(217i) Stabilization and Control of Rheological Properties for Concentrated Colloidal Suspensions Under High Ionic Strength

Control of the stability and rheological properties of concentrated colloidal suspensions has been an important but challenging issue for various applications such as ceramic processing and nuclear waste treatment, one that fundamental science has yet to address fully. Rheological modifiers can be categorized into two types in terms of colloidal interaction implemented for enhancement of stability and rheological properties: electrostatic and steric interactions. Binding agents such as weak acids strengthen an electrostatic repulsion, whereas nonionic surfactants introduce a steric repulsion. We investigated various rheological modifiers on an iron oxide-rich nuclear waste simulant characterized by high ionic strength and high pH. From rheological analysis, it was found that citric acid is one of the best rheological modifiers for this simulant. Further analysis also supports that better stability is achieved by the addition of citric acid. This work is important to the waste treatment processing at Hanford and Savannah River sites, since controlling rheological properties enables us not only to increase the solids concentration in the process and reduce operational cost accordingly but also to ensure sustainable operations.