Characterization of triplet states of humic acids by laser flash-photolysis

MARTIN, MARCELA; GONZALEZ, MÓNICA; BORSARELLI, CLAUDIO; MÁRTIRE, DANIEL

Cubatão, São Paulo, Brazil

Congreso; IX ELAFOT; 2008

ELAFOT

Humic substances (HS) can act as photosensitizers and promote the degradation of organic pollutants in the environment. The time-resolved studies on the photolysis of HS are restricted. In this communication we investigate the spectral characteristics of the intermediate species formed by photolysis of humic acids in aqueous solution. The experiments were performed using the laser flash-photolysis technique (LFP). The excitation source was a Litron Nd:YAG laser (2 ns FWHM y 6 mJ per pulse at 266 nm). Previously purified commercial Aldrich humic acids (HA) were employed in the experiments. Traces were obtained with solutions of different pH values and saturated with Ar, air or oxygen. Since the system is complex, a bilinear regression program was used to analyze the minimum number of intermediate species involved in the decay traces. From the oxygen effect on the decay kinetics of the transients, these species are assigned to triplet states. The observed mechanism agrees with the T-T energy transfer proposed for humic acids.