Photoinductive activity of humic acid fractions with the presence of Fe(III): The role of aromaticity and oxygen groups involved in fractions

Relationship between the photoinductive activity and the properties of humic acids (HA) fractions were investigated with and without Fe(III). Three fractions were separated based on the molecular weight (Mw) and were obtained following the order of Mw: FA > FB > FC. Compared to FA and FB, photodegradation of atrazine under simulated sunlight was much faster in solution containing FC, whose structure was dominated by greater aromaticity, more oxygen groups and fluorophores. The interaction of HA fractions and Fe(III) was studied using fluorescence spectrometry and FC had the largest quenching constant. The capacity of electron transfer, estimated from the amount of photoformed Fe(II), was also highest for FC. Thus, the Fe(III)–FC complex was efficient in phototransformation of atrazine in nearly neutral aqueous solutions. These results suggest that the aromaticity and oxygen groups content of HA exert great influence on the binding ability of metals and on the fate of pollutants in natural waters.