Prediction of the cloud point of polyethoxylated surfactants and their mixtures by the thermodynamic model of Flory-Huggins-Rupert

Abstract

The cloud point curves of polyethoxylated surfactants are established experimentally. These experimental data are preliminary to the development of the cloud point extraction process, which appears as an interesting alternative to the usual solvent extraction unit operation. Starting from the thermodynamic model developed by Flory and Huggins for phase separation of polymer aqueous solutions, this paper aims at the prediction of cloud point curves. In this work, Rupert’s approach is extended to commercial nonionic surfactants, mixtures of homologous species, namely a few alkylphenol and alcohol ethoxylates. The limit of such an approach is clearly demonstrated, provided that a fitting parameter is finally required for a successful model application to pilot-plant manufactured surfactants, like C₈ΦE_n (n = 7.5, 10, 12), C₉ΦE_n (n = 8, 10, 12), C₁₂E₄, C₁₂E₆ and commercial Tergitol 15-S-7 (linear C₁₂-C₁₄ secondary alcohol with an average of 7 ethylene oxide units).GRAPHICAL ABSTRACT

Keywords:

• Polyethoxylated surfactants
• cloud point
• Flory-Huggins-Rupert approach
• demixing curves
• modeling