Preparation method of nickel-doped lead dioxide ozone catalytic anode and application thereof

Abstract

This invention discloses a method for preparing a nickel-doped lead dioxide ozone catalytic anode and its application. The method involves using a titanium substrate as the anode and a titanium sheet as the cathode for anodic oxidation, followed by a secondary anodic oxidation using the resulting titanium dioxide nanotube array as the anode and a titanium sheet as the cathode. The newly oxide-layered titanium dioxide nanotube array electrode is placed in a tube furnace and calcined in air. A transition layer titanium dioxide nanotube array electrode is then used as the cathode, and a titanium plate as the anode, for electrochemical reduction in formic acid solution. The resulting electrode with a highly conductive titanium dioxide nanotube array transition layer is then used as the anode, and a titanium sheet as the cathode, for electrodeposition in an acidic electrodeposition solution to obtain a β-PbO2 layer. Finally, a Ti / TNAs / Ni-PbO2 anode is obtained. This anode exhibits high stability, long service life, and can operate continuously without affecting its catalytic activity, showing promising application prospects in the electrocatalytic ozone treatment of organic wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for preparing a nickel-doped lead dioxide ozone catalytic anode and its application. Background Technology

[0002] In recent years, with the rapid development of the economy and society, industries such as new energy, medical, food, papermaking, and printing and dyeing have generated a large amount of organic wastewater. This type of wastewater is characterized by large discharge volume, complex composition, high concentration of organic pollutants, and difficulty in degradation. If it enters the environment without being treated to meet discharge standards, it will pose a serious threat to the ecological environment and human health. However, traditional wastewater treatment methods usually suffer from low treatment efficiency, high investment, and secondary pollution. Ozone is a powerful oxidant and is widely used in wastewater treatment. Ozone molecules are unstable and easily decompose to generate various reactive products, including hydroxyl radicals (•OH). Its standard redox potential is 2.8V. It has advantages such as non-selectivity, fast mineralization speed, and wide applicability, and is considered one of the strongest oxidants in water treatment processes. Since the decomposition product of ozone is reactive oxygen species (ROS), its reactivity is stronger than that of ozone itself. Therefore, promoting ozone decomposition is one of the ways to enhance the degradation of organic matter during ozone treatment.

[0003] In water, ozone decomposition is initiated by •OH, but the reaction between ozone and •OH is relatively slow. Advanced oxidation processes utilize a series of reactions to generate •OH, among which electrochemical advanced oxidation technology has advantages such as small footprint and high processing efficiency. The electrode, as the core component of electrochemical advanced oxidation technology, plays a decisive role in the cost and efficiency of the oxidation process due to its material and performance. Titanium-based lead dioxide electrodes have advantages such as strong electrocatalytic oxidation ability, good corrosion resistance, long service life, and high oxygen evolution potential, and have been widely used. However, titanium substrates are prone to oxidation, significantly increasing electrode resistance and reducing electron transport efficiency. Secondly, the oxide layer reduces the adhesion between the catalyst layer and the titanium substrate, increasing the possibility of catalyst layer detachment. Therefore, the presence of a transition layer (e.g., SnO2-Sb) is used to inhibit oxide film formation and improve the adhesion between the catalyst layer and the titanium substrate. However, the introduction of the transition layer increases the electron transport path, reduces electron transport efficiency, and increases the anode fabrication cost.

[0004] Therefore, there is an urgent need to develop a wastewater treatment technology that combines the advantages of ozone oxidation and advanced electrochemical oxidation, and to prepare an ozone catalytic electrode with simple structure, high oxygen evolution potential, stable electrode performance, long service life and high catalytic efficiency, so as to improve the treatment efficiency of organic wastewater and the comprehensive utilization of resources. Summary of the Invention

[0005] In view of the problems existing in the prior art, the main objective of the present invention is to provide a method for preparing a nickel-doped lead dioxide ozone catalytic anode and its application. The prepared nickel-doped lead dioxide ozone catalytic anode is a nickel-doped lead dioxide ozone catalytic anode (Ti / TNAs / Ni-PbO2) with titanium metal as the substrate and an in-situ self-grown titanium dioxide nanotube array as the transition layer, so as to solve the problems of low electrocatalytic ozone oxidation efficiency, complex anode preparation method, low oxygen evolution potential, unstable electrode performance, and short service life in the prior art.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing a nickel-doped lead dioxide ozone catalytic anode includes the following steps:

[0008] Step S1: Titanium sheet pretreatment: First, the titanium sheet is polished and cleaned, and then etched with acid to obtain a titanium substrate;

[0009] Step S2: Using the titanium substrate obtained in step S1 as the anode and a titanium sheet of the same area as the cathode, titanium dioxide nanotube arrays are prepared by anodic oxidation in an ethylene glycol solution containing ultrapure water and ammonium fluoride.

