Inhibition of the Photocatalytic Degradation of Benzoic and Salicylic Acid by Nontoxic Aromatic Compounds

Abstract

This work studies the photocatalytic degradation of benzoic (HBz) and salicylic acid (HSal) in the presence of nontoxic aromatic compounds (phenylalanine, tyrosine, tryptophan, and sodium benzenesulfonate). The purpose is to find compounds able to compete for electron‐transfer processes in photocatalysis: the failure to do this is one of the main drawbacks of currently adopted sunscreens. Sodium benzene sulfonate (SBS) proved to be quite effective in inhibiting electron transfer as demonstrated by its effect on the photocatalytic degradation of HBz and HSal. Furthermore, a mixture of SBS and 1,3‐butanediol was able to inhibit the photocatalytic degradation of both phenol and HBz. This fact indicates that the mixture is able to block both the hydroxylation pathway (responsible for phenol degradation) and the electron‐transfer one (HBz degradation). The simultaneous inhibition of the degradation of both phenol and HBz has not been observed in commercial sunscreen treatments. This work thus shows that the use of nontoxic aromatic compounds can be a way to improve sunscreen performance, and that the photocatalytic degradation test of phenol+HBz (or phenol+HSal) is the most appropriate way to find the best performing treatments.

Keywords:

• Titanium dioxide
• rutile
• photocatalysis
• solar creams
• solar gels
• sunburn