Reduction of methylene blue with reducing sugars: Kinetics of reduction of methylene blue with organic reductants

The photobleaching of methylene blue with reducing sugars in 50% aqueous methanol using acetate buffer has been investigated with steady ? illumination of monochromatic radiations of 661 nm on specially designed optical bench in a dark room. The dye reduction processes were studied at various parameters i) concentrations of dye, ii) concentrations of reductants such as Galactose, D-Mannose, D-Ribose, Maltose and Lactose, iii) acidity Ho of reaction solution iv) temperature as a function of quantum yield . Hammett acidity function Ho was used to determine acidity of the reaction solution. The optical method was adopted to evaluate the values of Ho. Bleaching of the dye simultaneously with demethylation has been observed upon irradiation, color recover as the source of irradiation turned off or exposure to air. Reaction follows second order kinetics with respect to dye concentration and reductant and first order with respect to triplet transient species with life time of 10.1 micro s.