The presence of pharmaceutic compounds has been widely detected in water and wastewater due to the increase in their production and consumption. Since conventional treatments are not able to totally remove these microcontaminants, more efficient technologies, such as adsorption, must be investigated. This study aimed to evaluate the adsorption of diclofenac sodium (DS) onto commercial organoclay (Spectrogel (R) Type C) in static system. Process optimization was performed through Central Composite Design (CCD) and the adsorbent mass of 0.5 g and agitation speed of 200 rpm were selected as the optimum conditions. The variable initial concentration of DS was not statistically significant. Pseudo-first order model showed the best correlation to kinetic experimental data and the investigation of adsorption mechanism revealed that external mass transference was the main rate-controlling step. Equilibrium data obtained at 15 degrees C and at 30 degrees C were best described by Freundlich isotherm model and at 50 degrees C by Temkin isotherm model. The maximum adsorption capacity from Langmuir was of 0.133 mmol/L at 50 degrees C. Thermodynamically, the process is spontaneous and endothermic. Characterization analysis depicted that DS adsorption takes place on the surface of Spectrogel, which is not significantly modified by the process. (C) 2019 Elsevier B.V. All rights reserved.