Application of difunctional microcapsule in formaldehyde degradation

Abstract

According to the application of the difunctional microcapsule in formaldehyde degradation, the difunctional microcapsule is of a core-shell structure, the core is a phase change material, and the shell is a polymer layer containing TiO2 nanoparticles. According to the technical scheme, the photo-generated carrier separation efficiency can be remarkably improved, the durability is enhanced, meanwhile, the inner core part of the microcapsule can further play an energy storage or heat management function, and the dual-function cooperation of photocatalysis and energy regulation and control is achieved.

Description

Technical Field

[0001] This application relates to the technical field of formaldehyde degradation, specifically to the application of a bifunctional microcapsule in formaldehyde degradation. Background Technology

[0002] Formaldehyde is an unavoidable pollutant in the home decoration process. Long-term excessive inhalation can cause varying degrees of harm to the human body, and it must be purified and eliminated.

[0003] Currently, indoor formaldehyde removal methods mainly include physical adsorption (activated carbon, zeolite), chemical oxidation (potassium permanganate, ozone, etc.), and photocatalytic decomposition. Among these, photocatalysis is considered the most promising method for adsorbing and degrading formaldehyde because it can completely oxidize formaldehyde to CO2 and H2O at room temperature and pressure. However, the traditional method of using TiO2 photocatalysts for formaldehyde degradation and elimination suffers from technical problems such as easy aggregation, weak visible light response, and poor reusability. Summary of the Invention

[0004] This application addresses the aforementioned shortcomings of the prior art by providing a bifunctional microcapsule that can significantly improve the separation efficiency of photogenerated carriers and enhance durability. At the same time, the core of the microcapsule can further play the role of energy storage or thermal management, realizing the application of bifunctional microcapsule with "photocatalysis + energy regulation" in formaldehyde degradation.

[0005] To solve the above-mentioned technical problems, the technical solution adopted in this application is: the application of a bifunctional microcapsule in formaldehyde degradation, wherein the bifunctional microcapsule has a core-shell structure, wherein the core is a phase change material and the shell is a polymer layer containing TiO2 nanoparticles.

[0006] Furthermore, the core is a phase change material, paraffin or hexadecane.

[0007] Furthermore, in the polymer layer containing TiO2 nanoparticles, the mass content of TiO2 in the middle phase material of the polymer layer ranges from 0.5 to 2 wt%.

[0008] Furthermore, in the polymer layer containing TiO2 nanoparticles, the mass content of TiO2 in the middle phase material of the polymer layer ranges from 0.5 to 1.5 wt%.

[0009] Furthermore, in the polymer layer containing TiO2 nanoparticles, the mass content of TiO2 in the middle phase material of the polymer layer ranges from 0.5 wt%, 1.0 wt%, or 1.5 wt%.

[0010] Furthermore, in the polymer layer containing TiO2 nanoparticles, the mass content of TiO2 in the middle phase material of the polymer layer is in the range of 1.5 wt%.

[0011] Furthermore, the amount of the bifunctional microcapsules used in the formaldehyde solution to be degraded ranges from 1 to 4 g / 100 ml (i.e., 1 to 4 g of bifunctional microcapsules are added per 100 ml of formaldehyde solution to be degraded).

[0012] Furthermore, the dosage range of the bifunctional microcapsules in the formaldehyde solution to be degraded is 1.5-2.5g / 100ml (i.e., 1.5-2.5g of bifunctional microcapsules are added per 100ml of formaldehyde solution to be degraded).

[0013] Furthermore, the formaldehyde concentration in the degraded formaldehyde solution described in this application can be controlled within the range of 1–10 ppm, which meets the indoor air pollution standard test concentration.

[0014] Furthermore, under ultraviolet light irradiation, the bifunctional microcapsules undergo electron-hole separation in TiO2: TiO2 + hν → e - +h + Hole oxidation surface adsorbs H2O or OH- to generate ·OH, free radicals react with formaldehyde to generate CO2+H2O: HCHO+·OH→CO2+H2O. The uniform distribution of TiO2 in the microcapsule shell allows for more sufficient contact between light absorption and active sites, thereby improving the degradation rate.

[0015] Furthermore, the length of the ultraviolet light described in this application is <400nm.

