L of catalyst, and then add 2.5mL of hydrogen peroxide with a mass concentration of 30%, and stir for 0.5h. After the reaction is completed, use a magnet to suck back the catalyst that has not been consumed, and then let it stand for 1h. Then take a certain amount of supernatant in a 50mL centrifuge tube, adjust the pH to about 8.5 with alkali solution, and then centrifuge (speed is 4500r / min) for 10min. After centrifugation, filter with a needle filter membrane with a pore size of 0.45μm, and the filtrate is loaded into a covered glass tube, and then water bathed for 30min (water bath temperature is 50℃), and then detect COD and TOC. After testing, the COD of the wastewater was 223.3 mg / L, and the removal rate was 79.7%; the TOC was 91.76 mg / L, and the removal rate was 70.4%.

[0065] The wastewater after the reaction was allowed to stand overnight to obtain a supernatant with a turbidity of about 3.7 NTU. Take 0.5L of the supernatant, add 0.8mL of 30% hydrogen peroxide to carry out the Fenton reaction, the stirring rate is 200r / min, and the reaction time is 30min. After the reaction is completed, stand for 30min, then take a certain amount of the supernatant in a 50mL centrifuge tube, adjust the pH to about 8.5 with alkali solution, and then centrifuge (speed is 4500r / min) for 10min. After the centrifugation is completed, filter with a needle filter membrane with a pore size of 0.45μm, and the obtained filtrate is loaded into a covered glass tube, and then water bathed for 30min (water bath temperature is 50℃), and then detect COD and TOC. After testing, the COD of the final filtrate is 88.2mg / L and the TOC is 47.6mg / L. COD is less than 100mg / L, reaching the first-level standard of the national comprehensive sewage discharge standard (≤100mg / L).

[0066] Example 2

[0067] The mass ratio of Fenton iron sludge dry material to biochemical sludge dry material is 2:1. The mixture is placed in a covered crucible and then pushed into a tube furnace. Then, the mixture is pyrolyzed at 800°C for 4.5h under nitrogen protection at a heating rate of 100°C / 10min and a flow rate of 100mL / min. After sufficient pyrolysis, the mixture is cooled to room temperature, and the prepared catalyst is put into a sealed bag and crushed by hand to obtain a sludge-based iron-based catalyst (hereinafter referred to as catalyst).

[0068] Take 1L of wastewater (COD is 1200mg / L, TOC is 340mg / L) and pour it into a 2L beaker. Stir it mechanically at a stirring rate of 250r / min, adjust the pH to 1.5, then add 2.2g / L of catalyst, add 2mL of 30% hydrogen peroxide, and stir for 1h. After the reaction is completed, use a magnet to suck back the catalyst that has not been consumed, let it settle for 1h, then take a certain amount of supernatant in a 50mL centrifuge tube, adjust the pH to about 8.5 with alkali solution, and then centrifuge (speed is 4500r / min) for 10min. After centrifugation, filter it with a needle filter membrane with a pore size of 0.45μm, and the filtrate is placed in a covered glass tube, then water bathed for 30min (water bath temperature is 50℃), and then detect COD and TOC. After testing, the COD of the wastewater was 204.9 mg / L, and the removal rate was 82.9%; the TOC was 49.3 mg / L, and the removal rate was 85.5%.

[0069] The wastewater after the reaction was allowed to stand overnight to obtain a supernatant with a turbidity of about 20NTU. Take 0.5L of the supernatant, add 0.6mL of 30% hydrogen peroxide to carry out Fenton reaction, the stirring rate is 200r / min, and the reaction time is 30min. After the reaction is completed, stand for 30min, then take a certain amount of supernatant in a 50mL centrifuge tube, adjust the pH to about 8.5 with alkali solution, and then centrifuge (speed is 4500r / min) for 10min. After the centrifugation is completed, filter with a needle filter membrane with a pore size of 0.45μm, and the obtained filtrate is loaded into a covered glass tube, and then water bathed for 30min (water bath temperature is 50℃), and then detect COD and TOC. After testing, the COD of the final filtrate is 93.1mg / L and the TOC is 37.6mg / L. COD is less than 100mg / L, reaching the first-level standard of the national comprehensive sewage discharge standard (≤100mg / L).

