Effect of pH and NaCl Concentration on the Stability of Surfactant-Free Foam Films

Wang, Liguang and Yoon, Roe-Hoan (2009) Effect of pH and NaCl Concentration on the Stability of Surfactant-Free Foam Films. Langmuir, 25 1: 294-297. doi:10.1021/la802664k

Author Wang, Liguang
Yoon, Roe-Hoan
Title Effect of pH and NaCl Concentration on the Stability of Surfactant-Free Foam Films
Journal name Langmuir   Check publisher's open access policy
ISSN 0743-7463
Publication date 2009-01
Sub-type Article (original research)
DOI 10.1021/la802664k
Volume 25
Issue 1
Start page 294
End page 297
Total pages 4
Place of publication Washington, D.C.
Publisher American Chemical Society
Language eng
Subject 0904 Chemical Engineering
Abstract The stability of surfactant-free foam films was studied in NaCl solutions of varying concentration and pH using the thin film pressure balance (TFPB) technique. In pure water, it was not possible to produce foam films due to weak film elasticity and the strong attractive hydrophobic force in foam films, despite the presence of strong repulsive double-layer force. In the presence of a very small amount of an electrolyte, however, the hydrophobic force was dampened, allowing metastable foam films to form. As the NaCl concentration was raised above 10-6 M, the film stability diminished as a result of double-layer compression. The TFPB technique was also used to measure the equilibrium film thicknesses (He) in 10-5 M NaCl solutions of varying pH; He reached a maximum of approximately 130 nm at pH 6.0-7.3, and decreased on either side of this pH range as a result of the increased ionic strength caused by the HC1 and NaOH added to control the pH. The hydrophobic force in surfactant-free foam films was maximum at pH 7.3, where the concentration of electrolytes, including that of H2CO3 species, was minimum. © 2009 American Chemical Society.
Keyword Double-layer forces
Film elasticities
Hydrophobic forces
Ionic strength
Ionization of liquids
Metastable foams
NaCl concentrations
Nacl solutions
pH effects
pH ranges
Pure waters
Sodium chloride
Surface active agents
Thin film pressure balances
Q-Index Code C1
Q-Index Status Provisional Code

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Chemical Engineering Publications
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Citation counts: TR Web of Science Citation Count  Cited 5 times in Thomson Reuters Web of Science Article | Citations
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Created: Thu, 23 Sep 2010, 11:56:23 EST by Ms May Balasaize on behalf of Faculty Of Engineering, Architecture & Info Tech