WO2018023912A1

WO2018023912A1 - Indium-doped titanium-based lead dioxide electrode, and manufacturing method thereof and application of same

Info

Publication number: WO2018023912A1
Application number: PCT/CN2016/109462
Authority: WO
Inventors: 陈建孟; 戴启洲; 夏伊静; 王家德; 乔志华
Original assignee: 浙江工业大学; 宝鸡市昌立特种金属有限公司
Priority date: 2016-08-05
Filing date: 2016-12-12
Publication date: 2018-02-08
Also published as: CN106277216A

Abstract

An indium (In)-doped titanium-based lead dioxide electrode, and manufacturing method thereof, and an application of same in degradation treatment of highly concentrated pharmaceutical wastewater with low biodegradability. The electrode uses titanium as the matrix, and comprises an antimony tin oxide base layer, an α-PbO₂ middle layer, and an In-doped, fluoride-containing β-PbO₂ active layer, wherein the layers are coated onto a titanium matrix in that order. A structural design and surface doping of the electrode are used to modify the lead dioxide electrode. By adding the post-transition metal In and a fluoride polymer resin, micro-particle dispersion of PbO₂ on the surface of the electrode becomes more compact and uniform, greatly improving a surface structure and property of the electrode and reducing an internal stress between the PbO₂ active layer and the titanium matrix. The final electrode therefore has a higher oxygen evolution potential and electrochemical stability, effectively extending the service life of the electrode. The electrode has excellent catalytic performance, long service life, and strong potential applicability, and is easy to manufacture. The invention has great market prospects.

Description

Indium doped titanium-based lead dioxide electrode and preparation method and application thereof

(1) Technical field

The invention relates to a main group metal indium (In) doped titanium-based lead dioxide electrode and a preparation method and application thereof, the electrode has high catalytic performance and can be applied to electrochemical degradation of biodegradable pharmaceutical wastewater, belonging to electrochemical Technical and environmentally friendly wastewater treatment technology.

(2) Background technology

With the rapid development of society, the quantity and variety of refractory organic compounds in industrial wastewater are increasing day by day. These toxic and harmful high-concentration refractory organic wastewaters pose great challenges to traditional biological treatment methods. The most typical one is pharmaceutical wastewater, which is complex and difficult to degrade. It is a difficult and hot spot for water treatment at home and abroad. Therefore, in order to meet increasingly stringent wastewater discharge standards, it is necessary to develop new wastewater treatment technologies with high reliability, high effect and low cost. In recent years, in the treatment of organic wastewater containing difficult biodegradation, electrochemical oxidation has no consumption or little consumption of chemical reagents, no secondary pollution, simple operation, strong oxidizing ability, mild reaction conditions, and occupation. The small area and other advantages have become a research hotspot. The key and core of electrochemical water treatment technology is the performance of anode materials. In addition to the low cost of preparation, the anode material must also have the characteristics of good electrical conductivity, high oxygen evolution potential and good catalytic activity for electrochemical oxidation treatment of organic pollutants in wastewater.

Researchers have developed a wide range of anode materials over the past few decades, including platinum, graphite, ceria, cerium oxide, tin dioxide, lead dioxide, and boron-doped diamond electrodes. The platinum electrode is expensive, the oxygen evolution potential is low, most of the current is consumed in the process of generating oxygen, resulting in low current efficiency; the graphite electrode is inexpensive, but the oxygen evolution potential is also low; the oxidation of organic matter by the cerium oxide and the cerium oxide electrode The performance is weak; the tin dioxide electrode has an obvious defect: the electrode life is too short; the preparation process of the boron doped diamond electrode is complicated and the cost is high, especially for large-area production. In contrast, the lead dioxide electrode has the advantages of good electrical conductivity, low cost, simple preparation method, high oxygen evolution potential and strong oxidizing ability, and is an electrode material which is generally considered to have application prospects. Lead dioxide electrodes are typically produced by electrodeposition on ceramic, titanium metal and other metal material substrates. Because titanium has good corrosion resistance, low price, small thermal conductivity, easy surface physical and chemical processing, it is an ideal base material for the preparation of lead dioxide electrode. At present, titanium-based lead dioxide electrodes have been successfully applied to the production of inorganic and organic compounds, environmental pollution control. However, during the use of the titanium-based lead dioxide electrode, there is a problem that the PbO ₂ active layer is not tightly bonded to the matrix, the PbO ₂ active layer has large stress, and is easily peeled off, which affects the catalytic activity and stability of the electrode. To this end, some research work has further improved the titanium-based lead dioxide electrode. One method is to introduce a tin and tantalum intermediate layer as a transition layer between the titanium substrate and the lead dioxide active layer, which can greatly reduce the internal stress between the lead dioxide active layer and the titanium substrate. Another method is to add NaF and polytetrafluoroethylene (PTFE) to the plating solution to prepare a fluorine-containing lead dioxide electrode, and the prepared electrode has the advantages of small internal stress, good bonding force and long electrode life.

