Electrocatalytic electrode, preparation method thereof and dye wastewater treatment method

Abstract

The invention discloses an electro-catalysis electrode which is used for purifying dye wastewater and comprises a metal substrate, and a SnO2-Sb2O4-La composite material layer is attached to the metal substrate; the technical problems that in the prior art, an electrode material adopted by an electrochemical oxidation method is prone to passivation, low in current efficiency, high in processing energy consumption and the like, and then the electrocatalytic activity is weak, and the service life of an electrode is short are solved. Compared with an electro-catalysis electrode not doped with La, the catalytic electrode attached with the SnO2-Sb2O4-La composite material layer disclosed by the invention can increase the effective contact area with dye wastewater, increase the active sites on the surface of the electrode active layer, accelerate the electron transfer rate between the surface of the electrode active layer and the interface of the dye wastewater, and improve the catalytic activity of the dye wastewater. Compared with the prior art, the preparation method has the advantages that the electro-catalytic activity of the electrode is improved, the degradation efficiency of dye wastewater is improved, in addition, the doping of La can effectively prevent the dye wastewater from immersing into the coating to be in contact with the substrate, the falling of the SnO2-Sb2O4-La composite material layer deposited on the surface of the substrate due to passivation of the substrate is prevented, and the service life of the electrode is prolonged.

Description

Technical Field

[0001] The invention relates to the field of dye wastewater treatment, and in particular to an electrocatalytic electrode and a preparation method thereof, and a dye wastewater treatment method. Background Art

[0002] With the rapid development of industrialization, dyes are often used as colorants, photosensitizers, water tracers, fluorescent markers for microstructure analysis, and biological stains in biomedical research in the textile, paper, plastic, printing, biomedical and leather industries. As a result, a large amount of dye wastewater is discharged, posing a serious threat to the ecological environment. In addition, some dyes are mutagenic and carcinogenic in nature. If ingested, they will have a serious impact on the development, central nervous system and other organs (including liver, kidney, etc.) of humans or animals.

[0003] In the treatment process of dye wastewater, adsorption method, Fenton method, electrochemical oxidation method, etc. are often used. Among them, electrochemical oxidation technology (EOT) is a technology that uses free radicals (such as hydroxyl and hydrogen peroxide hydroxyl radicals) generated during the electrolysis process as oxidants to degrade pollutants.

[0004] One of the main processes of electrochemical oxidation technology (EOT) is to remove or decompose substances through direct reactions on electrodes. Another process is to remove pollutants through strong oxidants such as hydroxyl radicals (·OH) produced during the electrolysis process. Compared with other treatment technologies, this technology is simple to operate in practical applications, and has efficient and rapid treatment, especially in the treatment of wastewater containing difficult-to-biodegrade or toxic substances, showing excellent degradation effects.

[0005] In the prior art, the electrode materials used in the electrochemical oxidation method have disadvantages such as easy passivation, low current efficiency, and high processing energy consumption, which in turn cause problems such as weak electrocatalytic activity and short electrode service life. Therefore, the improvement of catalytic electrode materials is an important development direction of electrochemical oxidation. Summary of the invention

[0006] The purpose of the present invention is to provide an electrocatalytic electrode and a preparation method thereof, and a dye wastewater treatment method, so as to solve the technical problems in the prior art that the electrode materials used in the electrochemical oxidation method are easy to passivate, have low current efficiency, and high processing energy consumption, thereby resulting in weak electrocatalytic activity and short service life of the electrode.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention discloses an electrocatalytic electrode for purifying dye wastewater, comprising a metal substrate, to which a SnO2-Sb2O4-La composite material layer is attached, wherein the SnO2-Sb2O4-La composite material layer has a thickness of 0.2 to 0.8 mm.

[0009] Compared with the electrocatalytic electrode without La doping, the electrocatalytic electrode disclosed in this scheme belongs to the tin-antimony system electrode. By observing its morphological characteristics, the catalytic electrode with SnO2-Sb2O4-La composite material layer attached disclosed in this scheme has an uneven honeycomb morphology on its surface, and the surface is very evenly covered with SnO2 particles, with a rough coating structure and fine particle size. It can increase the effective contact area with dye wastewater. At the same time, La doping can improve the coating surface morphology, increase the active sites on the surface of the electrode active layer, and accelerate the electron transfer rate between the surface of the electrode active layer and the interface of the dye wastewater, thereby increasing the number of hydroxyl radicals on the electrode surface, improving the electrocatalytic activity of the electrode, and improving the degradation efficiency of the dye wastewater. In addition, La doping can effectively prevent the dye wastewater from infiltrating the coating and contacting the substrate, prevent the SnO2-Sb2O4-La composite material layer deposited on the substrate surface from falling off due to passivation of the substrate, and extend the service life of the electrode.

[0010] Preferably, the dye wastewater is dye wastewater containing Rhodamine B, and the concentration range of the Rhodamine B is 10 to 40 mg / L.

[0011] Preferably, the metal substrate is a titanium substrate with a thickness of 0.5 to 2.0 mm.

[0012] In a second aspect, the present invention further discloses a method for preparing an electrocatalytic electrode, using the electrocatalytic electrode as described above, comprising the following steps:

[0013] S1, pre-treating the metal substrate;

[0014] S2, placing the pretreated metal substrate into the reactor and using it as a cathode, using a graphite electrode as an anode, and connecting the cathode and the anode to the negative electrode and the positive electrode of a power source respectively through electrical wires;

[0015] S3, preparing a mixed solution according to a preset mixing ratio, adjusting the pH of the mixed solution to acidic, and then adding the mixed solution into a reactor, wherein the raw materials used to prepare the mixed solution include SnCl4·5H2O, Sb2O3, and La(NO3)3·6H2O;

[0016] S4, turning on the power supply so that the specified current density is maintained between the cathode and the anode, so that the substances in the mixed solution are deposited on the metal substrate. After the deposition time is preset, a SnO2-Sb2O4-La composite material deposition layer is formed on the metal substrate, and the deposition thickness is 0.2 to 0.8 mm;

[0017] S5. calcining the metal substrate with the SnO2-Sb2O4-La composite material deposition layer attached thereto, controlling the calcination temperature and time, and obtaining an electrocatalytic electrode with the SnO2-Sb2O4-La composite material layer attached thereto.

[0018] This scheme adopts the method of first depositing and then calcining to attach a SnO2-Sb2O4-La composite material deposition layer on a metal substrate. At the same time, during the deposition and calcination process, the ratio of each component, the deposition time, the calcination time and the calcination temperature are controlled, so that the obtained electrocatalytic electrode, when applied to dye wastewater containing Rhodamine B, can have a high efficiency in degradation rate and removal rate of Rhodamine B in the dye wastewater, and can also extend the service life of the electrocatalytic electrode.

[0019] Preferably, in step S1, the metal substrate is pretreated by first grinding it with sandpaper, then rinsing the ground metal substrate with deionized water, then immersing it in a NaOH solution for degreasing, then immersing it in an oxalic acid solution for micro-boiling etching, and finally rinsing it with deionized water to obtain a pretreated metal substrate.

