M. J. Angove, M. B. Fernandes, J. Ikhsan. (2002), 'The Sorption of Anthracene onto Goethite and Kaolinite in the Presence of Some Benzene Carboxylic Acids', Journal of Colloid and Interface Science, 247: p. 1 - 8.

ABSTRACT

The uptake of anthracene from dilute aqueous solution onto goethite and kaolinite was investigated at 25 o C, first in the absence and then in the presence of three benzene carboxylic acids: phtalic acid (benzene-1,2-dicarboxylic acid), trimesic acid (-1,3,5-), and mellitic acid (-1,2,3,4,5,6-). Carboxylic acid concentrations were 0.20, 0.10, and 0.05 mM. Anthracene (200 mM) did not adsorb strongly onto the pure mineral surfaces, but in the presence of phtalic acid a substancial increase in anthracene uptake was observed, particularly for the goethite systems. Trimetic and mellitic acids did not enhance anthracene uptake. Phtalate and proton adsorption data have been used to model phtalate adsorption onto the mineral surfaces using an extended constant capacitance surface complexation model. This model then succesfully adapted to account for the observed increase in the anthracene uptake, where anthracene molecule were assumed to interact with adsorbed phtalate. We propose that the enhancement of anthracene adsorption in the presence of phtalic acid is due to an increase in the hydrophobicity of the mineral surface once phtalic acid molecules adsorb. The same effect was not observed for the other benzene carboxylates because of their greater polarity.

Keywords: adsorption; anthracene; PAH; kaolinite; goethite; carboxylic acid; surface complexation; clays.