Partitioning of SSOCs into Straight-Chained Surfactants

The purpose of this research was to study the effect of surfactant structure and micelle composition on the partitioning of sparingly soluble organic compounds (SSOCs) into surfactant micelles. The surfactants used in this research were sodium dodecyl sulfate (SDS), dodecyl trimethyl ammonium bromide (DDTMA), tetradecyl trimethyl ammonium bromide (TDTMA), hexadecyl trimethyl ammonium bromide (HDTMA), Mega-9 (nonanoyl-n-methyl glucamide) and polyoxyethylene ether (POE). The SSOCs used were toluene, trichloroethylene and p-xylene. SSOC partitioning into the micelles of cationic surfactants increased with increasing number of carbon atoms in the surfactant tail. However, when the amount of partitioned SSOC was normalized by the length of the straight-chain tail, there was no difference in SSOC removal between SDS, DDTMA, TDTMA, and HDTMA. Using these data and previously published data, correlations were developed between the normalized partition coefficient and hydrophobicity for both cationic and anionic straight chain surfactants. Mixed surfactant systems had lower CMCs and lower partition coefficients than did single surfactants in the 1-10 mM concentration range. The presence of a mixture of SSOCs did not affect SSOC partitioning into micelles in this study.