Gatifloxacin photocatalytic degradation in different water matrices: Antimicrobial activity and acute toxicity reduction

The main goal of this study is to evaluate the feasibility of using heterogeneous photocatalysis to degrade the organic contaminant gatifloxacin (GAT) and reduce the antimicrobial activity and acute toxicity from different water matrices. Assays were performed using four water matrices (ultrapure water -UW, mineral water -MW, potable water -PW, and simulated surface water -SW) fortified with gatifloxacin (500 mu g L-1) as a model antibiotic contaminant and its quantification was followed using online SPE-UHPLC-MS/MS. Initially, the photocatalytic process efficiency towards GAT removal as a function of UV light wavelength (UVA and UVC), catalyst type (TiO2-P25 or TiO2-PC500), photocatalyst loading (from 1 to 200 mg TiO2 L-1), solution pH (from 4 to 9), GAT initial concentration (from 50 mu g GAT L-1 to 5000 mu g GAT L-1) and water matrix (UW, MW, SW or PW) was assessed. In this context, the TiO2-PC500 system using UVA showed the best removal performance of GAT. With TiO2-PC500 loadings higher than 10 mg L-1, > 90% of GAT degradation was achieved after only 40 min of reaction. Finally, the system efficiency was evaluated according to its ability to reduce the antimicrobial activity of the solutions against Gram-negative and Gram-positive bacteria as well as their acute toxicity to A. fischeri bacterium. The antimicrobial activity in the solutions dropped along the reaction time, but no toxicity variation was observed.