Air purification material based on photocatalytic oxidation technology and preparation method thereof

Abstract

The invention discloses an air purification material based on a photocatalytic oxidation technology and a preparation method thereof, and belongs to the technical field of environmental materials. The material adopts a three-dimensional porous carbonized cotton-carbon nanotube composite carrier, a copper-cerium co-doped titanium dioxide photocatalytic active component is loaded, and a dopamine derived carbon shell is introduced through an in-situ polymerization method to form a core-shell structure. Through the high adsorption-mass transfer synergistic effect of the carrier, the transition metal co-doped electron-hole separation strengthening effect and the stability protection mechanism of the carbon shell, the degradation efficiency of the material on formaldehyde and benzene series under indoor weak light reaches 90% or above, and the activity retention rate still exceeds 85% after the material is continuously used for 120 days. The problems that a traditional photocatalytic material is high in cost, poor in weak light response and prone to inactivation are solved, and the photocatalytic material is suitable for indoor scenes such as homes and offices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental functional materials, and particularly relates to a multifunctional air purification material for photocatalytic oxidation degradation of volatile organic compounds and sterilization and a preparation method thereof. BACKGROUND

[0002] Indoor air pollution has become a major environmental health problem in the current society, and volatile organic compounds such as formaldehyde and benzene series and microbial pollutants such as bacteria and viruses pose a serious threat to human health. Traditional air purification technologies have obvious limitations, and activated carbon adsorption is easy to saturate and fail, HEPA filters cannot remove gaseous pollutants, and ozone oxidation may produce harmful by-products.

[0003] In comparison, photocatalytic oxidation technology has unique advantages because it can efficiently degrade pollutants at room temperature and atmospheric pressure without producing secondary pollution, but there are still many technical bottlenecks in the practical application of existing photocatalytic materials that need to be broken through. Currently, commercial photocatalytic materials are mainly titanium dioxide, which has the advantages of good chemical stability, non-toxicity, and low cost, but it can only utilize less than 5% of the ultraviolet light part of sunlight, and the efficiency is even lower under indoor light conditions. In order to improve this situation, researchers have developed modification methods such as noble metal deposition, which can expand the light response range, but the high cost and easy oxidation of noble metals limit their practical application. Non-metallic doping can narrow the band gap, but it often leads to an increase in carrier recombination rate, which in turn reduces the quantum efficiency. The rapid recombination of electron-hole pairs during photocatalysis is another key factor that limits efficiency. Although the construction of heterojunctions or metal ion doping can promote charge separation, defects at the heterojunction interface can become new recombination centers, and too high a metal doping concentration can introduce additional recombination sites, which makes the improvement effect of existing technologies limited.

[0004] In terms of practical application, traditional photocatalytic materials also face the problem of insufficient pollutant adsorption capacity. The specific surface area of ordinary titanium dioxide powder is usually small, and the capture ability of indoor low-concentration pollutants is weak, which leads to insufficient contact of pollutants with active sites. Although the use of porous carriers for loading can increase the specific surface area, the adsorption performance of traditional carriers (such as activated carbon) is limited, and pollutants cannot be effectively enriched around the active sites, which restricts the degradation rate. The active components introduced into the material are easily deactivated by particulate matter coverage or light corrosion, and have a short service life. Some improvement schemes use noble metal doping (such as ruthenium and platinum), which results in high material cost and makes it difficult to scale up.

[0005] Researchers have made improvements through doping transition metals and constructing composite carriers, but there are still problems such as narrow weak light response range and insignificant stability improvement. Therefore, it is of great significance to develop a low-cost, high-weak-light-activity, and stable photocatalytic air purification material.

[0006] Compared with the prior art, the material of the present application has a significantly improved visible light utilization rate while maintaining the advantage of low cost, and the degradation rate of formaldehyde and the inactivation rate of common pathogenic bacteria both reach the industry-leading level. These breakthroughs provide a new way to solve the technical challenges faced by indoor air purification, and have important application value and market prospects. SUMMARY

[0007] The present application aims to overcome the problems of low purification efficiency, poor stability, and complex preparation process of photocatalytic air purification materials in the prior art, and to provide a low-cost, high-stability indoor photocatalytic air purification material and a preparation method thereof.