[0010] Step S3: Using the titanium dioxide nanotube array electrode plate prepared in step S2 as the anode and a titanium sheet of the same area as the cathode, a second anodic oxidation is performed in an ethylene glycol solution containing phosphoric acid to form a new oxide layer between the titanium dioxide nanotube array and the titanium substrate.

[0011] Step S4: Place the titanium dioxide nanotube array electrode with the new oxide layer from step S3 in a tube furnace, calcine it in an air atmosphere, and then cool it naturally to room temperature to obtain a stable titanium dioxide nanotube array transition layer.

[0012] Step S5: Using the titanium dioxide nanotube array electrode with the transition layer from step S4 as the cathode and a titanium plate of the same area as the anode, place it in a formic acid solution for electrochemical reduction to form a stable, highly conductive titanium dioxide nanotube array transition layer.

[0013] Step S6: Using the electrode with a highly conductive titanium dioxide nanotube array transition layer prepared in step S5 as the anode and a titanium sheet of the same area as the cathode, a β-PbO2 layer is electrodeposited in an acidic electrodeposition solution containing lead nitrate, nickel nitrate, potassium fluoride, polytetrafluoroethylene and a small amount of nitric acid, and finally Ti / TNAs / Ni-PbO2 anode is obtained.

[0014] Furthermore, the specific process of titanium sheet pretreatment in step S1 is as follows:

[0015] The titanium sheet is polished using a grinding wheel and sandpaper. The polished titanium sheet is then acid-washed and alkali-washed with sodium hydroxide and sulfuric acid solutions. It is then etched with oxalic acid of a certain concentration. After removal, it is cleaned with deionized water to obtain the titanium substrate.

[0016] Further, in step S1, the titanium sheet is polished using a 120-grit grinding wheel, 600-grit sandpaper, and 1200-grit sandpaper, respectively, until the surface of the titanium sheet is glossy; the polished titanium sheet is then subjected to alkaline washing and degreasing in a 40% sodium hydroxide solution at 25°C for 30 minutes; the alkaline-washed titanium sheet is then subjected to acid washing in a 20% sulfuric acid solution at 60°C for 20 minutes; the acid-washed titanium sheet is then etched in a 15% oxalic acid solution at 80°C for 180 minutes.

[0017] Furthermore, the specific process of step S2 is as follows:

[0018] Using the titanium substrate obtained in step S1 as the anode and a titanium sheet of the same area as the cathode, a titanium dioxide nanotube array is obtained by in-situ self-growth on the pretreated titanium substrate through a single anodic oxidation in an ethylene glycol solution containing 2-4 vol% ultrapure water and 0.5-1.5 wt% ammonium fluoride, followed by electrolysis with 20-30V DC for 4-6 hours.

[0019] Furthermore, the specific process of step S3 is as follows:

[0020] Using the titanium dioxide nanotube array electrode plate prepared in step S2 as the anode and a titanium sheet of the same area as the cathode, a new oxide layer is formed between the titanium dioxide nanotube array and the titanium substrate by secondary anodic oxidation in an ethylene glycol solution containing 5-8 wt% phosphoric acid and electrolysis with 20-30V DC for 0.5-1h.

[0021] Furthermore, the specific process of step S4 is as follows:

[0022] The titanium dioxide nanotube array electrode plate with the new oxide layer in step S3 is placed in a tube furnace at 450~550℃ and a heating rate of 2~4℃ / min and calcined in air atmosphere for 2~4h, and then naturally cooled to room temperature to obtain a stable titanium dioxide nanotube array transition layer.

[0023] Furthermore, the specific process of step S5 is as follows:

[0024] Using the titanium dioxide nanotube array electrode with the transition layer from step S4 as the cathode and a titanium plate of the same area as the anode, the electrode is placed in a 10-20% formic acid solution with a current density of 5-10 mA / cm². 2 Electrochemical reduction is carried out for 5-20 minutes to form a stable, highly conductive titanium dioxide nanotube array transition layer.

[0025] Furthermore, the specific process of step S6 is as follows:

[0026] Using the electrode with a highly conductive titanium dioxide nanotube array transition layer prepared in step S5 as the anode, and a titanium sheet of the same area as the cathode, an acidic electrodeposition solution containing lead nitrate, nickel nitrate, potassium fluoride, polytetrafluoroethylene, and a small amount of nitric acid was prepared, with a current density of 20~40 mA / cm². 2 A β-PbO2 layer was obtained by electrodeposition at 80~90℃ for 1~2h, and finally Ti / TNAs / Ni-PbO2 anode was prepared.

[0027] Further, in step S6, a β-PbO2 active layer electrodeposition solution is prepared by mixing 100 g / L Pb(NO3)2, 1 g / L KF·2H2O, 6 ml / L PTFE, Ni(NO3)2·9H2O and 1.2 ml / L HNO3, wherein the molar ratio of nickel to lead is 1:100~3:100.

