Photocatalytic reactor, reaction system for continuously and deeply treating wastewater, and application thereof

Abstract

The present application discloses a photoelectrocatalytic reactor, a reaction system for continuously and deeply treating wastewater and an application thereof, which includes an anode current collector tank, a photoanode unit, an insulating unit, a cathode and a cathode current collector. A light-transmitting window is provided at the bottom of the anode current collector tank, and a water inlet is provided at the bottom of the anode current collector; a water outlet is provided on the cathode current collector. The insulating unit is embedded in the anode current collector tank, and the cathode current collector is embedded in the insulating unit. A liquid flow channel is formed between the anode current collector tank, the insulating unit and the cathode current collector. Through the design of the embedded structure, it is easy to assemble and can avoid wastewater leakage at the same time; the light-transmitting window is arranged below the reactor. While the light source is fully close to the photoanode unit, it is ensured that the photoanode unit is fully immersed in the reaction solution. The oxygen generated by the photoanode unit during the wastewater treatment process can realize redox through the cathode to generate superoxide radicals, improving the treatment ability of fluorinated aromatic wastewater.

Description

Technical Field

[0001] The present application relates to a photoelectrocatalytic reactor, a reaction system for continuous deep treatment of wastewater and its application, and belongs to the technical field of sewage treatment. Background Art

[0002] Fluorine, with its small atomic radius and high electronegativity, exhibits strong electronic, barrier, hydrophobic, and lipid-soluble permeability effects. Its introduction into organic molecules can significantly alter specific physical and chemical properties, such as hydrophobicity, thermodynamic stability, acidity, and lipophilicity. Consequently, it is widely used in the pharmaceutical, pesticide, and chemical industries. Fluoroaromatic hydrocarbon derivatives are important pharmaceutical and pesticide intermediates, such as those used in the synthesis of the antidepressant fluoxetine and cephalosporin antibiotics. However, fluorine's extremely strong electronegativity and high carbon-fluorine bond energy make fluoroaromatic compounds stable in environmental media. They are persistent environmental pollutants that accumulate in organisms and enter the human body through the food chain, disrupting the body's normal metabolism of calcium and phosphorus and inhibiting the activity of certain enzymes, thereby affecting human health. The advanced treatment of fluoroaromatic wastewater has always been a challenge, which is of great significance to the sustainable development of pharmaceutical wastewater treatment and pharmaceutical technology.

[0003] At present, the main methods for treating fluoroaromatic wastewater include biological methods, catalytic wet oxidation, and the Fenton method. The operating cost of biological treatment methods is relatively low. Since there are almost no natural fluorine-containing compounds in nature, the cultivation and screening of strains for fluoride treatment are greatly limited. In addition, biological treatment methods will form incompletely degraded fluorine-containing intermediates during the treatment of fluoroaromatic molecules, which have potential environmental toxicity. Catalytic wet oxidation mainly catalyzes the breaking of chemical bonds of fluoroaromatic molecules under high temperature and high pressure environments. It is non-selective and highly active. However, catalytic wet oxidation is limited by thermodynamic constraints and requires the wastewater to be heated to 100 degrees Celsius or above. It consumes a lot of energy and has great safety risks. The cost of treating relatively low-concentration fluoroaromatic wastewater is high. The Fenton process mainly uses Fenton reagents such as iron and copper to catalyze the decomposition of chemical reagents such as hydrogen peroxide or persulfate to produce free radicals with strong oxidizing ability such as hydroxyl radicals and sulfate radicals to participate in the oxidation process of fluoroaromatic hydrocarbon molecules. It is a non-selective deep treatment method at room temperature and pressure. However, the traditional Fenton process is limited by conditions such as the difficulty in activating peroxide compound reagents and the limited circulation of Fenton reagents, as well as problems such as a narrow pH range of application and secondary contamination of iron sludge.

[0004] Photoelectrocatalysis is an advanced oxidation technology that has developed rapidly in recent years. It integrates the advantages of photocatalysis and electrocatalysis. Mainly, under light illumination, electron-hole pairs are generated in the semiconductor. Under the condition of an applied bias voltage, electrons and holes migrate to the cathode and anode surfaces respectively to participate in chemical reactions, mainly including the direct oxidative defluorination of fluoroaromatic molecules on the anode surface, reductive hydrodefluorination on the cathode surface, water oxidation to generate high-energy hydroxyl radicals, oxygen reduction to generate superoxide radicals, etc. Under the combined action of multiple paths and multiple species, the fluoroaromatic wastewater is deeply treated, including rapid and efficient defluorination to improve the biodegradability of the fluoroaromatic wastewater and deep and efficient mineralization to achieve the safe discharge of the fluoroaromatic wastewater.

[0005] The photoelectrocatalytic method that combines photocatalysis and electrocatalysis not only overcomes the problems of easy recombination of electron-hole pairs in nanoparticles and difficult recovery of nanoparticle catalysts in the photocatalytic process, but also expands the problems such as limitations of traditional electrocatalytic materials and inactivation of catalytic sites on the electrode surface. At the same time, in this process, active species such as hydroxyl radicals and superoxide radicals are in-situ generated through water oxidation and oxygen reduction, overcoming the related problems such as continuous input of chemical reagents and difficult activation, and limited recycling of Fenton reagents in the traditional Fenton process. It is a strengthened fluoroaromatic wastewater treatment technology with good application prospects.

