Experimental and modeling investigations of styrene adsolubilization in nonionic surfactant admicelles.

摘要

With amphipathic structure, surfactants may adsorb at an interface and form ordered aggregates. Adsolubilization, solubilization of sparingly soluble compounds in adsorbed surfactant aggregates, has demonstrated applications in such diverse fields as composite materials, pharmaceutics, and separation processes. Styrene is a typical sparingly soluble compound and widely used monomer in polymerization. Investigations of styrene adsolubilization will enhance our knowledge on this phenomenon and help us to develop various applications.; This work investigated adsolubilization of styrene by different nonionic surfactants, and mixed surfactants, on amorphous precipitated silica. The effect of the addition of lipophilic linkers (long chain linear alcohols) on adsolubilization was also checked. The styrene adsolubilization isotherms were compared to find the impact of the different factors.; The experimental results show that at concentrations below the critical micelle concentration (CMC), adsolubilization increased with increasing bulk solute concentration. The adsolubilization capacity (Adsolubilization/Adsorption) is affected by several factors including: surfactant structure, ratios of mixed surfactants and the presence of additives such as lipophilic linkers and other organics. Several ways to improve the capacity were proposed with demonstrated impacts of up to 100% increase. The linker that will perform best in a given system for promoting adsolubilization was suggested and the results compared to those for solubilization. Mixed surfactant systems are far more sensitive to the concentrations change of surfactants than single ones. However, much less of a second surfactant is needed to achieve that same increase in adsolubilization than for a lipophilic linker.; A model based on the BET adsorption isotherm equation was developed and can be used to predict adsolubilization performance in similar systems given very limited experiment support. The model may also be easily related to existing partition coefficients in order to compare adsolubilization and imply information about the location of solute in the admicelle.; The results of this study provided insights for styrene adsolubilization at the water-silica interface and increase our ability to "tune" adsolubilization for specific applications.