Selectivity Coefficients for Divalent Oxyanions from the Continuous Foam Fractionation of a Quaternary Ammonium Surfactant

An experimental investigation is presented of the continuous, single equilibrium stage foam fractionation of chromate (CrO42-) and of thiosulfate (S2O32-) from 0.4 to 3.0 × 10-4 M aqueous solutions. the cationic surfactant, ethyl-hexadecyldimethylammonium bromide (EHDA-Br), is modeled as a soluble ion exchanger, considering the exchange of CrO42- and S2O32- or EHDA-CrO4-and EHDA-S2O3- for Br-. the data indicate that EHDA-CrO4- or EHDA-S2O3- is exchanged with Br-. the selectivity coefficient for chromate is 3.90 and that for thiosulfate is 16.8.