Photoelectric anode materials, photoelectric anodes and their preparation methods and applications in wastewater treatment

Abstract

This invention relates to the field of wastewater treatment technology, specifically disclosing a photoanode material, a photoanode, its preparation method, and its application in wastewater treatment. The photoanode material comprises an FeSe2 array layer and a Bi2O2WO4 layer supported on the FeSe2 array layer. FeSe2 has a narrow band gap, good light absorption performance, and photogenerated charge separation capability, which can sensitize other semiconductors with wider band gaps to form heterojunctions, promoting the improvement of photocurrent density and electron quantum yield, and enhancing the photoelectric conversion efficiency of the catalytic material. Bi2O2WO4 is composed of [Bi2O2]. 2+ Layers and [WO4] 2‑ The vertically alternating layers facilitate the separation of photogenerated electrons and holes, thereby enhancing the catalytic oxidation activity of the electrode. The combination of Bi₂O₂WO₄ and FeSe₂ improves their respective solar photoresponse capabilities and photoelectrocatalytic performance, offering significant advantages in environmental engineering.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a photoelectric anode material, a photoelectric anode, its preparation method, and its application. Background Technology

[0002] Industrial wastewater is characterized by its complex composition, recalcitrant nature, and large fluctuations in quality and quantity. It contains various organic and inorganic pollutants. For example, dyeing and printing wastewater contains large amounts of dyes and auxiliaries (such as sodium sulfide and sodium hydrosulfite). These organic substances have complex compositions and diverse structures, and some are even biotoxic, making them difficult to remove completely using a single treatment method. Electroplating wastewater is rich in heavy metal ions, such as chromium, nickel, cadmium, and copper. These heavy metals are non-biodegradable, persist in the environment for a long time, and easily accumulate in organisms, posing serious threats to ecosystems and human health. Different heavy metals require different treatment processes for effective removal, increasing the complexity of the treatment process.

[0003] Currently, common methods for treating industrial wastewater include physical, chemical, and biological methods, as well as combinations thereof. Physical methods have limited catalyst cycles, while traditional biochemical methods suffer from drawbacks such as large land area requirements, long treatment cycles, and poor treatment efficiency. Photoelectrocatalytic advanced oxidation wastewater treatment technology, under the influence of light or an applied electric field, excites photoelectrocatalyst materials to generate a large number of electrons and holes. These electrons and holes separate and move directionally, accumulating at the anode and cathode to produce a large number of active free radicals. These highly oxidizing free radicals react with pollutants in the water, mineralizing them into carbon dioxide, water, and inorganic salts, thereby achieving water purification. Furthermore, these active free radicals can purify different types of water bodies and enhance the biodegradability of the treated water, thus reducing the difficulty of further treatment.

[0004] However, due to limitations in photoelectrocatalytic nanomaterials and other factors, existing photoelectrocatalytic advanced oxidation wastewater treatment technologies consume high energy and their efficiency in treating complex water qualities remains unsatisfactory. Therefore, there is an urgent need to develop a wastewater treatment material with significantly improved purification efficiency. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a photoelectric anode material, a photoelectric anode, its preparation method, and its application. By combining semiconductor Bi2O2WO4 and an n-type semiconductor FeSe2 array to form a heterojunction, they can be used together as photoelectrocatalytic materials, thereby improving the efficiency of deep treatment of complex water bodies and achieving the rational utilization of energy.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0007] In a first aspect, the present invention provides a photoelectric anode material comprising a FeSe2 array layer and a Bi2O2WO4-containing layer loaded on the FeSe2 array layer.

[0008] Compared to existing technologies, the photoelectroanode material provided by this invention, FeSe2, a photoelectrocatalyst, has a narrow band gap, exhibits excellent light absorption performance and photogenerated charge separation capability, and is a typical power-generating semiconductor (n-type semiconductor). It can sensitize other semiconductors with wider band gaps to form heterojunctions, promoting increased photocurrent density and electron quantum yield, thereby enhancing the photoelectric conversion efficiency of the catalytic material. Bismuth metal semiconductors have low toxicity, high conductivity, and a suitable tunable band gap, possessing excellent photoelectrocatalytic activity and photoelectric conversion efficiency. [Bi2O2] 2+ Layers and salt anions [WO4] 2- In the layered structure of the Aurvillius photocatalyst Bi₂O₂WO₄, [Bi₂O₂] 2+ Layers and anions [WO4] 2- The vertically alternating layers structure is more conducive to promoting the separation of photogenerated electrons and holes, thereby improving the catalytic oxidation reaction activity of the electrode. This invention uses a novel composite of Bi₂O₂WO₄ and FeSe₂ to form a heterojunction, which can improve their respective solar photoresponse capabilities and photoelectrocatalytic performance, showing significant application advantages in environmental engineering and wastewater treatment.

[0009] Preferably, the thickness of the FeSe2 array layer is 3μm to 5μm.

[0010] It should be noted that in this invention, the FeSe2 array layer is arranged as a single-layer FeSe2 array, and the thickness of the FeSe2 array layer is the same as the length of the FeSe2 array.

[0011] Preferably, the thickness of the Bi2O2WO4 layer is 80nm~200nm.

[0012] Preferably, the Bi2O2WO4-containing layer further includes carbon nanofibers.

[0013] Carbon nanofibers possess excellent toughness, mechanical strength, adhesion, and conductivity. They can increase the adhesion between the active materials (FeSe2 array and Bi2O2WO4) in the photoelectrode material and the anode substrate, preventing the active materials from detaching from the anode substrate and improving the stability of the photoelectrode. At the same time, carbon nanofibers have good conductivity and will not reduce the electron transport performance of the photoelectrode, which is beneficial to improving the photoelectrocatalytic activity of the electrode.

[0014] More preferably, the carbon nanofibers have a diameter of 150nm~200nm and a length of 5μm~20μm.

[0015] Preferably, the mass ratio of FeSe2 to Bi2O2WO4 in the photoanode material is 200:(10~50).

[0016] More preferably, the mass ratio of FeSe2, Bi2O2WO4 and carbon nanofibers in the photoelectric anode material is 200:(10~50):(0.8~1.6), and more preferably 200:(20~40):(1~1.4).

[0017] By limiting the thickness of the FeSe2 array layer and the Bi2O2WO4 layer, as well as the amount of FeSe2 and Bi2O2WO4, this invention can better leverage the synergistic effect of the two, achieving both good photoresponse capability and good electrocatalytic performance.

[0018] More preferably, the method for preparing FeSe2 includes the following steps:

[0019] S1-1, Selenium powder is added to a reducing agent solution to carry out a reduction reaction, yielding a divalent selenide solution;

[0020] S1-2, ferrous salt, chelating agent and first dispersant are added to water, mixed with the ferrous selenide solution, and a redox reaction is carried out to obtain FeSe2.

[0021] This invention first reduces selenium powder to divalent selenide, and then reacts it with divalent ferric salt in a redox reaction to obtain FeSe2. A chelating agent is used to coordinate ferrous ions, so that ferrous ions are released slowly. At the same time, a first dispersant is added to prevent the agglomeration of powder, which helps to form uniform nano FeSe2 particles in the subsequent process.

[0022] More preferably, in S1-1, the reducing agent solution comprises 18wt%~22wt% sodium borohydride solution.

[0023] More preferably, in S1-1, the mass ratio of the selenium powder to the reducing agent solution is 1:(2~15), and even more preferably 1:(4~8).

[0024] More preferably, in S1-1, the temperature of the reduction reaction is 20℃~30℃, and the reaction time is 30min~50min.

[0025] More preferably, in S1-2, the divalent ferric salt includes ferrous chloride.

[0026] More preferably, in S1-2, the chelating agent includes N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid.

[0027] More preferably, in S1-2, the first dispersant comprises dodecyltrimethylammonium bromide.

[0028] More preferably, in S1-2, the mass ratio of the divalent iron salt, chelating agent, first dispersant, water and divalent selenide solution is (2~10):(10~30):(0.01~0.05):(20~100):(6~30), and even more preferably (4~8):(15~25):(0.01~0.05):(50~80):(10~25).

