La0.7Sr0.3MnO3 (LSMO) nanoparticles with a perovskite structure were prepared by a combination of ultrasound and co-precipitation method. The synthesized catalyst was characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy. The catalytic performance of the catalyst was evaluated for the degradation of 4-chlorophenol in the presence and in the absence of ultrasound. The degradation has been studied at different temperatures, pH, catalyst dosage, and initial concentration of 4-chlorophenol. The results have shown that the degradation efficiency was higher in the presence of ultrasound than its absence under the mild conditions. More than 88% decrease in the concentration and 85% decrease in the TOC for 4-chlorophenol could be achieved in a short time of sonication with respect to the conventional method. This behavior could be attributed to the cavitation process which followed by a high mass transfer on the catalyst with high surface area. These conditions led to facilitate the removal of pollutant from aqueous solution. The results also indicated that the catalyst without recalcination can be used successfully up to five consecutive cycles without any significant loss in activity in the presence and in the absence of ultrasound. In addition, the most important is the magnetic property of the nanoparticles which separated easily from aqueous solution by an external magnetic field.

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