Sonocatalytic degradation of Reactive Yellow 39 using synthesized ZrO₂ nanoparticles on biochar

ZrO₂-biochar (ZrO₂-BC) nanocomposite was prepared by a modified sonochemical/sol–gel method. The physicochemical properties of the prepared nanocomposite were evaluated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray fluorescence, Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller model. The sonocatalytic performance of ZrO₂-BC was investigated in sonochemical degradation of Reactive Yellow 39 (RY39). The high observed sonocatalytic activity of the ZrO₂-BC sample could be interpreted by the mechanisms of sonoluminescence and hot spots. Parameters including ZrO₂-BC dosage, solution pH, initial RY39 concentration and ultrasonic power were selected as the main operational parameters and their influence on RY39 degradation efficiency was examined. A 96.8% degradation efficiency was achieved with a ZrO₂-BC dosage of 1.5 g/L, pH of 6, initial RY39 concentration of 20 mg/L and ultrasonic power of 300 W. In the presence of ^[rad]OH radical scavengers, RY39 degradation was significantly inhibited, providing evidence for the key role of hydroxyl radicals in the process. The sonodegradation intermediates were identified using gas chromatography-mass spectroscopy and the possible decomposition route was proposed.