A method for preparing Cu@C composite materials for in-situ Fenton oxidation system and their application

Abstract

This invention discloses a method for preparing Cu@C composite materials for in-situ Fenton oxidation systems and their applications, belonging to the field of inorganic non-metallic materials technology. The method involves placing copper acetate monohydrate in a high-temperature tube furnace, purging the furnace with inert gas, then raising the furnace temperature to 300–450°C at a rate of 4–10°C / min in an inert atmosphere, followed by raising it to above 550°C at a rate of 1–4°C / min, holding the temperature at this point for 0.5–2 hours, and finally cooling it to room temperature to obtain a Cu@C composite material with a "core-shell" structure. This invention utilizes the direct high-temperature pyrolysis of copper acetate monohydrate in an inert atmosphere to obtain a "core-shell" structured Cu@C composite material. Copper acetate plays a dual role as both a Cu and C source, avoiding the disadvantages of the H2 reduction method, such as easy explosion, high cost, and difficulty in large-scale production. This method is simple, safe and controllable, low-cost, green and pollution-free, and can be produced on a large scale. The prepared Cu@C composite material has a large specific surface area, high catalytic activity, and good cycle stability, and can be applied to in-situ H2O2 production and in-situ Fenton catalysis.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic materials technology, specifically, it relates to a method for preparing Cu@C composite materials for in-situ Fenton oxidation system and their application. Background Technology

[0002] With the rapid development of human society, an increasing amount of organic matter is being used to serve humanity (WaterRes. 2021, 203, 117513). The untreated discharge of organic pollutants into natural water bodies threatens human health and the environment. In recent years, the research and development of organic pollutant water treatment technologies have received widespread attention. Among them, Fenton oxidation technology is one of the most widely used technologies to solve this problem (Chem.Eng.J. 2019, 376, 115672). However, Fenton technology suffers from problems such as low iron recycling efficiency, low hydrogen peroxide (H2O2) utilization rate, and high risks associated with H2O2 transportation and storage, which limit the application of the Fenton system (J.Hazard.Mater. 2010, 181, 343-350). Therefore, developing novel catalysts to reduce oxygen in situ to generate H2O2, and efficiently utilizing the in-situ generated H2O2 to remove organic pollutants (in-situ Fenton system), is a highly promising strategy for sustainable future development.

[0003] In recent years, reported methods for in-situ Fenton degradation of organic pollutants mainly include electro-Fenton, photo-Fenton, and chemical reaction methods (https: / / doi.org / 10.1016 / j.gee.2023.01.003). The electro-Fenton method is energy-intensive and costly; the photo-Fenton method requires light radiation, and photogenerated electrons are prone to recombination. Furthermore, the operating conditions for the in-situ H2O2 generation process of the above two methods are harsh, limiting their large-scale application. Conversely, some zero-valent metals and metal composites require no additional energy consumption, are low-cost, and have simple in-situ H2O2 generation processes, making them easy to apply on a large scale. This is considered a highly promising strategy for in-situ H2O2 generation. Zero-valent metals (Al...) 0 Fe 0 Cu 0 Zn 0 The in-situ generation of H2O2 (reducing O2 to H2O2) and the degradation of pollutants (catalytic generation of ·OH from H2O2) by Al and metal complexes in acidic systems have been reported (J. Hazard Mater. 2014, 275, 193-199). However, due to Al 0 Fe 0 Zn 0Metals and metal complexes (ZVs) possess strong reduction potentials, especially under acidic conditions. They can be directly consumed by free protons to generate H₂, leading to metal inactivity and inhibiting in-situ H₂O₂ formation, thus limiting their use at low pH levels (Environ. Sci. Technol. 2014, 48, 3354-3362). However, low pH is essential for H₂O₂ production (Environ. Sci. Technol. 2008, 42, 1262-1267). Therefore, it is necessary to find other metals to overcome the drawbacks of ZVs. The standard reduction potential of copper is 0.34 V (Cu). 2+ This ( / Cu) will prevent protons from generating H2 through the substitution reaction, giving it a higher persistent oxidation capacity (J. Hazard. Mater. 2014, 275, 193-199). Therefore, zero-valent copper can be an ideal substitute for ZV.

