Foam Separation of Anions: Stoichiometry

Publisher Website
Google Scholar
Abstract
Experimental studies have been carried out on the foam separation of I−, HCrO4 −, S2O3 2−, and Ag(S2O3)2 3− using a cationic surfactant as the collector-frother. The object of the work is the establishment of the Stoichiometry of the foam-separated surfactant cation-anion product to gain some insight into the mode of interaction between the surfactant and the anion. The Stoichiometry, S, defined as the ratio of the rate of surfactant removal to the rate of anion (colligend) removal at the gas bubble interfaces, ranges from 2.2–2.8 mole/mole (average values) for S2O3 2−, being a function of foaming time for the only system which does not involve the formation of particulates between the surfactant and the colligend. For HCrO4 −, I−, and Ag(S2O3)2 3−, S is constant with foaming time and a participate product is formed in the bulk solution and/or the froth. For HCrO4-, S is close to unity and is almost independent of the feed surfactant/colligend ratio, indicating minimum free surfactant. For I-, S averages 1.3 and is a weak function of the feed ratio, indicating that free surfactant is significant. Steric effects or secondary adsorption or exchange of Ag(S2O3)2 3− the particulates makes S a linear function of the feed ratio.