Preparation method of phosphorus-doped electrode inducing Ti4O7 lattice strain and application of the electrode in electrocatalytic reinforcement of advanced purification of medical wastewater

Abstract

A method for preparing a phosphorus-doped electrode inducing Ti4O7 lattice strain and its application in electrocatalytic enhanced advanced purification of pharmaceutical wastewater. Through the in-situ P-doping process, PH3 generated on the surface of Ti4O7 undergoes redox reaction to form new O vacancies, and P is doped into the Ti4O7 lattice to form Ti-O-P structure. O vacancies are conducive to improving the conductivity of the system, and can also increase the Ti 3+ active sites, strengthen · OH production. The construction of P sites can realize its adjustment of CO3 2‑ adsorption and activation, and further reduce its conversion to CO3 ·‑ reaction energy barrier, inhibit CO3 2‑ quenching of · OH. At the same time, in the process of CO3 ·‑ , CO3 2‑ transfers electrons to the electrode surface, which effectively migrates to Ti 3+ sites through O vacancies, inhibits the tendency of high-valence conversion in the catalytic process, thereby realizing · OH stable and efficient production, and effectively degrading antibiotics in pharmaceutical wastewater.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering technology, and relates to the research on the preparation technology of phosphorus-doped Ti4O7 electrode materials, and to the preparation of an electrode with phosphorus doping-induced Ti4O7 lattice strain and its application in the electrocatalytic enhancement of the deep purification of pharmaceutical wastewater. Background Technology

[0002] Two major challenges of this century are energy scarcity and increasingly severe environmental pollution. As the world's population continues to grow at an unprecedented rate, the demand for clean and usable water is also increasing. Furthermore, changes in living standards and industrial development are releasing new or organic pollutants into water bodies, adding further pressure to the aquatic environment. As the world's largest producer and exporter of antibiotics, China inevitably generates large amounts of pharmaceutical wastewater containing high concentrations of antibiotics during its pharmaceutical production processes. With the rapid development of the domestic pharmaceutical industry, the levels of residual highly toxic and refractory antibiotics in water bodies are constantly increasing, posing a potential threat to ecosystems and human safety. However, traditional biological wastewater treatment technologies have low efficiency, insufficient to completely remove or degrade antibiotics in wastewater, and high energy consumption and carbon emissions increase the cost of pollutant treatment.

[0003] Electrocatalysis has advantages such as high treatment efficiency, no secondary pollution, and simple operation, and is widely used in the treatment of pharmaceutical wastewater. Hydroxyl radicals ( · OH) is one of the most important active species in electrocatalytic systems, possessing extremely strong oxidizing properties (redox potential 2.8V). CO3 is ubiquitous in actual water bodies. 2- Generally considered · An effective quencher of OH, thereby inhibiting · OH plays a role. However, there is currently no way to inhibit CO3. 2- right · Materials quenched by OH radicals. And carbonate free radicals (CO3) ·- Higher selectivity, and CO3 in natural water bodies ·- The steady-state concentration is higher than · OH, therefore CO3 ·- Ti4O7 has potential applications in limiting the persistence of various organic pollutants. It exhibits a high oxygen evolution potential (>2.5 V vs SHE) and excellent electrical conductivity (1500 S cm⁻¹). −1 With its good properties of high permeability and corrosion resistance, Ti4O7 is a common electrocatalytic material. However, the interfacial charge transfer rate of pure Ti4O7 is relatively low, leading to low mass transfer efficiency in the reaction system and insufficient mass transfer during the electrocatalytic process. ·OH radicals are used for pollutant degradation. Therefore, modification strategies are needed to improve the performance of Ti4O7 in electrocatalytic pollutant degradation. Based on the above issues, the articles "Photochemical degradation of oxytetracycline: Influence of pH and role of carbonate radical" and "Defect Engineering on a Ti4O7 Electrode by Ce" address these issues. 3+ Doping for the Efficient Electrooxidation of Perfluorooctanesulfonate” respectively involves photoactivation of CO3 in a UV / H2O2 system. 2- Ce 3+ Doped Ti4O7 electrodes enhance the degradation of organic pollutants. Although the above studies can inhibit CO3 to some extent... 2- right · The quenching effect of OH promotes electron transfer on the Ti4O7 electrode surface, but requires the use of ultraviolet light sources, which increases energy consumption. Furthermore, the high material requirements of ultraviolet light also increase the cost of device construction. 3+ The doping of metal ions on the Ti4O7 electrode surface can lead to irreversible leaching, causing secondary pollution to water bodies. Furthermore, the aforementioned modified materials increase surface active sites and promote the catalytic generation of active species (…). · There is still considerable room for improvement in areas such as OH generation.

