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

Abstract

The invention discloses a preparation method and application of a nickel-doped lead dioxide ozone catalytic anode, a titanium substrate is used as an anode, a titanium sheet is used as a cathode for anodic oxidation, an obtained titanium dioxide nanotube array is used as an anode, a titanium sheet is used as a cathode for secondary anodic oxidation, and the nickel-doped lead dioxide ozone catalytic anode is obtained. And putting the obtained titanium dioxide nanotube array electrode of the new oxide layer into a tubular furnace, calcining in an air atmosphere, taking the titanium dioxide nanotube array electrode of the transition layer as a cathode, taking a titanium plate as an anode, and performing electrochemical reduction in a formic acid solution to obtain the titanium dioxide nanotube array electrode of the transition layer. The obtained electrode with the high-conductivity titanium dioxide nanotube array transition layer serves as an anode, a titanium sheet serves as a cathode, electrodeposition is carried out in an acid electrodeposition solution to obtain a beta-PbO2 layer, and finally the Ti / TNAs / Ni-PbO2 anode is prepared, the anode is high in stability and long in service life and can work for a long time without affecting the catalytic activity of the anode, and the application range of the Ti / TNAs / Ni-PbO2 anode is wide. The method has a certain application prospect in the aspect of electro-catalytic ozone treatment of organic wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a preparation method and application of a nickel-doped lead dioxide ozone catalytic anode. Background Art

[0002] In recent years, with the rapid economic and social development, industries such as new energy, healthcare, food, papermaking, and printing and dyeing have generated large quantities of organic wastewater. This wastewater is characterized by large discharge volumes, complex composition, high concentrations of organic pollutants, and difficulty in degradation. If it enters the environment without being treated to meet discharge standards, it poses a serious threat to the ecological environment and human health. However, traditional wastewater treatment methods often suffer from low treatment efficiency, high investment, and secondary pollution. Ozone is a powerful oxidant widely used in wastewater treatment. Ozone molecules are unstable and readily decompose to form various reactive products, including hydroxyl radicals (•OH). Its standard redox potential is 2.8V. It is considered one of the most powerful oxidants in water treatment processes due to its non-selective nature, rapid mineralization, and wide applicability. Because ozone decomposition products are reactive oxygen species (ROS), which are more reactive than ozone itself, promoting ozone decomposition is one way 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 produce •OH. Electrochemical advanced oxidation technology, among them, offers advantages such as a small footprint and high processing efficiency. Electrodes, as core components of electrochemical advanced oxidation technology, have a decisive influence on the cost and efficiency of the oxidation process due to their material and performance. Titanium-based lead dioxide electrodes have been widely used due to their strong electrocatalytic oxidation capacity, excellent corrosion resistance, long service life, and high oxygen evolution potential. However, the titanium substrate is susceptible to oxidation, significantly increasing the electrode's resistance and reducing electron transfer efficiency. Furthermore, the oxide layer reduces the adhesion between the catalytic layer and the titanium substrate, increasing the likelihood of the catalytic layer detaching. Therefore, a transition layer (such as SnO2-Sb) is used to inhibit the formation of an oxide film and improve the adhesion between the catalytic layer and the titanium substrate. However, the introduction of a transition layer increases electron transfer paths, reduces electron transfer efficiency, and increases the cost of anode preparation.

