Contents lists available at ScienceDirect Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso Hydroxyapatite/NiFe 2 O 4 superparamagnetic composite: Facile synthesis and adsorption of rare elements Mohamed A. Attia a , Saber I. Moussa a, ⁎ , Reda R. Sheha a , Hanan H. Someda a , Ebtsam A. Saad b a Nuclear Chemistry Dept., Hot Lab Center, Atomic Energy Authority, P.O. 13759, Cairo, Egypt b Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt HIGHLIGHTS • A superparamagnetic hydroxyapatite composite (CaHAP/NF) was successfully synthesized. • The composite is a crystalline in nature, possesses a high porous structure and chemically stable at pH > 3.5. • 152+154 Eu and 160 Tb radionuclides were efectively removed using the synthesized magnetic composite. • REEs were sufciently recovered using FeCl 3 and EDTA as eluents. • The chromatographic separation of Eu(III) from Tb(III) was signifcantly attained using EDTA. ARTICLE INFO Keywords: Hydroxyapatite Ferrite Superparamagnetic Eu(III) Tb(III) ABSTRACT A magnetic hydroxyapatite composite (CaHAP/NF) derived from calcium hydroxyapatite [Ca 10 (PO 4 ) 6 (OH) 2 ] and nickel ferrite [NiFe 2 O 4 ] was successfully synthesized by a coprecipitation method. The synthesized com- posite was characterized using Fourier transform infrared spectroscopy (FT–IR), X-Ray difractometer (XRD), thermogravimetric diferential thermal analysis (TG-DTA), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). Results clarify that the composite is a crystalline in nature, thermally stable up to 800 °C and possesses a high porous structure. The synthesized CaHAP/NF composite is a superparamagnetic material easily separated from aqueous solutions and would dissociate to some extent in strongly acidic con- ditions. The synthesized material was successfully applied as a solid phase for separation of Eu(III) and Tb(III) ions from aqueous solutions. The efect of various parameters (e.g. solution pH, equilibrium time and ionic strength) on sorption process was studied in static conditions. The synthesized sorbent could be considered as an efcient candidate for separation and recovery of Eu(III) and Tb(III). The sorption process was very fast initially, reached equilibrium within 6 h of contact and independent of ionic strength. The maximum sorption capacity values were 137.35 and 130.43 mg g –1 for Eu(III) and Tb(III), respectively. Desorption of Eu(III) and Tb(III) from loaded sample was studied using various eluents and maximum recovery was obtained using FeCl 3 and EDTA solutions. More importantly, both FeCl 3 and EDTA were individually applied as eluents in chromatographic separation of Eu(III) and Tb(III) in CaHAP/NF packed column and the best separation results were obtained by EDTA. 1. Introduction Rare earth elements (REEs) consist of 17 elements of the periodic table including 15 lanthanides along with yttrium and scandium (Liatsou et al., 2015; Anastopoulos et al., 2016; Jacinto et al., 2018). They are further subdivided into light and heavy rare earth elements on the basis of their atomic number. REEs have unique properties and often termed as "seeds of technology" (Ponou et al., 2014). They are widely used in diferent applications such as metallurgy, electronics, alloys, fertilizers, lasers, magnets, superconductors, catalysis, chemical reagents and nuclear energy (Smith et al., 2016; Rychkov et al., 2018). The total demand for REEs was increased from 128,000 t in 2011 to 170,000 t in 2015, while it is expected to rise to 255,000 t in 2020 with a growth rate about 6–10%/year (Fernandez, 2017). Such expected great demand for rare earth elements is resulted mainly from their widespread applications in many felds of human life. With ever- https://doi.org/10.1016/j.apradiso.2018.12.003 ⁎ Corresponding author. E-mail addresses: mohamed.attia@eaea.org.eg (M.A. Attia), saber.moussa@eaea.org.eg (S.I. Moussa), reda.sheha@eaea.org.eg (R.R. Sheha). Applied Radiation and Isotopes 145 (2019) 85–94 Available online 05 December 2018 0969-8043/ © 2018 Published by Elsevier Ltd. T