[0029] More preferably, in S1-2, the mixing temperature is 50℃~70℃, the mixing rate is 100rpm~200rpm, and the mixing time is 1h~2h.

[0030] More preferably, in S1-2, the temperature of the redox reaction is 180℃~200℃, and the reaction time is 3h~6h.

[0031] The present invention first mixes the components at 50℃~70℃, and then carries out a redox reaction at 180℃~200℃. The gradient heating method is beneficial to the formation of FeSe2 and avoids the formation of impurities such as FeSe and Fe2Se3 by excessive reduction reaction.

[0032] For example, in S1-2, after the redox reaction is completed, the process also includes: cooling to room temperature, solid-liquid separation, washing and drying the solid to obtain FeSe2.

[0033] More preferably, in S1-2, the particle size of FeSe2 is 10nm~180nm.

[0034] More preferably, the preparation method of the Bi2O2WO4 includes the following steps:

[0035] S2-1, tungstate, bismuth salt, second dispersant and pH adjuster are added to water and hydrolyzed under weak acid conditions to obtain a suspension;

[0036] S2-2, the suspension is subjected to a first hydrothermal reaction to obtain Bi2O2WO4.

[0037] In this invention, tungstate and bismuth salt undergo a hydrolysis reaction under weak acid to form a white suspension of Bi(OH)WO4, and a second dispersant reduces the number of agglomerated particles; then, through a first hydrothermal reaction, the layered lattice is continuously replaced and overlapped, and the bismuth salt and Bi(OH)WO4 continue to react, ultimately generating nanoscale Bi2O2WO4.

[0038] More preferably, in S2-1, the tungstate includes sodium tungstate.

[0039] More preferably, in S2-1, the bismuth salt includes bismuth nitrate.

[0040] More preferably, in S2-1, the second dispersant comprises polyethylene glycol.

[0041] More preferably, in S2-1, the pH adjuster comprises a 1.7M~2.3M acetic acid solution and a 1.7M~2.3M ammonium acetate solution; the mass ratio of the acetic acid solution to the ammonium acetate solution is (1.8~2.2):1.

[0042] More preferably, in S2-1, the mass ratio of the tungstate, bismuth salt, second dispersant and water is (2~8):(4~16):(0.5~1):(100~160), and even more preferably (3~7):(8~12):(0.6~0.9):(120~150).

[0043] More preferably, in S2-1, the weak acid condition is pH=5~6.

[0044] More preferably, in S2-1, the temperature of the hydrolysis reaction is 20℃~35℃, and the reaction time is 30min~40min.

[0045] More preferably, in S2-2, the temperature of the first hydrothermal reaction is 160℃~190℃, and the reaction time is 8h~12h.

[0046] For example, in S2-1, after the first hydrothermal reaction is completed, the process also includes: cooling to room temperature, solid-liquid separation, washing and drying the solid to obtain Bi2O2WO4.

[0047] More preferably, in S2-2, the particle size of the Bi2O2WO4 is 10nm~150nm.

[0048] In a second aspect, the present invention provides a photoanode, comprising an anode substrate and the photoanode material loaded on the anode substrate.

[0049] The photoelectric anode provided by the present invention improves the efficiency of deep treatment of complex industrial wastewater by loading photoelectric anode materials (including FeSe2 array layer and Bi2O2WO4 layer) onto the anode substrate.

[0050] Preferably, the anode substrate includes at least one of stainless steel mesh, titanium mesh, copper mesh, aluminum mesh, molybdenum mesh, nickel mesh, stainless steel sheet, foamed nickel, foamed titanium, or foamed aluminum.

[0051] In this invention, the anode substrate is made of metallic material, and the substrate shape is sheet-like, mesh-like, or foam mesh-like. It has a unique porous structure, stable physicochemical properties, and good conductivity, exhibiting stability in different electrolytes. The porous structure not only increases the surface area of ​​the anode but also facilitates the reaction between ions in the electrolyte and the active material on the electrode, improving the activity of the photoelectrocatalytic reaction and thus enhancing the photoelectrocatalytic advanced oxidation wastewater treatment effect.

[0052] Preferably, the anode substrate has a length of 50mm to 100mm, a width of 100mm to 200mm, and a thickness of 2mm to 4mm.

[0053] This invention employs a composite electrode made of non-toxic, inexpensive, and highly resistant to acid and alkali corrosion, consisting of a FeSe2 nano-metal array and a Bi2O2WO4 semiconductor. The electrode material exhibits high adhesion, is not easily detached, and can be removed for cleaning, soaking, regeneration, and reuse, solving the problems of traditional suspended photocatalysts such as difficulty in recycling and easy detachment. This invention utilizes a low-cost anode substrate with a large specific surface area and stable physicochemical properties as the support substrate for the photocatalyst, effectively leveraging the synergistic effect of photocatalysis and saving on wastewater treatment costs.

[0054] Thirdly, the present invention provides a method for preparing the aforementioned photoelectric anode, comprising the following steps:

[0055] Sa, the anode substrate is immersed in a mixture of FeSe2 and water to carry out a second hydrothermal reaction to obtain the primary electrode;

[0056] Sb, the primary electrode is immersed in a mixture of FeSe2, silane coupling agent and cosolvent, and a third hydrothermal reaction is carried out to form a FeSe2 array layer, thus obtaining a FeSe2 array electrode;

[0057] Sc, a mixture of Bi2O2WO4, binder and co-solvent is coated onto the FeSe2 array electrode, and then calcined to form a Bi2O2WO4 layer, thus obtaining a photoanode.

[0058] The method for preparing a photoanode provided by this invention employs a sol-gel method to load and grow photoanode material onto an anode substrate, and then utilizes the annealing properties through calcination to obtain the photoanode. This invention first uses a second hydrothermal reaction to form a primary electrode; then, under the action of a co-solvent, hydrothermal action allows nano-FeSe2 to enter the surface of the primary electrode, continuously nucleating and diffusing, and undergoing adsorption and coupling under the action of a silane coupling agent, depositing to form a FeSe2 array layer, thus obtaining a FeSe2 array electrode; finally, the sol-gel method is again used to coat Bi2O2WO4 onto the surface of the FeSe2 array electrode, and calcination is performed to form a Bi2O2WO4-containing layer, obtaining the photoanode.

[0059] For example, in Sa, before impregnation, the process includes: placing the anode substrate in acetone and water in sequence, sonicating for 10 to 15 minutes respectively, and then drying.

[0060] This invention first pre-treats the anode substrate, which can effectively remove impurities and oil stains on the surface of the anode substrate and increase the adhesion of subsequent photoelectrocatalytic materials to the electrode substrate surface.

[0061] Preferably, in Sa, the mass ratio of FeSe2 to water is (1~4):(80~100).

[0062] Preferably, in Sa, the immersion time is 30 min to 60 min.

[0063] Preferably, in Sa, the temperature of the second hydrothermal reaction is 100℃~120℃, and the reaction time is 25min~40min.

[0064] Under specific second hydrothermal reaction conditions, this invention enables FeSe2 to diffuse uniformly onto the surface of the anode substrate while ensuring that the crystal form of FeSe2 remains unchanged, and at the same time improves the adhesion and bonding force of FeSe2 on the anode substrate.

[0065] Preferably, in Sb, the silane coupling agent includes KH560.

[0066] Preferably, in Sb and Sc, the co-solvent comprises 40wt% to 60wt% of an aqueous solution of povidone.

[0067] Povidone aqueous solution is an ionic liquid, which can increase the solubility of the system, reduce interfacial tension, and facilitate the full progress of the third hydrothermal reaction.

[0068] Preferably, in Sb, the mass ratio of FeSe2, silane coupling agent and cosolvent is (2~5):(1~4):(10~20).

[0069] Preferably, in Sb, the temperature of the third hydrothermal reaction is 80℃~120℃, and the reaction time is 4h~8h.

