Photostability of the UV filter benzophenone-3 and its effect on the photodegradation of benzotriazole in water

Abstract

Environmental contextThe environmental fate of a particular contaminant can be influenced by the presence of other chemicals. It is shown that the photodegradation in water of benzotriazole, a common household and industrial chemical, is reduced in the presence of a sunscreen compound. Thus, contaminants such as benzotriazole may persist longer in the environment in the presence of chemicals designed to filter ultraviolet rays, such as those used in sunscreens. AbstractThe presence of co-solutes (e.g. UV filters) can potentially influence the environmental fate of micropollutants. The photolysis of benzotriazole (BT, an anticorrosion agent) and benzophenone-3 (BP-3, a UV filter), as well as their interactions in aqueous solutions under UV and artificial solar light with or without added humic acid (HA) and metal ions (Cu2+ and Fe3+), has been investigated. BT was found to be photosensitive under UV irradiation, but photostable under solar light. The half-lives for the photolysis of BT were 2.8 h in pure aqueous solution and increasing to 4.5 h in the presence of BP-3 (1.0 mg L–1). BP-3 was photostable under both UV and artificial solar light. Solar radiation exposure of 50 days resulted in a small loss of BP-3 (8 %) in pure aqueous solution, and resulted in a greater loss of BP-3 (up to 31 %) at 50 mg L–1 of HA. UV irradiation of the BT solutions containing BP-3 led to formation of five photoproducts, formed mainly by N–N and N–NH bond scission, polymerisation and hydroxylation. In the case of BP-3, one major photoproduct was isolated and tentatively identified as 2,4-dimethylanisole, formed by the loss of hydroxy and benzoyl groups.