[0006] For the photoelectrocatalytic treatment process of fluoroaromatic wastewater, it is necessary to develop a suitable photoelectrocatalytic reactor to achieve mobile-phase and large-scale treatment. Photoelectrocatalysis is troubled by problems such as large-scale synthesis technology of electrodes, resistance loss of conductive substrates, resistance loss of electrolytes, and mass transfer limitation during the amplification process. A key to solving these problems is the design of the photoreactor. Traditional photoelectrocatalytic reactors mainly include internally illuminated cylindrical reactors, side-illuminated flat reactors, filtration reactors, etc. The internally illuminated cylindrical reactor mainly uses short-wavelength ultraviolet lamps as the light source, and a cylindrical reactor is combined with a mesh electrode to achieve photoelectrocatalysis. This reactor improves solution mass transfer and can achieve large-area electrode assembly. However, the short-wavelength ultraviolet lamp scatters severely in the solution, limiting the utilization of light energy; the area of the mesh electrode is enlarged, but the problems such as its current loss are not solved, limiting the performance and large-scale application of photoelectrocatalysis. The side-illuminated flat reactor mainly uses industrial LEDs, etc. as the light source, and the reactor is connected by fasteners. This reactor can conveniently adjust the distance between the photoelectrode and the light source, and has a small footprint and can achieve integrated scale. However, through the fastener connection method, due to the action of gravity, the solution is prone to leakage, limiting its application in the mobile-phase treatment process; at the same time, the problem of current loss of the photoelectrode during the amplification process is not solved. The filtration reactor mainly designs through a porous carrier, and the residence time of pollutant molecules in the carrier is extended, thereby improving its deep catalytic treatment effect. However, the porous carrier design limits the light absorption performance of the catalyst, reduces the utilization efficiency of the catalyst, and at the same time, the filtration reactor needs to be equipped with a suction filtration device to provide osmotic pressure, with a high cost and it is difficult to achieve large-scale treatment. Summary of the Invention

[0007] In view of the characteristics of the difficult degradation of fluorinated aromatic wastewater, a new type of photoelectrocatalytic reactor is developed by combining photoelectrocatalytic technology with the advantages of photocatalysis and electrocatalysis, forming a photoelectrocatalytic method for the continuous flow and deep treatment of fluorinated aromatic wastewater on a large scale. Its principle is that under light irradiation, the photoanode can generate high-energy photogenerated holes and a large number of hydroxyl radicals. The high-energy holes are used for direct oxidation and the hydroxyl radicals for electrophilic substitution reactions to achieve rapid defluorination and deep mineralization of fluorinated aromatic pollutants. At the same time, the photogenerated electrons migrate to the cathode under the action of the electric field to realize the hydrodefluorination reaction of fluorinated aromatic hydrocarbons or the reaction of oxygen reduction to generate superoxide radicals, which, together with the oxidation process at the anode, improve the treatment efficiency of fluorinated aromatic wastewater. The design of the embedded photoelectrocatalytic reactor solves the problem of solution leakage during the treatment of the mobile phase, the design of the current collector inside the reactor reduces the resistance loss during the amplification of the photoanode, the design of the internal flow field improves the electrolyte resistance loss and mass transfer limitation problems during the catalytic degradation process, and the all-metal bottom-illumination design is conducive to the connection of multiple reactors, thus having the ability to be treated on a large scale.

[0008] According to one aspect of the present application, a photoelectrocatalytic reactor is provided, including an anode current collector tank, a photoanode unit, an insulating unit, a cathode, and a cathode current collector;

[0009] The insulating unit is embedded in the anode current collector tank, the cathode current collector is embedded in the insulating unit, and a liquid flow channel is formed between the anode current collector tank, the insulating unit, and the cathode current collector;

[0010] The photoanode unit is fixed on the anode current collector tank;

[0011] The cathode is fixed on the cathode current collector;

[0012] A light-transmitting window is provided at the bottom of the anode current collector tank, and a water inlet is provided at the bottom of the anode current collector;

[0013] A water outlet is provided on the cathode current collector;

[0014] The photoanode unit is located above the light-transmitting window;

[0015] Both the photoanode unit and the cathode have a hole structure;

[0016] Both the anode current collector tank and the cathode current collector are made of conductive metal materials.

[0017] The photocatalytic reactor provided by this application is provided with a light-transmitting window at the bottom. Through the bottom-illumination design, the distance between the photoanode and the light source is controlled to reduce light loss. By using conductive metal materials for both the anode current collector tank and the cathode current collector, multi-point contact between the photoanode unit and the anode current collector tank can be achieved, with uniform electric field distribution, reducing charge dissipation. At the same time, taking advantage of the characteristics of the all-metal multi-point contact of the photocatalytic reactor and combining the parallel assembly of small-area photoanodes, equivalent area replacement is realized, reducing the performance loss caused by geometric dimensions. By using the installation mode where the photoanode unit and the cathode are parallel and opposite to each other, a uniform electrolyte electric field is formed, reducing the electrolyte resistance.