[0004] Therefore, this application selects Ti4O7 as the anode substrate material and constructs Ti-OP with Ti and P dual reaction active sites by in-situ P doping to regulate the lattice structure of the system. 3+ As · OH generation sites, Ti after P doping 3+ The proportion of oxygen vacancies increased significantly, which is beneficial for promoting... · The formation of OH. Compared to metal doping, nonmetallic doping of P involves P atoms forming a stable coordination structure with Ti ions in Ti4O7 through coordinate bonds, which effectively suppresses the dissolution of nonmetallic ions. As the reaction proceeds, Ti... 3+ It will gradually decrease, Ti 4+ Gradually increasing, · The rate of OH production is limited. P sites can adsorb CO3. 2- Thus inhibiting · Quenching of OH. CO3 adsorbed on the P site. 2- Once activated, it easily loses electrons and transforms into CO3. ·-The doping of P and the presence of more oxygen vacancies create directional electron migration channels in the system (P→Ti). 3+ ), inhibited Ti 3+ The trend towards higher price levels, thus... · OH can be generated continuously and stably, achieving the goal of efficient and low-consumption electrocatalytic degradation of antibiotics in pharmaceutical wastewater. Summary of the Invention

[0005] This invention provides a method for preparing a p-doped titanium suboxide electrode (Ti4O7-P) material, and its application in the electrocatalytic activation of CO3. 2- Degradation of antibiotics in pharmaceutical wastewater. By constructing a Ti-OP structure, the PO bonds can adsorb CO3. 2- Thus inhibiting · Quenching of OH. Using Ti 3+ As · OH generation sites, Ti after P doping 3+ The increased proportion of oxygen vacancies promotes · The formation of OH. As the reaction proceeds, Ti... 3+ It will gradually decrease, Ti 4+ Gradually increasing, · The rate of OH production is limited. CO3 adsorbed on the PO bond... 2- It easily loses electrons and transforms into CO3 ·- P doping and more oxygen vacancies promote electron transfer to Ti. 4+ ,make · OH can be generated continuously and stably, achieving the goal of electrocatalytically degrading antibiotics in pharmaceutical wastewater.

[0006] The technical solution of the present invention:

[0007] A method for preparing an electrode with phosphorus doping-induced Ti4O7 lattice strain, comprising the following steps:

[0008] An electrode plate coated with a Ti4O7 film and sodium hypophosphite monohydrate were placed in two separate ceramic boats. The two boats were then placed in the middle of a tube furnace, with the sodium hypophosphite monohydrate positioned upwind of the furnace. The distance between the electrode plate and the sodium hypophosphite monohydrate was 4-6 cm. Under a nitrogen atmosphere, the heating rate was 0.5-5 °C / min, the reaction temperature was 250-400 °C, and the reaction time was 1-4 h. After calcination, the mixture was allowed to cool naturally to room temperature. The electrode plate was then removed and placed in an electrochemical reduction reactor as the cathode, with a lead oxide electrode as the anode. The electrolyte was an ammonium fluoride solution, and the reaction proceeded at a rate of 5 mA / cm². 2 The Ti4O7 lattice strain electrode was obtained by running in constant current mode for 2 minutes.

[0009] The thickness of the Ti4O7 film is 50-100 μm.

[0010] The ratio of the area of ​​the electrode plate to the amount of sodium hypophosphite monohydrate added is 0.1-1.0 g of sodium hypophosphite monohydrate per square centimeter of electrode.

[0011] The ammonium fluoride solution is a mixture of ethylene glycol, ammonium fluoride and water in a mass ratio of 90:2:8.

[0012] The application of a Ti4O7 lattice strain electrode in the electrocatalytic enhancement of deep purification of pharmaceutical wastewater includes the following steps:

[0013] An electrochemical degradation system was constructed using a Ti4O7 lattice strain electrode as the anode and a Ti plate as the cathode; at 1-20 mA / cm 2 Under constant current conditions, at a reaction temperature of 24℃-26℃, using SMX wastewater with a concentration of 5-40 mg / L as the target, CO3... 2- With a content of 1-10 mM and a reaction time of 30 min, the SMX degradation rate can reach over 99%.

