Charge trapping in the reductive dissolution of colloidal suspensions of iron(III) oxides

Abstract

Reduction of suspensions of α-Fe2O3, α-FeOOH, and transparent a-Fe2O3 sols by viologen radicals has been studied by using steady-state radiolysis to generate the radicals. The yield of Fe2+ at pH >2.5 is substantially lower than the yield expected from the complete transfer of electrons to the particles. Adsorption isotherms for Fe2+ on these colloids indicate that adsorption of the reduced iron can only account for a small fraction of the reduction yields obtained. This observation, as well as measurements of the amounts of Fe2+ that can be removed from the surface after the reduction, leads to the conclusion that a substantial fraction of the electrons transferred to the colloid is able to..