In this study, I found that oyster shell powder (OSP) can effectively adsorb Cu2+ and Ni2+ from wastewater, with the adsorption capacity being higher for the former ion. The isotherms for the adsorption of Cu2+ and Ni2+ on the OSP fitted the Langmuir, Freundlich, and Dubinin-Kaganer-Radushkevich isotherms quite well (R-2 = 0.949-0.984, 0.912-0.988 and 0.900-0.990, respectively). Positive values of Delta H degrees, and Delta S degrees, indicated that these adsorptions were endothermic in nature; the values of E (between 1.722 and 3.553 kJ mol(-1)) were consistent with a physical adsorption mechanism. Moreover, the adsorptions of Cu2+ and Ni2+ on the OSP followed pseudo-second-order kinetics. The adsorption capacities of the OSP toward Cu2+ and Ni2+ were 49.26-103.1 and 48.75-94.3 mg g(-1), respectively. (C) 2009 Elsevier B.V. All rights reserved.