[0020] Preferably, in step S3, the mixed solution is prepared by sequentially adding SnCl4·5H2O, Sb2O3 and La(NO3)3·6H2O to an isopropanol solution, then sequentially adding hydrochloric acid and citric acid, and then first ultrasonicating and then stirring at a constant temperature to obtain a mixed solution; in the mixed solution, the molar ratio of SnCl4·5H2O, Sb2O3 and La(NO3)3·6H2O is in the range of 100:10:0.5 to 100:10:3, wherein Sn 4+ The concentration is 0.3-0.6 mol / L; the volume ratio of isopropanol, hydrochloric acid and citric acid is 100:2:125, wherein the concentration of hydrochloric acid is 35%-40%, and the concentration of citric acid is 10%-20%.

[0021] Preferably, the metal substrate is a titanium substrate with a thickness of 0.5 to 2.0 mm.

[0022] Preferably, in step S4, the specified current density range is 10 to 40 mA·cm -2 , the deposition time is 15 to 30 minutes.

[0023] Preferably, in step S5, the calcination temperature is greater than 500° C., and the calcination time ranges from 1 to 2 hours.

[0024] In the third aspect, the present invention also discloses a method for treating dye wastewater, using the electrocatalytic electrode as described above, placing the electrocatalytic electrode as an anode into the dye wastewater containing Rhodamine B, and placing a substrate made of the same material as the metal substrate of the electrocatalytic electrode as a cathode into the same dye wastewater containing Rhodamine B, connecting the anode and the cathode to the positive and negative electrodes of a power source respectively through electrical conductors; turning on the power source to degrade the Rhodamine B in the dye wastewater.

[0025] The present invention has the following beneficial effects: compared with the electrocatalytic electrode not doped with La, the electrocatalytic electrode disclosed in the present scheme belongs to the tin-antimony system electrode, and its morphological characteristics are observed. The catalytic electrode with the SnO2-Sb2O4-La composite material layer attached thereto disclosed in the present scheme has an uneven honeycomb morphology on its surface, and the surface is very evenly covered with SnO2 particles, and has a rough coating structure and fine particle size. It can increase the effective contact area with dye wastewater, and at the same time, La doping can improve the coating surface morphology, increase the active sites on the surface of the electrode active layer, and accelerate the electron transfer rate between the surface of the electrode active layer and the interface of the dye wastewater, thereby increasing the number of hydroxyl radicals on the electrode surface, improving the electrocatalytic activity of the electrode, and improving the degradation efficiency of the dye wastewater. In addition, La doping can effectively prevent the dye wastewater from infiltrating the coating and contacting the substrate, prevent the SnO2-Sb2O4-La composite material layer deposited on the substrate surface from falling off due to passivation of the substrate, and extend the service life of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the purpose, technical solution and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0027] Figure 1 Schematic diagram of the electrocatalytic electrode structure of the present invention.

[0028] Figure 2 It is a schematic diagram of the dye wastewater treatment method of the present invention.

[0029] Figure 3 This is a comparison chart of the decolorization rates of different electrodes in Example 2 of the present invention.

[0030] Figure 4 This is a SEM image of Ti / SnO2 in Example 3 of the present invention.

[0031] Figure 5 This is the SEM image of Ti / SnO2-Sb2O4 in Example 3 of the present invention.

[0032] Figure 6 This is the SEM image of Ti / SnO2-Sb2O4-La in Example 3 of the present invention.

[0033] Figure 7 This is a schematic diagram of the EDS results of the Ti / SnO2-Sb2O4-La electrode in Example 3 of the present invention.

[0034] Figure 8 Schematic diagram of element mapping results of the Ti / SnO2-Sb2O4-La electrode in Example 3 of the present invention.

[0035] Fig. 9 This is the XRD spectrum of Ti / SnO2, Ti / SnO2-Sb2O4, and Ti / SnO2-Sb2O4-La in Example 3 of the present invention.

[0036] Fig.10 The different electrodes in Example 3 of the present invention are at 0.3 mol·L -1 Sodium sulfate and 20mg.L-1 rhodamine B solution at 4mV.s -1 The cyclic voltammetry curves were scanned at a scan rate of .

[0037] Fig.11 The different electrodes in Example 3 of the present invention are 10mV.s -1 Linear voltammetric curve of rate scan.

[0038] Fig.12 The different electrodes in Example 3 of the present invention are 0.1 mol·L -1 Sodium sulfate and 20mg.L -1 AC impedance spectrum and equivalent circuit diagram of Rhodamine B solution.

[0039] Fig.13 This is a schematic diagram of the degradation rate of Rhodamine B after 5 cycles by 1% Ti / SnO2-Sb2O4-La in Example 3 of the present invention.

[0040] Fig.14 Schematic diagram of accelerated life test of different electrodes in Example 3 of the present invention.

[0041] Fig.15 This is the absorption spectrum change of RhB solution treated with 1% Ti / SnO2-Sb2O4-La in Example 3 of the present invention.

[0042] Fig.16 The degradation rate and kinetic curve corresponding to the absorption spectrum in Example 3 of the present invention.

[0043] Fig.17 This is the effect of deposition time on the degradation rate of Rhodamine B in Example 4 of the present invention.

[0044] Fig.18This is the effect of calcination time on the degradation rate of Rhodamine B in Example 4 of the present invention.

[0045] Fig.19 This is the effect of calcination temperature on the degradation rate of Rhodamine B in Example 4 of the present invention.

[0046] Fig. 20 This is the effect of current density on the degradation rate of Rhodamine B in Example 4 of the present invention.

[0047] Fig.21 This is the effect of electrolyte concentration on the degradation rate of Rhodamine B in Example 4 of the present invention.

[0048] Fig. 22 The figure shows the effect of the pH value of the solution on the degradation rate of Rhodamine B in Example 4 of the present invention.

[0049] Fig.23 This is the effect of the initial concentration of Rhodamine B on the degradation rate of Rhodamine B in Example 4 of the present invention.

[0050] Fig.24 This is a schematic diagram of the treatment effect of using the electrocatalytic electrode prepared in Example 2 in Example 5 of the present invention to treat actual dye wastewater.

[0051] Description of reference numerals: 1. electrocatalytic electrode; 11. metal substrate; 12. SnO2-Sb2O4-La composite material layer; 2. cathode; 3. electric conductor; 4. dye wastewater; 5. power supply; DETAILED DESCRIPTION

[0052] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0053] It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the invention product is usually placed when used, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In addition, the terms "horizontal", "vertical", etc. do not mean that the components are absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] The present invention can be applied to the technical field of purifying dye wastewater by electrocatalytic oxidation, and is particularly suitable for the field of purifying dye wastewater. It solves the technical problems in the prior art that the electrode materials used in the electrochemical oxidation method are easy to passivate, have low current efficiency, and have high processing energy consumption, thereby resulting in weak electrocatalytic activity and a short service life of the electrode.

