Calotropis gigantea leaves assisted biosynthesis of ZnO and Ag@ZnO catalysts for degradation of rhodamine B dye in aqueous medium

The semiconductor metal oxides based photocatalysis is one of the efficient techniques used for eradication of pollutants from wastewater. The plants mediated biosynthesis of metal oxides have got much interest due to environmentally friendly and cost‐effective nature. This article reports the Calotropis gigantea mediated biosynthesis of ZnO and Ag@ZnO as effective catalysts for degradation of rhodamine B (RhB) dye. After characterization with advanced techniques, the biosynthesized ZnO and Ag@ZnO were tested as photocatalysts on degradation of RhB dye under irradiation. The catalytic activity of ZnO and Ag@ZnO was estimated in terms of decolorization, COD, and TOC removal. Results showed that 50.4 and 90.2% decolorization, 41.3 and 74.8% removal of COD, and 45.3 and 83.5% removal of TOC were measured over ZnO and Ag@ZnO as photocatalysts in 120 min, respectively. The biosynthesized Ag@ZnO was a stable and reusable catalyst in degradation experiments.