Cellulose, a natural polymer, was used as an adsorbent for the adsorption of Cu(II) ions from the aqueous solutions of copper sulfate pentahydrate (CuSO4 . 5H(2)O) at different temperatures and a fixed pH. The amount adsorbed increased with increasing concentration of Cu(II) ions; however, it did not differ significantly with temperature. The equilibrium times of adsorptions of Cu(II) ions at various temperatures were the same. Kinetics studies showed that the adsorption process obeyed the first-order reversible kinetic model. It was also determined that adsorption isotherms followed both Freundlich and Langmuir models. Furthermore, the thermodynamic parameters, i.e., standard free energy (DeltaG degrees), standard enthalpy (DeltaH degrees), and standard entropy (DeltaS degrees), of the adsorption process were calculated. The results obtained are discussed in detail.