In recent years, the use of new technologies based on non-conventional energies such as ultrasound gains increasing importance. Ultrasound exhibits several beneficial mechanical effects in solid-liquid systems by means of the cavitations phenomenon. In this study, activated carbon adsorbent for removing heavy metals cations such as Cu2+ from aqueous solutions has been prepared. For this purpose, hazelnut shells were impregnated with KOH solution under ultrasound irradiation. After filtration, hazelnut shells have been carbonized under inert N-2 atmosphere. The experiments were planned by fractional factorial design and central composite design. Activated carbons were characterized by their copper adsorption capacity. Optimum process conditions were obtained by using a constrained optimization program as follows: particle size 0.83 mm, ultrasound power/volume 19 W/L, impregnation ratio 0.06 g/mL, impregnation time 143 min, activation temperature 838 degrees C and activation time 19 min, following with maximum adsorption capacity was found as 40 mg Cu2+/g Ac. Activated carbon with the maximum adsorption capacity was further characterized by using scanning electron microscopy and its open pore structure was observed. (c) 2005 Elsevier B.V. All rights reserved.