Array-type electro-catalysis ozonization water treatment device based on annular electric field enhanced mass transfer and application method of array-type electro-catalysis ozonization water treatment device

Abstract

The invention discloses an array type electro-catalysis ozonization water treatment device based on annular electric field enhanced mass transfer and an application method, and is characterized in that a carbon felt loaded by an iron-based nitrogen coordination porous carbon active layer is used as an annular cathode, and forms a coaxial annular electric field structure with a microporous aeration titanium anode arranged in the center; the cathode active layer is subjected to ozonization reaction through (1) catalytic decomposition of ozone introduced by the anode and (2) in-situ reduction of ozone to generate hydrogen peroxide, hydroxyl radicals are synergistically generated, a composite oxidation system is constructed on the surface of the annular cathode and in the space of the reactor, and oxidation of refractory organics in the high-salinity wastewater is realized; the water treatment requirements under different degradation-resistant organic matter load conditions can be met.

Description

Technical Field

[0001] This invention relates to an array-type electrocatalytic perozonation water treatment device and application method based on enhanced mass transfer through a ring electric field, belonging to the field of water pollution control. Background Technology

[0002] Advanced oxidation technologies (AOPs) are an effective means of treating recalcitrant organic wastewater. Their core lies in generating highly oxidizing hydroxyl radicals (·OH) to achieve deep mineralization of pollutants. Electrocatalytic perozonation, as an emerging AOP, couples an electrochemical process with ozone oxidation to synergistically generate ·OH, exhibiting higher oxidation efficiency than either technology alone, and shows great promise in the field of advanced industrial wastewater treatment.

[0003] However, existing electrocatalytic perozonation technologies still face systemic bottlenecks in achieving the synergy between "cathode-based ozone reduction" and "anode-based ozone activation," hindering their treatment efficiency and engineering applications. Specifically, this manifests in two aspects: Firstly, in terms of reactor configuration and electric field distribution, traditional designs, such as the planar electrode used in patent CN101928065A, suffer from uneven electric field distribution, limiting ozone mass transfer efficiency. Secondly, while patent CN02251073.7 proposes using an electric field to enhance ozone mass transfer, its core focus is on promoting bubble splitting through the electric field to improve mass transfer, failing to address the issue of synergistic regulation of the anode and cathode reaction fields. Some studies have attempted to improve these problems through reactor structure optimization. For example, patent CN115092993B discloses an electrocatalytically coupled ozone catalytic reactor, employing a mixed filling method of three-dimensional electrode packing and ozone catalytic packing, attempting to achieve synergy between electrocatalysis and ozone catalysis within the same reaction space. However, while this design broadens the conversion pathway of ·OH, its core still relies on the heterogeneous catalytic reaction on the filler surface. It fails to achieve a directional and coordinated electron