A com-btnt anode, a preparation method and application thereof

Abstract

The application relates to the technical field of nanomaterials, in particular to a CoMo-BTNT anode, a preparation method and application thereof, wherein the preparation method comprises the following steps: preparing a Ti substrate; preparing a titanium dioxide nanotube array by using the Ti substrate; depositing a Co-Mo oxide layer deposition solution onto the surface of the TNA through a direct current deposition method, and then performing annealing heat treatment to prepare a CoMo-TNA; and preparing the CoMo-BTNT anode by taking the CoMo-TNA as a cathode and a Pt sheet as an anode; the application further provides application of the above CoMo-BTNT anode in antibiotic degradation in water; the application takes the TNA as a base layer, and deposits an active CoMo oxide layer thereon; the CoMo-BTNT anode has good conductivity and electrocatalytic performance, the conductivity of the anode is improved, an effective electrically assisted activated PMS tetracycline degradation system is constructed, and a new solution idea is provided for tetracycline wastewater treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials, in particular to a CoMo-BTNT anode, a preparation method and application thereof. BACKGROUND

[0002] Tetracycline antibiotics (TCs) are one of the most widely used antibiotics in the world, mainly used in clinical medicine, livestock and poultry breeding, and aquaculture industries. Since this class of compounds is not easily absorbed by organisms, it is difficult to degrade in the environment, and it is difficult to completely remove in conventional wastewater treatment systems, which poses a serious threat to the ecosystem and human health. Therefore, it is of great significance to develop efficient tetracycline deep purification technology.

[0003] The sulfate radical-based (SO4 ·- ) advanced oxidation technology is considered an attractive method for degrading organic pollutants because it has a higher oxidation-reduction potential, a longer half-life, milder pH conditions, and higher selectivity. In this case, the selection of anode material is crucial.

[0004] Vertically oriented blue-black TiO2 nanotube arrays (TNA) are widely used in (photo) electrochemical AOPs as host catalysts or intermediate layers to remove organic pollutants due to their high aspect ratio, large specific surface area, and more active sites. However, anatase TNA usually exhibits n-type semiconductor properties, and charge transport is limited, resulting in an undesirable electro-oxidation capacity and poor degradation of persistent organic pollutants, thus limiting its application in anode materials. SUMMARY

[0005] To solve this problem, the inventors found that uniformly filling nanoparticles within the TNA channels is an effective method that can significantly improve the efficiency of directional electron transfer and surface activity. Based on this, the present application develops a Co / Mo-BTNT anode with multi-metal synergistic catalysis. Specifically, the present application uses TNA as the base layer and deposits an active CoMo oxidation layer on it, which has good electrical conductivity and electrocatalytic performance, improves the electrical conductivity of the anode, and constructs an effective electro-assisted activation PMS degradation tetracycline system, providing a new solution for the treatment of tetracycline wastewater.

[0006] The embodiments of the present application are implemented by the following technical solutions:

[0007] Firstly, the present application provides a preparation method of CoMo-BTNT anode, comprising the following steps:

[0008] (1) preparing a Ti substrate;

[0009] (2) using Ti substrate to prepare titanium dioxide nanotube array (TNA);

[0010] (3) depositing Co-Mo oxide layer deposition solution onto the surface of TNA by direct current electrodeposition method, and then performing annealing heat treatment to prepare CoMo-TNA;

[0011] (4) using CoMo-TNA as cathode and Pt sheet as anode to prepare CoMo-BTNT anode; wherein, BTNT represents blue titanium dioxide nanotube array.

[0012] More specifically, in step (1), the preparation of Ti substrate includes the following steps: firstly, polishing the titanium foil with 600, 800, 1500 and 2000 grit sandpaper in sequence to remove the surface oxide layer of the titanium foil, and then cutting the titanium foil into a titanium sheet with a desired size; then, cleaning the titanium sheet in an ultrasonic tank with acetone, ethanol and ultrapure water for 30-60 min; immersing the cleaned titanium sheet in an oxalic acid solution with a concentration of 10-20% and heating in a water bath at 90-100 ℃ for 1.5-2.5 h; stopping the treatment when the surface of the titanium sheet becomes a matte state, and cleaning it to obtain the Ti substrate.

[0013] In step (2), the preparation of TNA includes the following steps: using Ti substrate as anode and Pt sheet as cathode, performing first anodic oxidation in an electrolyte containing fluoride ions for a period of time; then continuing the second anodic oxidation in an electrolyte containing fluoride ions for a period of time, and finally flushing the electrolyte remaining on the surface of the Ti substrate to obtain the titanium dioxide nanotube array; more specifically, using Ti substrate as anode and Pt sheet as cathode, anodic oxidation in a mixed solution of 0.25% (mass fraction) NH4F and 2% (mass fraction) H2O in ethylene glycol at 60 V for 1-2 h; then continuing anodic oxidation in a mixed solution of 0.1% (mass fraction) NH4F and 1% (mass fraction) H2O in ethylene glycol for 3-5 h; after oxidation, flushing the electrolyte remaining on the surface of the Ti substrate with ultrapure water to obtain the TNA substrate.

