The Role of Iron Incorporation in a Novel Apatite Structure: A Comparative Study on Strontium Separation

In this paper, a novel magnetic apatite composite derived from Fe3O4 and hydroxyapatite (HAP) was synthesized, characterized and applied for removal of Sr2+ ions from aqueous solution. Batch experiments were conducted to comparatively investigate the separation behavior of Sr(II) as a function of contact time, sample mass, initial ph value and temperature. The BET data illustrated that the surface area and pore volume highly increased after iron incorporation in HAP structure during the synthesis of the magnetic apatite beads. The saturation magnetization (Ms) indicated that the prepared composite was a ferromagnetic material. The results also clarified that Sr(II) uptake occurred rapidly in the first 60 min and was dependent on solution ph value. Strontium ions exhibited a higher affinity to the magnetic composite than to the other comparative sorbents. The separation of Sr(II) from aqueous solution was attained mainly through ion exchange mechanism. The maximum sorption capacity (Q) was found to be 1.12, 15.38 and 27.48 mg g-1 for Sr(II) sorption onto Fe3O4, HAP and HAP-Fe3O4 at 294 degree K. The values of thermodynamic parameters (ΔG◦, ΔH◦, and ΔS◦) were determined at different temperatures and the data showed that Sr(II) separation was a feasible and endothermic process. The prepared magnetic composite could be considered as an effective and prospective sorbents to separate 90Sr in nuclear waste and industry wastewater.