[0008] To achieve the above-mentioned purposes, the present application adopts the following technical solutions: An air purification material based on photocatalytic oxidation technology, composed of the following raw materials by weight: composite carrier 60-75, photocatalytically active component 20-30, and protective shell layer 3-10 parts.

[0009] Further, the composite carrier is a three-dimensional porous carbonized cotton-carbon nanotube composite carrier, wherein the mass ratio of carbonized cotton to carbon nanotube is (5-8):1, the porosity is ≥85%, and the specific surface area is 1200-1800 m² / g.

[0010] The carbonized cotton is prepared by carbonizing natural cotton fibers at 400-500℃, and the fiber diameter is 10-20μm; the carbon nanotube is hydroxylated single-walled carbon nanotube (diameter 3-8nm, length 300-800nm).

[0011] Further, the photocatalytically active component is copper-cerium co-doped titanium dioxide, wherein the doping amount of copper is 1-2% of the molar amount of titanium dioxide, and the doping amount of cerium is 1.5-3% of the molar amount of titanium dioxide.

[0012] Further, the protective shell layer is a dopamine-derived carbon shell, coated on the surface of the photocatalytically active component, with a thickness of 3-8nm, and containing 1-2wt% of nitrogen element in the carbon shell.

[0013] The dopamine-derived carbon shell is prepared by polymerizing dopamine under alkaline conditions and then carbonizing at 300-400℃.

[0014] The present application also provides a preparation method of the above-mentioned air purification material based on photocatalytic oxidation technology, comprising the following steps: (1) Preparation of carbonized cotton-carbon nanotube composite carrier: carbonize natural cotton fibers at 400-500℃ under nitrogen atmosphere for 2-3h, crush, and disperse hydroxylated carbon nanotubes in deionized water at a mass ratio of (5-8):1, ultrasonic for 2-3h, and freeze-dry to obtain the composite carrier.

[0015] (2) Preparation of copper-cerium co-doped titanium dioxide precursor: dissolve the titanium source, copper source and cerium source in ethanol-water mixed solution (volume ratio 1:1) according to the proportion, add acetic acid to adjust the pH to 2-3, and stir until a sol is formed.

[0016] (3) Loading of active components: add the composite carrier to the precursor solution, immerse for 4-6 h, and then microwave-assisted drying (power 300-500 W, time 10-15 min), repeat the immersion-drying 2-3 times.

[0017] (4) Coating of dopamine carbon shell: disperse the product of step (3) in Tris-HCl buffer solution (pH=8.5), add dopamine (concentration 0.5-1 g / L), stir for 6-8 h to allow in-situ polymerization of dopamine, filter, and then carbonize at 300-400 ℃ under nitrogen atmosphere for 1-2 h.

[0018] (5) Post-treatment: wash with deionized water and dry at 60-80 ℃ to obtain the air purification material.

[0019] Further, in the preparation method, the titanium source is tetrabutyl titanate, the copper source is copper nitrate, and the cerium source is cerium nitrate; in the ethanol-water mixed solution, the concentration of the titanium source is 0.2-0.5 mol / L. The present application has the following advantages: 1. The present application uses natural cotton fibers and transition metals (copper and cerium) as raw materials, replacing noble metals and high-priced carbon materials, and the raw material cost is reduced by more than 60%; the preparation process does not require high-temperature and high-pressure equipment, and the energy consumption is low, which is suitable for large-scale production.

[0020] 2. The copper-cerium co-doped material of the present application cooperatively broadens the light response range of titanium dioxide to 580 nm, and the degradation efficiency of formaldehyde and benzene series under indoor weak light (≤500 lux) can reach more than 90%, solving the limitation of traditional materials that can only respond to ultraviolet light.

[0021] 3. The dopamine-derived carbon shell of the present application effectively protects the active components, avoids covering or photo-corrosion of the active components, and the activity retention rate is still more than 85% after 120 days of continuous use, and the service life is more than twice that of traditional materials.