transfer process of ozone molecules on the anode and cathode surfaces, and has not yet developed an effective design for the synergistic mechanism of "cathode reduction of ozone to hydrogen peroxide" and "anodic activation of ozone to hydroxyl radicals." In the design and system integration of oxidation pathways, existing technologies often spatially or temporally separate the ozone introduction, activation, and reduction stages, resulting in a single oxidation pathway and difficulty in significantly improving the generation and utilization efficiency of active species. For example, although patent CN117682634B integrates ozone generation and catalytic oxidation units, its focus remains on the in-situ supply of ozone and the heterogeneous catalytic decomposition process. It fails to effectively utilize the cathode to directionally reduce ozone to hydrogen peroxide, a key intermediate, and also does not fully integrate the direct activation effect of the anode on ozone. Patent CN106335998A proposes an electrocatalytic ozone oxidation process with synergistic oxidation of anode and cathode. A mixture of ozone and oxygen is first electrochemically activated by a porous metal anode, then reduced to hydrogen peroxide by a cathode, achieving a sequential series connection of the anode and cathode. This design initially embodies the concept of synergistic anode-cathode reaction, but it is essentially a spatially segmented process, failing to achieve real-time synergy and mutual promotion between "anodic activation of ozone" and "cathode reduction of ozone" within the same reaction field. Patent CN110845057A discloses an electrochemically coupled ozone micro / nanobubble treatment system, employing micro / nanobubble technology to enhance ozone mass transfer while utilizing anodic oxidation and cathodic reduction. However, the core of this system lies in the optimization of bubble morphology and the simple superposition of electrochemical processes, lacking precise control over the crucial pathway of ozone's directional conversion to hydrogen peroxide. In addition, patent CN101634035 discloses a method and apparatus for the synergistic electrochemical generation of ozone and hydrogen peroxide in a neutral medium, which uses a proton exchange membrane to separate a cathode chamber and an anode chamber, generating ozone at the anode and hydrogen peroxide at the cathode, respectively.While this design achieves the co-generation of two oxidants in the same tank, its membrane separation structure strictly separates the anode and cathode reactions, essentially circumventing the direct reduction of ozone at the cathode. This prevents the utilization of ozone itself as a cathode reactant to generate hydrogen peroxide, thus failing to construct the intrinsically coupled perozonation reaction mechanism triggered by "anodic activation of ozone" and "cathode reduction of ozone." In summary, existing improvements fail to fundamentally integrate the three key dimensions of uniform electric field construction, enhanced mass transfer, and synergistic effects of multiple oxidation pathways. Therefore, developing a novel device capable of achieving uniform electric field distribution and enhanced endogenous mass transfer through reactor innovation, and integrating the synergistic mechanisms of "cathode reduction of ozone" and "anodic activation of ozone," has become a crucial direction for promoting the efficient and stable engineering applications of this technology.

