Studies in Solvent Extraction Using Polyaphrons. I. Size Distribution, Stability, and Flotation of Polyaphrons

Abstract

Abstract Predispersed solvent extraction (PDSE) is a promising technique for the treatment of wastewater containing low solubility, hydrophobic contaminants. A stable predispersed organic solvent in the form of polyaphrons of very small diameter results in high surface areas with a minimum energy requirement for mass transfer of solutes from the aqueous phase to the organic solvent. PDSE should greatly improve the performance of a conventional extraction process. This paper focuses on the characterization and size distributions of polyaphrons. Polyaphrons were generated using different cationic, anionic, and nonionic surfactants in water and an oil-soluble nonionic surfactant. Kerosene was used as the organic solvent to form the polyaphrons. Size distributions were obtained using a particle size analyzer. The optimal instrument parameters (sample quantity, optical parameters, run time, etc.) were identified for these measurements. The size distribution based on volume fraction was found to show a bimodal behavior, with peak size maxima between 1–3 and 10–30 μm for all the polyaphrons. The effects of different surfactant types, surfactant concentrations, and storage times on the size distribution spectrum of polyaphrons were studied. The size distribution of different polyaphrons before and after flotation in an aqueous column using colloidal gas aphrons (CGAs) was also studied. Flotation was deduced to occur as a result of electrostatic forces between the CGAs and polyaphrons.