Studies on lead dioxide electrodes have shown that although these improved lead dioxide electrodes have strong stability and electrocatalytic properties, it is still necessary to further improve the electrode catalytic activity and current efficiency.

(3) Invention content

Structural design and surface doping modification of PbO ₂ electrode, by using a simple electrodeposition method, by doping the main group metal element In in the plating solution, the surface structure of the electrode can be modified, and while improving the electrocatalytic performance, Further improving its oxygen evolution potential and stability will inevitably lead to a new type of electrode with superior electrocatalytic performance, which is of great significance for the research and application of organic pollutants, especially electrocatalytic oxidation methods for difficult biodegradable pollutants.

Accordingly, it is an object of the present invention to provide a novel process for treating pharmaceutical wastewater having a long oxygen evolution potential and a long life. In-doped titanium-based lead dioxide electrode and preparation method and application thereof.

In order to achieve the above objectives, the technical solution adopted by the present discovery is:

An In-doped titanium-based lead dioxide electrode, wherein the electrode is made of titanium, and the tin-germanium oxide underlayer, the α-PbO ₂ intermediate layer, and the doped indium are sequentially plated from the inside to the outside of the titanium substrate. Fluorine β-PbO ₂ active layer.

The preparation method of the In doped titanium-based lead dioxide electrode of the invention comprises: roughening the surface of the titanium substrate, preparing the tin antimony oxide underlayer by thermal decomposition on the surface of the roughened titanium substrate, and then performing alkaline The In-doped titanium-based lead dioxide electrode is prepared by electroplating an α-PbO ₂ intermediate layer and finally doping a fluorine-containing β-PbO ₂ active layer by acid composite plating.

In the present invention, the titanium substrate may be a titanium sheet, a titanium mesh or a titanium tube.

Further, the method for preparing the In-doped titanium-based lead dioxide electrode is carried out as follows:

(1) Titanium matrix pretreatment (surface roughening treatment):

The surface of the titanium substrate is sanded with sandpaper, the lye is degreased, washed with water, placed in a sulfuric acid solution, immersed and etched at 50-70 ° C for 10 to 60 minutes, washed with water, and then placed in an oxalic acid solution at 70-90. Soaking and etching at °C for 2 to 5 hours, and washing with water to obtain a pretreated titanium substrate;

(2) Preparation of tin antimony oxide underlayer by thermal decomposition method:

A: The tin antimony oxide sol solution is uniformly coated on the surface of the pretreated titanium substrate obtained in the step (1), placed in a tube muffle furnace, baked at a constant temperature of 130 ° C for 20 min, and then heated to 515 ° C. Thermal decomposition treatment for 15 min, cooling, completing an operation cycle;

B: repeat the operation cycle described in A 8 to 15 times, and finally uniformly apply the tin antimony oxide sol solution again, and then thermally decompose at 500 to 550 ° C for 60 to 80 min after cooling, and then plated with cooling. An electrode of a tin antimony oxide underlayer;

The tin antimony oxide sol solution is prepared by mixing the following parts by weight: 5 to 10 parts of SbCl ₃ , 95 to 110 parts of SnCl ₄ · 5H ₂ O, 268 to 290 parts of ethylene glycol, and 180 to 200 parts of citric acid. ;

Preferably, the tin antimony oxide sol solution is prepared by mixing the following parts by weight of materials: 7.53 parts of SbCl ₃ , 104.16 parts of SnCl ₄ ·5H ₂ O, 280 parts of ethylene glycol, and 192.14 parts of citric acid;

(3) Alkaline plating α-PbO ₂ intermediate layer:

The electrode plated with the tin antimony oxide underlayer prepared by the step (2) is an anode, and the titanium piece is a cathode, and is placed in an alkaline plating solution for constant current electrodeposition of the α-PbO ₂ intermediate layer, and the operating condition is: temperature 50 ～ 65 ° C (preferably 60 ° C), current density of 3 ~ 5 mA / cm ² (preferably 5 mA / cm ² ), deposition time of 0.5 ~ 2h (preferably 1h); obtained tin-bismuth oxide underlayer and α-PbO ₂ intermediate layer Electrode

