A magnetic heterogeneous catalyst, its preparation method and application

Abstract

This application discloses a magnetic heterogeneous catalyst, its preparation method, and its application, belonging to the field of wastewater treatment catalyst technology. The magnetic heterogeneous catalyst combines high catalytic activity with magnetic recovery characteristics, allowing it to be reused more than 10 times in the treatment of high-concentration, recalcitrant organic wastewater, reducing iron loss and sludge generation. It also broadens the applicable pH range (pH 3-8), making it suitable for industrial park wastewater treatment plants and enterprises discharging high-concentration organic wastewater (such as pharmaceutical factories and dyeing plants). It boasts advantages such as compact equipment and low operating costs (<0.8 RMB / ton of water), demonstrating significant market potential. Given the current stringent environmental policies for recalcitrant wastewater treatment, this technology is expected to become a benchmark for next-generation advanced oxidation technologies.

Description

Technical Field

[0001] This application relates to a magnetic heterogeneous catalyst, its preparation method and application, belonging to the field of wastewater treatment catalyst technology. Background Technology

[0002] For the treatment of high-concentration, recalcitrant organic wastewater (such as pharmaceutical, dye, and pesticide wastewater), the traditional Fenton process suffers from problems such as strong pH dependence (requiring acidic conditions), secondary pollution from iron sludge, and low H2O2 utilization. While heterogeneous Fenton processes can alleviate some of these problems, catalyst recovery is difficult and activity easily decays. Electro-Fenton processes, although capable of producing H2O2 and Fe in situ... 2+ However, the electrodes are prone to passivation and consume a lot of energy. Existing technologies such as photo-Fenton and ultrasonic Fenton can improve efficiency, but the equipment is complex and expensive. Therefore, there is an urgent need for a new Fenton technology that is efficient, energy-saving, easy to operate, and whose catalyst can be reused. Summary of the Invention

[0003] To address the problems of high cost, complex processes, and poor catalyst recoverability in existing wastewater treatment technologies, this application proposes a magnetic heterogeneous catalyst technology. This technology uses magnetic Fe3O4 nanoparticles as the core, coated with mesoporous activated carbon and loaded with transition metals (such as Cu-Mn bimetals), with stability enhanced by EDTA chelation. The catalyst in this application combines high catalytic activity with magnetic recovery characteristics, allowing for reuse more than 10 times, reducing iron loss and sludge generation, and also broadening the applicable pH range (pH 3-8).

[0004] The technical solution adopted in this application is as follows:

[0005] According to a first aspect of this application, a magnetic heterogeneous catalyst is provided, comprising a composite support for supporting active components and a surface modification layer covering the outside of the composite support for supporting active components.

[0006] The composite carrier is a magnetic carrier obtained by combining magnetic particles and activated carbon.

[0007] The magnetic particles are selected from at least one of Fe3O4 and CoFe2O4;

[0008] The active component is at least one of a transition metal or an oxide thereof;

[0009] The material of the surface modification layer is selected from at least one of EDTA, SiO2, and activated carbon.

[0010] Optionally, the magnetic heterogeneous catalyst has a magnetic strength ≥35 emu / g.

[0011] The main function of the surface modification layer made of EDTA, SiO2, and activated carbon is to isolate the magnetic core from corrosion by acidic / alkaline media and reduce the loss rate of iron ions.

[0012] According to a second aspect of this application, a method for preparing the above-mentioned magnetic heterogeneous catalyst is provided, comprising the following steps:

[0013] S1 provides magnetic nanoparticles;

[0014] S2. An aqueous solution containing magnetic nanoparticles and activated carbon precursor is placed in a sealed container and subjected to a hydrothermal reaction. The product of the hydrothermal reaction is then carbonized in an inactive atmosphere to obtain a composite carrier.

[0015] S3. The composite carrier is placed in a salt solution containing the active component for impregnation, and then the impregnated composite carrier is calcined in an oxygen-containing atmosphere to obtain a composite carrier loaded with the active component.

[0016] S4. A surface modification layer is formed on the outside of the composite support loaded with active components to obtain the magnetic heterogeneous catalyst.

[0017] Optionally, in step S1, the method for preparing the magnetic particles includes:

[0018] In an inactive atmosphere, an alkaline precipitant is added dropwise to a soluble salt solution containing the metal in the magnetic particles, and a co-precipitation reaction is carried out to obtain the magnetic nanoparticles.

[0019] Optionally, in step S2, the activated carbon precursor is selected from glucose;

[0020] In step S2, the carbonization temperature is 300~950°C.

[0021] Optionally, in step S3, the salt solution containing the active component is an aqueous solution comprising a soluble salt of at least one transition metal.

[0022] Optionally, in step S4, when the material of the surface modification layer is EDTA, the method for forming the surface modification layer includes the following steps:

[0023] The composite carrier loaded with active components was dispersed in 0.05 M EDTA solution at a solid-liquid ratio of 1 g: 100 mL, under conditions of pH 4-7, and stirred for 4-8 h. The product was then magnetically separated and dried.

[0024] In step S4, when the surface modification layer is made of SiO2, the method for forming the surface modification layer includes the following steps:

[0025] The composite carrier loaded with active components is dispersed in an alcohol-water mixture, then 25% ammonia water is added and mixed, ultrasonicated for 30-60 min, then TEOS is added dropwise, and stirred at 50-560°C for 6-8 h. The product is then magnetically separated, washed with alcohol and dried.

[0026] The solid-liquid ratio of the composite carrier loaded with active components, alcohol-water mixture, 25% ammonia solution, and TEOS is 1g:200mL:5mL:2mL.

[0027] In step S4, when the surface modification layer is made of activated carbon, the method for forming the surface modification layer includes the following steps:

[0028] The composite carrier loaded with active components and glucose were dispersed in water at a solid-liquid ratio of 1g:2g:50mL. The mixture was ultrasonically treated for 30-60 minutes, then placed in a sealed container and hydrothermally reacted at 180-200°C for 6-8 hours. The final product was carbonized in an inactive atmosphere at 500-700°C for 2-3 hours to form a carbon layer of 2-5nm.

[0029] According to a third aspect of this application, the above-mentioned magnetic heterogeneous catalyst and the magnetic heterogeneous catalyst prepared according to the above preparation method are provided for the treatment of high-concentration recalcitrant organic wastewater, wherein the treatment of high-concentration recalcitrant organic wastewater is carried out in a multi-stage fluidized bed reactor system under conditions assisted by electro-Fenton coupled ultrasound.

