Magnetic heterogeneous catalyst as well as preparation method and application thereof

Abstract

The invention discloses a magnetic heterogeneous catalyst as well as a preparation method and application thereof, and belongs to the technical field of wastewater treatment catalysts. The magnetic heterogeneous catalyst has the characteristics of high catalytic activity and magnetic recovery, can be repeatedly used for more than 10 times in treatment of high-concentration degradation-resistant organic wastewater, reduces iron loss and sludge generation, widens the pH application range (pH 3-8), can be applied to wastewater treatment stations in industrial parks and high-concentration organic wastewater discharge enterprises (such as pharmaceutical factories and printing and dyeing mills), and has wide application prospects. The device has the advantages of compact equipment, low operation cost (less than 0.8 yuan / ton of water) and the like, and has remarkable market potential. In combination with strict requirements of current environmental protection policies on treatment of refractory wastewater, the technology is expected to become a benchmark of a new generation of advanced oxidation technology.

Description

Technical Field

[0001] The present application relates to a magnetic heterogeneous catalyst and a preparation method and application thereof, belonging to the technical field of wastewater treatment catalysts. Background Art

[0002] For the treatment of high-concentration, difficult-to-degrade organic wastewater (such as pharmaceutical, dye, and pesticide wastewater), the traditional Fenton method has problems such as strong pH dependence (requires acidic conditions), secondary pollution of iron sludge, and low H2O2 utilization rate. Although heterogeneous Fenton can alleviate some of these problems, the catalyst recovery is difficult and the activity is easily attenuated. Although electro-Fenton can produce H2O2 and Fe in situ, 2+ However, the electrodes are susceptible to passivation and energy consumption is high. Existing technologies such as photo-Fenton and ultrasonic Fenton can improve efficiency, but the equipment is complex and costly. Therefore, there is an urgent need for a new Fenton technology that is efficient, energy-efficient, easy to operate, and has reusable catalysts. Summary of the Invention

[0003] To address the high costs, complex processes, and poor catalyst recyclability inherent in existing wastewater treatment technologies, this application proposes a magnetic heterogeneous catalyst technology solution. This solution utilizes magnetic Fe₃O₄ nanoparticles as a core, coated with mesoporous activated carbon and loaded with a transition metal (such as a Cu-Mn bimetallic), with enhanced stability through EDTA chelation. This catalyst combines high catalytic activity with magnetic recyclability, allowing for reuse more than 10 times, reducing iron loss and sludge production, and extending its pH range (pH 3-8).

[0004] This application adopts the following technical solutions: According to a first aspect of the present application, there is provided a magnetic heterogeneous catalyst comprising a composite carrier carrying an active component and a surface modification layer coated on the outside of the composite carrier carrying the active component; 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 transition metal or its oxide; The material of the surface modification layer is selected from at least one of EDTA, SiO2, and activated carbon.

[0005] Optionally, the magnetic strength of the magnetic heterogeneous catalyst is ≥35 emu / g. The main functions of the surface modification layers of EDTA, SiO2 and activated carbon are to isolate the acidic / alkaline media from corroding the magnetic core and reduce the loss rate of iron ions.

[0006] According to the second aspect of the present application, a method for preparing the above-mentioned magnetic heterogeneous catalyst is provided, comprising the following steps: S1. providing magnetic nanoparticles; S2, placing an aqueous solution containing magnetic nanoparticles and an activated carbon precursor in a sealed container for a hydrothermal reaction, and then carbonizing the product of the hydrothermal reaction in an inert atmosphere to obtain a composite carrier; S3, placing the composite support in a salt solution containing an active component for impregnation, and then calcining the impregnated composite support in an oxygen-containing atmosphere to obtain a composite support loaded with the active component; S4. Forming a surface modification layer on the exterior of the composite carrier carrying the active component to obtain the magnetic heterogeneous catalyst.

[0007] Optionally, in step S1, the method for preparing the magnetic particles includes: In an inert atmosphere, an alkaline precipitant is added dropwise to a soluble salt solution containing the metal in the magnetic particles to undergo a coprecipitation reaction to obtain the magnetic nanoparticles.

[0008] Optionally, in step S2, the activated carbon precursor is selected from glucose; In step S2, the carbonization temperature is 300-950°C.

[0009] 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.

[0010] Optionally, in step S4, when the material of the surface modification layer is EDTA, the method for forming the surface modification layer comprises the following steps: The composite carrier loaded with active ingredients was dispersed in 0.05 M EDTA solution at a solid-liquid ratio of 1 g:100 mL, with a pH of 4-7, and stirred for 4-8 h. The product was then magnetically separated and dried. In step S4, when the material of the surface modification layer is SiO2, the method for forming the surface modification layer comprises the following steps: The composite support loaded with active ingredients was dispersed in an alcohol-water mixture, and then 25% ammonia water was added for mixing. The mixture was ultrasonicated for 30-60 minutes, and then TEOS was added dropwise. The mixture was stirred at 50-560°C for 6-8 hours. The product was then subjected to magnetic separation, alcohol washing, and drying. The solid-liquid ratio of the composite carrier loaded with active components, alcohol-water mixture, 25% ammonia water, and TEOS is 1 g:200 mL:5 mL:2 mL; In step S4, when the material of the surface modification layer is activated carbon, the method for forming the surface modification layer includes the following steps: The active component-loaded composite carrier and glucose were dispersed in water at a solid-liquid ratio of 1 g:2 g:50 mL, ultrasonically treated for 30-60 min, and then placed in a sealed container for hydrothermal reaction at 180-200°C for 6-8 h. The product was finally carbonized in an inert atmosphere at 500-700°C for 2-3 h to form a 2-5 nm carbon layer.

