Department of Materials and Life Science, Faculty of Science and Technology, Shizuoka Institute of Science and Technology, 2200-2 Toyosawa, Fukuroi, Shizuoka 437-8555, Japan.
Department of Materials and Life Science, Faculty of Science and Technology, Shizuoka Institute of Science and Technology, 2200-2 Toyosawa, Fukuroi, Shizuoka 437-8555, Japan.
Ultrason Sonochem. 2021 Mar;71:105354. doi: 10.1016/j.ultsonch.2020.105354. Epub 2020 Sep 28.
Ionic surfactants tend to accumulate in the interfacial region of ultrasonic cavitation bubbles (cavities) because of their surface active properties and because they are difficult to evaporate in cavitation bubbles owing to their extremely low volatilities. Hence, sonolysis of ionic surfactants is expected to occur in the interfacial region of the cavity. In this study, we performed sonochemical degradation of surfactants with different charge types: anionic, cationic, zwitterionic, and nonionic. We then estimated the degradation rates of the surfactants to clarify the surfactant behavior in the interfacial region of cavitation bubbles. For all of the surfactants investigated, the degradation rate increased with increasing initial bulk concentration and reached a maximum value. The initial bulk concentration to obtain the maximum degradation rate had a positive correlation with the critical micelle concentration (cmc). The initial bulk concentrations of the anionic surfactants were lower than their cmcs, while those of the cationic surfactants were higher than their cmcs. These results can be explained by the negatively charged cavity surface and the effect of the coexisting counterions of the surfactants.
离子型表面活性剂由于其表面活性性质，以及由于其挥发性极低而难以在空化泡中蒸发，因此往往会在超声空化泡的界面区域积聚。因此，预计离子型表面活性剂将在空化泡的界面区域发生超声降解。在这项研究中，我们对具有不同电荷类型的表面活性剂（阴离子型、阳离子型、两性离子型和非离子型）进行了超声化学降解。然后，我们估算了表面活性剂的降解速率，以阐明表面活性剂在空化泡界面区域的行为。对于所有研究的表面活性剂，降解速率随初始本体浓度的增加而增加，并达到最大值。获得最大降解速率的初始本体浓度与临界胶束浓度（cmc）呈正相关。阴离子表面活性剂的初始本体浓度低于其 cmc，而阳离子表面活性剂的初始本体浓度高于其 cmc。这些结果可以通过带负电荷的空化泡表面和表面活性剂共存抗衡离子的影响来解释。
