Effects of Surface Tension on the Stability of Surface Nanobubbles

Abstract

The existence of surface nanobubbles has already been confirmed by variable detection methods, but the mechanism of their extraordinary stability remains unclear and has aroused widespread research interest in the past 2 decades. Experiments and theoretical analyses have tried to account for these stabilities such as the very long lifetime, very high pressure and very small contact angle. Attractive hydrophobic potential was applied to complement the pinning-oversaturation theory and successfully explain the survival of surface nanobubbles in undersaturation environment by some researchers. However, the survival of nanobubbles on hydrophilic surface still requires sizeable oversaturation. In this paper, we introduce the variable surface tensions, namely Tolman-dependence and state-dependence, and show that they effectively promote the stability of nanobubbles. The decrease in surface tension can lead to larger contact angle and even make the nanobubbles survivable on the highly hydrophilic surface. In Tolman-dependence, the changing rate in the contact angle evolution slows down, which is more obvious when the bubble size is close to the Tolman length. The contact angle is also getting larger in the state-dependence, and the increase of the gas saturation degree is beneficial to the stability of surface nanobubbles. With the gas saturation ratio of 3, the bubbles on the quite hydrophilic surface can also be stable, while grow up on the hydrophobic surface. The variable surface tensions weaken the need of saturation degree for the surface nanobubbles’ stability.

High Recovery of Ceramic Membrane Cleaning Remediation by Ozone Nanobubble Technology

“…The physical modification significantly influences the further process of ROS generation. − We rationalize that the conventional thermodynamics of the bubble collapse phenomenon led to ozone breakdown. Furthermore, this process comprises three sequential stages, namely, initiation, propagation, and termination.…”

“…Ozone is a promising oxidant in NB systems considering the high reduction potential. Additionally, in the ozone-NB system, ROS could potentially be generated not only by water pyrolysis but also by ozonation reaction through an indirect way. − NBs act as a physical barrier, effectively encapsulating the contaminating layers on its surface. − When contamination-encapsulated, the oxidant would oxidize it. Compared to larger bubbles, ozone-based NBs produced by NB generators exhibit a longer lifetime in the water column .…”

Combination of ozone-based advanced oxidation process and nanobubbles generation toward textile wastewater recovery

“…The physicochemical concept of NB technology is slightly comparable to the AOP method. At a glance, NB facilitates the formation of a physical barrier such that a contaminant layers can be encapsulated by the bubble surface (Pan et al, 2021;Suvira and Zhang, 2021;Inoue et al, 2022;Selihin and Tay, 2022) thereby generating ROS efficiently (Fan et al, 2023). The formation of ROS plays a vital role in degrading organic compounds that are present in the wastewater (Mishra et al, 2017).…”

Estimating the Pinning Force of Surface Nanobubbles Based on Trapped Nanobubble Protruding

“…Surface nanobubbles are typical gaseous domains that attach at the solid–liquid interface, and the morphology, − formation methods, − ,− influencing factors, − observation techniques, − ,− stability, − and potential applications − of surface nanobubbles have been extensively investigated over the past two decades. In these studies, the remarkable thermodynamic stability and abnormally small contact angle (gas phase) of surface nanobubbles are still a hot topic.…”