Abstract
Natural dye sensitizers are environment-friendly and inexpensive substances that could be used for photocatalytic decontamination of organic pollutants. In this study, a natural dye extracted from mangosteen peel, containing a significant amount of anthocyanin dye, has been successfully employed to sensitize aeroxide TiO2 to lower its bandgap, thereby making the process visible sunlight-driven. We have demonstrated the photocatalytic activity of mangosteen dye-sensitized-TiO2 (MS-TiO2) under visible solar light by studying the degradation of methylene blue (MB), a well-studied model compound. A multivariate parametric study was performed using factorial design methodology with three factors—pH, MS-TiO2 dosage, and visible light intensity. The study indicated that pH and MS-TiO2 dosage are the two most dominant factors for MB degradation under visible solar light. The kinetic rate constant and adsorption equilibrium constant were determined, and a Langmuir-Hinshelwood-type equation was proposed to describe MB degradation on MS-TiO2 under visible solar light. Apparent quantum yield was also reported for the MS-TiO2 photocatalyst at optimum experimental conditions.
Highlights
In an era where freshwater scarcity is turning into an environmental systemic risk, degradation and complete mineralization of organic contaminants are of immense significance
The dye molecule gets excited by absorbing visible solar light, and an electron is transferred from its highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) [7]
We determined of approximately mg anthocyanin content per 100 g of dry mangosteen peel
Summary
In an era where freshwater scarcity is turning into an environmental systemic risk, degradation and complete mineralization of organic contaminants are of immense significance. This provides an opportunity to use this dye sensitization technology for photocatalytic water decontamination processes as well [7,15,16] In this sensitization process, the dye molecule gets excited by absorbing visible solar light, and an electron is transferred from its highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) [7]. Catalysts 2020, 10, 917 photocatalyst molecule, resulting in the formation of a highly reactive superoxide anion (O2 − ) and/or hydroxyl radical (OH· ) [16] In this approach, the entire photocatalytic process becomes visible sunlight-driven, which is the most abundant natural source of energy. No study has yet been performed with a mangosteen peel-based natural dye-sensitized aeroxide TiO2 system under visible solar light. Results andasDiscussion solution pH, visible solar light intensity, and photocatalyst dosage—a statistical approach was adopted to understand the complete and combined effect of three independent variables on the
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