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Investigation on the Adsorption Features of Humic Acid on Carbon Nanotubes  

Lee, Sun-Hwa (Dept. of Environmental Science and Engineering Ewha Womans University)
Kim, Dong-Su (Dept. of Environmental Science and Engineering Ewha Womans University)
Publication Information
Journal of Korean Society on Water Environment / v.20, no.5, 2004 , pp. 520-524 More about this Journal
Abstract
As a feasibility study for the application of carbon nanotubes to the treatment of environmental pollutants, the adsorption characteristics of humic acid on carbon nanotubes has been investigated. The dispersion features of carbon nanotubes in aquatic environment were investigated by measuring the variation of their electrokinetic potentials with pH, and the effects of some dispersants on their dispersion features were also examined. Under the experimental conditions, humic acid was observed to mostly adsorb on nanotubes within a few minutes and reach the equilibrium state within about one hour. The adsorption features of humic acid on nanotubes were found to follow the Freundlich model better than the Langmuir Model. Humic acid adsorbed on carbon nanotubes endothermically and the change of enthalpy in adsorption reaction was estimated to be ca. 18.37kJ/mol at standard state. The entropic change in adsorption reaction for humic acid was ca. 0.0503kJ/mol at standard state and the activation energy for adsorption was also estimated based on the change of rate constants with temperature. FT-IR investigations showed that the functional groups such as alcohol, ester, and aromatics existing in the chemical structure of humic acid might work as the bridge in its adsorption on nanotubes.
Keywords
Humic acid; Carbon nanotubes; Adsorption; Dispersion; Kinetics;
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