[0016] The advantages and beneficial effects of this application are as follows:

[0017] 1. This application is the first to use TiO2-supported bifunctional microcapsules with specific structures and functions for the degradation of formaldehyde. This application can achieve efficient degradation of indoor formaldehyde and is suitable for photocatalytic reactions under UV light irradiation. The TiO2-supported bifunctional microcapsules of this application have a typical core-shell structure, in which the core (inner phase) is a phase change material (such as paraffin or hexadecane) and the outer shell is a polymer layer containing TiO2 nanoparticles. This bifunctional microcapsule can both promote photocatalytic activity and ensure the structural stability of the microcapsule framework.

[0018] 2. The TiO2-supported bifunctional microcapsules of this application significantly improve the separation efficiency of photogenerated carriers and enhance durability by uniformly dispersing TiO2 nanoparticles in a polymer shell. Simultaneously, the core of the microcapsule can further perform energy storage or thermal management functions, achieving a synergistic effect of "photocatalysis + energy regulation," which is unattainable with traditional powder catalysts. Furthermore, the results of SEM-EDS, FTIR, and cycling tests demonstrate that this application method achieves the advantages of reduced agglomeration and improved durability. The EDS mapping of this application shows uniform distribution of Ti and O, indicating that TiO2 is uniformly embedded in the shell, achieving the technical effect of avoiding agglomeration. In addition, the catalytic degradation of this application shows only a 4.1% loss of activity after 5 cycles, further demonstrating high durability and strong reusability.

[0019] 3. Traditional TiO2 has been mainly used in the fields of organic dye or VOC removal, water treatment, etc. However, this application is the first to load TiO2 into the shell of a microcapsule with a phase change core for the degradation of formaldehyde. This capsule maintains high photocatalytic activity and also has thermal energy storage capacity, which has application potential in the fields of indoor air purification and energy-saving materials.

[0020] 4. The bifunctional microcapsules for formaldehyde degradation described in this application exhibit ideal stability and durability during the degradation process. The durability of the 1.5wt% TiO2-loaded microcapsules was evaluated through five consecutive cycles of photocatalytic experiments. Under 180 minutes of UV irradiation, the removal efficiency was 89.5% in the first round and decreased to 85.4% in the fifth round, with a loss of only about 4.1% of activity. Therefore, the above conclusions indicate that the bifunctional microcapsule framework of this application exhibits excellent structural stability and durability in photochemical reactions and can maintain long-term stability in practical applications.

[0021] 5. The bifunctional microcapsules for formaldehyde degradation proposed in this application also have the potential for bifunctional applications: These TiO2-supported microcapsules also demonstrate the potential for bifunctional applications. The polymer shell not only promotes the photocatalytic degradation of formaldehyde under UV light irradiation, but the core region of the microcapsule can also store ultraviolet and visible light energy, thereby enhancing its application prospects in energy harvesting and environmental remediation. Attached Figure Description

[0022] Figure 1 (a) Scanning electron microscope image of solid microcapsules; (b) Crushed core-shell microcapsules (1.0 wt% TiO2-loaded bifunctional microcapsules).

[0023] Figure 2 Energy dispersive X-ray spectroscopy (EDS) analysis of bifunctional microcapsules.

[0024] Figure 3These are optical microscope images of the microcapsules, clearly showing their core-shell structure. Four of the images are microscopic images of double-emulsion droplets formed under different Qi / Qm ratios; where Qi is the flow rate of the external phase in the microfluidic device, and Qm is the flow rate of the middle phase in the microfluidic device.

[0025] Figure 4 The graphs show the degradation curves and degradation efficiency comparisons of formaldehyde by the bifunctional microcapsules of this application. In the graphs, a is the degradation curve of Examples 1-3, and b is the degradation efficiency comparison after five cycles.

[0026] Figure 5 (a) is the DSC curve of pure n-hexadecane and bifunctional microcapsules with a flow rate ratio of 4 / 5 between the inner and middle phases; (b) is the thermogravimetric curve of n-hexadecane, HDDA and bifunctional microcapsules. Detailed Implementation