The alkaline plating solution is prepared according to the following composition: PbO 0.1 mol/L, NaOH 4-5 mol/L, and the solvent is water;

(4) Acid composite plating doped In-containing fluorine-containing β-PbO ₂ active layer:

The electrode plated with the tin antimony oxide underlayer and the α-PbO ₂ intermediate layer prepared in the step (3) is used as an anode, and the titanium piece is used as a cathode, and is placed in an acidic plating solution to carry out constant current electrodeposition of the doped fluorine-containing β. -PbO ₂ surface active layer, operating conditions: temperature 50 ~ 90 ° C (preferably 80 ° C), current density 10 ~ 80 mA / cm ² (preferably 50 mA / cm ² ), deposition time 1.5 ~ 2h (preferably 2h), obtained The In doped titanium-based lead dioxide electrode;

The acidic plating solution is prepared as follows:

The mixture was first prepared as follows: Pb(NO ₃ ) ₂ 0.3 mol/L, KF·2H ₂ O 0.01 to 0.02 mol/L, In(NO ₃ ) ₃ 0.0015 to 0.012 mol/L, 60 wt% polytetrafluoroethylene 4~5mL / L of the emulsion, the solvent is water; the prepared mixture is adjusted to a pH of 1.5 to 2.0 with nitric acid to obtain the acidic plating solution;

Preferably, the acidic plating solution is prepared as follows:

The mixture was prepared as follows: Pb(NO ₃ ) ₂ 0.3 mol/L, KF·2H ₂ O 0.01 mol/L, In(NO ₃ ) ₃ 0.003 mol/L, 60 wt% polytetrafluoroethylene emulsion 4 mL/L The solvent is water; the prepared mixture is adjusted to a pH of 1.8 with nitric acid to obtain the acidic plating solution;

The 60 wt% polytetrafluoroethylene emulsion is commercially available directly.

Further, in the preparation method of the present invention, the step (1) is operated as follows:

After grinding the titanium substrate with sandpaper to make the surface appear silver-white metallic luster, rinse it with deionized water; then place the polished titanium substrate in a 20 wt% to 50 wt% (preferably 40 wt%) NaOH solution, soak 30 Degreasing with ~60min (preferably 30min), rinsed with deionized water; then placed in a 20 wt% to 30 wt% (preferably 20 wt%) H ₂ SO ₄ solution, soaked at 50-70 ° C (preferably 60 ° C) 10 ~60min (preferably 20min), rinsed with deionized water; then placed in 15% to 20% by weight (preferably 15% by weight) oxalic acid solution, soaked and etched at 70-90 ° C (preferably 80 ° C) for 2 ~ 5h (preferably 3h) Finally, a large amount of distilled water is used to rinse off the residual oxalic acid and titanium oxalate on the surface of the titanium substrate to obtain a pretreated titanium substrate; the obtained pretreated titanium substrate is gray pockmark and stored in 0.5 wt% to 1.5 wt% of oxalic acid solution. ,spare.

In the step (1), the surface of the titanium substrate is sanded with a sandpaper, and then generally ground with a 120-mesh coarse sandpaper, and then polished with a 600-mesh, 1200-mesh fine sandpaper until the surface of the titanium substrate exhibits a silver-white metallic luster.

In the step (2), the tin antimony oxide sol solution is uniformly applied to the surface of the pretreated titanium substrate, and the coating method may be brushing, spraying or immersing and centrifuging, which is a person skilled in the art. A well-known technique.

The In-doped titanium-based lead dioxide electrode of the invention has strong catalytic activity, high oxygen evolution potential, good stability and long service life, and can be applied to degradation treatment of high concentration biodegradable pharmaceutical wastewater; The method comprises the following steps: using the In-doped titanium-based lead dioxide electrode as the anode and the titanium plate as the cathode, and using the constant current electrolysis pharmaceutical wastewater.

The invention utilizes the main group element In to modify the surface structure of the β-PbO ₂ electroplating layer, and the beneficial effects of the invention are compared with the conventional lead dioxide electrode and the prior art:

(1) The present invention modifies a lead dioxide electrode by electrode structure design and surface doping: doping a certain amount of main group metal In in a lead nitrate solution containing a fluororesin polymer, using constant current electrochemical deposition In the method, a Ti/Sn-SbO _x /α-PbO ₂ /In-β-PbO ₂ electrode was prepared. Through the addition of the main group metal In and the high polymer fluororesin, the PbO ₂ particles on the electrode surface are more closely dispersed, which greatly improves the structure and properties of the electrode surface, and reduces the internal stress between the PbO ₂ active layer and the titanium matrix. Small, therefore, the resulting electrode has a higher oxygen evolution potential and electrochemical stability, effectively extending the life of the electrode.