[0070] Example 3

[0071] The mass ratio of Fenton iron sludge dry material to biochemical sludge dry material is 3:2. The mixture is placed in a covered crucible and then pushed into a tube furnace. Then, it is pyrolyzed at 900℃ for 6h under nitrogen protection with a heating rate of 100℃ / 10min and a flow rate of 180mL / min. After sufficient pyrolysis, it is cooled to room temperature, and the prepared catalyst is put into a sealed bag and crushed by hand to obtain a sludge-based iron-based catalyst (hereinafter referred to as catalyst).

[0072] Take 1L of wastewater (COD is 1050mg / L, TOC is 330mg / L) and pour it into a 2L beaker. Use mechanical stirring at a stirring rate of 250r / min, adjust the pH to 2.5, then add 3.0g / L of catalyst, and then add 3.0mL of 30% hydrogen peroxide, and stir for 2h. After the reaction is completed, use a magnet to suck back the catalyst that has not been consumed, let it settle for 1h, then take a certain amount of supernatant in a 50mL centrifuge tube, adjust the pH to about 8.5 with alkali solution, and then centrifuge (speed is 4500r / min) for 10min. After centrifugation, filter with a needle filter membrane with a pore size of 0.45μm, and the filtrate is loaded into a covered glass tube, and then water bathed for 30min (water bath temperature is 50℃), and then detect COD and TOC. After testing, the COD of the wastewater was 229.1 mg / L, and the removal rate was 78.2%; the TOC was 50.6 mg / L, and the removal rate was 84.7%.

[0073] The wastewater after the reaction was allowed to stand overnight to obtain a supernatant with a turbidity of about 15 NTU. Take 0.5L of the supernatant, add 0.4mL of 30% hydrogen peroxide to carry out Fenton reaction, the stirring rate is 200r / min, and the reaction time is 30min. After the reaction is completed, stand for 20min, then take a certain amount of supernatant in a 50mL centrifuge tube, adjust the pH to about 8.5 with alkali solution, and then centrifuge (speed is 4500r / min) for 10min. After the centrifugation is completed, filter with a needle filter membrane with a pore size of 0.45μm, and the obtained filtrate is loaded into a covered glass tube, and then water bathed for 30min (water bath temperature is 50℃), and then detect COD and TOC. After testing, the COD of the final filtrate is 91.1mg / L and the TOC is 39.2mg / L. COD is less than 100mg / L, reaching the first-level standard of the national comprehensive sewage discharge standard (≤100mg / L).

[0074] Figure 1 The scanning electron microscope image of the sludge-based iron-based catalyst prepared in Example 1. It can be seen that the prepared catalyst is relatively mixed, but there are a large number of crystalline substances, the particle diameters of these substances vary greatly, and they also contain impurities. The main reason is that the raw materials are all sludge and have more impurities. From (b) and (c), it can be seen that the catalyst contains a large number of crystalline substances. The analysis of such crystalline substances by energy spectrometer shows that the main components are iron (65% to 80%) and carbon (20%-35%), as well as a small amount of impurities such as silicon. The other unshaped substances in the catalyst are analyzed by energy spectrometer, and the main components are iron (20% to 58%), carbon (30% to 38%), oxygen (5.5% to 33%), silicon (0.5% to 2.8%), potassium (0.4% to 1.2%), calcium (0.2% to 0.5%), sodium (0.6% to 4.3%), phosphorus (0.6% to 3.1%) and other elements. It can be deduced from this that the catalyst prepared by the present invention contains a large amount of iron-carbon compounds, and the components may be zero-valent iron, iron carbide, etc. In the Fenton-like reaction, a lot of zero-valent iron will react with the acid to form ferrous iron to complete the catalytic oxidation reaction. In addition, it also contains more iron oxides, which can also promote the Fenton reaction. Therefore, the catalyst prepared by the present invention can produce a large amount of ferrous iron when performing a Fenton-like reaction, and together with other iron oxides, it can promote the Fenton reaction. It can also produce a large amount of iron ions, which will have a strong coagulation and precipitation effect after the reaction is completed, and further remove organic matter in the water, which is different from other pure catalytic oxidation Fenton-like catalysts. Therefore, the catalyst prepared by the present invention can be effectively applied to the treatment of actual wastewater, and experiments have also proved that the treatment effect on the effluent of the MBR of the landfill leachate is better than that of the secondary homogeneous Fenton and other Fenton-like treatments.

