Adsorption of anionic dye and surfactant from water onto organomontmorillonite

Single- and bisolute competitive adsorptions were carried out to investigat e the adsorption behavior of an anionic dye, Orange II, and an anionic surf actant, dodecylbenzenesulfonate (DBS), from water at 25 degrees C onto mont morillonite treated with hexadecyltrimethylammonium (HDTMA) cation. The mon ovalent HDTMA cation was exchanged for the metal cations on the montmorillo nite to prepare HDTMA-montmorillonite, changing its surface property from h ydrophilic to organophilic. Adsorption affinity of DBS on HDTMA-montmorillo nite was found to be slightly higher than that of Orange II, probably due t o hydrophobic or nonpolar interactions between the long hydrocarbon chains of the HDTMA with an anion. The single-solute adsorption data were fitted t o the Langmuir and the Redlich-Peterson (RP) adsorption models. The competi tive Langmuir model and the ideal adsorbed solution theory (IAST) coupled w ith the single-solute adsorption models were used to predict the bisolute c ompetitive adsorption equilibria. Among the models, the IAST coupled with t he Langmuir and the RP models for DBS and Orange II, respectively, yielded the most favorable representation of the bisolute competitive adsorption be havior.