| Since the90’s of last century, a large number of new buildings have been built inChina. Indoor air pollution caused by volatile organic compounds (VOC), which emitfrom building decoration and furniture, is harmful to people’s health and life quality. Itis a social problem which is concerned by people and the leaders. And how to controlthe indoor VOC pollution is a hot topic in indoor air research field in China. IndoorVOC removal by purification materials is an important approach to solve the problem.Adsorption and catalytic reaction are proven or promising approaches for indoor VOCremoval. However, there are still some key problems which are not clear, such as themethod for selecting adsorption materials and designing their performance, and themechanism of thermal catalytic oxidation. To address the above issues, the followinginvestigations have been carried out in this study:New parameters such as the equivalent clean air volume Va,cand itsdimensionless express Va,c*were developed for the evaluation the VOC removalcapability of purification materials. Traditional evaluation parameters for VOCpurification materials are impossible to evaluate and estimate their performancein real air purification process (non-steady-state) during a given time. By usingnew evaluation parameters, the problem in comparing VOC removalperformance by different purification method (such as adsorption and catalyticoxidation) can be solved. The model of VOC removal by adsorption material wasestablished, and the Va,c*of the adsorption material was expressed as a function of timeand some key parameters, such as the diffusion coefficient in material (D), the partitioncoefficient (K) and the external mass transfer coefficient (hm). Therefore, the capabilityof different purification materials can be estimated and compared, which overcomes theshortage of existing evaluation parameters.An experimental method and its procedures were established for estimating theVa,c*of adsorption materials. That is, by measuring the D and K between lowconcentration VOC and adsorption materials under certain experimentalconditions, the Va,c*under real operation condition is estimated. In practical, thismethod can be used for the selection of adsorption material, the design of adsorption filter and the estimation of the life time.Through experimental study, the kinetic characteristics of formaldehyde removalby thermal catalyst were obtained. It was found that the mechanism follows thebimolecular L-H equation, which is, the adsorbed formaldehyde reacts with the reactiveoxygen species on the surface of the catalyst, and competition adsorption occurs whenthe formaldehyde concentration is high. The parameters in the equation were measuredand the influence of temperature was considered. The apparent activation energy in thereaction was obtained, which explained the mechanism of why the reaction can takeplace at room temperature. Therefore, the performances of thermal catalytic oxidationair cleaners can be designed.The application strategies of using purification materials for indoor VOC controlhave been proposed. The method for selecting purification mode was proposed. And bymodeling of emission control by adsorption material, the analytical solution wasobtained. And the dimensionless equation for determining the life time of adsorptionmaterial was obtained.These investigations can be the basis of evaluating and designing theapplications of purification materials for indoor VOC removal. |
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