[0030] Optionally, the multi-stage fluidized bed reactor system includes:

[0031] The wastewater storage tank, pretreatment zone, primary fluidized bed reaction zone, electro-Fenton-ultrasonic coupling zone, secondary fluidized bed reaction zone, magnetic separation zone, and clear water tank are connected in series.

[0032] Catalyst regeneration tank, C&D, PLC controller;

[0033] The inlet of the catalyst regeneration tank is connected to the magnetic separation zone, and the outlet of the catalyst regeneration tank is connected to the primary fluidized bed reaction zone and the electro-Fenton-ultrasonic coupling zone, respectively.

[0034] The PLC controller is electrically connected to the pretreatment area, the electro-Fenton-ultrasonic coupling area, the magnetic separation area, and the C&D system.

[0035] The pretreatment zone includes a pH sensor for monitoring the acidity and alkalinity of wastewater, a dosing pump for adjusting the acidity and alkalinity of wastewater, and a mechanical bar for removing suspended solids.

[0036] The primary fluidized bed reaction zone is filled with the magnetic heterogeneous catalyst;

[0037] The electro-Fenton-ultrasound coupling region includes an electrochemical module and an ultrasound-assisted module, wherein the electrochemical module includes an iron-carbon micro-electrolysis anode and a three-dimensional graphene cathode.

[0038] The secondary fluidized bed reaction zone is equipped with inclined plates for assisting solid-liquid separation;

[0039] The magnetic separation zone is equipped with a permanent magnet drum;

[0040] The catalyst regeneration tank is equipped with an ultrasonic auxiliary device.

[0041] Optionally, the steps for treating the high-concentration, recalcitrant organic wastewater include:

[0042] Wastewater is pumped from the wastewater storage tank into the pretreatment area;

[0043] In the pretreatment zone, the pH sensor monitors and feeds back the pH value of the wastewater in real time and sends the feedback to the PLC controller. The PLC controller automatically adjusts the amount of acid or alkali added to the wastewater through the dosing pump to stabilize the pH value of the wastewater to 3-8. At the same time, the mechanical bar intercepts and retains suspended solids.

[0044] After pH adjustment and suspended solids removal in the pretreatment zone, the wastewater is pumped into the primary fluidized bed reaction zone by a constant flow pump to contact the magnetic heterogeneous catalyst filled therein. The bottom of the primary fluidized bed reaction zone is aerated with gas-liquid mixing to maintain the fluidization of the magnetic heterogeneous catalyst and initially degrade the wastewater.

[0045] After being treated in the primary fluidized bed reaction zone, the fluidized wastewater in the gas-liquid mixed state overflows into the electro-Fenton-ultrasonic coupling zone. In the electro-Fenton-ultrasonic coupling zone, Fe²⁺ is released in situ by the anode, H₂O₂ is generated by the cathode through aeration, and ultrasonic auxiliary module releases ultrasonic waves to generate cavitation effect. Under the control of the PLC controller, the wastewater is deeply oxidized and degraded under the synergistic action of the anode, cathode and ultrasound.

[0046] The wastewater treated in the electro-Fenton-ultrasonic coupling zone overflows into the secondary fluidized bed reaction zone, where the wastewater undergoes further degradation through inclined plate sedimentation to enhance solid-liquid separation.

[0047] Wastewater treated in the secondary fluidized bed reaction zone flows into the magnetic separation zone. In the magnetic separation zone, the magnetic separation intensity of the permanent magnet drum is controlled by a PLC controller. The magnetic separation heterogeneous catalyst is adsorbed and recovered and transported to the catalyst regeneration tank. At the same time, after ammonia nitrogen nitrification and chemical phosphorus removal, the resulting qualified clean water flows into the clear water tank, and the remaining sludge is discharged after sedimentation.

[0048] The catalyst is cleaned and regenerated in the catalyst regeneration tank, and then the regenerated catalyst is returned to the primary fluidized bed reaction zone and the electro-Fenton-ultrasonic coupling zone for recycling.

[0049] The beneficial effects of this application include:

[0050] The magnetic heterogeneous catalyst provided in this application combines high catalytic activity with magnetic recovery characteristics, allowing for reuse more than 10 times, reducing iron loss and sludge generation. It broadens the applicable pH range (pH 3-8), achieving a COD removal rate >95% at pH=5, overcoming the acid-base limitations of traditional Fenton technology (only 80% at pH=3). When applied to the treatment of high-concentration, recalcitrant organic wastewater, the magnetic heterogeneous catalyst utilizes an electrochemical-ultrasound synergistic enhancement system coupling electrochemical and ultrasonic technologies, resulting in high efficiency and energy saving. H2O2 utilization is increased by 50%, energy consumption is reduced by 30%, and it is environmentally friendly, with a magnetic catalyst recovery rate >95% and sludge reduction of 70%. In the treatment of high-concentration, recalcitrant organic wastewater, the magnetic heterogeneous catalyst employs intelligent operation and a magnetic adaptive control system to simplify maintenance. It is suitable for highly fluctuating wastewater and can treat pharmaceutical, dyeing, and coking wastewater with COD of 500-5000 mg / L, overcoming the traditional Fenton pH limitations. The technical solution presented in this application can be applied to wastewater treatment plants in industrial parks and enterprises discharging high-concentration organic wastewater (such as pharmaceutical factories and dyeing plants). It boasts advantages such as compact equipment and low operating costs (<0.8 RMB / ton of water), demonstrating significant market potential. Combined with the stringent environmental policies regarding the treatment of recalcitrant wastewater, this technology is expected to become a benchmark for next-generation advanced oxidation technologies. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the multi-stage fluidized bed reactor system of this application. Detailed Implementation

[0052] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0053] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0054] Ferric chloride hexahydrate (FeCl3·6H2O, ≥99%), ferrous chloride tetrahydrate (FeCl2·4H2O, ≥98%), activated carbon precursor (glucose, C6H2O) 12 O6 (analytical grade), copper nitrate (Cu(NO3)2·3H2O, ≥99%), manganese nitrate (Mn(NO3)2·50% aqueous solution), disodium EDTA (C 10 H 14N2Na2O8 (≥99%), ammonia (NH3·H2O, 25-28%), anhydrous ethanol (C2H5OH, ≥99.7%), cobalt chloride hexahydrate (CoCl2·6H2O, ≥99%), tetraethyl orthosilicate (TEOS, ≥98%), anhydrous ethanol (C2H5OH, ≥99.7%), ammonia (NH3·H2O, 25-28%), glucose (C6H 12 O6 (analytical grade), sucrose (secondary carbon source), nitrogen (N2, ≥99.99%).

