A photoanode for synchronously treating ammonia nitrogen and organic matter in high-chloride wastewater and a preparation method thereof

Abstract

The present invention discloses a photoanode material applied to the synchronous treatment of ammonia nitrogen and refractory organic compounds in high-chloride wastewater by photoelectrocatalysis. It is characterized in that tungsten oxide is in-situ loaded on doped-fluorine SnO2 conductive glass in sequence by layer, oriented crystal plane bismuth vanadate with a carrier space pre-separation structure is hydrothermally grown, and cobalt borate salt cocatalyst is photo-assisted electro-deposited, which greatly improves the photoelectric performance from multiple perspectives such as the effective separation of photo-generated electrons and holes, the charge transfer resistance at the photoanode / solution interface, and the conversion rate of photo-generated holes to redox equivalent substances. The photoelectrochemical system using it as the photoanode realizes the in-situ generation of strongly oxidizing active chlorine by using chloride ions, promotes the oxidation of refractory organic compounds and ammonia nitrogen, effectively controls the generation amount of nitrate nitrogen at the same time, improves the denitrification efficiency, and has the advantages of high efficiency and stability in the synchronous removal process of ammonia nitrogen and refractory organic compounds in high-chloride wastewater.

Description

Technical Field

[0001] The present invention relates to the field of high-salt wastewater treatment, and specifically relates to a photoanode material for synchronously treating ammonia nitrogen and refractory organic matter in high-chloride salt wastewater by photoelectrocatalysis and a preparation method thereof. Background Technique

[0002] The structures of pollutants in the tail water generated by various industries are becoming increasingly complex, posing new requirements for wastewater treatment processes. The efficient removal of chemical oxygen demand (COD) and ammonia nitrogen (NH4 + -N) is a key problem that has long existed. Specifically, during the oxidation process of NH4 + -N, a large amount of nitrate nitrogen (NO3 - -N) is easily formed due to insufficient carbon source, resulting in an unsatisfactory total nitrogen removal rate in the wastewater. At the same time, refractory organic matter with complex structures is difficult to be effectively degraded by the processes of traditional sewage treatment plants due to its high chemical stability. For example, pharmaceuticals and personal care products (PPCPs) mainly originate from domestic waste drugs and wastewater from the pharmaceutical industry and have been detected in urban wastewater many times in recent years. In addition, many complexly polluted wastewaters contain high concentrations of inorganic salts, such as pharmaceutical wastewater, textile wastewater, leather-making wastewater, and landfill leachate, etc. The Cl - content can even reach several thousand or even tens of thousands of mg / L. The presence of a large number of inorganic salt ions (Cl - , SO4 2- , Na + , K + , Ca + etc.) has a significant inhibitory effect on the biological treatment technologies of conventional sewage treatment plants. Therefore, the combined pollution problem of NH4 + -N and refractory organic matter in high-salt wastewater urgently needs a more efficient and powerful synchronous treatment method.

[0003] The breakpoint chlorination method is to add hypochlorous acid or hypochlorite to generate residual chlorine with strong oxidizing properties, which is widely used for wastewater decolorization, deodorization, and drinking water disinfection. In recent years, its ability to oxidize NH4 + -N has also received attention (Chinese Patent Publication Nos.: CN113387482A, CN102863109A, CN108218065B). However, the addition of chemicals will not only increase the treatment cost but also pose problems of transportation safety risks. Therefore, it is possible to consider using Cl -, in-situ generation of active chlorine species is achieved through the excitation of external energy. The photoelectrochemical (PEC) system is a synergistic technology of photocatalysis and electrocatalysis. Compared with a single photo / electrocatalytic system, the PEC technology can not only avoid excessive consumption of electric energy, but also improve the utilization efficiency of visible light energy. Among them, the photoanode structure is one of the key factors affecting the photoelectric performance of the PEC system. Semiconductor materials tungsten oxide (WO3) and bismuth vanadate (BiVO4) are preferred materials for constructing the photoanode heterojunction structure due to their strong visible light response ability and environmental stability (Chinese Patent Publication Nos.: CN107185522A, CN110042409A). However, the exposure of different crystal planes in the BiVO4 crystal can affect its catalytic activity, and controlling the directional crystal plane growth of the BiVO4 crystal on the photoanode can significantly improve the photoelectric performance. Therefore, developing an efficient and stable photoanode can in-situ generate active chlorine species in a high-chloride salt solution for achieving the + simultaneous and efficient removal of NH4 Summary of the Invention