[0055] First, see Figure 1 Based on the technical problems solved above, the present invention discloses an electrocatalytic electrode 1 for purifying dye wastewater, comprising a metal substrate 11, on which a SnO2-Sb2O4-La composite material layer 12 is attached, wherein the SnO2-Sb2O4-La composite material layer has a thickness of 0.2 to 0.8 mm.

[0056] In the prior art, the catalytic electrode without La doping has a typical "cracked" morphology and a relatively smooth surface. This morphology indicates that the active layer is not tightly bonded to the titanium sheet, which seriously affects the service life of the electrode.

[0057] Compared with the electrocatalytic electrode without La doping, the electrocatalytic electrode disclosed in this scheme belongs to the tin-antimony system electrode. By observing its morphological characteristics, the catalytic electrode with SnO2-Sb2O4-La composite material layer attached disclosed in this scheme has an uneven honeycomb morphology on its surface, and the surface is very evenly covered with SnO2 particles, with a rough coating structure and fine particle size. It can increase the effective contact area with dye wastewater. At the same time, La doping can improve the coating surface morphology, increase the active sites on the surface of the electrode active layer, and accelerate the electron transfer rate between the surface of the electrode active layer and the interface of the dye wastewater, thereby increasing the number of hydroxyl radicals on the electrode surface, improving the electrocatalytic activity of the electrode, and improving the degradation efficiency of the dye wastewater. In addition, La doping can effectively prevent the dye wastewater from infiltrating the coating and contacting the substrate, prevent the SnO2-Sb2O4-La composite material layer deposited on the substrate surface from falling off due to passivation of the substrate, and extend the service life of the electrode.

[0058] Preferably, the dye wastewater is dye wastewater containing rhodamine B, the concentration of rhodamine B is 10-40 mg / L, and the corresponding removal rate is above 90%. When the concentration of rhodamine B is 10-30 mg / L, the removal rate is above 99%.

[0059] Rhodamine B (RhB) dye is a common water-soluble dye widely used in the textile industry to dye wool fabrics. In addition, in other industries such as papermaking, plastics, printing, biomedicine and leather, Rhodamine B is often used as a colorant, photosensitizer, water tracer, fluorescent marker for microstructural analysis and biological stain in biomedical research. However, Rhodamine B is inherently mutagenic and carcinogenic. If ingested, it can cause serious effects on the development, central nervous system and other organs (including liver, kidneys, etc.) of humans or animals. In recent years, studies have found that electrochemical oxidation has a significant effect on the degradation of Rhodamine B, which is a very promising method.

[0060] When this scheme is applied to the degradation of Rhodamine B, at low current density, the degradation rate of Rhodamine B by the Ti / SnO2-Sb2O4-La electrode can reach 99.78%. Compared with the Ti / SnO2-Sb2O4 electrode, the service life of this electrode is increased by 3 times.

[0061] Preferably, the metal substrate is a titanium substrate with a thickness of 0.5 to 2.0 mm.

[0062] The advantages of using titanium sheets are good stability and not easy to corrode after long-term use; high activity and can effectively promote oxidation reactions; low cost, simple manufacturing process, and economical materials; good mechanical properties, high strength, and resistance to harsh conditions; flexible processing and can be made into different shapes according to needs; corrosion resistance and resistance to erosion by a variety of chemical substances; high current efficiency, reduced energy consumption, and improved efficiency; low overpotential: reduced energy consumption; reusable, reducing replacement costs.

[0063] Specifically, the effective area of ​​the electrocatalytic electrode, that is, the attachment area of ​​the SnO2-Sb2O4-La composite material layer is greater than 80% of the surface area of ​​the metal substrate, and the remaining metal substrate is a bare substrate used to connect a power source to energize the metal substrate.

[0064] The electrocatalytic electrode disclosed in the present invention has the following technical effects: the electrode without La doping has a typical "crack" morphology, and the surface is relatively smooth. This morphology indicates that the active layer is not tightly bonded to the titanium sheet, which seriously affects the service life of the electrode. For the La doped electrode, it can be clearly seen that the electrode surface has an uneven honeycomb morphology, and the surface is very evenly covered with SnO2 particles, with a rough coating structure and fine particle size, which increases the effective contact area with the dye wastewater and has more active sites, thereby improving the catalytic effect.

[0065] In a second aspect, the present invention further discloses a method for preparing an electrocatalytic electrode, using the electrocatalytic electrode as described above, comprising the following steps:

[0066] S1, pre-treating the metal substrate;

[0067] S2, placing the pretreated metal substrate into the reactor and using it as a cathode, using a graphite electrode as an anode, and connecting the cathode and the anode to the negative electrode and the positive electrode of a power source respectively through electrical wires;

[0068] S3, preparing a mixed solution according to a preset mixing ratio, adjusting the pH of the mixed solution to acidic, and then adding the mixed solution into a reactor, wherein the raw materials used to prepare the mixed solution include SnCl4·5H2O, Sb2O3, and La(NO3)3·6H2O;

[0069] S4, turning on the power supply so that the specified current density is maintained between the cathode and the anode, so that the substances in the mixed solution are deposited on the metal substrate. After the deposition time is preset, a SnO2-Sb2O4-La composite material deposition layer is formed on the metal substrate, and the deposition thickness is 0.2 to 0.8 mm;

[0070] S5. calcining the metal substrate with the SnO2-Sb2O4-La composite material deposition layer attached thereto, controlling the calcination temperature and time, and obtaining an electrocatalytic electrode with the SnO2-Sb2O4-La composite material layer attached thereto.

[0071] This scheme adopts the method of first depositing and then calcining to attach a SnO2-Sb2O4-La composite material deposition layer on a metal substrate. At the same time, during the deposition and calcination process, the ratio of each component, the deposition time, the calcination time and the calcination temperature are controlled, so that the obtained electrocatalytic electrode, when applied to dye wastewater containing Rhodamine B, can have a high efficiency in degradation rate and removal rate of Rhodamine B in the dye wastewater, and can also extend the service life of the electrocatalytic electrode.

[0072] Preferably, in step S1, the metal substrate is pretreated by first grinding it with sandpaper, then rinsing the ground metal substrate with deionized water, then immersing it in a NaOH solution for degreasing, then immersing it in an oxalic acid solution for micro-boiling etching, and finally rinsing it with deionized water to obtain a pretreated metal substrate.

[0073] Preferably, in step S3, the mixed solution is prepared by sequentially adding SnCl4·5H2O, Sb2O3 and La(NO3)3·6H2O to an isopropanol solution, then sequentially adding hydrochloric acid and citric acid, and then first ultrasonicating and then stirring at a constant temperature to obtain a mixed solution; in the mixed solution, the molar ratio of SnCl4·5H2O, Sb2O3 and La(NO3)3·6H2O is in the range of 100:10:0.5 to 100:10:3, wherein Sn 4+ The concentration is 0.3-0.6 mol / L; the volume ratio of isopropanol, hydrochloric acid and citric acid is 100:2:125, wherein the concentration of hydrochloric acid is 35%-40%, and the concentration of citric acid is 10%-20%.

[0074] Preferably, the metal substrate is a titanium substrate.

