A sludge-based iron-based catalyst and its preparation method and application

Abstract

The present invention provides a sludge-based iron-based catalyst, 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: drying, crushing and sieving Fenton iron sludge and biochemical sludge respectively to obtain Fenton iron sludge dry material and biochemical sludge dry material; mixing the Fenton iron sludge dry material and the biochemical sludge dry material, and then pyrolyzing them under anaerobic conditions to obtain the sludge-based iron-based catalyst. The preparation method of the present invention is simple, does not require chemical agents, and the raw material is waste sludge, which realizes waste treatment with waste. The catalyst prepared by the present invention can efficiently degrade the effluent of landfill leachate MBR.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts 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 generated. It is difficult to treat with general coagulation and biochemical technologies and requires advanced oxidation technology for treatment, including Fenton oxidation technology. Fenton oxidation technology can degrade organic matter by producing highly 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 a wide range of applications 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 brings high disposal costs and restricts the further promotion and application of Fenton oxidation technology.

[0003] To address the high sludge production and disposal costs associated with homogeneous Fenton oxidation technology, heterogeneous Fenton oxidation technology, also known as Fenton-like oxidation technology, has been extensively studied. It offers advantages such as a wide pH range and low sludge production. Among the various Fenton-like catalysts, iron-based catalysts have attracted considerable attention due to their non-toxicity, availability, and high efficiency. However, the preparation processes for most iron-based catalysts, especially nanoscale ones, are complex, involving numerous reagents. Some also require organic solvent washing, resulting in high preparation costs and the generation of secondary pollution. These limitations restrict the application of these catalysts. Currently, many Fenton-like catalysts exhibit high pH adaptability and excellent catalytic oxidation performance when treating refractory simulated wastewater. However, their performance is poor when applied to real wastewater. This is primarily due to the complex composition of real wastewater, which contains many large organic molecules. These compounds are difficult to remove from the wastewater by catalytic oxidation alone, but can be more easily removed by coagulation and sedimentation. Therefore, when using Fenton-like methods to treat real refractory wastewater, the catalyst must possess both high catalytic oxidation and coagulation and sedimentation properties to be viable for engineering applications.

[0004] When using biochemical technologies to treat organic wastewater, such as municipal sewage, large amounts of biochemical sludge are produced. This sludge is typically disposed of by landfill or incineration, both of which are very costly. However, biochemical sludge contains a high concentration of organic matter and a certain amount of iron, making it a viable resource for recycling. 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 Fenton iron mud dry material and 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 preparation method.

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

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

[0013] Adding hydrogen peroxide to the supernatant to carry out stirring reaction 2, then adjusting the pH value of the reaction system, coagulation and precipitation, and completing the treatment of the landfill leachate MBR effluent;

[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 present invention is simple, does not require the addition of chemical agents, and the raw material is waste mud, thus realizing resource utilization by treating waste with waste.

[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 shorter, and investment and operation costs are saved.

[0019] The method provided by the present invention has high feasibility, small investment, low risk, high organic matter removal rate, low mud production and low operating cost, and is worthy of promotion 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 following briefly introduces the drawings required for use in the embodiments. 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 any creative work.

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

[0022] Figure 2 This is a process flow chart for the continuous Fenton process of the present invention to degrade 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 rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

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

[0025] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 any conflict with any incorporated document, the contents 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 described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be 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] Both Fenton iron sludge and biochemical sludge are production wastes with high treatment costs and difficulties. Based on the concept of "treating waste with waste", this invention utilizes the properties of Fenton iron sludge and biochemical sludge, adopts a scientific ratio, and prepares a high-performance iron-based catalyst to replace the ferrous iron in homogeneous Fenton, realizing 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 sludge and biochemical sludge under high temperature conditions, generating a large amount of reducing gas, and then reducing the trivalent iron in the Fenton iron sludge to low-valent iron. This method can not only treat the difficult-to-degrade organic matter in the sludge, but also produce a high-performance Fenton-like iron-based catalyst. The prepared iron-based catalyst can then be used to treat difficult-to-degrade wastewater, achieving treatment results comparable to homogeneous Fenton.

