Solubilization of nonaqueous phase liquids and their mixtures in micellar solutions of ethoxylated nonionic surfactants.
Diallo, Mamadou Samba
1995
Abstract
The work described in this dissertation is an experimental and theoretical investigation of the solubilization of nonaqueous phase liquids (NAPLs) and their mixtures in micellar solutions of ethoxylated nonionic surfactants. The basic premise of this dissertation is that the two site model of solubilization provides a unifying framework for assessing the relationships between solubilization capacity and NAPL and surfactant molecular properties in pure and mixed NAPL systems. This model is predicated upon the fact that (i) an ethoxylated nonionic surfactant micelle consists of a hydrophobic core and a polyoxyethylene (POE) shell separated by a sharp interface and (ii) nonpolar and polar NAPLs are predominantly solubilized in the micellar core and POE shell, respectively. The research efforts in this dissertation are structured around three tasks: pure component solubilization, correlation development and binary solubilization. The effect of surfactant hydrophile lipophile balance (HLB) on the molar solubilization ratio (MSR) of four aliphatic NAPLs five aromatic and two chlorinated alkenes in 0.01 M micellar solutions of dodecyl alcohol ethoxylates at 25$\sp\circ$C are examined in the single component solubilization studies. Micellar core volume, NAPL molar volume and the extent of dispersion interactions between NAPL molecules and surfactant alkyl groups are shown to control the MSRs of the aliphatic NAPLs. Conversely, the MSRs of the aromatic NAPLs/chlorinated alkenes are shown to depend on micellar volume and specific interactions between NAPL molecules and ethylene oxide (EO) head groups. Consistent with the underpinnings of the two site model, two types of correlation are formulated and evaluated in this dissertation: a dispersion interaction based (DIB) correlation and a specific interaction based (SIB) correlation. The DIB correlation is restricted to NAPLs that are predominantly solubilized in the micellar care of ethoxylated nonionic surfactant micelles. The SIB correlation describes the more general case of NAPLs that are solubilized in both the core and POE shell of ethoxylated nonionic surfactant micelles. The evaluation shows that both correlations give adequate estimates of NAPL micelle-water partition coefficient in dilute solutions of ethoxylated nonionic surfactants. In the binary solubilization studies, three mixtures of NAPLs with similar average loci of solubilization and five mixtures of NAPLs with differing average loci of solubilization are evaluated. For NAPLs with similar loci of solubilization, a mutual suppression of solubilization is observed. This behavior is attributed to NAPL competition for the micellar core/POE shell volume and/or to the non-ideal behavior of the NAPL mixtures and micellar phases. Both enhancement and mutual suppression of solubilization are observed in the binary mixtures of the NAPLs with differing loci of solubilization. The enhancement is attributed to a solubilization induced increase of micellar volume.Other Identifiers
(UMI)AAI9542826
Subjects
Biology, Molecular Chemistry, Biochemistry Environmental Sciences
Types
Thesis
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