A method for removing pollutants in water by using local thermal effect to promote fenton-like reaction

Abstract

The application provides a method for removing pollutants in water by utilizing a local thermal effect to promote a Fenton-like reaction, and uses a ruthenium-doped titanium dioxide nanobelt (TNB-Ru) as a catalyst; the TNB-Ru is prepared by using commercial anatase titanium dioxide nanoparticles as raw materials, first, a hydroxylated titanium dioxide nanobelt is prepared by using an alkaline hydrothermal method, then the titanium dioxide nanobelt is dispersed in a ruthenium chloride ethanol solution, and the ruthenium is loaded on the titanium dioxide nanobelt by using the anchoring effect of the surface hydroxyl group, and finally the target material is obtained. The TNB-Ru prepared by the method has excellent catalytic degradation performance, which is mainly due to the fact that the ruthenium dispersed on the titanium dioxide nanobelt generates a local plasmonic resonance effect to form a local high-temperature environment under visible light irradiation, and the Fenton-like reaction is accelerated.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and particularly relates to a method for removing pollutants from water by enhancing a Fenton-like reaction using localized thermal effects. Background Technology

[0002] Heterogeneous Fenton reactions are widely used in various fields due to their environmental friendliness and excellent pollutant removal performance. However, commonly used oxidants such as hydrogen peroxide are relatively difficult to activate due to the symmetrical structure of the peroxy bond. Therefore, it is essential to find a method to promote the activation of hydrogen peroxide. High reaction temperatures have been proven to help overcome the activation barrier. Utilizing the photothermal conversion effect of materials can effectively initiate and control chemical reactions, with many interesting applications in photothermal therapy, photocatalysis, micro-pollutant degradation, and CO2 reduction. In traditional photothermal conversion, light is absorbed on the catalyst surface and converted into heat. This surface heat diffuses into the solution, resulting in most of the heat on the catalyst surface being dissipated in the bulk solution rather than forming localized high temperatures. Furthermore, water has a high specific heat capacity, limiting the overall temperature rise of the solution and leading to unsatisfactory chemical reaction performance. Therefore, constructing a localized high-temperature environment to promote Fenton-like reactions is of great significance. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for removing organic pollutants from water by utilizing local thermal effects to promote Fenton-like reactions.

[0004] To solve the technical problem, the present invention adopts the following technical solution:

[0005] A method for removing pollutants from water by promoting a Fenton-like reaction using localized thermal effects includes: adding an appropriate amount of ruthenium-doped titanium dioxide nanoribbon catalyst and hydrogen peroxide to polluted water, mixing thoroughly, and then irradiating with visible light. The metallic ruthenium undergoes plasmon resonance, forming a localized thermal environment, which promotes the activation of hydrogen peroxide to generate free radicals for the oxidation and removal of pollutants from the water.

[0006] Preferably, the dosage of the ruthenium-doped titanium dioxide nanoribbons in the polluted water is 0.1–0.3 g / L.

[0007] Preferably, the concentration of hydrogen peroxide added to the polluted water body is 2-10 mM.

[0008] Preferably, the concentration of pollutants in the polluted water body is 5–20 mg / L.

[0009] The preparation method of ruthenium-doped titanium dioxide nanoribbons according to the present invention is as follows: First, surface-hydroxylated titanium dioxide nanoribbons are prepared by alkaline hydrothermal method, and then they are dispersed in ruthenium trichloride ethanol solution. The anchoring effect of the surface hydroxyl groups is used to load ruthenium onto the titanium dioxide nanoribbons, thereby obtaining the target material. Specifically, it includes: dispersing commercial anatase titanium dioxide nanoparticles in KOH solution and carrying out a hydrothermal reaction to obtain surface-hydroxylated titanium dioxide nanoribbons; dispersing the surface-hydroxylated titanium dioxide nanoribbons in ruthenium trichloride ethanol solution and shaking at room temperature; impregnating the obtained product in ascorbic acid solution to obtain ruthenium-doped titanium dioxide nanoribbons as a Fenton-like catalyst.

[0010] Preferably, in the above method for preparing ruthenium-doped titanium dioxide nanoribbons, the molar ratio of ruthenium trichloride to surface-hydroxylated titanium dioxide nanoribbons is 1:10 to 20.

[0011] Preferably, in the above method for preparing ruthenium-doped titanium dioxide nanoribbons: the oscillation speed is 180-230 r / min and the time is 12-18 h.

