Figure 2. Schematic plot of adsorption of organic compounds on multiple sites on CNT surface at various concentrations.

At relatively low C_e, as there are plenty of sorption sites, chemical molecule will prefer to sorb on those sites that have high energy. With increasing C_e, solute molecule will gradually sorb on less energetic sites and the competing ability of water molecule on sorption sites will be relatively greater, which results in increasing of a, b and v. Meanwhile, as C_e increases, the sorption sites for solute molecule continue to decrease, which might then change the sorption manner of solutes molecule, from planar (that will occupy more sorption sites per molecule) to end by end (that will take fewer sorption sites per molecule). This will lead to the increase of v and decrease of p. As C_e continues to increase, there are not enough sites for sorption and the intermolecular interactions between solute molecules may increase, then a, b, v and p would be reduced.