The riboflavin-photosensitized degradation of the uv-absorbing azo dye-metabolites Benzidine and o-Tolidine. Kinetic and mechanistic aspects

•The natural pigment riboflavin (Rf) promoted the photodegradation of two carcinogenic azo-dye metabolites (BZ-C) Benzidine and o-Tolidine.•The effective BZ-C degradation is mainly driven by the photogenerated ROS distinct of singlet molecular oxygen.•The comparison of BZ-C photooxidative-rate with archetypal surface-water-contaminants aniline and phenol indicates that BZ-C degradation occurs in a moderately slower fashion than the reference contaminants.•The natural Rf- photosensitized degradation of BZ-C appears as a plausible process, as evaluated under simulated environmental conditions.