A method for simultaneous removal of antibiotics and Cr(VI) from wastewater based on multi-heterostructure titanium dioxide photoelectrodes

Abstract

The present invention relates to a method for synchronously removing antibiotics and Cr(VI) from wastewater based on a multi-heterostructure titanium dioxide photoelectrode. A three-electrode system is constructed with an Ag / AgVO3QDs@3D TiO2 photoelectrode as a working electrode, a 3D TiO2 as a counter electrode, and a saturated calomel electrode as a reference electrode. A water body containing OFL, Cr(VI), and an electrolyte is used as a treatment object. Under irradiation with a light source, a bias voltage is applied, and the OFL and Cr(VI) are synchronously removed by photoelectrocatalysis. The present invention can achieve synchronous removal of OFL and Cr(VI) (Cr(VI)) composite pollution in water, achieving 100% removal of OFL and Cr(VI) within 30 minutes under simulated sunlight. After five cycles, the removal rates of OFL and Cr(VI) remain at 97.8% and 90%, respectively, showing efficient and stable photoelectrocatalytic redox performance. After expanding the types of antibiotics to include norfloxacin and tetracycline, the target electrode still has a good ability to synchronously remove pollutants.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and relates to a method for synchronously removing OFL and Cr(VI) (i.e., hexavalent chromium) in sewage based on multi-heterostructure titanium dioxide photoelectrodes. Background Art

[0002] Since their discovery, antibiotics have not only been used in the field of human medicine, but also widely used in aquaculture and animal husbandry to increase crop yields. Among them, quinolone antibiotics are a type of antibiotic with a nitrogen (hetero) bicyclic structure as its skeleton. The accumulation of quinolone antibiotics in the human body is very likely to cause neurological diseases; Cr(VI) that enters the human body through various pathways accumulates in the human body due to its strong oxidizing and complexing properties, and in severe cases will cause DNA damage. At present, various physical, chemical, and biological technologies are used to treat OFL and Cr(VI) in water, such as adsorption, flocculation, and biosorption. However, these methods have disadvantages such as low efficiency, difficulty in recovery, and easy introduction of other pollutants. In the past few decades, advanced oxidation technologies (AOPs), including Fenton oxidation, electrochemical oxidation, photocatalytic oxidation, photoelectrocatalytic technology, and ozone oxidation technology, have become popular technologies for the green, efficient, and simultaneous removal of OFL and Cr(VI) in water. Research on the simultaneous removal of OFL and Cr(VI) using photocatalysis has been reported. Photocatalysts generate photogenerated electron-hole pairs under light excitation conditions. Photogenerated holes (h + ) as a strong oxidizing substance, can degrade OFL, some h + It can react with water to form highly active ·OH, promoting the mineralization of organic pollutants; photogenerated electrons (e - ) can act as a reducing agent to reduce Cr(VI). However, photocatalytic technology is limited by the material morphology, and photogenerated electrons and holes easily recombine, significantly affecting redox efficiency. Electrodes in photoelectrocatalytic technology, on the other hand, are highly recyclable, achieving, to a certain extent, the goal of green and sustainable pollutant degradation. Furthermore, under the action of an external electric field, photogenerated electrons and holes quickly separate, significantly improving the efficiency of the photoelectrocatalytic reaction.

[0003] Titanium dioxide (TiO2), being inexpensive, easy to synthesize, and non-toxic, stands out among many transition metal oxides and has become the most studied semiconductor photocatalyst. However, TiO2 has a wide band gap and can only absorb ultraviolet light to generate photogenerated carriers, resulting in a low solar light utilization rate of less than 5%. Furthermore, the surface of TiO2 contains numerous electron-hole recombination sites, resulting in a short carrier lifetime, which inhibits its photoelectrocatalytic performance to a certain extent. To broaden the light absorption range, constructing a heterogeneous interface is a good method to improve light absorption efficiency and charge separation efficiency. Increasing the specific surface area can be achieved by constructing a multi-level structure, thereby improving light absorption efficiency and charge injection efficiency. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for the simultaneous removal of antibiotics and Cr(VI) in sewage based on a multi-heterostructure titanium dioxide photoelectrode, which can significantly improve the light absorption efficiency and charge separation and transfer capability, and achieve efficient synergistic oxidation removal of OFL and Cr(VI) pollutants in water.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for simultaneously removing antibiotics and Cr(VI) from wastewater based on multi-heterostructure titanium dioxide photoelectrodes is proposed. A three-electrode system is constructed with Ag / AgVO3 QDs@3D TiO2 photoelectrode as the working electrode, 3D TiO2 as the counter electrode, and a saturated calomel electrode as the reference electrode. The water body to be treated containing antibiotics (taking OFL as an example), Cr(VI) and electrolyte is used as the treatment object. Under the irradiation of light source, bias voltage is applied, and the antibiotics and Cr(VI) therein are simultaneously removed by photoelectrocatalysis.