[0055] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0056] Hydrothermal reactor (PTFE liner), tube furnace (N2 atmosphere), magnetic stirrer, centrifuge, vacuum drying oven, pH meter, magnetically stirred constant temperature water bath, and precision temperature-controlled tube furnace.

[0057] The magnetic strength was tested by VSM (Lake Shore 7404 type) under the following conditions: 25°C, magnetic field ±30 kOe, according to ASTM A894 standard.

[0058] Example 1: Magnetic heterogeneous catalyst (EDTA-Cu-Mn / Fe3O4@C)

[0059] Step 1: Synthesis of Fe3O4 nanoparticles

[0060] 2.16 g of FeCl3·6H2O and 0.795 g of FeCl2·4H2O were dissolved in 80 mL of deionized water and stirred for 30 min under nitrogen protection. 10 mL of 25% ammonia solution was added dropwise, and the mixture was reacted in a water bath at 60 °C for 2 h, resulting in a black precipitate. The precipitate was collected by magnetic separation, washed three times each with deionized water and ethanol, and dried under vacuum at 60 °C for 6 h to obtain Fe3O4 nanoparticles. Strict oxygen control (N2 protection) is required in this step to prevent oxidation to γ-Fe2O3.

[0061] Step 2: Preparation of Fe3O4@C composite support

[0062] 1.0 g of Fe3O4 nanoparticles and 3.0 g of glucose were dispersed in 50 mL of deionized water and sonicated for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 180 °C for 12 h. After cooling, the product was collected by centrifugation. The product was then placed in a tube furnace and carbonized at 600 °C for 2 h under a N2 atmosphere (heating rate 5 °C / min) to obtain the Fe3O4@C magnetic support. In this step, a carbonization temperature of 300–950 °C can balance the conductivity and magnetic stability of the carbon layer.

[0063] Step 3: Loading Cu-Mn active components

[0064] A mixed solution of 0.2 M Cu(NO3)2 and 0.1 M Mn(NO3)2 (Cu:Mn molar ratio = 2:1) was prepared. 1.0 g of Fe3O4@C support was impregnated in the above solution for 24 h, with ultrasonic-assisted dispersion (30 min / time). After evaporating the solvent at -60℃, the solution was calcined at 350℃ for 3 h in a tube furnace (air atmosphere, heating rate 3℃ / min) to obtain Cu-Mn / Fe3O4@C.

[0065] Step 4: EDTA surface modification

[0066] 0.5 g of Cu-Mn / Fe3O4@C was dispersed in 50 mL of 0.05 M EDTA solution (pH=6.0) and stirred at room temperature for 4 h. After magnetic separation, it was dried at 60 °C for 6 h to finally obtain the EDTA-Cu-Mn / Fe3O4@C catalyst, i.e., a magnetic heterogeneous catalyst. The chelation effect was optimal at pH 4–7 in this step, which can prevent metal dissolution.

[0067] The prepared magnetic heterogeneous catalyst was characterized and showed that the magnetic strength was ≥35 emu / g, and it could be magnetically separated and recovered. The specific surface area was ~180 m² / g as determined by the BET method, and the loading of active components was 5.2 wt% Cu and 2.8 wt% Mn as determined by ICP-OES.

[0068] Example 2: Magnetic heterogeneous catalyst (EDTA-Cu-Mn / CoFe2O4@C)

[0069] The preparation steps are the same as in Example 1, except that Fe3O4 nanoparticles are replaced with CoFe2O4 nanoparticles. The specific process is as follows:

[0070] Step 1: Synthesis of CoFe2O4 nanoparticles

[0071] 1.19 g of CoCl2·6H2O and 2.16 g of FeCl3·6H2O were dissolved in 80 mL of deionized water and stirred for 30 min under nitrogen protection. 10 mL of ammonia (25%) was added dropwise, and the mixture was transferred to a hydrothermal reactor and reacted at 200 °C for 12 h. After cooling, the mixture was magnetically separated, washed three times each with deionized water and ethanol, and dried under vacuum at 60 °C for 6 h to obtain CoFe2O4 nanoparticles.

[0072] Step 2: Preparation of CoFe2O4@C composite support

[0073] 1.0 g of Fe3O4 nanoparticles and 3.0 g of glucose were dispersed in 50 mL of deionized water and sonicated for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 180 °C for 12 h. After cooling, the product was collected by centrifugation. The product was then placed in a tube furnace and carbonized at 600 °C for 2 h under a N2 atmosphere (heating rate 5 °C / min) to obtain the CoFe2O4@C magnetic support. In this step, a carbonization temperature of 300–950 °C can balance the conductivity and magnetic stability of the carbon layer.

[0074] Step 3: Loading Cu-Mn active components

[0075] A mixed solution of 0.2 M Cu(NO3)2 and 0.1 M Mn(NO3)2 (Cu:Mn molar ratio = 2:1) was prepared. 1.0 g of Fe3O4@C support was impregnated in the above solution for 24 h, with ultrasonic-assisted dispersion (30 min / time). After evaporating the solvent at -60℃, the solution was calcined at 350℃ for 3 h in a tube furnace (air atmosphere, heating rate 3℃ / min) to obtain Cu-Mn / Fe3O4@C.

[0076] Step 4: EDTA surface modification

[0077] 0.5 g of Cu-Mn / CoFe2O4@C was dispersed in 50 mL of 0.05 M EDTA solution (pH=6.0) and stirred at room temperature for 4 h. After magnetic separation, it was dried at 60 °C for 6 h to finally obtain the EDTA-Cu-Mn / CoFe2O4@C catalyst, i.e., a magnetic heterogeneous catalyst. The chelation effect was optimal at pH 4–7 in this step, which can prevent metal dissolution.

[0078] The prepared magnetic heterogeneous catalyst was characterized and showed a magnetic strength ≥45 emu / g, indicating that it can be magnetically separated and recovered.

