title: Sorption behavior of carbon nanotubes: changes induced by functionalization, sonication and natural organic matter.
abstract: The effect of functionalization on the sorption behavior of carbon nanotubes (CNTs) remains poorly understood, especially when combined with other factors affecting dispersion. The sorption behavior of a series of functionalized CNTs towards pyrene has therefore been systematically evaluated over a wide range of concentrations and dispersion scenarios. When studied as purchased (in the absence of humic acids and sonication treatment), sorption isotherms showed that OH-, COOH- and NH2-CNTs exhibited significantly different sorption affinity for pyrene. Sonication greatly increased both the sorption affinity and the maximum capacity of all types of functionalized CNTs, to an extent that overwhelmed the differences initially observed (increase of up to 1.5 orders of magnitude lead to log Kd values close to 9 L/kg). Results demonstrate that a significant proportion of the CNT surface was unavailable to pyrene prior to sonication. The presence of humic acids enhanced dispersion but decreased sorption, especially when combined with sonication. Sorption affinity, however, remained very high in all cases (log Kd>7.5 L/kg), suggesting that CNTs can act as strong sorbents under a wide range of conditions.
authors.affiliation: Department of Environmental Geosciences, University of Vienna, Althanstrasse 14, Vienna 1090, Austria. Electronic address: melanie.kah@univie.ac.at.
authors.forename: Melanie
authors.initials: M
authors.lastname: Kah
authors.affiliation: Department of Environmental Geosciences, University of Vienna, Althanstrasse 14, Vienna 1090, Austria; School of Environment and Energy Engineering, Key Laboratory of Urban Stormwater System and Water Environment, Ministry of Education, Beijing University of Civil Engineering and Architecture, Zhanlanguan Road 1, Xicheng District, Beijing, 100044, China.
authors.forename: Xiaoran
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Environmental Geosciences, University of Vienna, Althanstrasse 14, Vienna 1090, Austria. Electronic address: thilo.hofmann@univie.ac.at.
authors.forename: Thilo
authors.initials: T
authors.lastname: Hofmann
keywords: Adsorption; Dispersion; Humic acid; PAH; Passive sampling; Pyrene