Temperature effects on iodine adsorption on organo-clay minerals

The sorptive capability of clay minerals for anionic radionuclides can be improved substantially by exchanging the natural inorganic interlayer cations with certain organic cations. After screening a variety of possible candidates, four organic cations were selected and combined with three clay minerals, providing 12 organo-cation/clay mineral combinations. The samples were tested for anion adsorption in batch experiments with radioiodide in a concentration range of 10 ⁻² to 10 ⁻⁹ mol l ⁻¹ and exhibited high adsorption in bidistilled water as well as in synthetic groundwater. Results for two clay minerals—a smectite and a vermiculite—and four organic cations are given in this paper. Tests were also performed with temperature pretreated material. An increase of the pretreatment temperature from 20 to 40, 60, 80 and 100 °C did not result in a remarkable effect on iodide adsorption, except for the 1,12-dipyridiniododecan/vermiculite combination. In batch experiments with equilibrium temperatures of 20–60 °C, iodide adsorption decreased slightly with increasing temperature. Only 1,12-dipyridiniododecan in combination with smectite and vermiculite showed a somewhat lower iodide adsorption at higher temperatures.