[0007] Furthermore, the preparation process of the 3D TiO2 is as follows:

[0008] Hydrochloric acid, hydrogen peroxide, and water were sequentially added to a high-pressure reactor, and a titanium mesh was placed therein for a gas-phase hydrothermal reaction. After the reaction was complete, the mixture was cooled to room temperature to obtain a 1D TiO2 electrode.

[0009] The 1D TiO2 electrode was placed in a mixed solution of hydrochloric acid, titanium trichloride solution and deionized water for a secondary hydrothermal reaction, followed by a heat treatment in an air atmosphere to obtain a 3D TiO2 electrode.

[0010] Furthermore, the titanium mesh was subjected to the following pretreatment before the gas-phase hydrothermal reaction: water, nitric acid (≥99.0%), and hydrofluoric acid (≥38 wt %) were mixed in a volume ratio of 50:10:2 to obtain a chemical polishing solution, the titanium mesh was immersed for 30 s, and deionized water and ethanol were ultrasonicated twice in sequence for 3-5 min.

[0011] Furthermore, during the gas-phase hydrothermal reaction, the volume ratio of hydrochloric acid, hydrogen peroxide, and water is 1:(0.25-0.35):(4.5-5.5), the mass fraction of hydrochloric acid is 36-38%, the mass fraction of hydrogen peroxide is 30%, and the gas-phase hydrothermal temperature is 180-220°C;

[0012] During the secondary hydrothermal reaction, the volume ratio of hydrochloric acid, titanium trichloride solution and deionized water satisfies (0.2-0.25):(0.1-0.15):(22-28), the mass fraction of hydrochloric acid is 36-38%, the concentration of titanium trichloride solution is 15-20wt%, and the temperature of the secondary hydrothermal reaction is 70-90°C;

[0013] The temperature of the heat treatment is 400-550°C.

[0014] Furthermore, the preparation process of the Ag / AgVO3 QDs@3D TiO2 photoelectrode is as follows:

[0015] S1. Add solid ammonium metavanadate to the silver nitrate solution, shield from light and stir, then adjust the solution to pH 7, transfer it to a high-pressure reactor, add the 3D TiO2 electrode, and perform a hydrothermal reaction. After the reaction is completed, cool it to room temperature to obtain the AgVO3 QDs@3DTiO2 electrode;

[0016] S2. Place the AgVO3 QDs@3D TiO2 electrode in a AgNO3 solution, shield it from light and stir it, then perform a photodeposition reaction under simulated sunlight. After the reaction is completed, wash the electrode with deionized water and dry it to obtain the Ag / AgVO3QDs@3D TiO2 photoelectrode material.

[0017] Furthermore, in S1, the concentration of the silver nitrate solution is 1.0-2.0 mM, preferably 1.5 mM, the molar ratio of silver nitrate to ammonium metavanadate is 1:1, and the light-shielding stirring time is more than 1 hour.

[0018] Furthermore, in S1, the temperature of the hydrothermal reaction is 150-250° C., and the time is 5-7 h.

[0019] Furthermore, in S2, the concentration of the AgNO3 solution is 0.05-0.5 M, the illumination time in the photodeposition reaction is 10-20 min, and the light intensity of the light source is 50-200 mW / cm 2 .

[0020] Furthermore, in the water to be treated, the concentrations of antibiotics (preferably OFL, i.e., ofloxacin) and Cr(VI) are both 2-5 mg / L, and the concentration of the electrolyte is 0.1-0.4 mol / L.

[0021] Furthermore, the electrolyte is sodium sulfate.

[0022] Furthermore, during the photoelectrocatalytic process, a xenon lamp light source equipped with an AM 1.5G filter can be used to simulate the solar spectrum, with a light intensity of 50 to 200 mW / cm 2 , the applied bias voltage is +0.2~+1.0V, and the degradation time is 20~40min.

