Rust removal method for metal wire

Abstract

The invention discloses a rust removal method for a metal wire, and relates to the technical field of metal wire processing, and the rust removal method for the metal wire comprises the following steps: putting the metal wire to be treated and a composite treatment liquid into a catalytic reaction tank, immersing the metal wire into the composite treatment liquid, and carrying out derusting treatment at the temperature in the tank of 25-40 DEG C for 1-2 hours; and controlling the catalytic reaction tank to excite visible light so as to perform rust removal treatment on the metal wire. Wherein the composite treating fluid is prepared from the following components in percentage by weight: 10 to 15 percent of citric acid, 1 to 3 percent of bismuth vanadate / ferric oxide heterojunction photocatalyst and 5 to 8 percent of diammonium hydrogen phosphate. The technical problem that waste discharge cannot be reduced while the rust removal efficiency of the metal wire is improved can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of metal wire processing, and in particular to a method for removing rust from metal wire. Background Art

[0002] At present, citric acid is usually used to remove rust from metal wires. 3+ The reaction forms a soluble iron citrate complex, which removes the rust layer.

[0003] Due to Fe 3+ The coordination ability of citric acid is weak, and the reaction rate with citric acid at room temperature is low, resulting in slow rust removal. In order to improve the rust removal efficiency, it is usually necessary to carry out the process under high temperature conditions; however, under high temperature conditions (such as greater than 80°C), citric acid will undergo thermal decomposition to generate small molecular organic acids (such as acetone dicarboxylic acid, oxalic acid), etc. These substances have a high chemical oxygen demand (COD), which increases the difficulty and cost of wastewater treatment.

[0004] Therefore, the related art cannot improve the rust removal efficiency of metal wires while reducing waste emissions. Summary of the Invention

[0005] The main purpose of this application is to provide a method for rust removal of metal wires, aiming to solve the technical problem of being unable to reduce waste emissions while improving the rust removal efficiency of metal wires.

[0006] To achieve the above objectives, the present application proposes a method for removing rust from a metal wire, the method comprising:

[0007] Placing a metal wire to be treated and a composite treatment solution into a catalytic reaction tank, immersing the metal wire in the composite treatment solution, wherein the composite treatment solution comprises, by percentage, 10-15% citric acid, 1-3% bismuth vanadate / iron oxide heterojunction photocatalyst, and 5-8% diammonium hydrogen phosphate;

[0008] At a tank temperature of 25-40° C., the catalytic reaction tank is controlled to excite visible light to perform rust removal treatment on the metal wire.

[0009] In one embodiment, the bismuth vanadate / iron oxide heterojunction photocatalyst is doped with 0.5-1% tungsten.

[0010] In one embodiment, the catalytic reaction tank is provided with an LED light source, the wavelength of the selected LED light source is the same as the maximum absorption wavelength of the bismuth vanadate material, and the intensity of the visible light is greater than or equal to 1000 μW / cm 2 .

[0011] In one embodiment, the body of the catalytic reaction tank is made of borosilicate glass, and the inner wall of the catalytic reaction tank is covered with a reflective aluminum film.

[0012] In one embodiment, the surface of the bismuth vanadate is coated with a TiO2 protective layer.

[0013] In one embodiment, an electrode system is further provided in the catalytic reaction tank, wherein the cathode of the electrode system is provided on the side where the metal wire is placed, and the electrode system is electrically connected to an external asymmetric pulse power supply;

[0014] The step of controlling the catalytic reaction tank to excite visible light comprises:

[0015] The catalytic reaction tank is controlled to excite visible light, and after a preset time, the asymmetric pulse power supply is controlled to operate based on preset electric field parameters to synchronously apply the electric field during the photocatalytic process until a preset stop condition is reached, the asymmetric pulse power supply is turned off and the excitation of visible light is stopped.

