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Aqueous foams in the presence of surfactant crystals

Binks, Bernard P.; Shi, Hui

Authors

Hui Shi



Abstract

Aqueous foams are used extensively in many fields and anionic surfactants are commonly used foaming agents. However, potential trouble may arise when they are utilized in hard water areas and/or at low temperatures. Anionic surfactants, like sodium dodecyl sulfate (SDS), may precipitate in the form of crystals when the concentration of divalent counterions such as Mg2+ exceeds a certain limit. In an attempt to prepare ultrastable foams containing precipitated crystals, the behavior of SDS in water was systematically investigated as a function of surfactant concentration at different concentrations of Mg(NO3)2 prior to a study of their foam properties. We quantitatively study the conversion of surfactant micelles to crystals and the redissolution of crystals into micelles. It was found that the presence of surfactant crystals reduced the initial foam volume and foam half-life but greatly improved the long-term stability of foams. Foam studies were also conducted for the supernatant and sediment isolated from crystal dispersions so that the importance of surfactant crystals to foam stability could be established. Despite the foamability of a sediment being low, an order of magnitude increase in foam half-life was related to the coverage of bubble surfaces by surfactant crystals. Both rapid cooling and ultrasonication were shown to influence the surfactant crystal shape and size with an impact on foam properties.

Citation

Binks, B. P., & Shi, H. (2020). Aqueous foams in the presence of surfactant crystals. Langmuir : the ACS journal of surfaces and colloids, 36(4), 991-1002. https://doi.org/10.1021/acs.langmuir.9b03862

Journal Article Type Article
Acceptance Date Jan 15, 2020
Online Publication Date Jan 27, 2020
Publication Date Feb 4, 2020
Deposit Date Jan 15, 2020
Publicly Available Date Jan 28, 2021
Journal Langmuir
Print ISSN 0743-7463
Electronic ISSN 1520-5827
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 36
Issue 4
Pages 991-1002
DOI https://doi.org/10.1021/acs.langmuir.9b03862
Keywords Crystals; Sodium dodecyl sulfate; Colloids; Foams; Surfactants
Public URL https://hull-repository.worktribe.com/output/3363026
Publisher URL https://pubs.acs.org/doi/abs/10.1021/acs.langmuir.9b03862

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