Development and performance evaluation of hybrid magnetic composites as solid phase extractants for some lanthanides

Abstract

Magnetic hydroxyapatite composites (CaHAP/NF, NF/CaHAP and CaHAP–NF) and their precursors nickel ferrite (NF) and calcium hydroxyapatite (CaHAP) were successfully synthesized and characterized using different techniques. The results clarified that these materials are crystalline in nature, thermally stable up to 800 °C and possess high porous structure. The synthesized samples are superparamagnetic materials easily separated from aqueous solutions and would dissociate to some extent in strongly acidic conditions. They were successfully applied as solid phases for separation of Sm(III), Eu(III) and Tb(III) ions from aqueous solutions. The sorption process was independent of ionic strength and ion exchange was a main mechanism participating in Sm(III), Eu(III) and Tb(III) separation beside other mechanisms. A monolayer of Sm(III), Eu(III) and Tb(III) ions could be predicted to cover the surface of synthesized sorbents through a chemisorption process. Sorption of Sm, Eu(III) and Tb(III) is an endothermic process takes place spontaneously with the possibility of strong bonding between studied metal ions and sorbents surface. Desorption of Sm(III), Eu(III) and Tb(III) from loaded samples was studied using various eluents and maximum recovery was obtained using FeCl3 and EDTA solutions. More importantly, both FeCl3 and EDTA were individually applied as eluents in chromatographic separation of Eu(III) from Tb(III) in CaHAP/NF packed column and the best separation results were obtained by EDTA.