The results presented in this work are related to the design of a guideline to develop specific properties at the surface of an activated carbon (AC). For this, two model aromatic compounds have been synthesized and their electrolytic behavior in aqueous solutions was studied by a potentiometric method. The textural characteristics of the activated carbon were determined by porosimetry methods. The nature of oxygen-carrying functions and the acid-base behavior of the AC surface were characterized by TPD and potentiometric titration methods, respectively. The adsorption and desorption equilibria of the aromatic compounds on activated carbon were measured in aqueous solutions, and the hysteresis between adsorption and desorption, which reveals irreversible adsorption, was discussed on the basis of the frontier orbital theory. HOMO and LUMO orbitals of the adsorbent and adsorbates were calculated, and irreversible adsorption was attributed to the small energy difference between HOMO and LUMO of the aromatic adsorbates and the adsorbent. Adsorption equilibria of K2CrO4 in aqueous solution on the AC alone and on the AC-aromatic ligand adsorbents, respectively, prove the efficient development of specific chemical functions at the carbon surface provided by the adsorbed aromatic compounds.

The adsorption of five Nalpha-substituted amino acids with a 5-nitroso-6-oxo pyrimidine as substituent on a commercial activated carbon (AC) has been studied in aqueous solution at several pH values. The adsorption processes of these organic compounds have been analyzed on the basis of the electrolytic behavior of the adsorbates. In all cases, the adsorption process is highly irreversible due to strong pi-pi interactions between the arene centers of the AC and the pyrimidine residue of the adsorbates. This interaction is consistent with XPS data and HOMO-LUMO theoretical calculations. The adsorption of these organic compounds provides a new route for the functionalization of the AC surface with carboxyl groups. In addition, the adsorption capacity of the AC/organic compound systems for Cu(II) ions in aqueous solution has been studied at different pH values. These systems show an increase of the adsorption capacity for Cu(II) compared to the AC, which is related to the AC functionalization with carboxyl groups due to the adsorbed organic compounds.

The compound N- (4-amino-1-methyl-5-nitroso-6-oxo-1,6-

The new compound N ε -(4-amino-1,6-dihydro-1-methyl-5-nitroso-6-oxopyrimidin-2-yl)-L-lysine (H 2 L) has been synthesised and its molecular structure determined by single-crystal X-ray diffraction methods. The Brönsted acid/base character of H 2 L has been determined in water in the pH range 2.5-10.0, and the nature of the observed protonation steps determined by potentiometric and spectrophotometric methods. The adsorption of H 2 L on a commercial activated carbon (AC) in aqueous solution is irreversible, mainly due to the electronic behaviour of the π system of the pyrimidine moiety. The adsorption of H 2 L on the AC provides a route to develop NH 3 + -CHR-COO --type functions on the AC surface,