[0004] Therefore, there is an urgent need to develop a wastewater treatment technology that combines the advantages of ozone oxidation and electrochemical advanced oxidation, and at the same time prepare ozone catalytic electrodes 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 purpose of the present invention is to provide a preparation method and application of a nickel-doped lead dioxide ozone catalytic anode. The prepared nickel-doped lead dioxide ozone catalytic anode is a nickel-doped lead dioxide ozone catalytic anode (Ti / TNAs / Ni-PbO2) with a titanium metal as a substrate and an in-situ self-grown titanium dioxide nanotube array as a 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 object, the technical solution of the present invention is as follows: A method for preparing a nickel-doped lead dioxide ozone catalytic anode comprises the following steps: Step S1: Pretreatment of the titanium sheet: 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 an anode and a titanium sheet of the same size as a cathode, anodization is performed in an ethylene glycol solution containing ultrapure water and ammonium fluoride to prepare a titanium dioxide nanotube array; Step S3: Using the titanium dioxide nanotube array plate prepared in step S2 as the anode and a titanium sheet of the same size as the cathode, secondary 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: placing the titanium dioxide nanotube array electrode with a new oxide layer in step S3 in a tube furnace, calcining it in an air atmosphere, and then naturally cooling it to room temperature to obtain a stable titanium dioxide nanotube array transition layer; Step S5: The titanium dioxide nanotube array electrode with the transition layer prepared in step S4 is used as a cathode, and a titanium plate of the same size is used as an anode, and the electrodes are placed in a formic acid solution for electrochemical reduction to form a stable and 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 size 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 to finally obtain a Ti / TNAs / Ni-PbO2 anode.

[0007] Furthermore, the specific process of the titanium sheet pretreatment in step S1 is as follows: The titanium sheet is polished using a grinding wheel machine and sandpaper, pickled and alkaline washed with sodium hydroxide and sulfuric acid solutions, etched with oxalic acid of a certain concentration, taken out and cleaned with deionized water to obtain a titanium substrate.

[0008] Furthermore, in step S1, the titanium sheet is polished using a 120-mesh grinding wheel, 600-mesh sandpaper, and 1200-mesh sandpaper, respectively, until the surface of the titanium sheet is glossy; the polished titanium sheet is alkali-washed and degreased in a 40% sodium hydroxide solution at 25° C. for 30 minutes; the alkali-washed titanium sheet is pickled in a 20% sulfuric acid solution at 60° C. for 20 minutes; the pickled titanium sheet is etched in a 15% oxalic acid solution at 80° C. for 180 minutes.

[0009] Furthermore, the specific process of step S2 is as follows: The titanium substrate obtained in step S1 is used as the anode, and a titanium sheet of the same size is used as the cathode. A single anodic oxidation is performed in an ethylene glycol solution containing 2-4 vol% ultrapure water and 0.5-1.5 wt% ammonium fluoride, and then electrolyzed with a 20-30 V direct current for 4-6 hours to allow titanium dioxide nanotube arrays to be in situ self-grown on the pretreated titanium substrate.

[0010] Furthermore, the specific process of step S3 is as follows: The titanium dioxide nanotube array plate prepared in step S2 is used as the anode, and a titanium sheet of the same size is used as the cathode. Secondary anodic oxidation is performed in an ethylene glycol solution containing 5-8 wt% phosphoric acid, and electrolysis is performed at 20-30 V DC for 0.5-1 h to form a new oxide layer between the titanium dioxide nanotube array and the titanium substrate.

[0011] Furthermore, the specific process of step S4 is as follows: The titanium dioxide nanotube array electrode plate with a new oxide layer in step S3 is placed in a tube furnace at 450-550°C and a heating rate of 2-4°C / min in an air atmosphere and calcined for 2-4 hours, and then naturally cooled to room temperature to obtain a stable titanium dioxide nanotube array transition layer.

[0012] Furthermore, the specific process of step S5 is as follows: The titanium dioxide nanotube array electrode with a transition layer in step S4 was used as the cathode, and a titanium plate of the same size was used as the anode. The solution was placed in a 10-20% formic acid solution at a current density of 5-10 mA / cm 2 , and electrochemical reduction is carried out for 5 to 20 minutes to form a stable and highly conductive titanium dioxide nanotube array transition layer.