[0075] Preferably, in step S4, the specified current density range is 10 to 40 mA·cm -2 , the deposition time is 15 to 30 minutes.

[0076] Preferably, in step S5, the calcination temperature is greater than 500° C., and the calcination time ranges from 1 to 2 hours.

[0077] Specifically, in step S5, the metal substrate with the SnO2-Sb2O4-La composite material deposition layer attached thereto is placed in a tube furnace at 600° C. and calcined for 120 minutes.

[0078] The preparation method of the electrocatalytic electrode disclosed in the present invention has the following technical effects: the preparation method of the electrocatalytic electrode adopts the method of first depositing and then calcining to attach a SnO2-Sb2O4-La composite material deposition layer on a metal substrate. At the same time, in the process of deposition and calcination, the ratio of each component, the deposition time, the calcination time and the calcination temperature are controlled, so that when the obtained electrocatalytic electrode is applied to dye wastewater containing rhodamine B, the electrode surface doped with La has an uneven honeycomb morphology, and the surface is very evenly covered with SnO2 particles, has a rough coating structure and a fine particle size, and has more active sites while increasing the effective contact area with the dye wastewater, thereby improving the catalytic effect, and can have an efficient degradation rate and a high removal rate for rhodamine B in the dye wastewater. In addition, the doping of La can effectively prevent the dye wastewater from infiltrating the coating and contacting the substrate, prevent the SnO2-Sb2O4-La composite material layer deposited on the substrate surface from falling off due to passivation of the substrate, and extend the service life of the electrode.

[0079] In the third aspect, the present invention also discloses a method for treating dye wastewater. Figure 2 , using the electrocatalytic electrode 1 as described above, the electrocatalytic electrode 1 is placed as an anode in the dye wastewater 4 containing rhodamine B, and a substrate made of the same material as the metal substrate of the electrocatalytic electrode 1 is used as a cathode 2 and placed in the same dye wastewater 4 containing rhodamine B, and the anode and the cathode are respectively connected to the positive and negative electrodes of a power source 5 through an electrical conductor 3; the power source 5 is energized to degrade the rhodamine B in the dye wastewater.

[0080] In summary, the electrocatalytic electrode and preparation method thereof, and dye wastewater treatment method disclosed in the present invention have the following technical effects:

[0081] 1. The present invention prepares a novel Ti / SnO2-Sb2O4 electrode doped with rare earth La. This electrocatalytic electrode belongs to a tin-antimony electrode. By observing its morphological characteristics, the catalytic electrode with a SnO2-Sb2O4-La composite material layer attached thereto disclosed by the present invention has an uneven honeycomb morphology on its surface, and the surface is very evenly covered with SnO2 particles, with a rough coating structure and fine particle size. It can increase the effective contact area with dye wastewater. At the same time, La doping can improve the coating surface morphology, increase the active sites on the surface of the electrode active layer, and accelerate the electron transfer rate between the surface of the electrode active layer and the interface of the dye wastewater, thereby increasing the number of hydroxyl radicals on the electrode surface, improving the electrocatalytic activity of the electrode, and improving the degradation efficiency of the dye wastewater. In addition, La doping can effectively prevent the dye wastewater from infiltrating the coating and contacting the substrate, prevent the SnO2-Sb2O4-La composite material layer deposited on the substrate surface from falling off due to passivation of the substrate, and extend the service life of the electrode.

[0082] 2. The catalytic electrode with a SnO2-Sb2O4-La composite material layer disclosed in the present invention can achieve a degradation rate of 99.78% for Rhodamine B at a low current density.

[0083] 3. The catalytic electrode with a SnO2-Sb2O4-La composite material layer disclosed in the present invention has a service life increased by 3 times compared with the Ti / SnO2-Sb2O4 electrode.

[0084] 4. In the catalytic electrode with a SnO2-Sb2O4-La composite material layer disclosed in the present invention, the degradation of Rhodamine B is attributed to electrocatalytic oxidation and ·OH oxidation. The degradation rate of Rhodamine B can be further improved through the dual oxidation effect.

[0085] In order to further optimize or illustrate the electrocatalytic electrode and its preparation method, and the dye wastewater treatment method of the present invention, the present invention discloses the following embodiments.

[0086] Embodiment 1

[0087] In this embodiment, a titanium sheet is used as a metal substrate to prepare an electrocatalytic electrode with a SnO2-Sb2O4-La composite material layer attached thereto. The size of the metal substrate is 80 mm×20 mm×1 mm (length×width×thickness).

[0088] When preparing an electrocatalytic electrode with a SnO2-Sb2O4-La composite material layer attached, the titanium sheet is first pretreated. The specific pretreatment method is to grind it with sandpaper until the surface has a silvery white metallic luster, rinse the polished titanium sheet with deionized water, degrease it with 6% NaOH for 150 minutes, etch it with a 20% oxalic acid solution for 120 minutes, and rinse it with deionized water; put the pretreated metal substrate into a reactor and use it as a cathode, use a graphite electrode as an anode, and connect the cathode and the anode to the negative and positive electrodes of a power source respectively through electrical wires;

[0089] Then, the mixed solution was prepared according to the preset mixing ratio, and the pH of the mixed solution was adjusted to acidic, and then the mixed solution was added to the reactor. The mixed solution was prepared by adding SnCl4·5H2O, Sb2O3 and La(NO3)3·6H2O to 40mL of isopropanol solution, and the molar ratio of each component was 100:10:1, wherein Sn 4+ The concentration is 0.5 mol / L, and then 0.8 mL of hydrochloric acid (37%) and 5 mL of citric acid (10%) are added, and the solution is placed in an ultrasonic machine at a constant temperature of 25°C for 15 minutes, and then magnetically stirred for 60 minutes to obtain a mixed solution;

[0090] A constant current of 0.12A is passed through the electric wires of the cathode and the anode through a power supply, so that the substances in the mixed solution are deposited on the metal substrate. After deposition for 30 minutes, a SnO2-Sb2O4-La composite material deposition layer is formed on the metal substrate;

[0091] The metal substrate with the SnO2-Sb2O4-La composite material deposition layer attached thereto was placed in a tube furnace and calcined for 120 minutes at 600°C to obtain an electrocatalytic electrode with the SnO2-Sb2O4-La composite material layer attached thereto.

[0092] The effective area of ​​the electrocatalytic electrode obtained in this embodiment is 30 mm×20 mm. The effective area of ​​the electrocatalytic electrode is smaller than the specification of the titanium sheet because the exposed titanium sheet needs to be reserved for connecting to a power source. The area of ​​the exposed titanium sheet is approximately 10 mm×20 mm.