[0018] By setting the water inlet at the bottom of the anode current collector tank and the water outlet on the cathode current collector tank, a flow pattern where wastewater flows in from the bottom and out from the top can be achieved, enabling the wastewater to flow vertically through the photoanode and the cathode, enhancing mass transfer. Through the flow field design, reaction dead zones are reduced, and the degradation performance is improved.

[0019] Optionally, a first support framework is provided at the bottom of the anode current collector tank, and the photoanode unit is press-fitted on the first support framework through the insulating unit. The first support framework is a platform that protrudes inward from the inner side of the anode current collector tank, supporting the photoanode unit while conducting the photo-generated electrons and holes of the photoanode, reducing the resistance loss of the photoanode.

[0020] Optionally, the photoanode unit includes one photoanode or multiple photoanodes in parallel, and the photoanode unit is fixed at the bottom of the anode current collector tank.

[0021] Optionally, a fluororubber ring is provided between the anode current collector tank and the insulating unit, which is used for the close contact between the anode current collector tank and the insulating unit, and at the same time prevents wastewater leakage.

[0022] Optionally, a second support framework is provided at the bottom of the insulating unit, and the cathode is press-fitted on the second support framework through the cathode current collector. The second support framework of the insulating unit isolates the photoanode unit and the cathode, and at the same time plays a supporting role for the photoanode unit and the cathode.

[0023] Optionally, a fluororubber ring is provided between the insulating unit and the cathode current collector, which is used for the close contact between the insulating unit and the cathode current collector, preventing wastewater leakage.

[0024] Optionally, the photoanode unit is selected from at least one of titanium dioxide, tungsten oxide, and iron oxide.

[0025] Optionally, the cathode is selected from at least one of metal titanium, metal nickel, metal tungsten, metal copper, nickel oxide, copper oxide, and carbon materials.

[0026] The photoanode of the present invention is synthesized by methods such as hydrothermal synthesis, sol-gel method, thermal spraying, heat treatment, etc., controlling the quasi-in-situ or in-situ synthesis process to synthesize a semiconductor photoanode with a special morphology of nanocrystal arrays, so as to enable it to have a high charge separation efficiency and surface catalytic efficiency.

[0027] Optionally, the material of the insulating unit is selected from one of polytetrafluoroethylene, polypropylene, and polyether ether ketone.

[0028] Optionally, the conductive metal material is selected from one of metallic titanium, metallic nickel, and stainless steel.

[0029] Optionally, the light-transmitting window is selected from at least one of a quartz sheet, a high-transmission glass, and a magnesium fluoride lens.

[0030] Optionally, a sealing gasket is provided above the photoelectrocatalytic reactor, a metal pressing plate is provided above the sealing gasket, and the metal pressing plate is fixedly connected to the anode current collector tank through bolts. The sealing gasket is used to seal the top of the photoelectrocatalytic reactor. At the same time, the sealing gasket is made of an insulating material. A metal pressing plate is provided above the sealing gasket, and the metal pressing plate is fixedly connected to the anode current collector tank through bolts, which facilitates the connection between the positive pole of the power supply and the anode and also facilitates the series assembly of multiple reactors.

[0031] According to another aspect of the present application, a reaction system for continuous deep treatment of wastewater is provided, including a control terminal, a reactor group, a DC power supply, an LED light source, a power unit, a wastewater storage tank, and an on-line detection device;

[0032] The reactor group, the power unit, the wastewater storage tank, and the on-line detection device are sequentially connected through pipelines;

[0033] The DC power supply is connected to the reactor group,

[0034] The control terminal is connected to the DC power supply and the LED light source;

[0035] The reactor group includes N photoelectrocatalytic reactors connected in series in sequence.

[0036] The above reaction system for continuous deep treatment of wastewater can evolve wastewater by connecting multiple systems in series, not limited to the reaction system connected by the above set of devices.

[0037] Optionally, N is an integer from 4 to 10.

[0038] Due to the miniaturization of the volume of the photoelectrocatalytic reactor provided in the present application, and at the same time, the bottom-illuminated and bottom-flow design prevents wastewater leakage. Through the all-metal design, it is convenient to assemble multiple reactors to form a reactor group, and the number of reactors can be designed according to different needs.

[0039] Optionally, the power unit is a peristaltic pump, which is respectively arranged on the pipeline before the water inlet and the pipeline after the water outlet, so that the reaction system can continuously treat the wastewater.

[0040] Optionally, the illumination wavelength of the LED light source is 365 - 405 nm.

[0041] Optionally, the LED light source uses ultraviolet lamps with illumination wavelengths of 365 nm, 395 nm, and 405 nm, which have low cost and long service life.

[0042] According to another aspect of the present application, a method for continuously and deeply treating fluorinated aromatic wastewater is provided, which uses the above-mentioned reaction system for continuously and deeply treating wastewater;

[0043] It includes the following steps:

[0044] S1: Control the DC power supply and the LED light source to start through the control terminal;

[0045] S2: Start the power unit to make the wastewater continuously enter the reactor group for treatment through the pipeline, and detect the concentration of the treated wastewater through the on-line detection device.