[0013] Furthermore, the specific process of step S6 is as follows: The electrode with the highly conductive titanium dioxide nanotube array transition layer prepared in step S5 was used as the anode, and a titanium sheet of the same size was used as the cathode. In an acidic electrodeposition solution containing lead nitrate, nickel nitrate, potassium fluoride, polytetrafluoroethylene and a small amount of nitric acid, the current density was 20-40 mA / cm 2 , the β-PbO2 layer was obtained by electrodeposition at 80~90℃ for 1~2h, and finally the Ti / TNAs / Ni-PbO2 anode was prepared.

[0014] Furthermore, in step S6, 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 are prepared to prepare a β-PbO2 active layer electrodeposition solution, wherein the molar ratio of nickel to lead is 1:100~3:100.

[0015] The present invention also proposes an application of a nickel-doped lead dioxide ozone catalytic anode prepared by the method in catalytic ozonation degradation of organic wastewater.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The present invention prepares a nickel-doped lead dioxide ozone catalytic anode Ti / TNAs / Ni-PbO2 by direct current corrosion, high-temperature calcination in a tubular furnace, and electrodeposition. The nickel-doped lead dioxide ozone catalytic anode and cathode prepared by the method of the present invention are placed in a reactor to electrocatalytically treat organic wastewater with ozone. The catalytic effect of the electric field, metal ions, and hydrogen peroxide generated by the cathode on ozone molecules enhances the ozone treatment effect of the 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 obtains electrons under the electrochemical action and is reduced to hydrogen peroxide, which further reacts with ozone to generate active oxygen. 2) The tubular structure of the titanium dioxide nanotube array transition layer in the present invention greatly enhances the bonding strength of the active layer. After high-temperature calcination, the titanium dioxide nanotubes are converted to an anatase phase, resulting in a more stable structure and better catalytic performance. Before electrodeposition of the β-PbO2 active layer, the anatase phase TNAs are electrochemically reduced to convert them to a relatively highly conductive state. 3) Ti / TNAs / Ni-PbO2 has good crystallinity, a large specific surface area, and a small grain size (approximately 39 nm). In the catalytic ozone oxidation system, it can more fully contact ozone molecules, causing them to decompose and produce more •OH groups. These •OH groups attack pollutants to achieve degradation, resulting in excellent catalytic activity. This anode is stable and can be used for long periods of time without loss of activity. 4) Compared with the ozone oxidation system alone, Ti / TNAs / Ni-PbO2 showed good removal efficiency for pollutants and chemical oxygen demand (COD) in the catalytic ozone oxidation system; 5) Under actual working current density conditions (20mA / cm 2 ), the service life of the Ti / TNAs / Ni-PbO2 anode prepared by the present invention is 7.99 years, which is higher than 6.60 years of the Ti / TNAs / PbO2 anode; 6) The preparation process of the present invention is simple, and it has a high removal rate for the three organic wastewaters and COD in the catalytic ozone oxidation system. In addition, the anode has high stability and a 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 X-ray diffraction analysis (XRD) of the nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2 prepared in Example 1; Figure 2 This is a SEM characterization image of the nickel-doped lead dioxide anode transition layer TNAs prepared in Example 1; Figure 3 This is a SEM characterization image of the nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2 prepared in Example 1; FIG4 is a diagram of the degradation experiment of sulfamethazine by catalytic ozone oxidation in Example 1, wherein FIG4(a) is a schematic diagram of the curve of sulfamethazine concentration changing with time, and FIG4(b) is a schematic diagram of the curve of COD value changing with time; FIG5 is a diagram showing the degradation experiment of acesulfame potassium by catalytic ozone oxidation in Example 2, wherein FIG5(a) is a schematic diagram showing the curve of the change of acesulfame potassium concentration over time, and FIG5(b) is a schematic diagram showing the curve of the change of COD value over time; FIG6 is a diagram of the degradation experiment of ketoprofen by catalytic ozone oxidation in Example 3, wherein FIG6(a) is a schematic diagram of the curve of ketoprofen concentration changing with time, and FIG6(b) is a schematic diagram of the curve of COD value changing with time; Figure 7 Comparison of cyclic voltammetry curves of the Ti / TNAs / Ni-PbO2 anode in Example 1 and the Ti / TNAs / PbO2 anode in Comparative Example 1; Figure 8 This is a comparison chart of the accelerated service life of the Ti / TNAs / Ni-PbO2 anode in Example 2 and the Ti / TNAs / PbO2 anode in Comparative Example 2. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited to the described scope. Example 1