[0030] A 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 Fenton iron mud dry material and 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; and 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 filter press sludge from a municipal sewage treatment plant, or may 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. Conventional technical means for drying Fenton iron mud and biochemical sludge can be used by those skilled in the art, for example, drying in a blast drying oven at 100°C.

[0035] The present invention does not impose any particular limitation on the crushing method, and conventional technical means used by those skilled in the art may be used, for example, crushing using a soil crusher or a ball mill.

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

[0037] Since the Fenton iron sludge dry material and the biochemical sludge dry material need to undergo 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 content of organic matter 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 types of sludge are mixed is (30-50):1, and about 38:1 is optimal. After the two types 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 compacted, the specific surface area will be reduced, and the catalytic performance will be reduced.

[0041] In some embodiments of the present invention, the oxygen-free condition is an inert gas atmosphere. 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. / 10 min.

[0043] In the present invention, pyrolysis temperatures below 700°C prevent a significant amount of organic matter from being decomposed, while temperatures above 900°C result in a rapid pyrolysis rate, hindering the sufficient reaction of the generated reducing gas with the high-valent iron. Furthermore, within this pyrolysis temperature range and the mass ratio of dry Fenton iron sludge to dry biochemical sludge, the resulting catalyst exhibits high catalytic performance, resists caking and easy breakage.

[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 a hydrogen content in the flue gas of less than 0.03% (at a nitrogen flow rate of 20 mL / 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 (1-3):1. Full pyrolysis is achieved at 700°C, with a full pyrolysis time of 4h-5h; at 800°C, with a full pyrolysis time of 4h-4.5h; and at 900°C, with a full pyrolysis time of 2.5h-6h. The higher the proportion of biochemical sludge, the longer the full pyrolysis time, and vice versa. The catalyst prepared using the conditions described in the present invention has a volatile matter content of almost 0 detected by an automatic industrial analyzer, indicating that almost all organic matter has been pyrolyzed.

[0045] In some embodiments of the present invention, after the pyrolysis is completed, the process further comprises cooling the product to room temperature and crushing the product.

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

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

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

[0049] Adding hydrogen peroxide to the supernatant to carry out stirring reaction 2, then adjusting the pH value of the reaction system, coagulation and precipitation, and completing the treatment of the landfill leachate MBR effluent;

[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 amount of hydrogen peroxide added 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 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 process, with a general recovery rate of 25-35%), thereby realizing the recycling of the catalyst.

[0056] In the present invention, after the first catalytic degradation, the COD removal rate in the supernatant is 75% to 90%, with a residual of 150 to 350 mg / L; the TOC removal rate is 65% to 90%, with a residual of 50 to 85 mg / L. These COD and TOC removal rates are higher than those achieved by other catalysts in the art (less than 70%), while the amount of sludge produced is approximately one-third that of conventional homogeneous Fenton.

[0057] In some embodiments of the present invention, hydrogen peroxide is added to the supernatant to carry out stirring reaction for 2 hours, and 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 hydrogen peroxide is added) - pH adjustment - coagulation - precipitation - effluent), the effluent water quality can directly meet the first-level standard (≤100 mg / L) of the national comprehensive sewage discharge standard, and the effluent COD is about 80-95 mg / 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), the two unit operations of 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 two-stage Fenton treatment.

