International Conference on Emerging Trends in Engineering and Management (ICETEM-2014)

Abstract: The degradation of trace amounts of the cationic dye RhodamineB (RhB) pollutantin water in the presence and absence of catalystis investigated undermicrowave (MW) irradiation.The degradation is much faster compared to identical thermal conditions thus suggesting that the MW effect is not just heating the reaction system. The presence of semiconductor oxide catalyst ZnO which is known to enhance the degradation of many organic chemical pollutants photocatalyticallyenhances the degradation in presence of MW as well. Addition of H₂O₂ enhances the MW-assisted degradation significantly in the presence as well as absence of catalyst. The increased efficiency can be attributed to increased formation of reactive free radicals and their interaction with the dye. The MW radiation may not be affecting the surface characteristics of the semiconductor as in the case of other AOPs. The effect of different parameters, viz. catalyst dosage, concentration of the dye, pH, MW power and H₂O₂ concentration on the degradation rate is evaluated and optimum parameters for the mineralization of the pollutant are identified.The degradation is favored under extreme acidic and alkaline conditions in both thermal and MW processes. There is considerable synergy in the MW/ZnO/H₂O₂ process compared to the respective individual processes.

Keywords: Hydrogen peroxide, microwave radiation, rhodamine B,zinc oxide.

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Abstract: In this present work, zirconium pillared montmorillonite and rare earth exchanged zirconium pillared montmorillonite were prepared and their catalytic performance was studied for the Friedel –Crafts Benzylation reaction. The rare earths selected are Lanthanum (La), Cerium(Ce) and Samarium(Sm). The physicochemical characterization was performed using X-ray diffraction(XRD), BET surface area measurement(BET-SA) and scanning electron microscopy(SEM). The surface acidity of the prepared systems was studied by stepwise temperature programmed desorption (TPD) of ammonia. The catalytic activity of the prepared systems was studied by selecting Friedel-Crafts alkylation reaction of benzene with benzyl chloride. Enhancement of surface area, acidity and shift of XRD peak towards lower 2θ region suggest efficient pillaring. Zirconium pillared clays at room temperature was found to be very effective catalysts for the catalytic benzylation of benzene with benzyl chloride. Among the various rare earth exchanged forms, the Sm exchanged Zr pillared montmorillonite shows the highest activity and the least activity is shown by Ce exchanged one.
Keywords : Friedel-Crafts Benzylation, Pillared clays, rare earths, zirconium pillared montmorillonite,

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Abstract: Sono, photo and sonophotocatalysis are major Advanced Oxidation Processes (AOP) under intensive investigation as potential technologies for the removal of trace pollutants from water.The techniques involve the formation and participation of Reactive Oxygen Species (ROS) like .OH, HO2., O2- ., H2O2 etc. Among these, H2O2 is the most stable and is also a precursor for the reactive free radicals. Current investigations on the TiO2 mediated sonocatalytic degradation of phenol pollutant in water confirm our earlier findings using ZnO catalyst that H2O2 formed insitu cannot be quantitatively correlated with the degradation of the pollutant. The concentration of H2O2 formed does notincrease corresponding to phenol degradation and reaches a plateau or varies in a wave-like fashion (oscillation) with well defined crests and troughs, indicating concurrent formation and decomposition. The number of maxima and minima or their precise occurrence at any point in time is unpredictable and inconsistent, indicating the complexity of the free radical process. The influence of various reaction parameters on the oscillation are identified and investigated in detail.
Keywords- Hydrogen peroxide, oscillation, sonocatalysis, titanium dioxide.

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Abstract: The application of microwave (MW) catalysis using MnO2 as catalyst for the removalof trace amounts of the dianionicdye Indigocarmine (IC) from wateris investigated. Comparison of thermal and MW initiated degradation under identical conditions show that the MW degradation is much faster thus suggesting that the MW effect is not just heating the reaction system. The presence of semiconductor oxide catalysts ZnO or TiO2which are known to enhance the degradation in photocatalysisisnot effective in the presence of MW. Addition of H2O2 inhibits the MW-assisted degradation initially. This is attributed to the absorption of MW by H2O2 and its degradation to inactive H2O and O2. Further, H2O2 consumes some of the reactive .OH radicals which could have been beneficially used by the IC for its degradation. The microwave radiation may not be affecting the surface characteristics of the semiconductor as in the case of other AOPs even though the lattice oxygen removed from the catalyst plays significant role. This lattice oxygen vacancy is later replenished by dissolved oxygen taking MnO2 to its original composition. The degradation is maximum under extreme acidic and alkaline conditions in both thermal and MW processes. H2O2 formed in the reaction undergoes concurrent formation and decomposition resulting in oscillation in its concentration though the phenomenon is not consistently reproducible.The observations are analysed and a general mechanism is proposed.
Key words- Hydrogen peroxide, indigo carmine, manganese dioxide, microwave

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Abstract: The influence of palladium loading on titania nanostructures with three different morphologies viz., cubes, spheres and rods was studied. Nanotitania was synthesized by microwave irradiation method. Nano-sized palladium particles were loaded on synthesized titania nanostructures by metal sol method. As-synthesized TiO2 and Pd-TiO2 were characterized by XRD, UV-visible spectroscopy, BET surface area, PLand TEM techniques. Photocatalytic degradation property of titania and palladium loaded titania nanostructures were investigated using the dye methylene blue under sunlight. The dye degradation capabilitiesof nano-sized Pd-TiO2catalysts were found superior to bare TiO2 nanostructures. The higher photoactivity of Pd-TiO2 can be ascribed to the effect of enhancement of electron hole separation by the Pd deposits acting as electron traps on the TiO2 surface.
Key words: Dye degradation, microwave irradiation, photocatalysis, Pd-TiO2,, titania.

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