Investigations on the role of manganese based nanomaterials and nanocomposites for degradation of organic dyes

Abstract

The urge to maintain a high standard of living has made man depend more on synthetics than natural. This increasing demand has resulted in complex residuals, majority of which are incompatible with the environment. Now, Mother Nature is no longer capable of generating scavengers that can auto-repair the environment. A realistic approach is to design technology in harmony with the environment. At the end, it is desirable that waste treatments result in eco- friendly products. Dyestuffs constitute one of the largest groups of toxic organic compounds. Their general classification is based on the type of chromophore group in the molecular moiety [1]. The removal of dyes has been an indecisively pursued Subject in the last decade. Mn based element with its chemically inert nature, cheaper price and high redox ability is an ideal choice for energy and environmental applications. Also, a mixture of these two polymorphs has been reported to produce enhancement in charge carrier transfer processes [2, 3]. However, the low quantum efficiency of Mn based nanoparticles limits large scale applications. The present work outlines different routes to remove the limiting aspects of Mn based composites. Surface modification of MnO and MnS by another nanoparticle (TiO2 and ZnO) and by surfactant was achieved via different synthesis method. This is a new field of research to describe the effect of precipitation on chemical reactions. The surface modification induces a red shift of the absorption edge of Mn based element. This is essential for the visible light response of the nanocomposites that could lead to more efficient utilization of the solar energy. One of the crucial pre-requisites for efficient dye removal is adsorption or the dye on the photocatalyst surface. This was estimated from BET isotherms. The surface charge of the dye and textural properties of the composites need to be considered for adsorption. The operational parameters of photocatalysis were also optimized using response surface methodology.