[0014] The first anodic oxidation in the present application is to prepare titanium dioxide nanotube array vertically grown on the Ti substrate, and then wash the prepared titanium dioxide nanotube in a deionized water or acid in an ultrasonic environment, so that the substrate surface will have a trace of nanotube distribution and eliminate defects and cracks; then, the second anodic oxidation is performed on this basis to make the grown titanium dioxide nanotube have more uniform pore size and more ordered arrangement.

[0015] In the step (3) of preparing the CoMo-TNA, the following steps are included: firstly, a Co-Mo oxide layer deposition solution is prepared by mixing CoSO4·7H2O, Na3C6H5O7·2H2O and Na2MoO4·2H2O according to a molar concentration ratio of 0.1-0.2:0.2-0.3:0.005-0.01, and adjusting the pH value of the system solution to 8-10; then, the Co-Mo oxide layer deposition solution is deposited on the surface of the TNA by a direct current deposition method, more specifically, using a Pt sheet electrode as an anode and the TNA as a cathode, and placing the TNA in the Co-Mo oxide layer deposition solution under the condition of a current density of 20-40 mA / cm 2 2, a deposition temperature of 40-60℃, a stirring speed of 200-400 r / min and an electrodeposition time of 3000-4000 s, so as to obtain the CoMo-TNA (amorphous), which is washed with ultrapure water, dried, annealed at 400-500℃ in a tube furnace for 1-3 h, and then obtained as the CoMo-TNA (anatase).

[0016] In the step (4) of preparing the CoMo-BTNT anode, the CoMo-TNA (anatase) is used as a cathode, a Pt sheet is used as an anode, and the CoMo-BTNT anode is obtained by placing the CoMo-TNA (anatase) in a solution containing 5-15% (v%) formic acid under the condition of a current density of 3-10 mA / cm 2 2, reducing the cathode in the solution for 5-10 min, and changing Ti in part of the TiO2 in the cathode into Ti 4+ , so as to change the color of the CoMo-BTNT anode into blue. 3+

[0017] Secondly, the application further provides a CoMo-BTNT anode prepared by the above preparation method.

[0018] Thirdly, the application further provides an application of the CoMo-BTNT anode, which is mainly used in the degradation of antibiotics in water.

[0019] (1) preparing a reaction solution by mixing the to-be-tested solution, sodium sulfate and monopersulfate, and adjusting the temperature of the solution system to 20-30℃, and then placing the CoMo-BTNT anode in the reaction solution and reacting for a period of time under the condition of power supply;

[0020] (2) filtering the reaction solution, measuring the ultraviolet-visible absorbance of the reaction solution, and then obtaining the concentration of the antibiotics in the to-be-tested solution by substituting the measured absorbance data into a linear equation of absorbance and antibiotic concentration.

[0021] The technical scheme of the application has at least the following advantages and beneficial effects: ​

[0022] 1. The CoMo-BTNT anode material is successfully synthesized, and a method for degrading antibiotics in wastewater based on the CoMo-BTNT anode material is established. The degradation method can quickly and accurately degrade antibiotics in water with high sensitivity, and shows good application performance in actual water samples.

[0023] 2. The CoMo-BTNT is prepared by depositing an active CoMo oxide layer on the TNA base layer. The synergistic effect of Co and Mo is beneficial to the formation of oxygen vacancies in the main crystal lattice and the Co and Mo species redox pairs, thereby improving the conductivity and oxidation capacity of the anode. In addition, the redox pairs (CoII / CoIII and MoIV / MoVI) formed between Co and Mo promote the redox cycle of Co species, thereby improving the oxidation capacity of the catalyst. Based on this, the CoMo-BTNT anode with Co and Mo synergistic catalysis is developed, which improves the conductivity and electrocatalytic performance of the anode, and an effective PMS activation system for degrading tetracycline is constructed, providing a new solution for tetracycline wastewater treatment.

