Photocatalytic degradation of acid azo dyes in aqueous TiO2 suspension -: I.: The effect of substituents

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 oil both sides of the trans-azobenzene backbone in o-ary-lazonaphthols. The contribution from an intramolecular hydrogen bond or O-H ... NH2 hydrogen bond caused due to the pertinent substitution at the 1,8-positions in the naphthalene mucleus retards the attack of O-1(2), but the dyes could be destroyed by TiO2 photoassisted catalysis. Compared with photosensitised degradation, homogeneous photocatalysis is a possible way of evaluating the light-fastness of azo dyes. (C) 1998 Elsevier Science Ltd.