Surfactant-based separation technique for the removal of dissolved organics from water
Advancing the chemical engineering fundamentals
Interfacial & Colloidal Phenomena - III (T2-6c)
Keywords: nonionic surfactant,cloud point,phase separation,salting-out electrolyte,distribution coefficient
I.V.Rao* and P.Venkat Reddy**
University College of Technology
Osmania University, Hyderabad – 500 007. (India)
Separation techniques based on the use of surfactants have several important advantages over traditional separation methods. Aqueous solutions of certain surfactant micelles exhibit phase separation behaviour upon temperature alteration. This phenomenon can be exploited in separation science for the development of extraction, purification and pre-concentration schemes for different solutes. Since the addition of just a small amount of an appropriate nonionic surfactant to the aqueous sample solution is required, this approach is convenient and fairly benign, eliminating the need for the use of organic solvents as in conventional liquid-liquid or solid-liquid extraction.
The technique of extracting dissolved species from water via nonionic surfactant micelle-mediated phase separation was studied. The effect on extraction efficiency, solute distribution coefficient and phase volume ratio of pertinent experimental parameters such as surfactant hydrophilicity, temperature and additives was systematically evaluated. Surfactant hydrophilicity was examined by monitoring the extraction parameters for two members of the homologous series of octylphenoxypolyethoxyethanols with varying ethylene oxide units.
The cloud point technique was used to recover phenol, o-chlorophenol and
o-nitrophenol from aqueous solutions using octylphenoxypolyethoxyethanol as the nonionic surfactant. The experiments indicate that increase in temperature resulted in increased recovery of the solutes. Recovery of phenols decreases from o-nitrophenol to o-chlorophenol followed by phenol and is increased in the presence of sodium chloride ; a salting-out electrolyte. The presence of salting-out electrolytes is preferred both to decrease the cloud point and to increase the efficiency of extraction. It was also observed that as the surfactant hydrophilicity increases, the solute distribution coefficient decreased for all the solutes studied.
*author for correspondence
**presently with the Department of Chemical Engg., IIT Bombay, Mumbai-400076.
Presented Thursday 20, 12:00 to 12:20, in session Interfacial & Colloidal Phenomena - III (T2-6c).
