title: Understanding interactions in the adsorption of gaseous organic compounds to indoor materials.
abstract: We studied adsorption of organic compounds to a wide range of indoor materials, including plastics, gypsum board, carpet, and many others, under various relative humidity conditions by applying a conceptual model of the free energy of interfacial interactions of both van der Waals and Lewis acid-base (e-donor/acceptor) types. Data used for the analyses were partitioning coefficients of adsorbates between surface and gas phase obtained from three sources: our sorption experiments and two other published studies. Target organic compounds included apolars, monopolars, and bipolars. We established correlations of partitioning coefficients of adsorbates for a considered surface with the corresponding hexadecane/air partitioning coefficients of the adsorbates which are used as representative of a van der Waals descriptor instead of vapor pressure. The logarithmic adsorption coefficients of the apolars and weak bases, e.g., aliphatics and aromatics, to indoor materials linearly correlates well with the logarithmic hexadecane/air partitioning coefficients regardless of the surface polarity. The surface polarity in terms of e-donor/acceptor interactions becomes important for adsorption of the strong bases and bipolars, e.g., amines, phenols, and alcohols, to unpainted gypsum board. Under dry or humid conditions, the adsorption to flat plastic materials still linearly correlates well with the van der Waals interactions of the adsorbates, but no correlations were observed for the adsorption to fleecy or plush materials, e.g., carpet. Adsorption of highly bipolar compounds, e.g., phenol and isopropanol, is strongly affected by humidity, attributed to Lewis acid-base interactions with modified surfaces.
authors.affiliation: Faculty of Engineering, Mahasarakham University, Kantarawichai, Mahasarakham, 44150, Thailand. maneerat.o@msu.ac.th.
authors.forename: Maneerat
authors.initials: M
authors.lastname: Ongwandee
authors.affiliation: Faculty of Engineering, Mahasarakham University, Kantarawichai, Mahasarakham, 44150, Thailand.
authors.forename: Thabtim
authors.initials: T
authors.lastname: Chatsuvan
authors.affiliation: International College, King Mongkut's Institute of Technology Ladkrabang, Ladkrabang, Bangkok, 10250, Thailand.
authors.forename: Wichitsawat
authors.initials: W
authors.lastname: Suksawas Na Ayudhya
authors.affiliation: Faculty of Engineering, Mahasarakham University, Kantarawichai, Mahasarakham, 44150, Thailand.
authors.forename: John
authors.initials: J
authors.lastname: Morris
mesh_terms: D000327:Adsorption; D016902:Air Pollution, Indoor; D000473:Alkanes; D002133:Calcium Sulfate; D005430:Floors and Floorcoverings; D005740:Gases; D006813:Humidity; D008422:Materials Testing; D009930:Organic Chemicals
chemical_list: D000473:Alkanes; D005740:Gases; D009930:Organic Chemicals; C007932:n-hexadecane; D002133:Calcium Sulfate
keywords: Hexadecane/air partitioning coefficient; Lewis acid-base interactions; Relative humidity; Total free energy of adsorption; Vapor pressure; van der Waals interactions