[0016] In one embodiment, the preset electric field parameters include an anode voltage of 3-5 V / 100 ms, a cathode voltage of 2-3 V / 50 ms, and a frequency of 8-10 Hz.

[0017] In one embodiment, after the preset stop condition is reached, a Fe3(PO4)2 film is deposited on the surface of the metal wire, and the thickness of the Fe3(PO4)2 film is 5-10 μm.

[0018] In one embodiment, the pH of the composite treatment solution is 3-4.

[0019] In one embodiment, when the asymmetric pulse power supply is controlled to operate, a preset amount of H2O2 and a Cu2O2 having a concentration of 0.1 mmol / L are added to the composite treatment solution. 2+ ; wherein the preset amount is adjusted according to the COD value in the composite treatment liquid.

[0020] One or more technical solutions proposed in this application have at least the following technical effects:

[0021] The present invention involves placing a metal wire to be treated and a composite treatment solution into a catalytic reaction tank, immersing the metal wire in the composite treatment solution, and controlling the catalytic reaction tank to excite visible light at a tank temperature of 25-40°C to perform a rust removal treatment on the metal wire. The composite treatment solution comprises, by percentage, 10-15% citric acid, 1-3% bismuth vanadate / iron oxide heterojunction photocatalyst, and 5-8% diammonium hydrogen phosphate.

[0022] Specifically, the bismuth vanadate / iron oxide heterojunction photocatalyst is a composite material composed of two semiconductor materials (bismuth vanadate and iron oxide). The material properties of bismuth vanadate and iron oxide are used to enhance the photocatalytic activity, especially the absorption and conversion efficiency in the visible light region. Combining bismuth vanadate and iron oxide to form a heterojunction can effectively promote charge separation and inhibit the recombination of electron-hole pairs, thereby improving the overall photocatalytic performance. When the catalytic reaction tank is controlled to excite visible light, electron-hole pairs are generated under visible light irradiation, and the photogenerated electrons can convert Fe 3+ Reduction to Fe 2+ , and Fe 2+ Fe 3+ It is easier to form a stable complex with citric acid, thereby significantly improving the rate of the rust removal reaction; in addition, the bismuth vanadate / iron oxide heterojunction photocatalyst can also directly activate citric acid molecules, enhance the complexing ability of citric acid with iron ions, and further promote the dissolution of the rust layer.

[0023] At the same time, by adding diammonium hydrogen phosphate as a buffer, the pH of the composite treatment solution can be adjusted, the effective activity range of citric acid can be maintained, and the decomposition of citric acid caused by excessive acidity or alkalinity can be prevented, thereby reducing the generation of by-products.

[0024] Moreover, the above reaction process of the present application only needs to be carried out under low temperature conditions of 25-40°C without heating, which fundamentally avoids the problem of thermal decomposition of citric acid caused by high temperature, thereby greatly reducing the generation of high COD organic matter in the waste liquid.

[0025] Therefore, the above method of the present application can improve the rust removal efficiency of metal wires while reducing waste emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 A schematic diagram of a scenario provided for an embodiment of the method for removing rust from a metal wire of the present application.

[0029] The purpose, features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0030] It should be understood that the specific embodiments described herein are merely used to explain the technical solutions of the present application and are not intended to limit the present application.

[0031] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0032] At present, citric acid is usually used to remove rust from metal wires. 3+ The reaction forms a soluble iron citrate complex, which removes the rust layer.

[0033] Due to Fe 3+ The coordination ability of citric acid is weak, and the reaction rate with citric acid at room temperature is low, resulting in slow rust removal. In order to improve the rust removal efficiency, it is usually necessary to carry out the process under high temperature conditions; however, under high temperature conditions (such as greater than 80°C), citric acid will undergo thermal decomposition to generate small molecular organic acids (such as acetone dicarboxylic acid, oxalic acid), etc. These substances have a high chemical oxygen demand (COD), which increases the difficulty and cost of wastewater treatment.

