Recovery of an anionic surfactant in the presence of benzene, toluene, and hexane by foam fractionation

The discharge of surfactants through wastewater from numerous industries is a serious concern, since they can critically impact the health of human beings as well as other living creatures. In addition, oily effluents present in the wastewater (such as benzene, toluene, and hexane) make it more harmful so that it is essential to treat it before disposing off. The present work demonstrates the removal of an anionic surfactant [i.e., sodium dodecyl sulfate (SDS)] from water by foam fractionation in the presence of these effluents. The SDS concentration was above its critical micellar concentration. A foam fraction column was used in the batch mode. SDS concentration in the samples collected from the column was measured by two-phase titration. The airflow rate was varied in the range of 0.4–1.6 dm 3 min –1 . The adsorption of the surfactant at the air–water interface was measured by the surface tension. About 72% of the SDS was recovered in the form of a semi-solid cake. Nearly 97.5% of water was recovered in this process. The removal and recovery of SDS increased with increasing airflow rate. Foam stability had a serious impact on the recovery of SDS. The oils had an antifoaming effect which reduced the foam volume. The foam stability was higher in the absence of the oils. The foam stability was analyzed by the measurement of zeta potential, and the entering, spreading, and bridging coefficients.