Photocatalytic degradation of acid azo dyes in aqueous TiO 2 suspension I. The effect of substituents

Abstract

The effect of substituents on the photocatalytic degradation of H/K acid based azo dyes in aqueous solution is investigated. The intramolecular chemical environment can easily change the charge transfer direction of the conjugated pair on both sides of the trans-azobenzene backbone in o-arylazonaphthols. The contribution from an intramolecular hydrogen bond or O–H⋯NH 2 hydrogen bond caused due to the pertinent substitution at the 1,8-positions in the naphthalene nucleus retards the attack of 1O 2, but the dyes could be destroyed by TiO 2 photoassisted catalysis. Compared with photosensitised degradation, homogeneous photocatalysis is a possible way of evaluating the light-fastness of azo dyes.