In this study, the nanocrystalline hydroxyapatite (HAP) prepared by thermal decomposition of precursors was used as the adsorbent, and the potential of nanocrystalline HAP for nitrobenzene removal from aqueous solution was evaluated. Results indicated that nitrobenzene adsorption was initially rapid and the adsorption process reached a steady state after 1 min. The adsorption isotherms were well described by the Langmuir and the Freundlich models, the latter being found to provide the better fit with the experimental data. The nitrobenzene adsorption capability of the nanocrystalline HAP was investigated as a function of temperature, pH, ionic strength, fulvic acid, and the presence of solvent. According to the experimental results, decrease in pH and temperature resulted in increase in nitrobenzene adsorption capacity; Increasing ionic strength and the presence of fulvic acid decreased the adsorption of nitrobenzene by nanocrystalline HAP; Acetone appeared to inhibit nitrobenzene adsorption to an extent greater than the presence of methanol. Thermodynamics studied revealed that the adsorption of nitrobenzene by nanocrystalline HAP was physisorption, spontaneous and endothermic in nature. This study showed that nanocrystalline HAP could be used as an efficient adsorbent material for the removal of nitrobenzene from aqueous solution. (C) 2010 Elsevier B.V. All rights reserved.