Fe-TiO2 and Ag-ZnO mediated visible light photocatalysis for atenolol and acetaminophen removal – A comparative study and modeling

Abstract

Globally, presence of pharmaceutical contaminants (PCs) in environment is a cause of concern. In this study, performance of the green synthesized nano-composites Fe-TiO2 and Ag-ZnO as visible light photocatalyst was evaluated by considering the removal of PCs viz., atenolol (ATL) and acetaminophen (ACT) spiked in treated domestic wastewater. Advanced oxidation process was performed in a batch photoreactor under visible radiation (650 nm). Removal of PCs were studied by considering four experimental factors viz., initial pH (4 to 12), initial ATL and ACT concentration (5 to 20 mg/L), visible photo catalyst concentration (500 to 1500 mg/L) and reaction time (40 to 120 min). Response surface methodology was used, regression models were developed (R2adj > 85 %), and optimization of factors was performed for the contaminant removal. It was found that, both Fe-TiO2 and Ag-ZnO performed well (ATL removal >63 %, and ACT removal >85 %) though, Fe-TiO2 had higher removal efficiency. It was found that the maximum removal of contaminants occurred when contaminant concentration was 5 mg/L, pH 8, catalyst concentration 1055 mg/L and reaction time 98 min. Characteristics of ATL and ACT photocatalytic degradation was performed and it was found that the contaminant removal was predominantly through the photocatalytic mechanism majorly due to OH oxidation pathway rather than adsorption and photolytic process. Further, the COD and TOC experiments indicated that >50 % mineralization could be achieved for both ATL and ACT, indicating that both the nanomaterial can be effectively used as a photocatalyst in the visible light radiation.