[0034] Therefore, the related art cannot improve the rust removal efficiency of metal wires while reducing waste emissions.

[0035] In order to solve the above technical problems, a method for removing rust from a metal wire is proposed. Specifically, referring to Example 1, the method for removing rust from a metal wire includes steps S10 to S20:

[0036] Step S10, placing the metal wire to be treated and the composite treatment solution into a catalytic reaction tank, immersing the metal wire in the composite treatment solution, wherein the composite treatment solution comprises, by percentage, 10-15% citric acid, 1-3% bismuth vanadate / iron oxide heterojunction photocatalyst, and 5-8% diammonium hydrogen phosphate;

[0037] Step S20 , controlling the catalytic reaction tank to excite visible light at a tank temperature of 25-40° C. to perform rust removal treatment on the metal wire.

[0038] In one embodiment, a composite treatment solution can be prepared according to the following ratio: 12% citric acid, 2% bismuth vanadate / iron oxide heterojunction photocatalyst, and 6% diammonium phosphate are added to a corrosion-resistant stirring container, with the remainder being deionized water. The mixture is stirred at 300 rpm for 30 minutes to thoroughly mix the components, thereby obtaining a composite treatment solution.

[0039] Furthermore, the prepared composite treatment liquid is poured into a catalytic reaction tank equipped with a visible light source that can evenly illuminate the surface of the treatment liquid, clean the surface of the metal wire to be treated, remove obvious dust and grease, and ensure that it can fully contact the composite treatment liquid. The pretreated metal wire is immersed in the catalytic reaction tank filled with the composite treatment liquid, the temperature in the catalytic reaction tank is controlled to be maintained between 25-40°C, and the visible light excitation system is turned on to excite visible light for 8-15 minutes, preferably the temperature in the catalytic reaction tank is controlled to be maintained between 30°C, and the visible light excitation system is turned on to excite visible light for 10 minutes.

[0040] In the above process, since the components of the composite treatment liquid include 10-15% citric acid, 1-3% bismuth vanadate / iron oxide heterojunction photocatalyst, 5-8% diammonium hydrogen phosphate and deionized water, and the bismuth vanadate / iron oxide heterojunction photocatalyst is a composite material composed of two semiconductor materials (bismuth vanadate and iron oxide), the material properties of bismuth vanadate and iron oxide are utilized to enhance the photocatalytic activity, especially the absorption and conversion efficiency in the visible light region. The bismuth vanadate and iron oxide are combined to form a heterojunction, which can effectively promote charge separation and inhibit the recombination of electron-hole pairs, thereby improving the overall photocatalytic performance.

[0041] When the catalytic reaction tank is irradiated by visible light, the bismuth vanadate / iron oxide heterojunction photocatalyst absorbs photon energy and generates electron-hole pairs. The photon energy causes the valence band electrons in bismuth vanadate and iron oxide to jump to the conduction band, forming free-moving electrons (e - ), while leaving holes (h + ); photogenerated electrons (e - ) can migrate to the surface of the metal wire and convert the Fe 3+ Reduction to Fe 2+ , and Fe 2+ Fe 3+ It is easier to form a stable complex with citric acid, thereby significantly improving the rate of rust removal reaction. + ) can oxidize other substances in water or composite treatment liquid to generate active oxygen species such as hydroxyl radicals. These active oxygen species help to activate citric acid molecules, enhance the coordination ability of citric acid molecules with iron ions, and further promote the reaction between citric acid and Fe 2+ , citric acid and Fe 3+ The complex reaction forms a soluble iron citrate complex, thereby dissolving the rust layer.

[0042] It should be noted that in the photocatalytic process, iron oxide mainly plays the role of promoting charge separation and improving the utilization rate of light energy, and does not directly participate in chemical reactions that may lead to further oxidation of itself.

[0043] Optionally, refer to Figure 1 The catalytic reaction tank is provided with an LED light source, the wavelength of the selected LED light source is the same as the maximum absorption wavelength of the bismuth vanadate material, and the intensity of the visible light is greater than or equal to 1000 μW / cm 2 .