[0046] Optionally, in step S2, if the wastewater concentration ≤ 0.5 ppm, it is safely discharged;

[0047] If the wastewater concentration > 0.5 ppm, it needs to be repeatedly treated.

[0048] The present application deeply and continuously treats fluorinated aromatic wastewater through photoelectrocatalytic action. Under the condition of light irradiation, the photoanode unit can generate high-energy photo-generated holes and a large number of hydroxyl radicals. The rapid defluorination and deep mineralization of fluorinated aromatic pollutants are realized by directly oxidizing with high-energy holes and electrophilic substitution reaction of hydroxyl radicals; at the same time, the photo-generated electrons migrate to the cathode under the action of the electric field to realize the hydrodefluorination reaction of fluorinated aromatic hydrocarbons or the reaction of generating superoxide radicals by redox, and together with the oxidation process at the anode, the treatment efficiency of fluorinated aromatic wastewater is improved.

[0049] The photoanode unit and the cathode are placed in an embedded photoelectrocatalytic reactor, and the light source is provided by an LED ultraviolet lamp, and the electric field is provided by a DC power supply; the reactor is equipped with liquid inlet and outlet ports, and the solution flow is provided by a peristaltic pump or a circulation pump; multiple reactors can be electrically connected in parallel or in series through wires to realize the large-scale continuous flow and deep treatment of fluorinated aromatic wastewater.

[0050] The beneficial effects that the present application can produce include:

[0051] 1) The photocatalytic reactor provided by this application, through an embedded structure design, is easy to assemble and can avoid wastewater leakage. The light-transmitting window is set below the reactor. While the light source is fully close to the photoanode unit, it ensures that the photoanode unit is fully immersed in the reaction solution. The oxygen generated by the photoanode unit during the wastewater treatment process can be used by the cathode to achieve oxidation-reduction to generate superoxide radicals, improving the treatment ability for fluoroaromatic wastewater;

[0052] 2) The photocatalytic reactor provided by this application, the photoanode prepared by in-situ or quasi-in-situ methods has good mechanical stability and catalytic stability, and can continuously generate high-energy photo-generated electron-hole pairs, hydroxyl radicals and superoxide radicals for a long time and without interruption under the condition of flowing scouring, so as to realize the continuous treatment of fluoroaromatic wastewater;

[0053] 3) The photocatalytic reactor provided by this application, both the anode current collector tank and the cathode current collector are made of conductive metal materials. The good conductivity of the metal can be used as a current collector to reduce the resistance loss during the process of assembling the photoanode method. The embedded structure can realize the modular connection of the reactor, the combination of various operating conditions and continuous fluidity treatment, so as to have the potential for large-scale methods;

[0054] 4) The photocatalytic reactor provided by this application can improve the biodegradability of fluoroaromatic wastewater, and the effluent of this reactor can also be further treated by biochemical methods;

[0055] 5) The reaction system for continuous deep treatment of wastewater provided by this application utilizes the photo-electro synergistic effect, combines the advantages of photocatalysis and electrocatalysis, constructs a method for large-scale continuous flow deep treatment of fluoroaromatic wastewater, uses a metal oxide photoanode synthesized by in-situ or quasi-in-situ methods on a porous substrate, and can in-situ generate high-energy photo-generated electron-hole pairs, hydroxyl radicals and superoxide radicals under the irradiation of an LED ultraviolet lamp and act together on the degradation of fluoroaromatic pollutants to achieve deep treatment, improve the biodegradability of wastewater, and has the prospect of industrial application. The embedded reactor design can realize the assembly amplification of the photoanode unit and the fluidity treatment of wastewater. The current collector and flow field design reduce the performance loss during the amplification process of the photoanode unit and improve the mass transfer process of the degradation reaction. The modular connection of multiple reactors can realize the coupling of various photoanodes and operating conditions, realize large-scale deep treatment of fluoroaromatic wastewater, and combine with traditional coagulation precipitation method and bipolar membrane electrodialysis method to deeply treat the fluoride ions and inorganic salts generated after the degradation of fluoroaromatic. Description of the Drawings

[0056] Figure 1 is the schematic diagram of the photocatalytic degradation of fluoroaromatic reaction principle of this application;

[0057] Figure 2 is the schematic diagram of the structure of the photocatalytic reactor in Example 1 of this application;

[0058] Figure 3 Schematic assembly diagram of the photoelectrocatalytic reactor of Embodiment 1 of the present application;

[0059] Figure 4 Cross-sectional view of the photoelectrocatalytic reactor of Embodiment 1 of the present application;

[0060] Figure 5 Cross-sectional view after assembly of the anode current collector tank and the photoanode of the present application;

[0061] Figure 6 Cross-sectional view of the insulation unit of the present application;

[0062] Figure 7 Cross-sectional view after assembly of the insulation unit and the cathode of the present application;

[0063] Figure 8 Scanning electron micrograph of the metal titanium-based titanium dioxide photoanode of the present application;

[0064] Figure 9 Schematic diagram of the reaction system for continuous deep treatment of wastewater of the present application;

