PHOTOGENERATION AND PHOTOSENSITIZING ACTION OF HUMIC SUBSTANCES IN THE PRESENCE OF RIBOFLAVIN. A KINETIC AND MECHANISTIC STUDY

PAJARES A.; BREGLIANI M.; MONTAÑA M. P.; AMAT-GUERRI F.; GARCÍA N. A.

Granada

Congreso; III JORNADAS IBÉRICAS DE FOTOQUÍMICA; 2011

Humic substances are mixtures of organic compounds abundant in terrestrial and aquatic systems, and humic acids (HAs) are the predominant compounds in these mixtures. The available evidence indicates that these substances should be generated through the oxidative natural degradation/photodegradation of polyphenolic materials by complex thermal and photochemical mechanisms. In order to advance in the study of these mechanisms, the present contribution discusses: (a) the kinetic and mechanistic aspects of the photoprocesses that operate in the photodegradation of gallic acid (GA) a polyphenol naturally formed after lignin degradation under conditions frequently found in nature, i.e. aqueous environment, visible-light illumination and sensitization with riboflavin (Rf, vitamin B2) a native photosensitizer present as traces in waters of rivers, lakes and seas [ ]; and (b) the photosensitizing properties of mixtures Rf + HAs in the photodegradation of phenolic water-contaminants, using phenol (PhOH) and 3-hydroxypyridine (3-OHP) as models. Both, Rf and HAs, have been considered to individually play important roles in the photochemical degradation of organic materials in nature.