SORPTION OF PHENANTHRONE FROM WATER ONTO ALUMINA-COATED WITH DIANIONIC SURFACTANTS

An aluminum oxide (alumina) coated with three dianionic surfactants (c ommercial DOWFAX) was examined for its effectiveness to sorb phenanthr ene from water, as a function of the surfactant loading rate and the s urfactant alkyl chain length. The results showed that the dianionic su rfactants adsorbed on alumina are effective phases for the sorption of nonionic organic compounds (NOCs) such as phenanthrene, increasing th e apparent distribution coefficient (K) of phenanthrene onto the soli d phase by up to 3 orders of magnitude. The effectiveness of the surfa ctants as sorptive phases was shown to increase with their carbon cont ent(i.e., the alkyl chain length). To distinguish between the contribu tions to the sorption of phenanthrene by surfactant monolayers and bil ayers, the partitioning of phenanthrene onto the surfactant coated alu mina was quantified over a large range of surfactant loading. Compared on a unit surfactant mass basis, the bilayers of the dianionic surfac tants are approximately 3-6 times as effective in terms of sorbing phe nanthrene from water than the corresponding monolayers, showing that t he organic carbon-normalized partition coefficient for these two sorbe d surfactant phases differs. It was also shown that, on a per unit sur factant mass basis, the partitioning of phenanthrene between the adsor bed dianionic surfactant phases (monolayers and bilayers) and water is 5-7 (15 in one case) times more effective than that between the corre sponding surfactants phases (monomers and micelles) in the aqueous pha se and water.