[0024] 3. The CoMo-BTNT can effectively activate PMS to generate active oxygen substances such as sulfate radicals (SO4 ·- ), superoxide anions (O2 ·- ) and singlet oxygen radicals (O2 1 ). The oxidation-reduction potential of SO4 ·- is higher, and the half-life is longer, which enables it to effectively contact and oxidize target pollutants and function in a wider pH range. In addition, SO4 ·- has higher selectivity and can directly attack specific electron-rich functional groups such as amino (-NH2), hydroxyl (-OH) and other organic compounds containing unsaturated bonds through electron transfer reactions. Similarly, 1 O2 has a long lifetime and a wider pH value tolerance, and shows high electrophilicity and selectivity to electron-rich substances due to its unoccupied π* orbital. Therefore, SO4 ·- and 1 O2 can quickly and effectively oxidize high-priority pollutants with little interference from actual wastewater matrix, which lays a foundation for selective detection and degradation of antibiotics pollutants in the environment. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The preparation process of CoMo-BTNT of the embodiment 1 of the present application is shown in the figure;

[0026] Figure 2 SEM images of CoMo-BTNT prepared in Example 1 of the present application and BTNT prepared in Comparative Example 1; wherein, Figure 2 (a) and Figure 2 (c) are top view and side view of BTNT, respectively; Figure 2 (b) and Figure 2 (d) are top view and side view of CoMo-BTNT, respectively; Figure 2 (e)- Figure 2 (h) is EDS element mapping of CoMo-BTNT;

[0027] Figure 3 X-ray diffraction patterns of TNA (anatase), Co / Mo-TNA (amorphous) prepared in Example 1 of the present application, CoMo-TNA (anatase) and CoMo-BTNT;

[0028] Figure 4 Resulting graph of degradation effect of tetracycline within 60 min under different experimental group systems;

[0029] Figure 5 Resulting graph of degradation effect of tetracycline under different current densities;

[0030] Figure 6 Resulting graph of degradation effect of tetracycline under different PMS dosages;

[0031] Figure 7 Resulting graph of degradation effect of tetracycline under different pH values;

[0032] Figure 8 Stability resulting graph of CoMo-BTNT anode material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme of the embodiments of the present application will be described clearly and completely below. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be purchased in the market.

[0034] A CoMo-BTNT anode, a preparation method and application thereof provided by the embodiments of the present application will be described in detail below.

[0035] The preparation method of the CoMo-BTNT anode comprises the following steps:

[0036] (1) Preparation of Ti substrate: first, polish the titanium foil with 600, 800, 1500, 2000 grit sandpaper in sequence to remove the surface oxide layer of the titanium foil, then cut the titanium foil into a titanium sheet of the desired size, and then clean the titanium sheet in an ultrasonic bath with acetone, ethanol and ultrapure water for 30-60 min. Immerse the cleaned titanium sheet in an oxalic acid solution with a concentration of 10-20%, and heat it in a water bath at 90-100°C for 1.5-2.5 h. Stop the treatment when the surface of the titanium sheet becomes a matte state, and clean it thoroughly to obtain the Ti substrate;

[0037] (2) Preparation of titanium dioxide nanotube array (TNA) using Ti substrate: use the Ti substrate as an anode and a Pt sheet as a cathode to perform the first anodic oxidation in an electrolyte containing fluoride ions for a period of time, then continue the second anodic oxidation in an electrolyte containing fluoride ions for a period of time, and finally rinse the electrolyte remaining on the surface of the Ti substrate to obtain the titanium dioxide nanotube array; more specifically, use the Ti substrate as an anode and a Pt sheet as a cathode to perform anodic oxidation in a mixed solution of 0.25% (mass fraction) NH4F and 2% (mass fraction) H2O in ethylene glycol at 60 V for 1-2 h, then continue the anodic oxidation in a mixed solution of 0.1% (mass fraction) NH4F and 1% (mass fraction) H2O in ethylene glycol for 3-5 h, and after the oxidation is completed, rinse the electrolyte remaining on the surface of the Ti substrate with ultrapure water to obtain the TNA substrate;

[0038] The first step of anodic oxidation in the present application is to prepare a titanium dioxide nanotube array vertically grown on the Ti substrate, and then wash the prepared titanium dioxide nanotube in a deionized water or acid in an ultrasonic environment, so that the substrate surface will have a trace of nanotube distribution and eliminate defects and cracks; then perform the second step of anodic oxidation based on this, so that the grown titanium dioxide nanotube has more uniform pore size and more ordered arrangement.

[0039] (3) Preparation of CoMo-TNA by depositing Co-Mo oxidation layer deposition solution onto the surface of TNA through direct current electrodeposition method: first, prepare the Co-Mo oxidation layer deposition solution by mixing CoSO4·7H2O, Na3C6H5O7·2H2O and Na2MoO4·2H2O according to the molar concentration ratio of 0.1-0.2:0.2-0.3:0.005-0.01, and then adjust the pH value of the system solution to 8-10 to obtain the Co-Mo oxidation layer deposition solution; then, deposit the Co-Mo oxidation layer deposition solution onto the surface of TNA through direct current electrodeposition method, more specifically, use a Pt sheet electrode as an anode and TNA as a cathode, and deposit the Co-Mo oxidation layer deposition solution onto the surface of TNA at a current density of 20-40 mA / cm 2Next, the TNA is placed in the Co-Mo oxide layer deposition solution, and the deposition temperature is controlled to be 40-60 DEG C, the stirring rate is controlled to be 200-400 r / min, and the CoMo-TNA (amorphous) is obtained by electrodeposition for 3000-4000 s. After being washed with ultrapure water and dried, the CoMo-TNA (anatase) is obtained by annealing at 400-500 DEG C in a tube furnace for 1-3 h.