[0044] Since the band gap width of bismuth vanadate is approximately 2.4eV, the corresponding light absorption edge is approximately 520nm. In order to maximize the excitation of electron transitions in bismuth vanadate and generate more photogenerated electron-hole pairs, the wavelength of the selected LED light source is the same as the maximum absorption wavelength of the bismuth vanadate material (BiVO4 material) (i.e., the preferred LED light source wavelength is 520nm). If ordinary white light or a light source with a mismatched wavelength is used, the light energy utilization rate will be low, which will affect the overall photocatalytic efficiency.

[0045] Furthermore, the light intensity is greater than or equal to 1000 μW / cm 2 Only visible light can excite a sufficient number of electron-hole pairs to meet the redox capacity required for the rust removal reaction, ensuring that a high reaction kinetic rate can be maintained even at a lower temperature (25-40°C); the light intensity of visible light greater than or equal to 1000μW / cm can be achieved through multiple sets of LED arrays. 2 , thereby ensuring that each point in the treatment liquid can be fully irradiated to avoid insufficient local reaction.

[0046] Optionally, the body of the catalytic reaction tank is made of borosilicate glass, and the inner wall of the catalytic reaction tank is covered with a reflective aluminum film.

[0047] Because borosilicate glass has excellent visible light transmittance (typically above 90%) and exhibits virtually no absorption or scattering of light within the 500-600nm wavelength range (e.g., BiVO4's peak absorption band), it ensures that visible light emitted by the LED light source can penetrate the walls of the catalytic reaction tank to the greatest extent possible and enter the composite treatment solution, effectively stimulating the photocatalyst. Furthermore, borosilicate glass exhibits excellent chemical stability and resistance to corrosion from acidic and alkaline solutions, making it suitable for long-term, reusable industrial rust removal systems.

[0048] Furthermore, by coating the inner wall of the catalytic reaction tank with a layer of high-reflectivity aluminum film, the light that would otherwise be lost due to scattering or penetrating the tank wall can be reflected back into the composite treatment liquid, thereby increasing the effective utilization density of photons per unit volume and thereby enhancing the excitation efficiency of the photocatalyst.

[0049] In addition, diammonium hydrogen phosphate, as a buffer, can regulate the pH of the composite treatment solution, maintain the effective activity range of citric acid, and prevent the decomposition of citric acid caused by excessive acidity or alkalinity, thereby reducing the formation of by-products.3- ) will also form a protective film on the metal surface, which will play a certain role in corrosion inhibition and prevent the uncorroded metal parts from being excessively corroded.

[0050] Optionally, the bismuth vanadate / iron oxide heterojunction photocatalyst is doped with 0.5-1% tungsten.

[0051] Tungsten (W 6+ ) doping can change the electronic structure of bismuth vanadate, narrow the band gap width of bismuth vanadate, and enable bismuth vanadate to absorb photons in a wider wavelength range, especially increasing the utilization efficiency of the visible light portion, thereby enhancing its absorption capacity for visible light. In addition, tungsten doping can also provide additional free electrons, thereby accelerating the conductivity of electrons within the bismuth vanadate / iron oxide heterojunction photocatalyst and promoting the rapid transfer of charges. It can also effectively suppress the deactivation phenomenon that may occur in the bismuth vanadate / iron oxide heterojunction photocatalyst during long-term use, such as photocorrosion or structural changes, thereby enhancing the overall stability and service life of the bismuth vanadate / iron oxide heterojunction photocatalyst.

[0052] Optionally, the surface of the bismuth vanadate is coated with a TiO2 protective layer.