[0014] The beneficial effects of this invention: In the method of this invention, the crystal structure of the system is controlled by in-situ P-doping Ti4O7, thereby improving the system's response to CO3 under electrocatalytic conditions. 2- Activate and strengthen at the same time · The OH generation rate is improved to achieve efficient and low-consumption degradation of antibiotics in pharmaceutical wastewater. The PH3 generated during the in-situ P doping process in step 1 undergoes a redox reaction on the Ti4O7 surface, forming numerous new O vacancies. Simultaneously, P doping is incorporated into the Ti-OP structure within the Ti4O7 crystal lattice. These O vacancies can induce localization within the crystal lattice. A mixed valence network enables rapid electron migration within the system through a small polaritron hopping mechanism. Each O vacancy generates two Ti³ sites. This directly increases the density of surface active sites. Ti³ The active site weakens the OH bond through coordination, promoting H+ ionization. O dissociates to generate · OH. By constructing appropriate P sites and utilizing tunable local electronic microenvironments, its control over CO32- can be achieved. 2- Adsorption and activation, thereby reducing its conversion to CO3 ·- Reaction energy barrier, inhibiting CO3 2- right · The quenching effect of OH. If the P doping concentration is insufficient, P atoms cannot be fully embedded in the Ti-O lattice, failing to form sufficient lattice strain. This results in limited oxygen vacancy concentration and a limited number of exposed active sites, affecting the activity of redox reactions on the electrode surface. Furthermore, low-concentration P doping is difficult to effectively control. The positions of the conduction and valence bands lead to an undesirable distribution of electronic states on the material surface, resulting in a limited improvement in conductivity and a reduced ability to adsorb and activate reaction intermediates. Excessive P leads to... An imbalance in the ratio causes the catalyst's d-band center to shift excessively upwards, resulting in overly strong adsorption of intermediate products (e.g., ...). · Phosphorus doping (P₂O₃) hinders subsequent reaction steps. High concentrations of P doping induce lattice distortion accumulation, leading to the distortion and even local collapse of the Ti-O octahedral structure, reducing the material's mechanical stability and cycle life. Excessive heating rates result in insufficient P atom diffusion, leading to localized P enrichment and the formation of inactive phosphorus oxide layers (such as PO₄²⁻). This process induces lattice stress concentration, leading to microcracks and grain boundary embrittlement. Slowly increasing the temperature prolongs the high-temperature dwell time, causing phosphorus (P) to segregate to the grain boundaries (P concentration at grain boundaries reaches 3-5 times that of the bulk phase), forming an inactive TiPO4 interface layer that hinders electron transport. Simultaneously, CO3 is generated. ·- During the process, CO3 2- Electrons are transferred to the electrode surface, and these electrons can migrate efficiently to Ti through oxygen vacancies. 3+ Sites that inhibit the tendency of catalytic conversion to higher valence states during catalysis, thereby achieving · OH is generated stably and efficiently. Therefore, this material can achieve CO3 production. 2- Existence · OH groups stably generate highly efficient electrocatalytic degradation of antibiotics. Furthermore, this preparation method is simple and low-cost, possessing the potential for industrial-scale production. Attached Figure Description

[0015] Figure 1 Image of a Ti4O7-P electrode material sample.

[0016] Figure 2 The images show TEM elemental surface scans of the Ti4O7-P electrode material, where (a) is the surface scan of P and (b) are the surface scans of Ti, O, and P.

[0017] Figure 3 The image shows the XRD pattern of the Ti4O7-P electrode material.

[0018] In the figure: 1 DC power supply; 2 Ti4O7-P electrode; 3 titanium plate. Detailed Implementation

[0019] The specific embodiments of the present invention are described in detail below with reference to the technical solutions and accompanying drawings.

[0020] Example 1

[0021] Preparation method of Ti4O7-P electrocatalytic material:

[0022] Put 3 g of sodium hypophosphite monohydrate into a porcelain boat and place it on the upstream of the tube furnace, and place the Ti4O7 electrode on the downstream. Use the tube furnace to calcine under N2 protection, with a heating rate of 3°C / min, a reaction temperature of 350°C, and a reaction time of 2 h. After the reaction is completed and the electrode is cooled to room temperature, wash it with deionized water and ethanol alternately for 2 times, and reduce it in 1 M (NH4)2SO4 solution for 5 min. The reduction reaction device is shown in Figure 1 , to obtain the P-modified Ti4O7 electrode Ti4O7-P3-3.