[0028] The present invention also proposes an application of the nickel-doped lead dioxide ozone catalytic anode prepared by the method described above in the catalytic ozonation degradation of organic wastewater.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1) This invention prepares a nickel-doped lead dioxide ozone catalytic anode Ti / TNAs / Ni-PbO2 by direct current electro-corrosion, high-temperature calcination in a tubular furnace, and electrodeposition. The nickel-doped lead dioxide ozone catalytic anode and cathode prepared by this invention are placed in a reactor for electrocatalytic ozone treatment of organic wastewater. The catalytic effect of the electric field, metal ions, and hydrogen peroxide generated by the cathode on ozone molecules enhances the ozone treatment effect on organic wastewater. At the same time, the added ozone increases the conductivity of the solution and generates a large amount of active oxygen. The added oxygen is reduced to hydrogen peroxide under electrochemical action, which further reacts with ozone to generate active oxygen.

[0031] 2) The tubular structure of the titanium dioxide nanotube array transition layer in this invention greatly enhances the bonding strength of the active layer. After high-temperature calcination, the titanium dioxide nanotubes are transformed into anatase phase, thus having a more stable structure and better catalytic performance. Before electrodepositing the β-PbO2 active layer, the anatase phase TNAs are electrochemically reduced to convert the TNAs into a relatively highly conductive state.

[0032] 3) Ti / TNAs / Ni-PbO2 has good crystallinity, a large specific surface area and a small grain size (around 39nm). In the catalytic ozone oxidation system, it can make more sufficient contact with ozone molecules, causing them to decompose and generate more •OH groups. The •OH groups attack pollutants to achieve degradation effect, and it has excellent catalytic activity. The anode has good stability and can be used for a long time without reducing its activity.

[0033] 4) Compared with the ozone oxidation system alone, Ti / TNAs / Ni-PbO2 showed good removal rates for both pollutants and chemical oxygen demand (COD) in the catalytic ozone oxidation system;

[0034] 5) Under actual operating current density conditions (20mA / cm²) 2 Under these conditions, the service life of the Ti / TNAs / Ni-PbO2 anode prepared by this invention is 7.99 years, which is higher than the 6.60 years of the Ti / TNAs / PbO2 anode.

[0035] 6) The preparation process of this invention is simple, and it has a high removal rate for three types of organic wastewater and COD in the catalytic ozone oxidation system. Moreover, the anode has high stability and long service life, and can work for a long time without affecting its catalytic activity. It has certain application prospects in the electrocatalytic ozone treatment of organic wastewater. Attached Figure Description

[0036] Figure 1 X-ray diffraction (XRD) pattern of the nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2 prepared in Example 1;

[0037] Figure 2 SEM characterization image of the nickel-doped lead dioxide anode transition layer TNAs prepared in Example 1;

[0038] Figure 3 The image shows the SEM characterization of the nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2 prepared in Example 1.

[0039] Figure 4 shows the degradation experiment of sulfadiazine by catalytic ozone oxidation in Example 1. Figure 4(a) is a schematic diagram of the change curve of sulfadiazine concentration over time, and Figure 4(b) is a schematic diagram of the change curve of COD value over time.

[0040] Figure 5 shows the degradation experiment of potassium acesulfame potassium by catalytic ozone oxidation in Example 2. Figure 5(a) is a schematic diagram of the change curve of potassium acesulfame potassium concentration over time, and Figure 5(b) is a schematic diagram of the change curve of COD value over time.

[0041] Figure 6 shows the degradation experiment of ketoprofen by catalytic ozone oxidation in Example 3. Figure 6(a) is a schematic diagram of the change curve of ketoprofen concentration over time, and Figure 6(b) is a schematic diagram of the change curve of COD value over time.

[0042] Figure 7 This is a comparison of the cyclic voltammetry curves of the Ti / TNAs / Ni-PbO2 anode in Example 1 and the Ti / TNAs / PbO2 anode in Comparative Example 1.

[0043] Figure 8 This is a comparison chart of accelerated service life of the Ti / TNAs / Ni-PbO2 anode in Example 2 and the Ti / TNAs / PbO2 anode in Comparative Example 2. Detailed Implementation

[0044] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited to the scope described. Example 1

[0045] This invention provides a method for preparing a nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2, specifically including the following steps:

[0046] Step S1: The titanium sheet is polished using a 120-grit grinding wheel and 600-grit and 1200-grit sandpaper. It is then degreased by alkaline washing with 40% sodium hydroxide solution at 25°C for 30 minutes. Next, it is acid-washed with 20% sulfuric acid solution at 60°C for 20 minutes. Finally, it is etched with 15% oxalic acid solution at 80°C for 180 minutes. After cleaning with deionized water, the titanium substrate is obtained.