[0004] The present invention aims to construct an efficient and stable photoanode material applied to the photo-electro-catalytic system, in-situ generate strongly oxidizing active chlorine species in a high-chloride salt solution, and achieve the simultaneous and efficient removal of NH4 + -N and refractory organic compounds, reduce the generation amount of the oxidation product NO3 - -N, and improve the denitrification efficiency and water purification capacity. To achieve the above object, the present invention provides a WO3 / BiVO4-cobalt borate (CoB i ) photoanode, which forms a PEC system with a commercial Pt sheet electrode. The specific preparation steps of the WO3 / BiVO4-CoB i photoanode are as follows:

[0005] Step 1, pretreatment of fluorine-doped SnO2 conductive glass (FTO): Cut FTO with a fixed area, and ultrasonically clean it in ultrapure water, acetone and ethanol in sequence to remove surface impurities, and dry it for standby.

[0006] Step 2, electrodeposition of WO3 loading: Prepare a 25 mmol / L Na2WO4 precursor solution with a pH of 1-3. Using a three-electrode system, use the pretreated FTO, platinum (Pt) sheet and Ag / AgCl electrode as the working electrode, counter electrode and reference electrode respectively, and perform WO3 electrodeposition on the working electrode. After completion, repeatedly wash it with ethanol and ultrapure water, and perform annealing treatment at 400-600 °C for 0.5-2 h to obtain the FTO / WO3 photoanode.

[0007] Step 3, hydrothermal growth of oriented crystal plane BiVO4: First, coat the BiVO4 seed layer. Bi(NO3)3·5H2O and NH4VO3 with a molar ratio of 1:1 - 1:2 are dissolved in 60% HNO3, and 0.05 - 0.2 g / mL of polyvinyl alcohol is continuously added and stirred until the solution becomes transparent. The seed solution is spin-coated on FTO / WO3 and annealed at 400 - 600 °C for 0.5 - 2 h. Then, Bi(NO3)3·5H2O and NH4VO3 with a molar ratio of 1:1 - 1:2 are dissolved in 2 mol / L HNO3, the FTO is immersed, and after adjusting the pH with NH3·H2O, constant temperature stirring is maintained to allow the growth of the precursor. It is transferred for hydrothermal synthesis and annealed at 400 - 600 °C for 3 - 6 h to obtain the FTO / WO3 / BiVO4 photoanode.

[0008] Step 4, photo-assisted electrodeposition of CoB i Co-catalyst: Using 1 mol / L H3BO3 solution (pH adjusted to 8 - 10 with KOH) as the electrolyte, the FTO / WO3 / BiVO4 electrode is electrochemically pretreated, and then 0.1 - 0.8 mmol / L Co(NO3)2·6H2O is added to the above electrolyte, and CoB i electrodeposition is carried out under visible light irradiation to obtain FTO / WO3 / BiVO4-CoB i photoanode.

[0009] Further, in Step 2, the electrodeposition voltage is -0.3 to -0.5 V vs. Ag / AgCl, and the deposition duration is 15 - 40 minutes.

[0010] Further, in Step 3, the solution pH is adjusted to 0.5 - 2.0.

[0011] Further, in Step 3, the hydrothermal synthesis is carried out at 180 - 230 °C for 8 - 12 h.

[0012] Further, in Step 4, the electrochemical pretreatment voltage is -0.7 to -0.9 V vs. Ag / AgCl, and the duration is 100 - 300 s.

[0013] Further, in Step 4, the electrodeposition voltage is 0.3 to 0.6 V vs. Ag / AgCl, and the duration is 20 - 60 s.

[0014] Using WO3 / BiVO4-CoB i as the photoanode, a commercial Pt sheet as the cathode, and high-chloride wastewater as the electrolyte, the device and specific steps for the synchronous treatment of NH4 + -N and refractory organic compounds are as follows: Wastewater treatment is carried out in a single-chamber open reactor. The side of the FTO-loaded material of the photoanode faces upward and is fixed 1 - 2 cm below the solution surface with an L-shaped electrode clamp. The commercial Pt sheet electrode (2×2 cm2 ) It is arranged at the bottom of the reactor parallel to the liquid surface as the cathode, opposite to the photoanode, and the Ag / AgCl electrode is vertically inserted into the solution as the reference electrode. The xenon lamp visible light source irradiates the photoanode vertically from above the solution, keeping the light intensity at the photoanode about 100 mW / cm 2 . The liquid to be treated is injected into the reactor as the electrolyte, and the electrochemical workstation serves as the power supply to provide the working voltage required for the reaction system, and the treatment reaction is started.

