Oxidation of EDTA with H2O2 catalysed by metallophthalocyanines.

The oxidation of ethylenediaminetetraacetic acid (EDTA) and Na, Ca, Zn, Fe, and Mn EDTA complexes with hydrogen peroxide was studied in aqueous solution with the use of several metallophthalocyanines (MePcS) as catalysts. The impact of pH, temperature, and catalyst/substrate ratio were investigated. The most effective catalytic system under neutral conditions was FePcS- H2O2. In these laboratory-scale experiments, a catalyst/substrate/H2O2 molar ratio of 4:100:2000 was found to be optimal, while the effective reaction temperature was 40-60 degrees C. When the impact of metal speciation was studied, metal-specific degradation rates in the removal of these compounds were observed: all EDTA-metal complexes except Zn-EDTA were efficiently oxidized within three hours. The most degradable species was Fe(III)-EDTA. Among the catalysts, FePcS was found to be the most active in EDTA degradation. Over 90% of EDTA was removed in the presence of FePcS as catalyst within three hours of reaction time.