The Influence of pH and Temperature on the Equilibrium and Dynamic Surface Tension of Aqueous Solutions of Sodium Oleate
2001 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 239, no 1, 209-216 p.Article in journal (Refereed) Published
For aqueous solutions of sodium oleate, the dynamic surface tension (using the maximum bubble pressure technique) and the equilibrium surface tensions (using the du Nouy ring method) were studied. Experiments were carried out within the pH range 7 to 13 and at temperatures from 20 to 60 degreesC. From the equilibrium surface tension studies at 25 degreesC, a wide variation in surface activity was found to occur in the premicellar concentration range, depending on pH and oleate concentration, and this was explained on the basis of the formation of strongly surface-active premicellar species. It was also shown that the critical micelle concentration (cmc) of the system increased with pH within the pH range 7-12, Dynamic surface tension experiments were carried out from 20 to 60 degreesC at concentrations beyond the cmc in alkaline solutions, and the adsorption kinetics at the air/solution interface were analyzed using established theoretical diffusion models. From these data, the effective diffusion coefficients (D-eff) for the oleate species were determined and the presence of an interfacial activation barrier in the diffusion process was confirmed. It was found that the D-eff values obtained within the temperature range from 40 to 60 degreesC at 2-3 mM were in general agreement with previously reported values for the oleate dimer obtained by pulse-gradient FT-NMR. Furthermore, D-eff significantly increased with temperature and also increased with concentration at higher temperatures (> 40 degreesC).
Place, publisher, year, edition, pages
2001. Vol. 239, no 1, 209-216 p.
dynamic surface tension, equilibrium surface tension, sodium oleate, diffusion coefficient
IdentifiersURN: urn:nbn:se:kth:diva-9037DOI: 10.1006/jcis.2000.7543ISI: 000169533100026OAI: oai:DiVA.org:kth-9037DiVA: diva2:14578
QC 201009232006-01-272006-01-272010-09-23Bibliographically approved