[0023] TEM element mapping (‌ Figure 2 ) shows that P, Ti, and O elements are uniformly distributed in the material, indicating that P has been successfully doped into the Ti4O7 lattice. The XRD spectrum (‌ Figure 3 ) shows that all Ti4O7-Ps retain the same diffraction peaks (20.76°, 29.57°, 31.74°) as Ti4O7, which match the standard card (PDF #50-0787). All Ti4O7-Ps have a new characteristic peak at 2θ = 22.84°, and the diffraction peak intensity at 29.57° is significantly enhanced, indicating that the original Ti4O7 surface layer is etched and peeled off during the PH3 etching process, and a new Ti4O7 crystal phase is generated. In addition, the diffraction peak at 53.31° slightly shifts to a high angle after P doping, indicating that the introduction of P causes local distortion of the Ti4O7 lattice.

[0024] Using the above method, a series of Ti4O7-P materials (named Ti4O7-P3-1, Ti4O7-P3-2, Ti4O7-P3-5, Ti4O7-P3-10) were prepared at different heating rates of 1, 2, 5, and 10°C / min for subsequent performance comparison tests.

[0025] In addition, using the above method, a series of Ti4O7-P materials (named Ti4O7-P1-3, Ti4O7-P2-3, Ti4O7-P5-3, Ti4O7-P7-3) were prepared by selecting different sodium hypophosphite monohydrate dosages of 1, 2, 5, and 7 g for subsequent performance comparison tests.

[0026] Example 2

[0027] Electrocatalytic activation of CO3 2- Degradation of sulfamethoxazole: 3 mM Na2CO3 was weighed and dispersed into an electrocatalytic reactor containing 50 mL of sulfamethoxazole (20 mg / L SMX). A series of Ti4O7-P material electrodes were used as anodes, and Ti plates were used as cathodes, with a current density of 5 mA / cm 2, electrolyte is 30 mM Na2SO4, reaction time is 30 min. Take the reaction liquid once every 10 min, take 1 mL of the removed reaction liquid after filtering with a 0.22 μm filter membrane, and obtain the degradation rate after instrument testing. After 30 min of reaction, take 15 mL of the reaction liquid, filter with a 0.22 μm filter membrane, and test the TOC removal rate of the degradation process.

[0028] The SMX concentration is determined by ultra-high performance liquid chromatography, and the test results show that, after 30 min of reaction, the addition of CO3 2- The degradation rates of the series of Ti4O7-P materials on SMX can all reach more than 99%, compared with the pure Ti4O7 electrode which can only achieve a SMX degradation rate of 15%. The comparison of the mineralization rate performance of SMX shows that Ti4O7-P3-3 can achieve a mineralization rate of 65% at 30 min of reaction, which is better than other materials in the series (mineralization rate 30%-47%). Ti4O7-P3-3 can completely degrade SMX in the solution (removal rate 99.9%) at 20 min of reaction, and its degradation performance is better than other materials in the series, so it is used as the material for subsequent performance comparison tests.

[0029] Example 3

[0030] Electrocatalytic activation of CO3 2- Degradation of different pollutants test: as in Example 2, replace SMX with the same concentration of electron-rich pollutants: ciprofloxacin (CIP), diclofenac (DCF), minocycline (MINO), and electron-deficient pollutants: carbamazepine (CBZ), amoxicillin (IBF). By ultra-high performance liquid chromatography, the degradation rates of the electron-rich pollutants CIP, DCF, MINO can all reach more than 99%, and the degradation rates of the electron-deficient pollutants CBZ, IBF are 89.1% and 95.1% respectively, indicating that the P-doped Ti4O7 electrocatalytic activation of CO3 2- system has high applicability to electron-rich pollutants.

[0031] Example 4

[0032] Ion and natural organic matter influence test of electrocatalytic degradation performance: use cations: potassium ion (KNO3), calcium ion (Ca(NO3)2), magnesium ion (Mg(NO3)2); use anions: nitrate ion (KNO3), chloride ion (NaCl); natural organic matter (humic acid) are added to the electrocatalytic reactor containing 50 mL of SMX solution (20 mg / L) at a concentration of 3 mM CO3 2- The Ti4O7-P electrode is used as the anode, and the Ti plate is used as the cathode, and the current density is 5 mA / cm 2, electrolyte was 30 mM Na2SO4, reaction time was 30 min. The reaction solution was taken once every 10 min, and 1 mL of the taken reaction solution was filtered with a 0.22 μm filter membrane before instrument testing to obtain the degradation rate. By comparing the SMX degradation efficiency without adding anions and cations, the influence of anions and cations and natural organic matter on the degradation efficiency was proved.