[0079] Example 3: Magnetic heterogeneous catalyst (SiO2-Cu-Mn / Fe3O4@C)

[0080] The preparation steps are the same as in Example 1, except that step 4 involves SiO2 surface modification, and the specific process is as follows:

[0081] Step 1: Synthesis of Fe3O4 nanoparticles

[0082] 2.16 g of FeCl3·6H2O and 0.795 g of FeCl2·4H2O were dissolved in 80 mL of deionized water and stirred for 30 min under nitrogen protection. 10 mL of 25% ammonia solution was added dropwise, and the mixture was reacted in a water bath at 60 °C for 2 h, resulting in a black precipitate. The precipitate was collected by magnetic separation, washed three times each with deionized water and ethanol, and dried under vacuum at 60 °C for 6 h to obtain Fe3O4 nanoparticles. Strict oxygen control (N2 protection) is required in this step to prevent oxidation to γ-Fe2O3.

[0083] Step 2: Preparation of Fe3O4@C composite support

[0084] 1.0 g of Fe3O4 nanoparticles and 3.0 g of glucose were dispersed in 50 mL of deionized water and sonicated for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 180 °C for 12 h. After cooling, the product was collected by centrifugation. The product was then placed in a tube furnace and carbonized at 600 °C for 2 h under a N2 atmosphere (heating rate 5 °C / min) to obtain the Fe3O4@C magnetic support. In this step, a carbonization temperature of 300–950 °C can balance the conductivity and magnetic stability of the carbon layer.

[0085] Step 3: Loading Cu-Mn active components

[0086] A mixed solution of 0.2 M Cu(NO3)2 and 0.1 M Mn(NO3)2 (Cu:Mn molar ratio = 2:1) was prepared. 1.0 g of Fe3O4@C support was impregnated in the above solution for 24 h, with ultrasonic-assisted dispersion (30 min / time). After evaporating the solvent at -60℃, the solution was calcined at 350℃ for 3 h in a tube furnace (air atmosphere, heating rate 3℃ / min) to obtain Cu-Mn / Fe3O4@C.

[0087] Step 4: SiO2 surface modification

[0088] 1.0 g Cu-Mn / Fe3O4@C was dispersed in 200 mL of ethanol / water mixed solution (V / V=4:1), then 5 mL of ammonia (25%) was added, and the mixture was sonicated for 30 min. Then, 2 mL of TEOS was added dropwise, and the mixture was stirred in a water bath at 50 °C for 6 h. After magnetic separation, the product was washed three times with ethanol and dried under vacuum at 60 °C for 12 h to obtain SiO2-Cu-Mn / Fe3O4@C.

[0089] The prepared magnetic heterogeneous catalyst was characterized and showed a magnetic strength ≥35 emu / g, which allows for magnetic separation and recovery; the specific surface area was ~220 m² / g as determined by the BET method.

[0090] Example 4: Magnetic heterogeneous catalyst (carbon layer - Mn / Fe3O4@C)

[0091] The preparation steps are the same as in Example 1, except that the carbon layer undergoes surface modification in step 4. The specific process is as follows:

[0092] Step 1: Synthesis of Fe3O4 nanoparticles

[0093] 2.16 g of FeCl3·6H2O and 0.795 g of FeCl2·4H2O were dissolved in 80 mL of deionized water and stirred for 30 min under nitrogen protection. 10 mL of 25% ammonia solution was added dropwise, and the mixture was reacted in a water bath at 60 °C for 2 h, resulting in a black precipitate. The precipitate was collected by magnetic separation, washed three times each with deionized water and ethanol, and dried under vacuum at 60 °C for 6 h to obtain Fe3O4 nanoparticles. Strict oxygen control (N2 protection) is required in this step to prevent oxidation to γ-Fe2O3.

[0094] Step 2: Preparation of Fe3O4@C composite support

[0095] 1.0 g of Fe3O4 nanoparticles and 3.0 g of glucose were dispersed in 50 mL of deionized water and sonicated for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 180 °C for 12 h. After cooling, the product was collected by centrifugation. The product was then placed in a tube furnace and carbonized at 600 °C for 2 h under a N2 atmosphere (heating rate 5 °C / min) to obtain the Fe3O4@C magnetic support. In this step, a carbonization temperature of 300–950 °C can balance the conductivity and magnetic stability of the carbon layer.

[0096] Step 3: Loading Cu-Mn active components

[0097] A mixed solution of 0.2 M Cu(NO3)2 and 0.1 M Mn(NO3)2 (Cu:Mn molar ratio = 2:1) was prepared. 1.0 g of Fe3O4@C support was impregnated in the above solution for 24 h, with ultrasonic-assisted dispersion (30 min / time). After evaporating the solvent at -60℃, the solution was calcined at 350℃ for 3 h in a tube furnace (air atmosphere, heating rate 3℃ / min) to obtain Cu-Mn / Fe3O4@C.

[0098] Step 4: Surface modification of carbon layer

[0099] 1.0 g of Cu-Mn / Fe3O4@C and 2.0 g of glucose were dispersed in 50 mL of deionized water and sonicated for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 180 °C for 6 h. The product was collected by centrifugation and then placed in a tube furnace for carbonization at 500 °C for 2 h under a N2 atmosphere (heating rate 3 °C / min) to obtain a carbon layer of Mn / Fe3O4@C. Carbonization at 500 °C can form a 2-5 nm carbon layer; excessively high temperatures (>700 °C) result in the covering of Mn active sites.

[0100] The prepared magnetic heterogeneous catalyst was characterized and showed a magnetic strength ≥35 emu / g, which allows for magnetic separation and recovery; the specific surface area was ~250 m² / g as determined by the BET method.

[0101] Application Example 1: Electrochemical-Ultrasound Synergistic Treatment of Wastewater

[0102] The magnetic heterogeneous catalysts prepared in Examples 1-4 were used to treat high-concentration, recalcitrant organic wastewater in a multi-stage fluidized bed reactor system under electro-Fenton coupled ultrasonic assistance.

[0103] (1) Schematic diagram of multi-stage fluidized bed reactor system as shown in Figure 1 Figure 1 As shown, it includes:

[0104] The components are arranged in series: wastewater storage tank, pretreatment zone, primary fluidized bed reaction zone, electro-Fenton-ultrasonic coupling zone, secondary fluidized bed reaction zone, magnetic separation zone, and clear water tank.

[0105] Catalyst regeneration tank, C&D;

[0106] And a PLC controller that controls the above system structure.

[0107] The above system structure is equipped with online monitoring devices and feedback control. All detection devices and feedback control form a prior monitoring system and a prior feedback system. The online monitoring system uses a COD sensor, pH probe, and ORP meter to adjust the H2O2 dosage, current density, and ultrasonic power in real time to ensure optimal reaction conditions. The online feedback control system, based on a PLC system, adjusts the multi-point addition of hydrogen peroxide, current intensity (1-3V), and ultrasonic frequency according to real-time water quality data. The pretreatment zone is filled with iron-carbon packing material. The catalyst separated in the magnetic separation zone is recovered to the catalyst regeneration tank, and the regenerated catalyst is reused from the catalyst regeneration tank in the electro-Fenton-ultrasonic coupling zone and the primary fluidized bed reaction zone.

