This study analyzed the structural transformations and adsorption properties of Na-bentonite clay before and after chemical activation by sulfuric and hydrochloric acids. The untreated and treated samples were characterized using Xray Fluorescence, X-ray diffraction and Fourier Transform Infrared (FTIR) Spectroscopy. The adsorptive capacities of the samples were investigated by using them to adsorb organic matter from high strength phosphoric acid. The experimental data exhibited that the clay treated with sulfuric acid caused highest organic matter adsorption capacity. The kinetic models of adsorption were analyzed by the pseudo-first order, pseudo-second order, Elovich kinetic and Morris-Weber models. The results have been indicated that the pseudo-secondorder kinetic model is more appropriate than the others for natural bentonite but for chemical activated clays pseudo-first order is fitting.