[0004] Previous studies have shown that nanoscale zero-valent copper can effectively degrade azo dyes by generating H2O2 in situ under acidic pH and aerobic conditions (Water Res. 2014, 66, 22-30; J. Hazard. Mater. 2014, 275, 193-199). Due to its high specific surface area and high reactivity, the synthesis of nanoscale zero-valent copper has attracted widespread attention. Its synthesis methods mainly include the NaBH4-reduction method and the sol-gel method (Chem. Eng. J. 2012, 203, 95-100; Water Res. 2014, 66, 22-30). These methods require the addition of additional chemical reagents and generate wastewater that pollutes the environment. Furthermore, nanoscale copper particles tend to aggregate during the reaction, which reduces their overall reactivity and results in poor recyclability, limited to no more than three times. Therefore, researchers have adopted a strategy of adding stabilizers to improve the dispersion stability of copper nanoparticles. For example, carboxylic acids, polyvinyl alcohol, oleylamine, and polyaminoamine dendrimers have been used as stabilizers to disperse copper nanoparticles (Mater. Lett. 2007, 61, 4711-4714; J. Am. Chem. Soc. 1998, 120, 7355-7356; Mater. Lett. 2010, 64, 45-48). However, these stabilizers are all organic chemicals, which not only interfere with the activation of oxygen by zero-valent copper to produce reactive oxygen species, but also cause secondary pollution (Chemosphere, 2017, 180, 335-342).

[0005] A search of existing technologies both domestically and internationally has revealed no one who has proposed using copper acetate to directly decompose at high temperatures in an inert atmosphere to obtain a Cu@C composite catalyst with a "core-shell" structure that exhibits good dispersibility, high catalytic activity, and good cycle stability. Summary of the Invention

[0006] To address the various shortcomings of existing in-situ Fenton systems induced by chemical reactions, this invention aims to provide a method for synthesizing and applying in-situ Fenton catalysts with large specific surface area, high catalytic activity, and good cycle stability.

[0007] Therefore, the first objective of this invention is to address some problems existing in the prior art by providing a method for preparing Cu@C composite materials for in-situ Fenton oxidation systems. Another objective of this invention is to utilize Cu@C composite materials as in-situ Fenton catalysts for the removal of organic pollutants.

[0008] To achieve the above-mentioned technical objectives, the inventors conducted extensive experimental research and tireless exploration, and finally obtained the following technical solution: a method for preparing Cu@C composite materials for in-situ Fenton oxidation systems, the specific steps of which are as follows:

[0009] (1) Weigh a certain amount of copper salt into a porcelain boat, place it in a high-temperature tube furnace, and use inert gas to remove the air from the high-temperature tube furnace.

[0010] (2) In an inert atmosphere, the high-temperature tube furnace is heated to above 300-450°C at a rate of 4-10°C / min, and then heated to above 550°C at a rate of 1-4°C / min. The temperature is held for 0.5-2 hours and then cooled to room temperature to obtain Cu@C composite material with a "core-shell" structure.

[0011] More preferably, in the preparation method of Cu@C composite material for in-situ Fenton oxidation system as described above, the mass of the copper salt in step (1) is 2-4g.

[0012] More preferably, in the preparation method of Cu@C composite material for in-situ Fenton oxidation system as described above, the copper salt in step (1) is copper acetate monohydrate.

[0013] More preferably, in the preparation method of Cu@C composite material for in-situ Fenton oxidation system as described above, the inert gas in step (1) is argon or nitrogen.

[0014] More preferably, in the preparation method of Cu@C composite material for in-situ Fenton oxidation system as described above, the flow rate of the inert gas in step (2) is 20-50 mL / min.

[0015] More preferably, in the preparation method of Cu@C composite material for in-situ Fenton oxidation system as described above, the temperature is increased to 350-450°C at a rate of 5-8°C / min in step (2).

[0016] More preferably, in the preparation method of Cu@C composite material for in-situ Fenton oxidation system as described above, the temperature in step (2) is increased to 500-1000℃ at a rate of 1-4℃ / min.

[0017] More preferably, in the preparation method of Cu@C composite material for in-situ Fenton oxidation system as described above, the heat preservation time in step (2) is 1 to 1.5 h.

[0018] Furthermore, using organic dyes as the target pollutant, the inventors conducted simulation experiments to study the catalytic performance of the self-generating H2O2 "core-shell" structured Cu@C composite material prepared by the above method for organic pollutants. The results showed that the "core-shell" structured Cu@C composite material prepared by this invention exhibits good catalytic performance against organic dyes in wastewater, and therefore can be used for the treatment of organic dye wastewater. That is, the technical solution of this invention also includes the application of the "core-shell" structured Cu@C composite material prepared by the above method in the treatment of organic dye wastewater. Further preferably, the organic dyes include methyl orange, methylene blue, rhodamine B, neutral red, and orange-yellow II.

