The rheology of oxide dispersions and the role of concentrated electrolyte solutions

Biggs, Simon and Tindley, Amy (2009). The rheology of oxide dispersions and the role of concentrated electrolyte solutions. In: ICEM2007: Proceedings of the 11th International Conference On Environmental Remediation and Radioactive Waste Management, Pts A and B. 11th International Conference on Environmental Remediation and Radioactive Waste Management, Bruges Belgium, (249-254). Sep 02-06, 2007. doi:10.1115/ICEM2007-7010


Author Biggs, Simon
Tindley, Amy
Title of paper The rheology of oxide dispersions and the role of concentrated electrolyte solutions
Conference name 11th International Conference on Environmental Remediation and Radioactive Waste Management
Conference location Bruges Belgium
Conference dates Sep 02-06, 2007
Proceedings title ICEM2007: Proceedings of the 11th International Conference On Environmental Remediation and Radioactive Waste Management, Pts A and B
Publisher ASME
Publication Year 2009
Sub-type Fully published paper
DOI 10.1115/ICEM2007-7010
Open Access Status
ISBN 978-0-7918-4339-0
0-7918-3818-8
Start page 249
End page 254
Total pages 6
Language eng
Formatted Abstract/Summary
Stability control of particulate dispersions is critical to a wide range of industrial processes. In the UK nuclear industry, significant volumes of waste materials arising from the corrosion products of Magnox fuel rods currently require treatment and storage. The majority of this waste is present as aqueous dispersions of oxide particulates. Treatment of these dispersions will require a variety of unit operations including mobilisation, transport and solid-liquid separation. Typically these processes must operate across a narrow optimal range of pH and the dispersions are, almost without exception, found in complex electrolyte conditions of high overall concentration. Knowledge of the behaviour of oxides in various electrolyte conditions and over a large pH range is essential for the efficient design and control of any waste processing approach. The transport properties of particle dispersions are characterised by the rheological properties. It is well known that particle dispersion rheology is strongly influenced by particle-particle interaction forces, and that particle-particle interactions are strongly influenced by adsorbed ions on the particle surfaces. Here we correlate measurements of the shear yield stress and the particle zeta potentials to provide insight as to the role of ions in moderating particle interactions. The zeta potential of model TiO2 suspensions were determined (Colloidal Dynamics ZetaProbe) over a range of pH for a series of alkali metal halides and quaternary ammonium halides at a range of solution concentrations (0.001M–1M). The results show some surprising co-ion effects at high electrolyte concentrations (>0.5M) and indicate that even ions generally considered to be indifferent induce a shift in iso-electric point (i.e.p.) which is inferred as being due to specific adsorption of ions. The shear yield stress values of concentrated titania dispersions were measured using a Bohlin C-VOR stress controlled rheometer. The shear yield stress of a material is defined as the minimum applied shear stress required to induce flow. The yield stress vs. pH curves obtained reflected the shifts in i.e.p. seen in the zeta potential results. Interestingly, specific ion adsorption results in an unexplained increase in the value of the yield stress over that expected for simple systems with no such interfacial ion adsorption. Possible reasons for this effect such as ion-ion correlation effects are discussed. The importance of this increased attraction for the mobilisation of settled solids in an aqueous environment and especially the likely effects on the treatment of Magnox fuel waste materials is discussed.
Keyword Rheology
Zeta potential
Yield stress
Specific ion effects
Suspensions
Q-Index Code E1
Q-Index Status Provisional Code
Institutional Status Non-UQ

 
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