[0011] According to the third aspect of the present application, there is provided an application of the above-mentioned magnetic heterogeneous catalyst and the magnetic heterogeneous catalyst prepared according to the above-mentioned preparation method in the treatment of high-concentration refractory organic wastewater. The treatment of high-concentration refractory organic wastewater is carried out in a multi-stage fluidized bed reactor system under the conditions of electro-Fenton coupled ultrasonic assistance.

[0012] Optionally, the multi-stage fluidized bed reactor system comprises: The wastewater storage tank, pretreatment area, primary fluidized bed reaction area, electro-Fenton-ultrasonic coupling area, secondary fluidized bed reaction area, magnetic separation area, and clear water tank are arranged 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 zone, the electro-Fenton-ultrasonic coupling zone, the magnetic separation zone, and the C&D; The pretreatment area includes a pH sensor for monitoring the acidity and alkalinity of the wastewater, a dosing pump for adjusting the acidity and alkalinity of the wastewater, and a mechanical screen for removing suspended matter; The primary fluidized bed reaction zone is filled with the magnetic heterogeneous catalyst; The electro-Fenton-ultrasonic coupling zone includes an electrochemical module and an ultrasonic auxiliary 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 provided with an inclined plate for assisting solid-liquid separation; A permanent magnetic roller is provided in the magnetic separation zone; The catalyst regeneration tank is provided with an ultrasonic auxiliary device.

[0013] Optionally, the steps of treating high-concentration refractory organic wastewater include: Wastewater is pumped from the wastewater storage tank into the pretreatment area; The pH sensor in the pretreatment area monitors and feeds back the pH value of the wastewater in real time and feeds back 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 screen intercepts and retains suspended matter. The wastewater after pH adjustment and suspended solids interception in the pretreatment zone is pumped into the primary fluidized bed reaction zone through a constant flow pump to contact the magnetic heterogeneous catalyst filled therein. The gas-liquid mixed aeration at the bottom of the primary fluidized bed reaction zone maintains the fluidization of the magnetic heterogeneous catalyst to preliminarily degrade the wastewater. After being treated in the primary fluidized bed reaction zone, the fluidized wastewater in a gas-liquid mixture overflows into the electro-Fenton-ultrasonic coupling zone. In the electro-Fenton-ultrasonic coupling zone, the anode releases Fe²⁺ in situ, the cathode produces H2O2 through aeration, and the ultrasonic auxiliary module releases ultrasonic waves to produce a cavitation effect. Under the synergistic action of the anode, cathode and ultrasound controlled by the PLC controller, the wastewater is deeply oxidized and degraded. The wastewater after being treated in the electro-Fenton-ultrasonic coupling zone overflows into the secondary fluidized bed reaction zone, where the wastewater is further degraded by enhanced solid-liquid separation through inclined plate sedimentation; The wastewater treated in the secondary fluidized bed reaction zone flows into the magnetic separation zone, where the magnetic separation intensity of the permanent magnet drum is controlled by a PLC controller, and the magnetic separation heterogeneous catalyst is adsorbed and recovered and transported to the catalyst regeneration tank. After ammonia nitrogen nitrification and chemical phosphorus removal are simultaneously performed, the generated clean water that meets the discharge standards flows into the clean 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 cyclic use.

[0014] The beneficial effects of this application include: The magnetic heterogeneous catalyst provided in this application combines high catalytic activity with magnetic recovery properties, making it reusable more than 10 times and reducing iron loss and sludge production. It also extends its pH range (pH 3-8), achieving a COD removal rate of >95% at pH 5, surpassing the acid-base limitation of traditional Fenton technology (only 80% at pH 3). When used in the treatment of high-concentration, refractory organic wastewater, the magnetic heterogeneous catalyst utilizes an electrochemical-ultrasonic synergistic enhancement system coupled with electrochemical and ultrasonic technologies, resulting in high efficiency and energy conservation. This increases H2O2 utilization by 50%, reduces energy consumption by 30%, and is environmentally friendly. The magnetic catalyst recovery rate is >95%, and sludge reduction is 70%. When used in the treatment of high-concentration, refractory organic wastewater, the magnetic heterogeneous catalyst utilizes intelligent operation and a magnetic adaptive control system to simplify operation and maintenance. It is suitable for highly volatile wastewater and can treat pharmaceutical, printing and dyeing, and coking wastewater with COD levels of 500-5000 mg / L, surpassing the traditional Fenton pH limitation. The technical solution in this application can be applied to industrial park wastewater treatment stations and enterprises discharging high-concentration organic wastewater (such as pharmaceutical factories and printing and dyeing plants). It offers advantages such as compact equipment and low operating costs (less than 0.8 yuan per ton of water), and has significant market potential. Combined with current environmental protection policies' stringent requirements for the treatment of refractory wastewater, this technology is expected to become a benchmark for the next generation of advanced oxidation technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the structure of the multi-stage fluidized bed reactor system of this application. DETAILED DESCRIPTION

[0016] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0017] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0018] Ferric chloride hexahydrate (FeCl3·6H2O, ≥99%), ferrous chloride tetrahydrate (FeCl2·4H2O, ≥98%), activated carbon precursor (glucose, C6H 12 O6, analytical grade), copper nitrate (Cu(NO3)2·3H2O, ≥99%), manganese nitrate (Mn(NO3)2·50% aqueous solution), disodium EDTA (C 10 H 14 N2Na2O8, ≥99%), ammonia water (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 water (NH3·H2O, 25-28%), glucose (C6H 12O6, analytical grade), sucrose (secondary carbon source), and nitrogen (N2, ≥99.99%).