[0093] The single Ti / SnO2 electrode is a representative type of electrode in electrochemical oxidation technology. It has lower cost than boron-doped diamond (BDD) electrode, higher oxygen evolution potential and catalytic ability than Ti / PbO2 electrode, and better removal effect than Ti / IrO2 electrode. However, SnO2 has weak conductivity and is prone to agglomeration, resulting in poor corrosion resistance. Doping with Sb and rare earth element La can reduce the crystallinity of SnO2, reduce agglomerates, and change the conductivity of SnO2. Moreover, the electrocatalytic activity of La is better than that of other rare earth elements (Ce, Eu, Pr, Nd, Sm). The presence of La can cause the "remaining electrons" that form bonds with other elements to deform due to polarization, so that La can enter the electrode coating lattice in the form of interstitial filling or substitution, and can introduce deep energy level impurity bands into the inner conductor band of SnO2, providing a lower energy level channel for the transmission of electrons, thereby improving the conductivity of the electrode. In addition, La doping can improve the surface morphology of the coating. While increasing the active sites, it can effectively prevent the solution from penetrating into the coating and contacting the titanium plate, prevent the titanium plate from passivating and causing the coating to fall off, and extend the service life of the electrode.

[0094] Embodiment 2

[0095] In this embodiment, a titanium sheet is used as a metal substrate to prepare an electrocatalytic electrode with a SnO2-Sb2O4-La composite material layer attached thereto. The specification of the metal substrate is 70 mm×20 mm×2 mm.

[0096] First, the titanium plate was polished with sandpaper until the surface showed a silvery white metallic luster, and then the polished titanium plate was rinsed with deionized water, degreased with 5% NaOH for 2 hours, slightly boiled and etched in 15% oxalic acid solution for 2 hours, and then rinsed with deionized water.

[0097] The pretreated titanium plate was used as the cathode, and SnCl4.5H2O, Sb2O3 and LaN3O9·6H2O were added to 40 ml of isopropanol solution. The molar ratio of each component was 100:10:x, where x was 0.5, 1, 2, and 3, respectively. 4+ The concentration is 0.5 molL -1 , then add 0.8ml hydrochloric acid (37%) and 5ml citric acid (10%), place the solution in an ultrasonic machine at a constant temperature of 25℃ for 15min, then stir it magnetically for 1h, and finally deposit it at a constant current of 0.12A for 15min, with an effective area of ​​30mm x 20mm x1mm. Both the cathode and cathode are titanium plates, and the deposited titanium plates are placed in a tubular furnace at 500℃ and calcined for 2h to obtain an electrocatalytic electrode with a SnO2-Sb2O4-La composite material layer attached.

[0098] The effective area of ​​the electrocatalytic electrode with the SnO2-Sb2O4-La composite material layer attached obtained in this example is 20 mm×20 mm.

[0099] Next, the catalytic performance of the electrode with SnO2-Sb2O4-La composite material layer obtained in this example was analyzed: In this example, according to the different molar ratios of the components, in 100 mL, 0.1 mol L -1 Na2SO4 and 20mg L -1 The prepared electrode was used as anode and titanium plate as cathode at a current density of 30 mA cm -2 RhB was degraded at a constant current for 30 mins under the condition of . The absorbance of RhB at a specific wavelength of 554 nm was measured by UV-Vis spectrophotometer and substituted into formula 1 to calculate the degradation rate of RhB.

[0100] The accelerated life of the electrode was studied by using Ti / SnO2-Sb2O4-1%La (effective area of ​​20 mm×20 mm) as the anode and titanium plate as the cathode in 1M H2SO4 at 1 mA cm -2 The electrode was considered inactivated when the cell voltage reached 10 V, and the duration of the test was recorded as the accelerated life of the electrode. The effect of ·OH on the degradation of RhB was studied using tert-propyl alcohol (TBA) as a free radical cleaner.

[0101] exist Figure 3The results show that the degradation rate of rhodamine B by 1% Ti / SnO2-Sb2O4-La after half an hour (Eq. (1)) reached a maximum of 99.84%, which is better than Ti / SnO2 (75.11%) and Ti / SnO2-Sb2O4 (82.72%). This is because the doping of rare earth element La increases the adsorption of oxygen in oxygen vacancies inside the electrode coating and reduces lattice oxygen, which is conducive to the production of more hydroxyl radicals, thereby improving the catalytic performance of the electrode. The reaction kinetics of the degradation process of rhodamine B were fitted. The relationship between the degradation of rhodamine B and the rate-degradation time conforms to the pseudo-first-order kinetic equation Eq. (2). The results show that Ti / SnO2-Sb2O4-1% La achieves the fastest reaction kinetic rate constant k (0.1952min -1 ), respectively Ti / SnO2(0.0463min -1 )、Ti / SnO2-Sb2O4

[0102] (0.0592min -1 ), Ti / SnO2-Sb2O4-0.5%La(0.0711min -1 ), Ti / SnO2-Sb2O4-2%La (0.1060min -1 ), Ti / SnO2-Sb2O4-3%La (0.0809min -1 ), which may be because the addition of La increases the active sites on the surface of the electrode active layer, accelerates the electron transfer rate between the surface of the electrode active layer and the solution interface, thereby increasing the number of hydroxyl radicals on the electrode surface and improving the electrocatalytic activity of the electrode. If the doping amount of La is too low, the coating will be partially modified and not optimal. If it is too high, point defects will aggregate into electron-hole recombination centers, reducing conductivity, and will damage the coating to increase the lattice, resulting in a decrease in catalytic effect.

[0103]

[0104]

[0105] In formula (1) and formula (2), C0 and C t Represents the concentration of RhB at degradation time 0 and t (min) (mg.L -1 ).

[0106] Embodiment 3

[0107] Based on the conclusion of Example 2, the electrocatalytic electrode Ti / SnO2-Sb2O4-1%La prepared by using SnCl4.5H2O, Sb2O3 and LaN3O9·6H2O with a molar ratio of each component of 100:10:1 was analyzed for characteristics:

[0108] 1. Electrode surface morphology

[0109] Electrode surface morphology analysis was performed using a field emission electron scanning microscope (SEM. ZEISS GeminiSEM 300. Germany), see Figures 4 to 6 The SEM images of three different electrodes are shown, and the differences in the surface morphology of the three electrodes can be clearly observed. Figure 4 and Figure 5 There is a typical "crack" morphology, and the surface is relatively smooth, which may be due to the hydrogen dissolution side reaction during the electrodeposition process. This morphology indicates that the active layer is not tightly bonded to the titanium sheet, which seriously affects the service life of the electrode. Figure 5 The crack ratio Figure 4 The cracks are small, indicating that doping Sb can improve the surface morphology of the electrode, while improving the use effect and extending the service life of the electrode. Figure 6 From the SEM image of the La-doped electrode, it can be clearly seen that the electrode surface has an uneven honeycomb morphology. From the further enlarged image, it can be seen that its surface is very evenly covered with SnO2 particles with a rough coating structure and fine particle size, which increases the effective contact area with the solution and produces more active sites, thereby improving the catalytic effect.

[0110] 2. Qualitative and semi-quantitative composition analysis of elements

[0111] The qualitative and semi-quantitative composition of the elements is analyzed by energy dispersive spectroscopy (EDS), see Figure 7 and Figure 8 , Figure 7 The EDS results of Ti / SnO2-Sb2O4-La show that the Ti / SnO2-Sb2O4-La electrode is composed of four elements: O, Sn, Sb and La, indicating that La is successfully doped into the electrode and the corresponding oxides are generated from Sn, Sb and La. Figure 8 The element mapping in shows the uniform distribution of the four elements O, Sn, Sb and La in the coating, proving that the active coating is evenly covered on the titanium sheet and can effectively prevent the exposed titanium metal from reacting with oxygen to form a TiO2 passivation layer during the electrocatalytic process, thereby extending the service life of the electrode.