[0040] (4) CoMo-TNA is used as the cathode, and a Pt sheet is used as the anode to prepare a CoMo-BTNT anode; wherein, BTNT represents a blue titanium dioxide nanotube array; more specifically, CoMo-TNA (anatase) is used as the cathode, and a Pt sheet is used as the anode, and the CoMo-BTNT anode is prepared under the condition that the current density is 3-10 mA / cm 2 Next, the cathode is immersed in a formic acid solution with a volume percentage of 5-15%, and the cathode is reduced for 5-10 min. After reduction, Ti 4+ in part of the TiO2 is changed into Ti 3+ , and the color is changed into blue, i.e., the CoMo-BTNT anode is obtained.

[0041] The application further provides a CoMo-BTNT anode prepared by the above preparation method.

[0042] The application further provides an application of the CoMo-BTNT anode, which is mainly used in the degradation of antibiotics in water. The application is described in detail by taking the degradation of tetracycline antibiotics (TCs) as an example. Specifically, the degradation method of tetracycline antibiotics is as follows:

[0043] (1) A reaction solution is prepared: 60 mL of a solution system is prepared by mixing a to-be-tested solution with 0.03-0.08 M sodium sulfate and 0.5 mM-1.0 mM peroxymonosulfate (PMS), and the temperature of the solution system is adjusted to be 20-30 DEG C, i.e., the reaction solution is obtained. The CoMo-BTNT is placed in the reaction solution and reacts for a period of time under the condition of power supply.

[0044] The initial pH value of the reaction solution is 3-4, and is preferably 3.83. The current density under the condition of power supply is 2.5 mA / cm 2 -5 mA / cm 2 , and is preferably 5 mA / cm 2 .

[0045] (2) Then, 1 mL of the reaction solution was taken with a syringe equipped with a 0.22 μm polyether sulfone needle filter, the reaction solution was filtered, and UV-Vis spectrum analysis was performed on the filtered reaction solution at 357 nm by means of a UV spectrophotometer, the UV-visible absorbance of the reaction solution was measured, and the measured absorbance data was substituted into the linear equation of absorbance and antibiotic concentration, i.e. the concentration of tetracycline antibiotics in the measured solution was obtained; wherein the linear equation is: y = 0.02672x + 0.01461 (R 2 = 0.9993); wherein x represents the concentration of tetracycline antibiotics, and y represents the absorbance at 357 nm (A 357 ).

[0046] To solve the problems of anatase TNA in application, the inventors found that uniformly filling nanoparticles in the TNA channel is an effective method, which can significantly improve the efficiency of directional electron transfer and active surface. And transition molybdate shows high electrochemical performance due to its modulation conductivity, large surface area and high active oxidation state, and it has multiple oxidation states, low cost and environmental friendliness, which is conducive to improving the redox activity.

[0047] CoMo-BTNT can effectively activate PMS, so that PMS is activated to generate active oxygen substances such as sulfate radicals (SO4 ·- ), superoxide anion (O2 ·- ) and singlet oxygen radical ( 1 O2). The redox potential of SO4 ·- is higher, and the half-life is longer, which enables it to effectively contact and oxidize target pollutants and play a role in a wider pH range. In addition, SO4 ·- has higher selectivity and can directly attack specific electron-rich functional groups such as amino (-NH2), hydroxyl (-OH) and other organic compounds containing unsaturated bonds through electron transfer reactions. Similarly, 1 O2 has a long lifetime and a wider pH value tolerance, and shows high electrophilicity and selectivity to electron-rich substances due to its unoccupied π* orbital. Therefore, SO4 ·- and 1 O2 can quickly and effectively oxidize high-priority pollutants and are almost not disturbed by actual wastewater matrix, which lays a foundation for selective detection and degradation of antibiotic pollutants in the environment.

[0048] In addition, the synergistic effect of Co and Mo is conducive to the formation of oxygen vacancies in the main lattice, Co and Mo species redox pairs, thereby improving the conductivity and oxidation capacity of the anode. In addition, the formation of redox couples between Co and Mo (CoII / CoIII and MoIV / MoVI) promotes the redox cycle of Co species, thereby improving the oxidation capacity of the catalyst. Based on this, the CoMo-BTNT anode catalyzed by Co and Mo is developed, which improves the conductivity of the anode, constructs an effective electrically assisted activation PMS degradation TC system, and provides a new solution for the treatment of tetracycline wastewater.

