EFFECT OF THE ZETA-POTENTIAL ON ELECTRON-TRANSFER TO COLLOIDAL IRON-OXIDES

The reaction rate between charged, reducing radicals and highly charged, colloidal oxide particles is shown to be strongly dependent on the f potential of the particles. An equation is developed which ncorporates the influence of the electric field present around colloidal oxides on both mass-transferlimited and activation-controlled electron-transfer reactions at the colloid surface. It is shown that appreciable kinetic effects are possible under typical experimental conditions. By use of a Stern model for the oxide-water interface, an inner layer capacitance of 400, 30 μF cm-2 for iron oxide is obtained. © 1990, American Chemical Society. All rights reserved.