[0047] Step S2: Using the titanium substrate obtained in step S1 as the anode and a titanium sheet of the same area as the cathode, the titanium nanotube array is obtained by anodic oxidation in an ethylene glycol solution containing 2 vol% ultrapure water and 0.5 wt% ammonium fluoride, followed by electrolysis with 20 V DC for 4 h.

[0048] Step S3: Using the titanium dioxide nanotube array electrode plate prepared in step S2 as the anode and a titanium sheet of the same area as the cathode, a secondary anodic oxidation is performed in an ethylene glycol solution containing 5wt% phosphoric acid. Electrolysis is carried out with 20V DC for 0.5h to form a new oxide layer between the titanium dioxide nanotube array and the titanium substrate to eliminate the influence of the fluorine-rich oxide layer and increase the adhesion and conductivity of the titanium dioxide nanotube array.

[0049] Step S4: The prepared titanium dioxide nanotube array electrode plate is placed in a tube furnace at 450℃ and a heating rate of 2℃ / min and calcined in air atmosphere for 2h, and then naturally cooled to room temperature to obtain a stable titanium dioxide nanotube transition layer.

[0050] Step S5: Using the calcined titanium dioxide nanotube array as the cathode and a titanium plate of equal area as the anode, the electrode is placed in a 10% formic acid solution with a current density of 5 mA / cm². 2 Electrochemical reduction was carried out for 5 minutes to form a stable, highly conductive titanium dioxide nanotube transition layer.

[0051] Step S6: Using the electrode plate with the highly conductive titanium dioxide nanotube transition layer prepared in step S5 as the anode, and a titanium sheet of the same area as the cathode, in an environment containing 100 g / L Pb(NO3)2 and 1 g / L KF·2

[0052] In an acidic electrodeposition solution containing H2O, 6 ml / L PPTFE, 0.88 g / L Ni(NO3)2·9H2O, and 1.2 ml / L HNO3, at a current density of 20 mA / cm² 2 A β-PbO2 layer was obtained by electrodeposition at 80℃ for 1 hour, ultimately forming a Ti / TNAs /

[0053] Ni-PbO2 anode.

[0054] The XRD and SEM characterizations of the nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2 prepared in this embodiment are as follows: Figure 1 , Figure 2 and Figure 3 As shown.

[0055] pass Figure 1 It can be seen that the (110) and (101) crystal planes of Ti / TNAs / Ni-PbO2 are very sharp, indicating that it has high crystallinity. Therefore, this anode has high stability and good catalytic activity. According to the Scherrer formula, its grain size is calculated to be about 39 nm.

[0056] from Figure 2 The SEM images show that the anatase TNAs, which serve as the transition layer, are highly ordered, vertically arranged, and uniformly distributed. The tube diameter is about 88 nm and the wall thickness is 8 nm. The β-PbO2 layer is deposited inside and on the surface of the nanotube to form an interlocking structure that increases the mechanical strength of the anode.

[0057] from Figure 3 The SEM images show that the β-PbO2 layer has fewer cracks, the sediment surface is more regular and dense, and the tiny pyramidal protrusions greatly increase its specific surface area, indicating that Ti /

[0058] TNAs / Ni-PbO2 exhibits good catalytic activity in the ozone oxidation degradation of pollutants.

[0059] The nickel-doped lead dioxide ozone catalytic anode Ti / TNAs / Ni-PbO2 prepared by the above method is used to degrade organic wastewater. The specific process is as follows:

[0060] Accurately prepare 0.5L of a 200mg / L sulfamethazine solution, pour it into a glass reactor, and connect the ozone generator. Immerse a nickel-doped lead dioxide anode (Ti / TNAs / Ni-PbO2) and a titanium cathode of equal area into the solution, respectively. Connect a regulated DC power supply and set the current density to 20mA / cm². 2 Simultaneously turn on the power switch and ozone ventilation valve, set the ozone dosage to 32 ml / min and the reaction time to 60 min, and start timing. Take samples at 0, 10, 20, 30, 40, 50, and 60 min. Use a 10 ml syringe with a 0.22 μm organic filter for sampling. The collected water samples are used for COD testing. cr Determination of concentrations of sulfamethoxazole and sulfadiazine.

[0061] A blank control group was set up, and the operation steps were the same as described above, except that the Ti / TNAs / Ni-PbO2 prepared by the above method was not added. The COD under the ozone system alone was observed. cr Changes in concentration and sulfamethoxazole concentration.

[0062] As shown in Figure 4(a), within a reaction time of 60 min, the removal rate of sulfadiazine by the ozone oxidation system alone was 78.10%, while it was 100% in the Ti / TNAs / Ni-PbO2 catalyzed ozone oxidation system, with the degradation efficiency increased by 21.90%.

