AbstractIn the present study, jatropha oil cake (JOC), a waste produced from processing jatropha seeds for biodiesel production, has been investigated for the removal of nickel (II) from aqueous solutions. Jatropha oil cake contains different functional groups that can participate in the metal ion complexation. Jatropha oil cake is used in its natural form (JOCN) as well as in its immobilized form (JOCB). Batch experiments were performed for adsorption of Ni (II) by JOCN and JOCB. Parameters affecting the adsorption, such as the effect of adsorbent dose, pH, the initial concentration of metal ion, agitation speed, and contact time, were studied for the maximum removal efficiency. Removal efficiency was found to be 62% and 63% for Ni (II) at pH 6.2 in its natural and immobilized forms, respectively. Maximum adsorption occurred within an hour for Ni (II) with JOCN and 90 min for JOCB. The equilibrium data was analyzed using Langmuir and Freundlich isotherms.