[0053] Although bismuth vanadate has good visible light response ability, it is prone to photocorrosion under long-term illumination. That is, photogenerated holes will oxidize the bismuth vanadate itself, causing its structural damage or performance degradation. Therefore, by forming a nano-scale TiO2 coating layer on the surface of bismuth vanadate, the bismuth vanadate can be effectively isolated from direct contact with the composite treatment solution, preventing it from being oxidized and degraded by photogenerated holes.

[0054] It should be noted that the above-mentioned metal material can be iron, iron alloy, etc.

[0055] The above method can achieve efficient metal wire rust removal at relatively low temperatures (25-40 ° C) without heating, fundamentally avoiding the problem of thermal decomposition of citric acid caused by high temperature, thereby significantly reducing the generation of high COD organic matter in the waste liquid. Therefore, the present application utilizes photocatalytic technology to enhance the reaction activity between citric acid and iron ions, combined with the buffering and corrosion inhibition of diammonium hydrogen phosphate, to improve the efficiency of metal wire rust removal while reducing waste emissions, that is, to provide a high-efficiency, low-consumption, and environmentally friendly metal wire rust removal solution.

[0056] Example 2

[0057] Although the above solution can significantly reduce waste emissions, it still cannot completely avoid the decomposition of citric acid molecules. In order to solve this technical problem, based on the above technical solution, the catalytic reaction tank is further provided with an electrode system, the cathode of the electrode system is located on the side where the metal wire is placed, and the electrode system is electrically connected to an external asymmetric pulse power supply; the specific implementation method of controlling the catalytic reaction tank to excite visible light can be:

[0058] The catalytic reaction tank is controlled to excite visible light, and after a preset time, the asymmetric pulse power supply is controlled to operate based on preset electric field parameters to synchronously apply the electric field during the photocatalytic process until a preset stop condition is reached, the asymmetric pulse power supply is turned off and the excitation of visible light is stopped.

[0059] Specifically, an electrode system (including a cathode and an anode) can be set in the catalytic reaction tank, the cathode can be set on the side where the metal wire is placed, and the anode can be set on the side away from the metal wire. Figure 1 ; The electrode material can be made of inert materials (such as titanium-based coating electrodes (Ti / IrO2 5 -Ta2O5) to prevent oxidation and corrosion of the electrodes themselves. The electrode system is connected to an external asymmetric pulse power supply. The asymmetric pulse power supply is used to output current waveforms with different positive and negative pulse widths and amplitudes, making it easier to adjust the direction and intensity of the electric field and enhance ion migration control capabilities.

[0060] Furthermore, the catalytic reaction tank is controlled to excite visible light (i.e., the LED power supply is turned on), and the bismuth vanadate / iron oxide heterojunction photocatalyst is used to absorb visible light, excite electron-hole pairs, and start the rust removal reaction. After a preset time, the asymmetric pulse power supply is turned on to introduce an electric field to enhance the ion migration and charge separation efficiency. After reaching the preset stop condition (a certain time is reached or the rust on the surface of the metal wire is completely removed), the power supply and light source are turned off to complete the rust removal operation.

[0061] It can be understood that after the external electric field is introduced, a local high electron concentration area can be formed in the cathode region, further promoting the Fe 3+ The reduction reaction can improve the rust removal efficiency; and under the action of asymmetric pulse power supply, weak electrolysis of water can be achieved by controlling the pulse parameters, and OH can be generated locally. - or H + , assisting in adjusting the pH value of the metal surface, which is more conducive to the stable existence and complexation of citric acid.

[0062] At the same time, in order to recycle the citric acid in the composite treatment solution, the preset electric field parameters include an anode voltage of 3-5V / 100ms, a cathode voltage of 2-3V / 50ms, and a frequency of 8-10Hz.