[0023] The titanium source in the present invention is a titanium mesh, which can serve as a site for the in-situ growth of titanium dioxide. The rapid transfer of electrons relies on uniform, upright nanorods obtained through vapor-phase hydrothermal treatment. Nanocones are grown on the nanorods through secondary hydrothermal treatment to form a three-dimensional structure, significantly improving the efficiency of charge transfer and reaction mass transfer. AgVO3 quantum dots are further loaded through a hydrothermal reaction. AgVO3, as a narrowband semiconductor, broadens the material's light absorption range when combined with TiO2, improving light absorption efficiency. The pn junction formed by AgVO3 and TiO2 facilitates the separation and rapid transfer of photogenerated electrons and holes. Photogenerated electrons are transferred from AgVO3 on the photoanode to TiO2 and then to the photocathode through an external circuit. Ag quantum dots are further loaded through photodeposition, utilizing the surface plasmon effect to further enhance the light absorption efficiency of the electrode material. The introduction of Ag enhances the electrode's conductivity, improving the efficiency of electron transfer to a certain extent. This Ag / AgVO3 QDs@3D TiO2 photoelectrode can achieve 100% OFL and Cr(VI) removal efficiency within 30 min under simulated sunlight.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) Using 3D TiO2 as the substrate electrode, the high specific surface area of ​​its three-dimensional structure and the crystal plane heterojunction composed of three highly exposed crystal planes ({111}, {101} and {110}) not only improve the efficiency of fast and efficient selective spatial separation of electrons and holes generated by photogeneration, but also increase the high specific surface area of ​​the material and provide abundant active sites.

[0026] (2) AgVO3 quantum dots are loaded on the 3D TiO2 surface. AgVO3, as a narrow bandgap semiconductor, helps improve the light absorption capacity of the substrate electrode and effectively broadens the light absorption range. Moreover, the quantum dots are small in size, providing active sites without blocking the active crystal surface. At the same time, the energy bands of AgVO3 and TiO2 match, forming a heterojunction, which promotes the transfer of holes to AgVO3 and the transfer of photogenerated electrons to TiO2. The synergistic effect of the AgVO3 / TiO2 heterojunction and the TiO2 polycrystalline heterojunction greatly increases the separation and transfer rate of photogenerated carriers.

[0027] The surface plasmon effect of Ag quantum dots helps to expand the light absorption range of TiO2 electrodes, and the loading of Ag enhances the conductivity of TiO2, increases the transfer rate of photogenerated electrons, and enhances the separation ability of photogenerated carriers.

[0028] (3) The present invention is based on the prepared Ag / AgVO3 QDs@3D TiO2 photoelectrode to construct a photoelectrocatalytic system. By using the effect of external bias, the transfer of photogenerated electrons is further promoted, and the separation efficiency and utilization efficiency of photogenerated charges are effectively improved. At the same time, through the synergistic effect of anodic oxidation of OFL and cathode reduction of Cr(VI), efficient photoelectrocatalytic synergistic removal of two pollutants, OFL and Cr(VI), in water can be achieved. This photoelectrocatalytic system.

[0029] (4) The photoelectrocatalytic synergistic system constructed in this invention exhibits excellent stability and recyclability in the simultaneous removal of OFL and Cr(VI) complex pollutants from water. After five cycles, the target electrode still achieved a 97.8% OFL removal rate and a 92.5% Cr(VI) removal rate. Furthermore, this system can be expanded to remove other antibiotic and Cr(VI) complex pollutants in real-world water, such as norfloxacin and tetracycline. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Scanning electron microscopy images of 3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3 QDs@3DTiO2 prepared in Example 1;

[0031] Figure 2 A comparison chart of the photoelectric properties of 3D TiO2, Ag QDs@3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3QDs@3D TiO2 prepared in Example 1;

[0032] Figure 3 Fluorescence spectra and time-resolved transient fluorescence spectra of 3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3 QDs@3DTiO2 photoelectrodes prepared in Example 1;

[0033] Figure 4 UV-vis-DRS spectra, open circuit voltage and light absorption efficiency curves of 3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3 QDs@3DTiO2 photoelectrodes prepared in Example 1

[0034] Figure 5 The removal efficiency of OFL and Cr(VI) by different photoelectrocatalytic systems composed of 3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3 QDs@3DTiO2 prepared in Example 1 and the corresponding kinetic fitting curves;

[0035] Figure 6The removal efficiency of other antibiotics and Cr(VI) by the photoelectrocatalytic system composed of Ag / AgVO3 QDs@3D TiO2 and 3D TiO2 prepared in Example 1 and the corresponding kinetic fitting curves;

[0036] Figure 7 Cyclic test of OFL oxidation and Cr(VI) reduction of the photoelectrocatalytic system composed of Ag / AgVO3 QDs@3D TiO2 and 3D TiO2 prepared in Example 1;

[0037] Figure 8 Cyclic performance test of the photoelectrocatalytic system composed of Ag / AgVO3 QDs@3D TiO2 and 3D TiO2 in Example 1 DETAILED DESCRIPTION

[0038] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0039] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercial products or conventional processing techniques in the art.

