Photocatalytic Degradation Of Typical VOCs In Indoor Air

Indoor air quality is closely related to human health.In recent years,diseases such as allergic diseases and respiratory diseases have become more and more common,and it is widely believed that the occurrence of these diseases is closely related to indoor air quality.How to effectively eliminate indoor pollutants becomes crucial.Among many indoor air pollutants,VOCs are widely concerned because of their wide range of sources and great harm.Photocatalytic technology is an efficient and environmentally friendly method for purifying VOCs.In this thesis,Bi2WO6 was used as a catalyst and modified to prepare it,and it was applied to indoor photocatalytic purification of typical VOCs.The main work and conclusions are as follows:Firstly,Cd²⁺ion-doped Bi₂WO₆ was prepared by hydrothermal method.The photocatalytic effects of ion doping amount,hydrothermal reaction time,hydrothermal reaction temperature and pH on ion-doped Bi₂WO₆ were investigated.The degradation test showed that the optimal preparation conditions of Cd²⁺ion doped Bi₂WO₆ were:n?Cd/Bi?was 0.05,hydrothermal reaction temperature was 160?,hydrothermal reaction time was 16 h,and pH was 5.The degradation rate of rhodamine B by ion-doped Bi₂WO₆prepared under this condition can reach 86.5%in 50 min.Secondly,in order to improve the composite effect of the semiconductor photocatalyst when co-doped Bi₂WO₆,the dispersive experiment was first carried out on the ion-doped sample to determine the best dispersion effect.The co-doped Bi₂WO₆ was prepared by using Ag₃PO₄ as the composite semiconductor,and the photocatalytic degradation of toluene was verifid.It was found that when the mass ratio of polyacrylamide to sample was 0.1 and the ultrasonic dispersion time was 1 h,the dispersion of photocatalyst dispersion was the best,and when n?Ag₃PO₄/Cd-Bi₂WO₆?was0.3,its degradation efficiency to toluene was the highest,reaching 79.7%in 8h.Finally,the indoor air pollution was simulated by mixing VOCs of formaldehyde,toluene and benzene.The degradation efficiency of multi-component VOCs was investigated.The effects of three factors affecting the photocatalytic effect of VOCs on the amount of catalyst,initial toluene concentration and light intensity were investigated by using toluene as a model pollutant.Then the reaction kinetics of photocatalytic degradation was carried out.This study found that the degradation rate of formaldehyde,toluene and benzene in the mixed components was reduced by 7.7%,15.3%and 16.6%,respectively,compared with the single component.Under certain degradation conditions,the degradation rate of toluene showed a trend of increasing first and then decreasing with the increase of catalyst dosage and initialconcentration of toluene.While the increase of light intensity increased the degradation efficiency.The results of fitting under different conditions of initial concentration and light intensity of toluene showed that photocatalytic degradation of toluene basically conformed to the first-order reaction kinetics of L-H.