The influence of ultrasound at 24 kHz on the heterogeneous aqueous oxidation of phenol over Rub with hydrogen peroxide (H2O2) was studied isothermally at 298 K. Effect of ultrasound irradiation on catalytic properties and performance of RuI3 has been studied in details by means of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), dispersion analyzer and a surface analyzer. Turn over frequency of the catalyst was also calculated. In this work, experimental design methodology was applied to optimize the degradation of phenol in aqueous solution, while minimizing an excessive consumption of chemical reagents. The independent variables considered were the catalyst load and oxidant concentration. The multivariate experimental design allowed the development of empiric non-linear quadratic models for total organic carbon (TOC) removal after 120 and 240 min of the reaction, and the time needed for total hydrogen peroxide consumption, which were adequate to predict responses in all of the range of experimental conditions used. Ruthenium leaching was not detected from samples studied at different stages of the reaction, indicating stability of the chosen catalyst. A reaction scheme involving radical species ((OH)-O-center dot, (HO2)-H-center dot) was proposed to explain phenol conversion. Ultrasound-assisted catalytic oxidation demonstrated nearly two-fold increase in phenol conversion (up to 70%), contrary to 31% obtained during silent process. High catalytic activity of RuI3 associated with isothermal reaction conditions at circum neutral pH was capable to extend the applicability of such catalyst in ultrasound-assisted oxidation processes. (C) 2008 Elsevier B.V. All rights reserved.