Studies on metal oxide nanomaterials for heterogeneous photocatalyzation of dyes in water

Abstract

Two serious issues faced by people of developing countries are with fossil fuels getting exhausted every moment, energy has to be produced and conserved in a way compatible with nature and environment to meet the growing needs of people and a pollution free atmosphere to secure present and future generations from hazardous chemicals which can cause serious threat to public health. Through detailed literature survey, in this research work I have initiated a step to eradicate organic dye named methylene blue (MB) from industrial waste water which is carcinogenic under constant exposure. The principle behind this is a bio-mimic called artificial photosynthesis. Major challenge to achieve this was to find a suitable photocatalysts with specific properties. Mn3O4 was chosen to be suitable material to serve the above purpose as it is a semiconductor of low cost, ecofriendly and abundant in nature and also limited research is done on p-type semiconductors for photocatalytic activity. Generally, only one dopant is added but in this work a series of dopants are added to study the promotion of activity in detail. Performed solid - state synthesis to obtain pure Mn3O4 nano photocatalysts and their methylene blue dye degradation efficiencies were investigated. Though to some extent it proved to be possible to decolour MB however desired results were not obtained so modifications were performed by incorporating Zinc, Nickel and Chromium. After adding transition metal ions, changes in the structure, morphology, regulated bang gaps and surface area was observed which were confirmed by a series of characterizations namely X-Ray diffraction, Scanning electron Microscope, UV-Vis Diffuse Refluctance Spectroscopy and BET analysis as they brought significant iv changes to the overall properties of the photocatalysts making them proficient. Oxidation of model dye (methylene blue) was studied by using the synthesized products as photocatalysts. The effect of operational parameters such as time and dopant concentration was analyzed from