Quantification of the adsorption of phenolic compounds on the geotextile and bentonite components of four geosynthetic clay liners

Abstract

ABSTRACT: The aim of this paper is to present the experimental results obtained regarding the adsorption on various constitutive geotextiles and bentonites of geosynthetic clay liners of phenol, o-cresol, p-cresol, 2-chlorophenol, 4-chlorophenol, 2,4-dimethylphenol, 3,4-dimethylphenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, 2,3,5,6-tetrachlorophenol, pentachlorophenol, and bisphenol A. These contaminants, including certain derivatives of halogenated phenols, are known to be toxic even at very low concentrations. Geotextiles and bentonites were sampled from four geosynthetic clay liners (GCLs) representative of the GCLs commonly used in bottom liner systems in France. Adsorption was studied through batch adsorption tests. The effect of the nature of the bentonite (sodium versus calcium activated) was studied. Results obtained in this study show that, contrary to what has been observed for volatile organic compounds (VOCs), the adsorption isotherms are non-linear. For VOCs, linear adsorption isotherms are obtained both for geotextiles and for bentonites. The contrast between the adsorption on geotextiles and bentonites is smaller than for VOCs. Up to two orders of magnitude difference can be obtained between the low adsorption coefficient for bentonite as compared with the large adsorption coefficient for geotextiles when adsorption of VOCs is considered. For phenolic compounds, the adsorption coefficients are of the same order of magnitude for bentonite and geotextiles. Two different trends were observed for woven and nonwoven needle-punched geotextiles as regards the adsorption parameters measured. For chlorophenols, polarity appears to affect adsorption: the adsorption coefficients increased with increasing number of chlorine atoms.