pH-DEPENDENT SORPTIONS OF PHENOLIC COMPOUNDS ONTO MONTMORILLONITE MODIFIED WITH HEXADECYLTRIMETHYLAMMONIUM CATION

Abstract

Single-solute sorptions onto the organically modified montmorillonite were completed at 2 different pH conditions, 7 and 11.5, in a batch reactor to investigate the pH-dependent uptake of 2-chlorophenol (ChP), 3-cyanophenol (CyP), and 4-nitrophenol (NiP) dissolved in water at 25°C. During the preparation of HDTMA-clay, hexadecyltrimethylammonium (HDTMA) cation was exchanged for metal cations on the montmorillonite at the cation exchange capacity of the montmorillonite. During the process, the montmorillonite changed from having a hydrophilic to an organophilic surface. Experimental results show that the sorption affinity on HDTMA-clay was in the order of 2-ChP > 4-NiP > 3-CyP for the 2 pH conditions. The Langmuir and the Redlich-Peterson (RP) models were used to fit the single-solute sorption equilibria data graphically. The ideal adsorbed solution theory (IAST) coupled with a single-solute model (i.e., either Langmuir or RP model) was used to predict the multisolute competitive-sorption equilibria. Predictions from the IAST at each pH condition yielded favorable representations of multisolute competitive sorption of the phenolic compounds onto HDTMA-clay.

ACKNOWLEDGMENTS

This paper was supported by Kyungpook National University Research Fund, 1998, for which one of the authors (D. I. Song) expresses his gratitude. The authors would like to thank an anonymous reviewer who provided many excellent comments that improved the quality of the manuscript.