[0049] Example 1

[0050] The embodiment provides a preparation method of a CoMo-BTNT anode, comprising the following steps:

[0051] (1) Pretreatment: polishing the titanium foil with 600, 800, 1500 and 2000 grit sandpaper in sequence to remove the surface oxide layer of the titanium foil, and cutting the titanium foil into a titanium sheet with a size of 20mm x 10mm; then, sequentially cleaning the titanium sheet in an ultrasonic tank with acetone, ethanol and ultrapure water for 30min; immersing the cleaned titanium sheet in a 10% oxalic acid solution, heating at 98℃ in a water bath for 2h, and taking out the titanium sheet when the surface of the titanium sheet becomes a matte state, and then cleaning the titanium sheet with ultrapure water to obtain a Ti substrate;

[0052] (2) Preparation of amorphous TNA:

[0053] First step anodic oxidation: taking the Ti substrate as an anode and a Pt sheet as a cathode, anodizing in a 0.25% NH4F and 2% H2O ethylene glycol solution at 60V for 1h;

[0054] Second step anodic oxidation: then anodizing in a 0.1% NH4F and 1% H2O ethylene glycol solution for 4h; after the oxidation is completed, the electrolyte remaining on the surface of the Ti substrate is washed with ultrapure water to obtain a TNA substrate;

[0055] (3) Preparation of CoMo-TNA: first, prepare a Co-Mo oxide layer deposition solution: mix 0.14M CoSO4·7H2O, 0.2M Na3C6H5O7·2H2O and 0.007M Na2MoO4·2H2O, and then adjust the pH value of the system solution to 9 to obtain the Co-Mo oxide layer deposition solution; then, using a Pt sheet electrode as an anode and the TNA substrate as a cathode, depositing at a deposition temperature of 50℃ and a current density of 30mA / cm 2CoMo-TNA(amorphous) was prepared by placing TNA in Co-Mo oxidation layer deposition solution under the conditions of a deposition temperature of 50℃, a stirring rate of 300r / min, and an electrodeposition time of 3600s, and then annealing CoMo-TNA(amorphous) in a tube furnace at 450℃ for 2h to obtain CoMo-TNA(anatase).

[0056] (4) Preparation of CoMo-BTNT anode: CoMo-TNA(anatase) was used as a cathode, and a Pt sheet was used as an anode, and then the cathode was reduced in a 10% formic acid solution under the conditions of a current density of 5mA / cm 2 for 5min to obtain a CoMo-BTNT anode; a specific preparation process is shown in the schematic diagram of Figure 1 .

[0057] The prepared CoMo-BTNT anode was used for the degradation of tetracycline antibiotics in water samples, and the degradation method was as follows: (1) preparation of a reaction solution: 60mL of a solution system was prepared by mixing a to-be-tested liquid with 0.05M sodium sulfate and 1.0mM monopersulfate, and the temperature of the solution system was adjusted to room temperature to obtain a reaction solution, and the prepared CoMo-BTNT anode was placed in the reaction solution and reacted for 10min under the conditions of a current density of 5mA / cm 2 .

[0058] (2) 1mL of the reaction solution was taken by using a syringe equipped with a 0.22μm polyether sulfone needle filter, the reaction solution was filtered, and then UV-Vis spectral analysis was performed on the filtered reaction solution at 357nm by using an ultraviolet spectrophotometer, the ultraviolet visible absorbance of the reaction solution was measured, and the measured absorbance data was substituted into a linear equation of absorbance and antibiotic concentration to obtain the concentration of tetracycline antibiotics in the to-be-tested liquid; wherein the linear equation is: y=0.02672x+0.01461(R 2 =0.9993); wherein x represents the concentration of tetracycline antibiotics, and y represents the absorbance at 357nm.

[0059] Example 2

[0060] The difference between Example 2 and Example 1 is that in step (3), the molar concentration ratio of CoSO4·7H2O, Na3C6H5O7·2H2O and Na2MoO4·2H2O is 0.15:0.25:0.006.

[0061] Example 3

[0062] The difference between Example 3 and Example 1 is that in step (3), annealing was performed at 400℃ for 2h.

[0063] Example 4

[0064] Example 4 differs from Example 1 in that, in step (4), the current density is 6 mA / cm 2 Next, the cathode is immersed in a 15% by volume formic acid solution and reduced for 10 min.

[0065] Comparative Example 1

[0066] This comparative example differs from Example 1 in that it does not contain the electrodeposition step of step (3); that is, after two-step anodization, the Ti substrate is directly annealed and then cathodically reduced, and the final product is recorded as BTNT.

[0067] Comparative Example 2

[0068] This comparative example differs from Example 1 in that it does not contain the electrodeposition step of step (3) and does not contain step (4); that is, after two-step anodization, the Ti substrate is annealed at 450°C for 1 h, and the final product is recorded as TNA (anatase).

