Adhesion of Colloidal Hematite onto Mercury in Water-Ethanol Media

The adherence of hematite (alpha-Fe(2)O(3)) particles onto mercury electrodes in water-ethanol mixtures has been studied by counting on optical microscope images, obtaining also the effective charge by electrophoretic measurements. The number of attached particles, when the ethanol content is small, decreases as the ethanol concentration increases. At an ethanol mole fraction near 0.2, the number of particles goes through a minimum and then increases with ethanol concentration. When the electrode potential is modified, curves of the number of particles vs ethanol mole fraction with the same shape are found, but they cross each other. The experimental behavior can be explained based on the dependence of particle/solution, metal/solution, and metal/particle interaction energies on the solvent composition. Copyright 1999 Academic Press.