Hydrogen is a valuable source of energy. However its storage is a major concern and means has to be developed for this purpose and where processes based on the technique of adsorption can be regarded as promising ways, particularly when using natural and with no cost solid materials. The retention capabilities of this technique are shown through the present study which concerns the retention of a pharmaceutical compound, namely Diclofenac from aqueous solutions by adsorption onto activated carbon prepared from olive stones. The first stage consisted of the preparation and determination of the physical and chemical characteristics of this material such as pHpzc, porosity and specific area using known techniques of characterization. The functional groups present on the surface of this material were also determined by using Boehm method and by Fourier transform infra-red spectroscopy (FTIR). The effects of contact time, pH, initial concentration of Diclofenac and adsorbent dose were investigated experimentally. The results showed that the retention of the pollutant was rapid during the first minutes and then slowed down to reach equilibrium after 30 min. The maximum adsorption was reached at pH = 2. Diclofenac adsorption kinetic was of the pseudo-second order controlled by the intra-particular diffusion phenomenon but is not the limiting step. Basing on the obtained experimental data, the adsorption isotherm on the preset concentration range was well represented by the BET model. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.