[0019] Unless otherwise specified, conventional methods were used for testing, and instrument settings were those recommended by the manufacturer.

[0020] Hydrothermal reactor (PTFE lined), tubular furnace (N2 atmosphere), magnetic stirrer, centrifuge, vacuum drying oven, pH meter, magnetic stirring constant temperature water bath, precise temperature control tubular furnace. Magnetic strength was tested by VSM (Lake Shore 7404) at 25°C and a magnetic field of ±30 kOe, in accordance with ASTM A894.

[0021] Example 1 Magnetic Heterogeneous Catalyst (EDTA-Cu-Mn / Fe3O4@C) Step 1: Synthesis of Fe3O4 nanoparticles Dissolve 2.16 g of FeCl₃·6H₂O and 0.795 g of FeCl₂·4H₂O in 80 mL of deionized water and stir under nitrogen for 30 min. Add 10 mL of 25% aqueous ammonia dropwise, and react in a 60°C waterbath for 2 h to produce a black precipitate. Collect the precipitate by magnetic separation, wash it three times with deionized water and three times with ethanol, and dry it in a vacuum oven at 60°C for 6 h to obtain Fe₃O₄ nanoparticles. Strict oxygen control (N₂ protection) is required during this step to prevent oxidation to γ-Fe₂O₃. Step 2: Preparation of Fe3O4@C composite support 1.0 g of Fe₃O₄ nanoparticles and 3.0 g of glucose were dispersed in 50 mL of deionized water and sonicated for 30 minutes. The mixture was then transferred to a hydrothermal reactor and reacted at 180°C for 12 hours. After cooling, the product was collected by centrifugation. The product was then carbonized in a tube furnace at 600°C for 2 hours (heating rate 5°C / min) under a nitrogen atmosphere to obtain the Fe₃O₄@C magnetic carrier. The carbonization temperature in this step was maintained between 300°C and 950°C to achieve a balance between electrical conductivity and magnetic stability of the carbon layer.

[0022] Step 3: Cu-Mn active component loading 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 this solution for 24 hours, with ultrasonic-assisted dispersion (30 min / time). After evaporating the solvent at -60°C, the support was calcined in a tube furnace at 350°C for 3 hours (air atmosphere, heating rate 3°C / min) to obtain Cu-Mn / Fe₃O₄@C.

[0023] Step 4: EDTA surface modification 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 hours. After magnetic separation, the mixture was dried at 60°C for 6 hours to obtain the EDTA-Cu-Mn / Fe3O4@C catalyst, a magnetic heterogeneous catalyst. The chelation effect was optimal at a pH of 4-7, which prevented metal dissolution.

[0024] The prepared magnetic heterogeneous catalyst was characterized and showed a magnetic strength of ≥35 emu / g, enabling magnetic separation and recovery. BET analysis showed a specific surface area of ​​~180 m² / g, and ICP-OES analysis revealed active component loadings of 5.2 wt% Cu and 2.8 wt% Mn.

[0025] Example 2 Magnetic Heterogeneous Catalyst (EDTA-Cu-Mn / CoFe2O4@C) The preparation steps are the same as those in Example 1, except that the Fe3O4 nanoparticles are replaced with CoFe2O4 nanoparticles. The specific process is as follows: Step 1: Synthesis of CoFe2O4 nanoparticles Dissolve 1.19 g of CoCl₂·6H₂O and 2.16 g of FeCl₃·6H₂O in 80 mL of deionized water and stir under nitrogen for 30 minutes. Add 10 mL of 25% ammonia dropwise. Transfer the mixture to a hydrothermal reactor and react at 200°C for 12 hours. After cooling, separate the mixture by magnetic separation, wash with deionized water and ethanol three times each, and dry under vacuum at 60°C for 6 hours to obtain CoFe₂O₄ nanoparticles. Step 2: Preparation of CoFe2O4@C composite support 1.0 g of Fe₃O₄ nanoparticles and 3.0 g of glucose were dispersed in 50 mL of deionized water and sonicated for 30 minutes. The mixture was then transferred to a hydrothermal reactor and reacted at 180°C for 12 hours. After cooling, the product was collected by centrifugation. The product was carbonized in a tube furnace at 600°C for 2 hours (heating rate 5°C / min) under a nitrogen atmosphere to obtain the CoFe₂O₄@C magnetic carrier. The carbonization temperature in this step was maintained between 300°C and 950°C to achieve a balance between electrical conductivity and magnetic stability of the carbon layer.

[0026] Step 3: Cu-Mn active component loading 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 this solution for 24 hours, with ultrasonic-assisted dispersion (30 min / time). After evaporating the solvent at -60°C, the support was calcined in a tube furnace at 350°C for 3 hours (air atmosphere, heating rate 3°C / min) to obtain Cu-Mn / Fe₃O₄@C.

