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Micellar effects on luminescense of organic compounds or probes are well established, and here we show that quenching is highly favored in aqueous sodium dodecyl sulfate (SDS) micelles, which concentrate a naphthalene probe and cations of lanthanides, transition metals, and noble metals. Interactions have been studied by steady state and time-resolved fluorescence in examining the fluorescence suppression of naphthalene by metal ions in anionic SDS micelles. The quenching is collisional and correlated with the unit charge and the reduction potential of the metal ion. The rate constants, calculated in terms of local metal ion concentrations, are close to the diffusion control limit in the interior of SDS micelles, where the microscopic viscosity decreases the transfer rate, following the Stokes-Einstein relation.

The adsorption isotherms of Mg 2+ on γ-alumina follow a typical Langmuir model, characteristic of single layer adsorption, and experimental data fitting is successfully described by a two-layer electrostatic model (DLM) on discrete sites on the surface with variable charge as a function of pH. Speciation studies indicate that Mg 2+ was the major adsorbed species and the results show how chemical composition and species distribution in clay surfaces couples to solution properties such as pH and ionic strength to regulate adsorption and desorption processes in the distribution of Mg 2+ species between sediment and the aqueous phase. Probably the mechanism of adsorption of Mg 2+ at the γ-alumina surface is predominantly electrostatic, with outer sphere complexation, and the Mg 2+ -saturated γ-Al 2 O 3 surface efficiently promotes hydrolysis of phosphate diesters.