The Experimental Research On The Degradation Of Formaldehyde In Car By Loaded Composite Photocatalyst

With the increasing of people’s incomes and living standards, more and morefamilies could afford cars for transportation. While enjoying the convenience broughtby the car, lots of volatile organic pollutants emitted by automotive interiors anddecoration materials have become the murderer which seriously affects human health.Therefore, the research and exploitation of air purification products of the car also havethe profound significance for sustainable development.Photochemical catalytic technology is essential for the development of airpurification technology. The volatile organic pollutants inside the car can be rapidly andcompletely decomposed by using this technology. Now the titanium dioxide catalytictechnology has gained great successes, but how to reduce the photo generated holes andlight electrons recombination rate, and how to improve the catalytic activity of titaniumdioxide photo catalyst and solve the fixation under the visible light catalytic activity arestill in need of a further improvement for automobile air pollution control.In this study, the TiO₂-SiO₂composite photocatalyst was proposed according to theextension of traditional sol-gel method and load the glass fiber cloth which waspretreated first by dip-coating method. For the typical car air pollutant, formaldehydewas selected to be the experimental object. The impact of the pretreatment of glass fibercloth, the composite ratio of TiO₂and SiO₂, V-doping level, calcination temperature,film loaded numbers on degradation rate of formaldehyde were studied by thedegradation of formaldehyde and the structural performance of composite photocatalystwhich characterized by XRD and BET. This study also focus on the influence of initialformaldehyde concentration, light, temperature, humidity on photocatalytic degradation,firmness and durability of the supported composite photocatalyst. The study alsoanalyzed the application and market prospects of the product manufactured byexperiment. Finally, the study validated the effect of the supported compositephotocatalyst by using it in the car air pollution controllment and analyzed itsapplication fields and market value.The result obtained herein may indicate that:①The supported composite photocatalyst’s optimum preparation conditions were:Glass fiber cloth with the H₂SO₄/H₂O₂boiling pretreatment, the composite ratio of n（Ti）: n （Si）=5:1, V-doped ratio of n （V）: n （Ti+Si）=3%, the calcination temperature of600°C, film loaded numbers of three.②The analyzing results of XRD and BET investigate that the crystal of TiO₂wasanatase, and the average particle size of pure TiO₂（500℃） and V⁵⁺/TiO₂-SiO₂（600℃）was24.6nm and16.9nm. The specific surface area of V⁵⁺/TiO₂-SiO₂（600℃） was143.74m²/g, and the pore size was mainly concentrated on the2¹0nm, belong to themesoporous structure.③The study exploit the influence of initial formaldehyde concentration, light,temperature, humidity on formaldehyde photocatalytic degradation reaction shows that:（1） When the concentration was at a low level, the higher the initial concentration was,the more conducive to the adsorption of formaldehyde on the photocatalyst surface, sothe photocatalytic degradation rate was higher.（2） Under the UV light, theformaldehyde degradation rate of TiO₂-GF, TiO₂-SiO₂-GF and V⁵⁺/TiO₂-SiO₂-GF was45.81%、56.74%、65.40%after180min, and under the visible light it was27.95%、39.57%、54.1%. Compared to the UV light, the degradation rate of formaldehydedecreased by17.86%、17.17%、11.3%under the visible light in180min. It indicatedthat the photocatalytic activity under the visible light of V⁵⁺/TiO₂-SiO₂-GF compositephotocatalysts had been greatly improved.（3） When the temperature and concentrationwere at low levels, the degradation rate of formaldehyde was higher when thetemperature increased. When the reaction temperature arrived30℃, the degradation rateof formaldehyde was68.62%.（4） As relative humidity increased from35%to75%, thedegradation rate of formaldehyde presented the trend that first increased and thendecreased. When the relative humidity was55%, the photocatalytic activity of theV⁵⁺/TiO₂-SiO₂-GF composite photocatalysts was better and the degradation rate offormaldehyde was69.24%.④The composite film didn’t deformed after blew by the strong wind （about5m/s）for three hours. After reused10times, the degradation rate of formaldehyde was onlydecreased by3percent. Its firmness and durability were excellent.⑤After4h degradation, the formaldehyde and TVOC concentration in the carhad been greatly declined. The formaldehyde degradation rate was58.78%and theTVOC degradation rate was49.82%. The residual concentration of formaldehyde andTVOC were0.26mg/m³and0.838mg/m³. It was still exeeded the standard, but the harmwas greatly reduced. If the visible light was exist, the organic pollutant would bedegraded and reached the standard, so that the air pollution in the car got a effectivelycontrolled. ⑥Due to the excellent photocatalytic activity, the supported compositephotocatalyst could be used in research and development of sun visor, air conditioningsystem, air purifier, composite nanometer photocatalyst cavity spray, automobileinternal surface decoration cloth with photocatalytic function and other fields. So theloaded composite photocatalyst has a great potential of custom market.