Polydisperse Adsorption Characteristics of Aqueous Organic Matrices in Water and Wastewater Sources
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Polydisperse Adsorption Characteristics of Aqueous Organic Matrices in Water and Wastewater Sources FUSHENG LI∗ Water Environment Research Group, Public Works Research Institute, Tsukuba, Ibaraki 305-8516, Japan [email protected]
AKIRA YUASA River Basin Research Center, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan YOSHIHIKO MATSUI Department of Civil Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan EUN-JEONG CHEONG Graduate School of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
Abstract. Batch adsorption isotherms of fourteen dissolved organic matrices (DOMs) from river water, ground water, wastewater and commercial sources were measured using lumped quality indices of DOC and UV260, and analyzed using a distributed fictive component method. By accounting for the heterogeneity of DOM constituents with a log-normal distribution of Freundlich K , the adsorption equilibrium of each DOM was characterized by searching for only three parameters. Indicating strong adsorbability dependency upon the sources and types of DOMs, the distribution ranges of the Freundlich K differed markedly. Compared to a river water DOM that had a K range in 10.8–190 (mg/g)/(mg/l)1/n , a commercial humic acid was found most heterogeneous: K varied in 0.01–1494.3 (mg/g)/(mg/l)1/n . In addition, based upon chromatographic results measured using a HPSEC system for all DOMs before and after adsorption, preferential adsorption of small molecular weight constituents was revealed for commercial humic acids; for aquatic organic matrices, however, such a trend was not found. Keywords: NOM, humic matter, adsorption, molecular weight distribution, isotherm
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Introduction
Activated carbon adsorption applied for advanced water and wastewater treatment has to deal with two categories of organic adsorbates: macromolecular organic matrices and small synthetic organic compounds. Arising from the decay of plant and animal residues and other biological activities of microor∗ To
whom correspondence should be addressed.
ganisms, the macromolecular organic matrices consisted of mainly humic molecules and/or similar organic polyelectrolytes are highly polydisperse in their physicochemical features (including molecular size, functional group, charge density, aromaticity, etc.). Characterization of their composition in terms of adsorbabilities is important for better understanding their adsorption behavior. It is also central for modeling the adsorption equilibrium and kinetics of specially targeted trace organic compounds whose adsorption
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extent is markedly affected by coexisting organic macromolecules (Crittenden et al., 1993; Warta et al., 1995; Pelekani and Snoeyink, 1999; Ebie et al., 2001). Fictive component method (FCM), which involves a series of hypothetical components (HCs) and a competitive adsorption model, in many cases the ideal adsorbed solution theory (IAST), is an approach developed for description of the adsorption equilibrium of organic matrices with unknown composition (Fettig and
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