[0070] It should be noted that the present invention does not limit the amount of photoanode and mixed solution in Sa, as long as the mixed solution can immerse the anode substrate; the present invention also does not limit the amount of primary electrode and mixed solution in Sb, as long as the mixed solution can immerse the primary electrode.

[0071] Preferably, in Sc, the mixture also includes carbon nanofibers.

[0072] Preferably, in Sc, the adhesive comprises polyamide.

[0073] More preferably, in Sc, the polyamide has a molecular weight of 5000~12000 and a particle size of 200 mesh~300 mesh.

[0074] Preferably, in Sc, the mass ratio of Bi2O2WO4, binder and cosolvent is (6~32):(1~8):(10~80), more preferably (10~28):(2~7):(25~65), and even more preferably (15~22):(3~6):(30~50).

[0075] Preferably, in Sc, the coating thickness is 80nm~200nm.

[0076] For example, in Sc, after coating and before calcination, it also includes natural drying for 4 to 10 minutes.

[0077] Preferably, in Sc, the calcination temperature is 160℃~260℃ (more preferably 180℃~240℃), and the calcination time is 60min~120min.

[0078] Under specific calcination conditions, the Bi2O2WO4-containing layer solidifies, and the Bi2O2WO4 lattice gradually diffuses and tends to equilibrium, increasing the adhesion and bonding force of the Bi2O2WO4-containing layer on the FeSe2 array electrode.

[0079] In the example, Sc, calcination also includes: cooling to room temperature.

[0080] Fourthly, the present invention provides the aforementioned photoanode material or the application of the aforementioned photoanode in wastewater treatment.

[0081] Fifthly, the present invention provides a photoelectrocatalytic advanced oxidation wastewater treatment system, comprising the aforementioned photoanode, photocathode, electrolytic cell, power supply, and light source;

[0082] The photoanode and the photocathode are located in the electrolytic cell, and the photoanode and the photocathode are respectively connected to the power source via wires;

[0083] The light source is located outside the electrolytic cell and is used to irradiate the electrolytic cell with light.

[0084] The photoelectrocatalytic advanced oxidation wastewater treatment system provided by this invention combines photocatalysis and electrochemical catalysis technologies to achieve deep treatment of wastewater, improve the removal efficiency of organic pollutants, reduce energy consumption, and provide mild reaction conditions, making it environmentally friendly, easy to operate, and suitable for water bodies with various water quality conditions. In practical applications, it has a more effective purification effect and has high market application value.

[0085] This invention utilizes a photoanode loaded with a FeSe2 array / Bi2O2WO4 heterojunction in an electrolytic cell, improving the deep treatment efficiency of complex water quality. The wastewater treatment reaction conditions are mild, green, and low-carbon, overcoming the drawbacks of traditional advanced oxidation technologies such as high energy consumption and limited catalyst cycles, while significantly shortening the treatment cycle. The photocatalytic system possesses extremely strong redox capabilities under the influence of an external electric field and light radiation. The photoanode loses electrons and generates holes under the excitation of electrical energy and light radiation. These holes exhibit strong oxidizing properties and can react directly with pollutants or react with water molecules to form hydroxyl radicals (·OH) for indirect oxidation. Meanwhile, electrons, under the influence of an external electric field, move directionally to and accumulate at the cathode. These strongly reducing electrons can not only directly catalyze the precipitation of heavy metal ions but also react with water to generate superoxide radicals (·O2). 2- This invention indirectly oxidizes pollutants. Through photocatalytic advanced oxidation technology, it enhances the activity of photocatalytic and electrocatalytic oxidation reactions, and the various components and materials exhibit synergistic effects, achieving advanced wastewater treatment.

[0086] The photoelectrocatalytic advanced oxidation wastewater treatment system provided by this invention can be used to treat wastewater with COD of 600mg / L~10000mg / L, ammonia nitrogen of 15mg / L~300mg / L, and heavy metal ion content of 5mg / L~120mg / L.

[0087] Preferably, the photocathode includes at least one of a graphite electrode, a carbon rod electrode, a graphite fiber felt electrode, or a coated metal electrode.

[0088] More preferably, the photocathode comprises at least one of carbon cloth, carbon fiber felt, titanium sheet, titanium mesh, platinum sheet, or platinum mesh.

[0089] Preferably, the photoanode and the photocathode are of the same size.

[0090] This invention selects corrosion-resistant electrodes with sheet-like or mesh-like structures as photocathodes, which have low overpotentials, high hydrogen evolution potentials, and are less prone to hydrogen gas generation and hydrogen embrittlement. The preferred photocathode of this invention can fully utilize energy, reduce electricity consumption, and has the advantages of low-carbon emission reduction.

[0091] Preferably, the volume of the electrolytic cell is 20L to 150L.

[0092] Preferably, the inlet and outlet of the electrolytic cell are respectively connected to peristaltic water pumps, which are used to control the inlet flow rate and the outlet flow rate, respectively.

[0093] This invention can control the inlet and outlet flow rates through a peristaltic water pump, thereby adjusting the treatment efficiency of pollutants in the water, shortening the time for photoelectrocatalytic advanced oxidation, and achieving the rational utilization of energy.

[0094] Preferably, the electrolytic cell is equipped with a stirring device.

[0095] For example, the light source uses a simulated sunlight system.

[0096] Preferably, the power source is a DC power source.

[0097] Preferably, the photoelectrocatalytic advanced oxidation wastewater treatment system further includes a water storage device. The inlet of the water storage device is connected to the outlet of the electrolytic cell via a pipe, and the outlet of the water storage device is connected to the inlet of the electrolytic cell via a pipe, for the purpose of realizing the recycling treatment of wastewater.

[0098] This invention uses a water storage device to repeatedly treat stubborn substances in water, further purifying the water until the water quality at the outlet meets the standards (COD less than 60 mg / L, ammonia nitrogen less than 15 mg / L). It is simple to operate, environmentally friendly, and suitable for treating water bodies with different water qualities.

[0099] Due to its significant efficiency, the photoelectrocatalytic advanced oxidation method for wastewater treatment is well-suited for short-term, multiple-operation cycles. After multiple cycles, the electrodes can be removed, activated, cleaned, washed, and recycled repeatedly, exhibiting long-term operational stability and strong resistance to shock loads. This invention allows for control based on the actual conditions of the influent and effluent, using a water storage device for buffering to facilitate secondary recycling. Wastewater treatment solutions can be tailored to different water bodies, adjusting the start-up time and power of pumps in different stages. The power supply current can be set linearly with time as the variable, reducing degradation energy consumption and improving the current efficiency of the electrochemical system to meet the expected treatment conditions. Attached Figure Description

[0100] Figure 1 This is a schematic diagram of the structure of the photoelectrocatalytic advanced oxidation wastewater treatment system in an embodiment of the present invention; wherein, 1 represents the photoanode, 2 represents the photocathode, 3 represents the electrolytic cell, 301 represents the inlet of the electrolytic cell, 302 represents the outlet of the electrolytic cell, 303 represents the peristaltic pump, 4 represents the power supply, 5 represents the light source, and 6 represents the water storage device.

[0101] Figure 2 This is a SEM image of Bi2O2WO4 in Embodiment 3 of the present invention;

[0102] Figure 3 This is a SEM image of the FeSe2 array in Embodiment 3 of the present invention;

[0103] Figures 4-5 This is a SEM image of the Bi2O2WO4 / FeSe2 array in Embodiment 3 of the present invention;

[0104] Figure 6This is an elemental analysis diagram of the Bi2O2WO4 / FeSe2 array in Example 3 of the present invention;

[0105] Figure 7 The XRD patterns of Bi2O2WO4, Bi2O2WO4 / FeSe2 array and FeSe2-Bi2O2WO4 in Embodiment 3 of the present invention are shown below.

