Hydroxyapatite-gelatin nanocomposite as a novel adsorbent for nitrobenzene removal from aqueous solution

A novel adsorbent of hydroxyapatite–gelatin (HAP–GEL) nanocomposite was developed for nitrobenzeneremoval from aqueous solution. The adsorbent was characterized and its performance in nitrobenzeneremoval was evaluated. The effects of contact time, adsorbent dosage, temperature, pH, ionic strength,humic acid, and the presence of solvent on nitrobenzene adsorption, as well as the thermodynamicparameters for adsorption equilibrium were also investigated. Results showed that HAP–GEL nanocom-posite possessed good adsorption ability to nitrobenzene. The adsorption process was fast, and it reacheda steady state after only 1 min. Nitrobenzene removal was increased with an increasing amount of adsor-bent dosage but decreased as the temperature and pH increased. Meanwhile the amount of nitrobenzeneadsorbed decreased with an increase of ionic strength from 0.01 to 1.0 mol/L and humic acid from 10to 50 mg/L. The adsorption isotherm studies showed that both Langmuir and Freundlich models couldfit the experimental data well, and the maximum adsorption capacity was estimated to be 42.373 mg/g.The thermodynamic parameters suggested that the adsorption of nitrobenzene on HAP–GEL nanocom-posite was physisorption, spontaneous and exothermic in nature. Findings of this study demonstratedthe potential utility of the HAP–GEL nanocomposite as an effective adsorbent for nitrobenzene removalfrom aqueous solution.