Recovery of Surfactant from an Aqueous Solution Using Continuous Multistage Foam Fractionation: Mixed Surfactant System

Abstract

A continuous multistage foam fractionation column with bubble caps was used for surfactant recovery from mixed surfactant solutions containing polyethylene glycol tert-octylphenyl (OPEO₁₀) and cetylpyridinium chloride (CPC) and the effects of air flow rate, foam height, and feed flow rate were investigated under a steady state of conditions. For the mixed surfactant system, the effect of synergism in the surfactant adsorption density was found. For separation efficiency, the total residual factor remained unchanged with an increasing feed molar fraction of OPEO₁₀ (α), suggesting that the addition of OPEO₁₀ does not increase the total separation efficiency. The residual factor of CPC increased with an increasing molar fraction of OPEO₁₀ (α), while the residual factor of OPEO₁₀ was lower for the mixed surfactant systems. A competitive removal was found in that the OPEO₁₀ can compete with CPC for the bubble surface. The total separation factors and enrichment ratio of mixed surfactant systems were in-between the two single surfactant systems at a long foam residence time and, in contrast, showed antagonism at short foam residence. This is due to the difference in liquid entrainment in foam at long and short foam residence times.

Keywords:

• cetylpyridinium chloride
• foam fractionation
• mixed surfactant system
• polyethylene glycol tert-octylphenyl
• recovery of surfactant

ACKNOWLEDGEMENTS

The Thailand Research Fund is acknowledged for providing a Royal Golden Jubilee Ph.D. scholarship (Grant No. PHD/0059/2550) to the first author. The Research Unit of Applied Surfactants for Separation and Pollution Control under Ratchadapisak Sompoch Fund, Chulalongkorn University and Center of Excellence on Petrochemical and Materials Technology, Ministry of Education are also acknowledged.

Notes

*The values calculated from Eqs. (7) and (8).