The results of the heterogeneous photocatalytic reduction of Fe(VI) in UV-irradiated TiO2 suspensions
are presented and suggest indirect observation of the formation of Fe(V) by the photoreduction
of Fe(VI) with ecb− at TiO2 surfaces. Because Fe(V) selectively and rapidly oxidizes low reactivity pollutants
with the production of the non-toxic by-product, Fe(III), the photocatalytic reduction of Fe(VI) has a role in
pollution remediation processes. The experiments were conducted as a function of TiO2 suspension concentrations,
Fe(VI) concentrations, and pH in basic media. The initial rate of Fe(VI) reduction gave a fractional
order with respect to initial Fe(VI) concentrations and adheres to simple Langmuir-Hinshelwood kinetics.
Results suggest that the surface reaction (Fe(VI)+ecb−→Fe(V)) is the rate-controlling step. The photocatalytic
reduction of Fe(VI) in the presence of less reactive nitrogen-containing species (ammonia, cyanate,
and fulvic acid) were also investigated. Enhancement in the rate of Fe(VI) reduction was observed. A reaction
scheme involving Fe(V) as an intermediate is presented which explains the faster photocatalytic oxidation
of pollutants in the presence of Fe(VI).