[0112] 3. Crystal structure analysis

[0113] The crystal structure of the produced materials was evaluated by X-ray diffractometer (XRD. Shimadzu XRD-6100. Japan). Fig. 9 As shown, the diffraction peaks of all electrodes at 2Theta = 26.61, 33.89, and 51.78 correspond to the (110), (101), and (211) crystal planes of the cubic rutile SnO2 phase, respectively. No characteristic peaks of Sb2O4 and La were observed in the figure, but it can be seen that the peak intensity of the La-doped electrode is the highest, which indicates that these two elements are replaced or filled in the SnO2 lattice, and doping does not introduce a new phase structure and does not change the crystal structure of the material. The narrowing of the diffraction peak width indicates that the La-doped electrode coating has smaller grains, a larger specific surface area, and improved conductivity and stability.

[0114] 4. Electrochemical test

[0115] Electrochemical tests were performed using a conventional three-electrode cell system (working electrode: Ti / SnO2-Sb2O4-1% La, reference electrode: saturated calomel electrode (SCE), auxiliary electrode: Pt electrode), and electrochemical analysis was performed using a CHI600E electrochemical workstation. -1 Rhodamine B and 0.1 mol·L -1 The cyclic linear voltammetry (CV) curve of the test electrode in Na2SO4 was measured in the scanning range of -0.5 to 2.0 V. The oxygen evolution potential (OEP) of the electrode was measured by linear sweep voltammetry (LSV) in the scanning range of 0.5 to 2.5 V. 5 Hz~0.1Hz, amplitude is 10mV.s -1 Electrochemical impedance spectroscopy (EIS) was measured under the following conditions.

[0116] Fig.10 For different electrodes at 0.3 mol·L -1 Sodium sulfate and 20mg.L -1 Rhodamine B solution at 4mV.s -1 The cyclic voltammetry curve was scanned at a scan rate of , and the CV curve showed that there was only one oxidation peak corresponding to the oxidation of RhB, and no reduction peak, indicating that the oxidation of RhB was an irreversible process. Doping Sb2O4 on the basis of Ti / SnO2 can improve the conductivity of the electrode, significantly increase the peak current in the same potential window, and significantly increase the area of ​​the CV curve. After doping La, the area and peak current are further improved. The increase in area indicates that the electrode has more catalytic active sites and has excellent electrocatalytic performance. The increase in peak current means that the conductivity of the electrode is improved.

[0117] Therefore, La doping greatly improves the electrode activity and catalytic performance.

[0118] The LSV curves of different electrodes are as follows: Fig.11 As shown, the scan rate is 10mV.s -1 Anodic oxygen evolution is a competitive reaction of pollutants in anodic oxidation, which leads to power loss and the formation of bubbles on the electrode surface, which also has a negative impact on the reaction area. A high oxygen evolution potential can reduce the oxygen evolution reaction at the anode (Equation 3), which is beneficial to the generation of ·OH and improves the current efficiency.

[0119] Mo x [·OH]+H2O→Mo x +O2 (3)

[0120] Fig.11 The oxygen evolution potential (2.20 V) of the La-doped Ti / SnO2-Sb2O4 electrode was higher than that of the undoped electrodes Ti / SnO2 (2.09 V) and Ti / SnO2-Sb2O4 (2.14 V). The results showed that La-doping can produce the best current efficiency to inhibit the oxygen evolution reaction.

[0121] Table 1. EIS fitting analysis results of different electrodes

[0122] <![CDATA[R s (Ω.cm -2 )]]> <![CDATA[R ct (Ω.cm -2 )]]> <![CDATA[CEP(mF.cm -2 )]]> <![CDATA[Ti / SnO2]]> 7.962 6.209 0.594 <![CDATA[Ti / SnO2-Sb2O4]]> 7.631 1.105 0.631 <![CDATA[Ti / SnO2-Sb2O4-La]]> 7.119 0.198 1.173

[0123] Fig.12 For different electrodes at 0.1 mol L -1 Na2SO4 and 20mg L -1 The AC impedance spectrum and equivalent circuit diagram in Rhodamine B solution are used to measure the charge transfer resistance of the electrode. The points in the figure represent the experimental values. The equivalent circuit that best matches the experimental data is R s (R ct CPE), where Rs, Rct and CPE are electrolyte resistance, charge transfer resistance and constant phase element respectively. According to the simulation results in Table 1, it can be seen that the R s The lowest, indicating the best conductivity; R ct The lowest CEP indicates that the electrode surface has the highest electron transfer rate, can promote the generation of ·OH, and has good electrocatalytic activity; a higher CEP indicates that it has a larger specific surface area and more active sites.

[0124] 5. Electrode stability test

[0125] (1) Cyclic degradation

[0126] Under the optimal conditions, the stability test of Ti / SnO2-Sb2O4-La was carried out. The experimental results are as follows: Fig.13As shown, after 5 cycles, the degradation rate of Rhodamine B by Ti / SnO2-Sb2O4-La decreased by 3.12%, indicating that Ti / SnO2-Sb2O4-La can stably and effectively remove organic matter.

[0127] (2) Accelerated life test

[0128] In 1.0M H2SO4 electrolyte and 500mA·cm -2 The accelerated life test of different electrodes was carried out under high current density conditions. Fig.14 As shown, the accelerated life of Ti / SnO2-Sb2O4-La is 90min, which is 3 times the accelerated life of Ti / SnO2-Sb2O4 electrode and 9 times the accelerated life of Ti / SnO2. In order to make the comparison more intuitive, the actual service life of Ti / SnO2-Sb2O4-La is calculated to be 1667hrs according to the Correa-Lozano formula. The results show that the actual service life of Ti / SnO2-Sb2O4-La electrode is higher than that of most electrodes because the dense and uniform active layer structure formed after La doping can effectively improve the service life of the electrode.

[0129]

[0130] In formula (4), i1 is the actual current density, t1 is the actual service life, i2 is the accelerated current density, and t2 is the accelerated service life. By comparison, the stability of the Ti / SnO2-Sb2O4-La electrode is higher.

[0131] (3) Absorption spectrum

[0132] In order to better observe the absorbance evolution of RhB during electrochemical oxidation, Fig.15 The UV-Vis absorption spectra of RhB at different degradation time periods are shown. As can be seen from the figure, RhB is gradually degraded by deethylation, indicating that Ti / SnO2-Sb2O4-La has a good decolorization effect on RhB. Fig.16 The decolorization curve corresponding to the UV-Vis absorption spectrum and the fitting of the first-order kinetic model finally reached almost 100% decolorization rate. The fitting results of the first-order kinetic model showed that the rate constant of Ti / SnO2-Sb2O4-La reached 0.2237min -1 .