[0019] The present invention provides a method for preparing a nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2, which specifically comprises the following steps: Step S1: The titanium sheet was polished using a 120-mesh grinding wheel and 600-mesh and 1200-mesh sandpapers, then alkaline-washed and degreased with a 40% sodium hydroxide solution at 25°C for 30 minutes, then pickled with a 20% sulfuric acid solution at 60°C for 20 minutes, and then etched with a 15% oxalic acid solution at 80°C for 180 minutes. The titanium sheet was then removed and cleaned with deionized water 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 size as the cathode, a single anodic oxidation was performed in an ethylene glycol solution containing 2 vol% ultrapure water and 0.5 wt% ammonium fluoride, followed by electrolysis at 20 V DC for 4 h, thereby in situ self-growing a titanium dioxide nanotube array on the pretreated titanium substrate; Step S3: Using the titanium dioxide nanotube array plate prepared in step S2 as the anode and a titanium sheet of equal size as the cathode, secondary anodic oxidation was performed in an ethylene glycol solution containing 5 wt% phosphoric acid, and electrolysis was performed at 20 V DC for 0.5 h 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; Step S4: The prepared titanium dioxide nanotube array electrode plate is placed in a tube furnace at 450°C with a heating rate of 2°C / min in an air atmosphere for calcination for 2 hours, and then naturally cooled to room temperature to obtain a stable titanium dioxide nanotube transition layer; Step S5: The titanium dioxide nanotube array electrode formed after calcination is used as the cathode and the titanium plate of the same area is used as the anode, and the electrodes are placed in a 10% formic acid solution at a current density of 5 mA / cm 2 , electrochemical reduction was performed for 5 min to form a stable and highly conductive titanium dioxide nanotube transition layer; Step S6: using the plate with the highly conductive titanium dioxide nanotube transition layer prepared in step S5 as the anode and a titanium sheet of the same size as the cathode in a solution containing 100g / L Pb(NO3)2, 1g / L KF·2 The electroplating was carried out in an acidic electroplating solution of H2O, 6ml / LPTFE, 0.88g / LNi(NO3)2.9H2O and 1.2ml / LHNO3 at a current density of 20mA / cm 2, β-PbO2 layer was obtained by electrodeposition at 80℃ for 1h, and finally Ti / TNAs / Ni-PbO2 anode.

[0020] The XRD and SEM characterizations of the nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2 prepared in this example are as follows: Figure 1 、 Figure 2 and Figure 3 shown.

[0021] pass Figure 1 It can be seen that the (110) and (101) crystal planes of Ti / TNAs / Ni-PbO2 are very sharp, indicating high crystallinity. Therefore, the anode has high stability and good catalytic activity. The grain size is calculated according to the Scherrer formula, and its average particle size is about 39nm.

[0022] from Figure 2 The SEM image shows that the anatase TNAs as the transition layer are highly ordered, vertically arranged and evenly distributed, with a tube diameter of about 88 nm and a wall thickness of 8 nm. The β-PbO2 layer is deposited inside and on the surface of the nanotubes to form an interlocking structure to increase the mechanical strength of the anode.

[0023] from Figure 3 It can be seen from the SEM image that the β-PbO2 layer has fewer cracks, the surface of the deposit is more regular and dense, and the presence of tiny protrusions in the form of pyramids greatly increases its specific surface area, which indicates that the Ti / TNAs / Ni-PbO2 has good catalytic activity in catalyzing ozone oxidation and degradation of pollutants.

