School of Civil and Environmental Engineering

Ph.D. Thesis Defense Announcement

Complex Adsorption Modeling for Nuclear Energy Applications

By

Austin P. Ladshaw

Advisors:

Dr. Sotira Yiacoumi (CEE)

Committee Members:

Dr. Costas Tsouris (CEE, ORNL), Dr. Spyros G. Pavlostathis (CEE),
Dr. James Mulholland (CEE), Dr. David Sherrill (CHEM)

Date & Time: Monday, April 3rd, 2017 at 11:00 AM

Location: Sustainable Education Building  Conference Room 122

ABSTRACT

Adsorption is a complex physical-chemical phenomenon by which molecules are

attached to surfaces of solid particles. The type of adsorption that occurs may often

depend on the media the phenomenon is occurring in, making the design of models for

various adsorption systems an arduous task. Regardless of the media, however, the basic

mechanisms of the adsorption process are the same. Therefore, a plausible approach to

the development of adsorption models in different systems would be to design a

generalized mathematical framework with all the necessary methods built in that will be

used as a platform to develop system specific adsorption models. In this work, the

investigation and development of such a structure will be discussed and a host of system

specific adsorption models that have been developed on top of that framework will be

detailed. The applications of interest are all related to nuclear energy and specifically the

availability of uranium in the Nuclear Fuel Cycle via recycling spent uranium fuel rods

and capturing new raw uranium from seawater. In recycling spent uranium, the

reprocessing procedure produces numerous gas pollutants that must be removed from the

off-gases before emission to the atmosphere. To facilitate the design of that capture

system, adsorption models have been developed to predict isothermal equilibria of

complex gas mixtures and to quantify the rates of adsorption for various adsorbent

materials. For recovering uranium from seawater, two different models were produced:

(i) a predictive, multi-ligand adsorption model to incorporate effects of pH, ionic

strength, and competing metals and (ii) an analytical model to quantify the impact of

current velocity on the mass transfer limitations of braided fiber adsorbents. The

culmination of these adsorption models will provide tools for scientists and engineers to

better understand adsorption phenomena in the applications of interest and subsequently

design the necessary capture systems at both the front and back ends of the Nuclear Fuel

Cycle.