(2) The doping of the main group metal In by the present invention not only improves the catalytic activity of the electrode, but also prolongs the life of the electrode. Through the improvement of surface structure, the particle size of PbO ₂ crystal is reduced, and the specific surface area of the electrode is increased, thereby effectively increasing the active site on the electrode surface. Compared with the undoped lead dioxide electrode, the catalytic activity of the modified electrode is obvious. improve.

(3) The lead dioxide electrode prepared by the invention having high oxygen evolution potential, high service life and high catalytic activity has an efficient removal effect on the biodegradable pharmaceutical wastewater.

(4) The electrode has good catalytic performance, long service life, strong practicability, easy preparation, and broad market prospect.

(4) Description of the drawings

1a is an SEM image (magnification 100 times) of the In-doped PbO ₂ electrode prepared in Example 1;

1b is an SEM image of an In-doped PbO ₂ electrode prepared in Example 1 (magnification 500 times);

FIG 2 is In Preparation Example 1 doped undoped In the XRD pattern of PbO ₂ electrode of PbO ₂ electrode prepared in Comparative Example 1, wherein, (A) an undoped In the graph of PbO ₂ electrode, (B The figure is an In doped PbO ₂ electrode;

3 is a polarization diagram of an In-doped PbO ₂ electrode prepared in Example 1 and an undoped In-PbO ₂ electrode prepared in Comparative Example 1;

Figure 4a is described in Example 2 of PbO ₂ electrode In-doped and undoped In the degradation effect of PbO ₂ electrode of 500mg / L aspirin (aspirin removal) comparison chart;

Example 2 Figure 4b the degradation of PbO ₂ In-doped and undoped In the electrode of PbO ₂ electrode 500mg / L aspirin (COD removal efficiency and current efficiency) comparison chart;

Example 5 is different from the In-doped PbO ₂ electrode 3 and undoped In the PbO ₂ electrode degradation effect of 500mg / L aspirin comparison chart.

(5) Specific implementation methods

The present invention will be further illustrated by the following specific examples, but the scope of the present invention is not limited thereto.

The 60 wt% polytetrafluoroethylene emulsion used below was purchased from Hangzhou Wannengda Technology Co., Ltd.

Example 1

Preparation of In doped titanium-based lead dioxide electrode:

(1) Titanium substrate pretreatment: a pure titanium sheet having a thickness of 0.1 mm and a size of 14 cm ² (7 cm × 2 cm) is sequentially ground with 120 mesh, 600 mesh and 1200 mesh sandpaper until the titanium matrix exhibits a silvery white metallic luster. Ion water rinse; soak the cleaned titanium sheet in a 40% NaOH solution for 30 min, rinse with deionized water; then at 60 ° C in H ₂ SO ₄ solution (mass score 20 Soak for 20min in %), take it out and wash it with deionized water; finally, soak it in oxalic acid solution (mass fraction 15%) at 80 °C for 3h, rinse with plenty of distilled water to remove oxalic acid and oxalic acid remaining on the surface of titanium substrate. Titanium, a pretreated titanium matrix is obtained. The pretreated titanium matrix is gray pockmarked and stored in oxalic acid with a mass fraction of 1%.

(2) Preparation of tin antimony oxide underlayer by thermal decomposition method: uniformly coating the tin antimony oxide sol solution on the surface of the titanium substrate pretreated by the step (1), and then placing it in a tubular muffle furnace at a constant temperature of 130 ° C After baking for 20 minutes, the electric furnace was heated to 515 ° C, thermally decomposed at this temperature for 15 minutes, and cooled to complete a cycle. The above operation was repeated 9 times, and the obtained electrode sheet was again coated with a tin sol sol gel solution, dried and then thermally decomposed at a high temperature of 515 ° C for 60 minutes, and after cooling, an electrode plated with a tin antimony oxide underlayer was obtained.

Among them, the tin antimony oxide sol solution was prepared as follows: 7.53 g SbCl ₃ , 104.16 g SnCl ₄ ·5H ₂ O, 251 mL ethylene glycol, and 192.14 g citric acid.

