Physical Properties of Hanford Transuranic Waste Sludge

Berg, John C.

University of Washington, Seattle, WA

关键词: Trade;    Sludges;    54 Environmental Sciences;    Electrostatics;    Mixtures;   

DOI  :  10.2172/893354
RP-ID  :  EMSP-90162-2005
RP-ID  :  FG02-04ER63796
RP-ID  :  893354

美国|英语

来源: UNT Digital Library

【 摘 要 】

Equipment that was purchased in the abbreviated year 1 of this project has been used during year 2 to study the fundamental behavior of materials that simulate the behavior of the Hanford transuranic waste sludge. Two significant results have been found, and each has been submitted for publication. Both studies found non-DLVO behavior in simulant systems. These separate but related studies were performed concurrently. It was previously shown in Rassat et al.'s report Physical and Liquid Chemical Simulant Formulations for Transuranic Wastes in Hanford Single-Shell Tanks that colloidal clays behave similarly to transuranic waste sludge (PNNL-14333, National Technical Information Service, U.S. Dept. of Commerce). Rassat et al. also discussed the pH and salt content of actual waste materials. It was shown that these materials exist at high pHs, generally above 10, and at high salt content, approximately 1.5 M from a mixture of different salts. A type of clay commonly studied, due to its uniformity, is a synthetic hectorite, Laponite. Therefore the work performed over the course of the last year was done mainly using suspensions of Laponite at high pH and involving high salt concentrations. One study was titled ''Relating Clay Rheology to Colloidal Parameters''. It has been submitted to the Journal of Colloid and INterface Science and is currently in the review process. The idea was to gain the ability to use measurable quantities to predict the flow behavior of clay systems, which should be similar to transuranic waste sludge. Leong et al. had previously shown that the yield stress of colloidal slurries of titania and alumina could be predicted, given the measurement of the accessible parameter zeta potential (Leong YK et al. J Chem Soc Faraday Trans, 19 (1993) 2473). Colloidal clays have a fundamentally different morphology and surface charge distribution than the spheroidal, uniformly charged colloids previously studied. This study was therefore performed in order to determine the applicability of the previous findings to the systems of interest. The yield stress of clay slurries was measured using the Physica MCR 300 purchased in year 1 of this project. The zeta potential of these systems was then measured using the Brookhaven Zeta PALS, also purchased in year 1. These two parameters were then plotted and compared with the Leong result. It was found that this system behaved in a non-DLVO manner. Leong found that colloidal slurry yield stress decreases with increased zeta potential which is consistent with the DLVO theory's assertion that particle attractions decrease as their electrostatic repulsion increases. Clay systems, however, show an increase in yield stress as zeta potential is increased. This is due to the nature of the charge distribution on the surface of clay particles. Clay particles are in the form of platelets.