Efficient lanthanides adsorption using magnetic hydroxyapatite incorporated cobalt

ABSTRACT

Magnetic hydroxyapatite incorporated cobalt (Co/HAp@Fe₃O₄) was fabricated by introducing both Co²⁺ and Fe₃O₄ into the hydroxyapatite (HAp) matrix. HAp@Fe₃O₄ and Co/HAp@Fe₃O₄ were characterised by IR, XRD, EDX, SEM and TG/DTA. The adsorption efficiency of La(III) and Sm(III) was compared on both HAp@Fe₃O₄ and Co/HAp@Fe₃O₄ using several factors, such as solution pH, contact time, initial metal concentrations and reaction temperature. It was found that the appropriate factors for the highest adsorption were at pH 5 and the equilibrium time was 60 min. The Co/HAp@Fe₃O₄ exhibited enhanced adsorption efficiency compared to HAp@Fe₃O₄ due to the existence of additional adsorption sites. The equilibrium adsorption isotherms for both Sm(III) and La(III) were fitted well with Langmuir model.The adsorption capacity was found to be 259.06 and 200.80 for La(III) and 413.22 and 476.19 mg/g for Sm(III) on Co/HAp@Fe₃O₄ and HAp@Fe₃O₄respectively. Thermodynamic parameters (∆G°, ∆S°, ∆H°) of La(III) and Sm(III) equilibrium with Co/HAp@Fe₃O₄ indicated a non-spontaneity and endothermic nature. The positive ΔS^o suggested an entropy un-favoured or disorder at the solid/liquid interface.

KEYWORDS:

• Hydroxyapatite
• cobalt oxide
• adsorption
• lanthanides

Acknowledgments

The authors thank all the staff members and colleagues of the Nuclear Fuel Technology Department, Hot Laboratories Centre, Atomic Energy Authority for their cooperation, and useful help offered during this work.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.