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Transmission electron microscopic observations of nanobubbles and their capture of impurities in wastewater.

Uchida T, Oshita S, Ohmori M, Tsuno T, Soejima K, Shinozaki S, Take Y, Mitsuda K - Nanoscale Res Lett (2011)

Bottom Line: Unique properties of micro- and nanobubbles (MNBs), such as a high adsorption of impurities on their surface, are difficult to verify because MNBs are too small to observe directly.MNBs in pure water and in 1% NaCl solutions were spherical or oval.When we applied this technique to the observation of O2 MNBs formed in the wastewater of a sewage plant, we found the characteristic features of spherical MNBs that adsorbed surrounding impurity particles on their surface.PACS: 68.03.-g, 81.07.-b, 92.40.qc.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Applied Physics, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan. t-uchida@eng.hokudai.ac.jp.

ABSTRACT
Unique properties of micro- and nanobubbles (MNBs), such as a high adsorption of impurities on their surface, are difficult to verify because MNBs are too small to observe directly. We thus used a transmission electron microscope (TEM) with the freeze-fractured replica method to observe oxygen (O2) MNBs in solutions. MNBs in pure water and in 1% NaCl solutions were spherical or oval. Their size distribution estimated from TEM images close to that of the original solution is measured by light-scattered methods. When we applied this technique to the observation of O2 MNBs formed in the wastewater of a sewage plant, we found the characteristic features of spherical MNBs that adsorbed surrounding impurity particles on their surface.PACS: 68.03.-g, 81.07.-b, 92.40.qc.

No MeSH data available.


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Various TEM images of freeze-fractured replica of the wastewater containing O2 MNBs. Each scale bar indicates 100 nm. (a, b) The MNB (850 nm in diameter) located in the center of each picture adsorbed many fine particles (20 nm in diameter) on its surface. The extended picture in (a) depicts the bubble-solution boundary indicating the process by which fine particles were attracted to the bubble surface. In contrast, no fine particles were observed around the MNB. (c) MNBs that captured fine particles were also located on the grain boundary between ice crystallites.
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Figure 5: Various TEM images of freeze-fractured replica of the wastewater containing O2 MNBs. Each scale bar indicates 100 nm. (a, b) The MNB (850 nm in diameter) located in the center of each picture adsorbed many fine particles (20 nm in diameter) on its surface. The extended picture in (a) depicts the bubble-solution boundary indicating the process by which fine particles were attracted to the bubble surface. In contrast, no fine particles were observed around the MNB. (c) MNBs that captured fine particles were also located on the grain boundary between ice crystallites.

Mentions: In contrast, several replica images in the same quenched sample exhibited a relatively wide smooth area similar to that of the pure water sample. In that area, we found some spherical objects that had adsorbed a large number of fine particles on their surface (Figure 5). These spherical objects ranged from 5 to 9 × 10-7 m in diameter, which corresponded to the expected size of the MNBs formed in the solution. The fine particles on the spherical objects (or NBs) were 2 to 3 × 10-8 m in diameter. Since no fine particles were observed around the NB, we postulated that these fine particles were impurities originally included in the wastewater and located around the MNB. Therefore, Figure 5 clearly indicates that MNBs in the wastewater trapped impurities existed around them on their surfaces and concentrated impurities during their residence time until quenching. This is the first direct observation of a typical property of MNBs, that is, MNBs adsorb effectively and concentrate impurities in solutions on their surface, which results in separating impurities from solutions.


Transmission electron microscopic observations of nanobubbles and their capture of impurities in wastewater.

Uchida T, Oshita S, Ohmori M, Tsuno T, Soejima K, Shinozaki S, Take Y, Mitsuda K - Nanoscale Res Lett (2011)

Various TEM images of freeze-fractured replica of the wastewater containing O2 MNBs. Each scale bar indicates 100 nm. (a, b) The MNB (850 nm in diameter) located in the center of each picture adsorbed many fine particles (20 nm in diameter) on its surface. The extended picture in (a) depicts the bubble-solution boundary indicating the process by which fine particles were attracted to the bubble surface. In contrast, no fine particles were observed around the MNB. (c) MNBs that captured fine particles were also located on the grain boundary between ice crystallites.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211361&req=5

Figure 5: Various TEM images of freeze-fractured replica of the wastewater containing O2 MNBs. Each scale bar indicates 100 nm. (a, b) The MNB (850 nm in diameter) located in the center of each picture adsorbed many fine particles (20 nm in diameter) on its surface. The extended picture in (a) depicts the bubble-solution boundary indicating the process by which fine particles were attracted to the bubble surface. In contrast, no fine particles were observed around the MNB. (c) MNBs that captured fine particles were also located on the grain boundary between ice crystallites.
Mentions: In contrast, several replica images in the same quenched sample exhibited a relatively wide smooth area similar to that of the pure water sample. In that area, we found some spherical objects that had adsorbed a large number of fine particles on their surface (Figure 5). These spherical objects ranged from 5 to 9 × 10-7 m in diameter, which corresponded to the expected size of the MNBs formed in the solution. The fine particles on the spherical objects (or NBs) were 2 to 3 × 10-8 m in diameter. Since no fine particles were observed around the NB, we postulated that these fine particles were impurities originally included in the wastewater and located around the MNB. Therefore, Figure 5 clearly indicates that MNBs in the wastewater trapped impurities existed around them on their surfaces and concentrated impurities during their residence time until quenching. This is the first direct observation of a typical property of MNBs, that is, MNBs adsorb effectively and concentrate impurities in solutions on their surface, which results in separating impurities from solutions.

Bottom Line: Unique properties of micro- and nanobubbles (MNBs), such as a high adsorption of impurities on their surface, are difficult to verify because MNBs are too small to observe directly.MNBs in pure water and in 1% NaCl solutions were spherical or oval.When we applied this technique to the observation of O2 MNBs formed in the wastewater of a sewage plant, we found the characteristic features of spherical MNBs that adsorbed surrounding impurity particles on their surface.PACS: 68.03.-g, 81.07.-b, 92.40.qc.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Applied Physics, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan. t-uchida@eng.hokudai.ac.jp.

ABSTRACT
Unique properties of micro- and nanobubbles (MNBs), such as a high adsorption of impurities on their surface, are difficult to verify because MNBs are too small to observe directly. We thus used a transmission electron microscope (TEM) with the freeze-fractured replica method to observe oxygen (O2) MNBs in solutions. MNBs in pure water and in 1% NaCl solutions were spherical or oval. Their size distribution estimated from TEM images close to that of the original solution is measured by light-scattered methods. When we applied this technique to the observation of O2 MNBs formed in the wastewater of a sewage plant, we found the characteristic features of spherical MNBs that adsorbed surrounding impurity particles on their surface.PACS: 68.03.-g, 81.07.-b, 92.40.qc.

No MeSH data available.


Related in: MedlinePlus