[0063] As shown in Figure 4(b) regarding COD degradation, the removal rate of the ozone oxidation system alone was 27.98%, while that of the Ti / TNAs / Ni-PbO2 catalyzed ozone oxidation system was 38.74%. This indicates that the presence of Ti / TNAs / Ni-PbO2 can improve the removal rate of sulfadiazine and has good catalytic activity. Example 2

[0064] This invention provides a method for preparing a nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2, specifically including the following steps:

[0065] Step S1: The titanium sheet is polished using a 120-grit grinding wheel and 600-grit and 1200-grit sandpaper. It is then degreased by alkaline washing with 40% sodium hydroxide solution at 25°C for 30 minutes. Next, it is acid-washed with 20% sulfuric acid solution at 60°C for 20 minutes. Finally, it is etched with 15% oxalic acid solution at 80°C for 180 minutes. After cleaning with deionized water, the titanium substrate is obtained.

[0066] Step S2: Using the titanium substrate obtained in step S1 as the anode and a titanium sheet of the same area as the cathode, the titanium nanotube array is obtained by anodic oxidation in an ethylene glycol solution containing 3 vol% ultrapure water and 1.0 wt% ammonium fluoride, followed by electrolysis with 25 V DC for 5 h.

[0067] Step S3: Using the titanium dioxide nanotube array electrode plate prepared in step S2 as the anode and a titanium sheet of the same area as the cathode, a secondary anodic oxidation is performed in an ethylene glycol solution containing 7wt% phosphoric acid. Electrolysis is carried out with 25V DC for 0.8h to form a new oxide layer between the titanium dioxide nanotube array and the titanium substrate to eliminate the influence of the fluorine-rich oxide layer and increase the adhesion and conductivity of the titanium dioxide nanotube array.

[0068] Step S4: The prepared titanium dioxide nanotube array electrode plate is placed in a tube furnace at 500℃ and a heating rate of 3℃ / min and fired in air atmosphere for 3 hours, and then naturally cooled to room temperature to obtain a stable titanium dioxide nanotube transition layer.

[0069] Step S5: Using the calcined titanium dioxide nanotube array as the cathode and a titanium plate of equal area as the anode, place it in a 15% formic acid solution with a current density of 8 mA / cm². 2 Electrochemical reduction was carried out for 10 minutes to form a stable, highly conductive titanium dioxide nanotube transition layer.

[0070] Step S6: Using the electrode plate with the highly conductive titanium dioxide nanotube transition layer prepared in step S5 as the anode, and a titanium sheet of the same area as the cathode, a current density of 30 mA / cm² is applied in an acidic electrodeposition solution containing 100 g / L Pb(NO3)2, 1 g / L KF·2H2O, 6 ml / L PtFE, 1.76 g / L Ni(NO3)2·9H2O, and 1.2 ml / L HNO3. 2 A β-PbO2 layer was obtained by electrodeposition at 85℃ for 1.5h, and finally a Ti / TNAs / Ni-PbO2 anode was prepared.

[0071] The nickel-doped lead dioxide ozone catalytic anode Ti / TNAs / Ni-PbO2 prepared by the above method is used to degrade organic wastewater. The specific process is as follows:

[0072] Accurately prepare 0.5L of a 200mg / L potassium acesulfame potassium solution, pour it into a glass reactor, and connect the ozone generator. Immerse a nickel-doped lead dioxide anode (Ti / TNAs / Ni-PbO2) and a titanium sheet of equal area as the cathode into the solution, connect a regulated DC power supply, and set the current density to 20mA / cm². 2 Simultaneously turn on the power switch and ozone ventilation valve, set the ozone dosage to 40 ml / min and the reaction time to 60 min, and start timing. Take samples at 0, 10, 20, 30, 40, 50, and 60 min. Use a 10 ml syringe with a 0.22 μm organic filter for sampling. The collected water samples are used for COD testing. cr Determination of concentration and potassium acesulfame potassium concentration.

[0073] A blank control group was set up, and the operation steps were the same as described above, except that the Ti / TNAs / Ni-PbO2 prepared by the above method was not added. The COD under the ozone system alone was observed. cr Changes in the concentration of acesulfame potassium and its concentration.

[0074] As shown in Figure 5(a), within a reaction time of 60 min, the removal rate of acesulfame potassium by the ozone oxidation system alone was 79.67%, while that by the Ti / TNAs / Ni-PbO2 catalyzed ozone oxidation system was 98.43%, representing an increase in degradation efficiency of 18.76%.

