In this work, the removal of cadmium ions from dilute aqueous solution by adsorption on commercial activated carbon, chitosan biosorbent and chitosan/activated carbon composite were investigated. Adsorption studies were performed in a batch system, and the effects of various experimental parameters such as solution pH, particle size and dose of adsorbent were evaluated. According to the results, the optimum operating conditions for cadmium removal by commercial activated carbon, chitosan and chitosan/activated carbon composite were pH = 6, particle size of adsorbent = 0.425 mm and adsorbent dose = 6 g/L The ANOVA tables indicate that the pH solution is the most significant removal parameter. Under these optimum operating conditions, 100% of cadmium was removed by commercial activated carbon, chitosan and chitosan/activated carbon composite after 2 h. The equilibrium adsorption data were well described by the Freundlich model for activated carbon and Langmuir model for chitosan and chitosan/activated carbon composite. The maximum adsorption capacities of activated carbon, chitosan and chitosan/activated carbon composite were 10.3 mg/g, 10 mg/g and 52.63 mg/g, respectively. It was observed that the adsorption kinetics of cadmium on these adsorbents could be well analyzed with pseudo-second-order model. (C) 2012 Elsevier B.V. All rights reserved.