[0004] Therefore, this invention aims to develop an array-type electrocatalytic perozonation water treatment device and its application method based on enhanced mass transfer using a ring electric field, in order to solve the aforementioned bottlenecks. This invention improves the electric field distribution and optimizes the reactant mass transfer pathway by designing concentric ring electrodes. Utilizing an Fe-NC active layer, it achieves perozonation through ① catalytic decomposition of ozone introduced at the anode, and ② in-situ reduction of ozone at the cathode to generate hydrogen peroxide, synergistically generating hydroxyl radicals. Through an expandable array design, the device combines enhanced mass transfer, efficient catalysis, and flexible operation in multiple modes (electrolysis, electro-Fenton, catalytic ozone oxidation, and electrocatalytic perozonation), significantly improving the yield and utilization efficiency of ·OH, enhancing the system's water quality adaptability, and providing an efficient and stable solution for purifying recalcitrant high-salt wastewater. Summary of the Invention

[0005] 1. This invention relates to an array-type electrocatalytic perozonation water treatment device and its application method based on enhanced mass transfer via a ring electric field. The device is characterized by using a carbon felt supported on an iron-based nitrogen-coordinated porous carbon active layer as the ring cathode, which, together with a centrally arranged microporous aerated titanium anode, forms a coaxial ring electric field structure. The cathode active layer ① catalytically decomposes ozone introduced by the anode, ② in-situ reduces ozone to generate hydrogen peroxide, undergoing a perozonation reaction, and synergistically generates hydroxyl radicals. A composite oxidation system is constructed on the surface of the ring cathode and within the reactor space, achieving the oxidation of recalcitrant organic matter in high-salt wastewater. This method can adapt to water treatment requirements under different recalcitrant organic matter load conditions. The specific methods for preparing the ring cathode, constructing the reactor, and applying the device are as follows: (1) Using MIL-88B (Fe) as a precursor, pyrolyze it under high-purity argon at 730~770℃ for 2.5~3.5 h to obtain a black iron oxide powder. Weigh 0.20~0.22 g of the powder and disperse it in 150~180 mL of nitric acid solution with a concentration of 2.0~2.2 mol / L. Stir the reaction in a water bath at 75~85℃ for 8~12 h. After the reaction, wash it three times with ultrapure water and dry it at 75~85℃ to obtain iron-nitrogen-carbon powder, denoted as Fe-NC. (2) Physicochemical characteristics of Fe-NC: It exhibits a highly graphitized structure. The intensity ratio of the defect peak to the graphite peak in the Raman spectrum is 0.8~0.9. Iron is anchored in the carbon matrix in an atomically dispersed form. Its active sites have an unsaturated coordination environment composed of nitrogen atoms and carbon atoms. Iron atoms form an unsaturated four-coordinate structure by coordinating with three oxygen atoms and one nitrogen atom. The H2O2 selectivity is 35~40%, and the number of transferred electrons is 3.2~3.3. (3) Pretreatment of the annular cathode substrate: The carbon felt (5×20 cm) is placed in 100~150 mL of acetone, anhydrous ethanol and ultrapure water for ultrasonic cleaning for 30~60 min to remove surface impurities, and then dried at 75~85℃. (4) Preparation of active layer slurry: Weigh 0.3~0.4 g of carbon black and 0.075~0.085 g of Fe-NC prepared in step (1), add 1.0~1.2 mL of 60 wt% polytetrafluoroethylene emulsion, 150.0~180.0 mL of ultrapure water and 2.4~3.0 mL of isopropanol, and ultrasonically mix them evenly under ice-water bath conditions; (5) Loading and molding of Fe-NC annular cathode: The pretreated carbon felt is immersed in the active layer slurry, and after ultrasonic treatment to ensure that the catalyst is fully penetrated, it is fixed on the annular mold, dried and shaped at 75~85℃, and then calcined in nitrogen at 350~370℃ for 25~35 min at 5~8℃ / min. After cooling, Fe-NC annular cathode is obtained. (6) The aeration anode is a microporous aeration titanium (stainless steel) anode, which is cylindrical in shape and the surface active coating is ruthenium-iridium titanium coating, iridium-tantalum titanium coating, platinum-based coating and other highly active and stable coatings. (7) The electrocatalytic perozonation reaction module adopts a concentric circle configuration, with the annular cathode coaxially surrounding the outside of the central microporous aeration anode, and the anode and cathode connected to the positive and negative terminals of an external DC power supply respectively through wires; (8) Operating conditions: The reaction module operates within the following optimized parameter range: operating current is 1.0~2.5 A, reaction gas flow rate is 50~200 mL / min, and total dissolved solids are 7000~12000 mg / L; (9) Operating modes: By switching the gas source (O2 / O3) and the circuit on / off, four operating modes can be flexibly realized: electrolysis, electro-Fenton, catalytic ozone oxidation and electro-catalytic perozonation, to adapt to different treatment needs; (10) The array-type electrocatalytic perozonation water treatment device adopts an array arrangement and is composed of multiple reaction units. Each unit can operate independently or be flexibly connected in series and in parallel through built-in flow channels. The device is functionally adjustable. For high-concentration recalcitrant organic matter (COD about 300~18000 mg / L), multiple modules are connected in series to construct a step-by-step treatment, which serves as a pretreatment unit to improve the chemical structure of organic matter and enhance the biodegradability of wastewater. For large flow and low pollution load (COD about 130~300 mg / L), multiple modules can be connected in parallel to achieve mineralization of recalcitrant organic matter and ensure that the COD of the effluent meets the standard stably. Attached Figure Description