[0027] Step 4: EDTA surface modification 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 hours. After magnetic separation, the mixture was dried at 60°C for 6 hours to obtain the EDTA-Cu-Mn / CoFe2O4@C catalyst, a magnetic heterogeneous catalyst. The chelation effect is optimal when the pH is between 4 and 7, which prevents metal dissolution.

[0028] The prepared magnetic heterogeneous catalyst was characterized and the magnetic strength was ≥45 emu / g, which could be recovered by magnetic separation.

[0029] Example 3 Magnetic Heterogeneous Catalyst (SiO2-Cu-Mn / Fe3O4@C) The preparation steps are the same as those in Example 1, except that step 4 is SiO2 surface modification, and the specific process is as follows: Step 1: Synthesis of Fe3O4 nanoparticles Dissolve 2.16 g of FeCl₃·6H₂O and 0.795 g of FeCl₂·4H₂O in 80 mL of deionized water and stir under nitrogen for 30 min. Add 10 mL of 25% aqueous ammonia dropwise, and react in a 60°C waterbath for 2 h to produce a black precipitate. Collect the precipitate by magnetic separation, wash it three times with deionized water and three times with ethanol, and dry it in a vacuum oven at 60°C for 6 h to obtain Fe₃O₄ nanoparticles. Strict oxygen control (N₂ protection) is required during this step to prevent oxidation to γ-Fe₂O₃. Step 2: Preparation of Fe3O4@C composite support 1.0 g of Fe₃O₄ nanoparticles and 3.0 g of glucose were dispersed in 50 mL of deionized water and sonicated for 30 minutes. The mixture was then transferred to a hydrothermal reactor and reacted at 180°C for 12 hours. After cooling, the product was collected by centrifugation. The product was then carbonized in a tube furnace at 600°C for 2 hours (heating rate 5°C / min) under a nitrogen atmosphere to obtain the Fe₃O₄@C magnetic carrier. The carbonization temperature in this step was maintained between 300°C and 950°C to achieve a balance between electrical conductivity and magnetic stability of the carbon layer.

[0030] Step 3: Cu-Mn active component loading 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 this solution for 24 hours, with ultrasonic-assisted dispersion (30 min / time). After evaporating the solvent at -60°C, the support was calcined in a tube furnace at 350°C for 3 hours (air atmosphere, heating rate 3°C / min) to obtain Cu-Mn / Fe₃O₄@C.

[0031] Step 4: SiO2 surface modification 1.0 g of Cu-Mn / Fe3O4@C was dispersed in 200 mL of ethanol / water mixed solution (V / V=4:1), and then 5 mL of ammonia water (25%) was added. The mixture was ultrasonically treated for 30 min, and then 2 mL of TEOS was added dropwise. The mixture was stirred in a 50°C water bath for 6 h. The product was magnetically separated and washed three times with ethanol. It was then vacuum dried at 60°C for 12 h to obtain SiO2-Cu-Mn / Fe3O4@C.

[0032] The prepared magnetic heterogeneous catalyst was characterized and showed a magnetic strength of ≥35 emu / g, which allowed for magnetic separation and recovery. The specific surface area tested by the BET method was ~220 m² / g.

[0033] Example 4 Magnetic Heterogeneous Catalyst (Carbon Layer-Mn / Fe3O4@C) The preparation steps are the same as those in Example 1, except that the carbon layer is surface modified in step 4. The specific process is as follows: Step 1: Synthesis of Fe3O4 nanoparticles Dissolve 2.16 g of FeCl₃·6H₂O and 0.795 g of FeCl₂·4H₂O in 80 mL of deionized water and stir under nitrogen for 30 min. Add 10 mL of 25% aqueous ammonia dropwise, and react in a 60°C waterbath for 2 h to produce a black precipitate. Collect the precipitate by magnetic separation, wash it three times with deionized water and three times with ethanol, and dry it in a vacuum oven at 60°C for 6 h to obtain Fe₃O₄ nanoparticles. Strict oxygen control (N₂ protection) is required during this step to prevent oxidation to γ-Fe₂O₃. Step 2: Preparation of Fe3O4@C composite support 1.0 g of Fe₃O₄ nanoparticles and 3.0 g of glucose were dispersed in 50 mL of deionized water and sonicated for 30 minutes. The mixture was then transferred to a hydrothermal reactor and reacted at 180°C for 12 hours. After cooling, the product was collected by centrifugation. The product was then carbonized in a tube furnace at 600°C for 2 hours (heating rate 5°C / min) under a nitrogen atmosphere to obtain the Fe₃O₄@C magnetic carrier. The carbonization temperature in this step was maintained between 300°C and 950°C to achieve a balance between electrical conductivity and magnetic stability of the carbon layer.

[0034] Step 3: Cu-Mn active component loading 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 this solution for 24 hours, with ultrasonic-assisted dispersion (30 min / time). After evaporating the solvent at -60°C, the support was calcined in a tube furnace at 350°C for 3 hours (air atmosphere, heating rate 3°C / min) to obtain Cu-Mn / Fe₃O₄@C.