[0108] The electro-Fenton-ultrasound coupling region includes: an electrochemical module employing an iron-carbon micro-electrolysis anode and a three-dimensional graphene cathode, with in-situ release of Fe from the anode. 2+ The cathode generates H2O2 through aeration, reducing the need for external reagent addition; the ultrasonic auxiliary module integrates a high-frequency ultrasonic device (40kHz), which utilizes the cavitation effect to enhance mass transfer efficiency, prevent catalyst agglomeration, and promote the ·OH generation rate to increase by more than 30%.

[0109] (2) Treatment of high-concentration, recalcitrant organic wastewater Specific process as follows:

[0110] Wastewater is pumped from the wastewater storage tank into the pretreatment zone. The PLC controller automatically adjusts the amount of acid (sulfuric acid) and alkali (sodium hydroxide) added via pH feedback signals (the pretreatment zone monitors pH in real time, and dynamic dosing ensures a deviation of ±0.2 from the set value) to stabilize the wastewater pH to 3-8. Simultaneously, a mechanical screen in the pretreatment zone intercepts suspended solids >100 μm (SS removal rate >90%). After pH adjustment and suspended solids interception, the wastewater is pumped to the primary fluidized bed reaction zone via a constant flow pump. The primary fluidized bed reaction zone is filled with magnetic catalyst (30% filling rate), and bottom gas-liquid mixing aeration (gas velocity 0.5 m / s) maintains fluidization. The hydraulic retention time (HRT) is 30 minutes. Organic matter (such as chlorobenzene) is adsorbed and enriched in the primary fluidized bed, degrading 30-40% of COD and adsorbing large molecular pollutants. In this zone, the magnetic catalyst is fluidized under bottom aeration, achieving initial degradation of organic matter. The gas-liquid mixed fluidized wastewater then overflows into the electro-Fenton-ultrasonic coupling zone. The PLC synchronously controls the current and adjusts the constant flow pump rate (5 m³ / h) to maintain stable hydraulic load in each reaction zone. Ultrasonic regulation (current density 10 mA / cm², intermittent ultrasonic operation at 40 kHz) is also used. H₂O₂ is generated in situ at the cathode, and the catalyst activates free radicals (·OH) to attack organic pollutants, causing ring-opening and chain scission, generating small molecule acids. After 60 minutes of HRT, the COD removal rate is >95%. Under the synergistic effect of electrodes and ultrasound (electro-acoustic synergy: automatically adjusting the current density (8-12 mA / cm²) and ultrasonic power (40-60 W / L) based on online COD data), pollutants are deeply oxidized. After the reaction, the wastewater overflows into the secondary fluidized bed reaction zone. In the secondary fluidized bed reaction zone, the overflow wastewater undergoes enhanced solid-liquid separation HRT via inclined plate sedimentation. Organic acids are deeply degraded in 20 minutes, and small molecule intermediates are further mineralized and oxidized to CO2 and H2O, ultimately flowing into the magnetic separation zone: PLC controls the magnetic separation intensity (0.5 T permanent magnet drum), adsorbs and recovers magnetic catalyst (recovery rate > 95%), and simultaneously achieves ammonia nitrogen nitrification (DO > 2 mg / L) and chemical phosphorus removal (Fe). 3+ The remaining sludge is discharged after sedimentation (dry weight 0.05 kg / m³). The recovered catalyst is transported to the catalyst regeneration tank for EDTA cleaning (0.1 M, pH=4, 60℃) followed by vacuum drying, with activity recovery >95%. The regenerated catalyst is then returned to the primary / secondary fluidized bed for recycling. When the catalyst activity decreases by 10%, the EDTA cleaning program is automatically initiated. The effluent from the magnetic separation zone is collected and discharged into a clear water tank meeting discharge standards (COD < 50 mg / L, total iron < 1.0 mg / L). This system achieves efficient, low-consumption, and sustainable treatment of high-concentration, recalcitrant organic wastewater through a multi-stage catalytic oxidation-magnetic separation regeneration closed-loop process, making it particularly suitable for complex wastewater systems in industrial parks.

[0111] (3) Catalyst recovery and regeneration:

[0112] Wastewater enters the magnetic separation zone, where a permanent magnet drum adsorbs magnetic catalyst. The catalyst is then scraped to a collection tank by a mechanical scraper (avoiding the clogging problem of traditional filters). It is then conveyed to a regeneration tank by a screw conveyor. The multi-stage fluidized bed reactor system uses a PLC to control the magnetic separation-transportation-regeneration closed loop, reducing the rate of manual intervention by 90%.

[0113] The wastewater treatment process parameters and procedures are shown in Table 1.

[0114] Table 1

[0115]

[0116] The synergistic mechanism in this application is as follows: Ultrasonic cavitation: enhances mass transfer, strips the passivation layer on the catalyst surface, and maintains the exposure of active sites. Electro-Fenton: continuously generates H2O2 at the cathode (in-situ oxygen supply), which reacts with Fe... 2+ / Cu - The Mn catalytic system generates ·OH (increasing the quantum yield of free radicals by 40%).

[0117] Application Result Analysis:

[0118] The wastewater treatment results at pH 5 in the pretreatment zone are shown in Tables 2 to 5.

[0119] Table 2 Comparison of results before and after treatment with the magnetic heterogeneous catalyst of Example 1

[0120]

[0121] Table 3 Comparison of results before and after treatment with the magnetic heterogeneous catalyst of Example 2

[0122]

[0123] Comparing Table 3 and Table 2, the magnetic heterogeneous catalyst of Example 2 has stronger magnetic strength and higher catalytic activity (Co-enhanced H2O2 activation) compared to that of Example 1.

[0124] Table 4 Comparison of results before and after treatment with the magnetic heterogeneous catalyst of Example 3

[0125]

[0126] Comparing Tables 2 and 4, the Fe ion leaching resistance of Example 3 is stronger than that of the magnetic heterogeneous catalyst of Example 1.

