INTERACTION BETWEEN ORGANIC AND INORGANIC POLLUTANTS IN THE CLAY INTERLAYER

A synergistic mechanism for the retention of organic and inorganic pol lutants in clays is discussed in this paper. The mechanism of adsorpti on of cis- or trans- 1, 2-dichloroethylene vapor (CDE or TDE, respecti vely) by hydrated smectite clay (hectorite) exchanged with Pb2+, Hg2+, Cd2+, Ca2+. Ag-, or Na+ has been investigated by simultaneously measu ring chlorohydrocarbon uptake and water desorption isotherm and by rec ording the infrared (IR) spectrum of the adsorbed phase. Hydrated hect orite saturated with divalent cations adsorbs about 55% more CDE or 35 % more TDE than those saturated with monovalent cations. The quantity of chlorohydrocarbon adsorbed is also a function of the hydration of t he clay interlayer space. When dehydrated, hectorite does not adsorb C DE or TDE. Upon long outgassing at room temperature or even at 100-deg rees-C, the characteristic IR bands of clays with adsorbed chlorohydro carbon, although much weakened, are still observable. The ratio of the amount of water desorbed to the amount of chlorohydrocarbon adsorbed varied from about 0.22 to 0.34. A shift of the center of gravity of th e hydration water OH stretching frequency towards a higher wavenumber and of the asymmetric CC 1 stretching vibration toward a lower frequen cy suggest that the formation of hydrogen bonds between CDE or TDE and water is the driving force for adsorption and that the cation-dipole interaction does not play a major role.