Photosensitized Oxidation of Emerging Organic Pollutants by Tetrakis C60 Aminofullerene-Derivatized Silica under Visible Light Irradiation

We recently reported that C-60 aminofullerenes Sunlight immobilized on silica support (aminoC(60)/silica) efficiently produce singlet oxygen (O-1(2)) and inactivate virus and bacteria under visible light irradiation.(1) We herein evaluate this new photocatalyst for oxidative degradation of 11 emerging organic contaminants, including pharmaceuticals such as acetaminophen, carbamazepine, cimetidine, propranolol, ranitidine, sulfisoxazole, and trimethoprim, and endocrine disruptors such as bisphenol A and pentachlorophenol. Tetrakis aminoC(60)/silica degraded pharmaceuticals under visible light irradiation faster than common semiconductor photocatalysts such as platinized WO3 and carbon-doped TiO2. Furthermore, aminoC(60)/silica exhibited high target-specificity without significant interference by natural organic matter. AminoC(60)/silica was more efficient than unsupported (water-suspended) C-60 aminofullerene. This was attributed to kinetically enhanced O-1(2) production after immobilization, which reduces agglomeration of the photocatalyst, and to adsorption of pharmaceuticals onto the silica support, which increases exposure to O-1(2) near photocatalytic sites. Removal efficiency increased with pH for contaminants with a phenolic moiety, such as bisphenol A and acetaminophen, because the electron-rich phenolates that form at alkaline pH are more vulnerable to singlet oxygenation.