However, the surface area is not enough to explain all results,
since CX, that has much larger surface area than CNT (Table 1),
adsorbs less CPX (Fig. 6, top). This is most likely related with the
fact that CNT has less surface groups (Fig. 5). It was shown, for
other organic pollutants, that the presence of acidic surface groups
is detrimental to adsorption [17,22,25–27]. On the other hand,
adsorption on basic materials (or less acidic) is favoured, mainly
due to the dispersive interactions between the delocalized electrons
in the carbon basal planes and the free electrons in the CPX
molecules (namely those of the aromatic rings). CPX has many
electron-rich site groups such as carboxylic, ketone, and aromatic
groups, which might form complexes with electron-withdrawing
groups upon deprotonation.