[0075] As shown in Figure 5(b) regarding COD degradation, the removal rate of the ozone oxidation system alone was 27.75%, while that of the Ti / TNAs / Ni-PbO2 catalyzed ozone oxidation system was 40.78%. This indicates that the presence of Ti / TNAs / Ni-PbO2 can improve the removal rate of acesulfame potassium and has good catalytic activity for different organic wastewaters. Example 3

[0076] This invention provides a method for preparing a nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2, specifically including the following steps:

[0077] Step S1: The titanium sheet is polished using a 120-grit grinding wheel and 600-grit and 1200-grit sandpaper. It is then degreased by alkaline washing with 40% sodium hydroxide solution at 25°C for 30 minutes. Next, it is acid-washed with 20% sulfuric acid solution at 60°C for 20 minutes. Finally, it is etched with 15% oxalic acid solution at 80°C for 180 minutes. After cleaning with deionized water, the titanium substrate is obtained.

[0078] Step S2: Using the titanium substrate obtained in step S1 as the anode and a titanium sheet of the same area as the cathode, the titanium nanotube array is obtained by anodic oxidation in an ethylene glycol solution containing 4 vol% ultrapure water and 1.5 wt% ammonium fluoride, followed by electrolysis with 30 V DC for 6 h.

[0079] Step S3: Using the titanium dioxide nanotube array electrode plate prepared in step S2 as the anode and a titanium sheet of the same area as the cathode, a second anodic oxidation is performed in an ethylene glycol solution containing 8wt% phosphoric acid. Electrolysis is carried out with 30V DC for 1 hour to form a new oxide layer between the titanium dioxide nanotube array and the titanium substrate to eliminate the influence of the fluorine-rich oxide layer and increase the adhesion and conductivity of the titanium dioxide nanotube array.

[0080] Step S4: The prepared titanium dioxide nanotube array electrode plate is placed in a tube furnace at 550℃ and a heating rate of 4℃ / min and fired in air atmosphere for 4 hours, and then naturally cooled to room temperature to obtain a stable titanium dioxide nanotube transition layer.

[0081] Step S5: Using the calcined titanium dioxide nanotube array as the cathode and a titanium plate of equal area as the anode, place it in a 20% formic acid solution with a current density of 10 mA / cm². 2 Electrochemical reduction was carried out for 20 minutes to form a stable, highly conductive titanium dioxide nanotube transition layer.

[0082] Step S6: Using the electrode plate with the highly conductive titanium dioxide nanotube transition layer prepared in step S5 as the anode, and a titanium sheet of the same area as the cathode, a current density of 40 mA / cm² is applied in an acidic electrodeposition solution containing 100 g / L Pb(NO3)2, 1 g / L KF·2H2O, 6 ml / L PtFE, 2.64 g / L Ni(NO3)2.9H2O, and 1.2 ml / L HNO3. 2 A β-PbO2 layer was obtained by electrodeposition at 90℃ for 2 hours, and finally a Ti / TNAs / Ni-PbO2 anode was prepared.

[0083] The nickel-doped lead dioxide ozone catalytic anode Ti / TNAs / Ni-PbO2 prepared by the above method is used to degrade organic wastewater. The specific process is as follows:

[0084] Accurately prepare 0.5L of 200mg / L ketoprofen solution, pour it into a glass reactor, and connect the ozone generator. Immerse a nickel-doped lead dioxide anode (Ti / TNAs / Ni-PbO2) and a titanium sheet of equal area as the cathode in the solution, connect a regulated DC power supply, and set the current density to 20mA / cm². 2 Simultaneously turn on the power switch and ozone ventilation valve, set the ozone dosage to 48 ml / min and the reaction time to 60 min, and start timing. Take samples at 0, 10, 20, 30, 40, 50, and 60 min. Use a 10 ml syringe with a 0.22 μm organic filter for sampling. The collected water samples are used for COD testing. cr Determination of concentration and ketoprofen concentration.

[0085] A blank control group was set up, and the operation steps were the same as described above, except that the Ti / TNAs / Ni-PbO2 prepared by the above method was not added. The COD under the ozone system alone was observed. cr Changes in concentration and ketoprofen concentration.

[0086] As shown in Figure 6(a), within a reaction time of 60 min, the removal rate of ketoprofen by the ozone oxidation system alone was 63.67%, while that by the Ti / TNAs / Ni-PbO2 catalyzed ozone oxidation system was 96.13%, with the degradation efficiency improved by 32.46%.

[0087] As shown in Figure 6(b) regarding COD degradation, the removal rate of the ozone oxidation system alone was 32.75%, while that of the Ti / TNAs / Ni-PbO2 catalyzed ozone oxidation system was 48.61%. This indicates that the presence of Ti / TNAs / Ni-PbO2 can also improve the removal rate of ketoprofen. Comparative Example 1

[0088] The difference from Example 1 is that nickel was not introduced for doping, resulting in a Ti / TNAs / PbO2 anode. Using the obtained Ti / TNAs / PbO2 anode (without nickel doping) and a titanium sheet of the same area as the cathode, sulfamethazine wastewater was degraded.

