Degradation of Brilliant Green (BG) dye has been studied using Fenton reagent in the dark environment. The intensity of dye color was pH dependent with maximum absorbance at pH 6. N-de-alkylation caused dye decomposition which resulted in the reduction of absorbance. The rate of BG dye decolorization increased with an increase in the H 2 O 2 and Fe 2? concentration. The presence of background ions commonly found in an industrial dyeing wastewater suppressed the efficiency of color, COD and TOC removal within 9 %. There was about 2.9-fold increase in biodegradability index after 30 min of reaction. The proposed mechanism showed the routes of dye degradation with low errors (-0.88 to 0.49 g mol -1 ) with respect to the exact mass. Dye degradation began with Nde-ethylation, and later was further cleaved to aromaticamine, -acid, -alcohol and -additive products. Hydroquinone was originated by hydroxylation of N,N-diethyl aniline. An equilibrium cycle among quinone, hydroquinone and Fe(III)-hydroquinone was exhibited through the formation of charge transfer complex.

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A B S T R A C THeterogeneous photocatalytic wastewater treatment using TiO 2 is a well-accepted technique under UV light illumination. Different strategies are employed to modify TiO 2 for shifting its photo-response to the visible light. In this work, Ag-doped TiO 2 nano-composites were synthesized by UV photo-reduction method to narrow down the band gap energy. Further, dye sensitization was performed using Eosin Yellowish to find out its influence on phenol decomposition. Synthesized catalysts were characterized using diffuse UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy (TEM), Brunner Emmer Teller (BET) area and zeta-potential measurements. Nanowire like structure was observed with 30-70 nm in diameter from TEM images. BET surface area was decreased considerably with Ag-doping (maximum 31.6%) and dye sensitization (40.6%). Ag concentration and solution pH showed dramatic impact on phenol decomposition with maximum 87% at pH 7, Ag-loading 1% (w/w) and catalyst dose 0.5 g L −1 . Practically no positive synergy was noted with dye sensitization even though the photo-responses were moved intensely to the visible region. The pseudo-first order kinetic exhibited sound agreement to the experimental results with correlation coefficient ≥0.98. Moreover, the enhancement of biodegradability is investigated in terms of biochemical to chemical oxygen demand.