Organic cosolvent effects on sorption kinetics of hydrophobic organic chemicals by organoclays

Data obtained from batch kinetics sorption experiments for naphthalene and diuron using two organoclays [trimethylphenylammonium (TMPA)-clay and benzyldimethyltetradecylammonium (BDTDA)-clay] in aqueous and methanol-water systems were analyzed with a first-order one-site mass transfer model (OSMTM) to obtain kinetic parameters. The mass transfer coefficient (epsilon) exponentially decreased as the sorption coefficient (K-p) increased, and a log-linear increase in epsilon was observed with an increase in the volume fraction of cosolvent (f(c)) in the system. Regression equations relating epsilon to f(c), measured in mixed solvents, could be extrapolated to f(c) = 0 to obtain the coefficients in aqueous systems. The organic cosolvent effects on the sorption kinetics behavior of naphthalene and diuron depended on the sorbate structure, the cosolvent fraction, and the arrangement of the exchanged quaternary alkylammonium ions in montmorillonite-clay interlayers.