The adsorption of Cu(II) ions from aqueous solutions by hazelnut shell activated carbon (HSAC) was studied in a batch adsorption system. Factors influencing copper adsorption such as initial copper ion concentration (25-200 mg L-1), pH (2-6), adsorbent dosage (0.5-3.0 g L-1) and temperature (293-323 K) were investigated. The adsorption process was relatively fast and equilibrium was established about 90 min. Maximum adsorption of Cu(II) ions occurred at around pH 6. A comparison of the kinetic models on the overall adsorption rate showed that the adsorption system was best described by the pseudo second-order kinetics. Desorption experiments were carried out to test the performance of the carbon and desorption efficiencies in four cycles were found to be in the range 74-79%. The adsorption equilibrium data fitted best with the Langmuir isotherm and the monolayer adsorption capacity of Cu(II) ions was determined as 58.27 mg g(-1) at 323 K. Thermodynamic parameters were calculated for the Cu(II) ion-HSAC system and the positive value of OH (18.77 kJ mol(-1)) showed that the adsorption was endothermic and physical in nature. (c) 2008 Elsevier B.V. All rights reserved.