Photodissolution of Iron Oxides III: The Interplay of Photochemical and Thermal Processes in Maghemite/Carboxylic acid Systems

M.I. LITTER; E.C. BAUMGARTNER; G.A. URRUTIA; M.A. BLESA

ENVIRONMENTAL SCIENCE & TECHNOLOGY

AMER CHEMICAL SOC

Lugar: Washington; Año: 1991 vol. 25 p. 1907 - 1913

0013-936X

Irradiation of y-Fe203 suspensions in the presence of oxalate and EDTA results in a complex interplay between photochemical and thermal electron-transfer reactions. In the thermal dissolution, surface >Fe"´-L complexes are slowly transferred by acid and reductive pathways until Fe´LL buildup in solution produces a strong acceleration. Irradiation accelerates the reaction by producing Fe2+, heterogeneously by photolysis of the oxide surface complexes, and by homogeneous photolysis of aqueous FemL. This latter process is responsible for the acceleration in photodissolution rates brought about by the addition of Fe3+8q: Experimental results are reasonably fitted by the analytical solution of the simplified set of kinetic equations.