Effect of ultrasonic irradiation on the catalytic activity and stability of goethite catalyst in the presence of H2O2 at acidic medium

The objective of this research is to examine the effect of ultrasonic irradiation (35 kHz) on the catalytic activity and stability of goethite powder (alpha-FeOOH) in the presence of H2O2 at pH 3. The catalytic activity of the catalyst was investigated on the decolorization of Direct Orange 39 (DO39) azo dye as a model pollutant, and the stability of the catalyst was examined by measuring contemporary dissolved total iron concentration. The decolorization of dye was strongly enhanced by ultrasonic irradiation on Fenton-like process (alpha-FeOOH/H2O2). The kinetics of decolorization obeys first-order reaction and the rate constant was found to be 0.0189 min(-1). The effect of alpha-FeOOH and H2O2 (2.5-15 g/L) dosage on the decolorization and iron dissolution was investigated and found to increase the decolorization rate with increasing dosage. However, both dosages did not influence the iron dissolution. The catalytic reusability was investigated in up to four successive cycles, and was found that the catalytic efficiency did not decrease appreciably. The effect of ultrasonic irradiation on the catalyst composition, surface area, pore volume, and pore size has been investigated and discussed in each cycle. The structure of the catalyst before and after four cycles was investigated using X-ray diffraction (XRD), cold-field emission scanning electron microscope (FESEM). The mechanism of degradation was discussed. It is concluded that ultrasonic irradiation in the presence of alpha-FeOOH and H2O2 is an efficient process and that the goethite is a promising catalyst for the abatement of dye pollutants in wastewater.