PHYSICOCHEMICAL STUDIES IN ENVIRONMENTAL CHEMISTRY: NMR STUDIES AND MATHEMATICAL MODELING (MIXED MICELLES, ADSORPTION)

The purpose of this thesis is four-fold: (1) to investigate the adsorption of surfactants on floc surfaces by nuclear magnetic resonance spectroscopy, (2) to study the charge effects on the structure of mixed micelles, (3) to model the operation of aeration columns, and (4) to reduce numerical dispersion in the solution of two dimensional advection dispersion equation in cartesian coordinates.; Adsorption of linear alkyl chain surfactants on aluminum deuteroxide flocs has been studied by means of proton and carbon-13 NMR. Proton spin-lattice relaxation times (T(,1)) and carbon-13 spin-spin relaxation times (T(,2)) (estimated from the line-widths of carbon-13 signals) indicate that the surfactant ions adsorbed on aluminum deuteroxide flocs are more constrained in their motions than are micellar surfactant ions and that the binding to the floc is through the polar head group.; Solubilization of dodecanoic acid in three different micelles--sodium dodecyl sulfate (anionic), dodecyl trimethyl ammonium chloride (cationic) and Triton X-100 (nonionic) was studied by carbon-13 NMR. Chemical shifts, T(,1) and nuclear Overhauser enhancement (NOE) factors for the carboxyl carbon of dodecanoic acid indicate an apparent shift in the pK(,a) of dodecanoic acid in these micellar media. Anomalously large viscosities for solutions of Triton X-100 with a neutral second amphiphile (like dodecyl alcohol, dodecyl amine, dodecanoic acid etc.) indicate the formation of extended micelles, while the repulsive forces of the ionic head groups prevented the formation of these extended structures when the second amphiphile was ionized.; A mathematical model for the removal of volatile organics from water by aeration is developed. Mass transfer rate effects and increasing volume of the air bubbles as they rise through the column are taken into account.; The partial differential equation governing the movement of a decomposing pollutant undergoing two-dimensional flow in a saturated aquifer is solved numerically. Use of two asymmetrical upwind formulas to approximate the advection term markedly reduces numerical dispersion in cartesian coordinates. Flow within a right angle and flow toward a sink in an otherwise uniform field are analysed to illustrate the methods.