[0127] Table 5 Comparison of results before and after treatment with the magnetic heterogeneous catalyst of Example 4

[0128]

[0129] Test Example 1

[0130] Taking the magnetic heterogeneous catalyst (EDTA-Cu-Mn / Fe3O4@C) prepared in Example 1 as an example, the treatment of high-concentration recalcitrant organic wastewater in a multi-stage fluidized bed reactor system under electro-Fenton coupled ultrasonic assistance was carried out. The study investigated wide pH adaptability, synergistic mechanism, energy consumption, catalyst recovery, and sludge reduction.

[0131] (1) Wide pH adaptability

[0132] In the application of the magnetic heterogeneous catalysts in Examples 1-4, the COD removal rate was still >95% at pH=5. In Example 1, the COD removal rate was as high as 98% at pH=3 and 88% at pH=7 (compared to only about 80% for the conventional Fenton catalyst at pH=3; this data is from: Neyens, E., & Baeyens, J. (2003). 对经典芬顿氧化作为一种高级氧化技术的综述 芬顿氧化与超声强化芬顿反应的比较研究 Journal of Hazardous Materials, 98(1-3), 33-50. This review points out that the COD removal rate of traditional Fenton reactors is usually 70%-85% at pH=2-4, and the efficiency decreases significantly after pH>4; Wang, S., et al. (2016). 芬顿 和超声强化芬顿反应 Chemical Engineering Journal, 283, 841-848. Experimental data in this paper showed that the COD removal rate of phenol wastewater was 78.5% at pH=3, decreasing to 45% at pH=5. A wastewater treatment plant operation report (2019) from a chemical industrial park, used as an engineering case study, showed that the average COD removal rate of the traditional Fenton method was 81.2% at pH=3, but only 52.6% at pH=5. (The reason why the traditional Fenton method becomes less effective at higher pH levels). Breakthrough in overcoming pH limitations: EDTA modification stabilizes the metal active centers and inhibits Fe... 3+ Precipitation; Cu-Mn broadens the ·OH formation pathway; the SiO2 layer isolates the magnetic core from corrosion by acidic / alkaline media, maintaining 90% activity after 15 cycles (85% after EDTA modification); the carbon layer accelerates Mn... 3+ / Mn 2+ Redox cycles enhance free radical production, and the carbon layer completely encapsulates the iron core, resulting in iron loss of <0.1 mg / L under acidic conditions (pH=2).

[0133] Key mechanism: Fe 2+ The reason for inactivation is Fe 2+ + H2O2→ Fe 3+ +OH -The equation +·OH fully expresses the process by which ferrous ions catalyze the decomposition of hydrogen peroxide to generate hydroxyl radicals under acidic conditions (pH < 4), which is the core mechanism of the Fenton reaction. 3+ +3OH - →Fe(OH)3↓ at pH>4, Fe 2+ It is rapidly oxidized to Fe 3+ The iron precipitates Fe(OH)3, forming a colloid, which reduces the concentration of active iron. ·OH (hydroxyl radical), the main active species in the Fenton reaction, has extremely strong oxidizing power. The Fe(OH)3 precipitation is the core reason why the traditional Fenton process fails at pH > 4, as it encapsulates the active sites of the catalyst. These two steps reveal the limitations of traditional Fenton technology: Under acidic conditions (pH 2-4): Reaction 1 dominates, continuously generating ·OH to degrade pollutants. Under moderately alkaline conditions (pH > 4): Reaction 2 is intensified, and iron precipitation leads to catalyst deactivation.

[0134] The key to overcoming the pH limitation in this technical solution lies in the advantages of magnetic heterogeneous catalysts. Taking the EDTA-Cu-Mn / Fe3O4@C catalyst as an example, the specific details are as follows:

[0135] a. Improved metal stability:

[0136] EDTA chelates Cu 2+ / Mn 2+ / Fe 2+ It inhibits the precipitation of metal ions (remains soluble in the pH range of 3-8).

[0137] b. Synergistic effect of multiple metals:

[0138] Cu-Mn redox couple (Cu 2+ / Cu + Mn 3+ / Mn 2+ ) Broaden the OH formation pathway and reduce the impact on Fe 2+ Dependence.

[0139] (2) Energy consumption comparison

[0140] The overall energy consumption of the technical solution in this application is 2.8 kWh / m³, which is 30% lower than that of the traditional electric Fenton (4.0 kWh / m³). Specifically:

[0141] The calculation basis for the comprehensive energy consumption of this application is as follows:

[0142] Power consumption components:

[0143] Electric Fenton system: 1.8 kWh / m³ (current density 10 mA / cm²) 2 (Voltage 8V)

[0144] Ultrasonic system: 0.7 kWh / m³ (50 W / L, 20% of operation is intermittent)

[0145] Other energy consumption: 0.3 kWh / m³ (pumps, magnetic separators, and other auxiliary equipment)

[0146] Calculation formula:

[0147] Total energy consumption calculation formula (Chinese expression)

[0148] Total energy consumption = (Power of electric Fenton system × Operating time + Power of ultrasonic system × Actual working time) ÷ Wastewater treatment volume

[0149] Taking the treatment of 1m³ of wastewater as an example:

[0150] Electric Fenton: 8V × 10A × 1h = 0.8 kWh (Actual efficiency 90% → 1.8 kWh / m³)

[0151] Ultrasonic treatment: 50W × 0.2 × 1h = 0.01 kWh / L → 10 kWh / m³ (reduced to 0.7 kWh / m³ after catalyst enhancement)

[0152] The sources of traditional electric Fenton energy consumption data are as follows:

[0153] Brillas et al. (2009) 电芬顿工艺:基础与 反应活性 Reports indicate that traditional electro-Fenton treatment of similar wastewater consumes 3.8-4.2 kWh / m³ (pH=3, current density 15 mA / cm²); an industrial case study (a pharmaceutical factory's wastewater treatment plant's 2018 operation report) shows an average energy consumption of 4.1 kWh / m³ (including H₂O₂ addition and sludge treatment energy consumption). The high energy consumption of traditional Fenton treatment is mainly due to: the need to maintain a low pH (acid addition cost + subsequent neutralization), iron sludge treatment accounting for 25-30% of the total energy consumption, and low H₂O₂ utilization rate (approximately 40% vs. 75% in this application).

[0154] The key differences between the technical solution of this application and the traditional electric Fenton are shown in Table 6.

[0155] Table 6

[0156]

[0157] The energy consumption verification experiment is as follows:

[0158] Test method: The power consumption of each unit was monitored in real time using a power analyzer (such as HIOKI PW3390), and the results were repeated 3 times and the average value was taken.

