8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Wed 711:10-14:00P5.25Dielectric response in realistic salt-free concentratedsuspensions. Non-equilibrium dissociation-associationprocessesFelix Carrique, 1 Emilio Ruiz-Reina, 1 Francisco J. Arroyo, 2 and Angel V. Delgado 31 Universidad de Malaga, Dpto. Fisica Aplicada I, Fac. Ciencias, Universidad de Malaga29071, Malaga, Spain2 Universidad de Jaen, Jaen, Spain3 Universidad de Granada, Granada, SpainIn this work we study the dielectric relaxation processes that a realistic concentrated aqueoussalt-free suspension undergoes in the presence of an oscillating electric field (AC). A puresalt-free suspension is composed by charged particles and the ”added counterions” in solutionthat counterbalance the particle charge. However, a realistic aqueous salt-free suspension includesalso ionic species like those associated with water dissociation and those originated by possibleCO 2 contamination. The AC model in this work is based on a new double layer model forspherical particles in ”realistic” salt-free suspensions developed by the authors [1]. To account forparticle-particle electrohydrodynamic interactions we have used a cell model [2]. Also, realisticsalt-free suspensions require accounting for the chemical reactions in the solution. In the past anequilibrium scenario for chemical reactions was used by the authors to study the AC response [3]of these systems. We use in this contribution a more rigorous procedure based on non-equilibriumkinetic equations, according to the procedure developed by Baygents and Saville [4] for weakelectrolytes. The results confirm the large effects of water dissociation and CO 2 contaminationalong the frequency spectrum, but most remarkable, the existence of a low-frequency relaxationprocess of an alpha-type related to the relaxation of the concentration gradient of neutral species,that the equilibrium formalism did not capture. Acknowledgements: Junta de Andalucía, Spain(Project P08-FQM-3779) and MICINN, Spain (Project FIS2010-18972), co-financed with FEDERfunds by the EU.[1] Ruiz-Reina, E. ; Carrique, F. J. Phys. Chem. B 2008, 112, 11960.[2] Happel J. , S. , J. Appl. Phys. 1957, 28, 1288.[3] Carrique, F. ; Ruiz-Reina, E. ; Arroyo, F. J. ; Delgado, A. V. J. Phys. Chem. B 2010, 114,6134.[4] Baygents, J. C. ; Saville, D. A. J. Colloid Interface Sci. 1991, 146, 9.25