Effect of Some Additives Used in the Cosmetic Field on the Photocatalytic Activity of Rutile

Abstract

The effects of some treatments used in cosmetics to reduce the activity of titanium dioxide towards the degradation of organic compounds are reported. These treatments, which include the use of organic additives and of inorganic surface coating, are aimed to protect the components of sunscreen formulations, and also the skin, from the photocatalytic processes induced by TiO₂ UV absorption. The effect of the addition of 1,3-butanediol (organic treatment) on the degradation rates of phenol, benzoic acid, and salicylic acid upon UV-A irradiation of rutile is assessed and discussed. About the inorganic coating, the effect of the surface treatment with Al₂ O₃ on the photocatalytic activity of rutile towards both phenol and salicylic acid is evaluated. The organic and the inorganic treatment are both very effective in inhibiting phenol degradation, but ineffective in avoiding degradation of salicylic acid. The results indicate that the degradation tests of both phenol and salicylic acid can be a useful tool for the evaluation of the efficiency of treatments aimed at reducing the effects that titanium dioxide photoactivity has on cosmetic formulations.