[0024] 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: Accurately prepare 0.5L of 200mg / L sulfamethazine solution, pour it into a glass reactor, and connect it to the ozone generator. Immerse the nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2 and a titanium sheet of the same area as the cathode in the solution. Connect a regulated DC power supply and set the current density to 20mA / cm 2 Turn on the power switch and ozone ventilation valve at the same time, set the ozone dosage to 32ml / min, the reaction time to 60min, and start timing at the same time. Sampling was performed at 0, 10, 20, 30, 40, 50, and 60min. A 10ml syringe with an organic filter with a pore size of 0.22um was used for sampling. The water samples were used for COD cr Determination of concentrations of sulfamethazine and sulfamethazine.

[0025] A blank control group was set up, and the operation steps were the same as above, except that the Ti / TNAs / Ni-PbO2 prepared by the above method was not added, and the COD under the ozone system alone was observed. cr The changes of sulfamethazine concentration and sulfamethazine concentration.

[0026] As can be seen from Figure 4 (a), within the reaction time of 60 minutes, the removal rate of sulfamethazine in the ozone oxidation system alone was 78.10%, while in the Ti / TNAs / Ni-PbO2 catalytic ozone oxidation system it was 100%, and the degradation efficiency was increased by 21.90%.

[0027] Judging from the COD degradation in Figure 4 (b), the removal rate of the ozone oxidation system alone is 27.98%, while in the Ti / TNAs / Ni-PbO2 catalytic ozone oxidation system it is 38.74%. This shows that the presence of Ti / TNAs / Ni-PbO2 can improve the removal rate of sulfamethazine and has good catalytic activity. Example 2

[0028] The present invention provides a method for preparing a nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2, which specifically comprises the following steps: Step S1: The titanium sheet was polished using a 120-mesh grinding wheel and 600-mesh and 1200-mesh sandpapers, then alkaline-washed and degreased with a 40% sodium hydroxide solution at 25°C for 30 minutes, then pickled with a 20% sulfuric acid solution at 60°C for 20 minutes, and then etched with a 15% oxalic acid solution at 80°C for 180 minutes. The titanium sheet was then removed and cleaned with deionized water 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 size as the cathode, a single anodic oxidation was performed in an ethylene glycol solution containing 3 vol% ultrapure water and 1.0 wt% ammonium fluoride, followed by electrolysis at 25 V DC for 5 h, thereby in situ self-growing a titanium dioxide nanotube array on the pretreated titanium substrate; Step S3: Using the titanium dioxide nanotube array plate prepared in step S2 as the anode and a titanium sheet of equal size as the cathode, secondary anodic oxidation was performed in an ethylene glycol solution containing 7 wt % phosphoric acid, and electrolysis was performed at 25 V DC for 0.8 h 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; Step S4: The prepared titanium dioxide nanotube array electrode plate is placed in a tube furnace at 500°C with a heating rate of 3°C / min in an air atmosphere for 3 hours, and then naturally cooled to room temperature to obtain a stable titanium dioxide nanotube transition layer; Step S5: The titanium dioxide nanotube array plate formed after calcination is used as the cathode and the titanium plate of the same area is used as the anode. The plates are placed in a 15% formic acid solution at a current density of 8 mA / cm 2 , electrochemical reduction was performed for 10 min to form a stable and highly conductive titanium dioxide nanotube transition layer; Step S6: Using the electrode with the highly conductive titanium dioxide nanotube transition layer prepared in step S5 as the anode and a titanium sheet of the same size as the cathode, the electrodeposition was carried out 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 at a current density of 30 mA / cm 2 , the β-PbO2 layer was obtained by electrodeposition at 85℃ for 1.5h, and finally the Ti / TNAs / Ni-PbO2 anode was prepared.