[0027] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the examples. Obviously, the described embodiments are merely preferred embodiments, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] The TiO2-loaded bifunctional microcapsules of this application are prepared using the method disclosed in CN202311741575.4, including specific preparation schemes, steps, raw materials, and microfluidic equipment. Specifically, the raw materials include a middle phase, an outer phase, and an inner phase; the preparation device is a microfluidic device; the inner phase is paraffin material; the middle phase includes HDDA (1,6-hexanediol diacrylate), TiO2, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a photoinitiator; the outer phase fluid contains 6-9.0 wt% polyvinyl alcohol and 1-3% poly(ethylene glycol) block-poly(propylene glycol) block-polyvinyl alcohol deionized water. The obtained bifunctional microcapsules exhibit a core-shell structure that can be observed using SEM-EDS and TEM. See the attached document for details. Figure 1 As shown, Figure 1 (a) is a scanning electron microscope image of solid microcapsules; Figure 1 (b) is a pulverized core-shell microcapsule; from the attached Figure 1 It can be seen that (1.0wt% TiO2-supported bifunctional microcapsules):

[0029] Ti and O elements are evenly distributed in the outer shell layer, while C elements are concentrated in the core region;

[0030] The Ti–O–C absorption peak in FTIR (approximately 1090 cm⁻¹) -1 Both EDS mapping and other methods further demonstrate that TiO2 is uniformly embedded in the shell.

[0031] The integrity of its core-shell structure can be seen from the image. The figure shows a bifunctional microcapsule sample with a TiO2 loading of 1.0 wt%.

[0032] like Figure 2 The image shown is an energy-dispersive X-ray spectroscopy (EDS) image of the bifunctional microcapsule. This technique, used for compositional analysis, detects the characteristic X-rays emitted after a sample is bombarded by an electron beam to perform qualitative and quantitative analysis of the material's composition. EDS analysis reveals the distribution and proportion of Ti and O elements, indicating that TiO2 was successfully loaded into the outer shell. Figure 2 It is also a bifunctional microcapsule sample with a TiO2 loading of 1.0 wt%.

[0033] Figure 3 These are optical microscope images of microcapsules, clearly showing their core-shell structure. Four of the images show the double emulsion droplets formed at different Qi / Qm ratios.

[0034] Example 1:

[0035] Bifunctional microcapsules loaded with 0.5 wt% TiO2 were used to react an aqueous formaldehyde solution in the dark at 80°C for 1 hour (1 hour in the dark at 80°C: indicates adsorption equilibrium is reached under light-free conditions, allowing formaldehyde to reach a stable adsorption state on the microcapsule surface, thereby eliminating the interference of physical adsorption on the photocatalytic results; the formaldehyde concentration can be controlled within the range of 1–10 ppm, which meets the indoor air pollution standard test concentration; 1 g of the above-mentioned bifunctional microcapsules are added to every 50 ml of formaldehyde aqueous solution) to reach adsorption equilibrium. The formaldehyde concentration was monitored in real time using a gas detector, which can continuously track the changes in formaldehyde concentration during the reaction process.

[0036] This application degrades formaldehyde, corresponding to formaldehyde solution. The reason for using liquid phase is to facilitate concentration control and detection. Gaseous formaldehyde can be photocatalytically oxidized through gas-solid contact, and the reaction mechanism is the same as the above-mentioned liquid phase degradation.

[0037] The results of formaldehyde adsorption and degradation in Example 1 above are shown in Table 1 below:

[0038] Table 1. Results of formaldehyde adsorption and degradation in Example 1

[0039]

[0040] Note: In the table above, C / C0 is the ratio of formaldehyde concentration C at reaction time t to the initial concentration C0; a decrease in C / C0 indicates that degradation is underway.

[0041] The data follows pseudo-first-order dynamics:

[0042] ln(C0 / C)=kt

[0043] Its k value increases with the increase of TiO2 loading.

[0044] Example 2:

[0045] Bifunctional microcapsules loaded with 1.0 wt% TiO2 were used to react an aqueous formaldehyde solution in the dark at 80°C for 1 hour (1 hour in the dark at 80°C: indicates adsorption equilibrium under no light conditions, allowing formaldehyde to reach a stable adsorption state on the surface of the microcapsules, thereby eliminating the interference of physical adsorption on the photocatalytic results; the formaldehyde concentration can be controlled within the range of 1–10 ppm, which meets the indoor air pollution standard test concentration; 1 g of the above-mentioned bifunctional microcapsules were added to every 50 ml of formaldehyde aqueous solution) to reach adsorption equilibrium. The formaldehyde concentration was monitored in real time using a gas detector, which can continuously track the changes in formaldehyde concentration during the reaction process.

