Adsorption and coadsorption of ionic surfactants, inorganic ions, and nonionic solutes on quartz and corundum: Computer models

The adsorption behavior of compounds in real (i.e., chemically complex) systems may be quite different from the behavior of the same compounds in idealized model systems. The presence of a particular species can alter the behavior of another by forming complexes which adsorb strongly (thereby increasing the adsorption of one or both species), by forming strong complexes which are non-adsorbing, or by competing for surface sites. To understand natural systems, adsorption must be understood under both simple and interacting conditions.;I have investigated the simultaneous adsorption of multiple interacting organic and inorganic species on oxide surfaces as a function of concentration, pH, and electrolyte concentration with the aid of the triple layer adsorption mode of the chemical speciation model HYDRAQL. This research has included the development of both conceptual and numerical models describing four modes of adsorption on simple oxide surfaces in the presence of a background electrolyte: (1) the adsorption of straight chained monofunctional surfactants; (2) the modifying influence of divalent cations on anionic surfactant adsorption; (3) the subsequent adsorption of nonionic organic compounds on surfaces with ionic surfactants adsorbed, and (4) demonstration of the ability to simulate a complex system including divalent cations, ionic surfactants, and nonionic organic compounds. A consistent description of surface ionization and electrolyte binding was also developed.;Representative model systems, with available experimental data, have been selected for each of these adsorption modes. Each system chosen is a subset of the most complex behavior to be modeled. Each simplified sub-system has been modeled independently. The resulting reactions and parameters have then been used without alteration in the modeling of progressively more complex systems.