[0015] Basic principle of the present invention: FTO / WO3 / BiVO4-CoB i The excellent optoelectronic properties of the photoanode are mainly due to (1) the octahedral BiVO4 array grown on the oriented crystal plane and the WO3 / BiVO4 heterojunction effectively inhibit the recombination of photo-generated electrons and holes through a two-step charge separation mechanism, (2) the cocatalyst CoB i reduces the charge transfer resistance at the photoanode / solution interface, and (3) the cocatalyst CoB i improves the conversion rate of photo-generated holes to redox equivalent substances. Therefore, the PEC system composed of this photoanode can effectively oxidize Cl in the perchlorate wastewater - , in-situ generate strongly oxidizing active chlorine species, control the oxidation direction of NH4 + -N, reduce the generation of the oxidation product NO3 - -N, improve the denitrification efficiency, and at the same time obtain a high-efficiency ability to remove refractory organic matter.

[0016] Beneficial effects of the present invention are:

[0017] (1) The FTO / WO3 / BiVO4-CoB i photoanode prepared in the present invention has optimized the structure from multiple angles of the effective separation of photo-generated electrons and holes, the charge transfer resistance at the photoanode / solution interface, and the conversion rate of photo-generated holes to redox equivalent substances, greatly improving the carrier transfer efficiency and optoelectronic properties of the photoanode.

[0018] (2) The FTO / WO3 / BiVO4-CoB i photoanode prepared in the present invention can in-situ utilize Cl in the perchlorate wastewater - to generate strongly oxidizing active chlorine species, reduce the generation of the oxidation product NO3 - -N, and improve the denitrification efficiency.

[0019] (3) The PEC system of the photoanode prepared in the present invention realizes the synchronous removal of NH4 + -N and refractory organic matter in the wastewater, and at the same time has the advantages of high efficiency and stability. Description of the drawings

[0020] Figure 1For the FTO / WO3 / BiVO4 and FTO / WO3 / BiVO4-CoB of the present invention i Scanning electron microscope morphology diagrams of the photoanodes. a, b) SEM images of the surface morphology of FTO / WO3 / BiVO4; c) SEM image of the cross-sectional morphology of FTO / WO3 / BiVO4; d, e) i SEM images of the surface morphology of FTO / WO3 / BiVO4-CoB; f) i SEM image of the cross-sectional morphology of FTO / WO3 / BiVO4-CoB.

[0021] Figure 2 For the FTO / WO3, FTO / WO3 / BiVO4 and FTO / WO3 / BiVO4-CoB of the present invention i Material structure and surface morphology characterization diagrams of the photoanodes. a) XRD characterization diagram; b) Co 2p XPS spectrum diagram.

[0022] Figure 3 For the FTO / WO3, FTO / WO3 / BiVO4 and FTO / WO3 / BiVO4-CoB of the present invention i Photoelectrochemical performance test results of the photoanodes. a) Electrochemical impedance EIS test diagram under visible light illumination; b) Transient photocurrent response intensity test; c) Steady-state J-V curve test.

[0023] Figure 4 For the treatment device schematic diagram of NH4 + -N and refractory organic matters in the high-chloride salt wastewater by the PEC system of the photoanodes of the present invention.

[0024] Figure 5 For the FTO / WO3, FTO / WO3 / BiVO4 and FTO / WO3 / BiVO4-CoB of the present invention i Efficiency results of the PEC system of the photoanodes for synchronously treating NH4 + -N and carbamazepine. a) Degradation efficiency of carbamazepine; b) NH4 + -N removal rate and NO3 - -N generation amount.

[0025] Figure 6 For the FTO / WO3 / BiVO4-CoB of the present invention i Efficiency differences of the PEC system of the photoanodes for synchronously treating NH4 - under different Cl + conditions and carbamazepine. a) NH4 + -N removal rate; b) Degradation efficiency of carbamazepine.

[0026] Figure 7 For the FTO / WO3 / BiVO4-CoB of the present inventioni The efficiency differences of the PEC system of the photoanode for synchronously treating NH4 + -N and carbamazepine under different applied voltage conditions. a) NH4 + -N removal rate; b) Carbamazepine degradation efficiency.