[0046] The results of formaldehyde adsorption and degradation in Example 2 above are shown in Table 2 below:

[0047] Table 2 Results of formaldehyde adsorption and degradation in Example 2

[0048]

[0049] Note: In the table above, C / C0 is the ratio of formaldehyde concentration C at reaction time t to the initial concentration C0; a decrease in C / C0 indicates that degradation is underway.

[0050] The data follows pseudo-first-order dynamics:

[0051] ln(C0 / C)=kt

[0052] Its k value increases with the increase of TiO2 loading.

[0053] Example 3:

[0054] Bifunctional microcapsules loaded with 1.5 wt% TiO2 were used to react an aqueous formaldehyde solution in the dark at 80°C for 1 hour (1 hour in the dark at 80°C: indicates that adsorption equilibrium was reached under light-free conditions, allowing formaldehyde to reach a stable adsorption state on the surface of the microcapsules, thereby eliminating the interference of physical adsorption on the photocatalytic results; the formaldehyde concentration can be controlled within the range of 1–10 ppm, which meets the indoor air pollution standard test concentration; 1 g of the above-mentioned bifunctional microcapsules were added to every 50 ml of formaldehyde aqueous solution) to reach adsorption equilibrium. The formaldehyde concentration was monitored in real time using a gas detector, which can continuously track the changes in formaldehyde concentration during the reaction process.

[0055] The results of formaldehyde adsorption and degradation in Example 3 above are shown in Table 3 below:

[0056] Table 3. Results of formaldehyde adsorption and degradation in Example 3

[0057]

[0058] Note: In the table above, C / C0 is the ratio of formaldehyde concentration C at reaction time t to the initial concentration C0; a decrease in C / C0 indicates that degradation is underway.

[0059] The data follows pseudo-first-order dynamics:

[0060] ln(C0 / C)=kt

[0061] Its k value increases with the increase of TiO2 loading.

[0062] Based on the above embodiments, the corresponding degradation curves and degradation efficiency comparison charts of the bifunctional microcapsules of this application for formaldehyde degradation are attached. Figure 4 As shown, from the appendix Figure 4 It can be seen that among them Figure 4 a is the degradation curve of Examples 1-3. Figure 4 b is a comparison of the degradation efficiency of 1.5wt% TiO2-loaded microcapsules after five cycles. It can be seen that the formaldehyde degradation efficiency increases with the increase of loading, and still maintains a high efficiency after five cycles, indicating that the formaldehyde degradation using this specific bifunctional microcapsule has the advantage of good stability.

[0063] According to the appendix Figure 4 The results showed that the durability of the 1.5 wt% TiO2-loaded microcapsules was evaluated through five consecutive cycles of photocatalytic experiments. Under 180 minutes of UV irradiation, the removal efficiency was 89.5% in the first round and dropped to 85.4% in the fifth round, with a loss of only about 4.1% of activity. This indicates that the microcapsule framework exhibits excellent structural stability and durability in photochemical reactions and can maintain long-term stability in practical applications.

[0064] Furthermore, this TiO2-supported bifunctional microcapsule demonstrates the potential for bifunctional applications. The polymer shell not only promotes the photocatalytic degradation of formaldehyde under UV light irradiation, but the core region of the microcapsule can also store ultraviolet and visible light energy, thus enhancing its application prospects in energy harvesting and environmental remediation. The core of the microcapsule used in this application is a phase change material (PCM, such as n-hexadecane), which can undergo endothermic and exothermic reactions at 20–25℃. Specific experimental verification is as follows:

[0065] DSC testing showed an endothermic peak of approximately 23.6℃ and an enthalpy change of approximately 145 J / g.

[0066] The surface temperature of the microcapsules gradually stabilized after rising by 3–5°C under light irradiation, indicating that the core absorbed and stored some photothermal energy.

[0067] Combining infrared thermal imaging and multi-cycle DSC testing, the reversible energy storage characteristics of the microcapsules were confirmed.

[0068] Therefore, it can be proven that the TiO2-loaded bifunctional microcapsules of this application have the bifunctional characteristic that "the core region can store ultraviolet and visible light energy".

[0069] As attached Figure 5 As shown, (a) is the DSC curve of pure hexadecane and bifunctional microcapsules with an internal and middle phase flow ratio of 4 / 5; (b) is the thermogravimetric curve of hexadecane, HDDA (1,6-hexanediol diacrylate) and bifunctional microcapsules.