[0159] Data reproducibility: Energy consumption fluctuation of different batches of wastewater (COD 1500-2500 mg / L) was ±0.3 kWh / m³.

[0160] (3) Comparison of catalyst recovery

[0161] The main technical reason why traditional catalysts cannot be recovered lies in the inherent defects of traditional homogeneous Fenton catalysts, as shown in Table 7.

[0162] Table 7

[0163]

[0164] In the application of the magnetic heterogeneous catalyst of this application, the iron content in the liquid phase before and after the reaction was determined by ICP-MS, and the catalyst recovery rate was calculated to be >95%. Compared with the application of traditional homogeneous Fenton catalysts, the advantages of the technical solution of this application are shown in Table 8.

[0165] Table 8

[0166]

[0167] (4) Comparison of sludge conditions

[0168] The method for calculating the dry weight of sludge is as follows:

[0169] Sludge dry weight (kg / m³) = (Wet sludge mass (kg) × (1 - moisture content)) ÷ treated water volume (m³) 3 ),

[0170] The specific calculation process in this application is as follows: the water treatment volume is 1 m³. 3 After magnetic separation, 100 g of sludge mixture (95% moisture content) was collected, dried at 105℃ to constant weight, and 5 g of dry matter was measured. Then, the formula was used for calculation (actual operating data was magnified 10 times to calculate the safety margin).

[0171] In the traditional Fenton process (reference: Pignatello et al. (2006)) 《环境科学与技术》 40(23): 7298-7304 records the production of 0.15-0.2 kg / m³ of Fe(OH)₃ sludge from the treatment of phenol wastewater (COD=1000 mg / L). 3 The iron content is approximately 35% (on a dry basis). The traditional Fenton process calculates the dry weight of the sludge as follows: For a treated water volume of 1 m³... 3 After adjusting the pH to 8.5, sedimentation was carried out to obtain 1.7 kg of wet sludge (90% moisture content). After drying, the dry matter was 170 g, and then the formula was used for calculation.

[0172] Based on comprehensive comparison, the dry weight of the sludge in this application is 0.05 kg / m³. 3In the traditional Fenton process, the dry weight of sludge is 0.17 kg / m³. 3 The amount of sludge is reduced by about 70%.

[0173] The key factors influencing sludge reduction mainly include:

[0174] pH adjustment stage: Traditional Fenton reactors require adding acid to pH=3 (reaction) and then adding alkali to pH=8 (precipitation), which significantly increases the amount of sludge due to the double addition of reagents;

[0175] Iron salt dosage: usually Fe 2+ H₂O₂ = 1:5 (molar ratio), excess iron eventually forms Fe(OH)₃;

[0176] Core of reduction:

[0177] Avoid the transformation of iron ions (Fe) 2+ →Fe 3+ →Fe(OH)3);

[0178] Magnetic separation directly recovers the catalyst, leaving only undegraded suspended solids (SS) to form sludge;

[0179] Test method verification:

[0180] The standard method refers to "Methods for Monitoring and Analyzing Water and Wastewater" (4th Edition);

[0181] Sludge moisture content: GB / T 27860-2011 (105℃ drying method);

[0182] COD: HJ 828-2017 (Potassium dichromate titration method);

[0183] Iron content: determined by ICP-MS.

[0184] The actual measurement data are compared in Table 9.

[0185] Table 9

[0186]

[0187] Note: The sludge in this application has extremely low iron content, proving that the catalyst can be effectively recovered.

[0188] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A magnetic heterogeneous catalyst, characterized in that, It includes a composite carrier loaded with active components and a surface modification layer covering the outside of the composite carrier loaded with active components; The composite carrier is a magnetic carrier obtained by combining magnetic particles and activated carbon. The magnetic particles are selected from at least one of Fe3O4 and CoFe2O4; The active component is at least one of a transition metal or an oxide thereof; The material of the surface modification layer is selected from at least one of EDTA, SiO2, and activated carbon; The preparation method of the magnetic heterogeneous catalyst includes the following steps: S1 provides magnetic nanoparticles; S2. An aqueous solution containing magnetic nanoparticles and activated carbon precursor is placed in a sealed container and subjected to a hydrothermal reaction. The product of the hydrothermal reaction is then carbonized in an inactive atmosphere to obtain a composite carrier. S3. The composite carrier is placed in a salt solution containing the active component for impregnation, and then the impregnated composite carrier is calcined in an oxygen-containing atmosphere to obtain a composite carrier loaded with the active component. S4. A surface modification layer is formed on the outside of the composite support loaded with active components to obtain the magnetic heterogeneous catalyst. In step S4, when the material of the surface modification layer is EDTA, the method for forming the surface modification layer includes the following steps: The composite carrier loaded with active components was dispersed in 0.05M EDTA solution at a solid-liquid ratio of 1g:100mL, under conditions of pH 4-7, and stirred for 4-8h. The product was then magnetically separated and dried. In step S4, when the surface modification layer is made of SiO2, the method for forming the surface modification layer includes the following steps: The composite carrier loaded with active components was dispersed in an alcohol-water mixture, and then 25% ammonia water was added and mixed. The mixture was ultrasonically treated for 30-60 min, and then TEOS was added dropwise. The mixture was stirred at 50°C for 6-8 h. The product was then magnetically separated, washed with alcohol, and dried. The solid-liquid ratio of the composite carrier loaded with active components, alcohol-water mixture, 25% ammonia solution, and TEOS is 1g:200mL:5mL:2mL. In step S4, when the surface modification layer is made of activated carbon, the method for forming the surface modification layer includes the following steps: The composite carrier loaded with active components and glucose were dispersed in water at a solid-liquid ratio of 1g:2g:50mL. The mixture was ultrasonically treated for 30-60 minutes, and then placed in a sealed container for hydrothermal reaction at 180-200℃ for 6-8 hours. The final product was carbonized in an inactive atmosphere at 500-700℃ for 2-3 hours to form a carbon layer of 2-5nm.

2. The magnetic heterogeneous catalyst according to claim 1, characterized in that, The magnetic heterogeneous catalyst has a magnetic strength ≥35 emu / g.

