FORMATION OF HYDROXYL RADICALS AND CO3-EDTA WITH HYDROGEN-PEROXIDE - CATALYTIC EFFECT OF FE3+( IN THE REACTION OF CO2+)

Co2+ ions (Co(NO3)2.6H2O) react with H2O2 only in presence of EDTA to yield OH radicals and Co3+. This reaction was carried out in unbuffere d aqueous solutions (pH = 2.6). The formation of Co3+ was confirmed by spectroscopy. The Co3+-EDTA complex shows two typical absorptions at 382 nm and 532 nm. The Co3+-EDTA complex can be prepared by a number o f oxidixing agents, like Fe3+, Fe3+-EDTA, Ag+, Ag2+, Ce4+, and hydroxy l radicals. Since Fe3+ oxidizes Co2+-EDTA to Co3+-EDTA and Fe2+ we ini tiate a chain reaction for .OH formation. Our results show that there are two modes for H2O2 decomposition: (1) One electron transfer to giv e OH radicals and (2) Decomposition of H2O2 to H2O and O2 without inte rmediate .OH formation. This reaction depends strongly on the pH of th e buffer. The H2O2 decomposition increases with increasing pH and incr easing Co2+ concentration.