Nano-rod hydroxyapatite for the uptake of nickel ions: Effect of sintering behaviour on adsorption parameters

Sorption studies in batch approach were carried out to investigate the elimination of Ni(II) ions from aqueous solution by fish scale derived nano-rod hydroxyapatite (FSDNHA) obtained via thermal decomposition at 800 and 900 degrees C respectively. The effects of Ni2+ concentration, contact time, pH, FSDNHA dose and temperature on elimination process were examined. Adsorption studies showed that maximum uptake amount of Ni2+ was attained at initial Ni2+ concentration of 240 mg L-1, sorption time of 120 min, FSDNHA dose of 40 mg and solution pH of 6.0. The highest value of R-2 obtained for Langmuir, Temkin, and Freundlich isotherms models are (0.996, 0.994, and 0.990) for FSDNHA-800 and (0.998, 0.986, and 0.992) for FSDNHA-900 respectively. The values of the maximum monolayer adsorption capacities obtained from Langmuir isotherm for FSDNHA-800 and FSDNHA-900 are 114.151 and 183.321 mg g(-1)- respectively. Kinetic modeling of the adsorption data clearly revealed that the sorption of Ni2+ onto the active sites of the FSDNHA surface was governed by Pseudo-first-order kinetic model. Thermodynamics parameters of Gibbs free energy (Delta G degrees), enthalpy (Delta H degrees) and entropy change (Delta S degrees) revealed that the sorption of Ni2+ on FSDNHA was spontaneous, feasible and exothermic in nature. Well resolved peaks of a characteristic pure hydroxyapatite (HA) containing hydroxyl, phosphate and carbonate groups were obtained as the major functional groups responsible for the uptake of Ni2+, while the morphological analysis by FE-SEM and TEM revealed a nano-rod shape. This current study showed that Ni2+ removal by FSDNHA compared favorable with other adsorbents and is feasible.

Automated summary

Sorption studies using batch approach showed efficient elimination of Ni(II) ions from aqueous solution by fish scale derived nano-rod hydroxyapatite (FSDNHA), indicating its favorable adsorption performance and feasibility compared to other adsorbents.