For example, they looked at how different levels of ultrasound affected the sonophotocatalytic degradation of sulfadiazine (SDZ) onto a composite of Zn-Cu-Mg mixed metal hydroxide (MMH) @ g-C3N4 @ microfibrillated carboxymethyl cellulose (MFC3) . Degradation accelerated with rising power values, because more cavitational microbubbles were generated, which in turn collapsed and produced more reactive oxygen species (ROS) . In a similar vein, the sonophotocatalytic degradation of AB dye dye onto ZnO/persulfate composites was studied in relation to ultrasound power (100-300 W L ~1). Increasing the ultrasound power resulted in better cavitational formation and the generation of more ROS, leading to higher degradation performance of the dye . Several others have made the same observation. The most important thing is to determine how much ultrasonic power to use so that degradation performance is maximized. A small power output might not be enough to cause cavitational phenomena to produce enough reactive species. As a result, degradation rates are reduced and pollutant removal efficiency is diminished. However, problems like catalyst deactivation or damage might result from ultrasonic power levels that are too high. The mechanism of ultrasonic cavitation and the subsequent creation of "hot spots" is shown schematically in Fig. .