A Study on Simultaneous Photocatalytic Removal of Hexavalent Chromium and Pharmaceutical Contaminant from Aqueous Phase

Abstract

Chromium (Cr) as Cr(+VI) is a well known environmental pollutant being highly toxic to most organisms including humans and are difficult to remove. Pharmaceuticals have also become a cause of environmental concern in recent years. Photocatalysis has emerged as a potential technology for treating variety of environmental pollutants and has gathered research interest in recent years for removing Cr(+VI). Among the reported photocatalysts titanium dioxide (TiO2) and zinc oxide (ZnO) had been widely studied due to high bandgap energy. However, the potential of ZnO as photocatalyst in the removal of Cr(+VI) is less explored. Studies also reported that presence of iron (Fe) ions and sacrificial organic electron donor greatly influence the photocatalytic removal of Cr(+VI). Accordingly the present study evaluated the efficacy of ZnO and Fe-impregnated ZnO (Fe--ZnO) in photocatalytic removal of Cr(+VI) with a model pharmaceutical compound, methylene blue (MB), as sacrificial electron donor under solar radiation. Fe incorporated ZnO was fabricated and X-ray diffraction (XRD) confirmed thet Fe penetrated into the ZnO lattice. The incorporation of Fe in ZnO resulted in shift in bandgap energy and allowed better utilization of solar radiation. Fe incorporation and presence of organic electron donor (MB) enhanced the Cr (+VI) in comparison to ZnO. Also, increase in catalyst loading enhanced the photo-reduction of Cr (+VI). A maximum of 48 % reduction of Cr(+VI) was recorded with 98 % MB discoloration with Fe-ZnO in 4 h of exposure in solar radiation. The present work demonstrates an alternative approach wherein two different toxic and problematic waste was simultaneously remediate in a sustainable manner.