| Autor: |
Nirmalkar N; School of Chemical Engineering , University of Birmingham , Edgbaston , Birmingham B15 2TT , U.K., Pacek AW; School of Chemical Engineering , University of Birmingham , Edgbaston , Birmingham B15 2TT , U.K., Barigou M; School of Chemical Engineering , University of Birmingham , Edgbaston , Birmingham B15 2TT , U.K. |
| Jazyk: |
angličtina |
| Zdroj: |
Langmuir : the ACS journal of surfaces and colloids [Langmuir] 2018 Sep 18; Vol. 34 (37), pp. 10964-10973. Date of Electronic Publication: 2018 Sep 04. |
| DOI: |
10.1021/acs.langmuir.8b01163 |
| Abstrakt: |
Bulk nanobubbles are a novel type of nanoscale bubble system. Because of their extraordinary behavior, however, their existence is not widely accepted. In this paper, we shed light on the hypothesis that bulk nanobubbles do exist, they are filled with gas, and they survive for long periods of time, challenging present theories. An acoustic cavitation technique has been used to produce bulk nanobubbles in pure water in relatively large numbers approaching 10 9 bubble·mL -1 with a typical diameter of 100-120 nm. We provide multiple evidence that the nanoentities observed in suspension are nanobubbles given that they disappear after freezing and thawing of the suspensions, their nucleation rate depends strongly on the amount of air dissolved in water, and they gradually disappear over time. The bulk nanobubble suspensions were stable over periods of many months during which time the mean diameter remained unchanged, suggesting the absence of significant bubble coalescence, bubble breakage, or Ostwald ripening effects. Measurements suggest that these nanobubbles are negatively charged and their zeta potential does not vary over time. The presence of such a constant charge on the nanobubble surfaces is probably responsible for their stability. The effects of pH, salt, and surfactant addition on their colloidal stability are similar to those reported in the literature for solid nanoparticle suspensions, that is, nanobubbles are more stable in an alkaline medium than in an acidic one; the addition of salt to a nanobubble suspension drives the negative zeta potential toward zero, thus reducing the repulsive electrostatic forces between nanobubbles; and the addition of an anionic surfactant increases the magnitude of the negative zeta potential, thus improving nanobubble electrostatic stabilization. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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