[0065] Figure 10 Current-voltage curves of metal titanium-based titanium dioxide photoanodes with different areas;

[0066] Figure 11 Current-voltage curves of parallel-connected metal titanium-based titanium dioxide photoanodes with different areas, where the curve in Figure (a) is for four 12.5 cm 2 parallel-connected photoanodes, and the curve in Figure (b) is for a single 50 cm 2 photoanode;

[0067] Figure 12 Current-voltage curve of the parallel connection of two 50 cm 2 metal titanium-based titanium dioxide photoanode reactors;

[0068] Figure 13 Degradation, defluorination, and TOC removal results of the degradation of 500 mL of fluorophenol solution by the parallel connection of two 50 cm 2 metal titanium dioxide photoanode reactors;

[0069] List of components and reference numerals:

[0070] 1. Anode current collector tank; 2. Photoanode unit; 3. Insulation unit; 4. Cathode; 5. Cathode current collector; 6. Sealing gasket; 7. Metal pressing plate; 1-1. Transparent window; 1-2. Water inlet; 1-3. First support frame; 3-1. Second support frame; 5-1. Water outlet. Detailed implementation manners

[0071] The present application will be described in detail below in conjunction with embodiments, but the present application is not limited to these embodiments.

[0072] The photoelectrocatalytic reactor provided by the present application utilizes the advantages of photocatalysis and electrocatalysis technologies to perform photoelectrocatalysis on fluorinated aromatic wastewater. The principle is as Figure 1 shown. Under light irradiation, the photoanode unit can generate high-energy photogenerated holes and a large number of hydroxyl radicals. The rapid defluorination and deep mineralization of fluorinated aromatic pollutants are achieved by directly oxidizing with high-energy holes and electrophilic substitution reactions of hydroxyl radicals. At the same time, the photogenerated electrons migrate to the cathode under the action of an electric field to realize the hydrodefluorination reaction of fluorinated aromatic hydrocarbons or the reaction of oxygen reduction to generate superoxide radicals, which, together with the oxidation process at the anode, improve the treatment efficiency of fluorinated aromatic wastewater.

[0073] According to an embodiment of the present application, a photoelectrocatalytic reactor is provided, including an anode current collector tank 1, a photoanode unit 2, an insulating unit 3, a cathode 4, and a cathode current collector 5;

[0074] A light-transmitting window 1-1 is provided at the bottom of the anode current collector tank 1, and a water inlet 1-2 is provided at the bottom of the anode current collector tank 1;

[0075] A water outlet 5-1 is provided on the cathode current collector 5; the insulating unit 3 is embedded in the anode current collector tank 1, the cathode current collector 5 is embedded in the insulating unit 3, and a liquid flow channel is formed between the anode current collector tank 1, the insulating unit 3, and the cathode current collector 5;

[0076] The photoanode unit 2 is fixed on the anode current collector tank 1;

[0077] The cathode 4 is fixed on the cathode current collector 5;

[0078] The photoanode unit 2 is located above the light-transmitting window 1-1;

[0079] Both the photoanode unit 2 and the cathode 4 have a porous structure;

[0080] Both the anode current collector tank 1 and the cathode current collector 5 are made of conductive metal materials;

[0081] Among them, the conductive metal material is selected from one of titanium metal, nickel metal, and stainless steel. In this embodiment, the conductive metal material is selected as titanium metal;

[0082] The photoanode unit is selected from at least one of titanium dioxide, tungsten oxide, and iron oxide. In this embodiment, the photoanode is a titanium-based titanium dioxide photoanode;

[0083] The photoanode unit includes one photoanode or multiple photoanodes connected in parallel. In the present application, the number of photoanodes is 1 to 4;

[0084] The preparation method of the photoanode in this application is as follows: Using the hydrothermal synthesis method, dissolve disodium ethylenediaminetetraacetate in secondary water, gradually adjust the pH with hydrochloric acid and stir, then transfer it to a hydrothermal reactor, add a metal titanium mesh, heat it in an oven, take it out after cooling, wash it multiple times and dry it in an oven. Among them, the concentration of disodium ethylenediaminetetraacetate is 75 mM, the concentration of the hydrochloric acid solution is 6 M, and the size of the metal titanium mesh is 240 cm 2 , the hydrothermal temperature is 200 °C, the hydrothermal time is 12 h, the drying temperature is 60 °C, and the drying time is 1 h. The synthesized titanium dioxide photoanode has a regular morphology and exposed crystal planes, exposing {110} and {101} crystal planes respectively. The morphology of the photoanode is as Figure 8 shown. The injection efficiency of this photoanode can reach up to 95% under the irradiation of a 365 nm LED ultraviolet lamp at 1 V vs. RHE.

[0085] The cathode is selected from at least one of metal titanium, metal nickel, metal tungsten, metal copper, nickel oxide, copper oxide, and carbon materials. In this embodiment, the cathode is selected as metal titanium;

[0086] The material of the insulating unit is selected from one of polytetrafluoroethylene, polypropylene, and polyetheretherketone. In this embodiment, the insulating unit is selected as polytetrafluoroethylene;

[0087] The light-transmitting window is selected from one of a quartz sheet, a high-transmission glass, and a magnesium fluoride lens. In this embodiment, the light-transmitting window is selected as a quartz sheet.

