TY - JOUR
T1 - Probing Internal Pressures and Long-Term Stability of Nanobubbles in Water
AU - Shi, Xiaonan
AU - Xue, Shan
AU - Marhaba, Taha
AU - Zhang, Wen
N1 - Funding Information:
This research is partially supported by the United States Department of Agriculture (USDA), the National Institute of Food and Agriculture, AFRI project [2018-07549], and the United States Environmental Protection Agency (US EPA) under Assistance Agreement Nos. 83945101 and 84001901 (EPA P3 phase I and II). The USDA and the EPA have not formally reviewed this study. The views expressed in this document are solely those of authors and do not necessarily reflect those of the agencies. The USDA and EPA do not endorse any products or commercial services mentioned in this publication.
Publisher Copyright:
© 2021 American Chemical Society. All rights reserved.
PY - 2021/2/23
Y1 - 2021/2/23
N2 - Nanobubbles (NBs) in liquid exhibit many intriguing properties such as low buoyancy and high mass transfer efficiency and reactivity as compared to large bulk bubbles. However, it remains elusive why or how bulk NBs are stabilized in water, and particularly, the states of internal pressures of NBs are difficult to measure due to the lack of proper methodologies or instruments. This study employed the injection of high-pressure gases through a hydrophobized ceramic membrane to produce different gaseous NBs (e.g., N2, O2, H2, and CO2) in water, which is different from cavitation bubbles with potential internal low pressure and noncondensed gases. The results indicate that increasing the injection gas pressure (60-80 psi) and solution temperatures (6-40 °C) both reduced bubble sizes from approximately 400 to 200 nm, which are validated by two independent models developed from the Young-Laplace equation and contact mechanics. Particularly, the colloidal force model can explain the effects of surface tension and surface charge repulsion on bubble sizes and internal pressures. The contact mechanics model incorporates the measurement of the tip-bubble interaction forces by atomic force microscopy to determine the internal pressures and the hardness of NBs (e.g., Young's modulus). Both the colloidal force balance model and our contact mechanics model yielded consistent predictions of the internal pressures of various NBs (120-240 psi). The developed methods and model framework will be useful to unravel properties of NBs and support engineering applications of NBs (e.g., aeration or ozonation). Finally, the bulk NBs under sealed storage could be stable for around a week and progressively reduce in concentrations over the next 30-60 days.
AB - Nanobubbles (NBs) in liquid exhibit many intriguing properties such as low buoyancy and high mass transfer efficiency and reactivity as compared to large bulk bubbles. However, it remains elusive why or how bulk NBs are stabilized in water, and particularly, the states of internal pressures of NBs are difficult to measure due to the lack of proper methodologies or instruments. This study employed the injection of high-pressure gases through a hydrophobized ceramic membrane to produce different gaseous NBs (e.g., N2, O2, H2, and CO2) in water, which is different from cavitation bubbles with potential internal low pressure and noncondensed gases. The results indicate that increasing the injection gas pressure (60-80 psi) and solution temperatures (6-40 °C) both reduced bubble sizes from approximately 400 to 200 nm, which are validated by two independent models developed from the Young-Laplace equation and contact mechanics. Particularly, the colloidal force model can explain the effects of surface tension and surface charge repulsion on bubble sizes and internal pressures. The contact mechanics model incorporates the measurement of the tip-bubble interaction forces by atomic force microscopy to determine the internal pressures and the hardness of NBs (e.g., Young's modulus). Both the colloidal force balance model and our contact mechanics model yielded consistent predictions of the internal pressures of various NBs (120-240 psi). The developed methods and model framework will be useful to unravel properties of NBs and support engineering applications of NBs (e.g., aeration or ozonation). Finally, the bulk NBs under sealed storage could be stable for around a week and progressively reduce in concentrations over the next 30-60 days.
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U2 - 10.1021/acs.langmuir.0c03574
DO - 10.1021/acs.langmuir.0c03574
M3 - Article
C2 - 33538170
AN - SCOPUS:85100732799
SN - 0743-7463
VL - 37
SP - 2514
EP - 2522
JO - Langmuir
JF - Langmuir
IS - 7
ER -