[0012] Preferably, in the above method for preparing ruthenium-doped titanium dioxide nanoribbons: the concentration of the ascorbic acid solution is 0.8–1.2 M, and the impregnation time is 0.5–1 h. After impregnation, the nanoribbons are washed and dried to obtain the target product at a drying temperature of 50–70 °C.

[0013] The beneficial effects of this invention are reflected in:

[0014] 1. This invention uses commercial anatase titanium dioxide nanoparticles as raw materials. First, surface-hydroxylated titanium dioxide nanoribbons are prepared using an alkaline hydrothermal method. Then, these nanoribbons are dispersed in a ruthenium chloride ethanol solution. The anchoring effect of the surface hydroxyl groups is used to load ruthenium onto the titanium dioxide nanoribbons, ultimately yielding the target material, ruthenium-doped titanium dioxide nanoribbons (TNB-Ru). The titanium dioxide nanoribbons obtained after alkaline treatment and hydrothermal reaction have a large number of hydroxyl groups on their surface and a larger specific surface area, allowing for better loading of ruthenium.

[0015] 2. The TNB-Ru prepared by the method provided in this invention exhibits excellent performance. Under visible light radiation, its degradation rate of Rhodamine B is increased by orders of magnitude compared to the undoped form. Ultraviolet-visible diffuse reflectance spectroscopy (DRS), infrared thermography, and finite-difference time-domain simulation (FDTD) demonstrate that the superior degradation performance is mainly attributed to the localized plasmon resonance (LSPR) effect generated by ruthenium dispersed on titanium dioxide nanoribbons under visible light irradiation, creating a localized high-temperature environment that accelerates the Fenton-like reaction. Specifically, under visible light irradiation, when the incident light frequency matches the oscillation frequency of free electrons in metallic ruthenium, plasmon resonance occurs. The absorbed photon energy induces electrons in the metal to transfer from the ground state to a higher energy state, forming hot carriers. These carriers undergo non-radiative attenuation through electron-photon, electron-electron, or electron-phonon coupling, generating a localized thermal effect that promotes the activation of hydrogen peroxide at active sites, forming free radicals that degrade pollutants. The TNB-Ru prepared by this invention has a stable structure and can maintain good pollutant removal performance for a long time.

[0016] 3. The preparation method of TNB-Ru of this invention requires low raw material costs and is simple to prepare, and has the potential for practical application, providing a new approach for the preparation of more efficient photocatalysts. Attached Figure Description

[0017] Figure 1 (a) is a high-resolution transmission electron microscope image of TNB-Ru prepared in Example 1. Figure 1 (b) is a high-angle annular dark-field scanning transmission electron microscope image of TNB-Ru with double spherical aberration.

[0018] Figure 2 XRD diffraction images of TNB-Ru and undoped TNB prepared in Example 1.

[0019] Figure 3 The UV-Vis diffuse reflectance spectra of TNB-Ru prepared in Example 1 and TNB without ruthenium doping.

[0020] Figure 4 The photothermal conversion effect of TNB-Ru and TNB in ​​Example 2 is shown, wherein... Figure 4 (a) shows the temperature change of the material over time under illumination. Figure 4 (b) is the temperature change curve of the beaker system with dispersed material after light exposure over time.

[0021] Figure 5 (a) is a graph showing the degradation amount-time of RhB removal by activated hydrogen peroxide in TNB-Ru and undoped TNB in ​​Example 3; Figure 5 (b) is a fitting graph of the rate constant for the catalytic degradation of pollutants by the material.

[0022] Figure 6 This is a diagram showing the reactive oxygen species generated by TNB-Ru and TNB-activated hydrogen peroxide in Example 4. Figure 6 (a) shows the EPR test results for hydroxyl radicals (·OH). Figure 6 (b) is singlet oxygen ( 1 EPR test results for O2), Figure 6 (c) represents superoxide radicals (·O2). - The EPR test results of ).

[0023] Figure 7 This is a repeatability characterization diagram of TNB-Ru prepared in Example 1 of the present invention.

[0024] Figure 8 This is a stability characterization diagram of TNB-Ru prepared in Example 1 of the present invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other instances that are improved or modified by those skilled in the art are within the scope of protection of the present invention. It should be understood that the embodiments of the present invention are only used to illustrate the technical effects of the present invention, and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the methods used in the embodiments are conventional methods.