[0040] Example 1

[0041] A method for simultaneously removing antibiotics and Cr(VI) from wastewater based on a multi-heterostructure titanium dioxide photoelectrode, specifically comprising the following steps:

[0042] (1) Chemical polishing pretreatment: Fold the 80-mesh titanium mesh into a double layer and cut it into a size of 2.5 cm × 3 cm. Mix HNO3 (≥99.0%), HF (≥38 wt%) and H2O in a volume ratio of 5:1:25 to prepare a chemical polishing solution. Soak the cut titanium mesh in the solution for 30 seconds as a pretreatment. After the treatment, ultrasonically clean it twice in water and ethanol for 3-5 minutes respectively, and then soak it in ethanol for later use.

[0043] (2) Gas-phase hydrothermal: 5 mL of deionized water, 300 μL of hydrogen peroxide (30%), and 1.0 mL of hydrochloric acid (37.0 wt%) were added sequentially to the lining of a 100 mL polytetrafluoroethylene-based reactor with a 7 cm high ring support. The pretreated dry titanium mesh was placed on the ring support in the lining, and the lining was placed in a high-pressure reactor. The gas-phase hydrothermal reaction was carried out at 200 ° C for 5 h. After the reaction was completed, it was cooled to room temperature, the electrode was taken out, the surface was rinsed with deionized water, and it was naturally dried to obtain a 1D TiO2 photoelectrode.

[0044] (3) Secondary hydrothermal reaction: 25 mL of deionized water, 210 μL of hydrochloric acid (37.0%), and 125 μL of titanium trichloride solution (18 wt%) were added to the inner lining of a 100 mL polytetrafluoroethylene-based reactor, and the solution was shaken to mix evenly. The 1D TiO2 photoelectrode prepared in step (2) was placed therein, and the inner lining was placed in a high-pressure reactor. The hydrothermal reaction was carried out at 80°C for 4 h. After the reaction was completed, the reaction was cooled to room temperature, the electrode was taken out, the surface was rinsed with deionized water, and the electrode was naturally dried.

[0045] (4) The photoelectrode prepared in step (3) was placed in a muffle furnace and calcined at 450°C in an air atmosphere at a heating rate of 3°C / min for 2 hours. After the calcination was completed, the electrode was cooled to room temperature and taken out to obtain a 3D TiO2 photoelectrode.

[0046] (5) Prepare 30 ml of 1.5 mM silver nitrate solution, add the same amount of ammonium metavanadate solid thereto, shade the solution and stir for more than 1 hour, then adjust the solution pH to 7 with NaOH solution (concentration is 2.5 mol / L), add the above solution to the lining of a 100 mL polytetrafluoroethylene-based reactor, place the 3D TiO2 photoelectrode prepared in step (4) therein, place the lining in a high-pressure reactor, and perform hydrothermal reaction at 200 ° C for 6 hours. After the reaction is completed, cool to room temperature, take out the electrode, rinse the surface with deionized water, and dry it naturally to obtain the AgVO3 QDs@3D TiO2 photoelectrode.

[0047] (6) Prepare 20 ml of 0.1 M silver nitrate solution, place the AgVO3 QDs@3D TiO2 photoelectrode prepared in step (5) in it, shield and stir for 20 minutes, and then simulate sunlight (light source intensity of 100 mW / cm 2 ) for 15 min. After the reaction, the electrode was taken out, the surface was rinsed with deionized water, and dried naturally to obtain the target electrode Ag / AgVO3QDs@3D TiO2.

