Research Journal of Recent Sciences ________________________________________________ ISSN 2277-2502
Vol. 1 (ISC-2011), 191-201 (2012)
Res.J.Recent Sci.

Ultrasound assisted semiconductor mediated catalytic degradation of organic
pollutants in water: Comparative efficacy of ZnO, TiO2 and ZnO-TiO2
Anju S.G., Jyothi K.P., Sindhu Joseph, Suguna Y. and Yesodharan E.P.*
School of Environmental Studies, Cochin University of Science and Technology, Kochi-682022 INDIA

Available online at: www.isca.in
(Received 26th November 2011, revised 6th January 2012, accepted 25th January 2012)

Abstract
Sonocatalytic degradation of organic pollutants in water is investigated using ZnO, TiO 2 and combination of ZnO and TiO2
(ZnO-TiO2) as catalysts, with phenol as the test substrate. The efficacy of the catalysts is in the order ZnO-TiO2 > ZnO > TiO2.
The degradation in presence of ZnO-TiO2 is more than the sum of the degradation achieved in presence of the individual oxides
under identical conditions, thereby demonstrating a synergistic effect. The ratio of the components in the mixed oxide is
optimized. The kinetics of the degradation as well as the influence of various parameters such as catalyst loading, concentration
of the pollutant and pH on the degradation efficiency is evaluated. Maximum degradation is observed in the acidic pH for all
catalysts. H2O2 is formed in the reaction and it undergoes simultaneous decomposition resulting in periodic increase and
decrease in its concentration. This observation of the phenomenon of oscillation in the concentration of H2O2 is the first of its
kind in sonocatalytic systems. A mechanism for the degradation of phenol is proposed based on the observations as well as the
concurrent formation and decomposition of H2O2.
Keywords: Zinc oxide, titanium dioxide, sonocatalysis, phenol, hydrogen peroxide.

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