3. The method for preparing the magnetic heterogeneous catalyst according to claim 1 or 2, characterized in that, Includes the following steps: S1 provides magnetic nanoparticles; S2. An aqueous solution containing magnetic nanoparticles and activated carbon precursor is placed in a sealed container and subjected to a hydrothermal reaction. The product of the hydrothermal reaction is then carbonized in an inactive atmosphere to obtain a composite carrier. S3. The composite carrier is placed in a salt solution containing the active component for impregnation, and then the impregnated composite carrier is calcined in an oxygen-containing atmosphere to obtain a composite carrier loaded with the active component. S4. A surface modification layer is formed on the outside of the composite support loaded with active components to obtain the magnetic heterogeneous catalyst. In step S4, when the material of the surface modification layer is EDTA, the method for forming the surface modification layer includes the following steps: The composite carrier loaded with active components was dispersed in 0.05M EDTA solution at a solid-liquid ratio of 1g:100mL, under conditions of pH 4-7, and stirred for 4-8h. The product was then magnetically separated and dried. In step S4, when the surface modification layer is made of SiO2, the method for forming the surface modification layer includes the following steps: The composite carrier loaded with active components was dispersed in an alcohol-water mixture, and then 25% ammonia water was added and mixed. The mixture was ultrasonically treated for 30-60 min, and then TEOS was added dropwise. The mixture was stirred at 50°C for 6-8 h. The product was then magnetically separated, washed with alcohol, and dried. The solid-liquid ratio of the composite carrier loaded with active components, alcohol-water mixture, 25% ammonia solution, and TEOS is 1g:200mL:5mL:2mL. In step S4, when the surface modification layer is made of activated carbon, the method for forming the surface modification layer includes the following steps: The composite carrier loaded with active components and glucose were dispersed in water at a solid-liquid ratio of 1g:2g:50mL. The mixture was ultrasonically treated for 30-60 minutes, and then placed in a sealed container for hydrothermal reaction at 180-200℃ for 6-8 hours. The final product was carbonized in an inactive atmosphere at 500-700℃ for 2-3 hours to form a carbon layer of 2-5nm.

4. The preparation method according to claim 3, characterized in that, In step S1, the method for preparing the magnetic particles includes: In an inactive atmosphere, an alkaline precipitant is added dropwise to a soluble salt solution containing the metal in the magnetic particles, and a co-precipitation reaction is carried out to obtain the magnetic nanoparticles.

5. The preparation method according to claim 3, characterized in that, In step S2, the activated carbon precursor is selected from glucose; In step S2, the carbonization temperature is 300–950°C.

6. The preparation method according to claim 3, characterized in that, In step S3, the salt solution containing the active component is an aqueous solution of a soluble salt comprising at least one transition metal.

7. The application of the magnetic heterogeneous catalyst according to claim 1 or 2, or the magnetic heterogeneous catalyst prepared according to any one of claims 3 to 6, in the treatment of high-concentration, recalcitrant organic wastewater, characterized in that... The treatment of the high-concentration, recalcitrant organic wastewater is carried out in a multi-stage fluidized bed reactor system under conditions assisted by electro-Fenton coupled ultrasound.

8. The application according to claim 7, characterized in that, The multi-stage fluidized bed reactor system includes: The wastewater storage tank, pretreatment zone, primary fluidized bed reaction zone, electro-Fenton-ultrasonic coupling zone, secondary fluidized bed reaction zone, magnetic separation zone, and clear water tank are connected in series. Catalyst regeneration tank, C&D, PLC controller; The inlet of the catalyst regeneration tank is connected to the magnetic separation zone, and the outlet of the catalyst regeneration tank is connected to the primary fluidized bed reaction zone and the electro-Fenton-ultrasonic coupling zone, respectively. The PLC controller is electrically connected to the pretreatment area, the electro-Fenton-ultrasonic coupling area, the magnetic separation area, and the C&D system. The pretreatment zone includes a pH sensor for monitoring the acidity and alkalinity of wastewater, a dosing pump for adjusting the acidity and alkalinity of wastewater, and a mechanical bar for removing suspended solids. The primary fluidized bed reaction zone is filled with the magnetic heterogeneous catalyst; The electro-Fenton-ultrasound coupling region includes an electrochemical module and an ultrasound-assisted module, wherein the electrochemical module includes an iron-carbon micro-electrolysis anode and a three-dimensional graphene cathode. The secondary fluidized bed reaction zone is equipped with inclined plates for assisting solid-liquid separation; The magnetic separation zone is equipped with a permanent magnet drum; The catalyst regeneration tank is equipped with an ultrasonic auxiliary device.

9. The application according to claim 8, characterized in that, The steps for treating high-concentration, recalcitrant organic wastewater include: Wastewater is pumped from the wastewater storage tank into the pretreatment area; In the pretreatment zone, the pH sensor monitors and feeds back the pH value of the wastewater in real time and sends the feedback to the PLC controller. The PLC controller automatically adjusts the amount of acid or alkali added to the wastewater through the dosing pump to stabilize the pH value of the wastewater to 3-8. At the same time, the mechanical bar intercepts and retains suspended solids. After pH adjustment and suspended solids removal in the pretreatment zone, the wastewater is pumped into the primary fluidized bed reaction zone by a constant flow pump to contact the magnetic heterogeneous catalyst filled therein. The bottom of the primary fluidized bed reaction zone is aerated with gas-liquid mixing to maintain the fluidization of the magnetic heterogeneous catalyst and initially degrade the wastewater. After treatment in the primary fluidized bed reaction zone, the fluidized wastewater, in a gas-liquid mixed state, overflows into the electro-Fenton-ultrasonic coupling zone, where Fe is released in situ from the anode. 2+ The cathode generates H2O2 through aeration, and the ultrasonic auxiliary module releases ultrasonic waves to generate a cavitation effect. Under the control of the PLC controller, the anode, cathode and ultrasonic waves work together to deeply oxidize and degrade the wastewater. The wastewater treated in the electro-Fenton-ultrasonic coupling zone overflows into the secondary fluidized bed reaction zone, where the wastewater undergoes further degradation through inclined plate sedimentation to enhance solid-liquid separation. Wastewater treated in the secondary fluidized bed reaction zone flows into the magnetic separation zone. In the magnetic separation zone, the magnetic separation intensity of the permanent magnet drum is controlled by a PLC controller. The magnetic separation heterogeneous catalyst is adsorbed and recovered and transported to the catalyst regeneration tank. At the same time, after ammonia nitrogen nitrification and chemical phosphorus removal, the resulting qualified clean water flows into the clear water tank, and the remaining sludge is discharged after sedimentation. The catalyst is cleaned and regenerated in the catalyst regeneration tank, and then the regenerated catalyst is returned to the primary fluidized bed reaction zone and the electro-Fenton-ultrasonic coupling zone for recycling.

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