[0133] In this example, a rare earth lanthanum-doped Ti / SnO2-Sb2O4 electrode was successfully prepared by electrodeposition for 15 minutes and calcined at 500°C for 2 hours, and its degradation efficiency for rhodamine B was studied. SEM and XRD results show that the surface structure of the Ti / SnO2-Sb2O4-La electrode is dense and the particles are fine. At the same time, it has a higher oxygen evolution overpotential than Ti / SnO2 and Ti / SnO2-Sb2O4 and a better degradation effect on rhodamine B. At a current density of 20 mA cm -2 , electrolyte concentration 0.3 mol·L -1 , 20 mg.L at pH 3 -1 The Rhodamine B was completely degraded in 30 min. After 5 cycles, the degradation rate of Rhodamine B by Ti / SnO2-Sb2O4-La was only reduced by 3.12%, and the service life was 3 times that of the Ti / SnO2-Sb2O4 electrode. In addition, the degradation of RhB was attributed to the direct oxidation of and the indirect oxidation of OH. Doping Sb in the Ti / SnO2 electrode can improve the conductivity, and doping La can reduce the crystallinity of SnO2, reduce agglomerates, and improve the electrocatalytic activity.

[0134] Embodiment 4

[0135] Based on the conclusion of Example 2, an electrocatalytic electrode Ti / SnO2-Sb2O4-1%La was prepared using SnCl4.5H2O, Sb2O3 and LaN3O9·6H2O with a molar ratio of each component of 100:10:1, and the effects of different deposition time, calcination temperature, calcination time, current density, electrolyte concentration, solution pH value, and initial concentration of Rhodamine B on the final treatment effect of the electrocatalytic electrode were investigated.

[0136] 1. Sedimentation time

[0137] like Fig.17 As shown, the deposition time is 10 min, 15 min, 20 min, 25 min and 30 min respectively. As the deposition time increases, the coating becomes thicker and the RhB degradation rate is improved. For this embodiment, the decolorization rate reaches the best when the deposition time reaches 15 min. However, when the deposition time continues to increase, the coating falls off due to being too thick and unstable, thereby reducing the RhB degradation rate.

[0138] 2. Calcination time

[0139] Calcination time will affect the crystal shape and size of the catalyst on the electrode surface as well as the performance of the membrane. Fig.18The effect of calcination time on the performance of Ti / SnO2-Sb2O4-La. As can be seen from the figure, as the calcination time increases, the degradation rate of RhB gradually increases. For this example, the degradation effect is best when the calcination time is 2h. If the calcination time is too long, the crystals will regrow and become larger in size, affecting the degradation effect.

[0140] 3. Calcination temperature

[0141] The calcination temperature will also directly affect the crystal form, size and film firmness of the catalyst on the electrode surface. Therefore, considering the effect of calcination temperature on the performance of Ti / SnO2-Sb2O4-La, the experimental results are as follows Fig.19 As shown in the figure, as the temperature increases, the degradation rate of RhB gradually increases. When the calcination temperature is 500°C, Ti / SnO2-Sb2O4-La shows the best degradation effect. Because when the temperature is lower than 500°C, the elements inside the coating cannot be completely oxidized, resulting in poor electrode catalytic effect, but when the calcination temperature continues to increase, the degradation rate decreases. This is because the increase in temperature makes the catalyst more likely to fall off, thus affecting the electrocatalytic performance.

[0142] 4. Current density

[0143] Fig. 20 The effect of current density on the degradation rate of Rhodamine B is shown in Figure 2. Low current density produces less ·OH. As the current density increases, more ·OH can be produced, which increases the degradation rate of Rhodamine B. When the current density rises to 30 mA·cm -2 and 40mA·cm -2 When the final degradation rate reaches more than 99%.

[0144] 5. Electrolyte concentration

[0145] Fig. 22 The effect of electrolyte concentration on the degradation rate of rhodamine B is shown in Figure 2. In this experiment, Na2SO4 was selected as the supporting electrolyte because it can avoid the production of carcinogenic and toxic chlorinated substances. Increasing the electrolyte concentration within a certain range can increase the conductivity of the solution and accelerate the electron conversion in the reaction. When the Na2SO4 concentration increases, the decolorization rate also increases. However, when the Na2SO4 concentration increases to 0.7 mol·L -1 When the decolorization rate decreases, the excess Na2SO4 will form a salt film on the electrode surface. High concentrations of sulfate can react under appropriate conditions, as shown in equations (5) and (6):

[0146] SO4 2- + OH → SO4 - +OH- (5)

[0147] 2SO4 2- →S2O82- (6)

[0148] Therefore, S2O8 in sulfate medium 2- The formation of OH will deplete the degradation rate of rhodamine B. -1 and 0.5 mol·L -1 The final degradation rate reached more than 99%, so from the perspective of cost, 0.3 mol·L -1 as the optimal electrolyte concentration.

[0149] 7. Solution pH

[0150] Fig. 22 The figure shows the effect of solution pH on the degradation rate of Rhodamine B. The solution pH is adjusted by 1M NaOH and 1M H2SO4. It can be seen from the figure that the degradation rate is best under acidic conditions because acidic conditions are conducive to the formation of H2O2. H2O2 and SnO2 produce adsorbed M-OH radicals at the anode, as shown in equations (7) and (8):

[0151] O2+2H + +2e - →H2O2 (7)

[0152] H2O2→·OH+·OH (8)

[0153] When the concentration of H2O2 is high, the concentration of ·OH produced will also increase accordingly, as shown in equations (9) and (10):

[0154] 1 / 2H2O2+SnO2→SnO2(OH) (9)

[0155] SnO2+OH-=SnO2(OH)+e - (10)

[0156] When the pH value continues to decrease, that is, when it is too acidic, the excessive acid solution in the environment increases the corrosion of the electrode, affecting the catalytic activity and service life of the electrode, resulting in a decrease in the degradation rate. Under alkaline conditions, the electrode is prone to oxygen evolution reaction, which leads to a decrease in the degradation rate of Rhodamine B. Therefore, it can be seen from the figure that the optimal solution pH for the degradation of Rhodamine B is 3.

[0157] 8. Initial concentration of Rhodamine B

[0158] Fig.23The figure shows the effect of the initial concentration of Rhodamine B on its degradation rate. It can be seen from the figure that as the concentration of Rhodamine B increases, the degradation rate decreases. Because in the electrochemical degradation process and when other conditions remain unchanged, the amount of ·OH produced is certain, but as the initial concentration of RhB increases, more ·OH is consumed, so the production of ·OH limits the improvement of the degradation rate. In addition, the increase in the concentration of Rhodamine B also leads to the production of more intermediates during the electro-oxidation process, and more compounds are transferred to the electrode surface. This prevents the contact between the pollutants and the active sites, and the intermediates will also compete with organic matter for the reaction of ·OH to limit the degradation of Rhodamine B.