[0059] Unless otherwise specified, the technical solutions described in the present invention are all conventional solutions in the field, 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 illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0061] Materials and wastewater in the examples: Fenton iron sludge, a first-stage homogeneous Fenton process, is derived from the effluent of a landfill leachate MBR process; biochemical sludge is filter press sludge from a municipal sewage treatment plant; and wastewater is derived from the effluent of a landfill leachate MBR process. The physicochemical properties of the dried, crushed Fenton iron sludge (i.e., dry Fenton iron sludge) after passing through a 100-mesh sieve (i.e., dry Fenton iron sludge) are: 8% moisture content, calorific value 2.81 kJ / g, and iron content 284.24 mg / g. The physicochemical properties of the dried, crushed biochemical sludge (i.e., dry biochemical sludge) after passing through a 100-mesh sieve are: 3.5% moisture content, calorific value 10.07 kJ / g, and iron content 18.36 mg / g. Wastewater quality: COD is 1000-1500 mg / L, TOC is 300-450 mg / L, chromaticity is 3500-6000, and pH is about 7.

[0062] Example 1

[0063] The mass ratio of dry Fenton iron sludge to dry biochemical sludge was 7:3. The mixture was placed in a covered crucible and then pushed into a tube furnace. Pyrolysis was then carried out at 700°C for 4.5 hours under a nitrogen atmosphere at a heating rate of 100°C / 10 min and a flow rate of 150 mL / min. After full pyrolysis, the mixture was cooled to room temperature, and the prepared catalyst was placed in a sealed bag and crushed by hand to obtain the sludge-based iron catalyst (hereinafter referred to as the 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 to adjust the pH to 2, then add 2.5g / L of catalyst, add 2.5mL of hydrogen peroxide with a mass concentration of 30%, and stir the reaction 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 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 is complete, filter with a needle filter membrane with a pore size of 0.45μm, and the filtrate obtained is placed in a glass tube with a lid, then water bath 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, with a removal rate of 79.7%; the TOC was 91.76 mg / L, with a removal rate of 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. 0.5 L of supernatant was taken and 0.8 mL of 30% hydrogen peroxide was added to carry out the Fenton reaction. The stirring rate was 200 r / min and the reaction time was 30 min. After the reaction was completed, the supernatant was allowed to stand for 30 min, and then a certain amount of supernatant was taken in a 50 mL centrifuge tube. The pH was adjusted to about 8.5 with alkali solution, and then centrifuged (rotating speed was 4500 r / min) for 10 min. After the centrifugation was completed, the filtrate was filtered with a needle filter membrane having a pore size of 0.45 μm. The filtrate was then placed in a covered glass tube and placed in a water bath for 30 min (the water bath temperature was 50°C) to detect COD and TOC. After testing, the COD of the final filtrate was 88.2 mg / L and the TOC was 47.6 mg / L. The COD was less than 100 mg / L, reaching the first-level standard (≤100 mg / L) of the national comprehensive sewage discharge standard.

[0066] Example 2

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

[0068] Take 1L of wastewater (COD is 1200mg / L, TOC is 340mg / L) and pour it into a 2L beaker. Use mechanical stirring at a stirring rate of 250r / min to adjust the pH to 1.5. Then add 2.2g / L of catalyst and 2mL of 30% hydrogen peroxide. Stir and react for 1h. After the reaction is complete, 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. Use alkali solution to adjust the pH to about 8.5. Then centrifuge (speed is 4500r / min) for 10min. After centrifugation, filter with a needle filter with a pore size of 0.45μm. The filtrate obtained is placed in a glass tube with a lid and placed in a water bath for 30min (water bath temperature is 50℃). Then detect COD and TOC. After testing, the COD of the wastewater was 204.9 mg / L, with a removal rate of 82.9%; the TOC was 49.3 mg / L, with a removal rate of 85.5%.

