Photocatalytic performance of Ag2O towards sulfamethoxazole degradation in environmental samples

Abstract

In recent years, great concerns have been expressed considering the large number of antibiotics detected in both treated and surface waters posing serious threats to human beings. Amongst various technologies used for water cleaning, photocatalysis has shown promising results towards the complete degradation of various micropollutants under ambient conditions. In this study, silver oxide (Ag2O) was synthesized according to an ion-exchange method, characterized and tested for the photocatalytic degradation of an antibiotic agent, sulfamethoxazole (SMX), under simulated solar irradiation. The photocatalytic activity of Ag2O was tested in real water matrices (bottled water (BW) and wastewater (WW)). Results showed that 0.5 mg/L SMX is efficiently degraded with the use of 25 mg/L Ag2O in BW in 120 min, while only 30 min are required in case of higher catalyst concentration (100 mg/L). Results obtained with the use of chlorides and bicarbonates showed promoting and zero effect on SMX degradation, correspondingly. Retarding phenomena were observed in the case of WW, which were partially conquered increasing Ag2O dosage. This behavior was partially attributed to the adverse effect of humic acid. Experiments conducted at different solution pH values showed a slight delay in SMX removal in the case of basic environment. Addition of persulfate ions in the reaction mixture clearly improved the efficiency of the present photocatalytic system. Radical quenching experiments revealed that SMX degradation takes place mainly through direct oxidation with photogenerated holes. Finally, experiments conducted with a UV cut-off filter showed that Ag2O can be categorized as a visible light photocatalytic material.