[0088] As Figure 5 shown, a first support skeleton 1-3 is provided at the bottom of the anode current collector 1. The photoanode unit 2 is press-fitted on the first support skeleton 1-3 through the insulating unit 3. The photoelectrocatalytic reactor further includes a plurality of photoanodes connected in parallel and fixed at the bottom of the anode current collector groove 1. The parallel connection method is to lay 1 to 4 photoanodes flat on the first support skeleton 1-3 and press them onto the first support skeleton 1-3 on the anode current collector groove 1 through the insulating unit 3. A fluororubber ring is provided between the anode current collector groove 1 and the insulating unit 3.

[0089] As Figure 6 , Figure 7 shown, a second support skeleton 3-1 is provided at the bottom of the insulating unit 3. The cathode 4 is press-fitted on the second support skeleton 3-1 through the cathode current collector 5. A fluororubber ring is provided between the insulating unit 3 and the cathode current collector 5.

[0090] A sealing gasket 6 is provided above the photoelectrocatalytic reactor, and a metal pressing plate 7 is provided above the sealing gasket 6. The metal pressing plate 7 is fixedly connected to the anode current collector groove 1 through bolts.

[0091] Example 1

[0092] A photoelectrocatalytic reactor, as Figure 2 , Figure 3 shown, includes an anode current collector tank 1, an insulating unit 3 and a cathode current collector 5. The insulating unit 3 is embedded in the anode current collector tank 1, and the cathode current collector 5 is embedded in the insulating unit 3. The metal titanium anode current collector tank 1 is a square shell with an open top, and a light-transmitting window 1-1 is provided on the bottom surface corresponding to the top. The light-transmitting window 1-1 is made of a quartz sheet and is hermetically connected to the anode current collector tank 1. A first support skeleton 1-3 protruding inward is provided inside the anode current collector tank 1. A water inlet 1-2 is provided on one side of the anode current collector tank 1. The water inlet 1-2 penetrates through the first support skeleton 1-3 and leads to the cavity inside the anode current collector tank 1. The titanium dioxide photoanode unit 2 is pressed on the first support skeleton 1-3 through the polytetrafluoroethylene insulating unit 3 and is sealed by a fluororubber ring. A second support skeleton 3-1 protruding inward is provided on the inner side of the bottom of the polytetrafluoroethylene insulating unit 3. The metal titanium cathode is pressed on the second support skeleton 3-1 through the metal titanium cathode current collector 5 and is sealed by a fluororubber ring. The metal titanium cathode current collector 5 serves as a shell cover to seal the cavity inside the anode current collector tank 1. A water outlet 5-1 is provided on the top of the metal titanium cathode current collector 5. A sealing gasket 6 is provided above the photoelectrochemical reactor, and a metal pressing plate 7 is provided above the sealing gasket 6. The metal pressing plate 7 is connected to the anode current collector tank 1 by bolts. Wastewater enters the cavity from the water inlet 1-2, passes through the photoanode 2, the insulating unit 3, and the cathode 4 in sequence, and flows out from the water outlet 5-1.

[0093] 1. Evaluation of the photoelectrocatalytic performance of photoanodes with different areas:

[0094] Taking the titanium dioxide photoanode of the present invention as an example, the photoelectrocatalytic performance of the photoanode was tested. The test conditions were as follows: Titanium dioxide photoanodes with sizes of 12.5 cm 2 ~50 cm 2 were taken, a 50 cm 2 metal titanium mesh was used as the cathode, and they were placed in an embedded photoelectrocatalytic reactor. A 500 mL 0.1 M Na2SO4 solution was used as the electrolyte, and a peristaltic pump was used to achieve fluid flow with a flow rate of 500 ml min -1 . A 200 W 365 nm ultraviolet lamp was used as the light source, and a DC power supply was used for power supply. The test potential was 0~3 V, and the test temperature was 25 °C.

[0095] The linear voltammetry curve is as Figure 10As shown, it can be seen from the figure that the larger the photocurrent density of the photoanode, the stronger its oxidation ability, the higher the concentration of hydroxyl radicals generated, and the higher the degradation performance. Since the photoelectrode is a semiconductor material, when the size is enlarged, the photocurrent per unit area decreases significantly, that is, the photocurrent density decreases significantly, which is an important factor limiting the large-scale application of photoelectrocatalysis. The area of the photoanode is directly enlarged from 12.5 cm 2 to 50 cm 2 , and the photocurrent density decays from 3.84 mA cm -2 to 1.74 mA cm -2 .

