Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Lindner, Jeffery

Committee Member

Toghiani, Rebecca

Committee Member

Hill, Priscilla

Date of Degree

8-11-2007

Original embargo terms

MSU Only Indefinitely

Document Type

Graduate Thesis - Campus Access Only

Major

Chemical Engineering

Degree Name

Master of Science

College

James Worth Bagley College of Engineering

Department

Dave C. Swalm School of Chemical Engineering

Abstract

The 53 million gallons (240,000 tons) of nuclear waste stored at the Hanford site comprises approximately 60% of the nation¡¯s legacy nuclear waste. Previously, processing of the saltcake phases of tank wastes dominated disposal efforts at Hanford. Interest is now being directed at the processing and pretreatment of the sludge phases of the waste. These sludges, consisting of complex combinations of insoluble metal compounds, present many challenges. This thesis deals with experimentation pertaining primarily to aluminum chemistry and the role it plays in pretreatment of Hanford waste sludge. Included is a statistical analysis of an inventory of components within Hanford tanks. A recipe was followed to produce a simulant sludge for further experimentation. The solubility of the aluminum species, gibbsite, thought to be the most common aluminum species in the Hanford tanks, was studied. In addition, the reaction by which gibbsite is transformed to a much less soluble phase, boehmite, was studied in depth. Gibbsite¡¯s transformation to boehmite begins at about 200 ¡ÆC, a temperature higher than that seen by Hanford tanks. However, recent literature suggests that it may be converted to boehmite at lower temperatures. A study of the rate of boehmite formation at temperatures ranging from 80 to 150 ¡ÆC using caustic concentrations of 1.5, 3, and 5 molal is reported. In such a way, the effects of both temperature and caustic loading on the rate of boehmite formation were sought. It was determined that boehmite formed readily at temperatures 120 ¡ÆC and higher. These data supplement existing aluminum chemistry knowledge and will increase the efficiency with which sludge pretreatment and disposal procedures are designed.

URI

https://hdl.handle.net/11668/16364

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