Adsorption and desorption of m-xylene vapor on organically modified montmorillonite

m-Xylene vapor was adsorbed to organically modified montmorillonite (organoclay). Hexadecyltrimethylammonium (HDTMA) was used to modify the surface of the clay. In adsorption experiments, the organoclay, along with the non-modified (washed) clay, was used. m-Xylene was adsorbed from a gaseous phase by using a fixed adsorption bed. The adsorption break-through curves and the adsorption isotherms were determined at three different temperatures (24, 34, and 44 degrees C). The adsorption data were modeled with the BET isotherm equation. It was found that the adsorption isotherms of washed clay exhibited a favorable Type I behavior, which implies that the adsorption capacity is strongly dependent on vapor concentration at low concentration ranges. In regards to the organoclay, isotherms showed a marginally favorable Type II behavior with a reduced adsorption capacity at low concentrations, and exhibited a linear increase at elevated vapor concentrations. The adsorption capacity of both washed clay and organoclay obviously decreased with the temperature. The desorption of m-xylene from the clays was also performed by using pure nitrogen, and the desorption rate constant k was on the order of 10(-5) min(-1) for all types of clay.