Physical adsorption, chemisorption and catalytic oxidization for indoor VOCs removal

Adsorption and catalytic oxidation are two promising technologies for indoor volatile organic compounds (VOCs) removal. Combining experimental and modeling approach, the present study aimed at improving the understanding and modeling of adsorption of water-insoluble VOCs (e.g. toluene), and chemisorption and catalytic oxidization of water soluble VOCs (e.g. formaldehyde). For water-insoluble compounds, a dynamic volumetric method was developed for determination of VOC adsorption isotherm of active carbon at low concentration levels. Diffusion coefficient, partition coefficient and mass transfer coefficient of toluene in activated carbon were obtained by comparing numerical modeling results with the adsorption test data. Two mechanistic models were developed for VOCs removal by activated carbon filter bed. Both models fitted well with experimental data. Based on the combined analysis of the experimental and numerical results, external mass transfer and surface diffusion were found to be the controlling mechanisms in VOC adsorption by activated carbon. For water soluble compounds, research was conducted to evaluate the performance of selected chemisorbents and catalysts for formaldehyde removal at room temperature. The effects of concentration, relative humidity, velocity and co-existence of multi-VOCs on the removal performance were experimentally investigated. The effect of relative humidity was related to the micropore structure, properties of sorbent/catalyst materials and the chemical reaction mechanisms. Study of the effect of velocity through the media bed revealed the role of external mass transfer for different materials. Supported noble metal catalyst was found to have the most lasting activity and capacity for formaldehyde removal at typical indoor environmental conditions. Two mechanistic models were developed for filter bed employing chemisorption/catalytic oxidation methods. The models were able to predict the experimental data well. Future researches are needed in terms of byproduct generation, field performance evaluation, more cost-effective chemisorbent and catalyst materials, and easy to use design/optimization tool