[0063] The overall solution is electrically neutral by applying a short high voltage at the anode (4V / 100ms) and a low voltage at the cathode (2V / 50ms). 3+ Rapid reduction to Fe 2+ , thereby releasing Fe 3+ The coordinated citric acid molecules (i.e., the already formed iron citrate complex can be dissociated to a certain extent, allowing the citric acid to return to a free state). By intermittently applying positive and negative pulses (at a frequency of 9 Hz), it is ensured that there is sufficient time to complete the electrochemical reaction within each cycle, while avoiding electrode polarization, reducing side reactions, and protecting the citric acid from being destroyed. The pulsed electric field can also improve the mass transfer efficiency of ions in the solution, allowing the generated free citric acid to quickly diffuse from the metal surface into the main body of the solution, preventing it from aggregating on the metal surface to form new complexes or precipitation.

[0064] It should be noted that after the preset stop condition is reached, a Fe3(PO4)2 film is deposited on the surface of the metal wire. Specifically, since the composite treatment solution contains diammonium hydrogen phosphate, diammonium hydrogen phosphate dissociates into HPO4 in the solution. 2- ions, and at the same time, the cathode reduction reaction converts Fe 2+ Reduction and precipitation form Fe3(PO4)2 film; if the film layer of Fe3(PO4)2 film is too thick or unevenly distributed, it may affect the subsequent phosphating film forming process, specifically affecting the direct contact between the phosphating solution and the metal substrate.

[0065] In order to solve this technical problem, the asymmetric pulse power supply is controlled based on the above-mentioned preset electric field parameters (anode voltage 3-5V / 100ms, cathode voltage 2-3V / 50ms, frequency 8-10Hz), so that the thickness of the Fe3(PO4)2 film is 5-10μm (when the preset electric field parameters are anode voltage 4V / 100ms, cathode voltage 2V / 50ms, frequency 9Hz, the thickness of the Fe3(PO4)2 film is 6μm). The Fe3(PO4)2 film is not easy to react with moisture and oxygen in the environment, thereby effectively preventing further oxidation and corrosion of the metal wire after pickling.

[0066] Moreover, the Fe3(PO4)2 film with a thickness of 5-10μm can be used as a substrate in the phosphating process. The Fe3(PO4)2 film has good compatibility and chemical affinity with the components in the phosphating solution, which helps to guide the phosphating reaction to proceed more evenly and avoid uneven phosphating caused by inconsistent surface conditions in local areas. At the same time, the pre-deposited Fe3(PO4)2 film can form a good interface bond with the surface of the metal wire and the subsequently formed phosphating layer, thereby improving the adhesion of the entire coating system; it is beneficial to the subsequent phosphating process.

[0067] In addition, during the rust removal process, citric acid may be partially hydrolyzed or photocatalytically decomposed into small molecular organic acids (such as oxalic acid, acetone dicarboxylic acid, etc.), resulting in an increase in COD. In order to solve this technical problem, a preset amount of H2O2 and a concentration of 0.1mmol / L of Cu2O2 can be added to the composite treatment solution while controlling the operation of the asymmetric pulse power supply. 2+ ; wherein the preset amount is adjusted according to the COD value in the composite treatment liquid.

[0068] Specifically, by adding a preset amount of H2O2, hydroxyl radicals can be generated under the induction of visible light or electric field. Hydroxyl radicals can completely oxidize these small molecular organic acids into CO2 and H2O, thereby more efficiently degrading organic pollutants and reducing the COD value of the waste liquid.

[0069] The preset amount may be adjusted according to the measured COD value in the composite treatment liquid. Specifically, the preset amount may be equal to the ratio of the measured COD value to a preset coefficient, wherein the preset coefficient may be 1.2-1.5.

[0070] Cu 2+ As a catalyst, it can promote the decomposition of H2O2 to generate hydroxyl radicals. 2+ It can effectively catalyze the decomposition of H2O2 to generate hydroxyl radicals without causing side reactions or producing excessive copper ion precipitation.

[0071] In actual operation, the COD value of the composite treatment liquid is monitored online to dynamically adjust the H2O2 and Cu 2+ The amount of citric acid added is sufficient to ensure that the oxidation reaction does not consume excessive amounts of citric acid while being able to remove organic pollutants.

