Koi Ling Lim

Date of Award

12-2006

Degree Name

Master of Science

Department

Geological and Environmental Sciences

Department

Geosciences

First Advisor

Dr. Johnson R. Haas

Second Advisor

Dr. Carla Koretsky

Third Advisor

Dr. Alan Kehew

Access Setting

Masters Thesis-Open Access

Abstract

Wastes and pollution containing uranium are released to the environment through mining, ore processing, industrial manufacture of nuclear fuel and weapons materials, and the disposal of spent nuclear fuel. There are a wide variety of processes that can affect UO2 stability. This research focuses on the surface reactivity of UO2 in reducing aqueous solutions, with an emphasis on assessment of the pH-dependent surface charge, reactive surface area, and the adsorption of dissolved lead (Pb), cadmium (Cd), lanthanum (La) onto UO2 particles. A surface complexation model was used to explain the adsorption and titration phenomena of UO2. Our results show that UO2 has two major surface sites, an amphoteric site and an acidic site, which are responsible for the release and uptake of protons. The N2-BET specific surface area of UO2 was measured at 3.505 m2/g. Pb exhibits strong adsorption onto UO2, followed by La and Cd. Pb and La adsorptions are independent of ionic strength indicating that they probably form inner-sphere complexes at the surface. Cd adsorption decreases with increasing ionic strength, which is a typical phenomenon of outer-sphere complexes.

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