Effect of microbubble diameter, alkaline concentration and temperature on reactive oxygen species concentration

Abstract

BACKGROUND In comparison with ordinary bubbles, microbubbles exhibit low floating rate and high surface charge density. More importantly, microbubbles shrink gradually and the gas–liquid interface charges congest significantly, generating large surface potential and energy, which promotes the formation of reactive oxygen species (ROS) when microbubbles eventually collapse. In this study, size‐controllable microbubbles were introduced to alkaline solutions by titanium microporous filters, and the effects of microbubble diameter, alkaline concentration and temperature on the formation of ROS were examined. RESULTS Maximum ROS concentration was obtained by using a microporous filter with average pore size of 25 µm and 40 µm in NaOH and KOH solutions, respectively. Further, with increase in alkaline concentration and temperature, the formation of ROS both exhibited parabolic trends, and optimal temperature for ROS formation was determined to be 65 °C. The maximum ROS concentration was 1.05 mmol L−1 and 3.51 mmol L−1 in NaOH and KOH solutions, respectively, after aerating for 60 min. CONCLUSION The formation of ROS is dependent on the bubble size and solution composition and is influenced by both temperature and alkaline concentration. The results further extend the range of ROS application and provide references for ROS regulations in alkaline media. © 2016 Society of Chemical Industry

Generation Mechanism of Hydroxyl Free Radicals in Micro–Nanobubbles Water and Its Prospect in Drinking Water

“…(4) Temperature: The temperature also has a role in − OH generation by MNBs. Yu et al explained that in an alkaline MNB solution, the ROS concentration first increased and then decreased with the temperature rise [110]. By this effect, a parabolic trend was shown, where the ROS concentration reached its maximum at 65 • C (Figure 3E).…”

“…(3) Bubble size: The bubble size also plays a crucial role in the generation of •OH by MNBs. Yu et al reported that titanium microporous filters to control the size of MNBs can be used to study the effect of their size on the concentration of reactive oxygen species (ROS) [110]. The results showed that the dependence of the ROS concentration on the size of microporous filters induced a quasi-parabolic change.…”

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.…”

Oxidative Capacity of Oxygen Nanobubbles and Their Mechanism for the Catalytic Oxidation of Ferrous Ions with Copper as a Catalyst in Sulfuric Acid Medium

“…The results showed that all oxygen NB suspensions prepared under various preparation conditions could produce ·OH to cause the degradation of MB, and the degradation kinetics of MB showed a common trend in all of the experimental groups, i.e., MB had a relatively rapid degradation rate in the initial stage, while the degradation rate gradually became slower thereafter. This trend may be due to the different characteristics of oxygen NBs in the suspensions prepared under different preparation conditions, such as particle size distribution, ζ-potential, and concentration, which are the determining factors for the generation rate and yield of ·OH from the collapse of oxygen NBs . The rapid destabilization of NBs is the key to the generation of ·OH, while the combined effect of the above-mentioned characteristic factors of oxygen NBs prepared under different preparation conditions will ultimately affect the stability of NBs.…”

“…This trend may be due to the different characteristics of oxygen NBs in the suspensions prepared under different preparation conditions, such as particle size distribution, ζ-potential, and concentration, which are the determining factors for the generation rate and yield of •OH from the collapse of oxygen NBs. 37 The rapid destabilization of NBs is the key to the generation of •OH, while the combined effect of the above-mentioned characteristic factors of oxygen NBs prepared under different preparation conditions will ultimately affect the stability of NBs. Thus, the common trend of the faster and then slower degradation rate is caused by the difference in the amount of • OH exposure triggered by the collapse of bubbles with different properties.…”