[0096] 2. Evaluation of the photocatalytic performance of small-area assembled photoanodes

[0097] Taking the titanium dioxide photoanode described in the present invention as an example, the photocatalytic performance of the photoelectrochemical reactor for assembling small-area photoanodes was tested. The test conditions were as follows: Two 12.5 cm 2 titanium dioxide photoanodes were connected in parallel in an embedded reactor, using a 50 cm 2 metal titanium mesh as the cathode, 500 ml of 0.1 M Na2SO4 solution as the electrolyte, and a peristaltic pump was used to achieve flow with a flow rate of 500 ml min -1 . A 200 W 365 nm ultraviolet lamp was used as the light source, powered by a DC power supply, the test potential was 0 - 3 V, the test temperature was 25 °C, and the photocatalytic performance was compared with that of a 25 cm 2 titanium dioxide photoanode under the same conditions, as shown in Figure 11 (a) of the figure; Four 12.5 cm 2 titanium dioxide photoanodes were connected in parallel in an embedded reactor, and under the same conditions, the photocatalytic performance was compared with that of a 50 cm 2 titanium dioxide photoanode, as shown in Figure 11 (b) of the figure.

[0098] According to Figure 11 (a) and (b) of the figure, it can be seen that when the area of the photoanode is enlarged from 12.5 cm 2 to 25 cm 2 and 50 cm 2 , the current density decays from 3.83 mA cm -2 to 2.33 mA cm -2 and 1.74 mA cm -2 respectively. By assembling small-area photoanodes in parallel, such as connecting two 12.5 cm 2 electrodes in parallel to form a 25 cm 2 electrode or connecting four 12.5 cm 2 electrodes in parallel to form a 50 cm 2 electrode, the current density can be restored to 2.80 mA cm-2 and 2.04 mA cm -2 That is, during the amplification process, through small-area assembly, while enlarging the total size of the photoanode, the photocurrent density can be maintained to a certain extent, facilitating large-scale processing; the small-area photoanode assembly requires a parallel mode, and since the reactor of the present application adopts a full-metal design, multi-point contact and parallel connection can be achieved.

[0099] Example 2

[0100] According to an embodiment of the present application, a reaction system for continuous in-depth treatment of wastewater is provided. As Figure 9 shown, it includes a high-concentration treatment system and a low-concentration treatment system. Both the high-concentration treatment system and the low-concentration treatment system include a control terminal, a reactor group, a DC power supply, an LED light source, a power unit, a wastewater storage tank, and an on-line detection device;

[0101] The reactor group, the power unit, the wastewater storage tank, and the on-line detection device are sequentially connected through pipelines;

[0102] The DC power supply is connected to the reactor group;

[0103] The control terminal is connected to the DC power supply and the LED light source;

[0104] The reactor group includes photo-electrocatalytic reactors connected in series in sequence. In this embodiment, the number of photo-electrocatalytic reactors is 4;

[0105] The power system is a peristaltic pump. Two peristaltic pumps are respectively arranged on the pipeline before the water inlet and the pipeline after the water outlet. The on-line detection device is arranged on the pipeline after the wastewater is treated to detect the treated wastewater. When the on-line detection device of the high-concentration treatment system detects that the concentration is lower than 0.5 ppm, the wastewater enters the low-concentration treatment system. If it is still higher than 0.5 ppm, it will continue to be recycled for treatment;

[0106] When the on-line detection device of the low-concentration treatment system detects that the concentration is lower than 0.5 ppm, the wastewater is safely discharged. If it is still higher than 0.5 ppm, it will continue to be recycled for treatment.

[0107] 3. Evaluation of the Photoelectrocatalytic Performance of Multi-Reactor Connection

[0108] Taking the titanium dioxide photoanode and the embedded photo-electrocatalytic reactor of the present invention as an example, the photoelectrocatalytic performance of multi-reactor connection is tested. The test conditions are as follows: Take two 50 cm 2 titanium dioxide photoanodes and place them in two sets of embedded reactors respectively. With 50 cm 2Titanium mesh is used as the cathode, and two embedded reactors are connected in parallel through wires. A 500 ml 0.1 M Na2SO4 solution is used as the electrolyte and is circulated by a peristaltic pump at a flow rate of 500 ml min -1 , with a 200 W 365 nm ultraviolet lamp as the light source, powered by a DC power supply, the test potential is 0 - 3 V, the test temperature is 25 °C, and it is compared with the performance of a single photoelectrocatalytic reactor under the same conditions.

[0109] The current-voltage curve is as Figure 12 shown. By connecting reactors in parallel, the treatment volume can be increased. For example, when two 50 cm 2 reactors are connected in parallel, as shown in the figure, the total photoanode area formed is 100 cm 2 , and the photocurrent density is similar to that of a single photoanode with a total area of 50 cm 2 . That is, by connecting reactors in parallel, the photocatalytic performance can be maintained while increasing the reaction volume, providing a basis for further scale-up.