[0069] It should be noted that, in the following experimental examples, CoMo-BTNT used, unless otherwise specified, is prepared by the preparation method of Example 1. In addition, Co / Mo-BTNT and CoMo-BTNT in this text and the drawings of the specification are synonymous.

[0070] Experimental Example 1

[0071] 1. The morphology of the Co / Mo-BTNT prepared in Example 1 and the BTNT material prepared in the comparative examples was analyzed by field emission scanning electron microscopy (SEM); see Figures Figure 2 (a)-(c), respectively. Figure 2 (a) and Figure 2 (c) show the top view and side view of BTNT, respectively, and it can be observed from Figure 2 (a) and Figure 2 (c) that a uniform and dense tubular structure is formed vertically on the titanium foil, and the average length of the nanotube array is 8.41 μm, the outer diameter is 136 nm, and the wall thickness is about 22 nm. Figure 2 (b) and Figure 2 (d) show the top view and side view of CoMo-BTNT, respectively, and it can be observed from Figure 2 (b) and Figure 2 (d) that a uniform CoMo oxide layer is deposited at the top of CoMo-BTNT, with a thickness of about 2.39 μm, and a TiO2 nanotube intermediate layer is formed after anodization, with a length of 5.20 μm, and because of the coverage of the CoMo oxide layer, the tube diameter of the TiO2 nanotube intermediate layer cannot be measured.

[0072] In addition, Figure 2 (e)- Figure 2 (h) is the EDS element mapping of CoMo-BTNT, wherein Co, Mo, Ti and O are uniformly distributed on the surface of the CoMo-BTNT anode; the above results show that the CoMo-BTNT anode material is successfully synthesized in the embodiment 1 of the application.

[0073] 2, the crystal structures of TNA (anatase), CoMo-TNA (amorphous), CoMo-TNA (anatase) and CoMo-BTNT are determined by X-ray powder diffraction (XRD), and the results are shown in Figure 3 It can be seen from Figure 3 that the characteristic diffraction peaks of the TNA (anatase) sample are 25.1°, 37.8°, 47.9°, 53.8°, 54.9°, 70.5° and 76.2°, respectively, corresponding to the (101), (004), (200), (105), (211), (220) and (301) crystal planes of the TiO2 anatase phase, which basically corresponds to the standard card (PDF #21-1272), proving the successful synthesis of TNA (anatase); after direct current deposition and annealing calcination, the diffraction peaks of CoMo-TNA (amorphous) and CoMo-TNA (anatase) anatase phase are weakened, which may be due to the deposition of CoMo oxide layer on the top of TNA; a series of diffraction peaks appear in the range of 40°-50°, corresponding to the (200) crystal plane of Co3Mo, proving the successful introduction of CoMo oxide layer; compared with CoMo-TNA (anatase), CoMo-BTNT after cathodic reduction appears new diffraction peaks belonging to MoO3 and CoMoO4, proving the successful preparation of CoMo-BTNT.

[0074] Experimental Example 2

[0075] In order to prove the electrocatalytic degradation performance of CoMo-BTNT on tetracycline, the degradation method of the application is used to add the following experimental group systems to a plurality of same to-be-tested liquids to carry out tetracycline degradation experiments: CoMo-BTNT, E, PMS, PMS+E, CoMo-BTNT+E, CoMo-BTNT+PMS and CoMo-BTNT+PMS+E, wherein E represents power-on; the tetracycline degradation efficiency results in 60 min under different experimental group systems are shown in Figure 4 .

[0076] It can be seen from Figure 4 that ① when CoMo-BTNT is used alone, the removal rate of TC is 2.12%, which can be ignored; it is indicated that when CoMo-BTNT is used alone, the adsorption effect on tetracycline is weak, and no additional adsorption experiment is needed before removal.

[0077] ② In the system with only electricity (E), only 20.07% of TC was removed, which is because the electrochemical oxidation is not effective in removing pollutants.

[0078] ③When only PMS was used, the TC removal efficiency reached 22.67%, because PMS hydrolysis can produce SO4 ·- , OH, O2 ·- 、 1 O2 and other active substances.

[0079] ④ When CoMo-BTNT was added under power-on condition, the removal efficiency of TC increased to 44.46%, indicating that the introduction of electrochemistry can improve the catalytic degradation effect of CoMo-BTNT on tetracycline.

[0080] ⑤ In order to compare the activation behavior of PMS in the E+PMS system, under the same experimental conditions, the original Ti electrode was used as the anode to degrade TC, and the removal efficiency reached 41.82% within 60 min, which was attributed to the fact that the current could promote the removal of ·OH and SO4 ·- The production of OH and SO4 ·- Can be transformed into each other.

