(125i) Analysis of the Hydrolysis Process in Sodium Dodecyl Sulfate Solutions Via Surface Tension Isotherms
- Conference: AIChE Annual Meeting
- Year: 2020
- Proceeding: 2020 Virtual AIChE Annual Meeting
- Group: Engineering Sciences and Fundamentals
- Time: Tuesday, November 17, 2020 - 10:00am-10:15am
Sodium dodecyl sulfate (SDS) is one of the most studied anionic surfactants in the literature and is known to be inherently contaminated by the long-chain alcohol, n-dodecanol, which is a product of SDS hydrolysis that is more surface-active than SDS. Trace amount (~0.2 mol%) of dodecanol in solution has an enormous impact on the resulting surface tension with its coverage yielding values of more than 80% of the total coverage. Methods of estimating the bulk concentration of the contaminant from surface tension readings have been developed over the years. However, there is a gap in knowledge related to how hydrolysis proceeds at ambient conditions of storage and aging of the sample. Investigation of how the alcohol concentration increases with time and its impact on the resulting surface monolayer is a key factor in understanding the behavior of more complex interfacial systems such as particle/surfactant mixtures. In a number of studies available SDS is used as received; therefore, it is unclear what the role of impurity presence is on the reported results. In addition, the presence of electrolyte enhances the SDS surface activity and influences the rate of reaction. In this work, we have examined the aging of SDS solutions in presence of different electrolyte concentrations. The variation in dodecanol content through aging is examined using the experimentally obtained surface tension isotherms that are analyzed via a theoretical model developed in the literature for determining small contents of dodecanol. Our goal is to clarify the role of salt and its concentration on both hydrolysis process and surface coverage as aging proceeds. The results obtained from these studies provide valuable insights on assays that involve SDS solutions and have application in more complex interfacial systems.