[0027] Figure 8 For the FTO / WO3 / BiVO4-CoB of the present invention i The PEC system of the photoanode synchronously treats NH4 + -N and the cyclic effect test of carbamazepine. Specific implementation mode

[0028] The technical solution of the present invention will be further described below in conjunction with the drawings and embodiments.

[0029] Example 1:

[0030] In this example, the preparation method of the FTO / WO3 / BiVO4-CoB i photoanode includes the following steps:

[0031] (1) Pretreatment of FTO conductive glass: Cut out a rectangular FTO conductive glass with a fixed area, ultrasonically clean it in ultrapure water, acetone and ethanol for 10 min in sequence to remove surface impurities, and then dry it for standby.

[0032] (2) Electrodeposition of WO3 loading: First, prepare the WO3 electrodeposition precursor solution. The precursor solution needs to be prepared on the same day. Add 0.01 - 0.1 mol / L 30% H2O2 dropwise to the 25 mmol / L Na2WO4 solution, and gradually add concentrated HNO3 to adjust the pH of the precursor solution to 1 - 3. Then, use a three-electrode system to electrodeposit WO3 on the conductive side of the FTO. Use the pretreated FTO, Pt sheet and Ag / AgCl electrode as the working electrode, counter electrode and reference electrode respectively. Use an electrochemical workstation as the power source, and perform electrodeposition on the working electrode at a voltage of -0.3 to -0.5 V vs. Ag / AgCl for 15 - 40 minutes. After that, soak and wash it with ethanol and ultrapure water for multiple times, and then transfer the deposited layer upwards to a muffle furnace, and carry out annealing treatment at 400 - 600 °C for 0.5 - 2 h at a heating rate of 1 - 5 °C / min to obtain the FTO / WO3 photoanode.

[0033] (3) In-situ growth of oriented crystal plane BiVO4 by hydrothermal method: First, a BiVO4 seed layer is coated on FTO / WO3. Bi(NO3)3·5H2O and NH4VO3 with a molar ratio of 1:1 - 1:2 are dissolved in 60% HNO3, and then 0.05 - 0.2 g / mL of polyvinyl alcohol is added and stirred overnight until the solution becomes transparent. The seed solution is spin-coated on FTO / WO3, and the coated side is transferred upward to a muffle furnace and annealed at 400 - 600 °C for 0.5 - 2 h with a heating rate of 1 - 5 °C / min. Then, a precursor solution for BiVO4 crystal growth is prepared. Bi(NO3)3·5H2O and NH4VO3 with a molar ratio of 1:1 - 1:2 are dissolved in 2 mol / L HNO3, and constant-temperature water bath stirring is maintained. The FTO / WO3 material coated with the seed layer is tilted with the material side upward and immersed in the precursor solution. NH3·H2O is dropped in to adjust the pH of the solution to 0.5 - 2.0, and constant-temperature water bath stirring is continued to allow the precursor to grow. Then, the solution is transferred to the inner lining of a polytetrafluoroethylene high-pressure reaction kettle. The FTO conductive side is facing downward and leaning against the tube wall, and hydrothermal synthesis is carried out at 180 - 230 °C for 8 - 12 h. After taking out, it is repeatedly soaked and washed in ultrapure water and ethanol, and finally annealed at 400 - 600 °C for 3 - 6 h with a heating rate of 1 - 5 °C / min to obtain the FTO / WO3 / BiVO4 photoanode.

[0034] (4) Photo-assisted electrodeposition of CoB i Cocatalyst: Prepare a 1 mol / L H3BO3 solution, add solid KOH to adjust the pH value to 8 - 10. Using the above solution as the electrolyte, set the working voltage of -0.7~-0.9V vs. Ag / AgCl, and perform electrochemical pretreatment on the FTO / WO3 / BiVO4 electrode for 100 - 300 s. Then, add 0.5 mmol / L Co(NO3)2·6H2O to the above electrolyte and stir until completely dissolved. Under the visible light irradiation simulated by a xenon lamp, set the working voltage of 0.3~0.6V vs. Ag / AgCl, and perform CoB i electrodeposition for 20 - 60 s to obtain the FTO / WO3 / BiVO4-CoB i photoanode. The difference in the surface morphology of the photoanode before and after loading CoB i is as follows Figure 1 .

[0035] Example 2:

[0036] The FTO / WO3 photoanode involved in the present invention is prepared according to the steps (1) and (2) in Example 1, and the FTO / WO3 / BiVO4 photoanode is prepared according to the steps (1), (2) and (3) in Example 1.

