Executive Summary : | In recent years, there have been increasing global evidences of the presence of persistent organic pollutants (POPs) in the aquatic bodies, primarily due to the inefficiency of conventional treatment processes in achieving their efficient removal from wastewater. Various advanced oxidation processes (AOPs), predominantly relying on the generation of hydroxyl radicals, are being increasingly investigated for removing these compounds, since they could potentially achieve complete mineralization. Amongst the available AOPs, photocatalysis is considered as a promising technology due to its efficient and environment friendly nature. Also, TiO2 has been extensively utilized as an efficient photocatalyst, since it is inexpensive and potentially non- toxic, possesses stronger photocatalytic activity and thus high oxidative power, and demonstrates high photochemical stability. However, the wide band gap and narrow optical absorption range of TiO2 limits its practical applications as a photocatalyst with the UV light (less than 5% of the solar spectrum) only, while rendering it inefficient to be used with visible light (~ 45% of the solar spectrum). This is a major limitation in developing efficient solar photocatalysis processes with TiO2 as photocatalyst. To address this limitation of TiO2 based photocatalysis, various surface modifications in TiO2 (e.g. doping / codoping, dye sensitization etc.) have been proposed which effectively extend its applicability with the visible light. Amongst the available surface modification techniques, dye-sensitized photocatalysts are perceived as the novel visible light-responsive photocatalysts for future industrialized applications. However, the conventional synthetic dyes pose several environmental concerns during their application as sensitizers, including their complex synthetic routes, environmental toxicity, and low yield. In comparison, natural dyes/pigments are a viable alternative to other rare and toxic synthetic dyes because of their low cost, easy attainability, abundance in the supply of raw materials, and environment-friendly nature. Since, chlorophylls are the most abundant and naturally occurring environment friendly pigments, it is important to investigate their potential to be used as sensitizers. In this context, the aim of this proposed research is to systematically investigate the feasibility of using natural chlorophyll pigments as sensitizers of TiO2 for visible light photocatalysis. Further, important parameters will be identified and optimized for their efficient application. Finally, studies will also be undertaken to prepare a suitable sensitized catalyst to efficiently utilize the solar spectrum for their potential application in solar photocatalysis. Such an investigation is highly relevant towards realizing an environmental friendly and sustainable visible/solar light photocatalysis. |