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

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/TiO 2 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 TiO 2 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.

Investigation of A Potted Plant (Hedera helix) with Photo-Regulation to Remove Volatile Formaldehyde for Improving Indoor Air Quality

“…4(B), the gaseous HCHO level in the air was rapidly reduced to a safe level in the fast discharge mode; but the other observation needed more time to achieve a similar level in the slow release mode. Our previous study demonstrated the temperature and relative humidity of indoor air are not sensitive to HCHO removal via natural dissipation and photo-degradation (Lin et al, 2017). However, the time course of gaseous HCHO removal presented a photo-regulated phenomenon by switching the illumination environment.…”

“…The lighting would increase the air temperature and indirectly enhance the vaporized rate of HCHO from the supported material into the air. Real absorbents have pores of various sizes; the diffusion plays an increasingly important role to decrease the observed activation energy, and the reaction order approaches unity (Lin et al, 2017).…”

Major Advances and Challenges in Heterogeneous Catalysis for Environmental Applications: A Review

“…For instance, formaldehyde is the most common VOC released from households and is related to many health risks, including sick building syndrome. Photocatalytic materials were also proven to be effective for degradation of these contaminants [95]. After UV irradiation with a TiO 2 filter for 2 hours, the removal efficiency of gaseous formaldehyde increases to approximately 90%.…”

Design and Synthesis of Microencapsulated Phase-Change Materials with a Poly(divinylbenzene)/Dioxide Titanium Hybrid Shell for Energy Storage and Formaldehyde Photodegradation

“…Some research studies clarified that TiO 2 NPs with a high surface area have a powerful ability for HCHO photodegradation due to their n-type semiconductor feature. − Besides, as a typical photocatalytic oxidation reaction, photodegradation of the indoor pollutant HCHO has been realized by TiO 2 , where the catalytic capability is affected by many factors especially temperature. According to the Arrhenius’ law, a higher temperature could promote the adsorption capacity of gas molecules to anchor onto the catalyst surfaces and accelerate the degradation rate. , To design and fabricate an integrated system with heat-supply and photocatalytic ability is an effective and novel method to achieve the efficient degradation of HCHO gas. Therefore, the MEPCM microcapsules in this research can be built as a platform for the effective photocatalysis of HCHO.…”

“…According to the Arrhenius' law, a higher temperature could promote the adsorption capacity of gas molecules to anchor onto the catalyst surfaces and accelerate the degradation rate. 49,50 To design and fabricate an integrated system with heat-supply and photocatalytic ability is an effective and novel method to achieve the efficient degradation of HCHO gas. Therefore, the MEPCM microcapsules in this research can be built as a platform for the effective photocatalysis of HCHO.…”