The present work deals with degradation of aqueous solution of Rhodamine 6G (Rh 6G) using sonocatalytic and sonophotocatalytic treatment schemes based on the use of cupric oxide (CuO) and titanium dioxide (TiO2) as the solid catalysts. Experiments have been carried out at the operating capacity of 2 L and constant initial pH of 12.5. The effect of catalyst loading on the sonochemical degradation has been investigated by varying the loading over the range of 1.5-4.5 g/L. It has been observed that the maximum degradation of 52.2% was obtained at an optimum concentration of CuO as 1.5 g/L whereas for TiO2 maximum degradation was observed as 51.2% at a loading of 4 g/L over similar treatment period. Studies with presence of radical scavengers such as methanol (CH3OH) and n-butanol (C4H9OH) indicated lower extents of degradation confirming the dominance of radical mechanism. The combined approach of ultrasound, solid catalyst and scavengers has also been investigated at optimum loadings to simulate real conditions. The optimal solid loading was used for studies involving oxidation using UV irradiations where 26.4% and 28.9% of degradation was achieved at optimal loading of CuO and TiO2, respectively. Studies using combination of UV and US irradiations have also been carried out using the optimal concentration of the catalysts. It has been observed that maximum degradation of 63.3% is achieved using combined US and UV with TiO2 (4 g/L) as the photocatalyst. Overall it can be said that the combined processes give higher extent of degradation as compared to the individual processes based on US or UV irradiations.
A B S T R A C TRemoval of patent blue V dye from aqueous solutions has been investigated in the present work using air bubble-induced oxidation based on the use of glass balls. The dependency of removal of patent blue V on the operating parameters, such as initial concentration and pH has been established and it has been observed that optimum initial concentration of dye exists and also acidic conditions are favourable for enhancing the degradation. The effect of intensifying additives, such as ZnO, TiO 2 and MnO 2 as well as combination with ferrous sulphate has been investigated for the first time for the case of air bubble-induced oxidation. The maximum extent of removal (97%) of patent blue V was observed for the combined approach of air bubble-induced oxidation and ferrous sulphate, which promote the production of HO Å through the radical mechanisms. For the different oxides, the order of activity for higher removal of patent blue has been observed as TiO 2 > MnO 2 > ZnO. The present work has enabled the development of an intensified process involving use of air bubble oxidation for the treatment of dye containing wastewaters.
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