Research On Photothermal Degradation Of Indoor Air Pollutants

Nowdays,with the development of economic,people’s living standards gradually increased which leads to people more concerned about their health.Breathing is one of the reactions that human beings must have to react,so people are more concerned about the quality of air.However,today,because of industrial development and man-made destruction,the quality of air is deteriorating.How to effectively purification of air,especially the indoor air,has become a modern concern.The semiconductor photocatalyst is an effective methods to treat different types of pollutants which gradually gets people’s attention.The representative one is TiO₂ which is non-toxic,free cheap and can use the sun light effectively.However,it also has some shortcomings.It has low utilization of sunlight and can not capture and degradation of low concentrations of gaseous pollutants.Therefore,the researchers made the combination of photocatalysis and other techniques which can make up their own shortcomings and play their respective advantages.This is so called multi-technology.Among them,the photocatalytic technology-assisted adsorption technology is one of the popular technology.But the adsorbent only plays the role of adsorption,which means it can not purify the pollutants.When there is absence of light,the adsorbent can only adsorb pollutants,which is easy to achieve saturation and then desorption which causes the secondary pollution of the environment.In recent years,more and more researches have been concerned on the low temperature catalytic oxidation which has made some progress on the removal of HCHO and CO.The reason why the low temperature catalytic oxidation is popular is that its reaction condition is similar with the indoor environment.Therefore,we combine the thermal catalytic technology and photocatalytic technology that means the photocatalytic technology-assisted the low temperature catalytic oxidation technology which helps us remove pollutants effectively.When under the conditions of light,we use photocatalytic and when there is no light,we use thermal catalysis which we can achieve all-weather response.How to select the thermal catalyst,how to combine the thermal catalyst and photocatalyst and how to remove HCHO gas on the lab etc.All of these are problems.So our research work is mainly consists of the following several aspects.（1）Study on the removal of acetaldehyde from indoor air by thermal-photo reaction based on Au-based Catalyst.In this section,firstly we synthesised the thermal catalyst,the noble metal Au supported on different oxide carriers.By investigated in the removal of acetaldehyde vapor diluted in air,we selected ZrO₂ as the optimal thermal catalyst carrier.The pH of the solution and the calcination temperature of the solution during the preparation of Au/ZrO₂ were investigated.The results showed that Au/ZrO₂ with the pH of the solution is 10 and the calcination temperature of 5000 C had the best activity when adsorption and degradation the acetaldehyde.The characterization of XRD,TEM and particle size distribution etc told us that its the smaller particle size of Au particles synthesized under this condition made it had high activity.Finally,TiO₂ was synthesized by solvothermal process and then we combined TiO₂ and Au/ZrO₂ by impregnation.It was found that the Au/ZrO₂-TiO₂ catalyst could be used to degradation acetaldehyde no matter under light conditions and no light conditions.The preparation of this kind of photothermal catalyst could partially solve the shortcomings of adsorption photocatalysis and had potential application.（2）Preparation of yolk-shell photocatalyst and study on removal of organic pollutants.The yolk-shell ZrO₂/TiO₂ catalyst was synthesized by one-step solvothermal process.The synthesis steps was simple.The structure of the catalyst was characterized by XRD,FESEM,TEM,XPS etc.The catalyst surface has an appropriate amount of hydroxyl groups,which can effectively capture the photogenerated holes and generate hydroxyl radicals.ZrO₂/TiO₂ was a compound which means it did not cover the active sites with each other,besides the yolk-shell Zr O₂/TiO₂ catalyst had a large specific surface area and multiple active sites and multiple reflections of light within the sphere interior voids.In a word,the yolk-shell ZrO₂/TiO₂ catalyst had a good effect on removal of acetaldehyde,so it has the potential application in removal of indoor air pollutants.（3）Preparation of photothermal catalyst and study on its degradation of formaldehyde.We built a experimental device for formaldehyde degradation and detection successfully.The methods of the detection is the national standard GB/T 18204.2-2014 phenol reagent spectrophotometric method.Through the adjustment of this devices,we could make the device on a stable operation finally.Then we prepared Pt/ZrO₂/TiO₂ to remove the formaldehyde gas.The degradation efficiency of formaldehyde was found to be 63% at 60 min under room temperature.However,the photocatalytic effect was poor,so the device also need to be improved.All in all,we made a contribution to the removal of the formaldehyde gas in our group.