[0022] 4. The high adsorption performance of the composite carrier of the present application enriches pollutants around the active components, improves the degradation rate, realizes the integration of "adsorption-degradation", and the purification efficiency is improved by more than 30% compared with single catalytic material. The air purification material has the advantages of high purification efficiency, good stability and long service life, and can be widely used in air purification of indoor places such as family, office and car, and has broad market prospect. DETAILED DESCRIPTION

[0023] The application will be described in further detail below with reference to specific embodiments. Example 1

[0024] Preparation of composite carrier: 50 g of natural cotton fibers were placed in a tube furnace and heated to 400 ℃ at a heating rate of 5 ℃ / min under a nitrogen atmosphere, and carbonized for 2 h; after cooling, the fibers were ground to a particle size of 50-100 μm, and then added to 500 mL of deionized water with 10 g of hydroxylated single-walled carbon nanotubes (diameter 3 nm, length 300 nm), and ultrasonically treated for 2 h (power 500 W); the resulting mixture was freeze-dried for 48 h to obtain a carbonized cotton-carbon nanotube composite carrier (mass ratio 5:1).

[0025] Preparation of active component precursor: 0.2 mol of tetrabutyl titanate, 0.002 mol of copper nitrate, and 0.003 mol of cerium nitrate were added to 100 mL of an ethanol-water mixture (volume ratio 1:1), and after stirring for 5 min, acetic acid was added dropwise to adjust the pH to 2, and stirring was continued for 30 min to form a yellowish sol.

[0026] Loading of active component: 20 g of the composite carrier was added to the above sol, and immersed at room temperature for 4 h; after removal, it was placed in a microwave oven and dried at a power of 500 W for 10 min; the immersion-drying operation was repeated twice to obtain a carrier loaded with copper-cerium co-doped titanium dioxide.

[0027] Carbon shell coating: the above carrier was dispersed in 200 mL of Tris-HCl buffer (pH=8.5), and 0.1 g of dopamine was added, and stirred at room temperature for 6 h; after filtration, the product was placed in a tube furnace, and heated to 300 ℃ at a heating rate of 3 ℃ / min under a nitrogen atmosphere, and carbonized for 1 h.

[0028] Post-treatment: the product was washed with deionized water 3 times, and vacuum dried at 60 ℃ for 12 h to obtain an air purification material. Example 2

[0029] Preparation of composite carrier: 60 g of natural cotton fibers were carbonized at 450 ℃ for 2.5 h under a nitrogen atmosphere (heating rate 5 ℃ / min); after grinding, the fibers were dispersed in 600 mL of deionized water with 10 g of hydroxylated single-walled carbon nanotubes (diameter 5 nm, length 500 nm), and ultrasonically treated for 2.5 h (power 500 W); freeze-drying was performed to obtain a composite carrier (mass ratio 6:1).

[0030] Preparation of active component precursor: 0.3 mol of tetrabutyl titanate, 0.005 mol of copper nitrate, and 0.007 mol of cerium nitrate were dissolved in 150 mL of an ethanol-water mixture (1:1), acetic acid was added to adjust the pH to 2.5, and stirring was continued for 35 min to form a sol.

[0031] Active component loading: 25 g of the composite support was immersed for 5 h, dried with 400 W microwave for 12 min, repeated for 3 times.

[0032] Carbon shell coating: dispersed in 250 mL Tris-HCl buffer (pH = 8.5), 0.2 g dopamine was added and stirred for 7 h; carbonized at 350 ℃ for 1.5 h under nitrogen atmosphere (heating rate 3 ℃ / min).

[0033] Post-processing: after washing, vacuum dried at 70 ℃ for 12 h to obtain the product. Example 3

[0034] Preparation of the composite support: 80 g of natural cotton fibers was carbonized at 500 ℃ for 3 h under nitrogen; after crushing, 10 g of hydroxylated carbon nanotubes (diameter 8 nm, length 800 nm) was dispersed in 800 mL of deionized water, and ultrasonic was performed for 3 h; freeze-drying to obtain the support (mass ratio 8:1).

[0035] Preparation of the active component precursor: 0.5 mol of tetrabutyl titanate, 0.01 mol of copper nitrate, and 0.015 mol of cerium nitrate were dissolved in 250 mL of ethanol-water mixture, the pH was adjusted to 3, and stirring was performed for 40 min to form a sol.

[0036] Active component loading: 30 g of the composite support was immersed for 6 h, dried with 300 W microwave for 15 min, repeated for 3 times.

