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Abstract-An activated carbon obtained from olive stones and with very low ash content (0.10%) was treated with either HCI, HF or HNO,. The changes in surface area and porosity resulting from the acid treatments were studied by N, and CO, adsorption at 77 and 273 K, respectively and by mercury porosimetry. The changes in surface chemistry were studied by temperature-programmed desorption and Fourier transformed infrared spectroscopy. The treatments with HCl yielded activated carbons on which some chlorine remained chemisorbed, whereas the HF treatment did not fix any fluorine. Due to this, the HCI treatment had a slight effect on the microporosity of the samples. Moreover, the HF treatment increased the amount of CO-evolving surface groups. The treatment with HNO, destroyed the pore walls to a large extent, fixing a large amount of oxygen surface groups. The nature and structure of the CO-and CO,-evolving groups will be discussed in detail. 0 1997 Elsevier Science Ltd All rights reserved

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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.