[0006] Figure 1 This is an electron micrograph of Fe-NC prepared according to the present invention; Figure 2 The selectivity and number of transferred electrons of the Fe-NC active ingredient H2O2 prepared in this invention; Figure 3 This is a schematic diagram of the electrocatalytic perozonation water treatment unit constructed according to the present invention; Figure Labels 1-Power supply, 2-Outlet, 3-Inlet, 4-Aeration anode, 5-Fe-NC loaded carbon felt cathode, 6-Conductive copper mesh, 7-Ozone inlet Figure 4 The diagram shows the degradation effect of the electrocatalytic perozonation water treatment unit constructed in this invention on fluconazole (FCZ). Figure 5 The diagram shows the degradation effect of the electrocatalytic perozonation water treatment unit constructed in this invention on COD in high-salt wastewater. Figure 6 This is a schematic diagram of the operation mode of the array-type electrocatalytic perozonation water treatment device based on enhanced mass transfer by a ring electric field constructed in this invention. 1-Grit chamber, 2-Grit chamber, 3-Primary sedimentation tank, 4-Biological treatment tank, 5-Secondary sedimentation tank, 6-Water pump, 7-Inlet valve, 8-Inlet, 9-Array-type electrocatalytic perozonation water treatment device with annular electric field enhanced mass transfer, 10-Ozone generator, 11-Check valve, 12-Flow meter, 13-Pressure gauge, 14-Disinfection tank Detailed Implementation The present invention will be described in further detail with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0007] Example 1: Fe-NC preparation method.

[0008] (1) Using MIL-88B (Fe) as a precursor, pyrolyze it for 2.5 to 3.5 h under the protection of high-purity argon at 730 to 770 °C to obtain a black iron oxide powder. Weigh 0.20 to 0.22 g of the powder and disperse it in 150 to 180 mL of nitric acid solution with a concentration of 2.0 to 2.2 mol / L. Stir the reaction in a water bath at 75 to 85 °C for 8 to 12 h. After the reaction, wash it three times with ultrapure water and dry it at 75 to 85 °C to obtain iron-nitrogen-carbon powder, denoted as Fe-NC.

[0009] Example 2: Preparation method of Fe-NC annular cathode.

[0010] (1) Cut the carbon felt into 5×20 cm size, place it in 100~150 mL of acetone, anhydrous ethanol and ultrapure water for 30~60 min of ultrasonic cleaning to remove surface impurities, and dry it at 75~85℃. (2) Weigh 0.3~0.4 g of carbon black and 0.075~0.085 g of Fe-NC prepared in step (1), add 1.0~1.2 mL of 60 wt% polytetrafluoroethylene emulsion, 150.0~180.0 mL of ultrapure water and 2.4~3.0 mL of isopropanol, and ultrasonically mix them evenly under ice-water bath conditions; (3) The pretreated carbon felt is immersed in the catalyst slurry. After ultrasonic treatment to ensure full penetration of the catalyst, it is fixed on the ring mold. It is first dried and shaped at 75~85℃, and then calcined in nitrogen at 350~370℃ for 25~35min at 5~8℃ / min. After cooling, the ring electrode is obtained. (4) Figure 1 Electron microscopy images show that iron atoms were successfully loaded onto the surface of the annular cathode; elemental surface scanning results confirmed that the nitrogen element was uniformly distributed. (5) Figure 2 The H2O2 selectivity of Fe-NC is 35-40%, and the number of transferred electrons is 3.2-3.3.

[0011] Example 3: Operation mode control of electrocatalytic perozonation water treatment unit.

