Separation of SDS from its determined lowest concentration by a two-stage foam separation

• 50 mg/L was determined as the lowest concentration of SDS in foam separation.
• In the one-stage foam column, E was improved but R decreased significantly.
• Surface excess was measured under continuous operation at low concentrations.
• A two-stage foam separation technology using only one column was developed.
• Using this technology, E and R increased to 28.0 and 94.2%, respectively.

ObjectiveThe lowest concentration of sodium dodecyl sulfate (SDS) separated capably from its feed solution using a one-stage foam separation was determined. Both enrichment ratio and recovery percentage of SDS were increased and SDS concentration of the residual solution was decreased at its lowest concentration.Materials methodThe effects of SDS concentration and superficial gas velocity on foaming height and enrichment ratio of SDS were studied in order to determine the lowest SDS concentration in foam separation. A two-stage foam separation technology using only one column was developed to improve the performances at the lowest SDS concentration.ResultsThe results showed that the lowest SDS concentration in foam separation was 50 mg/L. In the one-stage foam separation, SDS surface excess increased with increasing the height of the liquid phase and the pore diameter of gas distributor, thus enrichment ratio increased from 1.9 to 7.2 and however, recovery percentage decreased and SDS concentration of the residual solution significantly increased. In the developed two-stage foam separation, enrichment ratio and recovery percentage increased to 28.0 and 94.2%, respectively and at the same time, SDS concentration of the residual solution decreased to 6.0 mg/L under the operating conditions of SDS concentration of the feed solution of 50.0 mg/L, loading volume of 0.630 L and superficial gas velocity of 1.33 mm/s.