PHOTODISSOLUTION OF IRON-OXIDES IN MALONIC-ACID

The influence of 254-nm irradiation on the dissolution rate of magneti te (Fe3O4) and maghemite (gamma-Fe2O3) suspended in aqueous solutions of malonic acid is analyzed and compared with the dark reaction. The e ffect of the addition of Fe3+, reductants such as ascorbic acid and ox idants such as Ag+ or O-2 is described. Photochemical initiation invol ves the production of > Fe-II by electrons photogenerated on the oxide , which triggers thermal dissolution. Experimental results are fitted by analytical and numerical solutions of the set of kinetic equations. The calculated fitting parameters reflect the lower activity of iron oxides in malonic acid compared to EDTA media.