[0026] This invention provides a method for removing pollutants from water by promoting a Fenton-like reaction using localized thermal effects, comprising: adding an appropriate amount of ruthenium-doped titanium dioxide nanoribbon catalyst (TNB-Ru) and hydrogen peroxide (H2O2) to the pollutants, mixing thoroughly, and then irradiating under a xenon lamp, wherein the target pollutants in the water are oxidized and removed by reactive oxygen species generated by the activation of hydrogen peroxide.

[0027] In the reaction system: the catalyst dosage is preferably 0.1–0.3 g / L, and the H₂O₂ concentration is preferably 2–10 mM. Ruthenium-doped titanium dioxide nanoribbons (TNB-Ru), hydrogen peroxide, and a solution containing contaminants are mixed. The concentration of contaminants in the solution is preferably 5–20 mg / L. Unless otherwise specified, pH control is not required before the reaction in this invention. The initial reaction temperature is preferably 15°C–30°C, and the reaction time is preferably 30–60 min. The reaction is preferably carried out under magnetic stirring, with a stirring speed preferably 50–500 rpm.

[0028] This invention uses ruthenium-doped titanium dioxide nanoribbons as a catalyst for a Fenton-like reaction. Under visible light irradiation, metallic ruthenium undergoes plasmon resonance (LSPR), rapidly exciting hot electrons. The relaxation of these hot electrons creates a localized thermal environment, significantly promoting the activation of H2O2 by TNB-Ru to produce ·O2. - It can oxidize pollutants (RhB) in water, and has good stability, allowing for repeated use, which is of great significance for practical applications.

[0029] Example 1

[0030] Titanium dioxide nanoribbons (TNB) were prepared as follows: 0.5 g of commercial anatase titanium dioxide nanoparticles (30 nm in diameter) were added to 80 mL of a 10 M KOH solution and sonicated for 30 minutes to ensure uniform dispersion. The solution was then transferred to a 100 mL polytetrafluoroethylene autoclave, sealed, and placed in an oven for hydrothermal reaction at 180 °C for 24 h. After the reaction was completed and cooled to room temperature, the solution was removed, centrifuged, and washed several times with ethanol and deionized water, respectively. Finally, it was dried in a freeze dryer at -80 °C for 12 h to obtain titanium dioxide nanoribbons (TNB).

[0031] Ruthenium-doped titanium dioxide nanoribbons (TNB-Ru) were prepared as follows: A certain amount of hydrated ruthenium trichloride (RuCl3·xH2O, with a ruthenium content of 37-40%) was dispersed in 20 mL of anhydrous ethanol, so that Ru... 3+ The concentration of TNB was 12.5 mM, and it was gently sonicated to dissolve it completely. Then, 0.4 g of the TNB prepared above was added, and after sonication for 5 minutes, it was placed on a shaker and shaken for 14 h. After centrifugation, it was washed with deionized water and anhydrous ethanol, and then dispersed in 1 M ascorbic acid. After standing for 30 min, it was washed three times with deionized water and anhydrous ethanol. Finally, it was dried at 70 °C under vacuum for 12 h to obtain the target material TNB-Ru.

[0032] The TNB-Ru prepared in Example 1 of this invention was subjected to high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field scanning transmission electron microscopy (HADDF-STEM). The detection results are as follows: Figure 1 As shown. From Figure 1 As can be seen in (a), titanium dioxide, after treatment, becomes a thin nanoribbon structure with a length of 150–200 nm and a width of 10–20 nm. Figure 1 As can be seen in (b), the main form of metallic ruthenium on titanium dioxide is nanoclusters with a size of 1 to 2 nm.

[0033] XRD tests were performed on TNB-Ru and TNB prepared in Example 1, and the results are as follows: Figure 2As shown, there was no significant change after ruthenium doping, indicating that ruthenium did not form large particle structures.

[0034] The UV-Vis diffuse reflectance spectra of TNB-Ru and TNB prepared in Example 1 were measured, and the results are as follows: Figure 3 As shown, it can be seen that after loading ruthenium, the absorption of visible light by the material is significantly enhanced, and a plasmonic resonance absorption peak appears at 450 nm, which preliminarily proves that TNB-Ru can form a plasmonic resonance effect (LSPR) under visible light irradiation.

