| Abstract
| - Isotherms were measured for sorption of naphthaleneand diuron by four organoclays in equilibrium withvarious mixtures of methanol and water. The organoclays were prepared from Wyoming montmorilloniteby replacing the natural exchangeable cations of theclay by the quaternary ammonium ions TMA (tetramethylammonium), TMPA (trimethylphenylammonium),HDTMA (hexadecyltrimethylammonium), and BDTDA(benzyldimethyltetradecylammonium). TMPA-clayshowed the greatest sorptive capacity for naphthalene,while BDTDA-clay was the most effective sorbentfor diuron. The sorption mechanism for each sorbate−sorbent combination was related to the arrangementof the quaternary ammonium cations in theexchanged clay and the volume fraction of methanolin solution (fc). As expected fromthe solvophobictheory, the linear sorption coefficients decreased log-linearly with increasing fc in the binarysolventmixture, except for TMPA-clay at fc>0.5. In additionto solute−solvent and solvent−sorbent interactions,an additional effect involving solute-organoclayinteractions influenced the sorption of naphthaleneand diuron by organoclays from aqueous and mixedsolvents.
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