[0037] Example 3:

[0038] The photoanodes prepared in the present invention were characterized by XRD and XPS for their structures ( Figure 2 ). The results showed the successful preparation of WO3 (PDF#32 - 1395) and BiVO4 (PDF#14 - 0688) coatings and the successful loading of the cocatalyst CoB i , and the loading of BiVO4 and CoB i on the electrode surface did not damage the structure of the underlying WO3 crystals.

[0039] Example 4:

[0040] The photoanodes prepared in the present invention were tested for their optoelectronic properties by electrochemical impedance spectroscopy (EIS), transient photocurrent response, and steady-state J-V curves ( Figure 3 ). The EIS results showed that as the load layer of the photoanode was continuously modified, the transfer resistance of the photo-generated carriers gradually decreased and the transfer ability gradually increased. In particular, it was shown that the oriented crystal plane of BiVO4 promoted the accumulation of photo-generated holes on the photoanode surface, and the cocatalyst CoB i reduced the charge transfer resistance at the photoanode / solution surface, ultimately affecting the carrier transfer kinetics and improving the photo-generated carrier transfer ability of the photoanode. The results of the transient photocurrent response and steady-state J-V curves both showed that as the load layer was continuously modified, the photoanode exhibited stronger visible light response ability, higher visible light utilization rate, and carrier transfer ability under the same applied voltage.

[0041] Example 5:

[0042] The photoanode synchronously treated NH4 + -N and refractory organic compounds in the high-chloride salt solution. Using FTO / WO3 / BiVO4-CoB i as the photoanode and a commercial Pt sheet as the cathode to construct a PEC system for treating NH4 + -N and refractory organic compounds in the high-chloride salt wastewater, the reaction device ( Figure 4 ) and the specific steps were as follows: The wastewater was treated in a single-chamber open reactor. The side of the FTO-loaded material of the photoanode faced upward and was fixed 1 - 2 cm below the solution surface with an L-shaped electrode clip. The commercial Pt sheet electrode (2×2 cm 2 ) was used as the cathode and was set parallel to the liquid surface at the bottom of the reactor, opposite to the photoanode. The Ag / AgCl electrode was inserted vertically into the solution as the reference electrode. The xenon lamp visible light source irradiated the photoanode vertically from above the solution, maintaining the light intensity at the photoanode at about 100 mW / cm 2 . The electrochemical workstation was used as the power supply to provide the working voltage required for the reaction system. A solution containing 50 mg / L NH4 +The 0.2 mol / L NaCl solution containing 5 mg / L carbamazepine (CBZ) and -N was used as the electrolyte to be treated. 60 mL was taken and injected into the reactor. A working voltage of 2.0 V vs. Ag / AgCl was applied and the visible light source was turned on to start the treatment system. The results showed ( Figure 5 ), the PEC system with FTO / WO3 / BiVO4-CoB i as the photoanode had excellent synchronous removal efficiency of NH4 + -N and CBZ. The degradation rate of CBZ reached over 99% within 40 min, and the oxidation rate of NH4 + -N reached 75.4% at 120 min. Only about 10% of NH4 + -N was converted to NO3 - -N, and the rest was converted to the product N2.

[0043] Example 6: Effects of system Cl - concentration and applied voltage on the synchronous removal efficiency of NH4 + -N and refractory organics. The Cl - concentration of the solution to be treated was set to 0 - 0.25 mol / L, and the synchronous removal efficiency of the system was investigated. The results showed ( Figure 6 ), the presence of Cl - in the system was a necessary condition for the effective oxidation of NH4 + -N, and it was also beneficial to promote the degradation of organics. This was because the Cl - concentration was one of the decisive factors for the generation amount of active chlorine species in the system, and the content of active chlorine species directly affected the efficiency of the system in oxidizing NH4 + -N and refractory organics. In addition, the system was investigated with an applied voltage of 1.0 - 2.3 V vs. Ag / AgCl. The results showed ( Figure 7 ), the magnitude of the applied voltage was one of the important factors controlling the generation of active chlorine species in the PEC system. A higher system voltage was beneficial to the generation of active chlorine, which in turn promoted the improvement of the synchronous treatment ability of the system. When the Cl - concentration in the system was 0.2 mol / L, the applied voltage of the system was 2.0 V vs. Ag / AgCl, and the initial pH (5.7) of the solution to be treated was not adjusted artificially, the synchronous removal efficiencies of NH4 + -N and CBZ reached 75.4% and 100% respectively after 2 h, and the generation rate of NO3 - -N was effectively controlled within 10% of the oxidation amount of NH4 + -N, and the treatment effect was relatively ideal.