[0012] (1) such as Figure 3 As shown, the electrocatalytic perozonation water treatment unit mainly includes a shell, a power supply system, and a gas supply system. The shell is a cylindrical container, with a concentric electrocatalytic assembly at its core. A microporous aeration anode 4 serves as the central component, and an Fe-NC annular cathode 5 is coaxially fixed around it. The annular cathode is connected to the negative terminal of the power supply 1 via a tightly fitted conductive copper mesh 6 on its outer side, while the anode is directly connected to the positive terminal. An inlet 3 is located at the bottom of the reactor, and an outlet 2 is located at the top. An external ozone generator 18 is connected to the central aeration anode 4 via a pipeline to supply ozone. (2) The treatment unit operates in continuous flow mode: wastewater is pumped into the reactor through inlet 3, and the gas supply and power supply are turned on at the same time. The reaction module operates within the following optimized parameter range: working current 1.0~2.5 A, reaction gas flow rate 50~200 mL / min, total dissolved solids 7000~12000 mg / L. The treatment unit can start and maintain the oxidation process. (3) The processing unit provides four operating modes: electrolysis mode (no gas supply, only electricity supply), which relies on direct electrochemical conversion; electro-Fenton mode (O2 supply, electricity supply), where H2O2 is generated by the annular cathode and triggers a heterogeneous Fenton reaction; catalytic ozone oxidation mode (O3 supply, no electricity supply), which uses the Fe-NC annular cathode to catalyze ozone decomposition; and electrocatalytic perozonation mode (O3 supply, electricity supply), which uses a dual-pathway synergistic oxidation through ozone catalytic decomposition and H2O2 perozonation by the annular cathode. (4) Electrocatalytic perozonation treatment unit, under experimental conditions of 1.0~2.5 A operating current, 7000~12000 mg / L total dissolved solids, 100~200 μmol / L fluconazole, O3 gas flow rate of 50~200 mL / min, using Fe-NC annular cathode and ruthenium-iridium-titanium coated microporous aerated titanium anode, such as Figure 4 As shown, the electrocatalytic perozonation treatment unit achieves a fluconazole removal rate of over 90%. (5) such as Figure 5 As shown, the electrocatalytic perozonation treatment unit has a good treatment effect on high-salinity wastewater. For high-salinity wastewater with an initial COD of 130~300 mg / L, the COD removal rate reaches 50% after treatment.

[0013] Example 4: Engineering application of an array-type electrocatalytic perozonation water treatment device with enhanced mass transfer via a ring electric field.

[0014] (1) Process flow: Taking the deep treatment of high-salt and recalcitrant organic wastewater after biochemical treatment in a wastewater treatment plant in an industrial park as an example, the complete process flow is as follows: comprehensive wastewater of the park → bar screen → grit chamber → primary sedimentation tank → biochemical tank (A / O process) → secondary sedimentation tank → array-type electrocatalytic perozonation water treatment device with enhanced mass transfer by annular electric field → disinfection tank → discharge or reuse in compliance with standards. This device, as a deep treatment unit, is installed after the secondary sedimentation tank and is specifically used to remove residual COD, color and toxicity from the biochemical effluent to ensure that the effluent stably meets the discharge standards; (2) Device operation: such as Figure 6As shown, to meet the needs of large-scale water treatment, the reaction units of this invention can be connected in series and parallel arrays. The specific operation is as follows: the effluent from the secondary sedimentation tank is pumped by the water pump 6 and enters the array-type electrocatalytic perozonation water treatment device 9, which enhances mass transfer through the annular electric field, through the inlet valve 7 and the inlet 8. Inside this device, multiple reaction units can be flexibly configured in series or parallel according to the actual water quality and quantity conditions. The treated effluent then enters the subsequent disinfection tank 14. Series operation connects multiple reaction units in sequence to form a continuous oxidation treatment chain. By extending the total hydraulic retention time of the system, the stepwise degradation and complete removal of pollutants are achieved. Parallel operation is suitable for water quality with large flow rates or low loads. The treatment scale is expanded by arranging the reaction units in parallel.

[0015] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that several modifications and improvements can be made without departing from the principle of the present invention, and these all fall within the protection scope of this application.

