When the basic functional groups are fully deprotonated (i.e., pH N
pKabasic groups N PZC), the electrostatic repulsion of the negatively charged
species is intensified, as schematically represented by Eq. (13). The low
adsorption density of copper cyanocomplexes under such conditions, as
observed experimentally, supports this role of the basic groups available
on the carbon surface in the adsorption process.