Au-sensitised TiO2 and ZnO nanoparticles for broadband pharmaceuticals photocatalytic degradation in water remediation

A large number of contaminants of emerging concerns, such as most pharmaceuticals, exhibit high persistency in water bodies due to the difficulty of their removal by conventional treatment methods, causing severe environmental issues. Semiconductor-based photocatalysis has become an exciting solution to remove these pollutants through photocatalytic degradation. However, the high diversity of chemical composition of pharmaceutic pollutants hinders the selection of an adequate photocatalyst for efficient and broadband pollutants removal, making necessary the development of systematic studies that link the physicochemical photocatalyst and pollutant properties with the degradation performance. Here, four different photocatalysts have been synthesised, physical-chemically characterised and systematically compared in the photocatalytic degradation of four highly abundant and chemically different pharmaceuticals in water remediation field: chloroquine phosphate (CLQ), paracetamol (PAR), diclofenac sodium (DCF), and ciprofloxacin (CIP). The photocatalysts were selected to be easily accessible, cost-effective, and scalable, including the well-known TiO2 and ZnO, and the plasmonic photocatalysts versions TiO2:Au and ZnO:Au, which were synthesised, characterised, and assayed under UV and visible light. The results show that the photocatalytic degradation correlated with the amount and type of reactive oxygen species generated by photocatalysts, electrostatic interaction between pollutants and photocatalysts. High degradation efficiencies were shown for all photocatalysts and differences were observed as a function of the pollutant for the ZnO- and TiO2-based photocatalysis. Finally, the Au nanoparticle sensitising displayed remarkable improvement concerning the homocomponent counterparts under visible radiation opening the door for degrading pollutants in a cost-effective way.