Foam separation of ethylhexadecyldimethylammonium bromide.

Abstract

The adsorption of ethylhexadecyldimethylammonium bromide (EHDA-Br) at liquid-air interfaces generated by bubbling a constant stream of air through an aqueous solution was determined with a 2 in. diameter foram separation column equipped with a gas sparger made of porous stainless steel (20mu pores). The results obtained from batch operation with total recirculation of the collapsed foam as well as from continuous operation showed that the surface excess Gamma depends on foam rate as well as bulk concentration whereas Gibbs' adsorption isotherm predicts a constant value for Gamma. It was concluded that the application of Gibbs' equation to the prediction of the surface excess accumulated at dynamic interfaces generated in the foam separation process for EHDA-Br is probably justified only under the rather stringent conditions of good drainage and perfect stability of the foam. Equations proposed to predict the performance characteristics of a continuous pool-feed foam separation column based on Gibbs' equation and an ideal foam model were also found to be valid under the same conditions. The effect on the various parameters describing the efficiency of a continuous foam separation column was studies for the following variables: feed concentration, foam column height, feed rate, column diameter. An attempt was also made to analyze the continuous foam separation process by utilizing the concept of the HTU.