Fotobranqueamento de polpas celulósicas: estudo fotofísico e fotoquímico de modelos de lignina

Abstract

Three conditions of photobleaching were applied to study the behavior of some biphenylic and β-0-4 lignin models aiming to understand the photobleaching of cellulosic pulps and the photoyellowing of bleached pulps. The products were identifíed and some photophysical aspects associated to this were studied. The content of phenolic hydroxyl groups was quantified during the photolysis of β-0-4 models. Kinetics of degradation the biphenyl compounds were obtained based on the variations in fluorescence intensity of each model. The increase of the fluorescence intensity, associated to the brightnees index (BI), was correlated to the absence of oxidized structures and by another side the photoyellowing of the paper was associated to the increase in concentration of theses structures. The intermolecular fluorescence quenching of the reduced biphenylic model by the oxidized biphenyl model was obtained by a Stem - Volmer plots. These results show an efficient probably static quenching.