Observing the Effects of Temperature and Surface Roughness on Cetyltrimethylammonium Bromide Adsorption Using a Quartz-Crystal Microbalance with Dissipation Monitoring |
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Authors: | Joshua J Hamon Alberto Striolo Brian P Grady |
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Affiliation: | 1. School of Chemical, Biological and Materials Engineering and Institute of Applied Surfactant Research, University of Oklahoma, 100 East Boyd Street, Norman, OK, 73019 USA;2. Department of Chemical Engineering, University College London, London, WC1E 7JE UK |
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Abstract: | The effects of temperature and surface roughness on the mass and viscoelasticity of an adsorbed surfactant layer were monitored using a quartz crystal microbalance with dissipation monitoring (QCM-D). Adsorption isotherms at 30, 40, 50, and 60 °C and at two different roughnesses on gold were measured for cetyltrimethylammonium bromide (CTAB). All isotherms displayed an increase in mass and dissipation as surfactant concentration was increased to its critical micelle concentration (CMC). Above the CMC, adsorption reached a peak followed by a slight decrease to a plateau at the equilibrium adsorption value. As the temperature was increased, the adsorbed mass above the CMC decreased. The adsorbed mass decreased further by increasing substrate roughness, while the dissipation remained unchanged within experimental uncertainty. Dynamic adsorption experiments were also conducted at various temperatures for select concentrations above and below the CMC, providing evidence for the importance of different adsorption mechanisms as a function of both surfactant concentration and surface roughness. |
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Keywords: | Adsorption isotherm Cationic surfactants Surface activity Adsorption kinetics |
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