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Volume 17, No. 1, January 2017, Pages 330-339 PDF(1.17 MB)  
doi: 10.4209/aaqr.2016.09.0397   

Using Box Modeling to Determine Photodegradation Coefficients Describing the Removal of Gaseous Formaldehyde from Indoor Air

Ming-Wei Lin1, Ching-Song Jwo1, Hsin-Jr Ho1, Liang-Yü Chen2

1 Department of Energy and Refrigerating Air-Conditioning Engineering, National Taipei University of Technology, Taipei 106, Taiwan
2 Department of Biotechnology, Ming Chuan University, Taoyuan 33343, Taiwan

 

Highlights
  • Box modeling was used to simulate the removal of gaseous formaldehyde indoors.
  • Degradation of HCHO from air is a zero-order heterogeneous catalytic reaction.
  • UV irradiation determines the ability of indoor air handling units to remove VOCs.

Abstract

 

Human exposure to volatile organic compounds (VOCs) indoors is receiving increasing attention. Formaldehyde (HCHO) is the most common VOC emitted from household materials and is associated with many health risks, including sick building syndrome. In this study, a simple box model was developed and applied to help understand the fate and degradation mechanisms of HCHO in the indoor environment. The model was validated using observations from an air handling system under different conditions. A UV/TiO2 filter reactor was installed in a closed box with the air conditioning unit. Three parameters, temperature, relative humidity, and circulation wind speed, were investigated for their effects on the performance of the air handling system. Our results show that the operation mode of the air handling system has a greater effect on the removal of HCHO than any of the air conditioning parameters. From a kinetic perspective, the removal of gaseous HCHO from a constant-volume box clearly represents a zero-order reaction. After UV irradiation with a TiO2 filter for 2 hours, the removal efficiency of gaseous HCHO increases to approximately 90%. Contributions to the removal of gaseous HCHO from natural dissipation, photodegradation, and photocatalytic oxidation decomposition are 12%, 30%, and 58%, respectively. Our results have implications for reducing indoor air pollution and reducing stress on air conditioning systems. Meeting these goals is beneficial for human health and energy conservation in modern society.

 

 

Keywords: Heterogeneous catalysis; Titanium dioxide; Air cleaning; Reaction kinetics.

 

 

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