[0019] Compared with the prior art, the in-situ Fenton catalyst preparation method of the present invention has the following advantages and advancements:

[0020] (1) The method of the present invention selects raw materials and uses copper acetate monohydrate to directly decompose at high temperature in an inert atmosphere to obtain Cu@C composite material with a "core-shell" structure. Copper acetate plays a dual role as both a Cu and C source, avoiding the disadvantages of H2 reduction method such as easy explosion, high cost, and difficulty in large-scale production. The Cu@C composite material obtained by this method can be applied to the fields of in-situ H2O2 production and in-situ Fenton catalysis. Methyl orange organic dye (20 mg / L) can be completely degraded within 10 min.

[0021] (2) The Cu@C core-shell structure material obtained by the method of the present invention has a large specific surface area, high catalytic activity and good recyclability. After being recycled 10 times, the removal rate of organic dyes still reaches more than 95%.

[0022] (3) The shell C of the Cu@C “core-shell” structure material obtained by the method of the present invention not only inhibits the consumption of nano Cu and the agglomeration of nano Cu during the reaction process, but also accelerates the generation of H2O2 and improves the utilization rate of H2O2; under the synergistic effect of Cu and C, the catalytic activity and catalytic cycle stability are improved.

[0023] (4) The preparation steps of this invention are simple, the process is safe and controllable, the cost is low, it is green and free of pollutants, and it can be produced on a large scale. Attached Figure Description

[0024] Figure 1 The image shows the XRD pattern of the Cu@C composite material in Example 1 of this invention.

[0025] Figure 2 The image shows the Raman spectrum of the Cu@C composite material in Example 1 of this invention.

[0026] Figure 3 This is a TEM image of the Cu@C composite material in Example 1 of the present invention;

[0027] Figure 4 Nitrogen adsorption diagram of Cu@C composite material in Example 1 of this invention.

[0028] Figure 5 This is a graph showing the effect of Cu and Cu@C composite materials on the degradation rate of methyl orange in Example 1 of the present invention;

[0029] Figure 6 The catalytic cycle life of the Cu@C composite material for the degradation of methyl orange in Example 1 of this invention;

[0030] Figure 7 The image shows the XRD pattern of the Cu@C composite material in Example 2 of this invention.

[0031] Figure 8 The image shows the Raman spectrum of the Cu@C composite material in Example 2 of this invention.

[0032] Figure 9 The image shows the XRD pattern of the Cu@C composite material in Example 3 of this invention.

[0033] Figure 10 This is the Raman spectrum of the Cu@C composite material in Example 3 of the present invention. Detailed Implementation

[0034] The present invention will be further described in detail below through specific embodiments. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of protection of the present invention. Furthermore, unless specific technical operation steps or conditions are specified in the embodiments, they are all performed according to the general techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0035] Example 1

[0036] 2g of copper acetate was weighed into a ceramic boat, which was then placed in a tube furnace. Argon gas was passed through the furnace to purge the air from the high-temperature tube furnace for 1 hour. The furnace was then heated to 450°C at a rate of 5°C / min, and then to 600°C at a rate of 2°C / min. The temperature was held for 2 hours and then cooled to room temperature to obtain a Cu@C composite material with a "core-shell" structure.

[0037] The composition, microstructure and properties of the Cu@C material prepared in Example 1 were analyzed and characterized by XRD, Raman, TEM, EDS and physical adsorption analysis.

[0038] (1) Phase composition and microstructure analysis (XRD, Raman, TEM and physical adsorption)

[0039] Figure 1 The X-ray powder diffraction pattern of the Cu@C "core-shell" composite material prepared in Example 1 of this invention shows that the obtained Cu@C sample exhibited four diffraction peaks at 2θ = 43.4°, 50.6°, 74.2°, and 90.1°, which are consistent with the characteristic diffraction peaks of elemental copper. The Raman spectrum of the Cu@C composite material (…) Figure 2 It can be seen that at 1350cm -1 and 1580cm -1 The characteristic Raman peaks of amorphous carbon, D band and G band, appeared at the locations respectively.

[0040] Figure 3 The image shows a TEM image of the Cu@C core-shell composite material prepared in Example 1 of this invention. The image shows that amorphous carbon is coated on the surface of nano-carbon to form a core-shell structure. The C shell layer has a uniform thickness with an average thickness of 15 nm.

[0041] Figure 4 The nitrogen adsorption diagram is shown for the Cu@C core-shell composite material prepared in Example 1 of this invention, with a specific surface area of ​​28 cm². 2 / g, relative to nano copper (0.76cm 2 The amount of elemental substance ( / g) increased by 36.8 times.