(3) Alkaline electroplating α-PbO ₂ layer: the electrode plated with the tin antimony oxide underlayer prepared by the step (2) is an anode, the titanium plate of the same area is a cathode, and is placed in an alkaline electroplating solution The α-PbO ₂ intermediate layer was deposited. The electrode spacing was 6 cm during electrodeposition, the temperature was 60 ° C, the current density was 5 mA cm ^-2 , and the deposition time was 1 hour. The intermediate layer of tin-bismuth oxide and α-PbO _{2 were prepared.} The electrode of the layer.

Wherein said alkaline plating baths prepared according to the following composition: PbO is 0.1mol L ^-1, NaOH is 4.5mol L ^-1, the solvent is water.

(4) Acid composite plating doped fluorine-containing β-PbO ₂ active layer: the electrode plated with the tin antimony oxide underlayer and the α-PbO ₂ intermediate layer prepared in the step (3) is used as an anode, and the same area The titanium sheet is a cathode, and a fluorine-doped β-PbO ₂ surface active layer doped with In is electrolessly deposited in an acidic plating solution. The electrode spacing is 6 cm at the time of electrodeposition, the temperature is 80 ° C, and the current density is 50 mA cm ^-2 . At a time of 2 hours, a product In doped titanium-based lead dioxide electrode was prepared.

Wherein, the acidic plating solution is prepared as follows: firstly, the mixed liquid is prepared as follows: Pb(NO ₃ ) ₂ is 0.3 mol L ^-1 , KF · 2H ₂ O is 0.01 mol L ^-1 , In(NO ₃ ) ₃ is 0.003 mol L ^-1 , 60% polytetrafluoroethylene emulsion (PTFE) 4 mL L ^-1 , the solvent is water, to obtain a mixed solution; the prepared mixture is adjusted to pH 1.8 with HNO ₃ . That is, an acidic plating solution is obtained.

Comparative example 1

Ti-based lead dioxide electrode not doped with In

The experimental steps and conditions are the same as those in the first embodiment. In the step (4), the In (NO ₃ ) ₃ is not added to the acidic plating solution, and the acidic plating solution is prepared as follows: The mixed solution is prepared as follows: Pb(NO ₃ ) ₂ is 0.3 mol L ^-1 , KF·2H ₂ O is 0.01 mol L ^-1 , and the mass fraction is 60% polytetrafluoroethylene emulsion (PTFE) 4 mL L ^-1 , the solvent is water, and the mixture is obtained. The prepared mixture was adjusted to pH 1.8 with HNO ₃ to obtain an acidic plating solution. The other steps and operations were the same, and a titanium-based lead dioxide electrode not doped with In was obtained.

The In-doped PbO ₂ electrode prepared in Example 1 was characterized by field emission scanning electron microscopy (SEM), see Figures 1a, 1b. It can be seen from Fig. 1a, 1b that the surface of the prepared electrode exhibits a distinct tetrahedral three-dimensional crystal structure, the grain distribution is dense and uniform, and the particle size is about 35 μm. 2 is an XRD pattern of an In-doped PbO ₂ electrode and an undoped PbO ₂ electrode. Comparing the β-PbO ₂ standard card, the surface active layer of the prepared In-doped lead dioxide electrode is β-PbO _{2 .} The crystal structure of the tetragonal body, and the crystallinity and crystallization orientation after doping with In is slightly different. It is known that the half-peak of the main crystal plane β(200) of the doped electrode and the undoped electrode is calculated by the Xie Le formula. After doping with In, the particle size of the PbO ₂ crystal is reduced, which helps to increase the activity of the electrode surface. Site, thereby increasing the catalytic activity of the electrode. In addition, the incorporation of In does not introduce a new phase, indicating that In may enter the β-PbO ₂ lattice in a replacement or interstitial manner to form a solid solution, which causes the diffraction peak to change.

A three-electrode electrochemical measurement system was used. In the CHI660c electrochemical workstation, the prepared In-doped lead dioxide electrode and the undoped lead dioxide electrode were used as the working electrode (10 mm×10 mm), and the platinum electrode was used as the auxiliary electrode. (10 mm × 15 mm), a saturated calomel electrode (SCE) was used as a reference electrode, and the polarization curve of the electrode was measured in a 0.5 mol L ^-1 H ₂ SO ₄ solution, as shown in Fig. 3. The oxygen evolution potential of the In-doped lead dioxide electrode was measured to be about 2.08 V, which was higher than that of the undoped Indium dioxide electrode (1.99 V). In the electrocatalytic oxidation process, the oxygen evolution reaction is a major competitive side reaction, which leads to waste of electrical energy and reduces the effective utilization of current. The higher oxygen evolution potential can effectively inhibit the occurrence probability of oxygen evolution side reactions. The oxygen evolution potential is beneficial to improve current efficiency.

