Surfactant recovery from water using foam fractionation: Effect of temperature and added salt

The purpose of this study was to investigate the use of foam fractionation to recover surfactant present at low concentrations in aqueous streams. A s imple continuous mode foam fractionation was used, and three surfactants we re chosen for this study: sodium dodecyl sulfate, cetylpyridinium chloride, and sodium n-hexadecyl diphenyloxide disulfonate. In a previous study the effects of surfactant concentration, air flow rate, liquid- and vapor-phase heights, and sparger type were investigated for these surfactants. Here, t he effects of temperature and added salt are studied. It is found that the foam flow rate and enrichment ratio increase whereas the foam wetness and t he rate of surfactant recovery decrease with increasing temperature. Increa sing the concentration of added salt decreases the CMC of the surfactants. The foam flow rate, foam wetness, and the rate of surfactant recovery incre ase, while the enrichment ratio decreases with increasing concentration of salt.