[0106] Figure 8 Figure 1 shows the Mott-Schottky curves of the Bi2O2WO4, FeSe2 array, and Bi2O2WO4 / FeSe2 array in Embodiment 3 of the present invention; wherein, Figure 2a is the Mott-Schottky curve of Bi2O2WO4, Figure 2b is the Mott-Schottky curve of FeSe2 array, and Figure 2c is the Mott-Schottky curve of Bi2O2WO4 / FeSe2 array. Detailed Implementation

[0107] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0108] Please see Figure 1 The present invention provides a photoelectrocatalytic advanced oxidation wastewater treatment system, comprising a photoanode 1, a photocathode 2, an electrolytic cell 3, a power supply 4, a light source 5, and a water storage device 6;

[0109] The photoanode 1 and the photocathode 2 are located in the electrolytic cell 3, and the photoanode 1 and the photocathode 2 are respectively connected to the power supply 4 through wires;

[0110] The light source 5 is located outside the electrolytic cell 3 and is used to irradiate the electrolytic cell 3 with light.

[0111] The electrolytic cell 3 is equipped with peristaltic water pumps 303 at its inlet 301 and outlet 302, respectively, which are used to control the inlet flow rate and outlet flow rate.

[0112] The inlet of the water storage device 6 is connected to the outlet 302 of the electrolytic cell 3 via a pipe, and the outlet of the water storage device 6 is connected to the inlet 301 of the electrolytic cell 3 via a pipe, for the purpose of realizing the recycling treatment of sewage.

[0113] In this invention, the visible light radiation is provided by the light source of the HSX-F300 simulated sunlight system.

[0114] In this invention, all materials unless otherwise specified are commercially available products. All water used in this invention is deionized water. The wastewater used in this invention is taken from an industrial park. Testing showed that the industrial park wastewater had a COD of 1026 mg / L, an ammonia nitrogen value of 68 mg / L, a BOD of 275 mg / L, a suspended solids content of 93 mg / L, a manganese ion content of 6.3 mg / L, a pH of 5.2, and a color index with a dilution factor of 301.

[0115] Example 1

[0116] This embodiment provides a photoanode, comprising an anode substrate and a photoanode material loaded on the anode substrate; the photoanode material includes a FeSe2 array layer and a Bi2O2WO4-containing layer loaded on the FeSe2 array layer, the Bi2O2WO4-containing layer further comprising carbon nanofibers with a diameter of 150 nm and a length of 5 μm. The mass ratio of FeSe2, Bi2O2WO4, and carbon nanofibers in the photoanode material is 200:13:0.9.

[0117] The FeSe2 array layer is 3 μm thick, and the Bi2O2WO4 layer is 80 nm thick. The anode substrate is a molybdenum mesh with a length of 50 mm, a width of 200 mm, and a thickness of 2 mm.

[0118] The above-mentioned method for preparing a photoanode includes the following steps:

[0119] Preparation of S1 and FeSe2:

[0120] S1-1, Selenium powder is added to 18wt% NaBH4 solution, the mass ratio of selenium powder to NaBH4 solution is 1:10, mixed evenly, and the reduction reaction is carried out at room temperature for 30 min. The reaction system becomes colorless, and a divalent selenide solution is obtained.

[0121] In step S1-2, FeCl2·4H2O, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, and dodecyltrimethylammonium bromide (CTAB) were added to water and mixed thoroughly. This mixture was then combined with a divalent selenide solution at 50°C and 100 rpm for 2 hours (the mass ratio of FeCl2·4H2O, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, CTAB, water, and divalent selenide solution was 2:10:0.01:20:8). A redox reaction was then carried out in a reactor at 180°C for 5 hours. After cooling to room temperature, the solid and liquid were separated. The solid was washed three times with deionized water and three times with anhydrous ethanol, and then vacuum dried at 60°C for 5 hours to obtain FeSe2 with an average particle size of 13 nm.

[0122] Preparation of S2, Bi2O2WO4:

[0123] S2-1: Dissolve Na2WO4·2H2O in water, add Bi(NO3)3·5H2O, polyethylene glycol 2000, and pH adjuster (2.3M acetic acid solution and 2.3M ammonium acetate solution). The mass ratio of Na2WO4·2H2O, Bi(NO3)3·5H2O, polyethylene glycol 2000, pH adjuster, and water is 2:4:0.5:0.01:100. At this time, the pH of the system is 5. After hydrolysis reaction at 20℃ for 40 min, a suspension is obtained.

[0124] S2-2, the suspension was subjected to the first hydrothermal reaction in a high-pressure reactor at 160℃. After holding at the temperature for 12 hours, it was cooled to room temperature, and the solid and liquid were separated. The solid was washed three times with deionized water and three times with anhydrous ethanol, and then dried under vacuum at 60℃ for 5 hours to obtain Bi2O2WO4 with an average particle size of 60nm.

[0125] It should be noted that the order of S1 and S2 is not limited in this embodiment.

[0126] S3. The anode substrate is placed in acetone and water in sequence, sonicated for 10 min each, and then naturally dried. It is then immersed in a mixture of FeSe2 and water for 30 min, with a mass ratio of FeSe2 to water of 1:80. After that, it is taken out and placed in a 100℃ reactor for a second hydrothermal reaction. After holding at the temperature for 35 min, the primary electrode is obtained.

[0127] S4. The primary electrode is immersed in a mixture of FeSe2, KH560 and 50wt% of a polyvinyl ketone K30 aqueous solution, with a mass ratio of FeSe2, KH560 and polyvinyl ketone K30 aqueous solution of 2:1:10. The third hydrothermal reaction is carried out in a reactor at 80℃. After holding at this temperature for 8 hours, a FeSe2 array layer is formed. The electrode is then cooled to room temperature, washed with water and dried to obtain the FeSe2 array electrode.

[0128] S5. Using a coating machine, a mixture of Bi2O2WO4, carbon nanofibers, 200-mesh polyamide with a molecular weight of 5000 and 50wt% povidone K30 aqueous solution (the mass ratio of Bi2O2WO4, polyamide and povidone K30 aqueous solution is 6:1:10) is coated onto the FeSe2 array electrode. The coating thickness is 80nm. After natural drying for 4min, it is calcined at 160℃ for 120min to form a Bi2O2WO4-containing layer. After cooling to room temperature, a photoelectric anode containing a Bi2O2WO4 / FeSe2 array is obtained.

[0129] Example 2

[0130] This embodiment provides a photoanode, comprising an anode substrate and a photoanode material loaded on the anode substrate; the photoanode material includes a FeSe2 array layer and a Bi2O2WO4-containing layer loaded on the FeSe2 array layer, the Bi2O2WO4-containing layer further comprising carbon nanofibers with a diameter of 180 nm and a length of 10 μm. The mass ratio of FeSe2, Bi2O2WO4, and carbon nanofibers in the photoanode material is 200:25:1.

[0131] The FeSe2 array layer is 4 μm thick, and the Bi2O2WO4 layer is 100 nm thick. The anode substrate is a titanium sheet with a length of 60 mm, a width of 120 mm, and a thickness of 3 mm.

[0132] The above-mentioned method for preparing a photoanode includes the following steps:

[0133] Preparation of S1 and FeSe2:

[0134] S1-1, Selenium powder is added to a 20wt% NaBH4 solution, the mass ratio of selenium powder to NaBH4 solution is 1:6, mixed evenly, and the reduction reaction is carried out at room temperature for 40 minutes. The reaction system becomes colorless, and a divalent selenide solution is obtained.

[0135] S1-2, FeCl2·4H2O, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid and CTAB were added to water and mixed evenly. The mixture was then mixed with a divalent selenide solution at 60℃ and 120rpm for 1.5h (the mass ratio of FeCl2·4H2O, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, CTAB, water and divalent selenide solution was 3:15:0.02:40:15). The mixture was then subjected to a redox reaction at 185℃ for 5h. After cooling to room temperature, the solid and liquid were separated. The solid was washed three times with deionized water and three times with anhydrous ethanol. It was then vacuum dried at 70℃ for 5h to obtain FeSe2 with an average particle size of 40nm.