[0037] Carbon shell coating: dispersed in 300 mL Tris-HCl buffer, 0.3 g dopamine was added and stirred for 8 h; carbonized at 400 ℃ for 2 h under nitrogen.

[0038] Post-processing: after washing, vacuum dried at 80 ℃ for 12 h to obtain the product. Example 4

[0039] Preparation of the composite support: 55 g of natural cotton fibers was carbonized at 420 ℃ for 2.2 h under nitrogen; after crushing, 10 g of hydroxylated carbon nanotubes was dispersed in 550 mL of deionized water, and ultrasonic was performed for 2.3 h; freeze-drying to obtain the support (mass ratio 5.5:1).

[0040] Preparation of the active component precursor: 0.3 mol of tetrabutyl titanate, 0.006 mol of copper nitrate, and 0.008 mol of cerium nitrate were dissolved in 150 mL of ethanol-water mixture, the pH was adjusted to 2.3, and stirring was performed for 35 min to form a sol.

[0041] Active component loading: 22 g of the composite support was immersed for 5 h, dried with 450 W microwave for 12 min, repeated for 2 times.

[0042] Carbon shell coating: dispersed in 220 mL Tris-HCl buffer, 0.15 g dopamine was added and stirred for 7 h; carbonized at 320 ℃ for 1.2 h under nitrogen.

[0043] Post-treatment: vacuum drying at 70℃ for 12h after washing to obtain the product. Example 5

[0044] Composite carrier preparation: 70g natural cotton fiber was carbonized at 480℃ for 2.8h under nitrogen; after crushing, 10g hydroxylated carbon nanotubes were dispersed in 700mL deionized water, and ultrasonic treatment was performed for 2.8h; freeze-drying to obtain the carrier (mass ratio 7:1).

[0045] Active component precursor preparation: 0.4mol tetrabutyl titanate, 0.007mol copper nitrate, and 0.012mol cerium nitrate were dissolved in 200mL ethanol-water mixture, the pH was adjusted to 2.8, and stirring was performed for 45min to form a sol.

[0046] Active component loading: 28g of the composite carrier was immersed for 5.5h, then dried by microwave at 350W for 14min, and the process was repeated for 3 times.

[0047] Carbon shell coating: dispersed in 280mL Tris-HCl buffer, 0.25g dopamine was added and stirred for 7.5h; carbonization at 380℃ for 1.8h under nitrogen.

[0048] Post-treatment: vacuum drying at 75℃ for 12h after washing to obtain the product.

[0049] Effect test The air purification materials prepared in Examples 1-5 were subjected to performance test, and the test conditions were as follows: Test environment: a closed experimental cabin with a volume of 1m³, temperature 25℃, relative humidity 50%, and light intensity 500lux (simulated indoor natural light).

[0050] Initial concentration: formaldehyde 1mg / m³, benzene 0.5mg / m³.

[0051] Test method: gas chromatography was used to determine the pollutant concentration in the cabin at different time points, and the degradation efficiency was calculated; after continuous use for 120 days, the test was performed again, and the activity retention rate was calculated.

[0052] The test results show that the degradation efficiency of formaldehyde and benzene series under indoor weak light (≤500lux) is more than 90%, and the activity retention rate is still more than 85% after continuous use for 120 days.

[0053] The present application uses natural cotton fiber and transition metals (copper and cerium) as raw materials, replacing noble metals and high-valence carbon materials, and the raw material cost is reduced by more than 60%; the preparation process does not require high-temperature and high-pressure equipment, the energy consumption is low, and it is suitable for large-scale production.

[0054] The copper-cerium co-doped cooperates to broaden the light response range of the titanium dioxide to 580nm, and the degradation efficiency of formaldehyde and benzene series under indoor weak light (less than or equal to 500 lux) can reach more than 90%, solving the limitation that the traditional material can only respond to ultraviolet light.

[0055] The dopamine-derived carbon shell of the application effectively protects the active component, avoids covering or photo-corrosion of the active component, and the activity retention rate is still more than 85% after 120 days of continuous use, and the service life is more than twice that of traditional materials.