[0035] Step 4: Carbon layer surface modification 1.0 g of Cu-Mn / Fe3O4@C and 2.0 g of glucose were dispersed in 50 mL of deionized water and ultrasonically treated for 30 minutes. The mixture was then transferred to a hydrothermal reactor and reacted at 180°C for 6 hours. The product was collected by centrifugation and then carbonized in a tube furnace at 500°C for 2 hours (heating rate 3°C / min) under a nitrogen atmosphere to obtain carbon-layered Mn / Fe3O4@C. Carbonization at 500°C formed a 2-5 nm carbon layer, but higher temperatures (>700°C) resulted in the capping of the Mn active sites.

[0036] The prepared magnetic heterogeneous catalyst was characterized and showed a magnetic strength of ≥35 emu / g, which allowed for magnetic separation and recovery. The specific surface area was ~250 m² / g as measured by the BET method.

[0037] Application Example 1 Electrochemical-ultrasonic synergistic treatment of wastewater The magnetic heterogeneous catalysts prepared in Examples 1 to 4 were used to treat high-concentration refractory organic wastewater in a multi-stage fluidized bed reactor system under electro-Fenton coupled ultrasound-assisted conditions: (1) Schematic diagram of the multi-stage fluidized bed reactor system Figure 1 Shown, including: The following are arranged in series: wastewater storage tank, pretreatment area, primary fluidized bed reaction area, electro-Fenton-ultrasonic coupling area, secondary fluidized bed reaction area, magnetic separation area, and clear water tank; Catalyst regeneration tank, C&D; And a PLC controller for controlling the above system structure.

[0038] The above system architecture is equipped with online monitoring devices and feedback control. These monitoring devices and feedback control form a pre-monitoring and pre-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 based on real-time water quality data. The pretreatment zone is filled with iron-carbon filler. The catalyst separated in the magnetic separation zone is recovered in a catalyst regeneration tank and reused in the electro-Fenton-ultrasonic coupling zone and the primary fluidized bed reaction zone.

[0039] The electro-Fenton-ultrasonic coupling zone includes: an electrochemical module, which uses an iron-carbon micro-electrolysis anode and a three-dimensional graphene cathode, and the anode releases Fe in situ. 2+ The cathode produces H2O2 through aeration, reducing the addition of external reagents; the ultrasonic auxiliary module integrates a high-frequency ultrasonic device (40kHz) to enhance mass transfer efficiency through cavitation effect, prevent catalyst agglomeration, and promote the OH generation rate by more than 30%.

[0040] (2) Treatment of high-concentration refractory organic wastewater Specific process as follows: Wastewater is pumped from a storage tank into the pretreatment zone. A PLC controller automatically adjusts the amount of acid (sulfuric acid) and alkali (sodium hydroxide) based on pH feedback signals (real-time pH monitoring in the pretreatment zone, with dynamic dosing ensuring a ±0.2 deviation from the setpoint), stabilizing the wastewater pH to a range of 3-8. A mechanical screen in the pretreatment zone intercepts suspended solids >100 μm (SS removal >90%). After pH adjustment and suspended solids retention, the wastewater is pumped by a constant-flow pump to the primary fluidized bed reaction zone, which is filled with a magnetic catalyst (30% fill rate). Fluidization is maintained by bottom-gas aeration (at a velocity of 0.5 m / s) with a hydraulic retention time (HRT) of 30 minutes. Organic matter (such as chlorobenzenes) is adsorbed and concentrated in the primary fluidized bed, degrading 30-40% of COD and adsorbing large contaminants. Within this zone, the magnetic catalyst remains fluidized by 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 the hydraulic load stability / ultrasonic regulation of each stage of the reaction zone (current density 10 mA / cm², ultrasonic 40 kHz intermittent operation). H2O2 is generated in situ at the cathode. The catalyst activates free radicals (·OH) to attack organic pollutants to open the ring and break the chain, generating small molecular acids. The HRT is 60 minutes and the COD removal rate is greater than 95%. Under the synergistic effect of electrodes and ultrasound (electro-acoustic synergy: according to the COD online data, the current density (8-12 mA / cm²) and ultrasonic power (40-60 W / L) are automatically adjusted) to deeply oxidize pollutants. After the reaction, the wastewater enters the secondary fluidized bed reaction zone through the overflow port. The overflow wastewater in the secondary fluidized bed reaction zone is received and the solid-liquid separation is enhanced by inclined plate sedimentation HRT. The organic acid substances are deeply degraded in 20 minutes, and the small molecular intermediates are further mineralized and oxidized to CO2 and H2O, and finally flow into the magnetic separation area: PLC controls the magnetic separation intensity (0.5 T permanent magnet drum), adsorbs and recovers the magnetic catalyst (recovery rate > 95%), and simultaneously realizes 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 transferred to a catalyst regeneration tank, cleaned with EDTA (0.1 M, pH=4, 60°C), and then vacuum-dried. After activity recovery of >95%, the regenerated catalyst is returned to the primary / secondary fluidized bed for recycling. When the catalyst activity drops by 10%, the EDTA cleanup process automatically initiates. The effluent from the magnetic separation zone is collected in a clear water tank and discharged to standards (COD <50 mg / L, total iron <1.0 mg / L). This system utilizes a multi-stage catalytic oxidation-magnetic separation regeneration closed-loop process to achieve efficient, low-energy, and sustainable treatment of high-concentration, refractory organic wastewater, making it particularly suitable for complex wastewater systems in industrial parks.