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

[0070] Example 3

[0071] The mass ratio of Fenton iron sludge to biochemical sludge was 3:2. The mixture was placed in a covered crucible and then pushed into a tube furnace. Pyrolysis was then carried out at 900°C for 6 hours under a nitrogen atmosphere at a heating rate of 100°C / 10 minutes and a flow rate of 180 mL / min. After full pyrolysis, the mixture was cooled to room temperature, and the prepared catalyst was placed in a sealed bag and crushed by hand to obtain the sludge-based iron catalyst (hereinafter referred to as the 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 to adjust the pH to 2.5. Then add 3.0g / L of catalyst and 3.0mL of 30% hydrogen peroxide. Stir and react for 2h. After the reaction is complete, 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. Use alkali solution to adjust the pH to about 8.5. Then centrifuge (speed is 4500r / min) for 10min. After centrifugation, filter with a needle filter with a pore size of 0.45μm. The filtrate obtained is placed in a covered glass tube and water bathed for 30min (water bath temperature is 50℃). Then detect COD and TOC. After testing, the COD of the wastewater was 229.1 mg / L, with a removal rate of 78.2%; the TOC was 50.6 mg / L, with a removal rate of 84.7%.

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

[0074] Figure 1 This is a 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 contains a large amount of crystalline material. The particle diameters of these materials vary greatly and they also contain impurities. This is mainly due to the fact that the raw materials are all sludge, which is high in impurities. As can be seen from (b) and (c), the catalyst contains a large amount of crystalline material. Energy dispersive spectrometer analysis of these crystalline materials reveals that their main components are iron (65%-80%) and carbon (20%-35%), with small amounts of impurities such as silicon. Energy dispersive spectrometer analysis of other amorphous materials in the catalyst reveals that the main components are iron (20%-58%), carbon (30%-38%), oxygen (5.5%-33%), silicon (0.5%-2.8%), potassium (0.4%-1.2%), calcium (0.2%-0.5%), sodium (0.6%-4.3%), and phosphorus (0.6%-3.1%). It can be inferred from this that the catalyst prepared by the present invention contains a large amount of iron-carbon compounds, which may be composed of zero-valent iron, iron carbide, etc. During 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 a large amount of iron oxides, which can also promote the Fenton reaction. Therefore, when the catalyst prepared by the present invention undergoes a Fenton-like reaction, it can not only produce a large amount of ferrous iron, but also other iron oxides to promote the Fenton reaction together. It can also produce a large amount of iron ions. After the reaction is completed, it will have a strong coagulation and precipitation effect, further removing organic matter from 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. Experiments have also proved that the treatment effect of the effluent from the landfill leachate MBR is better than that of the secondary homogeneous Fenton and other Fenton-like treatments.

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

[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 principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for degrading landfill leachate MBR effluent using a continuous Fenton process, characterized in that: The following steps are involved: After adjusting the pH of the landfill leachate MBR effluent to acidic, it is mixed with the sludge-based iron-based catalyst and hydrogen peroxide, stirred for reaction for 1 minute, allowed to stand, and the supernatant is collected; Adding hydrogen peroxide to the supernatant to carry out stirring reaction 2, then adjusting the pH value of the reaction system, coagulating and settling, and completing the treatment of the landfill leachate MBR effluent; The dosage of the sludge-based iron-based catalyst is 1 to 3 g / L; the turbidity of the supernatant is less than 20 NTU; The preparation method of the sludge-based iron-based catalyst comprises the following steps: The Fenton iron mud and the biochemical sludge are dried, crushed and sieved respectively to obtain Fenton iron mud dry material and biochemical sludge dry material; Mixing the Fenton iron sludge dry material and the biochemical sludge dry material, and then fully pyrolyzing them under anaerobic conditions to obtain the sludge-based iron-based catalyst; 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; After the Fenton iron mud 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; The pyrolysis temperature is 700° C. to 900° C., the full pyrolysis time is 2.5 to 6 hours, and the heating rate during pyrolysis is 100° C. / 10 minutes.

2. The method for degrading landfill leachate MBR effluent by continuous Fenton process according to claim 1, characterized in that: The sieving is through an 80-300 mesh sieve.

3. The method for degrading landfill leachate MBR effluent by continuous Fenton process according to claim 1, characterized in that: The oxygen-free condition is an inert gas atmosphere.

4. The method for degrading landfill leachate MBR effluent by continuous Fenton process 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.

5. The method for degrading landfill leachate MBR effluent by continuous Fenton process according to claim 1, 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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