Date of Award

Spring 1988

Project Type

Dissertation

Program or Major

Chemistry

Degree Name

Doctor of Philosophy

First Advisor

C L Grant

Abstract

Sorption is the basis for a number of techniques used to characterize solid particles. Because a number of techniques are based on sorptive interactions which are not fully understood, they are often plagued by experimental inconsistencies that are difficult to explain and frequently ignored. The purpose of this dissertation is to examine two techniques that are complicated by experimental inconsistencies--surface area measurements and the determination of distribution coefficients.

The apparent surface area of illite was measured by adsorption of a cationin fluorescent dye, Pyronin-y, from aqueous solutions in which pH and ionic strength were systematically varied. Estimates were highly dependent on pH, while ionic strength effects depended on the composition and pH of the buffer solutions. A complete lack of sorption of the anionic dye, New Coccine, to illite was also observed. Results indicated that the interactions between illite and dyes were primarily electrostatic.

Variations in experimental procedures frequently result in a wide range of distribution coefficients measured for a single compound. Distribution coefficients have been reported to vary inversely with the solid-to-solution ratio used to measure coefficients. One explanation attributes this effect to the production of microparticulates during batch equilibration and the subsequent inability to separate these particles from the aqueous phase. A mathematical model was developed which highlights the effect microparticulates can have on the measurement of distribution coefficients when different methods of analysis are used. Distribution coefficients measured using the counting of radiolabelled analytes will be underestimated and can vary significantly with sediment concentration. Distribution coefficients measured by fluorescence quenching will be overestimated and will only be slightly influenced by sediment concentration. These predictions were supported on a qualitative basis by distribution coefficients measured for the sorption of anthracene to sediment using radiolabelling and fluorescence quenching techniques. To further evaluate this theory, the effect of equilibration time, type of agitation, sediment concentration and separation efficiency on the production of microparticulates during a batch equilibration experiment were studied. Based on total organic carbon concentration and conductivity measurements for the aqueous phase, sediment concentration was found to be the only variable which significantly influenced the production of microparticulates.

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