[0075] Depend on Figure 2It can be seen from the process flow chart that in the continuous Fenton process of the present invention, the iron element can be recycled, the entire process has almost no solid waste discharge, and a certain amount of biochemical sludge is also consumed.

[0076] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a sludge-based iron-based catalyst, characterized in that: The following steps are involved: The Fenton iron mud and the biochemical sludge are dried, crushed and sieved respectively to obtain the Fenton iron mud dry material and the biochemical sludge dry material; The Fenton iron sludge dry material and the biochemical sludge dry material are mixed, and then fully pyrolyzed under anaerobic conditions to obtain the sludge-based iron-based catalyst.

2. The method for preparing the sludge-based iron-based catalyst according to claim 1, characterized in that: The iron content in the Fenton iron mud is greater than or equal to 200 mg / g; the calorific value of the biochemical sludge is greater than or equal to 9000 J / g.

3. The method for preparing the sludge-based iron-based catalyst according to claim 1, characterized in that: The sieving is through a 80-300 mesh sieve.

4. The method for preparing the sludge-based iron-based catalyst according to claim 1, characterized in that: The mass ratio of the Fenton iron sludge dry material to the biochemical sludge dry material is (1-3):1; or after the Fenton iron sludge dry material and the biochemical sludge dry material are mixed, the ratio of the total iron content to the lower calorific value in the mixture is (30-50) mg / g:1 kJ / g.

5. The method for preparing the sludge-based iron-based catalyst according to claim 1, characterized in that: The oxygen-free condition is an inert gas atmosphere.

6. The method for preparing the sludge-based iron-based catalyst according to claim 1, characterized in that: The pyrolysis temperature is 700° C. to 900° C., the sufficient pyrolysis time is 2.5 to 6 hours, and the heating rate during pyrolysis is 100° C. / 10 minutes.

7. The method for preparing the sludge-based iron-based catalyst according to claim 1, characterized in that: After the pyrolysis is completed, the process further includes cooling the product to room temperature and crushing the product.

8. A sludge-based iron-based catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. A method for degrading landfill leachate MBR effluent by continuous Fenton process, characterized in that: The following steps are involved: After adjusting the pH of the landfill leachate MBR effluent to be acidic, the effluent is mixed with the sludge-based iron-based catalyst and hydrogen peroxide as claimed in claim 8, stirred for reaction for 1, allowed to stand, and the supernatant is collected; Add hydrogen peroxide to the supernatant to carry out stirring reaction 2, then adjust the pH value of the reaction system, coagulate and precipitate, and complete the treatment of the MBR effluent of the landfill leachate; The dosage of the sludge-based iron-based catalyst is 1-3 g / L; the turbidity of the supernatant is less than 20 NTU.

10. The method for degrading landfill leachate MBR effluent by continuous Fenton process according to claim 9, characterized in that: The COD of the landfill leachate MBR is 1000-1500 mg / L, the TOC is 300-450 mg / L, and the chromaticity is 3500-6000.

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