[0136] Preparation of S2, Bi2O2WO4:

[0137] S2-1: Dissolve Na2WO4·2H2O in water, add Bi(NO3)3·5H2O, polyethylene glycol 2000, and pH adjuster (2.0M acetic acid solution and 2.1M ammonium acetate solution). The mass ratio of Na2WO4·2H2O, Bi(NO3)3·5H2O, polyethylene glycol 2000, pH adjuster, and water is 4:8:0.7:0.02:120. At this time, the pH of the system is 5.5. After hydrolysis reaction at 25℃ for 30 min, a suspension is obtained.

[0138] S2-2, the suspension was subjected to the first hydrothermal reaction in a high-pressure reactor at 170℃. After holding at this temperature for 10 hours, it was cooled to room temperature, and the solid and liquid were separated. The solid was washed 4 times with deionized water and 4 times with anhydrous ethanol, and then dried under vacuum at 70℃ for 5 hours to obtain Bi2O2WO4 with an average particle size of 80nm.

[0139] It should be noted that the order of S1 and S2 is not limited in this embodiment.

[0140] S3. The anode substrate is placed in acetone and water in sequence, and ultrasonicated for 10 min and 15 min respectively. After natural drying, it is immersed in a mixture of FeSe2 and water for 40 min. The mass ratio of FeSe2 to water is 2:90. Then it is taken out and carried out in a reactor at 110℃ for a second hydrothermal reaction. After holding at the temperature for 30 min, the primary electrode is obtained.

[0141] S4. The primary electrode is immersed in a mixture of FeSe2, KH560 and 40wt% of a polyvinyl ketone K30 aqueous solution, with a mass ratio of FeSe2, KH560 and polyvinyl ketone K30 aqueous solution of 3:2:15. The third hydrothermal reaction is carried out in a reactor at 90℃. After holding at this temperature for 7 hours, a FeSe2 array layer is formed. The electrode is then cooled to room temperature, washed with water and dried to obtain the FeSe2 array electrode.

[0142] S5. Using a coating machine, a mixture of Bi2O2WO4, carbon nanofibers, 260-mesh polyamide with a molecular weight of 8000 and 60wt% of a polyvinyl chloride K30 aqueous solution (the mass ratio of Bi2O2WO4, polyamide and polyvinyl chloride K30 aqueous solution is 16:4:30) is coated onto the FeSe2 array electrode. The coating thickness is 100nm. After natural drying for 5min, it is calcined at 180℃ for 100min to form a Bi2O2WO4-containing layer. After cooling to room temperature, a photoelectric anode containing a Bi2O2WO4 / FeSe2 array is obtained.

[0143] Example 3

[0144] This embodiment provides a photoanode, comprising an anode substrate and a photoanode material loaded on the anode substrate; the photoanode material includes a FeSe2 array layer and a Bi2O2WO4-containing layer loaded on the FeSe2 array layer, the Bi2O2WO4-containing layer further comprising carbon nanofibers with a diameter of 200 nm and a length of 15 μm. The mass ratio of FeSe2, Bi2O2WO4, and carbon nanofibers in the photoanode material is 200:30:1.2.

[0145] The FeSe2 array layer is 4 μm thick, and the Bi2O2WO4 layer is 180 nm thick. The anode substrate is a nickel foam with a length of 800 mm, a width of 140 mm, and a thickness of 3.5 mm.

[0146] The above-mentioned method for preparing a photoanode includes the following steps:

[0147] Preparation of S1 and FeSe2:

[0148] S1-1, Selenium powder is added to a 20wt% NaBH4 solution, with a mass ratio of selenium powder to NaBH4 solution of 1:3.5. After mixing evenly, the reaction is carried out at room temperature for 40 minutes. The reaction system becomes colorless, and a divalent selenide solution is obtained.

[0149] S1-2, FeCl2·4H2O, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid and CTAB were added to water and mixed evenly. The mixture was then mixed with a divalent selenide solution at 60℃ and 180rpm for 1.5h (the mass ratio of FeCl2·4H2O, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, CTAB, water and divalent selenide solution was 8:20:0.04:80:20). The mixture was then subjected to a redox reaction at 190℃ for 5h. After cooling to room temperature, the solid and liquid were separated. The solid was washed 4 times with deionized water and 4 times with anhydrous ethanol. It was then vacuum dried at 80℃ for 4h to obtain FeSe2 with an average particle size of 120nm.

[0150] Preparation of S2, Bi2O2WO4:

[0151] S2-1: Dissolve Na2WO4·2H2O in water, add Bi(NO3)3·5H2O, polyethylene glycol 2000, and pH adjuster (2M acetic acid solution and 2M ammonium acetate solution). The mass ratio of Na2WO4·2H2O, Bi(NO3)3·5H2O, polyethylene glycol 2000, pH adjuster, and water is 7:12:0.8:0.04:150. At this time, the pH of the system is 6. After hydrolysis reaction at 30℃ for 35 min, a suspension is obtained.

[0152] S2-2, the suspension was subjected to the first hydrothermal reaction in a high-pressure reactor at 180℃. After holding at the temperature for 10 hours, it was cooled to room temperature, and the solid and liquid were separated. The solid was washed 4 times with deionized water and 4 times with anhydrous ethanol, and then dried under vacuum at 80℃ for 5 hours to obtain Bi2O2WO4 with an average particle size of 120nm.

[0153] The obtained product was subjected to electron microscopy and X-ray diffraction tests, and the results are as follows: Figure 2 and Figure 7 As shown; the above-prepared product was subjected to Mott-Schottky curve testing, and the results are as follows. Figure 8 As shown in Figure a. The results show that the slope of the Mott-Schottky curve of Bi2O2WO4 prepared in this embodiment is negative, indicating that Bi2O2WO4 belongs to the p-type semiconductor.

[0154] It should be noted that the order of S1 and S2 is not limited in this embodiment.

[0155] S3. The anode substrate is placed in acetone and water in sequence, sonicated for 12 min each, and then naturally dried. It is then immersed in a mixture of FeSe2 and water for 50 min, with a mass ratio of FeSe2 to water of 3:90. After that, it is taken out and placed in a reactor at 110℃ for a second hydrothermal reaction. After holding at this temperature for 30 min, the primary electrode is obtained.

[0156] S4. The primary electrode is immersed in a mixture of FeSe2, KH560 and 50wt% of a polyvinyl ketone K30 aqueous solution, with a mass ratio of FeSe2, KH560 and polyvinyl ketone K30 aqueous solution of 4:3:15. The third hydrothermal reaction is carried out in a reactor at 110℃. After holding at this temperature for 6 hours, a FeSe2 array layer is formed. The electrode is then cooled to room temperature, washed with water and dried to obtain the FeSe2 array electrode.

[0157] The obtained product was subjected to scanning electron microscopy, and the results are as follows: Figure 3 As shown; Mott-Schottky curve testing was performed on the FeSe2 array, and the results are as follows. Figure 8 As shown in b. The results show that the slope of the Mott-Schottky curve of the FeSe2 array prepared in this embodiment is positive, and the FeSe2 array belongs to the n-type semiconductor.

[0158] S5. Using a coating machine, a mixture of Bi2O2WO4, carbon nanofibers, 300-mesh polyamide with a molecular weight of 9870 and 50wt% of a polyvinylpyrrolidone K30 aqueous solution (the mass ratio of Bi2O2WO4, polyamide and polyvinylpyrrolidone K30 aqueous solution is 25:6:70) is coated onto the FeSe2 array electrode. The coating thickness is 180nm. After natural drying for 8min, it is calcined at 220℃ for 90min to form a Bi2O2WO4-containing layer. After cooling to room temperature, a photoelectric anode containing a Bi2O2WO4 / FeSe2 array is obtained.

