TY - JOUR
T1 - An experimental study of relative humidity effect on VOCs' effective diffusion coefficient and partition coefficient in a porous medium
AU - Xu, Jing
AU - Zhang, Jianshun S.
N1 - Funding Information:
“Although the research described in this article has been funded wholly or in part by the United States Environmental Protection Agency through grant/cooperative agreement CFDA #66.606, Sponsor Award #X-83269001-0 to Syracuse University, Strategically Targeted Research in Intelligent Built Environmental Systems, it has not been subjected to the Agency’s required peer and policy review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred.”
PY - 2011/9
Y1 - 2011/9
N2 - Most building materials are porous media. As a critical environmental factor, the influence of relative humidity on VOCs diffusion is still not well understood. In this study, VOC transport and sorption in a porous medium in the building materials (calcium silicate) were measured under three levels of relative humidity (25%, 50% and 80%) by using a dynamic dual chamber method. Tests were conducted for water-soluble compound (formaldehyde) and non-soluble compound (toluene). In addition, the transport of acetaldehyde, hexanal, benzaldehyde, butanol and decane through the calcium silicate were also tested at 50%RH to study the relationship between the effective diffusion coefficient (De), partition coefficient (Kma) and the VOCs' physical properties (molecular weight, vapor pressure and Henry's law constant). Experimental results showed that: relative humidity in the 80%RH led to a higher partition coefficient for formaldehyde compared to 50%RH. However, between 25% and 50%RH, there was no significant difference in partition coefficient. Partition coefficient of toluene decreased with the increase of humidity due to competition of water molecules for pore surface area and the non-solubility nature of toluene. Relative humidity had no significant influence on the effective diffusion coefficient on both formaldehyde and toluene for the range of moisture conditions tested. The solubility of VOCs was found to correlate with the partition coefficient of VOCs. The partition coefficient of VOCs was not simply inversely proportional to the vapor pressure of the compound, but also increased with the increase of Henry's law constant.
AB - Most building materials are porous media. As a critical environmental factor, the influence of relative humidity on VOCs diffusion is still not well understood. In this study, VOC transport and sorption in a porous medium in the building materials (calcium silicate) were measured under three levels of relative humidity (25%, 50% and 80%) by using a dynamic dual chamber method. Tests were conducted for water-soluble compound (formaldehyde) and non-soluble compound (toluene). In addition, the transport of acetaldehyde, hexanal, benzaldehyde, butanol and decane through the calcium silicate were also tested at 50%RH to study the relationship between the effective diffusion coefficient (De), partition coefficient (Kma) and the VOCs' physical properties (molecular weight, vapor pressure and Henry's law constant). Experimental results showed that: relative humidity in the 80%RH led to a higher partition coefficient for formaldehyde compared to 50%RH. However, between 25% and 50%RH, there was no significant difference in partition coefficient. Partition coefficient of toluene decreased with the increase of humidity due to competition of water molecules for pore surface area and the non-solubility nature of toluene. Relative humidity had no significant influence on the effective diffusion coefficient on both formaldehyde and toluene for the range of moisture conditions tested. The solubility of VOCs was found to correlate with the partition coefficient of VOCs. The partition coefficient of VOCs was not simply inversely proportional to the vapor pressure of the compound, but also increased with the increase of Henry's law constant.
KW - Dynamic dual chamber
KW - Henry's law constant
KW - Partition coefficient
KW - Relative humidity
KW - VOCs diffusion
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U2 - 10.1016/j.buildenv.2011.02.007
DO - 10.1016/j.buildenv.2011.02.007
M3 - Article
AN - SCOPUS:79954680211
SN - 0360-1323
VL - 46
SP - 1785
EP - 1796
JO - Building and Environment
JF - Building and Environment
IS - 9
ER -