In this study, systematic adsorption tests were carried out using Co/gama-Al2O3 adsorbents of different compositions for removal of Reactive Blue 19 dye from aqueous solutions. The adsorbent was characterized by scanning electron microscopy, X-Ray powder diffraction, diffuse reflectance UV-visible spectroscopy and EDX analysis. The influences of several parameters such as pH, adsorbent concentration, adsorption time and dye concentration on the adsorption capacity of g-Al2O3 and Co/g-Al2O3 were investigated. The obtained results indicate that the adsorption is strongly dependent on the solution pH. The maximum adsorption capacity of the Reactive blue 19 dye onto Co/gama-Al2O3 takes place at around pH 2. The adsorption process is fast in the first minutes (95% from the amount of dye being removed after 6 minutes).