[0110] 4. Performance evaluation of photocatalytic degradation of fluoroaromatic wastewater by connecting multiple reactors

[0111] Taking the titanium dioxide photoanode and the embedded photoelectrocatalytic reactor described in the present invention as an example, the performance of photocatalytic degradation of fluoroaromatic wastewater by connecting multiple reactors is tested. The test conditions are as follows: Two 50 cm 2 titanium dioxide photoanodes are respectively placed in two sets of embedded reactors. Using 50 cm 2 titanium mesh as the cathode, two embedded reactors are connected in parallel through wires. A 500 mL 20 ppm p-fluorophenol, 0.1 M Na2SO4 solution is used as the electrolyte and is circulated by a peristaltic pump at a flow rate of 500 ml min -1 , with a 200 W 365 nm ultraviolet lamp as the light source, powered by a DC power supply, tested in the constant potential mode, the cell voltage is 1.5 V, the test temperature is 25 °C, and it is compared with the degradation performance of a single embedded photoelectrocatalytic reactor under the same conditions. The degradation performance is as Figure 13 shown. By connecting reactors in parallel, the treatment volume can be increased. For example, when two reactors with a photoanode area of 50 cm 2 are connected in parallel, the total photoanode area formed is 100 cm 2 . The overall degradation performance of a 500 ml 4-fluorophenol solution by the reactor is significantly improved, which means an increase in the reaction volume. Due to the maintenance of the photoelectric performance, the degradation performance per unit area is similar. That is, by connecting reactors in parallel, the degradation performance of a small area can be maintained to a certain extent, and a larger-scale treatment capacity can be achieved by connecting reactors in parallel.

[0112] The above are only several embodiments of the present application and do not impose any form of limitation on the present application. Although the present application is disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the technical solution of the present application, makes some changes or modifications using the disclosed technical content, which are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A photoelectrocatalytic reactor, characterized in that, It includes an anode current collector tank, a photoanode unit, an insulating unit, a cathode, and a cathode current collector; The insulating unit is embedded in the anode current collector tank, the cathode current collector is embedded in the insulating unit, and a liquid flow channel is formed between the anode current collector tank, the insulating unit, and the cathode current collector; The photoanode unit is fixed on the anode current collector tank; The cathode is fixed on the cathode current collector; A light-transmitting window is provided at the bottom of the anode current collector tank, and a water inlet is provided at the bottom of the anode current collector; A water outlet is provided on the cathode current collector; The photoanode unit is located above the light-transmitting window; Both the photoanode unit and the cathode have a porous structure; Both the anode current collector tank and the cathode current collector are made of conductive metal; The light-transmitting window is selected from at least one of a quartz sheet, a highly transparent glass, and a magnesium fluoride lens.

2. The photocatalytic reactor according to claim 1, wherein A first support framework is provided at the bottom of the anode current collector tank, and the photoanode unit is press-fitted on the first support framework through the insulating unit; The photoanode unit includes one photoanode or multiple photoanodes connected in parallel, and the photoanode unit is fixed at the bottom of the anode current collector tank; A fluororubber ring is provided between the anode current collector tank and the insulating unit.

3. The photocatalytic reactor according to claim 2, wherein A second support framework is provided at the bottom of the insulating unit, and the cathode is press-fitted on the second support framework through the cathode current collector; A fluororubber ring is provided between the insulating unit and the cathode current collector.

4. The photocatalytic reactor according to claim 1, wherein, The photoanode unit is selected from at least one of titanium dioxide, tungsten oxide, and iron oxide; The cathode is selected from at least one of metallic titanium, metallic nickel, metallic tungsten, metallic copper, nickel oxide, copper oxide, and carbon materials; The material of the insulating unit is selected from one of polytetrafluoroethylene, polypropylene, and polyether ether ketone; The conductive metal material is selected from one of metallic titanium, metallic nickel, and stainless steel.

5. The photocatalytic reactor according to claim 2, wherein The preparation method of the photoanode is: a semiconductor photoanode with a nanocrystalline array is synthesized in-situ or quasi-in-situ by hydrothermal synthesis, sol-gel method, thermal spraying, or heat treatment method.

6. The photocatalytic reactor according to claim 1, wherein A sealing gasket is provided above the photoelectrocatalytic reactor, a metal pressing plate is provided above the sealing gasket, and the metal pressing plate is fixedly connected to the anode current collector tank through bolts.

7. A reaction system for continuously and deeply treating wastewater, characterized in that, It includes a control terminal, a reactor group, a DC power supply, an LED light source, a power unit, a wastewater storage tank, and an on-line detection device; The reactor group, the power unit, the wastewater storage tank, and the on-line detection device are sequentially connected through pipelines; The DC power supply is connected to the reactor group, The control terminal is connected to the DC power supply and the LED light source; The reactor group includes N photoelectrocatalytic reactors connected in series in sequence; The photoelectrocatalytic reactor is selected from the photoelectrocatalytic reactor according to any one of claims 1 to 6.

8. The reaction system according to claim 7, wherein N is an integer from 4 to 10; The power unit is a peristaltic pump; The illumination wavelength of the LED light source is 365 - 405 nm.

9. A method for continuously and deeply treating fluorinated aromatic hydrocarbon wastewater, characterized in that, Adopt the reaction system for continuously and deeply treating wastewater according to any one of claims 7 or 8; It includes the following steps: S1: Control the DC power supply and the LED light source to start through the control terminal; S2: Start the power unit to make the wastewater continuously enter the reactor group for treatment through the pipeline, and detect the concentration of the treated wastewater by the on-line detection device.

10. The method for continuously and deeply treating fluorinated aromatic hydrocarbon wastewater according to claim 9, characterized in that, In step S2, if the wastewater concentration ≤ 0.5 ppm, it is safely discharged; if the wastewater concentration > 0.5 ppm, repeated treatment is required.

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