Mk. Eberhardt et al., FORMATION OF HYDROXYL RADICALS AND CO3-EDTA WITH HYDROGEN-PEROXIDE - CATALYTIC EFFECT OF FE3+( IN THE REACTION OF CO2+), Biochimica et biophysica acta, 1157(1), 1993, pp. 102-106
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.