Abstract

The liquid-liquid extraction of samarium (III) from aqueous nitrate solution using D2EHPA (di-2-ethylhexyl phosphoric acid) as extractants is investigated to recover samarium (III) from aqueous solution. The effect of operating parameters, such as time, nitrate ion, aqueous phase acidity, concentration of the extractant, temperature on the samarium extraction. At pH=5.05, maximum extraction efficiency was obtained with 2 mmol L^-1 D2EHPA in dichloromethane at initial concentration of Sm³⁺ 1 mmol L^-1. D2EHPA extracts Sm³⁺ very rapidly. Equilibrium was reached within 15 min. The synergistic effect showed that addition of D2EHPA to TOP (Tri-iso-octyl-phosphate) extraction was obtained for the volume ratio 4.5/0.5. The thermodynamic functions like free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) of extraction mechanism are discussed. By liquid-liquid extraction the removed quantity was 93.26 mg g^-1. The stripping efficiency was found to be quantitative in HNO₃ and HCl 1 M. The robustness of the procedure is demonstrated by the average recoveries obtained (>99.6 %) for samarium (III).

Keywords: Samarium (III); D2EHPA; Optimization; Extraction