Sonocatalytic and sonophotocatalytic degradation of rhodamine 6G containing wastewaters

Abstract

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.

Decolorization of brilliant green dye using immersed lamp sonophotocatalytic reactor

“…The results are consistent with the reported findings. The study of US-UV degradation of rhodamine 6G indicated that degradation increases with the addition of copper oxide; the maximum degradation of 52.6% was observed for (1.5 g/L loading of copper oxide) US-UV treatment and 26.4% for UV treatment at 12.5 pH of the solution (Bokhale et al 2014). Similar results reported for US-UV degradation of dye C.I.…”

“…During photolysis, photon released from the UV source is absorbed by the water molecule and breaks the bond between the H Á and Á OH ions. Production of hydroxyl radicals during sonolysis depends on the liquid physiochemical properties of an aqueous medium, such as vapor pressure and surface tension (Bokhale et al 2014). Decolorization of BG enhanced on the multifold basis for the synergic combination of US-UV.…”

“…During cavitation cycle, reactions are occurring at the three zones: (a) inside the cavity of the bubble, (b) at the interface of gas-liquid, and (c) radicals generated after the collapse of the cavity. (Sathishkumar et al 2016;Marković et al 2015;Ahmedchekkat et al 2011, Bokhale et al 2014. When UV light (photocatalysis) passes through the aqueous solution, the holes (h ? )…”

Sonophotocatalytic degradation of Reactive Red 120 (RR120) in the presence of TiO2: Kinetic study

“…Although individual AOPs seem useful to treat textile wastewater, however they are also demonstrates substantially lower efficiency of degradation and complete mineralization especially for the complex effluent streams. The operation cost for this technique is also higher [6].…”

Synthesis of ZnO/CuO and TiO2/CuO nanocomposites for light and ultrasound assisted degradation of a textile dye in aqueous solution

“…The maximum degradation of 93% and 94% were achieved for photocatalysis, while 99.9% and 100% were obtained for sonocatalysis. These results suggested that the better efficiency of the combination processes of both irradiations compared to separately irradiation is not due to synergistic effects [14]. It is believed that sonolysis can increase the photocatalytic activity by: (i) increasing the catalytic activity of catalyst through the size reduction [15]; (ii) accelerating the mass transfer between the solution phase and catalyst surface [15].…”