[0089] The removal of sulfamethazine is shown in Figure 4(a), with a removal rate of 94.58%. The removal of COD is shown in Figure 4(b), with a removal rate of 34.29%. The cyclic voltammetry curves of the Ti / TNAs / PbO2 anode obtained in Comparative Example 1 and the Ti / TNAs / Ni-PbO2 anode obtained in Example 1 are shown in Figure 4(b). Figure 7 As shown.

[0090] Compared with Comparative Example 1, the introduction of nickel as a dopant in Example 1 increased the removal rate of sulfamethazine by 5.42% and the removal rate of COD by 4.50%, indicating that nickel doping can make the electrode grains finer and has a positive effect on the generation of •OH, thereby increasing the rate at which the electrode generates •OH.

[0091] from Figure 7 The results show that the Ti / TNAs / Ni-PbO2 anode exhibits an oxidation peak around 1.65V and a weak reduction peak around 0.91V. These two peaks correspond to the redox reactions of Pb(II) and Pb(IV) at the anode interface, respectively. The oxidation and reduction peaks of the Ti / TNAs / PbO2 anode are around 1.39V and 0.82V, respectively, indicating that both electrodes have good reversibility, but the PbO2-Ni electrode has a higher oxygen evolution potential. Furthermore, the prepared Ti / TNAs / Ni-PbO2 electrode shows a higher peak oxidation current, indicating that nickel doping increases the active surface area of ​​the electrode, thereby enhancing the degradation effect on pollutants.

[0092] Figure 8 To conduct accelerated lifespan experiments in sulfuric acid solution, the voltage changes of both electrodes over time were recorded. The results showed that the accelerated lifespan of the Ti / TNAs / Ni-PbO2 anode was 64 h, higher than the 52 h of the Ti / TNAs / PbO2 anode. Empirical formulas indicate that under actual operating current density conditions (20 mA / cm²), the accelerated lifespan of the Ti / TNAs / Ni-PbO2 anode is [not specified in the original text]. 2 Under these conditions, the Ti / TNAs / Ni-PbO2 anode can operate for 7.99 years, and the Ti / TNAs / PbO2 anode for 6.60 years. Nickel doping significantly improves electrode lifespan. Combined with SEM and XRD analysis, this is likely due to the reduced surface grain size and a more dense and complete β-PbO2 active layer. This dense structure effectively prevents solution from penetrating into the β-PbO2 active layer through cracks, inhibiting the erosion of the electrode by active oxides such as •OH. Comparative Example 2

[0093] The difference from Example 2 is that iron is introduced for doping, ultimately obtaining a Ti / TNAs / Fe-PbO2 anode. Using the obtained iron-doped Ti / TNAs / Fe-PbO2 anode, and a titanium sheet of the same area as the cathode, potassium acesulfame potassium wastewater is degraded.

[0094] The removal of potassium acesulfame potassium is shown in Figure 5(a), with a removal rate of 92.74%, while the removal of COD is shown in Figure 5(b), with a removal rate of 36.47%.

[0095] Compared with Comparative Example 2, Example 2 introduced nickel instead of iron for doping. After doping, the removal rate of acesulfame potassium increased by 5.69%, and the removal rate of COD increased by 4.31%. This indicates that the doping of nickel can react with ozone faster than that of iron, has a better catalytic effect on ozone, and improves the degradation effect of pollutants.

Claims

1. A method for preparing a nickel-doped lead dioxide ozone catalytic anode, characterized in that... Includes the following steps: Step S1: Titanium sheet pretreatment: First, the titanium sheet is polished and cleaned, and then etched with acid to obtain a titanium substrate; Step S2: Using the titanium substrate obtained in step S1 as the anode and a titanium sheet of the same area as the cathode, titanium dioxide nanotube arrays are prepared by anodic oxidation in an ethylene glycol solution containing ultrapure water and ammonium fluoride. Step S3: Using the titanium dioxide nanotube array electrode plate prepared in step S2 as the anode and a titanium sheet of the same area as the cathode, a second anodic oxidation is performed in an ethylene glycol solution containing phosphoric acid to form a new oxide layer between the titanium dioxide nanotube array and the titanium substrate. Step S4: Place the titanium dioxide nanotube array electrode with the new oxide layer from step S3 in a tube furnace, calcine it in an air atmosphere, and then cool it naturally to room temperature to obtain a stable titanium dioxide nanotube array transition layer. Step S5: Using the titanium dioxide nanotube array electrode with the transition layer from step S4 as the cathode and a titanium plate of the same area as the anode, place it in a formic acid solution for electrochemical reduction to form a stable, highly conductive titanium dioxide nanotube array transition layer. Step S6: Using the electrode with a highly conductive titanium dioxide nanotube array transition layer prepared in step S5 as the anode and a titanium sheet of the same area as the cathode, a β-PbO2 layer is electrodeposited in an acidic electrodeposition solution containing lead nitrate, nickel nitrate, potassium fluoride, polytetrafluoroethylene and a small amount of nitric acid, and finally Ti / TNAs / Ni-PbO2 anode is obtained.