[0081] ⑥ Compared with the PMS system alone, the TC removal efficiency of the CoMo-BTNT+PMS system reached 63.59%, indicating that the prepared CoMo-BTNT can significantly activate PMS to generate active free radicals.

[0082] ⑦ In the E+CoMo-BTNT+PMS system, the removal efficiency of TC reached 91.63%, indicating that Co 2+ and Mo 6+ Can be converted into Co 3+ and Mo 5+ Therefore, CoMo-BTNT and PMS have obvious synergistic and reinforcing effects under the power-on state, which is optimal for the electrocatalytic degradation of tetracycline.

[0083] Experimental Example 3

[0084] This experiment was conducted to investigate the effects of different current density, PMS dosage, initial pH value and other factors on the electrocatalytic degradation performance of CoMo-BTNT for TC.

[0085] 3.1 Current density

[0086] When other experimental conditions were the same, different current densities were applied to evaluate the degradation effect of E+CoMo-BTNT+PMS system on TC. The results are shown in Figure 2. Figure 5 As shown by Figure 5It can be seen that:

[0087] When the current density is increased from 2.5 mA / cm 2 Increase to 5mA / cm 2 When the current density increases, the degradation efficiency of TC increases by about 9.3%. This is mainly because the formation of CoMo redox couples promotes the recycling of low-valent metals, thereby activating more PMS to produce active free radicals. When the current density continues to increase, the degradation efficiency of TC does not increase significantly. It is speculated that this may be because too high a current density will intensify the side reaction at the anode, and the side reaction at the anode will produce O2, which will react with HSO5 - Competing for electrons, leading to SO4 ·- The production of is reduced, and the redox potential is weaker. 1 O2, so that the degradation efficiency of TC by E+CoMo-BTNT+PMS system is not significantly improved. Considering all factors, the current density of 5mA / cm 2 As the optimal current density for subsequent reactions.

[0088] 3.2 PMS dosage

[0089] Effect of PMS dosage on the catalytic degradation of tetracycline Figure 6 As shown. Figure 6 The results show that in the E+CoMo-BTNT+PMS system, an important factor in the degradation of tetracycline is the PMS dosage. Within 60 minutes, when the PMS dosage increased from 0.5mM to 1.0mM, the removal efficiency of tetracycline increased from 63.14% to 86.13%. However, as the PMS dosage continued to increase, the removal effect of tetracycline did not improve significantly, and even showed a slight downward trend. This may be because excessive PMS has a negative effect on SO4 ·- It has a certain removal effect on ·OH.

[0090] 3.3 Initial pH

[0091] Based on SO4 ·- One of the most important factors affecting the advanced oxidation process (AOP) is pH, especially when it is combined with electrochemistry. In this study, the initial pH value ranged from 3 to 11 to investigate the effect of different initial pH values ​​on the degradation of tetracycline by the E+CoMo-BTNT+PMS system. Figure 7 As shown by Figure 7It can be seen that the removal efficiency of tetracycline is equivalent within 60 min when the initial pH value of the system solution is 11 and the initial pH value (i.e. the pH value without adjustment) is 3.85, although the removal efficiency of the system solution with the initial pH value of 11 is slightly (88.68%) higher than that of the initial solution system without adjustment of the pH value, because part of PMS is alkali-activated. When the initial pH values are 3, 5, 7 and 9 respectively, the degradation rate of tetracycline by the E+CoMo-BTNT+PMS system decreases to 70.07%, 83.98%, 84.31% and 79% respectively, because the solution of the over-acid will accelerate the protonation of HSO5 - , and PMS will be more quickly self-decomposed in neutral and alkaline solutions. Finally, considering the simplicity of operation, the initial pH value of 3.85 (without adjustment of the pH value) is still selected for the degradation of tetracycline.

[0092] Experimental Example 4

[0093] This experimental example is to explore the stability of CoMo-BTNT, which is as follows:

[0094] The CoMo-BTNT anode material prepared in Example 1 is subjected to a cycle test under the same operation to explore the stability of CoMo-BTNT anode for removing TC, and the results are shown in Table 2. Figure 8

[0095] Among them, the operation steps and reaction conditions of the cycle test are as follows:

[0096] 1. Material regeneration: after each cycle reaction, the CoMo-BTNT is first washed with ultrapure water, naturally air-dried, annealed at 450℃ for 1h, and then reduced for 5min with CoMo-BTNT as the cathode and Pt sheet as the anode at 5mA / cm 2 , washed with ultrapure water and naturally air-dried to obtain regenerated CoMo-BTNT

[0097] 2. Cycle test:

[0098] 1) The test is carried out under the conditions of current density of 5mA / cm 2 ; initial concentration of tetracycline = 30mg / L; concentration of sodium sulfate = 60mmol / L; PMS dosage = 1mmol / L; temperature is room temperature; pH value is 3.85, and the CoMo-BTNT is placed in the reaction solution and reacted for a period of time (0min, 180min, 360min, 540min, 720min, 900min) under the power-on state;

