Application of Nano-photocatalytic Technology in Air Pollution Control

Application of Nano-photocatalytic Technology in Air Pollution Control

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Nowadays, the problem of environmental pollution has become a global problem. Strengthening environmental protection and promoting the coordinated development of environment and economy are the main means of world economic development. As a kind of environmental pollution, air pollution should be strengthened to alleviate the problems brought by greenhouse effect to social development, which is conducive to the construction of a harmonious society. Based on this, this paper mainly analyzes nano-photocatalytic technology and studies its application in air pollution control for reference.

Key words: nanometer photocatalytic technology; Air pollution; Governance application

The application of nano-photocatalytic technology in air pollution can improve the level of air pollution control. Nano-photocatalytic technology has become the most advanced air purification technology in current society because of its good photosensitive effect, easy to reach its reaction conditions, high efficiency and no harm to the environment and human body. Analyzing and studying nano-photocatalytic technology and fully understanding its application in air pollution control will help solve the serious smog problem in China, optimize people's living environment and promote rapid economic development.

First, the theory of nanometer photocatalytic technology

As one of the "inexhaustible" clean energy sources, the effective use of solar energy is particularly important in today's increasingly serious energy shortage and environmental pollution. Photocatalytic pollutant degradation technology can not only make full use of solar energy, but also solve the problem of air pollutants treatment. As a new air pollution control method, nano-photocatalytic technology has great application potential in air pollution control. Compared with the traditional physical adsorption method (activated carbon), using nano-photocatalytic technology to purify air has the following advantages: (1) catalytic degradation can be carried out at normal temperature and pressure; Simple operation; Under the excitation of sunlight, nitrogen oxides, VOCs and other pollutants in the atmosphere can be effectively removed without causing secondary pollution.

The theory of photocatalytic technology is mainly based on the "V-Ji Island-Honda" effect. In the late 1970s, Frank and Bard studied the photolysis of cyanide in water on the surface of TiO _ 2, and Carey studied the degradation of polychlorinated biphenyls under the ultraviolet irradiation of TiO _ 2, which greatly promoted the research of photocatalytic technology in environmental pollution control. The mechanism of catalytic oxidation of semiconductor materials is that when the semiconductor catalyst is irradiated by light with energy greater than the forbidden band width, the electrons in the valence band (va-band, VB) are excited, jumping over the forbidden band and entering the conductive band (CB), and holes () corresponding to the electrons () are generated in the valence band, that is, free electron-hole pairs are generated. Under the action of electric field, active electrons and holes can be separated from the semiconductor. At the same time, there is recombination of electrons and holes. Valence band hole () oxidizes adsorbed H2O to hydroxyl radical (), and conduction band electron () reduces O2 in air to superoxide radical (). These two kinds of free radicals () are the key active groups to degrade pollutants. The reaction principle is as follows:

Second, the practical application of nanometer photocatalytic technology

Nano-photocatalytic technology is widely used in air pollution control. As a photocatalyst with good application effect, titanium dioxide has good acid and alkali resistance, photo-corrosion resistance, good chemical stability, rich sources, large energy, and great potential for photogenerated electrons and holes. However, in the practical application of nano-photocatalytic technology, it is easily affected by the concentration of catalyst and organic matter. Therefore, in the process of air pollution control, relevant personnel should pay attention to the influence of these factors on photocatalytic technology.

Effect of (1) catalyst on nano-photocatalytic technology. The principle of nano-photocatalytic technology is to purify the atmosphere by using catalysts. During the reaction, the surface area and particle size of the catalyst will affect the nano-photocatalytic reaction. For example, when the particle size of the catalyst is decreasing, the particles per unit mass in the solution will increase, although the light absorption efficiency will increase, but the light absorption is not easy to saturate; The increase of surface area of catalyst system means that the area of catalyst participating in the reaction increases, which is beneficial to catalytic reaction, and vice versa. In addition, the surface hydroxyl group and mixed crystal effect of the catalyst are another factor affecting the nano-photocatalytic reaction.

(2) The influence of light source and light intensity on air pollution. The light sources commonly used in nano-photocatalytic technology are black light, high and low pressure mercury lamp, ultraviolet lamp, germicidal lamp and so on. The wavelength is in the range of 200-400 nanometers. Generally speaking, in the process of nano-photocatalytic reaction, the stronger the light intensity, the faster the catalytic reaction speed, which will gradually become constant, but the quantum efficiency of light will change with the change of light intensity. In addition, at different PH values, cocatalysts and inorganic salts are added. It will also affect the reaction of nano-photocatalytic technology to a certain extent.

Thirdly, the combination of nanometer photocatalytic air pollution control technology and other technologies.

(1) Indoor pollution control and ventilation technology. At present, there are two common indoor environment purification and ventilation technologies: active and passive. The former organically combines indoor environment purification device with mechanical ventilation system, while the latter adopts air purification filter combined with natural ventilation system. Both technologies involve efficient ventilation technology. The former is mainly aimed at exogenous pollution, and high efficiency and low resistance filtration can be used. The latter is mainly aimed at endogenous pollution, and the more effective ways are various indoor purification technologies. At present, the main ventilation methods are mixed ventilation, displacement ventilation and personalized air supply. The purpose of mixed ventilation and displacement ventilation is to create an indoor air-sensitive environment. When the set temperature of air conditioner increases, the thermal comfort of indoor personnel will inevitably decrease. Personalized air supply is subject to more restrictions in practical use and less restrictions in practical engineering.

(2) filtration technology. Filtration technology mainly includes nanofiber filtration technology, photocatalytic fiber filtration technology and membrane filtration technology. Nanofiber filtration technology is a composite filter material with a certain gradient structure, which can greatly improve the filtration performance. It has been used in indoor air purification, water purification and other fields, and is expected to achieve large-scale engineering application. Nano-photocatalytic technology is a new method to treat air pollutants, which has great application potential in air pollution control.

Four. conclusion

In the process of controlling air pollution, the effect of using nano-photocatalytic technology alone is not particularly obvious. Therefore, in the process of air pollution control, relevant personnel should effectively combine nano-photocatalytic technology with other advanced air purification technologies to improve the effect of air pollution control and protect people's health.

References:

[1] Cao Junji, Huang Yu. The application of nanometer photocatalytic technology in air pollution control [J]. Science and Technology Herald, 20 16, 17: 64-7 1.

[2] Wang Shaoyu. Study on the application of photocatalytic technology in indoor air purifier [D]. Zhejiang University, 20 13.

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