Photocatalytic photooxidation is a new pollution control technology which has received more and more attention in recent years. The degradation rate of VOCs can reach 90%-95%. The technology refers to the use of a certain wavelength of light, the photocatalytic activity of the catalyst, make the adsorbent on the surface of the VOCs REDOX reaction, oxidize organic matter into CO2, H2O and inorganic small molecule substances.

Photocatalytic photooxidation has the advantages of selectivity, mild reaction conditions (normal temperature, atmospheric pressure), non-toxic catalyst, low energy consumption, simple operation, relatively low price, no by-product generation, the used catalyst can be recycled by physical and chemical methods, and has purification capacity for almost all pollutants, etc.

In recent years, nano-TiO2 photocatalytic oxidation technology has increasingly revealed its advantages. Nano-TiO2 is a new kind of fine inorganic product with high function, and its particle size is between 1-100nm. Due to its large specific surface area, high chemical stability and catalytic activity, low price and a wide range of sources, high UV light absorption rate, light corrosion resistance, and no toxicity, it has a strong adsorption effect on many organic substances, making it has obvious advantages in the removal of gaseous pollutants.

Nanometer TiO2 photocatalytic oxidation of light composite performance is good, can directly USES air as oxidant under atmospheric pressure, a variety of harmful gases into harmless gas, will not cause secondary pollution, reaction under the condition of ultraviolet radiation, reaction speed, time needed for only a few minutes or several hours, so is a very convenient VOCs purification technology.

In order to avoid the problem of separating TO2 nanoparticles from air in the practical process, nano-TO2 is needed to be supported on the carrier material and made into a supported nano-TO2 photocatalyst for easy use. Among them, the activated carbon fiber as a carrier, TiO2 in the form of a film load on it, can combine the advantages of the two substances, the harmful gas oxidation into CO2 and H2O, and has the effect of antibacterial and sterilization, non-toxic to the human body, do not need to replace the regeneration.

In recent years, the research and application of nano-TiO2 photocatalysis technology have developed rapidly in China. A variety of air purifiers developed and produced by Tsinghua Tongfang Clean Technology Co., Ltd. and Ningbo Huaguang Precision Instrument Co., Ltd. use nanoTO2 photocatalytic technology, and the products have been launched on the market. Beijing Zhongke Kylan Technology Development Co., Ltd. has designed and developed a series of photocatalytic air disinfection and purification products with photocatalytic technology. These photocatalytic air purifiers can be widely used in hospitals, schools, hotels and other public places. Cao Yaohua et al. studied the uniform precipitation method to prepare semiconductor material photocatalyst -- nano TO2 powder, particle size of 10nm, crystal type is anatase, introduced the experimental conditions of treating organic pollutant phenol by photocatalytic oxidation method, the degradation rate of phenol after ultraviolet light irradiation is 99.9%.

The results show that the nanometer powders of the composite rare earth compounds have strong REDOX performance, which is not comparable to other catalysts for automobile exhaust purification. Its application can completely solve the pollution problem of carbon monoxide, nitrogen oxides and carbon oxides in automobile exhaust gas. Activated carbon fiber materials, especially carbon fiber based on nanometer, show obvious advantages on the adsorption of organic matter. The specific surface area of carbon fiber is up to 2000m2g, while that of powdered activated carbon is only 1000m3g. Pnavarre et al used carbon fiber material to adsorb xylene and ethyl acetate, and studied the relationship among different carbon fibers, fiber layers, different gases and gas concentrations, and achieved good results.

In addition, the Japanese have studied the decomposition of gaseous organic matter by ultraviolet light. The results show that in the case of gas, organic chloride and chlorofluorocarbons can be decomposed in a very short time under the irradiation of 185nm ultraviolet light, and the decomposition rate of organic halides is higher than that of chlorofluorocarbons, trichloroethylene can be decomposed into the final products of CO2, Cl2, F2 and phosphotic gas in a few seconds. The intermediate products such as trichloroethylene and acetic acid can be removed by means of NaOH solution treatment or prolonged retention time.

In addition, foreign scientists using ozone as auxiliary oxidant also studied the photocatalytic oxidation of benzene and a variety of photocatalytic oxidation reaction mechanism for compensation technology including benzene, toluene, xylene and benzene waste gas study, studies have shown that photocatalytic oxidation reaction with active carbon adsorption, catalytic combustion method, such as compensation techniques, Photocatalytic oxidation of Ⅴ OCS has the advantages of high reaction efficiency, free from the influence of solvent molecules, easy recovery, fast reaction rate, etc., but this technology still has several key technical problems.

Deodorization principle of photocatalytic oxidation equipment

In recent years, many scholars have proposed solutions to the above problems, such as doping TiO2, precious metal surface deposition, semiconductor composite, surface photosensitization or super acidification, microwave preparation, etc., in order to improve the photocatalytic quantum efficiency of TiO2 or the utilization of visible light: By sol gel method, metal organic chemical vapor deposition method, cathodic electrodeposition method, such as a variety of methods, and by changing the drying, roasting and other conditions in the preparation of both solid and good photocatalytic activity of TiO membrane: put the microwave field, thermal catalysis and plasma technology and light catalytic coupling, applied to gas phase photocatalytic degradation of organic pollutants, in order to improve the efficiency of photocatalytic process, etc.