[0035] Example 2

[0036] The photothermal conversion effect of the materials was detected using an infrared thermal imager. 50 mg of the TNB-Ru and TNB materials prepared in Example 1 were evenly spread on weighing paper, and a CUT420 (λ≥420 nm) xenon lamp light source was mounted on it for irradiation. The vertical distance between the xenon lamp filter and the material was maintained at 25–30 cm, and timing was started. The temperature of the material was recorded every 2 minutes using an infrared thermal imager. Additionally, 9 mg of TNB-Ru and TNB were dispersed in 60 mL of deionized water and placed under a xenon lamp light source equipped with the same filter for irradiation. The vertical distance between the liquid surface and the filter was maintained at 10–15 cm, and timing was started. The temperature of the entire system was recorded every 5 minutes using an infrared thermal imager.

[0037] Test results are as follows Figure 4 As shown. From Figure 4 As shown in (a), TNB-Ru's temperature rises rapidly to nearly 200°C after 2 minutes of light irradiation, while TNB's temperature change under visible light irradiation is not very significant, reaching only 75°C after 10 minutes of irradiation; from Figure 4 As can be seen from (b), the temperature of the system with TNB-Ru dispersion is higher than that of the system with TNB dispersion, indicating that TNB-Ru has better photothermal conversion efficiency.

[0038] Example 3

[0039] The TNB-Ru and TNB prepared in Example 1 were used as catalysts in the degradation experiment of the model pollutant (RhB): 9 mg of TNB-Ru prepared in Example 1 was added to 30 mL of RhB model pollutant, the concentration of which was 20 mg / L. Hydrogen peroxide (H2O2) was added as an oxidant, and the concentration of H2O2 in the model pollutant was 10 mM. The entire system was subjected to radiation from a xenon lamp light source equipped with a CUT420 (λ≥420 nm) and the radiation intensity was 1200 mW·cm. 2The timing was started, and after approximately 5 minutes, 1.5 mL of the reaction solution was collected, centrifuged to obtain the supernatant, and the concentration of the RhB model pollutants was detected using a UV-Vis spectrophotometer. The results were expressed as absorbance A. t This indicates that the above operation should be repeated, based on the degradation rate-time (A). t Plotting / A0-t) and processing the steepest part of the degradation curve to obtain the maximum degradation rate constant K of the material; simultaneously setting up degradation experiments under dark conditions, water bath degradation experiments, and TNB control group experiments, the experimental results are as follows. Figure 5 As shown, Figure 5 (a) is a graph showing the degradation amount-time of pollutants catalytically degraded by the material. Figure 5 (b) is a fitting graph of the rate constant for the catalytic degradation of pollutants by the material.

[0040] from Figure 5 (a) It can be seen that TNB has almost no degradation effect on pollutants under visible light irradiation; TNB-Ru degrades relatively slowly under dark conditions, and can only degrade about 5% of RhB in 30 minutes; heating in a 35℃ water bath has a certain promoting effect on degradation, but can only degrade about 30% of RhB in 30 minutes; under visible light irradiation, more than 90% of pollutants can be degraded. Figure 5 (b) The degradation rate constant also shows that TNB-Ru has the highest RhB degradation rate constant under light irradiation, which is approximately 0.135 min. -1 These values ​​are 1390 times, 98 times, and 18 times that of TNB under light conditions, TNB-Ru under dark conditions, and TNB-Ru under 35℃ water bath conditions, respectively. It can be seen that the local thermal effect formed by TNB-Ru under visible light irradiation has a significant promoting effect on the degradation of pollutants.

[0041] Example 4

[0042] Add 9 mg TNB-Ru to 30 mL of RhB contaminant, add 10 mM H2O2 dropwise to the system, and apply radiation from a xenon lamp light source equipped with a CUT420 (λ≥420 nm) at an intensity of 1200 mW·cm² to the entire system. 2 After reacting for 10 min, 10 μL of DMPO capture solution was added to a centrifuge tube, followed by 200 μL of the reaction solution filtered through a membrane. The generation of hydroxyl radicals (·OH) in the reaction solution was determined using electron paramagnetic resonance (EPR) spectroscopy. Then, 300 μL of TEMP capture solution was added to a centrifuge tube, followed by 700 μL of the reaction solution. The singlet oxygen (·OH) content in the reaction solution was determined using electron paramagnetic resonance (EPR) spectroscopy. 1 O2) generation; detection of superoxide radicals (·O2) in a methanol system. -To detect the signal, the specific procedure was as follows: 2 mg of TNB-Ru was dispersed in 10 mL of methanol solution, 5 μL of H2O2 and 50 μL of DMPO were added dropwise, and the entire system was irradiated with a xenon lamp source. After reacting for 10 min, samples were taken for detection. A control group experiment with TNB was also set up.

