Evaluating the effectiveness of photocatalysts based on titanium dioxide in the degradation of the dye Ponceau 4R

The performance of different titanium dioxide (TiO2) catalysts and a composite based on the association between TiO2 P25 and Zinc Phthalocyanine (TiO2/ZnPc 1.6%) was evaluated in the photocatalytic degradation of the dye Ponceau 4R (C.I. 16255). The results show that the composite presents a better performance than the other, reaching about 50% mineralization of the dye in 120 min of reaction, around three times higher than that observed under the action of pure TiO2 P25, although this catalyst presents a quantum yield of hydroxyl radical generation about three times higher than that estimated for the composite. This result seems to be a consequence of the synergism between the electronically excited ZnPc aggregates and the TiO2 surface.A parallel study, based on methods from quantum mechanics also suggested the most feasible routes for the photodegradation of the dye in the absence of the catalyst.

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► Six different catalysts based on TiO2 and a TiO2/ZnPc composite were studied.
► Their performance was compared by the photocatalytic degradation of Ponceau 4R.
► The composite was the photocatalyst more effective in promoting the degradation.
► This remarkable result is due to the synergism between ZnPc aggregates and TiO2.
► A quantum mechanical study evaluated the dye degradation by direct photolysis.