[0029] 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: Accurately prepare 0.5L of 200mg / L acesulfame potassium solution, pour it into the glass reactor, and connect the ozone generator. Immerse the nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2 and a titanium sheet of the same area as the cathode in the solution. Connect a regulated DC power supply and set the current density to 20mA / cm 2 Turn on the power switch and ozone ventilation valve at the same time, set the ozone dosage to 40ml / min, the reaction time to 60min, and start timing at the same time. Sampling was performed using a 10ml syringe with an organic filter with a pore size of 0.22um. The water samples were used for COD cr Determination of concentrations of acesulfame K and acesulfame K.

[0030] A blank control group was set up, and the operation steps were the same as above, except that the Ti / TNAs / Ni-PbO2 prepared by the above method was not added, and the COD under the ozone system alone was observed. cr The changes in the concentration of acesulfame K and the concentration of acesulfame K were observed.

[0031] As can be seen from Figure 5(a), within a reaction time of 60 min, the removal efficiency of acesulfame potassium by the ozone oxidation system alone was 79.67%, while that in the Ti / TNAs / Ni-PbO2 catalytic ozone oxidation system was 98.43%, and the degradation efficiency was increased by 18.76%; Judging from the COD degradation in Figure 5 (b), the removal rate of the ozone oxidation system alone is 27.75%, while in the Ti / TNAs / Ni-PbO2 catalytic ozone oxidation system it is 40.78%. This shows 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

[0032] The present invention provides a method for preparing a nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2, which specifically comprises the following steps: Step S1: The titanium sheet was polished using a 120-mesh grinding wheel and 600-mesh and 1200-mesh sandpapers, then alkaline-washed and degreased with a 40% sodium hydroxide solution at 25°C for 30 minutes, then pickled with a 20% sulfuric acid solution at 60°C for 20 minutes, and then etched with a 15% oxalic acid solution at 80°C for 180 minutes. The titanium sheet was then removed and cleaned with deionized water 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 size as the cathode, a single anodic oxidation was performed in an ethylene glycol solution containing 4 vol% ultrapure water and 1.5 wt% ammonium fluoride, followed by electrolysis at 30 V DC for 6 h, thereby in situ self-growing a titanium dioxide nanotube array on the pretreated titanium substrate; Step S3: Using the titanium dioxide nanotube array plate prepared in step S2 as the anode and a titanium sheet of the same size as the cathode, secondary anodic oxidation was performed in an ethylene glycol solution containing 8 wt % phosphoric acid, and electrolysis was performed at 30 V 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; Step S4: The prepared titanium dioxide nanotube array electrode plate is placed in a tube furnace at 550°C with a heating rate of 4°C / min in an air atmosphere for 4 hours, and then naturally cooled to room temperature to obtain a stable titanium dioxide nanotube transition layer; Step S5: The titanium dioxide nanotube array plate formed after calcination is used as the cathode and the titanium plate of the same area is used as the anode. The plates are placed in a 20% formic acid solution at a current density of 10 mA / cm 2 , electrochemical reduction was performed for 20 min to form a stable and highly conductive titanium dioxide nanotube transition layer; Step S6: Using the electrode with the highly conductive titanium dioxide nanotube transition layer prepared in step S5 as the anode and a titanium sheet of the same size as the cathode, the electrode was placed in an acidic electrodeposition solution containing 100 g / L PB(NO3)2, 1 g / L KF·2H2O, 6 ml / L TFE, 2.64 g / L Ni(NO3)2.9H2O, and 1.2 ml / L HNO3 at a current density of 40 mA / cm 2 , the β-PbO2 layer was obtained by electrodeposition at 90℃ for 2h, and finally the Ti / TNAs / Ni-PbO2 anode was prepared.

[0033] 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: Accurately prepare 0.5L of 200mg / L ketoprofen solution, pour it into the glass reactor, and connect the ozone generator. Immerse the nickel-doped lead dioxide anode Ti / TNAs / Ni-PbO2 and the cathode titanium sheet of the same area in the solution, connect a regulated DC power supply, and set the current density to 20mA / cm 2 Turn on the power switch and ozone ventilation valve at the same time, set the ozone dosage to 48ml / min, the reaction time to 60min, and start timing at the same time. Sampling was performed using a 10ml syringe with an organic filter with a pore size of 0.22um. The water samples were used for COD cr Determination of concentrations of ketoprofen and acetaminophen.

