Pharmaceutical products (PPs) are non-biodegraded substances which are more and more commonly found in sewage and surface water (Thiebault at al., 2015). Although being present at low concentration, these substances have been recognized to drive to toxic effects on several ecosystems. Among PPs recalcitrant to water treatments, diclofenac, a nonsteroidal anti-inflammatory substance, shows a high toxicity (Ferrari et al., 2003) and remains at high concentration in the environment (Miege et al., 2009) due to its particular resistance to the current treatment (Verlicchi et al., 2014). For this purpose, new techniques including adsorbents have to be developed for the adsorption of PPs (Guégan et al., 2015). In the present contribution, the adsorption of diclofenac onto a clay mineral and its organoclay derivatives has been studied with a particular understanding of the interactional mechanisms of this PP with the prepared adsorbents. The experimental data obtained by a set of complementary techniques (X-ray diffraction, infrared spectroscopy, gas chromatography coupled with mass spectroscopy) reveal that organoclays prepared with the use of a cationic long-alky chains surfactant (BDTA) show a particular affinity to diclofenac which is enhanced as the density of surfactant is increased.