[0042] In summary, this invention successfully prepared a Cu@C composite material with a core-shell structure and a large specific surface area.

[0043] (2) Oxidation catalysis experiment

[0044] Prepare 50 mL of a 20 mg / L methyl orange solution with pH 3.2. Add 20 mg of the Cu@C composite material prepared in the above method to the methyl orange solution, and stir the reaction at room temperature (25°C). Take samples at intervals, and measure the absorbance at the maximum absorption wavelength using a UV-Vis spectrophotometer to calculate the degradation rate. Figure 5 As shown in Figure a, the in-situ H2O2 production of Cu and Cu@C composite materials gradually increased with the extension of reaction time. Within 10 min, the H2O2 production of nano-Cu and Cu@C composite materials were 1.04 and 2.91 μL / mg, respectively, while the degradation rates of methyl orange were 8.4% and 100%, respectively. Figure 5(b) This shows that the catalytic activity of Cu@C is 12 times higher than that of nano-Cu, indicating that the synergistic effect of nano-Cu and shell C accelerates the in-situ generation of H2O2 and improves the utilization rate of H2O2, thus exhibiting better catalytic performance. After 10 cycles, the oxidation degradation rate of methyl orange by Cu@C can still reach over 95.0%, reflecting that the synthesized Cu@C catalyst has a good catalytic cycle life. Figure 6 ).

[0045] Example 2

[0046] 3g of copper acetate was weighed into a ceramic boat, which was then placed in a tube furnace. Argon gas was passed through the furnace to purge the air from the high-temperature tube furnace for 1 hour. The furnace was then heated to 400°C at 7°C / min, and then to 700°C at 1.5°C / min. The temperature was held for 1.5 hours and then cooled to room temperature to obtain a Cu@C composite material with a "core-shell" structure.

[0047] XRD was performed on the product. Figure 7 Raman Figure 8 TEM and physical adsorption analysis characterization showed that the "core-shell" structured Cu@C composite material was successfully prepared.

[0048] Prepare 50 mL of a 20 mg / L methyl orange solution with pH 3.6. Add 20 mg of the Cu@C composite material prepared by the above method to the methyl orange solution, and stir the reaction at room temperature (25 °C). The methyl orange degradation rate reaches 100% within 10 min.

[0049] Example 3

[0050] 4g of copper acetate was weighed into a ceramic boat, which was then placed in a tube furnace. Argon gas was passed through the furnace to purge the air from the high-temperature tube furnace for 1 hour. The furnace was then heated to 350°C at 8°C / min, and then to 900°C at 2°C / min. The temperature was held for 1 hour and then cooled to room temperature to obtain a Cu@C composite material with a "core-shell" structure.

[0051] XRD was performed on the product. Figure 9 Raman Figure 10 TEM and physical adsorption analysis characterization showed that the "core-shell" structured Cu@C composite material was successfully prepared.

[0052] Prepare 50 mL of a 20 mg / L methyl orange solution with pH = 4. Add 20 mg of the Cu@C composite material prepared by the above method to the methyl orange solution, and stir the reaction at room temperature (25 °C). The methyl orange degradation rate reaches 100% within 10 min.

Claims

1. The application of a Cu@C composite material in the in-situ Fenton oxidation treatment of organic dye wastewater, wherein the preparation method of the Cu@C composite material includes the following steps: (1) Weigh a certain amount of copper salt into a porcelain boat, place it in a high-temperature tube furnace, and use inert gas to remove the air from the high-temperature tube furnace. (2) After step (1) is completed, the high temperature tube furnace is heated to 300-450℃ at a rate of 4~10℃ / min in an inert atmosphere, then heated to 550~600℃ at a rate of 1~4℃ / min, held at the temperature for 0.5~2 h, and cooled to room temperature to obtain Cu@C composite material with "core-shell" structure. The copper salt mentioned in step (1) is copper acetate monohydrate.

2. The application according to claim 1, characterized in that, The mass of the copper salt mentioned in step (1) is 2~4 g.

3. The application according to claim 1, characterized in that, The inert gas mentioned in step (1) is argon and / or nitrogen.

4. The application according to claim 1, characterized in that, The flow rate of the inert gas in step (2) is 20~50 mL / min.

5. The application according to claim 1, characterized in that, In step (2), the temperature is increased to 350-450 ℃ at a rate of 5-8 ℃ / min.

6. The application according to claim 1, characterized in that, The heat preservation time mentioned in step (2) is 1~1.5 h.

7. The application according to claim 1, characterized in that, The organic dyes mentioned include methyl orange, methylene blue, rhodamine B, neutral red, and orange yellow II.

Images