Recovery of surfactants from water using multi-stage foam fractionation : effects of lail length, head group and salinity

Abstract

Surfactants are widely used in many industries such as healthcare, food processing, as well as several surfactant-based separation processes, and the effluent streams of these processes usually contain surfactants that need to be removed and recovered for both environmental and economic reasons. In this study, a multi-stage foam fractionation column with bubble-cap trays was used to recover surfactants and the effect of tail length and the head group of the surfactants hexadecyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB), dodecyltrimethylammonium bromide (DTAB) and hexadecylpyridinium bromide (CPB) and the effect of salinity were studied. The foam fractionation system was studied under steady state conditions and at a constant concentration of 0.5 times CMC of each surfactant at room temperature. Both surfactant recovery and enrichment ratio were strongly affected by the tail length of the surfactant and the salinity. The recovery and the enrichment ratio of the surfactant increased with increasing tail length of the surfactant. The surfactant recovery decreased in the presence of a pyridine group at the head group of the surfactant in contrast to the effect on the enrichment ratio. The surfactant recovery increased with increasing salt concentration. Beyond the optimum salinity, the surfactant recovery decreased with increasing NaCl concentration.