Claims

1. An array-type electrocatalytic perozonation water treatment device and application method based on enhanced mass transfer using a ring electric field, characterized in that, A ring cathode is constructed using a carbon felt supported on an iron-based nitrogen-coordinated porous carbon active layer. This ring cathode, together with a centrally located microporous aerated titanium anode, forms a coaxial ring electric field structure. The active layer of the cathode ① catalytically decomposes ozone introduced from the anode, and ② in-situ reduces ozone to hydrogen peroxide, resulting in a perozonation reaction. This process synergistically generates hydroxyl radicals, creating a composite oxidation system on the surface of the ring cathode and within the reactor space. This system enables the oxidation of recalcitrant organic matter in high-salt wastewater and can adapt to water treatment requirements under varying recalcitrant organic matter loads. The specific methods for preparing the ring cathode, constructing the reactor, and applying the system are as follows: (1) Using MIL-88B (Fe) as a precursor, pyrolyze it under high-purity argon at 730~770℃ for 2.5~3.5 h to obtain a black iron oxide powder. Weigh 0.20~0.22 g of the powder and disperse it in 150~180 mL of nitric acid solution with a concentration of 2.0~2.2 mol / L. Stir the reaction in a water bath at 75~85℃ for 8~12 h. After the reaction, wash it three times with ultrapure water and dry it at 75~85℃ to obtain iron-nitrogen-carbon powder, denoted as Fe-NC. (2) Physicochemical characteristics of Fe-NC: It exhibits a highly graphitized structure. The intensity ratio of the defect peak to the graphite peak in the Raman spectrum is 0.8~0.

9. Iron is anchored in the carbon matrix in an atomically dispersed form. Its active sites have an unsaturated coordination environment composed of nitrogen atoms and carbon atoms. Iron atoms form an unsaturated four-coordinate structure by coordinating with three oxygen atoms and one nitrogen atom. The H2O2 selectivity is 35~40%, and the number of transferred electrons is 3.2~3.

3. (3) Pretreatment of the annular cathode substrate: The carbon felt (5×20 cm) is placed in 100~150 mL of acetone, anhydrous ethanol and ultrapure water for ultrasonic cleaning for 30~60 min to remove surface impurities, and then dried at 75~85℃. (4) Preparation of active layer slurry: Weigh 0.3~0.4 g of carbon black and 0.075~0.085 g of Fe-NC prepared in step (1), add 1.0~1.2 mL of 60 wt% polytetrafluoroethylene emulsion, 150.0~180.0 mL of ultrapure water and 2.4~3.0 mL of isopropanol, and ultrasonically mix them evenly under ice-water bath conditions; (5) Loading and molding of Fe-NC annular cathode: The pretreated carbon felt is immersed in the active layer slurry, and after ultrasonic treatment to ensure that the catalyst is fully penetrated, it is fixed on the annular mold, dried and shaped at 75~85℃, and then calcined in nitrogen at 350~370℃ for 25~35 min at 5~8℃ / min. After cooling, Fe-NC annular cathode is obtained. (6) The aeration anode is a microporous aeration titanium (stainless steel) anode, which is cylindrical in shape and the surface active coating is ruthenium-iridium titanium coating, iridium-tantalum titanium coating, platinum-based coating and other highly active and stable coatings. (7) The electrocatalytic perozonation reaction module adopts a concentric circle configuration, with the annular cathode coaxially surrounding the outside of the central microporous aeration anode, and the anode and cathode connected to the positive and negative terminals of an external DC power supply respectively through wires; (8) Operating conditions: The reaction module operates within the following optimized parameter range: operating current is 1.0~2.5 A, reaction gas flow rate is 50~200 mL / min, and total dissolved solids are 7000~12000 mg / L; (9) Operating modes: By switching the gas source (O2 / O3) and the circuit on / off, four operating modes can be flexibly realized: electrolysis, electro-Fenton, catalytic ozone oxidation and electro-catalytic perozonation, to adapt to different treatment needs; (10) The array-type electrocatalytic perozonation water treatment device adopts an array arrangement and is composed of multiple reaction units. Each unit can operate independently or be flexibly connected in series and in parallel through built-in flow channels. The device is functionally adjustable. For high-concentration recalcitrant organic matter (COD about 300~18000 mg / L), multiple modules are connected in series to construct a step-by-step treatment, which serves as a pretreatment unit to improve the chemical structure of organic matter and enhance the biodegradability of wastewater. For large flow and low pollution load (COD about 130~300 mg / L), multiple modules can be connected in parallel to achieve mineralization of recalcitrant organic matter and ensure that the COD of the effluent meets the standard stably.

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