Ball-milled synthesis of maize biochar-ZnO nanocomposite (MB-ZnO) and estimation of its photocatalytic ability against different organic and inorganic pollutants

Different industrial and agricultural practices release a variety of dyes and pesticides in soil and water. Degradation of these pollutants is very important to avoid health and environmental issues. In this study, the photocatalysis technique has been optimized and adopted to degrade organic and inorganic pollutants. First of all, biochar with distinctive physicochemical properties, like high specific surface, highly carbonaceous property, and the electron-conductive nature was prepared in a vacuum furnace from maize straw. These properties depicted the effective absorbance ability of prepared biochar. Using a solvent-free ball-milling method, ZnO loaded maize biochar nanocomposite (MB-ZnO) was synthesized from this biochar and used as a photocatalyst to degrade aqueous pollutants, under different light sources. The adsorption and photocatalytic activity of MB-ZnO was assessed against Safranin O (Saf) and Mancozeb (MC) within a closed system using different light conditions including dark, UV and visible light. To understand the mechanism of Saf and MC removal from aqueous solution, reaction kinetics was calculated according to the pseudo-first-order kinetic model. MB-ZnOcomposite exhibited variable photocatalytic performances to degrade Saf under visible light (83.5%), UV radiations (81.0%) and dark conditions (78%) in 60 min. Similarly, maximum MC degradation by MB-ZnO nanocomposite was exhibited in visible light (56.5%), followed by UV radiations (27.5 %) and dark conditions (25.2%). The findings of this study concluded that MB-ZnO nanocomposite can be used as an excellent catalyst to remove aqueous pollutants, under both light and dark conditions.