[0070] The DSC curve can describe the relationship between the heat flux difference between the sample and the reference material and temperature or time under programmed temperature control. It can be seen that: Figure 5 a illustrates the melting and freezing DSC curves of bifunctional microcapsules prepared with pure hexadecane. Since only the phase change material undergoes a phase change in the temperature range of -40.0℃ to 40.0℃, the bifunctional microcapsules with HDDA shells can absorb and release less heat energy compared to pure hexadecane. Figure 5 b shows the thermogravimetric curves for three substances: pure hexadecane, pure HDDA, and a bifunctional capsule with an HDDA shell. All three substances decreased in weight with increasing temperature; pure hexadecane began to lose weight at around 68.4 °C and continued this trend until reaching 236.2 °C, at which point it had completely evaporated. Notably, the decomposition temperature of pure hexadecane was below its boiling point of 292 °C, indicating that the substance vaporized before reaching its boiling point. Conversely, the bifunctional capsule with an HDDA shell showed a significantly slower rate of weight loss compared to pure PCM. The thermal decomposition of these capsules was essentially completed at around 480 °C; furthermore, for the capsule with the HDDA shell, the 5% weight loss temperature (indicating thermal resistance) was approximately 124.3 °C; these findings suggest that the HDDA polymer shell effectively protects the PCM from leakage or rapid evaporation; essentially, the thermogravimetric analysis indicates that the bifunctional capsule with the HDDA shell exhibits enhanced thermal stability compared to pure hexadecane, with the HDDA polymer acting as a protective barrier against leakage or rapid evaporation.

Claims

1. The application of a bifunctional microcapsule in formaldehyde degradation, characterized in that: The bifunctional microcapsule has a core-shell structure, wherein the core is a phase change material and the shell is a polymer layer containing TiO2 nanoparticles.

2. The application of the bifunctional microcapsules according to claim 1 in formaldehyde degradation, characterized in that: The core is a phase change material, paraffin or hexadecane.

3. The application of the bifunctional microcapsules according to claim 1 in formaldehyde degradation, characterized in that: The polymer layer containing TiO2 nanoparticles, wherein the mass content of TiO2 in the middle phase material of the polymer layer ranges from 0.5 to 2 wt%.

4. The application of the bifunctional microcapsules according to claim 3 in formaldehyde degradation, characterized in that: The polymer layer containing TiO2 nanoparticles, wherein the mass content of TiO2 in the middle phase material of the polymer layer ranges from 0.5 to 1.5 wt%.

5. The application of the bifunctional microcapsules according to claim 4 in formaldehyde degradation, characterized in that: The polymer layer containing TiO2 nanoparticles, wherein the mass content of TiO2 in the middle phase material of the polymer layer is in the range of 0.5 wt%, 1.0 wt%, or 1.5 wt%.

6. The application of the bifunctional microcapsules according to claim 5 in formaldehyde degradation, characterized in that: The polymer layer containing TiO2 nanoparticles, wherein the mass content of TiO2 in the middle phase material of the polymer layer is in the range of 1.5 wt%.

7. The application of the bifunctional microcapsules according to claim 1 in formaldehyde degradation, characterized in that: The dosage range of the bifunctional microcapsules in the formaldehyde solution to be degraded is 1-4g / 100ml.

8. The application of the bifunctional microcapsules according to claim 7 in formaldehyde degradation, characterized in that: The dosage range of the bifunctional microcapsules in the formaldehyde solution to be degraded is 1.5-2.5g / 100ml.

9. The application of the bifunctional microcapsules according to claim 7 in formaldehyde degradation, characterized in that: The formaldehyde concentration in the degraded formaldehyde solution can be controlled within the range of 1–10 ppm, which meets the indoor air pollution standard test concentration.

10. The application of the bifunctional microcapsules according to claim 1 in formaldehyde degradation, characterized in that: Under ultraviolet light irradiation, the bifunctional microcapsules undergo electron-hole separation in TiO2: TiO2 + hν → e - +h+, H2O or OH adsorbed on the vacuolated surface - The formation of ·OH radicals, which react with formaldehyde to produce CO2 + H2O: HCHO + ·OH → CO2 + H2O; the length of the ultraviolet light is <400nm.

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