DYNAMICS OF LIGHT-INDUCED EXCITED-STATE QUENCHING OF FERRIOXALATE COMPLEXES BY PEROXIDES - FAST KINETIC EVENTS AND INTERACTION WITH TOXIC POLLUTANTS

The behaviour of the trioxaloferrate (Fe(ox)(3)(3-)) complex on laser illumination and its quenching in the presence of H2O2 were investigat ed by laser photolysis. At neutral Ph, a short (approximately 30 mu s) sind a longer (approximately 1 ms) lifetime were observed for transie nt Fe(ox)(3)(3-). The lifetime decreases as the pH becomes more acidic . In light-induced processes, the intensity of the light used is one o f the determining reaction parameters and this effect is reported in d etail. The excited states of the Fe oxalate complexes induced by laser photolysis are quenched by H2O2. The decay observed can be fitted in a simplified way by a bi-exponential function. The transient species F e(ox)(3)(3-) observed on laser photolysis does not undergo excited st ate annihilation, but ground state collisional quenching. The fast for mation of a hydroxylated phenol adduct is shown by kinetic laser spect roscopy. A detailed account of the kinetics and spectral characteristi cs of the transients is presented for these reactions. This allows a s cheme to be suggested for the intervention of these radicals in agreem ent with the experimental observations. The results obtained implicate the (OH)-O-. radical in the degradation of pollutants involving Fe co mplexes in the presence of H2O2.