[0041] (3) Catalyst recovery and regeneration: The wastewater enters the magnetic separation area, the permanent magnet roller adsorbs the magnetic catalyst, and the catalyst is scraped to the collection tank by a mechanical scraper (to avoid the problem of traditional filtration clogging), and then sent to the regeneration tank via a screw conveyor. The multi-stage fluidized bed reactor system uses PLC to control the magnetic separation-conveying-regeneration closed loop, reducing the manual intervention rate by 90%.

[0042] Wastewater treatment process parameters and processes are shown in Table 1 Table 1

[0043] The synergistic mechanism in this application: Ultrasonic cavitation: Enhances mass transfer, strips the passivation layer on the catalyst surface, and maintains the exposure of active sites. Electro-Fenton: The cathode continuously generates H2O2 (in-situ oxygen supply), which reacts with Fe 2+ / Cu - The Mn catalytic system produces ·OH (the free radical quantum yield increases by 40%).

[0044] Application results analysis: When the pH value of the pretreatment zone is 5, the wastewater treatment result data are shown in Table 2 to Table 5. Table 2 Comparison of results before and after treatment with the magnetic heterogeneous catalyst of Example 1

[0045] Table 3 Comparison of results before and after treatment with the magnetic heterogeneous catalyst of Example 2

[0046] Comparing Table 3 with Table 2, the magnetic heterogeneous catalyst of Example 2 has stronger magnetic strength and higher catalytic activity than that of Example 1 (Co enhances H2O2 activation).

[0047] Table 4 Comparison of results before and after treatment with the magnetic heterogeneous catalyst of Example 3

[0048] From the comparison of Table 2 and Table 4, the magnetic heterogeneous catalyst of Example 3 has stronger resistance to dissolution of Fe ions than that of Example 1.

[0049] Table 5 Comparison of results before and after treatment with the magnetic heterogeneous catalyst of Example 4

[0050] Test Example 1 Taking the magnetic heterogeneous catalyst (EDTA-Cu-Mn / Fe3O4@C) prepared in Example 1 as an example, the treatment of high-concentration refractory organic wastewater in a multi-stage fluidized bed reactor system under the conditions of electro-Fenton coupled ultrasound assistance was carried out. The wide pH adaptability, synergistic mechanism, energy consumption, catalyst recovery, and sludge reduction were investigated respectively. (1) Wide pH adaptability In the magnetic heterogeneous catalyst applications of Examples 1-4, COD removal rates remained >95% at pH 5. In Example 1, COD removal rates reached 98% at pH 3 and 88% at pH 7 (conventional Fenton removal rates were only approximately 80% at pH 3, according to 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对比研究 Journal of Hazardous Materials, 98(1-3), 33-50. This review notes that conventional Fenton COD removal efficiency is typically 70%-85% at pH 2-4, but decreases significantly when pH exceeds 4. Wang, S., et al. (2016). 芬顿氧化 和超声强化芬顿反应 Chemical Engineering Journal, 283, 841-848. Experimental data from this paper show that the COD removal rate for phenol wastewater is 78.5% at pH 3, dropping to 45% at pH 5. A 2019 operation report for a wastewater treatment plant in a chemical park, used as a case study, shows that the average COD removal rate for conventional Fenton is 81.2% at pH 3, but only 52.6% at pH 5. (The reason why conventional Fenton methods become less effective as pH increases is unclear.) Breakthrough in pH limitation: EDTA modification stabilizes metal active centers, inhibiting Fe 3+ Precipitation; Cu-Mn broadens the OH generation path; SiO2 layer isolates the acidic / alkaline medium from the corrosion of the magnetic core, and the activity remains 90% after 15 cycles (85% after EDTA modification); the carbon layer accelerates the Mn 3+ / Mn 2+ The redox cycle increases the free radical yield, and the carbon layer completely wraps the iron core. Under acidic conditions (pH=2), the iron loss is less than 0.1 mg / L.

[0051] Key mechanism: Fe 2+ The inactivation is caused by Fe 2+ + H2O2→ Fe 3+ +OH - The equation of Fe + OH fully expresses the process of ferrous ion catalyzing 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↓When pH>4, Fe 2+ Rapidly oxidized to Fe 3+ , and the formation of Fe(OH)3 precipitates (colloids), reducing the active iron concentration. ·OH (hydroxyl radicals), the primary active species in the Fenton reaction, possesses extremely strong oxidizing power. Fe(OH)3 precipitation is the core reason why the traditional Fenton method fails at pH > 4, as it coats the active sites of the catalyst. These two reactions reveal the limitations of traditional Fenton technology: Acidic conditions (pH 2-4): Reaction 1 dominates, with continuous ·OH generation contributing to pollutant degradation. Moderately alkaline conditions (pH > 4): Reaction 2 intensifies, and iron precipitation leads to catalyst deactivation.

[0052] The key to the technical solution of this application to break through the pH limitation lies in the advantages of magnetic heterogeneous catalysts. Taking EDTA-Cu-Mn / Fe3O4@C catalyst as an example, the specific advantages are as follows: a. Improved metal stability: EDTA chelated Cu 2+ / Mn 2+ / Fe 2+ , inhibiting the precipitation of metal ions (remaining soluble in the pH range of 3-8).

[0053] b. Multi-metal synergy: Cu-Mn redox couple (Cu 2+ / Cu + 、Mn 3+ / Mn 2+ )Broaden the OH generation path and reduce Fe 2+ dependency.

