Characterisation of colloidal gas aphrons for subsequent use for protein recovery

Abstract

Colloidal gas aphrons (CGAs) were first reported by Sebba (J. Colloid Interface Sci., 35 (4) (1971) 643) as micro bubbles (10–100 μm), composed of a gaseous inner core surrounded by a thin surfactant film, which are created by intense stirring of a surfactant solution. Since then, these colloidal dispersions have been used for diverse applications (clarification of suspensions, removal of sulphur crystals, separation of organic dyes from wastewater, etc.). However, there have been no reports, as yet, of their direct application for protein recovery. In this study, CGAs are created from an anionic surfactant (AOT) and are characterised in terms of stability and gas hold-up for a range of process parameters relevant to their proposed use for protein recovery, at a later stage. A statistical experimental design was developed in order to study the effect of different factors (surfactant concentration, salt concentration, pH, time of stirring and temperature) on the stability and gas hold-up of CGAs. The analysis of results from the experimental design provides predictive statistical models. Stability was found to depend mainly on salt and surfactant concentration. Several interactions are shown to be significant including the time-temperature interaction. Gas hold-up was found to depend mainly on salt and surfactant concentration and time of stirring. Also, results from power measurements are presented and the minimum energy for the formation of CGAs, for one set of solution properties, is determined.