[0159] The surface of the above-prepared material was subjected to scanning electron microscopy and X-ray diffraction tests, and the results are as follows: Figures 4-5 and Figure 7 As shown; elemental analysis of the Bi₂O₂WO₄ / FeSe₂ array was performed, and the results are as follows. Figure 6 As shown; to further verify the structure of the Bi2O2WO4 / FeSe2 array, X-ray diffraction tests were performed on a mixture of FeSe2 and Bi2O2WO4 with a mass ratio of 200:30 (denoted as FeSe2-Bi2O2WO4), and the results are shown below. Figure 7 As shown; and Mott-Schottky curve tests were performed on the Bi2O2WO4 / FeSe2 array, with results as follows. Figure 8As shown in c. The results show that the Bi2O2WO4 / FeSe2 array prepared in this embodiment contains Bi2O2WO4 and FeSe2, and the Mott-Schottky curve is inverted V-shaped, forming a pn heterojunction.

[0160] Example 4

[0161] This embodiment provides a photoanode, comprising an anode substrate and a photoanode material loaded on the anode substrate; the photoanode material includes a FeSe2 array layer and a Bi2O2WO4-containing layer loaded on the FeSe2 array layer, the Bi2O2WO4-containing layer further comprising carbon nanofibers with a diameter of 200 nm and a length of 20 μm. The mass ratio of FeSe2, Bi2O2WO4, and carbon nanofibers in the photoanode material is 200:45:1.5.

[0162] The FeSe2 array layer is 5 μm thick, and the Bi2O2WO4 layer is 200 nm thick. The anode substrate is a titanium mesh with a length of 100 mm, a width of 200 mm, and a thickness of 4 mm.

[0163] The above-mentioned method for preparing a photoanode includes the following steps:

[0164] Preparation of S1 and FeSe2:

[0165] S1-1, Selenium powder is added to a 22wt% NaBH4 solution, with a mass ratio of selenium powder to NaBH4 solution of 1:3. After mixing evenly, the reaction is carried out at room temperature for 50 minutes. The reaction system becomes colorless, and a divalent selenide solution is obtained.

[0166] S1-2, FeCl2·4H2O, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid and CTAB were added to water and mixed evenly. The mixture was then mixed with a divalent selenide solution at 70℃ and 200rpm for 1h (the mass ratio of FeCl2·4H2O, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, CTAB, water and divalent selenide solution was 10:30:0.05:100:28). The mixture was then subjected to a redox reaction in a reactor at 200℃ for 3h. After cooling to room temperature, the solid and liquid were separated. The solid was washed 4 times with deionized water and 4 times with anhydrous ethanol. It was then vacuum dried at 90℃ for 3h to obtain FeSe2 with an average particle size of 150nm.

[0167] Preparation of S2, Bi2O2WO4:

[0168] S2-1: Dissolve Na2WO4·2H2O in water, add Bi(NO3)3·5H2O, polyethylene glycol 2000, and pH adjuster (1.7M acetic acid solution and 1.7M ammonium acetate solution). The mass ratio of Na2WO4·2H2O, Bi(NO3)3·5H2O, polyethylene glycol 2000, pH adjuster, and water is 8:16:1:0.05:160. At this time, the pH of the system is 5.5. After hydrolysis reaction at 35℃ for 30 min, a suspension is obtained.

[0169] S2-2, the suspension was subjected to the first hydrothermal reaction in a high-pressure reactor at 190℃. After holding at this temperature for 8 hours, it was cooled to room temperature, and the solid and liquid were separated. The solid was washed 5 times with deionized water and 5 times with anhydrous ethanol, and then dried under vacuum at 80℃ for 5 hours to obtain Bi2O2WO4 with an average particle size of 145nm.

[0170] It should be noted that the order of S1 and S2 is not limited in this embodiment.

[0171] S3. The anode substrate is placed in acetone and water in sequence, sonicated for 10 min each, and then naturally dried. It is then immersed in a mixture of FeSe2 and water for 60 min, with a mass ratio of FeSe2 to water of 4:100. After that, it is taken out and placed in a reactor at 120℃ for a second hydrothermal reaction. After holding at this temperature for 25 min, the primary electrode is obtained.

[0172] S4. The primary electrode is immersed in a mixture of FeSe2, KH560 and 40wt% of a polyvinyl ketone K30 aqueous solution, with a mass ratio of FeSe2, KH560 and polyvinyl ketone K30 aqueous solution of 5:4:20. The third hydrothermal reaction is carried out in a reactor at 120℃. After holding at this temperature for 4.5h, a FeSe2 array layer is formed. The electrode is then cooled to room temperature, washed with water and dried to obtain the FeSe2 array electrode.

[0173] S5. Using a coating machine, a mixture of Bi2O2WO4, carbon nanofibers, 300-mesh polyamide with a molecular weight of 12000 and 50wt% of a polyvinyl chloride K30 aqueous solution (the mass ratio of Bi2O2WO4, polyamide and polyvinyl chloride K30 aqueous solution is 32:8:80) is coated onto the FeSe2 array electrode. The coating thickness is 200nm. After natural drying for 10min, it is calcined at 260℃ for 65min to form a Bi2O2WO4-containing layer. After cooling to room temperature, a photoelectric anode containing a Bi2O2WO4 / FeSe2 array is obtained.

[0174] Comparative Example 1

[0175] This comparative example provides a photoanode similar to that of Example 3, except that the Bi2O2WO4 in the Bi2O2WO4 layer is replaced with ferrous tungstate. All other conditions are the same as in Example 3 and will not be repeated.

[0176] The preparation method of the above photoanode is similar to that of Example 3, except that step S2 is omitted and Bi2O2WO4 in S5 is replaced with an equal mass of ferrous tungstate. The remaining conditions are the same as in Example 3 and will not be repeated.

[0177] Comparative Example 2

[0178] This comparative example provides a photoanode, similar to Example 3, except that the Bi2O2WO4 in the Bi2O2WO4 layer is replaced with BiWO6. All other conditions are the same as in Example 3 and will not be repeated.

[0179] The preparation method of the above photoanode is similar to that of Example 3, except that step S2 is deleted and Bi2O2WO4 in S5 is replaced with an equal mass of BiWO6. The remaining conditions are the same as in Example 3 and will not be repeated.

[0180] Comparative Example 3

[0181] This comparative example provides a photoanode, similar to that of Example 2, except that the Bi2O2WO4 in the Bi2O2WO4 layer is replaced with BiVO4. All other conditions are the same as in Example 2 and will not be repeated.

[0182] The preparation method of the above photoanode is similar to that of Example 2, except that step S2 is omitted and Bi2O2WO4 in S5 is replaced with an equal mass of BiVO4. The remaining conditions are the same as in Example 2 and will not be repeated here.

[0183] Comparative Example 4

[0184] This comparative example provides a photoanode, similar to Example 3, except that the FeSe2 in the FeSe2 array layer is replaced with TiO2. All other conditions are the same as in Example 3 and will not be repeated.

[0185] The preparation method of the above photoanode is similar to that of Example 3, except that step S1 is omitted, and FeSe2 in S3-S4 is replaced with an equal mass of TiO2. The remaining conditions are the same as in Example 3 and will not be repeated.

[0186] Comparative Example 5

[0187] This comparative example provides a photoanode similar to that of Example 2, except that the FeSe2 in the FeSe2 array layer is replaced with ZnO. All other conditions are the same as in Example 2 and will not be repeated.

[0188] The preparation method of the above photoanode is similar to that of Example 2, except that step S1 is omitted and FeSe2 in S3-S4 is replaced with an equal mass of ZnO. The remaining conditions are the same as in Example 2 and will not be repeated here.

[0189] Comparative Example 6

[0190] This comparative example provides a photoanode similar to that of Example 3, except that the Bi2O2WO4 in the Bi2O2WO4 layer is replaced with BiWO6, and the FeSe2 in the FeSe2 array layer is replaced with TiO2. All other conditions are the same as in Example 3 and will not be repeated here.

[0191] The preparation method of the above photoanode is similar to that of Example 3, except that steps S1-S2 are deleted, FeSe2 in S3-S4 is replaced with an equal mass of TiO2, and Bi2O2WO4 in S5 is replaced with an equal mass of BiWO6. The remaining conditions are the same as in Example 3 and will not be repeated.