[0034] A blank control group was set up, and the operation steps were the same as above, except that the Ti / TNAs / Ni-PbO2 prepared by the above method was not added, and the COD under the ozone system alone was observed. cr The changes of ketoprofen concentration and acetaminophen concentration.

[0035] As can be seen from Figure 6 (a), within the reaction time of 60 minutes, the removal rate of ketoprofen in the ozone oxidation system alone was 63.67%, while in the Ti / TNAs / Ni-PbO2 catalytic ozone oxidation system it was 96.13%, and the degradation efficiency was increased by 32.46%.

[0036] From the COD degradation data in Figure 6 (b), the removal rate of the ozone oxidation system alone is 32.75%, while in the Ti / TNAs / Ni-PbO2 catalyzed ozone oxidation system it is 48.61%. This shows that the presence of Ti / TNAs / Ni-PbO2 can also improve the removal rate of ketoprofen. Comparative Example 1

[0037] The difference from Example 1 is that no nickel was introduced for doping, resulting in a Ti / TNAs / PbO2 anode. The obtained Ti / TNAs / PbO2 anode without nickel doping was used with a titanium sheet of equal area as a cathode to degrade sulfamethazine wastewater.

[0038] 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 (a). Figure 7 shown.

[0039] Compared with Comparative Example 1, Example 1 introduces nickel element for doping. After doping, the removal rate of sulfamethazine is increased by 5.42%, and the removal rate of COD is increased by 4.50%, indicating that the doping of nickel element can make the grains of the electrode finer, have a positive effect on the production of •OH, and can increase the rate at which the electrode produces •OH.

[0040] from Figure 7 It can be seen that the Ti / TNAs / Ni-PbO2 anode has an oxidation peak near 1.65V and a weak reduction peak near 0.91V. These two peaks correspond to the redox reactions of Pb(II) and Pb(IV) at the anode interface, respectively. The oxidation peak and reduction peak of the Ti / TNAs / PbO2 anode are near 1.39V and 0.82V, indicating that both electrodes have good reversibility, but the PbO2-Ni electrode has a higher oxygen evolution potential. In addition, it can be observed that the prepared Ti / TNAs / Ni-PbO2 has a higher peak oxidation current, indicating that doping nickel has the effect of increasing the active surface area of ​​the electrode, thereby improving the degradation effect of pollutants on this basis.

[0041] Figure 8 To conduct an accelerated life test in sulfuric acid solution, the voltage of the two electrodes was recorded over time. The results showed that the accelerated life of the Ti / TNAs / Ni-PbO2 anode was 64 hours, which was higher than the 52 hours of the Ti / TNAs / PbO2 anode. According to the empirical formula, under the actual working current density conditions (20mA / cm 2 ), the Ti / TNAs / Ni-PbO2 anode can operate for 7.99 years, while the Ti / TNAs / PbO2 anode can operate for 6.60 years. Nickel doping significantly improves electrode life. Combined SEM and XRD analysis suggests this may be due to the reduced surface grain size, resulting in a denser and more complete β-PbO2 active layer. This dense structure effectively prevents solution penetration through cracks into the β-PbO2 active layer, inhibiting the corrosion of active oxides such as •OH into the electrode. Comparative Example 2

[0042] The difference from Example 2 is that iron is introduced for doping to obtain a Ti / TNAs / Fe-PbO2 anode. The obtained iron-doped Ti / TNAs / Fe-PbO2 anode was used with a titanium sheet of equal area as a cathode to degrade acesulfame potassium wastewater.

[0043] The removal of potassium acesulfame is shown in Figure 5(a), with a removal rate of 92.74%. The removal of COD is shown in Figure 5(b), with a removal rate of 36.47%.