[0099]

[0100] ​​2) At 0 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, and 45 min, 1 mL of the reaction solution was drawn from the sampling port using a syringe, filtered through a 0.22 μm polyethersulfone filter, and placed into a quartz cuvette. The absorbance at 357 nm was detected using an ultraviolet spectrophotometer. After tetracycline degradation, the absorbance at 357 nm showed a good linear relationship with the tetracycline concentration in the concentration range of 0 to 45 mg / L. The linear regression equation established between the standard solution concentration and the absorbance was: y=0.02672x+0.01461, wherein x represents the tetracycline concentration and y represents the absorbance data at 357 nm. The concentration of tetracycline in the reaction solution was calculated according to the established linear regression equation.

[0101] Depend on Figure 8 It can be seen that after 5 cycles, the degradation efficiency of CoMo-BTNT for tetracycline decreased slightly, but only by 11.74%. The decrease in degradation effect may be due to the gradual occupation of active sites on the catalyst surface; and the degradation efficiency can still be achieved after 5 cycles, that is, it still maintains a high degradation efficiency. This shows that CoMo-BTNT has good stability.

Claims

1. A method for preparing a CoMo-BTNT anode, characterized in that: The following steps are involved: (1) Preparation of Ti substrate; (2) Preparation of titanium dioxide nanotube arrays using Ti substrate; (3) depositing a Co-Mo oxide layer deposition solution onto the surface of a titanium dioxide nanotube array by a direct current electrodeposition method, and then performing an annealing heat treatment to prepare CoMo-TNA; The specific steps include: (3.1) Prepare the Co-Mo oxide layer deposition solution: Mix CoSO₄·7H₂O, Na₃C₆H₅O₀·2H₂O, and Na₂MoO₄·2H₂O, and adjust the pH of the solution to 8-10 to obtain the Co-Mo oxide layer deposition solution. (3.2) Using a Pt sheet electrode as the anode and a TiO2 nanotube array as the cathode, the current density was 20-40 mA / cm 2 Co-Mo oxide layer deposition liquid is deposited onto the surface of titanium dioxide nanotube array by electrodeposition under certain conditions, and then annealing heat treatment is performed to obtain CoMo-TNA; (4) Using CoMo-TNA as cathode and Pt sheet as anode, the CoMo-BTNT anode was prepared by cathode reduction.

2. The method for preparing a CoMo-BTNT anode according to claim 1, wherein: When preparing the Ti substrate in step (1), the following steps are included: first, removing the oxide layer on the surface of the titanium foil, then cutting it into titanium sheets of the required size, then ultrasonically cleaning the titanium sheets, and sequentially subjecting the cleaned titanium sheets to acid treatment and heat treatment. When the surface of the titanium sheets becomes rough, the treatment is stopped, and the sheets are cleaned to obtain the Ti substrate.

3. The method for preparing a CoMo-BTNT anode according to claim 1, wherein: When preparing the titanium dioxide nanotube array in step (2), the following steps are included: using the Ti substrate as the anode and the Pt sheet as the cathode, performing a first anodization in an electrolyte containing fluoride ions for a period of time; then continuing to perform a second anodization in the electrolyte containing fluoride ions for a period of time, and finally flushing the electrolyte remaining on the surface of the Ti substrate to obtain the titanium dioxide nanotube array.

4. The method for preparing a CoMo-BTNT anode according to claim 1, wherein: In step (3), the deposition temperature is 40-60°C, and the deposition time is 3000-4000s; during the annealing heat treatment, the annealing is performed at 400-500°C for 1-3h.

5. The method for preparing a CoMo-BTNT anode according to claim 1, wherein: When preparing the CoMo-BTNT anode in step (4): CoMo-TNA is used as cathode and Pt sheet is used as anode. 2 Under certain conditions, the cathode is immersed in a formic acid solution and reduced for a period of time to obtain a CoMo-BTNT anode.

6. A CoMo-BTNT anode, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 5.

7. An application of a CoMo-BTNT anode, characterized in that: The CoMo-BTNT anode prepared by the preparation method according to any one of claims 1 to 5 is used for the degradation of antibiotics in water.

8. The use of the CoMo-BTNT anode according to claim 7, characterized in that: The degradation method of the antibiotic is: (1) Prepare the reaction solution: Mix the test solution with sodium sulfate and peroxymonosulfate to obtain a reaction solution. Place the CoMo-BTNT anode in the reaction solution and allow it to react for a period of time under power-on conditions. (2) Then, after filtering the reaction solution, measure the UV-visible absorbance of the reaction solution, and substitute the measured absorbance data into the linear equation of absorbance and antibiotic concentration to obtain the antibiotic concentration in the test solution.

Images