[0192] Application Example 1

[0193] This application example provides a method for wastewater treatment using a photoelectrocatalytic advanced oxidation wastewater treatment system.

[0194] The photoelectrocatalytic advanced oxidation wastewater treatment system includes a photoanode 1, a photocathode 2, an electrolytic cell 3, a power supply 4 (DC power supply), a light source 5, and a water storage device 6;

[0195] The photoanode 1 and the photocathode 2 are located in the electrolytic cell 3, and the photoanode 1 and the photocathode 2 are respectively connected to the power supply 4 through wires;

[0196] The light source 5 is located outside the electrolytic cell 3 and is used to irradiate the electrolytic cell 3 with light;

[0197] The electrolytic cell 3 is equipped with peristaltic water pumps 303 connected to the inlet 301 and outlet 302 respectively, which are used to control the inlet flow rate and outlet flow rate respectively; the electrolytic cell 3 is equipped with a stirring device.

[0198] The inlet of the water storage device 6 is connected to the outlet 302 of the electrolytic cell 3 through a pipe, and the outlet of the water storage device 6 is connected to the inlet 301 of the electrolytic cell 3 through a pipe, which is used to realize the recycling treatment of sewage.

[0199] In this process, the photoanode 1 is the photoanode of Example 1, and the photocathode 2 is a coated tungsten electrode with the same size as the photoanode; the volume of the electrolytic cell is 100L.

[0200] Wastewater treatment methods include the following steps:

[0201] SI: Introduce the wastewater to be treated into the electrolytic cell 3 of the photoelectrocatalytic advanced oxidation wastewater treatment system, add 0.1wt% sodium hydroxide solution to adjust the pH of the wastewater to be treated to 5.0, then add anhydrous sodium sulfate to adjust the conductivity of the wastewater to be treated to 550μS / cm, and simultaneously adjust the voltage of the power supply 4 to 80V, turn on the simulated solar light source 5 and the stirring device, and perform photoelectrocatalytic treatment on the wastewater for 60min.

[0202] SII, the wastewater that has undergone one photoelectrocatalytic treatment is discharged into the water storage device 6 by the peristaltic water pump 303. The treatment effect of the photoelectrocatalytic advanced oxidation wastewater treatment system on wastewater is evaluated by real-time monitoring of the COD and ammonia nitrogen values ​​of the influent and effluent (see Table 1).

[0203] Application Example 2

[0204] This application example provides a method for wastewater treatment using a photoelectrocatalytic advanced oxidation wastewater treatment system.

[0205] The photoelectrocatalytic advanced oxidation wastewater treatment system is similar to Application Example 1, except that: the photoanode 1 is the same as the photoanode in Example 2, and the photocathode 2 is a titanium mesh of the same size as the photoanode. The remaining devices and connections are the same as in Application Example 1 and will not be described again.

[0206] The wastewater treatment method is the same as in Application Example 1, and will not be repeated here.

[0207] Application Example 3

[0208] This application example provides a method for wastewater treatment using a photoelectrocatalytic advanced oxidation wastewater treatment system.

[0209] The photoelectrocatalytic advanced oxidation wastewater treatment system is similar to Application Example 1, except that: the photoanode 1 is the same as the photoanode in Example 3, and the photocathode 2 is a graphite felt electrode of the same size as the photoanode. The remaining devices and connections are the same as in Application Example 1 and will not be described again.

[0210] The wastewater treatment method is the same as in Application Example 1, and will not be repeated here.

[0211] Application Example 4

[0212] This application example provides a method for wastewater treatment using a photoelectrocatalytic advanced oxidation wastewater treatment system.

[0213] The photoelectrocatalytic advanced oxidation wastewater treatment system is similar to Application Example 1, except that: the photoanode 1 is the same as the photoanode in Example 4, and the photocathode 2 is a carbon rod electrode of the same size as the photoanode. The remaining devices and connections are the same as in Application Example 1 and will not be described again.

[0214] The wastewater treatment method is the same as in Application Example 1, and will not be repeated here.

[0215] Application Comparative Example 1

[0216] This application example provides a method for wastewater treatment using a photoelectrocatalytic advanced oxidation wastewater treatment system.

[0217] The photoelectrocatalytic advanced oxidation wastewater treatment system is similar to that in Application Example 3, except that the photoelectroanode 1 is the same as that in Comparative Example 1. The remaining devices and connections are the same as in Application Example 1 and will not be described again.

[0218] The wastewater treatment method is the same as in Application Example 1, and will not be repeated here.

[0219] Application Comparative Example 2

[0220] This application example provides a method for wastewater treatment using a photoelectrocatalytic advanced oxidation wastewater treatment system.

[0221] The photoelectrocatalytic advanced oxidation wastewater treatment system is similar to that in Application Example 3, except that the photoelectroanode 1 is the same as that in Comparative Example 2. The remaining devices and connections are the same as in Application Example 3 and will not be described again.

[0222] The wastewater treatment method is the same as in Application Example 1, and will not be repeated here.

[0223] Application Comparative Example 3

[0224] This application example provides a method for wastewater treatment using a photoelectrocatalytic advanced oxidation wastewater treatment system.

[0225] The photoelectrocatalytic advanced oxidation wastewater treatment system is similar to that in Application Example 2, except that the photoelectroanode 1 is the same as that in Comparative Example 3. The remaining devices and connections are the same as in Application Example 2 and will not be described again.

[0226] The wastewater treatment method is the same as in Application Example 1, and will not be repeated here.

[0227] Application Comparative Example 4

[0228] This application example provides a method for wastewater treatment using a photoelectrocatalytic advanced oxidation wastewater treatment system.

[0229] The photoelectrocatalytic advanced oxidation wastewater treatment system is similar to that in Application Example 3, except that the photoelectroanode 1 is the same as that in Comparative Example 4. The remaining devices and connections are the same as in Application Example 3 and will not be described again.

[0230] The wastewater treatment method is the same as in Application Example 1, and will not be repeated here.

[0231] Application Comparative Example 5

[0232] This application example provides a method for wastewater treatment using a photoelectrocatalytic advanced oxidation wastewater treatment system.

[0233] The photoelectrocatalytic advanced oxidation wastewater treatment system is similar to that in Application Example 2, except that the photoelectroanode 1 is the same as that in Comparative Example 5. The remaining devices and connections are the same as in Application Example 2 and will not be described again.

[0234] The wastewater treatment method is the same as in Application Example 1, and will not be repeated here.

[0235] Application Comparative Example 6

[0236] This application example provides a method for wastewater treatment using a photoelectrocatalytic advanced oxidation wastewater treatment system.

[0237] The photoelectrocatalytic advanced oxidation wastewater treatment system is similar to that in Application Example 3, except that the photoelectroanode 1 is the same as that in Comparative Example 6. The remaining devices and connections are the same as in Application Example 3 and will not be described again.

[0238] The wastewater treatment method is the same as in Application Example 1, and will not be repeated here.

[0239] Table 1. Effluent performance indicators of application examples and comparative examples

[0240]

[0241] The wastewater was taken from the industrial park. The test results showed that the industrial park wastewater had a COD of 1026 mg / L, an ammonia nitrogen value of 68 mg / L, a BOD of 275 mg / L, a suspended solids content of 93 mg / L, a manganese ion content of 6.3 mg / L, a pH of 5.2, and a color index with a dilution factor of 301.

[0242] As shown in Table 1, after the wastewater was treated by the photoelectrocatalytic advanced oxidation wastewater treatment system in Examples 1-4, the effluent performance indicators, including COD, ammonia nitrogen, BOD, SS, and color, were all better than the national Class I standard, indicating that the photoelectrocatalytic advanced oxidation wastewater treatment system provided by this invention can effectively treat industrial wastewater at a deeper level.