[0044] Example 7: Evaluation of the cyclic effect of the PEC system synchronous treatment ability of the photoanode of the present invention. The cyclic experiment test of the synchronous treatment efficiency of the PEC system was carried out continuously for 10 times. The settings of the treatment device and the solution to be treated were kept consistent with those in Example 5. In addition, the Cl - concentration in the system was 0.2 mol / L, the externally applied voltage of the system was 2.0 V vs. Ag / AgCl, and the initial pH (5.7) of the solution to be treated was not adjusted artificially. The results showed ( Figure 8 ), that after 10 cyclic tests of the PEC system in the present invention, the photoelectrochemical performance only decreased slightly. The CBZ treatment rate reached 97.6% at 40 min, and the NH4 + -N oxidation rate reached 61.1% at 120 min.

[0045] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a photoanode applied to the photoelectrochemical synergistic catalysis for the synchronous treatment of ammonia nitrogen and refractory organic compounds in high-chloride wastewater, characterized in that, On doped fluorine tin oxide conductive glass (FTO), in accordance with the direction of carrier charge flow, tungsten oxide (WO3) is in-situ loaded successively, and then bismuth vanadate (BiVO4) with an oriented crystal plane array having a carrier spatial pre-separation structure is hydrothermally grown, and then cobalt borate salt (CoB i ) co-catalyst is photo-assisted electrodeposited, comprising the following steps: (1) FTO pretreatment: Cut FTO with a fixed area, ultrasonically clean it and dry it for standby; (2) In-situ loading of WO3: Prepare a 25 mmol / L Na2WO4 precursor solution with a pH of 1 - 3, and perform electrodeposition on FTO using a three-electrode system. After completion, repeatedly wash it with ethanol and ultrapure water, and perform annealing treatment at 400 - 600 °C for 0.5 - 2 h to obtain the FTO / WO3 photoanode; (3) Hydrothermal growth of oriented crystal plane BiVO4: First, coat the seed layer. Bi(NO3)3·5H2O and NH4VO3 with a molar ratio of 1:1 - 1:2 are dissolved in 60% HNO3, and 0.05 - 0.2 g / mL of polyvinyl alcohol is continuously added and stirred until the solution is transparent. Spin-coat the seed solution on FTO / WO3 and perform annealing treatment at 400 - 600 °C for 0.5 - 2 h. Then, Bi(NO3)3·5H2O and NH4VO3 with a molar ratio of 1:1 - 1:2 are dissolved in 2 mol / L HNO3, immerse FTO in it, adjust the pH with NH3·H2O and keep stirring at a constant temperature to allow the growth of the precursor, transfer it for hydrothermal synthesis, and perform annealing treatment at 400 - 600 °C for 3 - 5 h to obtain the FTO / WO3 / BiVO4 photoanode; (4) Photo-assisted electrodeposition of CoB i Co-catalyst: Using 1 mol / L H3BO3 solution as the electrolyte, adjusting the pH value to 8 - 10 with KOH, electrochemically pre-treating the FTO / WO3 / BiVO4 electrode, and then adding 0.1 - 0.8 mmol / L Co(NO3)2·6H2O to the above electrolyte. Conduct CoB i electrodeposition under visible light irradiation to obtain FTO / WO3 / BiVO4-CoB i photoanode.

2. The preparation method according to claim 1, wherein In step (2), the electrodeposition voltage is -0.3~-0.5 V vs. Ag / AgCl, and the deposition duration is 15 - 40 minutes.

3. The preparation method according to claim 1, characterized in that, In step (3), adjust the solution pH to 0.5 - 2.0, and the hydrothermal synthesis conditions are 8 - 12 h at 180 - 230 °C.

4. The preparation method according to claim 1, wherein In step (4), the electrochemical pretreatment voltage is -0.7~-0.9 V vs. Ag / AgCl, the duration is 100 - 300 s, the electrodeposition voltage is 0.3~0.6 V vs. Ag / AgCl, and the duration is 20 - 60 s.

5. The preparation method according to claim 1, and the prepared FTO / WO3 / BiVO4-CoB i photoanode is used for the application of photoelectrochemically synergistically catalyzing chloride ions to generate active chlorine species in high-chloride wastewater, and synchronously treating ammonia nitrogen and refractory organic compounds.

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