[0048] (7) Different photoelectrocatalytic systems were formed using the prepared 3D TiO2, AgVO3 QDs@3D TiO2, and Ag / AgVO3 QDs@3DTiO2 to remove simulated wastewater containing OFL and Cr(VI). The specific process is as follows:

[0049] The photoelectrocatalytic experiments were carried out in a 50 mL cuboid quartz degradation cell. A three-electrode system was used. Different dual-photoelectrode photoelectrocatalytic systems were constructed based on 3D TiO2, AgVO3 QDs@3D TiO2, and Ag / AgVO3 QDs@3D TiO2 as photoanodes and 3D TiO2 as photocathodes. A saturated calomel electrode was used as the reference electrode. The distance between the working electrode and the counter electrode was 5 cm, and the effective photoelectrode area was 2.5 × 3 cm. 2 The simulated wastewater is 0.1 mol·L -1 A mixed solution of sodium sulfate, 5 mg / L 0.1 mol ... 2 The distance between the sample cell and the light source was 25 cm, the bias voltage was +0.4 V (relative to the saturated calomel electrode), and the photoelectrocatalytic experiment was carried out. The reaction time was 40 min, and samples were taken at regular intervals. The concentrations of OFL and Cr(VI) in the samples were tested by UV-1800 ultraviolet spectrometer. The specific degradation results are shown in Figure 2. Figure 4 shown. Figure 4 In the figure, (a) and (c) represent the removal curves of OFL and Cr(VI), respectively, and (b) and (d) represent the corresponding kinetic curves.

[0050] Figure 4 Test results show that the Ag / AgVO3 QDs@3D TiO2-3D TiO2 photoelectric system successfully achieved efficient photoelectrocatalytic removal of OFL and Cr(VI) in wastewater. After 30 minutes of reaction, the removal rates of both OFL and Cr(VI) reached 100%, indicating that the synergistic photoelectrocatalytic system constructed by the Ag / AgVO3 QDs@3D TiO2 photoanode and 3D TiO2 photocathode achieved efficient and simultaneous removal of OFL and Cr(VI) pollutants in water.

[0051] Performance Testing

[0052] 1. Scanning Electron Microscope Analysis

[0053] The micromorphology of the electrodes was characterized by field emission scanning electron microscopy (Hitachi S-4800). Figure 1 , Figure 1 The clear structure of each electrode prepared in Example 1 is shown. First, 1D TiO2 with a one-dimensional nanorod structure can be observed growing on the titanium mesh substrate. Secondly, evenly distributed nanocones are observed growing on the surface of the nanorods, which is 3D TiO2 with a three-dimensional structure. The loading of Ag and AgVO3 quantum dots does not destroy the three-dimensional structure, but the edges of the nanocones become blunt.

[0054] 2. Photoelectrochemical performance test

[0055] The photoelectrocatalytic oxidation performance of 3D TiO2, Ag QDs@3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3 QDs@3D TiO2 photoelectrodes prepared in Example 1 were studied. The specific steps are as follows:

[0056] The specific preparation process of Ag QDs@3D TiO2 is as follows:

[0057] The 3D TiO2 photoelectrode prepared in Example 1 was placed in 20 ml of 0.1 M silver nitrate solution, shielded from light and stirred for 20 min, and then exposed to simulated sunlight (light source intensity of 100 mW / cm 2 ) for 15 min. After the reaction, the electrode was taken out, the surface was rinsed with deionized water, and dried naturally to obtain Ag QDs@3DTiO2.

[0058] The photoelectrocatalytic performance test was carried out in a square quartz reaction cell. The electrolyte solution was 0.1 mol / L sodium sulfate solution. A three-electrode system was used, with 3D TiO2, Ag QDs@3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3 QDs@3D TiO2 as working electrodes, platinum as counter electrode, and saturated calomel electrode as reference electrode. The transient photocurrent response curve, linear sweep voltammetry curve, Mott-Schottky curve and AC impedance spectrum were tested using a Chenhua CHI660C electrochemical workstation. A xenon lamp was used as the light source, and the distance between the light source and the working electrode was 1 cm. The test results are shown in Figure 2. Figure 2 The results show that under light conditions, the photoresponse performance of the Ag / AgVO3QDs@3D TiO2 electrode is better than that of Ag QDs@3D TiO2, AgVO3QDs@3D TiO2 and 3D TiO2, and the photocurrent density of the Ag / AgVO3 QDs@3D TiO2 electrode can reach 0.85 mA / cm 2 , which is 1.7 times that of 3D TiO2, with an impedance value of approximately 408Ω, and a calculated carrier concentration of 6.33×10 20 cm -3 .

