| Abstract
| - To characterize the linear adsorption phenomena inaqueous nonionic organic solute−mineral systems, theadsorption isotherms of some low-molecular-weight nonpolarnonionic solutes (1,2,3-trichlorobenzene, lindane, phenanthrene, and pyrene) and polar nonionic solutes (1,3-dinitrobenzene and 2,4-dinitrotoluene) from single- and binary-solute solutions on hydrophilic silica and alumina wereestablished. Toward this objective, the influences oftemperature, ionic strength, and pH on adsorption werealso determined. It is found that linear adsorption exhibitslow exothermic heats and practically no adsorptivecompetition. The solute−solid configuration and theadsorptive force consistent with these effects werehypothesized. For nonpolar solutes, the adsorption occurspresumably by London (dispersion) forces onto a waterfilm above the mineral surface. For polar solutes, theadsorption is also assisted by polar-group interactions.The reduced adsorptive forces of solutes with hydrophilicminerals due to physical separation by the water filmand the low fractions of the water-film surface coveredby solutes offer a theoretical basis for linear solute adsorption,low exothermic heats, and no adsorptive competition.The postulated adsorptive forces are supported byobservations that ionic strength or pH poses no effect onthe adsorption of nonpolar solutes while it exhibits asignificant effect on the uptake of polar solutes.
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