ADSORPTIVE SELECTIVITY OF ORGANIC-CATION-MODIFIED BENTONITE FOR NONIONIC ORGANIC CONTAMINANTS

The mineral surface of Wyoming bentonite was modified by replacing ino rganic ions with four quaternary ammonium cations in an amount equal t o 40 percent of the cation-exchange capacity of the bentonite. The fou r quaternary ammonium cations used were tetramethylammonium (TMA), tet raethylammonium (TEA), benzyltrimethylammonium (BTMA), and benzyltriet hylammonium (BTEA). Sorption of benzene, tetrachloromethane, trichloro ethene, 1, 2-dichlorobenzene, and naphthalene to the modified sorbents from water at 20 degrees C was investigated. All five solutes were so rbed strongly by TEA-, BTMA-, and BTEA-bentonite, but only benzene and tetrachloromethane were strongly sorbed by TMA-bentonite. The sorptio n isotherms are distinctly nonlinear and the magnitude of sorption is not correlated with the solute's aqueous solubility. In contrast, sorp tion of trichloroethene, 1, 2-dichlorobenzene, and naphthalene to TMA- bentonite was negligible relative to benzene and tetrachloromethane so rption. The apparent absence of solute selectivity by TEA-, BTMA-, and BTEA-bentonite, along with their large sorption capacities, indicates that these sorbents can potentially be useful as components of landfi ll liners or slurry walls to decrease the mobility of a variety of non ionic organic contaminants.