[0043] EPR test results are as follows Figure 6 .like Figure 6 As shown in (a), the signal of hydroxyl radicals in the reaction system is relatively weak; as shown in 6(b), under light irradiation, TNB-Ru hardly activates hydrogen peroxide to produce a stronger singlet oxygen signal, indicating that singlet oxygen does not significantly promote the degradation of RhB in the system; as shown in 6(c), the superoxide radical "sextet" signal of the reaction system is significantly enhanced, indicating that hydrogen peroxide is activated to produce more superoxide radicals.

[0044] Example 5

[0045] Good repeatability and stability are two important indicators for evaluating the practical application capability of catalysts. This example tests the repeatability and stability of the material TNB-Ru prepared in Example 1. (For repeatability testing, after the experiment, the catalyst was placed on a hydrophilic filter membrane for vacuum filtration and rinsed with a large amount of deionized water. Then, it was introduced into a new round of degradation experiments with new pollutants, with the volume of pollutants and the amount of H2O2 reduced proportionally. This process was repeated four times. For stability testing, the catalyst after the above cycle test was filtered, rinsed with a large amount of deionized water, dried in a 60℃ oven for 12 hours, and then subjected to XRD testing.) The results are as follows: Figure 7 and Figure 8 As shown. Figure 7 This is a repeatability characterization diagram of TNB-Ru prepared in Example 1 of the present invention. Figure 8 This is a stability characterization diagram of TNB-Ru prepared in Example 1 of the present invention.

[0046] from Figure 7 and Figure 8 It can be seen that after five consecutive degradation tests, the degradation effect of TNB-Ru hardly decreased, and its own structure did not change significantly.

[0047] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for removing pollutants from water by utilizing localized thermal effects to promote Fenton-like reactions, characterized in that: Adding an appropriate amount of ruthenium-doped titanium dioxide nanoribbon catalyst and hydrogen peroxide to polluted water, and then irradiating it with visible light after thorough mixing, causes plasmon resonance in the metallic ruthenium, forming a localized thermal environment that promotes the activation of hydrogen peroxide to generate free radicals for the oxidation and removal of pollutants from the water. The preparation method of the ruthenium-doped titanium dioxide nanoribbon is as follows: first, surface-hydroxylated titanium dioxide nanoribbons are prepared using an alkaline hydrothermal method, and then they are dispersed in an ethanol solution of ruthenium trichloride. The ruthenium is loaded onto the titanium dioxide nanoribbons by the anchoring effect of the surface hydroxyl groups, thereby obtaining ruthenium-doped titanium dioxide nanoribbons.

2. The method for removing pollutants from water by utilizing localized thermal effects to promote Fenton-like reactions according to claim 1, characterized in that, The dosage of the ruthenium-doped titanium dioxide nanoribbons in the polluted water is 0.1~0.3 g / L.

3. The method for removing pollutants from water by utilizing localized thermal effects to promote Fenton-like reactions according to claim 1, characterized in that, The concentration of hydrogen peroxide added to the polluted water body is 2~10 mM.

4. The method for removing pollutants from water by utilizing localized thermal effects to promote Fenton-like reactions according to claim 1, characterized in that, The method for preparing the ruthenium-doped titanium dioxide nanoribbons includes the following steps: Commercial anatase titanium dioxide nanoparticles were dispersed in KOH solution and subjected to a hydrothermal reaction to obtain surface-hydroxylated titanium dioxide nanoribbons. The surface-hydroxylated titanium dioxide nanoribbons were then dispersed in ruthenium trichloride ethanol solution and shaken at room temperature. The resulting product was impregnated in ascorbic acid solution to obtain ruthenium-doped titanium dioxide nanoribbons as a Fenton-like catalyst.

5. The method for removing pollutants from water by utilizing localized thermal effects to promote Fenton-like reactions according to claim 4, characterized in that, The molar ratio of ruthenium trichloride to surface-hydroxylated titanium dioxide nanoribbons is 1:10~20.

6. The method for removing pollutants from water by utilizing localized thermal effects to promote Fenton-like reactions according to claim 4, characterized in that, The oscillation speed is 180~230 r / min and the duration is 12~18 h.

7. The method for removing pollutants from water by utilizing localized thermal effects to promote Fenton-like reactions according to claim 4, characterized in that, The concentration of the ascorbic acid solution is 0.8~1.2 M, and the immersion time is 0.5~1 h.

Images