Selective removal of iron(III) from highly salted chloride acidic solutions by solvent extraction using di(2-ethylhexyl) phosphate

Abstract

Metal ions including Fe³⁺, Ca²⁺, Mg²⁺, Ni²⁺, Co²⁺ and Cu²⁺ are commonly found in the leaching solution of laterite-nickel ores, and the pre-removal of Fe³⁺ is extremely important for the recovery of nickel and cobalt. Di(2-ethylhexyl)phosphate acid (D2EHPA) showed high extraction rate and selectivity of Fe³⁺ over other metal ions. The acidity of the aqueous solution is crucial to the extraction of Fe³⁺, and the stoichiometry ratio between Fe³⁺ and the extractant is 0.86:1.54. The enthalpy for the extraction of Fe³⁺ using D2EHPA was 19.50 kJ/mol. The extraction of Fe³⁺ was ≥99% under the optimized conditions after a three-stage solvent extraction process. The iron stripping effects of different reagents showed an order of H₂C₂O₄>NH₄HCO₃>HCl>NaCl>NaHCO₃>Na₂SO₃. The stripping of Fe was ≥99% under the optimized conditions using H₂C₂O₄ as a stripping reagent.

Key words： solvent extraction; iron; di(2-ethylhexyl)phosphate acid; separation

Acknowledgements

This work has been financially supported by the National Key Research and Development Program of China (Grant No. 018YFC1900502), Key Research Program of Frontier Sciences of Chinese Academy of Sciences (Grant No. QYZDJ-SSW-JSC021), the National Natural Science Foundation of China (Grant Nos. 21606241, 51804289 and 51774260), and CAS Interdisciplinary Innovation Team. We also acknowledge the help from Professor Geoffrey W. Stevens with revising the manuscript.

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