[0056] The high adsorption performance of the composite carrier of the application enriches pollutants around the active component, improves the degradation rate, realizes the integration of "adsorption-degradation", and the purification efficiency is more than 30% higher than that of single catalytic material. The air purification material has the advantages of high purification efficiency, good stability, long service life, etc., and can be widely applied to air purification of indoor places such as family, office, car, etc., and has wide market prospect.

[0057] In summary, the photocatalytic air purifier of the application provides a technical solution with superior performance and strong practicability for effective management of indoor air pollution, and has wide application prospect and market potential.

[0058] The above description is only the preferred embodiment of the application and the explanation of the applied technical principles. It should be understood by those skilled in the art that the scope of the application involved in the application is not limited to the technical solutions formed by the specific combination of the above technical features, and also covers other technical solutions formed by the combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by the mutual replacement of the above features and the technical features disclosed in the application (but not limited to) with similar functions.

[0059] Finally, it should be pointed out that the above preferred embodiments are only used to illustrate the technical solutions of the application and not to limit, although the application has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the application.

Claims

1. An air purification material based on the photocatalytic oxidation technology, characterized by, The application relates to an air purification material based on photocatalytic oxidation technology, which comprises a composite carrier, a photocatalytic active component and a protective shell layer; the composite carrier is a three-dimensional porous carbonized cotton-carbon nanotube composite carrier, the mass ratio of carbonized cotton to carbon nanotube is (5-8):1, the porosity is greater than or equal to 85%, and the specific surface area is 1200-1800 m2 / g; the photocatalytic active component is copper-cerium co-doped titanium dioxide, the doping amount of copper is 1-2% of the molar amount of titanium dioxide, and the doping amount of cerium is 1.5-3% of the molar amount of titanium dioxide; and the protective shell layer is a dopamine-derived carbon shell, which is coated on the surface of the active component and has a thickness of 3-8 nm and contains 1-2 wt% of nitrogen elements.

2. The air purification material according to claim 1, wherein, The carbonized cotton is prepared by carbonizing natural cotton fibers at 400-500 DEG C, and the fiber diameter is 10-20 mu m; the carbon nanotube is a hydroxylated single-walled carbon nanotube with a diameter of 3-8 nm and a length of 300-800 nm.

3. The air purification material of claim 1, wherein, The dopamine-derived carbon shell is prepared by polymerizing dopamine under alkaline conditions and then carbonizing at 300-400 DEG C.

4. A method of producing an air purification material based on the photocatalytic oxidation technology according to any one of claims 1 to 3, characterized by, The application further discloses a preparation method of the air purification material based on photocatalytic oxidation technology. (1) preparing a carbonized cotton-carbon nanotube composite carrier: carbonizing natural cotton fibers at 400-500 DEG C under a nitrogen atmosphere for 2-3 h, crushing, dispersing in deionized water according to the mass ratio (5-8):1 of the carbonized cotton to the hydroxylated carbon nanotube, ultrasonicating for 2-3 h and freeze-drying to obtain the composite carrier; (2) preparing a copper-cerium co-doped titanium dioxide precursor: dissolving a titanium source, a copper source and a cerium source in an ethanol-water mixed solution (volume ratio 1:1) according to a proportion, adding acetic acid to adjust the pH to 2-3, and stirring until a sol is formed; (3) loading the photocatalytic active component: adding the composite carrier in step (1) into the precursor solution in step (2), immersing for 4-6 h, microwave-assisted drying at a power of 300-500 W for 10-15 min, and repeating the immersing-drying for 2-3 times; (4) coating the protective shell layer: dispersing the product in step (3) in a Tris-HCl buffer solution (pH=8.5), adding dopamine to a concentration of 0.5-1 g / L, stirring for 6-8 h, filtering, carbonizing at 300-400 DEG C under a nitrogen atmosphere for 1-2 h, and (5) post-treatment: washing the product in step (4) with deionized water and drying at 60-80 DEG C to obtain the air purification material based on photocatalytic oxidation technology.

5. The method for preparing air purification materials based on photocatalytic oxidation technology according to claim 4, characterized in that, In step (2), the titanium source is tetrabutyl titanate, the copper source is copper nitrate, and the cerium source is cerium nitrate; and the titanium source concentration in the ethanol-water mixed solution is 0.2-0.5 mol / L.