The development of Fe(III)/TiO(2) catalysts for sonocatalytic degradation of Reactive Blue 4 (RB4) dye in water was carried out using sol-gel method. Their surface morphology, phase transformation and surface characteristics were studied using SEM, XRD and surface analyzer, respectively. Phase transformation from amorphous to anatase occurred at 500°C and transformation of anatase to rutile phase occurred at 700°C. Complete rutile phase was formed at 900°C with corresponding increase in the particle size. Increasing in Fe(III) loading led to a reduction in the anatase phase and with the formation of weaker and broader of diffraction peaks. Surface morphology of the prepared catalyst was clearly observed with increasing calcination temperature. Surface area of the prepared catalyst decreased with increasing calcination temperature or increasing Fe(III) loading. The combination of 0.4 mol% of Fe(III)/TiO(2) with ultrasonic irradiation gave the highest sonocatalytic activity in the removal of RB4 from the aqueous solution. On the other hand, the presence of even small amount of rutile inhibited the catalytic activity of catalyst. 1.5 g/L was the optimum amount of catalyst that led to the highest sonocatalytic degradation of RB4 with an efficiency of 90%. Aeration significantly accelerated the reaction rate. Higher removal at 96% could be achieved with the combination of 0.4Fe(III)/TiO(2) and aeration under ultrasonic irradiation.

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Sonocatalytic degradation of acid red B (ARB) dye was investigated using Fe doped zeolite Y catalysts with the assistance of low frequency (20 kHz) ultrasonic irradiation. Low concentration of Fe ions from different precursors was loaded onto the zeolite using wet impregnation method. Catalytic degradation of ARB dye was found to be accelerated by the reaction between Fe (II) and Fe (III) ions and hydrogen peroxide (H2O2) generated in situ by the ultrasound-mediated dissociation of water molecules. Fe (II)/Y exhibited higher degradation efficiency at the beginning of the reaction but achieved almost similar degradation at the end of the process. The increase of pH significantly decreased the degradation efficiency of ARB dye and strongly affected the leaching and catalyst stability. The highest efficiency was achieved at an initial pH of 3 with nearly 100% degradation in less than 60 min. Both catalysts showed no significant changes in terms of their mean particle sizes before and after reaction. Finally, Fe (III)/Y showed better performance evaluated based on leaching of Fe and also catalyst reusability. Only minor physical changes occurred during the degradation process for four consecutive runs of reaction.

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