Adsorption of a designed l-glutamic acid-pyrimidine derivative ligand on an activated carbon for the removal of Cu(II) from aqueous solution

The influence of pH on the adsorption of the N-(4-amino-1,6-dihydro-1-methyl-5-nitroso-6-oxopyrimidin-2-yl)-l-glutamic acid ligand from aqueous solution was studied using a commercial granulated activated carbon. At pH values in the range 2.5–6.5, the uptake of the adsorbate is largely reduced as the pH value increases, which is related to the ligand deprotonation. It is proposed that the ligand uptake takes place via π–π interactions between the planar pyrimidine moiety of the ligand and the arene centres of the carbon surface which explains the irreversible character of these adsorption processes. Ligand adsorption develops carboxyl functionalities at the carbon surface, thus providing a carbon material with enhanced adsorption capacity to Cu2+ ion compared to the unfunctionalized activated carbon, in the 2.5–6.0 pH range. The enhancement of the adsorption capacity is related to the reactivity of the ligand carboxylate groups although the Cu2+ adsorption seems to be constrained to the external surface area of the activated carbon.