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Р-26: Sonophotocatalytic Degradation of Methyl Orange using TiO2 Photo-catalysts
Prepared under Different Experimental Conditions
Allegra Magenta,1 Meifang Zhou,2 Muthupandian Ashokkumar,2 Laura Prati1
and Claudia L. Bianchi1*
1Università di Milano – Dipartimento di Chimica, 20133 Milano, Italy; 2School of Chemistry, University of Melbourne, VIC 3010, Australia The sonochemical oxidation process has been found to be a potentially useful technique for the degradation of organic pollutants in an aqueous environment. In this technique, free radicals are generated during the violent collapse of acoustic cavitation bubbles. These free radicals react with organic pollutant molecules in several reaction pathways and reactive zones. The sonochemical process is often combined with other widely known advanced oxidation processes, such as, ozonation, photocatalysis and Fenton and photoFenton reactions. In this study, sonochemical technique is combined with photocatalysis for the degradation of an organic dye in aqueous environment. A number of photocatalysts were synthesized using conventional technique for use in sonophotocatalysis experiments. Nine different samples of titania were prepared using 3 different solvents (2-propanol, heptane and 2-ethyl- hexyl-alcohol) and different calcination conditions with and without gold loading. Constant molar ratios between water/titanium isopropoxide and water/alcohol were maintained during the preparation process. Briefly, titanium isopropoxide in alcohol was taken in a water-jacketed reactor and a known amount of water was added slowly. The mixture was left for 90 minutes for hydrolysis to complete. The solution was then evaporated and the solid sample was dried and calcined at a desired temperature. The synthesised catalysts were characterized by a variety of analytical techniques that include XRD, TEM, TGA, XPS, etc. The TiO2 particle size was in the range 5-10 nm (Figure 1a). Sonolytic, photocatalytic and sonophotocatalytic degradation of methyl orange were carried out to evaluate the efficiency of the synthesized catalysts. TiO2 modified by the addition of 0.5%wt of gold nanoparticles were also tested. Figure 1: (a) TEM of TiO2 photocatalyst prepared in heptane with 0.5% gold loading and calcined at 300 oC; (b) a comparison of sonolytic, photocatalytic and sonophotocatalytic degradation of methyl orange using TiO2 photocatalyst prepared in heptane with 0.5% gold loading and calcined at 300 oC. Among the 9 catalysts synthesized, TiO2 photocatalyst prepared in heptane with 0.5% gold loading and calcined at 300 oC showed the highest photocatalytic activity. Hence, this catalyst was used in the sonophotocatalytic experiment and the results are shown in Figure 1b. It can be seen that the photocatalytic degradation was significantly higher than that of sonlysis. The efficiency of the combined process is found to be just an additive effect without any synergy. Further details on the characterization of the catalysts and possible reasons for the observed trends in their catalytic efficiencies will be discussed. 13th Meeting of the European Society of Sonochemistry Lviv Polytechnic National University Institutional Repository http://ena.lp.edu.ua

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