Example 2

The as-doped lead dioxide electrode prepared in Example 1 and the undoped Indium dioxide electrode prepared in Comparative Example 1 were subjected to electrocatalytic oxidation degradation of aspirin.

The In-doped lead dioxide electrode prepared in Example 1 or the undoped Indium dioxide electrode prepared in Comparative Example 1 was used as the anode, the titanium sheet was the cathode, the electrode area was 14 cm ² , and the electrochemical degradation was performed by constant current electrolysis. . The constant current density is 50 mA cm ^-2 and the electrode spacing is 4 cm. 500 mg L ^-1 aspirin containing 0.1 mol L ^-1 electrolyte Na ₂ SO ₄ was used as the simulated wastewater, the reaction volume was 250 mL, and the wastewater treatment was carried out under the action of magnetic stirring, and the degradation reaction was carried out at different times for sampling analysis. The changes in the concentration of aspirin at different times were determined by high performance liquid chromatography (HPLC). The change of total organic carbon content (TOC) was measured by TOC meter. The experimental results are shown in Figures 4a and 4b. Figures 4a and 4b show a comparison of the degradation effects of In-doped PbO ₂ electrode and undoped PbO ₂ electrode on 500 mg L ^-1 aspirin. Figure 4a shows the removal rate of aspirin and Figure 4b shows the removal rate of TOC.

It can be seen from Fig. 4a, 4b that after aspirin is electrochemically degraded by In-doped lead dioxide electrode for 2.5 hours, the removal rate of aspirin is 76.45%, and the removal rate of COD is also 52.09%, while the lead dioxide of undoped In is used. At the electrode, the removal rate of aspirin was 64.07%, and the removal rate of COD was 43.53%, indicating that the removal effect of In-doped lead dioxide electrode was significantly better than that of undoped electrode. And by comparing the current efficiency of two electrodes in degrading aspirin, you can find The current efficiency of the In-doped lead dioxide electrode during the degradation process is higher than that of the undoped Indium dioxide electrode.

In addition, we also tested the safety of As-doped electrode degradation of aspirin. The toxic metal ions that may be generated in electrolysis are detected by plasma gas chromatography (ICP-MS), such as Pb, Ti, Sn, Sb, and In. From the experimental results, it is known that Ti is not detected in the treated wastewater solution. The presence of Sn, Sb and In ions, the concentration of Pb ions is 0.005 mg L ^-1 , which is much lower than the emission standard of lead ions (≤0.1 mg L ^-1 ). Therefore, the use of In-doped lead dioxide electrode to degrade aspirin is highly safe.

Example 3

Preparation of In doped titanium-based lead dioxide electrode:

(3) α-PbO ₂ alkaline plating layer: In step (2), antimony tin oxide electrode prepared by the underlying plating anode, the area of the titanium sheet, etc. as a cathode in an alkaline electroplating bath constant current level The α-PbO ₂ intermediate layer was deposited. The electrode spacing was 6 cm during electrodeposition, the temperature was 60 ° C, the current density was 5 mA cm ^-2 , and the deposition time was 1 hour. The intermediate layer of tin-bismuth oxide and α-PbO _{2 were prepared.} The electrode of the layer.

(4) Acid composite plating doped fluorine-containing β-PbO ₂ active layer: the electrode plated with the tin antimony oxide underlayer and the α-PbO ₂ intermediate layer prepared in the step (3) is used as an anode, and the same area The titanium sheet is used as a cathode, and the fluorine-containing β-PbO ₂ surface active layer doped with In is subjected to constant current electrodeposition in an acidic plating solution having different In contents. The electrode spacing is 6 cm at the time of electrodeposition, the temperature is 80 ° C, and the current density is 50 mA cm ^-2 , deposition time is 2 hours, and the product is prepared with different In-doped titanium-based lead dioxide electrodes.

Wherein, the acidic plating solution with different In contents is prepared as follows: firstly, the mixed liquid is prepared as follows: Pb(NO ₃ ) ₂ is 0.3 mol L ^-1 , KF · 2H ₂ O is 0.01 mol L ^-1 , In (NO ₃ ) ₃ each of 0.0015 mol L ^-1 , 0.003 mol L ^-1 , 0.006 mol L ^-1 and 0.012 mol L ^-1 , 60% by mass of polytetrafluoroethylene emulsion (PTFE) 4 mL L ^-1 , The solvent was water to obtain a mixed solution; the prepared mixture was adjusted to pH 1.8 with HNO ₃ to obtain an acidic plating solution having different In contents.