[0044] Compared with Comparative Example 2, Example 2 introduces nickel element instead of iron element for doping. After doping, the removal rate of acesulfame potassium is increased by 5.69%, and the removal rate of COD is increased by 4.31%, indicating that the doping of nickel element can react with ozone faster than that of iron element, 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 The steps include: Step S1: Pretreatment of the titanium sheet: 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 an anode and a titanium sheet of the same size as a cathode, anodization is performed in an ethylene glycol solution containing ultrapure water and ammonium fluoride to prepare a titanium dioxide nanotube array; Step S3: Using the titanium dioxide nanotube array plate prepared in step S2 as the anode and a titanium sheet of the same size as the cathode, secondary 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: placing the titanium dioxide nanotube array electrode with a new oxide layer in step S3 in a tube furnace, calcining it in an air atmosphere, and then naturally cooling it to room temperature to obtain a stable titanium dioxide nanotube array transition layer; Step S5: The titanium dioxide nanotube array electrode with the transition layer prepared in step S4 is used as a cathode, and a titanium plate of the same size is used as an anode, and the electrodes are placed in a formic acid solution for electrochemical reduction to form a stable and 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 size 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 to finally obtain a Ti / TNAs / Ni-PbO2 anode.

2. The method for preparing a nickel-doped lead dioxide ozone catalytic anode according to claim 1, characterized in that The specific process of step S1 titanium sheet pretreatment is as follows: The titanium sheet is polished using a grinding wheel machine and sandpaper, pickled and alkaline washed with sodium hydroxide and sulfuric acid solutions, etched with oxalic acid of a certain concentration, taken out and cleaned with deionized water to obtain a 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-mesh grinding wheel, 600-mesh sandpaper, and 1200-mesh sandpaper, respectively, until the surface of the titanium sheet is glossy; the polished titanium sheet is alkali-washed and degreased in a 40% sodium hydroxide solution at 25°C for 30 minutes; the alkali-washed titanium sheet is pickled in a 20% sulfuric acid solution at 60°C for 20 minutes; the pickled 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: The titanium substrate obtained in step S1 is used as the anode, and a titanium sheet of the same size is used as the cathode. A single anodic oxidation is performed in an ethylene glycol solution containing 2-4 vol% ultrapure water and 0.5-1.5 wt% ammonium fluoride, and then electrolyzed with a 20-30 V direct current for 4-6 hours to allow titanium dioxide nanotube arrays to be in situ self-grown on the pretreated titanium substrate.

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: The titanium dioxide nanotube array plate prepared in step S2 is used as the anode, and a titanium sheet of the same size is used as the cathode. Secondary anodic oxidation is performed in an ethylene glycol solution containing 5-8 wt% phosphoric acid, and electrolysis is performed at 20-30 V DC for 0.5-1 h to form a new oxide layer between the titanium dioxide nanotube array and the titanium substrate.

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 a new oxide layer in step S3 is placed in a tube furnace at 450-550°C and a heating rate of 2-4°C / min in an air atmosphere and calcined for 2-4 hours, 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: The titanium dioxide nanotube array electrode with a transition layer in step S4 was used as the cathode, and a titanium plate of the same size was used as the anode. The solution was placed in a 10-20% formic acid solution at a current density of 5-10 mA / cm 2 , and electrochemical reduction is carried out for 5 to 20 minutes to form a stable and 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: The electrode with the highly conductive titanium dioxide nanotube array transition layer prepared in step S5 was used as the anode, and a titanium sheet of the same size was used as the cathode. In an acidic electrodeposition solution containing lead nitrate, nickel nitrate, potassium fluoride, polytetrafluoroethylene and a small amount of nitric acid, the current density was 20-40 mA / cm 2 , the β-PbO2 layer was obtained by electrodeposition at 80~90℃ for 1~2h, and finally the 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, 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 are prepared to prepare a β-PbO2 active layer electrodeposition solution, wherein the molar ratio of nickel to lead is 1:100 to 3:

100.

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

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