(179g) Extraction of Phenolic Compounds From Aqueous Solution Using a Slightly Hydrophobic Nonionic Surfactant

A simple and rapid L₃-phase extraction technique was developed to recover mixtures of phenolic compounds, including 8 priority phenolic pollutants, from aqueous solutions using nonionic surfactant Tergitol 15-S-5 at ambient temperature. The readily biodegradable Tergitol 15-S-5 surfactant is a mixture of species with secondary ethoxylated alcohols, and exhibits as a dispersion of the lamellar phase in water (L_α + W) at ambient temperature (24°C). Hence, salting-out electrolytes were in need to induce the phase separation along the boundary of L₃ + W phases at ambient temperature. Effects of different electrolytes, such as monovalent LiCl, NaCl and KCl, as well as bivalent MgCl₂ and CaCl₂, to the L₃-based extraction process were studied. The strategy to achieve a high preconcentration factor was successfully demonstrated with increasing concentration of salting-out additives and/or decreasing the surfactant concentration, which could be attributable to increase the volume of water phase. The optimum conditions for the extraction and preconcentration of these selected phenolic compounds have been established as follows, 0.2% wt of Tergitol 15-S-5 + 5.6% wt of NaCl. Moreover, the logarithms of distribution coefficients of these phenolic compounds between coexisting L₃ phase and water phase was found to be linearly proportional to the logarithms of n-octanol/water distribution coefficients of these phenolic ompounds.