Stability of foams and froths in the presence of ionic and non-ionic surfactants |
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| Affiliation: | 1. Southern Federal University, Institute of Mathematics, Mechanics and Computer Science, Milchakova Street 8a, Rostov-on-Don 344090, Russia;2. Department of Structures for Engineering and Architecture, University of Naples – Federico II, Via Claudio 21, 84125 Napoli, Italy;1. School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore;2. Singapore Membrane Technology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore;3. Interdisciplinary Graduate School, Nanyang Technological University, Singapore;1. Institute of Chemical Biology and Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom;2. Department of Chemical Engineering, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom;3. Procter & Gamble, Newcastle Innovation Centre, Longbenton, Newcastle NE12 9TS, United Kingdom;1. The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand;2. Faculty of Horticulture, Graduate School of Horticulture, Chiba University, Chiba, Japan;3. Department of Chemical Engineering, Faculty of Engineering, Thammasat University, Pathumthani, Thailand;4. Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok, Thailand |
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| Abstract: | The thin film pressure balance (TFPB) technique was used to measure the kinetics of thinning of single foam films and disjoining pressures in the presence of sodium dodecyl sulfate (SDS) and electrolyte (NaCl). The results were analyzed in view of the Reynolds equation to determine the role of surface forces in film thinning. It was found that film thinning is controlled by surface forces at thicknesses below approximately 200 nm. It was found also that hydrophobic force plays an important role particularly at low SDS and NaCl concentrations. The values of the hydrophobic force constant (K232) estimated from the film thinning experiments were used to predict the disjoining pressure isotherms using the extended DLVO theory, which were found to be in excellent agreement with experiment. The TFPB technique was also used to measure the equilibrium thicknesses (He) of the foam films stabilized by a non-ionic surfactant, n-octanol, in the presence of NaCl. At a given ionic strength, He increased noticeably with increasing octanol concentration at very low concentrations. This observation suggests that hydrophobic force is maximum in the absence of surfactant and decreases with increasing surfactant concentration. The results obtained with the single foam films were used to explain the stability of the three-dimensional foams. |
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