One of the most toxic phenolic compounds is 4-Chlorophenol (4CP), It imposes serious dangers to the environment once discharged into water due to its high toxicity, carcinogenic character, persistence in the environment, and low biodegradability [1]. Recently, the researcher was focused on the use of ultrasound as one of the wastewater treatment technologies due to its greater efficiency and easier method to operate [2]. But, a total mineralization of organic pollutants by ultrasound alone is still a difficult task. Hence, a combination of ultrasound and catalyst called as sono-catalyst increases the oxidation of organic compounds under milder conditions compared to the non-catalyzed processes [3]. Among different catalysts, Sr-doped LaMnO3 is particularly of interest due to its proper magnetic, electric, catalytic properties, and non-toxicity [4]. In this study, La0.7Sr0.3MnO3 (LSMO) with nanoparticles a single-crystalline perovskite structure were prepared by a combination of ultrasound and copercipitation. Its average particle size was about 17 nm. This catalyst was characterized by X-ray diffraction, transmisson electron microscopy, Fourier transform infrared spectroscopy. The catalytic performance of the sample for 4CP degradation was evaluated in the presence and in the absence of ultrasound. The degradation has been studied at different temperatures, pH, catalyst dosage, and initial concentration of 4CP for both methods. The results have shown that the degradation efficiency was higher in the presence of ultrasound than the conventional method under mild conditions. More than 88% decrease in the concentration 4CP and 82% decrease in TOC was achieved in a short time of sonication with respect to the longer time required for the conventional method. This behavior could be attributed to the cavitation process, mass transfer on the catalyst, and the surface area of the catalyst which all of them facilitate the removal of pollutant from aqueous solution. In addition, the results indicated that the catalyst without recalcination can be successfully used up to five consecutive cycles with no significant loss in activity in both methods.

Keywords