Flocculation of anionic surfactant micelles in the presence of hydrocarbons

Abstract

Adsorptive micellar flocculation (AMF) is a surfactant-based separation process based on the flocculation of micelles of suitable anionic surfactants by Al3+. The micelles form large amorphous flocs which can be removed by filtration, which is attractive because soluble pollutants are captured by the floc, thus providing a simple separation method. As the primary aim of AMF is the removal of anionic pollutants from aqueous streams, it is important to investigate the influence of the various substances which may affect it. This article discusses the influence of the presence of insoluble hydrocarbons on the flocculation of micelles of the anionic surfactant dodecyl sulfate by Al3+. The ratio between surfactant remaining in solution and total surfactant and the ratio between Al3+ and surfactant in the flocculate are determined in systems composed of an aqueous solution containing a constant dodecyl sulfate concentration of 0.05 M and a variable Al3+ concentration and an organic phase (decane) with phase volume ratios of decane/water ranging from 0 (no decane) to 0.15. The flocculation is only slightly affected by the presence of decane for decane/solution ratios below 0.05, while the effect (lower flocculated fraction) is more marked above this ratio.