[0072] At the same time, the best complexing ability of citric acid appears in a weakly acidic environment (pH = 3-4), at which time most of the citric acid is in an intermediate dissociation state and has a strong coordination ability. If the pH is too high (such as greater than 5), Fe 3+ It will quickly hydrolyze to form Fe(OH)3 precipitate, blocking the complexation channel and affecting the rust removal efficiency. At the same time, it can promote the selective deposition of Fe3(PO4)2.

[0073] Specifically, an electrochemical sensor can be used to detect the oxygen concentration in the solution, thereby indirectly measuring the COD value.

[0074] Based on the above, through photocatalysis, electric field assistance, Cu 2+The synergistic effect of H2O2 oxidation significantly improves the rust removal efficiency, reduces the decomposition of citric acid and the generation of COD, and achieves efficient rust removal at room temperature. At the same time, it can generate a 5-10μm Fe3(PO4)2 film in situ on the metal surface, enhance corrosion resistance and optimize subsequent phosphating processes, achieving environmental protection, energy saving, and resource recycling.

[0075] It should be noted that the above examples are only used to understand the present application and do not constitute a limitation on the rust removal method for metal wires of the present application. Simple transformations in more forms based on this technical concept are all within the scope of protection of the present application.

Claims

1. A method for removing rust from a metal wire, characterized in that: The method includes: Placing a metal wire to be treated and a composite treatment solution into a catalytic reaction tank, immersing the metal wire in the composite treatment solution, wherein the composite treatment solution comprises, by percentage, 10-15% citric acid, 1-3% bismuth vanadate / iron oxide heterojunction photocatalyst, and 5-8% diammonium hydrogen phosphate; At a tank temperature of 25-40° C., the catalytic reaction tank is controlled to excite visible light to perform rust removal treatment on the metal wire.

2. The method according to claim 1, wherein The bismuth vanadate / iron oxide heterojunction photocatalyst is doped with 0.5-1% tungsten.

3. The method according to claim 1, wherein The catalytic reaction tank is provided with an LED light source, the wavelength of the selected LED light source is the same as the maximum absorption wavelength of the bismuth vanadate material, and the intensity of the visible light is greater than or equal to 1000 μW / cm 2 .

4. The method according to claim 1, wherein The catalytic reaction tank is made of borosilicate glass, and the inner wall of the catalytic reaction tank is covered with a reflective aluminum film.

5. The method according to claim 1, wherein The surface of the bismuth vanadate is coated with a TiO2 protective layer.

6. The method according to claim 1, wherein An electrode system is also provided in the catalytic reaction tank, wherein the cathode of the electrode system is provided on the side where the metal wire is placed, and the electrode system is electrically connected to an external asymmetric pulse power supply; The step of controlling the catalytic reaction tank to excite visible light comprises: The catalytic reaction tank is controlled to excite visible light, and after a preset time, the asymmetric pulse power supply is controlled to operate based on preset electric field parameters to synchronously apply the electric field during the photocatalytic process until a preset stop condition is reached, the asymmetric pulse power supply is turned off and the excitation of visible light is stopped.

7. The method according to claim 5, wherein The preset electric field parameters include an anode voltage of 3-5 V / 100 ms, a cathode voltage of 2-3 V / 50 ms, and a frequency of 8-10 Hz.

8. The method according to claim 5, wherein After the preset stop condition is reached, a Fe3(PO4)2 film is deposited on the surface of the metal wire, and the thickness of the Fe3(PO4)2 film is 5-10 μm.

9. The method according to claim 5, wherein The pH of the composite treatment liquid is 3-4.

10. The method according to claim 5, wherein When the asymmetric pulse power supply is controlled to operate, a preset amount of H2O2 and a concentration of 0.1 mmol / L of Cu are added to the composite treatment solution. 2+ ; wherein the preset amount is adjusted according to the COD value in the composite treatment liquid.

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