[0059] 3. Fluorescence spectroscopy and time-resolved transient fluorescence spectroscopy testing

[0060] The 3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3 QDs@3DTiO2 photoelectrodes prepared in Example 1 were used to perform fluorescence spectroscopy and time-resolved transient fluorescence spectroscopy tests. Figure 3, indicating that the loading of Ag and AgVO3 quantum dots significantly improved the separation efficiency of TiO2 photogenerated charges and effectively extended the lifetime of photogenerated electrons (3D TiO2: 13.35ns; AgVO3QDs@3D TiO2: 14.52ns; Ag / AgVO3 QDs@3DTiO2: 15.97ns), which correspondingly improved the rate of electron transfer. The holes of the photoanode can participate in the oxidation reaction more efficiently, thereby theoretically improving the efficiency of oxidative degradation of OFL.

[0061] 4. UV-Vis diffuse reflectance test

[0062] The UV-visible diffuse reflectance test was performed using the 3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3 QDs@3DTiO2 photoelectrodes prepared in Example 1. Figure 4 a, indicating that the loading of Ag and AgVO3 quantum dots promotes the light absorption ability of TiO2 and expands its light absorption range. Figure 4 b shows that through calculation, it was found that after loading Ag and AgVO3 quantum dots, the band gap of the photoelectrode became 2.5eV, indicating that the band gap of the target photoelectrode became smaller, thereby improving the light absorption efficiency. Figure 4 The open circuit voltage drop of the target electrode in c is the largest, further confirming the improvement of the electrode light absorption efficiency. Figure 4 d is the light absorption efficiency curve of the three electrodes. It is observed that at an operating voltage of 0.4V, the target electrode exhibits the best light absorption efficiency, reaching 70.64%, which is 1.44 times higher than that of the 3D TiO2 photoelectrode.

[0063] 5. Test of OFL and Cr(VI) removal effects using 3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3QDs@3D TiO2 photoelectrodes prepared in Example 1

[0064] Different photoelectrocatalytic systems were constructed using the 3D TiO2, AgVO3 QDs@3D TiO2 and Ag / AgVO3 QDs@3DTiO2 photoelectrodes prepared in Example 1 to remove OFL and Cr(VI) in water. The results are shown in Figure 2. Figure 5 The results showed that the removal rate of OFL by the target electrode reached 100% within 20 min, and the first-order kinetic constant was 0.292×10 -3 min -1 , which is 3.52 times that of 3D TiO2; for the removal of Cr(VI), the photoelectric system composed of the target electrode and 3D TiO2 can achieve 100% removal of Cr(VI) within 30 minutes, and the secondary kinetic constant is 0.227M -1 min-1 , which is 3.27 times that of 3D TiO2. In summary, the target electrode can achieve efficient and simultaneous removal of OFL and Cr(VI) in water;

[0065] The types of antibiotics were expanded to norfloxacin and tetracycline, and the effects of 3D TiO2, AgVO3 QDs@3DTiO2 and Ag / AgVO3 QDs@3D TiO2 photoelectrodes on the simultaneous removal of antibiotics and Cr(VI) were investigated. Figure 6 As shown, within 40 minutes, the target electrode system achieved a 100% removal rate for both norfloxacin and Cr(VI) in the coexistence of norfloxacin and Cr(VI). In the coexistence of tetracycline and Cr(VI), the removal rates reached 90% for tetracycline and 88% for Cr(VI). This demonstrates the universal applicability of the photoelectrocatalytic system composed of the target electrode and 3D TiO2 for the efficient removal of antibiotics and Cr(VI).

[0066] 6. Cyclic test of the removal effect of OFL and Cr(VI) using the Ag / AgVO3 QDs@3D TiO2 photoelectrode prepared in Example 1

[0067] The Ag / AgVO3 QDs@3D TiO2 photoelectrode prepared in Example 1 was used to construct a photoelectrocatalytic system, and the cyclic stability of the OFL and Cr(VI) removal effect in water was tested. The results are shown in Figure 2. Figure 7 As shown in the figure, after 5 cycles, the OFL removal rate at the anode can still reach 97.8%, indicating that the target electrode has good stability. At the same time, the photoelectric cycling performance of the photoelectrocatalytic system composed of Ag / AgVO3 QDs@3D TiO2 and 3D TiO2 was tested. During the 12,000s cycle test, the photoelectrocatalytic system showed a relatively stable photocurrent with an average value of 0.95mA, further confirming the cyclic stability of the target electrode.