[0159] This example analyzes the effects of current density, electrolyte concentration, initial concentration of Rhodamine B solution, and pH value on water treatment. The results show that when the current density ranges from 20 to 60 mA·cm -2 When the current density is 50 mA·cm -2 The above Rhodamine B degradation rate is better;

[0160] When the electrolyte concentration is between 0.1 and 0.7 mol·L -1 The degradation rate of rhodamine B was higher when the electrolyte concentration was 0.3 mol·L -1 and 0.5 mol·L -1 The degradation rate of rhodamine B is better when

[0161] When the solution pH is acidic, the degradation rate of Rhodamine B is higher, and when the solution pH is ≤3, the degradation rate of Rhodamine B is better;

[0162] When the initial concentration of rhodamine B is between 10 and 40 mg / L, the degradation rate of rhodamine B is relatively high, and when the initial concentration of rhodamine B is ≤30 mg / L, the degradation rate of rhodamine B is better.

[0163] In addition, the same operation steps were used in this embodiment, with the initial concentration of rhodamine B = 30 mg / L, the solution pH = 3, and the current density 30 mA·cm -2 , electrolyte concentration 0.3 mol·L -1 , under the premise of the deposition time being 15 min, other groups of experiments were carried out, as shown in Table 2.

[0164] Table 2 Degradation rate of Rhodamine B by electrocatalytic electrodes prepared under other parameter conditions

[0165]

[0166] It can be seen from the content of Table 2 that within the range of the influencing factor parameters disclosed in the present invention, the electrocatalytic electrode and the preparation method thereof disclosed in the present invention have a good degradation rate (greater than 98.6%) for the degradation of Rhodamine B, and can effectively remove the dye component of Rhodamine B in the dye wastewater.

[0167] Embodiment 5

[0168] The electrocatalytic electrode prepared in Example 2 is used to treat actual dye wastewater. Specifically, the concentration of Rhodamine B in the actual dye wastewater used in this example is 20 mg / L.

[0169] Fig.24 The decolorization rate of Rhodamine B in different solutions is shown in the figure. It can be seen from the figure that the decolorization rate in pure water (99.84%) is greater than that in tap water (96.13%) and real wastewater (93.29%), which is reduced by 3.71% in tap water and 6.55% in real wastewater. This shows that Ti / SnO2-Sb2O4-La can still achieve a high decolorization rate under the condition of interference from other metal ions, and also shows that the Ti / SnO2-Sb2O4-La electrode has good stability.

[0170] In this embodiment, the Ti / SnO2-Sb2O4-La electrode is used to degrade dye wastewater by electrocatalytic oxidation. La doping can not only reduce the crystallinity of SnO2, reduce agglomerates, increase active sites, and improve electrocatalytic activity, but also change the surface morphology of the coating, prevent the solution from penetrating into the coating and contacting the titanium substrate, prevent the titanium substrate from being passivated and causing the coating to fall off, and extend the service life of the electrode. At the same time, the electrocatalytic oxidation method is not only efficient and fast in degrading dye wastewater, but also reduces the risk of secondary pollution to the environment.

[0171] It is understood that the present invention is described by some embodiments, and those skilled in the art are aware that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. Under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. The embodiments described in the present invention are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all other embodiments obtained by ordinary technicians in the art without creative work based on the embodiments in the present invention belong to the scope of protection of the present invention.

Claims

1. An electrocatalytic electrode for purifying dye wastewater, characterized in that: It comprises a metal substrate, on which a SnO2-Sb2O4-La composite material layer is attached, wherein the SnO2-Sb2O4-La composite material layer has a thickness of 0.2-0.8 mm.

2. The electrocatalytic electrode according to claim 1, characterized in that The dye wastewater is dye wastewater containing rhodamine B, and the concentration of the rhodamine B is 10-40 mg / L.

3. The electrocatalytic electrode according to claim 1, characterized in that The metal substrate is a titanium substrate with a thickness of 0.5 to 2.0 mm.

4. A method for preparing an electrocatalytic electrode, using the electrocatalytic electrode as claimed in claim 1, characterized in that: The following steps are involved: S1, pre-treating the metal substrate; S2, placing the pretreated metal substrate into the reactor and using it as a cathode, using a graphite electrode as an anode, and connecting the cathode and the anode to the negative electrode and the positive electrode of a power source respectively through electrical wires; S3, preparing a mixed solution according to a preset mixing ratio, adjusting the pH of the mixed solution to acidic, and then adding the mixed solution into a reactor, wherein the raw materials used to prepare the mixed solution include SnCl4·5H2O, Sb2O3, and La(NO3)3·6H2O; S4, turning on the power supply so that the specified current density is maintained between the cathode and the anode, so that the substances in the mixed solution are deposited on the metal substrate. After the deposition time is preset, a SnO2-Sb2O4-La composite material deposition layer is formed on the metal substrate, and the deposition thickness is 0.2 to 0.8 mm; S5. calcining the metal substrate with the SnO2-Sb2O4-La composite material deposition layer attached thereto, controlling the calcination temperature and time, and obtaining an electrocatalytic electrode with the SnO2-Sb2O4-La composite material layer attached thereto.

5. The method for preparing an electrocatalytic electrode according to claim 4, characterized in that: In step S1, the metal substrate is pretreated by first grinding it with sandpaper, then rinsing the ground metal substrate with deionized water, then immersing it in a NaOH solution for degreasing, then immersing it in an oxalic acid solution for micro-boiling etching, and finally rinsing it with deionized water to obtain a pretreated metal substrate.

6. The method for preparing an electrocatalytic electrode according to claim 4, characterized in that: In step S3, the mixed solution is prepared by sequentially adding SnCl4·5H2O, Sb2O3 and La(NO3)3·6H2O to an isopropanol solution, then sequentially adding hydrochloric acid and citric acid, and then first ultrasonicating and then stirring at a constant temperature to obtain a mixed solution; in the mixed solution, the molar ratio of SnCl4·5H2O, Sb2O3 and La(NO3)3·6H2O is in the range of 100:10:0.5 to 100:10:3, wherein Sn 4+ The concentration is 0.3-0.6 mol / L; the volume ratio of isopropanol, hydrochloric acid and citric acid is 100:2:125, wherein the concentration of hydrochloric acid is 35%-40%, and the concentration of citric acid is 10%-20%.

7. The method for preparing an electrocatalytic electrode according to claim 4, characterized in that: The metal substrate is a titanium substrate with a thickness of 0.5 to 2.0 mm.

8. The method for preparing an electrocatalytic electrode according to claim 4, characterized in that: In step S4, the specified current density range is 10 to 40 mA cm -2 , the deposition time is 15 to 30 minutes.

9. The method for preparing an electrocatalytic electrode according to claim 4, characterized in that: In step S5, the calcination temperature is greater than 500° C., and the calcination time ranges from 1 to 2 hours.

10. A method for treating dye wastewater, using the electrocatalytic electrode as claimed in claim 2, characterized in that: An electrocatalytic electrode is placed as an anode in dye wastewater containing rhodamine B, and a substrate made of the same material as the metal substrate of the electrocatalytic electrode is placed as a cathode in the same dye wastewater containing rhodamine B. The anode and the cathode are respectively connected to the positive electrode and the negative electrode of a power source through electrical conductors; the power source is powered on to degrade the rhodamine B in the dye wastewater.

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