Solvent extraction of dysprosium with Cyanex 923

ABSTRACT

The solvent extraction of dysprosium from an aqueous solution containing 1 g L⁻¹ Dy and 0.2 M NaNO₃ by Cyanex 923 was carried out. From some preliminary experiments, it was observed that the extraction of Dy in the presence of NaNO₃ was more than that in the presence of NaCl and Na₂SO₄. The influence of equilibration time, equilibrium pH, extractant concentration, temperature, salt concentration and stripping agents were investigated. The McCabe–Thiele diagrams for extraction and stripping were constructed with 0.2 M Cyanex 923 and 0.1% sulphuric acid, respectively. The extraction of Dy was 98.4% in three countercurrent stages at pH 1.5 and A:O phase ratio of 2:1. The loaded organic was stripped with HCl, HNO₃ and H₂SO₄ and the stripping efficiencies of these acids followed the trend HCl < HNO₃ < H₂SO₄. The McCabe–Thiele diagram for stripping with H₂SO₄ showed two stages at A:O ratio of 2:3 for quantitative stripping. The species extracted to the organic phase was determined to be $\text{Dy}(\text{N}{\text{O}}_3{)}_3.3\text{Cyanex}923$. The change in enthalpy (ΔH), entropy (ΔS) and free energy change (ΔG) were calculated to be –45.86 kJ mol⁻¹, −120.63 J mol⁻¹K⁻¹ and 33.58 to −39.82 kJ mol⁻¹, respectively. Also, the synergistic effect of D2EHPA, Cyanex 272 and PC88A with Cyanex 923 was investigated.

KEYWORDS:

• Dysprosium
• Cyanex 923
• solvent extraction
• synergistic effect

Acknowledgements

The authors wish to thank Dr I. N. Bhattacharya, HOD, Hydro & Electrometallurgy Department and Prof. B. K. Mishra, Director, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar for their kind permission to publish this paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Ministry of Earth Sciences, Govt. of India, New Delhi.