Bismuth ferrite as innovative and efficient photocatalyst for the oxidation of As(III) to As(V) under visible light

Abstract

The presence of As in drinking water is a problem felt all over the world. In particular, arsenic is present in +3 (As(III)) and +5 (As(V)) oxidation states. However, As(III) is the most toxic and difficult to remove with conventional adsorption processes. A pre-oxidation process is therefore necessary. In this work, we report, for the first time, the use of BiFeO3 as a visible-light active photocatalyst for the complete and fast oxidation of As(III) to As(V) in water. In particular, the influence of annealing temperature for BiFeO3 preparation was studied and the prepared photocatalysts were characterized through XRD, N2 adsorption at −196°C, TEM, XPS, Raman and UV–Vis DRS spectroscopy. The best photocatalytic activity was achieved with BiFeO3 calcined at 550°C. The influence of catalyst dosage and the role of the main oxidizing species was evaluated, evidencing the key role of h+ in the photooxidation reaction of As(III) to As(V). Moreover, the efficiency of the photocatalyst was also evaluated in the case of drinking water contaminated by arsenic. The results demonstrated that, despite the presence of dissolved salts in the drinking water, the photocatalyst maintained its activity. The results obtained in this work prove that BiFeO3 calcined at 550°C evidenced photocatalytic performances better than different photocatalyst formulations studied for the photooxidation of As(III) to As(V) under visible light.