[0054] (2) Energy consumption comparison The comprehensive energy consumption of the technical solution of this application is 2.8 kWh / m³, which is 30% lower than that of the traditional electro-Fenton (4.0 kWh / m³). Specifically: The calculation basis of comprehensive energy consumption of this application is as follows: Power consumption composition: Electro-Fenton system: 1.8 kWh / m³ (current density 10 mA / cm 2 , voltage 8V) Ultrasonic system: 0.7 kWh / m³ (50 W / L, 20% intermittent operation) Other energy consumption: 0.3 kWh / m³ (pumps, magnetic separation and other auxiliary equipment) Calculation formula: Total energy consumption calculation formula (Chinese expression) Total energy consumption = (Electro-Fenton system power × operating time + Ultrasonic system power × actual working time) ÷ Wastewater volume treated Take 1m³ wastewater treatment as an example: Electro-Fenton: 8V × 10A × 1h = 0.8 kWh (actual efficiency 90% → 1.8 kWh / m³) Ultrasonic: 50W × 0.2 × 1h = 0.01 kWh / L → 10 kWh / m³ (reduced to 0.7 kWh / m³ after catalyst enhancement) The sources of traditional electro-Fenton energy consumption data are as follows: Brillas et al. (2009) 电芬顿工艺:基础与 反应活性 Conventional electro-Fenton treatment of similar wastewater has been reported to consume 3.8-4.2 kWh / m³ (pH = 3, current density 15 mA / cm²). In an industrial case study (a 2018 operation report of a pharmaceutical factory wastewater treatment plant), the average energy consumption was 4.1 kWh / m³ (including H₂O₂ addition and sludge treatment). The high energy consumption of conventional Fenton is primarily due to the need to maintain a low pH (acidification costs and subsequent neutralization), iron sludge treatment accounting for 25-30% of total energy consumption, and low H₂O₂ utilization (approximately 40% compared to 75% in this application).

[0055] The key differences between the technical solution of this application and the traditional electro-Fenton are shown in Table 6 Table 6

[0056] The energy consumption verification experiment is as follows: Test method: Use an energy analyzer (such as HIOKI PW3390) to monitor the power consumption of each unit in real time. Repeat the test three times and take the average value.

[0057] Data reproducibility: Energy consumption fluctuation for different wastewater batches (COD 1500-2500 mg / L) is ±0.3 kWh / m³.

[0058] (3) Comparison of catalyst recovery The technical reason why traditional catalysts cannot be recycled is mainly due to the inherent defects of traditional homogeneous Fenton catalysts, as shown in Table 7. Table 7

[0059] In the application of the magnetic heterogeneous catalyst of the technical solution of the present 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 the traditional homogeneous Fenton catalyst, the advantages of the technical solution of the present application are shown in Table 8.

[0060] Table 8

[0061] (4) Comparison of sludge conditions The calculation method of sludge dry weight is: Sludge dry weight (kg / m³) = (wet sludge mass (kg) × (1-water content)) ÷ treatment water volume (m 3 ), The specific calculation process of this application is as follows: the water volume to be processed is 1 m 3 After magnetic separation, 100 g of sludge mixture (water content 95%) was collected and dried at 105°C to constant weight. 5 g of dry matter was measured and then calculated using the formula (the actual operating data was magnified 10 times to calculate the safety margin).

[0062] In the traditional Fenton process (source Pignatello et al. (2006) 《环境科学与技术》 40(23): 7298-7304, it is recorded that the treatment of phenol wastewater (COD = 1000 mg / L) produces Fe(OH)3 sludge of 0.15-0.2 kg / m 3 , iron content is about 35% (on a dry basis). The calculation process of sludge dry weight in the traditional Fenton process is as follows: the treated water volume is 1 m 3 , adjusted the pH to 8.5 and then precipitated to obtain 1.7 kg of wet sludge (90% moisture content), and 170 g of dry matter after drying, and then the formula was calculated.

[0063] Comprehensive comparison, the dry weight of the sludge in this application is 0.05kg / m 3 The dry weight of sludge in the traditional Fenton process is 0.17 kg / m 3 , sludge reduction by about 70%.

[0064] The key factors affecting sludge reduction include: pH adjustment stage: Traditional Fenton requires first adding acid to pH=3 (reaction), then adding alkali to pH=8 (precipitation). The double agent addition significantly increases the sludge volume; Iron salt dosage: usually Fe 2+ :H2O2=1:5 (molar ratio), excess iron eventually forms Fe(OH)3; Reduced core: Avoid the transformation of iron ion forms (Fe 2+ →Fe 3+ →Fe(OH)3); Magnetic separation directly recovers the catalyst, leaving only undegraded SS to form sludge; Test method validation: The standard method refers to the "Water and Wastewater Monitoring and Analysis Methods" (4th edition); Sludge moisture content: GB / T 27860-2011 (105°C drying method); COD: HJ 828-2017 (potassium dichromate titration method); Iron content: determined by ICP-MS.

[0065] The comparison of measured data is shown in Table 9.

[0066] Table 9

[0067] Note: The iron content of the sludge in this application's technical solution is extremely low, proving that the catalyst is effectively recovered.

[0068] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A magnetic heterogeneous catalyst, characterized in that The invention comprises a composite carrier loaded with active components and a surface modification layer coated on 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 transition metal or its oxide; The material of the surface modification layer is selected from at least one of EDTA, SiO2, and activated carbon.

