Surface-associated metal catalyst enhances the sorption of perfluorooctanoic acid to multi-walled carbon nanotubes

Li, C. and Schaffer, A. and Séquaris, J-M. and László, Krisztina and Tóth, A. and Tombácz, E. and Vereecken, H. and Ji, R. and Klumpp, E. (2012) Surface-associated metal catalyst enhances the sorption of perfluorooctanoic acid to multi-walled carbon nanotubes. JOURNAL OF COLLOID AND INTERFACE SCIENCE, 377. pp. 342-346. ISSN 0021-9797

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Abstract

Perfluorooctanoic acid (PFOA) sorption behaviour of two commercial multi-walled carbon nanotubes (MWCNTs) (C 150 P from Bayer MaterialScience: BA and C-MWNTs from NanoTechLabs Inc.: CP) was investigated from aqueous solution. The BA nanotubes contain Co/Mn/Mg/Al catalysts both on their outer surface and in the inner bore while CP contains Fe-based catalyst typically within the tubes. The adsorption isotherms of 14C-radiolabeled PFOA were measured by batch experiments and fitted to the Freundlich model (r20.92).. The adsorption affinity and capacity on BA were significantly higher than on CP. Increasing the pH reduced the adsorption of PFOA due to the electrostatic interaction between the pH-sensitive surface and the adsorbate. Increasing NaCl concentration lead to the aggregation of the MWCNTs reducing the available surface and thus the adsorption capacity. Removal of the catalyst from the outer surface of BA changed the electrophoretic mobility from positive to negative value also decreasing the adsorbed amount of PFOA. The surface charge of the surface-associated metal catalyst favors the electrostatic sorption of PFOA. Such surface modification may be a promising way to improve the sorption capacity of MWCNTs for pollutants like PFOA and to broaden their potential application in water purification.

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