[0243] Compared to Examples 2-3, Comparative Examples 1-3 and Comparative Example 6 used non-Bi2O2WO4 semiconductors as photoanodes. After wastewater treatment, the effluent performance test results showed a significant increase in COD and ammonia nitrogen levels, with the ammonia nitrogen value even reaching 66 mg / L, far exceeding the national Class I standard. This indicates that replacing the Bi2O2WO4 semiconductor nanomaterial in the photoanode reduced the efficiency of its photoelectrocatalytic oxidation reaction, failing to leverage the synergistic effect of photocatalysis and electrocatalysis of FeSe2 and Bi2O2WO4, resulting in a significant decrease in the overall water treatment performance compared to the comparative examples.

[0244] Compared to Examples 1-3, Comparative Examples 4-6 used non-nano FeSe2 arrays as photoanodes. After wastewater treatment, the effluent performance test results showed a significant decrease in the purification performance of the photoelectrocatalytic advanced oxidation wastewater treatment system. This further demonstrates that the present invention, by using a composite of nano FeSe2 and Bi2O2WO4 semiconductors, can fully leverage the synergistic effect of the composite material's photoanode and cathode. Under illumination and an applied electric field, a large number of electrons and holes are generated. After separation, the electrons and holes move directionally, accumulating at the anode and cathode and generating a large number of active free radicals. These active free radicals react with pollutants in the water, significantly improving the water purification efficiency.

[0245] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A photoanode, characterized in that, The invention includes an anode substrate and a photoelectric anode material loaded on the anode substrate, wherein the photoelectric anode material includes a FeSe2 array layer and a Bi2O2WO4-containing layer loaded on the FeSe2 array layer; The method for preparing the photoanode includes the following steps: Sa, the anode substrate is immersed in a mixture of FeSe2 and water to carry out a second hydrothermal reaction to obtain the primary electrode; Sb, the primary electrode is immersed in a mixture of FeSe2, silane coupling agent and cosolvent, and a third hydrothermal reaction is carried out to form a FeSe2 array layer, thus obtaining a FeSe2 array electrode; Sc, a mixture of Bi2O2WO4, binder and co-solvent is coated onto the FeSe2 array electrode, and then calcined to form a Bi2O2WO4 layer, thus obtaining a photoanode.

2. The photoanode as described in claim 1, characterized in that, The thickness of the FeSe2 array layer is 3μm~5μm; and / or The thickness of the Bi2O2WO4 layer is 80nm~200nm.

3. The photoanode as described in claim 1 or 2, characterized in that, The Bi2O2WO4-containing layer also includes carbon nanofibers; The carbon nanofibers have a diameter of 150 nm to 200 nm and a length of 5 μm to 20 μm. The mass ratio of FeSe2, Bi2O2WO4 and carbon nanofibers in the photoelectric anode material is 200:(10~50):(0.8~1.6).

4. The photoanode as described in claim 3, characterized in that, The preparation method of FeSe2 includes the following steps: S1-1, Selenium powder is added to a reducing agent solution to carry out a reduction reaction, yielding a divalent selenide solution; S1-2, ferrous salt, chelating agent and first dispersant are added to water, mixed with the ferrous selenide solution, and a redox reaction is carried out to obtain FeSe2; The preparation method of Bi2O2WO4 includes the following steps: S2-1, tungstate, bismuth salt, second dispersant and pH adjuster are added to water and hydrolyzed under weak acid conditions to obtain a suspension; S2-2, the suspension is subjected to a first hydrothermal reaction to obtain Bi2O2WO4.

5. The photoanode as described in claim 4, characterized in that, In S1-1, the reducing agent solution comprises 18wt%~22wt% sodium borohydride solution, and the mass ratio of selenium powder to reducing agent solution is 1:(2~15); and / or In S1-1, the reduction reaction is carried out at a temperature of 20℃~30℃ for a reaction time of 30min~50min; and / or In S1-2, the divalent ferric salt includes ferrous chloride, the chelating agent includes N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, and the first dispersant includes dodecyltrimethylammonium bromide; and / or In S1-2, the mass ratio of the divalent iron salt, chelating agent, first dispersant, water, and divalent selenide solution is (2~10):(10~30):(0.01~0.05):(20~100):(6~30); and / or In S1-2, the redox reaction is carried out at a temperature of 180℃~200℃ for a reaction time of 3h~6h; and / or In S2-1, the tungstate includes sodium tungstate, the bismuth salt includes bismuth nitrate, the second dispersant includes polyethylene glycol, and the pH adjuster includes a 1.7M~2.3M acetic acid solution and a 1.7M~2.3M ammonium acetate solution; and / or In S2-1, the mass ratio of the tungstate, bismuth salt, second dispersant, and water is (2~8):(4~16):(0.5~1):(100~160), and the weak acid condition is pH=5~6; and / or In S2-1, the hydrolysis reaction is carried out at a temperature of 20℃~35℃ for a reaction time of 30min~40min; and / or In S2-2, the temperature of the first hydrothermal reaction is 160℃~190℃, and the reaction time is 8h~12h.

6. The photoanode as described in claim 1, characterized in that, In Sa, the mass ratio of FeSe2 to water is (1~4):(80~100); and / or In Sa, the temperature of the second hydrothermal reaction is 100℃~120℃, and the reaction time is 25min~40min; and / or In Sb and Sc, the co-solvent comprises 40wt% to 60wt% of a povidone aqueous solution; and / or In Sb, the mass ratio of FeSe2, silane coupling agent, and co-solvent is (2~5):(1~4):(10~20); and / or In Sb, the temperature of the third hydrothermal reaction is 80℃~120℃, and the reaction time is 4h~8h; and / or In Sc, the mixture further includes carbon nanofibers; and / or In Sc, the adhesive comprises polyamide; and / or In Sc, the mass ratio of Bi2O2WO4, binder, and co-solvent is (6~32):(1~8):(10~80); and / or In Sc, the calcination temperature is 160℃~260℃, and the calcination time is 60min~120min.

7. The method for preparing a photoanode according to any one of claims 1 to 6, characterized in that, Includes the following steps: Sa, the anode substrate is immersed in a mixture of FeSe2 and water to carry out a second hydrothermal reaction to obtain the primary electrode; Sb, the primary electrode is immersed in a mixture of FeSe2, silane coupling agent and cosolvent, and a third hydrothermal reaction is carried out to form a FeSe2 array layer, thus obtaining a FeSe2 array electrode; Sc, a mixture of Bi2O2WO4, binder and co-solvent is coated onto the FeSe2 array electrode, and then calcined to form a Bi2O2WO4 layer, thus obtaining a photoanode.

8. The method for preparing a photoanode as described in claim 7, characterized in that, In Sa, the mass ratio of FeSe2 to water is (1~4):(80~100); and / or In Sa, the temperature of the second hydrothermal reaction is 100℃~120℃, and the reaction time is 25min~40min; and / or In Sb and Sc, the co-solvent comprises 40wt% to 60wt% of a povidone aqueous solution; and / or In Sb, the mass ratio of FeSe2, silane coupling agent, and co-solvent is (2~5):(1~4):(10~20); and / or In Sb, the temperature of the third hydrothermal reaction is 80℃~120℃, and the reaction time is 4h~8h; and / or In Sc, the mixture further includes carbon nanofibers; and / or In Sc, the adhesive comprises polyamide; and / or In Sc, the mass ratio of Bi2O2WO4, binder, and co-solvent is (6~32):(1~8):(10~80); and / or In Sc, the calcination temperature is 160℃~260℃, and the calcination time is 60min~120min.

9. The application of the photoanode according to any one of claims 1 to 6 in wastewater treatment.

10. A photoelectrocatalytic advanced oxidation wastewater treatment system, characterized in that, Includes the photoanode, photocathode, electrolytic cell, power supply, and light source as described in any one of claims 1 to 6; The photoanode and the photocathode are located in the electrolytic cell, and the photoanode and the photocathode are respectively connected to the power source via wires; The light source is located outside the electrolytic cell and is used to irradiate the electrolytic cell with light.

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