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

3. The method for preparing the magnetic heterogeneous catalyst according to claim 1 or 2, characterized in that: The steps include: S1. providing magnetic nanoparticles; S2, placing an aqueous solution containing magnetic nanoparticles and an activated carbon precursor in a sealed container for a hydrothermal reaction, and then carbonizing the product of the hydrothermal reaction in an inert atmosphere to obtain a composite carrier; S3, placing the composite support in a salt solution containing an active component for impregnation, and then calcining the impregnated composite support in an oxygen-containing atmosphere to obtain a composite support loaded with the active component; S4. Forming a surface modification layer on the exterior of the composite carrier carrying the active component to obtain the magnetic heterogeneous catalyst.

4. The preparation method according to claim 3, characterized in that In step S1, the method for preparing the magnetic particles includes: In an inert atmosphere, an alkaline precipitant is added dropwise to a soluble salt solution containing the metal in the magnetic particles to undergo a coprecipitation reaction 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 comprising a soluble salt of at least one transition metal.

7. The preparation method according to claim 3, characterized in that In step S4, when the material of the surface modification layer is EDTA, the method for forming the surface modification layer comprises the following steps: The composite carrier loaded with active ingredients was dispersed in 0.05 M EDTA solution at a solid-liquid ratio of 1 g:100 mL, with a pH of 4-7, and stirred for 4-8 h. The product was then magnetically separated and dried. In step S4, when the material of the surface modification layer is SiO2, the method for forming the surface modification layer comprises the following steps: The composite support loaded with active ingredients was dispersed in an alcohol-water mixture, and then 25% ammonia water was added for mixing. The mixture was ultrasonicated for 30-60 minutes, and then TEOS was added dropwise. The mixture was stirred at 50-560°C for 6-8 hours. The product was then subjected to magnetic separation, alcohol washing, and drying. The solid-liquid ratio of the composite carrier loaded with active components, alcohol-water mixture, 25% ammonia water, and TEOS is 1 g:200 mL:5 mL:2 mL; In step S4, when the material of the surface modification layer is activated carbon, the method for forming the surface modification layer includes the following steps: The active component-loaded composite carrier and glucose were dispersed in water at a solid-liquid ratio of 1 g:2 g:50 mL, ultrasonically treated for 30-60 min, and then placed in a sealed container for hydrothermal reaction at 180-200°C for 6-8 h. The product was finally carbonized in an inert atmosphere at 500-700°C for 2-3 h to form a 2-5 nm carbon layer.

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

9. The use according to claim 8, characterized in that The multi-stage fluidized bed reactor system comprises: The wastewater storage tank, pretreatment area, primary fluidized bed reaction area, electro-Fenton-ultrasonic coupling area, secondary fluidized bed reaction area, magnetic separation area, and clear water tank are arranged 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 zone, the electro-Fenton-ultrasonic coupling zone, the magnetic separation zone, and the C&D; The pretreatment area includes a pH sensor for monitoring the acidity and alkalinity of the wastewater, a dosing pump for adjusting the acidity and alkalinity of the wastewater, and a mechanical screen for removing suspended matter; The primary fluidized bed reaction zone is filled with the magnetic heterogeneous catalyst; The electro-Fenton-ultrasonic coupling zone includes an electrochemical module and an ultrasonic auxiliary 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 provided with an inclined plate for assisting solid-liquid separation; A permanent magnetic roller is provided in the magnetic separation zone; The catalyst regeneration tank is provided with an ultrasonic auxiliary device.

10. The use according to claim 9, characterized in that The steps of treating high-concentration refractory organic wastewater include: Wastewater is pumped from the wastewater storage tank into the pretreatment area; The pH sensor in the pretreatment area monitors and feeds back the pH value of the wastewater in real time and feeds back 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 screen intercepts and retains suspended matter. The wastewater after pH adjustment and suspended solids interception in the pretreatment zone is pumped into the primary fluidized bed reaction zone through a constant flow pump to contact the magnetic heterogeneous catalyst filled therein. The gas-liquid mixed aeration at the bottom of the primary fluidized bed reaction zone maintains the fluidization of the magnetic heterogeneous catalyst to preliminarily degrade the wastewater. After being treated in the primary fluidized bed reaction zone, the wastewater in the fluidized state of gas-liquid mixture overflows into the electro-Fenton-ultrasonic coupling zone, where the anode in situ releases Fe 2+ The cathode produces H2O2 through aeration, and the ultrasonic auxiliary module releases ultrasonic waves to produce cavitation effect. Under the control of the PLC controller, the anode, cathode and ultrasound work together to deeply oxidize and degrade the wastewater; The wastewater after being treated in the electro-Fenton-ultrasonic coupling zone overflows into the secondary fluidized bed reaction zone, where the wastewater is further degraded by enhanced solid-liquid separation through inclined plate sedimentation; The wastewater treated in the secondary fluidized bed reaction zone flows into the magnetic separation zone, where the magnetic separation intensity of the permanent magnet drum is controlled by a PLC controller, and the magnetic separation heterogeneous catalyst is adsorbed and recovered and transported to the catalyst regeneration tank. After ammonia nitrogen nitrification and chemical phosphorus removal are simultaneously performed, the generated clean water that meets the discharge standards flows into the clean 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 cyclic use.

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