Regarding the
electronegativity, there is the following selectivity order: Pb
> Cr > Cd, since the higher the electronegativity, the greater
the affinity for sorption (Sag et al., 2002). Regarding the ionic
radius, Pb would be the most adsorbed, followed by Cd and Cr.
Pb ions have the smallest radius compared to the other metals
studied, thus, it has greater accessibility to the surface and
pores of the adsorbent, resulting in higher adsorption capacity
(Srivastava et al., 2008).