ORGANIC COSOLVENT EFFECTS OR SORPTION EQUILIBRIUM AT HYDROPHOBIC ORGANIC-CHEMICALS BY ORGANOCLAYS

Isotherms were measured for sorption of naphthalene and diuron by four organoclays in equilibrium with various mixtures of methanol and wate r. The organoclays were prepared from Wyoming montmorillonite by repla cing the natural exchangeable cations of the day by the quaternary amm onium ions TMA (tetramethylammonium), TMPA (trimethylphenylammonium), HDTMA (hexadecyltrimethylammonium), and BDTDA (benzyldimethyltetradecy lammonium). TMPA-clay showed the greatest sorptive capacity for naphth alene, while BDTDA-clay was the most effective sorbent for diuron. The sorption mechanism for each sorbate-sorbent combination was related t o the arrangement of the quaternary ammonium cations in the exchanged clay acid the volume fraction of methanol in solution (f(c)). As expec ted from the solvophobic theory, the linear sorption coefficients decr eased loglinearly with increasing f(c) in the binary solvent mixture, except for TMPA-clay at f(c) > 0.5. In addition to solute-solvent and solvent-sorbent interactions, an additional effect involving solute-or ganoclay interactions influenced the sorption of naphthalene and diuro n by organoclays from aqueous and mixed solvents.