Each of the different In-doped lead dioxide electrodes prepared as described above and the undoped Indium dioxide electrode prepared in Comparative Example 1 were subjected to electrocatalytic oxidation degradation of aspirin. The experimental condition parameters were the same as in Example 2, and the experimental results are shown in Fig. 5.

It can be seen from the figure that as the concentration of In(NO ₃ ) _{3 in the} electrodeposition liquid increases, the removal rate of aspirin gradually increases. When the concentration of In(NO ₃ ) _{3 in the} electrodeposition liquid was 0.003 mol L ^-1 , the obtained In-PbO ₂ electrode had the highest aspirin removal rate. When the concentration of In(NO ₃ ) ₃ continued to increase, the removal rate of aspirin decreased. When the concentration of In(NO ₃ ) _{3 in the} electrodeposition solution was 0.012 mol L ^-1 , the prepared In-PbO ₂ electrode to aspirin The removal rate is lower than that of the undoped PbO ₂ electrode. When the In content is high, it is difficult for the larger In atom to completely enter the PbO ₂ lattice, and become a single phase, so excessive In precipitates on the surface of the electrode and occupies the surface of the electrode, reducing the active site of the electrode. , reducing the catalytic activity of the electrode.

After 2.5 h of electrocatalytic oxidation treatment, the removal rate of aspirin by In-PbO ₂ electrode prepared by the concentration of In(NO ₃ ) _{3 in the} electrodeposition solution was 0.003 mol L ^-1 , which was 76.45% in the electrodeposition solution. The In-PbO ₂ electrode prepared at a concentration of In(NO ₃ ) ₃ of 0 mol L ^-1 , 0.0015 mol L ^-1 , 0.006 mol L ^-1 and 0.012 mol L ^-1 was 1.19, 1.06, 1.12 and 1.26 times. In addition, a first-order reaction kinetics fit was performed on the degradation process of aspirin to obtain an ln(C/C0)~t curve, as shown in the inset of FIG. As can be seen from the figure, the degradation of aspirin accords with the pseudo first-order kinetic equation. The concentration of In(NO ₃ ) _{3 in the} electrodeposition solution is 0 mol L ^-1 , 0.0015 mol L ^-1 , 0.003 mol L ^-1 , 0.006 mol L ^- The degradation rate constants of aspirin on the In-PbO ₂ electrode prepared at ¹ and 0.012 mol L ^-1 were 1.2 × 10 ^-4 s ^-1 , 1.5 × 10 ^-4 s ^-1 , and 1.7 × 10 ^-4 s ^{-1 , respectively.} , 1.3×10 ^-4 s ^-1 and 1.1×10 ^-4 s ^-1 , indicating that the aspirin is formed on the In-PbO ₂ electrode when the concentration of In(NO ₃ ) ₃ in the electrodeposition solution is 0.003 mol L ^-1 . The degradation rate is higher than other electrodes. Therefore, an appropriate amount of In modification is beneficial to improve the ability of the PbO ₂ electrode to degrade organic pollutants.

Claims

An In doped titanium-based lead dioxide electrode, characterized in that the electrode is made of titanium as a base, and a tin antimony oxide underlayer, an α-PbO 2 intermediate layer, and a doped layer are sequentially plated from the inside to the outside of the titanium substrate. A fluorine-containing β-PbO 2 active layer of a hetero In.
The In doped titanium-based lead dioxide electrode according to claim 1, wherein the titanium substrate is a titanium sheet, a titanium mesh or a titanium tube.
The method of claim 1 , wherein the preparation method comprises:

(1) roughening the surface of the titanium substrate to obtain a roughened titanium substrate;

(2) preparing a tin antimony oxide underlayer by a thermal decomposition method on the surface of the roughened titanium substrate obtained in the step (1) to obtain an electrode coated with a tin antimony oxide underlayer;

(3) The electrode of the tin-bismuth oxide underlayer obtained by the step (2) is subjected to alkaline plating of the α-PbO 2 intermediate layer to obtain an electrode plated with a tin antimony oxide underlayer and an α-PbO 2 intermediate layer;