[0068] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for simultaneously removing antibiotics and Cr(VI) from sewage based on a multi-heterostructure titanium dioxide photoelectrode, characterized in that: A three-electrode system was constructed with Ag / AgVO3 QDs@3D TiO2 photoelectrode as the working electrode, 3D TiO2 as the counter electrode, and a saturated calomel electrode as the reference electrode. The treated water body containing antibiotics, Cr(VI), and electrolyte was used as the treatment object. Under light irradiation and bias voltage, the antibiotics and Cr(VI) were removed simultaneously by photoelectrocatalysis. The preparation process of the 3D TiO2 is as follows: Hydrochloric acid, hydrogen peroxide, and water were sequentially added to a high-pressure reactor, and a titanium mesh was placed therein for a gas-phase hydrothermal reaction. After the reaction was complete, the mixture was cooled to room temperature to obtain a 1D TiO2 electrode. The 1D TiO2 electrode was placed in a mixed solution of hydrochloric acid, titanium trichloride solution and deionized water for a secondary hydrothermal reaction, followed by a heat treatment in an air atmosphere to obtain a 3D TiO2 electrode. The preparation process of the Ag / AgVO3 QDs@3D TiO2 photoelectrode is as follows: S1. Add solid ammonium metavanadate to the silver nitrate solution, shield from light and stir, then adjust the solution to pH 7, transfer it to a high-pressure reactor, add the 3D TiO2 electrode, and perform a hydrothermal reaction. After the reaction is complete, cool it to room temperature to obtain the AgVO3 QDs@3DTiO2 electrode. S2, placing the AgVO3 QDs@3D TiO2 electrode in a AgNO3 solution under light shielding and stirring, and then performing a photodeposition reaction under simulated sunlight. After the reaction is completed, the electrode is washed with deionized water and dried to obtain an Ag / AgVO3 QDs@3D TiO2 photoelectrode material; In S1, the hydrothermal reaction temperature is 150-250 °C and the time is 5-7 h; The antibiotic is OFL, norfloxacin or tetracycline.

2. The method for simultaneously removing antibiotics and Cr(VI) from sewage based on a multi-heterostructure titanium dioxide photoelectrode according to claim 1, characterized in that: During the gas-phase hydrothermal reaction, the volume ratio of hydrochloric acid, hydrogen peroxide, and water is 1: (0.25-0.35): (4.5-5.5), the mass fraction of hydrochloric acid is 36-38%, the mass fraction of hydrogen peroxide is 30%, and the gas-phase hydrothermal temperature is 180-220°C; During the secondary hydrothermal reaction, the volume ratio of hydrochloric acid, titanium trichloride solution, and deionized water satisfies (0.2-0.25):(0.1-0.15):(22-28), the mass fraction of hydrochloric acid is 36-38%, the concentration of titanium trichloride solution is 15-20 wt%, and the temperature of the secondary hydrothermal reaction is 70-90°C. The heat treatment temperature is 400~550℃.

3. The method for simultaneously removing antibiotics and Cr(VI) from sewage based on a multi-heterostructure titanium dioxide photoelectrode according to claim 1, characterized in that: In S1, the concentration of the silver nitrate solution is 1.0-2.0 mM, the molar ratio of silver nitrate to ammonium metavanadate is 1:1, and the light-shielded stirring time is more than 1 h.

4. The method for simultaneously removing antibiotics and Cr(VI) from wastewater based on a multi-heterostructure titanium dioxide photoelectrode according to claim 1, characterized in that: In S2, the concentration of AgNO3 solution is 0.05~0.5 M, the illumination time in the photodeposition reaction is 10~20 min, and the light intensity of the light source is 50~200 mW / cm 2 .

5. The method for simultaneously removing antibiotics and Cr(VI) from wastewater based on a multi-heterostructure titanium dioxide photoelectrode according to claim 1, characterized in that: In the water to be treated, the concentrations of antibiotics and Cr(VI) are both 2-5 mg / L, and the electrolyte is sodium sulfate, with a concentration of 0.1-0.4 mol / L.

6. The method for simultaneously removing antibiotics and Cr(VI) from wastewater based on a multi-heterostructure titanium dioxide photoelectrode according to claim 1, characterized in that: During the photoelectrocatalytic process, the light intensity of the light source is 50~200 mW / cm 2 , the applied bias voltage is +0.2~+1.0V, and the degradation time is 20~40min.

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