2. The method for preparing a nickel-doped lead dioxide ozone catalytic anode according to claim 1, characterized in that... The specific process of titanium sheet pretreatment in step S1 is as follows: The titanium sheet is polished using a grinding wheel and sandpaper. The polished titanium sheet is then acid-washed and alkali-washed with sodium hydroxide and sulfuric acid solutions. It is then etched with oxalic acid of a certain concentration. After removal, it is cleaned with deionized water to obtain the titanium substrate.

3. The method for preparing a nickel-doped lead dioxide ozone catalytic anode according to claim 2, characterized in that... In step S1, the titanium sheet is polished using a 120-grit grinding wheel, 600-grit sandpaper, and 1200-grit sandpaper until the surface of the titanium sheet is shiny. After polishing, the titanium sheet is subjected to alkaline washing and degreasing in a 40% sodium hydroxide solution at 25°C for 30 minutes. After alkaline washing, the titanium sheet is subjected to acid washing in a 20% sulfuric acid solution at 60°C for 20 minutes. After acid washing, the titanium sheet is etched in a 15% oxalic acid solution at 80°C for 180 minutes.

4. The method for preparing a nickel-doped lead dioxide ozone catalytic anode according to claim 1, characterized in that... The specific process of step S2 is as follows: Using the titanium substrate obtained in step S1 as the anode and a titanium sheet of the same area as the cathode, a titanium dioxide nanotube array is obtained by in-situ self-growth on the pretreated titanium substrate through a single anodic oxidation in an ethylene glycol solution containing 2-4 vol% ultrapure water and 0.5-1.5 wt% ammonium fluoride, followed by electrolysis with 20-30V DC for 4-6 hours.

5. The method for preparing a nickel-doped lead dioxide ozone catalytic anode according to claim 1, characterized in that... The specific process of step S3 is as follows: Using the titanium dioxide nanotube array electrode plate prepared in step S2 as the anode and a titanium sheet of the same area as the cathode, a new oxide layer is formed between the titanium dioxide nanotube array and the titanium substrate by secondary anodic oxidation in an ethylene glycol solution containing 5-8 wt% phosphoric acid and electrolysis with 20-30V DC for 0.5-1h.

6. The method for preparing a nickel-doped lead dioxide ozone catalytic anode according to claim 1, characterized in that... The specific process of step S4 is as follows: The titanium dioxide nanotube array electrode plate with the new oxide layer in step S3 is placed in a tube furnace at 450~550℃ and a heating rate of 2~4℃ / min and calcined in air atmosphere for 2~4h, and then naturally cooled to room temperature to obtain a stable titanium dioxide nanotube array transition layer.

7. The method for preparing a nickel-doped lead dioxide ozone catalytic anode according to claim 1, characterized in that... The specific process of step S5 is as follows: Using the titanium dioxide nanotube array electrode with the transition layer from step S4 as the cathode and a titanium plate of the same area as the anode, the electrode is placed in a 10-20% formic acid solution with a current density of 5-10 mA / cm². 2 Electrochemical reduction is carried out for 5-20 minutes to form a stable, highly conductive titanium dioxide nanotube array transition layer.

8. The method for preparing a nickel-doped lead dioxide ozone catalytic anode according to claim 1, characterized in that... The specific process of step S6 is as follows: Using the electrode with a highly conductive titanium dioxide nanotube array transition layer prepared in step S5 as the anode, and a titanium sheet of the same area as the cathode, an acidic electrodeposition solution containing lead nitrate, nickel nitrate, potassium fluoride, polytetrafluoroethylene, and a small amount of nitric acid was prepared, with a current density of 20~40 mA / cm². 2 A β-PbO2 layer was obtained by electrodeposition at 80~90℃ for 1~2h, and finally Ti / TNAs / Ni-PbO2 anode was prepared.

9. The method for preparing a nickel-doped lead dioxide ozone catalytic anode according to claim 8, characterized in that... In step S6, a β-PbO2 active layer electrodeposition solution is prepared by mixing 100 g / L Pb(NO3)2, 1 g / L KF·2H2O, 6 ml / L PTFE, Ni(NO3)2·9H2O and 1.2 ml / L HNO3, wherein the molar ratio of nickel to lead is 1:100~3:

100.

10. The application of a nickel-doped lead dioxide ozone catalytic anode prepared by the method according to any one of claims 1-9 in the catalytic ozonation degradation of organic wastewater.

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