Discoloration of dye solutions induced by solar photolysis of ferrioxalate in aqueous solutions

The discoloration of four dyes, C.I. reactive red 2, C.I. reactive black 8, C.I. basic red 13 and C.I. basic yellow 2, were induced by solar photolysis of ferrioxalate in aqueous solutions. The discoloration of the dye solutions were all pseudo-first order reactions. The discoloration rates of the dye solutions in sunlight/ferrioxalate system is about the same as in UV/ferrioxalate system, while much higher than in sunlight/Fe(III)-hydroxy system.