[0033] The test results show that after the addition of potassium ions and nitrate ions, the degradation efficiency of SMX does not change significantly, and a high content of calcium ions, magnesium ions and chloride ions can inhibit the degradation of SMX. Cl ions can compete with CO3 2- , and calcium and magnesium ions can form precipitates with CO3 2- to inhibit their participation in the degradation reaction. The addition of natural organic matter can also affect the degradation of SMX, which may be caused by the competitive reaction between natural organic matter and SMX in the degradation process.

[0034] Example 5

[0035] Application test of the Ti4O7-P electrode in actual wastewater: SMX solutions (20 mg / L) were prepared with seawater, tap water and influent of a domestic sewage treatment station, respectively. 3 mM CO3 2- was added to an electro-catalytic reactor containing 50 mL of the SMX solution (20 mg / L). The Ti4O7-P3-3 electrode was used as the anode, and a Ti plate was used as the cathode, the current density was 5 mA / cm 2 , the electrolyte was 30 mM Na2SO4, and the reaction time was 30 min. The reaction solution was taken once every 10 min, and 1 mL of the taken reaction solution was filtered with a 0.22 μm filter membrane before instrument testing to obtain the degradation rate. By comparing the SMX degradation efficiency prepared with pure water, the influence of actual wastewater on the degradation efficiency was proved.

[0036] In addition, 3 mM CO3 2- was added to an electro-catalytic reactor containing 50 mL of actual pharmaceutical wastewater (initial COD was 1500 mg / L). The P-doped Ti4O7 electrode was used as the anode, and a Ti plate was used as the cathode, the current density was 10 mA / cm 2 , the electrolyte was 30 mM Na2SO4, and the reaction time was 30 min. After 30 min of reaction, 15 mL of the reaction solution was taken, filtered with a 0.22 μm filter membrane, and the changes of COD and BOD in the degradation process were tested.

[0037] The results showed that the degradation rate of SMX was improved in seawater and tap water, but decreased in the influent of sewage treatment plant. The competition between COD and SMX in the influent may limit the interaction between activated oxygen species and SMX. Although the degradation efficiency decreased, the activation of CO3 2- by Ti4O7-P3-3 still played a role in the influent of sewage treatment plant. The COD of pharmaceutical wastewater decreased by 63.6%, and the BOD / COD value increased by 40.3%, indicating that the system could improve the biodegradability of wastewater in a short time.

Claims

1. A method for preparing a phosphorus-doped electrode inducing strain in a Ti4O7 lattice, characterized by, The steps are as follows: The electrode plate with Ti4O7 film layer on the surface and sodium hypophosphite monohydrate are respectively placed in two porcelain boats, and then the two porcelain boats are placed in the middle of the tube furnace, and the sodium hypophosphite monohydrate is placed on the windward of the tube furnace, and the distance between the electrode plate and the sodium hypophosphite monohydrate is 4-6 cm; under the nitrogen atmosphere, the heating rate is 0.5-5 ℃ / min, the reaction temperature is 250-400 ℃, the reaction time is 1-4 h, and after the calcination is completed, it is naturally cooled to room temperature; after the electrode plate is taken out, it is placed in an electrochemical reduction reaction device, as a cathode, a lead oxide electrode as an anode, an ammonium fluoride solution as an electrolyte, and a current of 5 mA / cm 2 The constant current mode is operated for 2 min to obtain a Ti4O7 lattice strain electrode.

2. The electrode production method according to claim 1, wherein The thickness of the Ti4O7 film layer is 50-100 μm.

3. The electrode production method according to claim 1, wherein The ratio of the area of the electrode plate to the sodium hypophosphite dosage is 0.1-1.0 g sodium hypophosphite per square centimeter of electrode.

4. The electrode production method according to claim 1, wherein The ammonium fluoride solution is a mixture of ethylene glycol, ammonium fluoride and water with a mass ratio of 90:2:

8.

5. The application of the Ti4O7 lattice-strained electrode prepared by the method of any one of claims 1-4 in the electro-catalytic reinforcement of advanced purification of medical wastewater, characterized in that, The steps are as follows: The electrochemical degradation system was constructed with Ti4O7 lattice strain electrode as anode and Ti plate as cathode; under 1-20 mA / cm 2 Under constant current condition, the reaction temperature was 24-26℃, the SMX wastewater with concentration of 5-40 mg / L was used as target, the CO3 2- The SMX degradation rate could reach more than 99% under the conditions of 1-10 mM CO3

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