(4) Step (3) The electrode plated with the tin antimony oxide underlayer and the α-PbO 2 intermediate layer is doped with an In-doped fluorine-containing β-PbO 2 active layer by acid composite plating, thereby preparing the In do doping. Titanium-based lead dioxide electrode.
The preparation method according to claim 3, wherein the operation method of the step (1) is:

The surface of the titanium substrate is sanded with sandpaper, the lye is degreased, washed with water, placed in a sulfuric acid solution, immersed and etched at 50-70 ° C for 10 to 60 minutes, washed with water, and then placed in an oxalic acid solution at 70-90. The solution was immersed and etched at ° C for 2 to 5 hours, and washed with water to obtain a roughened titanium substrate.
The preparation method according to claim 4, wherein the operation method of the step (1) is:

The titanium substrate is sanded with sandpaper to make the surface appear silver-white metallic luster, and then rinsed with deionized water; then the polished titanium substrate is placed in a 20 wt% to 50 wt% NaOH solution, and immersed for 30 to 60 minutes to remove oil. Rinse with deionized water; then place in 20 wt% ~ 30 wt% H 2 SO 4 solution, immerse and etch at 50 ~ 70 ° C for 10 ~ 60 min, rinse with deionized water; then place 15 wt% ~ 20 wt% oxalic acid solution The solution is immersed and etched at 70-90 ° C for 2 to 5 hours, and finally rinsed with distilled water to remove oxalic acid and titanium oxalate remaining on the surface of the titanium substrate to obtain a roughened titanium substrate, and stored in 0.5 wt% to 1.5 wt% of oxalic acid solution. Medium, spare.
The preparation method according to claim 3, wherein the operation method of the step (2) is:

A: The tin antimony oxide sol solution is uniformly applied to the surface of the roughened titanium substrate obtained in the step (1), placed in a tube muffle furnace, baked at a constant temperature of 130 ° C for 20 min, and then heated to 515. °C thermal decomposition treatment for 15min, cooling, complete an operation cycle;

B: repeat the operation cycle described in A 8 to 15 times, and finally uniformly apply the tin antimony oxide sol solution again, and then thermally decompose at 500 to 550 ° C for 60 to 80 min after cooling, and then plated with cooling. An electrode of a tin antimony oxide underlayer;

The tin antimony oxide sol solution is prepared by mixing the following parts by weight: 5 to 10 parts of SbCl 3 , 95 to 110 parts of SnCl 4 · 5H 2 O, 268 to 290 parts of ethylene glycol, and 180 to 200 parts of citric acid. .
The preparation method according to claim 3, wherein the operation method of the step (3) is:

The electrode plated with the tin antimony oxide underlayer prepared by the step (2) is an anode, and the titanium piece is a cathode, and is placed in an alkaline plating solution for constant current electrodeposition of the α-PbO 2 intermediate layer, and the operating condition is: temperature 50 ～ 65 ° C, current density of 3 ~ 5 mA / cm 2 , deposition time of 0.5 ~ 2h; an electrode plated with a tin antimony oxide underlayer and an α-PbO 2 intermediate layer;

The alkaline plating solution is prepared according to the following composition: PbO 0.1 mol/L, NaOH 4-5 mol/L, and the solvent is water;
The preparation method according to claim 3, wherein the operation method of the step (4) is:

The electrode plated with the tin antimony oxide underlayer and the α-PbO 2 intermediate layer prepared by the step (3) is an anode, and the titanium piece is a cathode, and is placed in an acidic plating solution to carry out constant current electrodeposition of the doped fluorine-containing β- The PbO 2 surface active layer is operated at a temperature of 50 to 90 ° C, a current density of 10 to 80 mA/cm 2 , and a deposition time of 1.5 to 2 h to obtain the In-doped titanium-based lead dioxide electrode;

The acidic plating solution is prepared as follows:

The mixture was first prepared as follows: Pb(NO 3 ) 2 0.3 mol/L, KF·2H 2 O 0.01 to 0.02 mol/L, In(NO 3 ) 3 0.0015 to 0.012 mol/L, 60 wt% polytetrafluoroethylene The emulsion is 4-5 mL/L, and the solvent is water; the prepared mixture is adjusted to a pH of 1.5 to 2.0 with nitric acid to obtain the acidic plating solution.
The use of the In doped titanium-based lead dioxide electrode according to claim 1 in the degradation treatment of high concentration biodegradable pharmaceutical wastewater.
The use according to claim 9, wherein the In-doped titanium-based lead dioxide electrode is used as an anode and the titanium plate is used as a cathode, and a constant current electrolysis pharmaceutical wastewater is used.