Applied Kinetics Aspects of Ferric EDTA Complex Reduction with Metal Powder

Abstract

Nitrogen and sulfur oxides (NOx and SOx) emitted from fossil-fuel-fired facilities can be simultaneously absorbed into aqueous mixed solutions of sulfite and FeIIL, a ferrous ion coordinated to a ligand L (a chelate compound). Usually, the ligand L represents an anion of ethylenediaminetetraacetic acid (EDTA or edta). Nitrogen oxide (NO) sparingly soluble in water is promptly bound to the [FeII(edta)(H2O)]2– complex to form the [FeII(edta)(NO]2–compound. However, [FeII(edta)(H2O]2– chelate is oxidized to form [FeIII(edta)(H2O)]− by NO, NO2, and O2, normally coexisting in flue gases. Because the ferric complex does not react with NO, the suppression of these undesired oxidation processes is a very important technological problem to be overcome. Thus, in this work, the reduction kinetics of ferric ion by metal was discussed on the basis of the kinetic data regarding the ferric ion reduction in aqueous solutions of [FeIII(edta)(H2O)]− containing such pulverized metals as aluminum, tin, and zinc. The rate exp...