Extraction of La, Ce, and Nd using an ionic liquid and its application to rare earth leachate derived from phosphogypsum

• Published in: Journal of rare earths 2024-07
• Main Authors: Tilp, A.H., Akl, Hesham M., T. Kandil, Abd El-Hakim, Cheira, Mohamed F., Gado, Hady Soliman, Salah, Bahaa A.
• Format: Article
• Language: English
• Subjects: Cyphos IL; Ionic liquid; Phosphogypsum; REEs leachate; Solvent extraction
• ISSN: 1002-0721; 2509-4963
• DOI: 10.1016/j.jre.2024.07.005

Rare earth elements (REEs) were extracted from phosphogypsum (PG) using an indirect leaching method that produces CaCO3. The carbonation process transforms PG into CaCO3, and a potential source of value is the (NH4)2SO4 fertilizer. The calcium carbonate byproduct is rich in REEs that are originally present in PG. Calcium carbonate, a byproduct of PG carbonation and a rich source of REEs, could dissolve in nitric acid to produce a calcium nitrate leach solution that contains RE nitrate. Subsequently, the most widely used solvent extraction technique can make use of an environmentally benign nitrate ionic liquid. Cyphos IL 101 (trihexyl(tetradecyl)phosphonium chloride) is transformed into trihexyl(tetradecyl)phosphonium nitrate ([P66614][NO3]) ionic liquid by adding 2.5 mol/L potassium nitrate. The extraction examinations were tested by equilibration of 2 mL of [P66614][NO3] with 2 mL of a synthetic solution of 1000 mg/L of individual La, Ce, and Nd to gain the optimal extraction conditions. The high extraction efficiency of La, Ce, and Nd was gained by stirring a 1/1 aqueous/organic phase ratio and 3 mol/L NH4NO3 (as salting out) at 800 r/min for 40 min at 50 °C to decrease the viscosity of [P66614][NO3]. The La(III), Ce(III), and Nd(III) stripping efficiencies were examined from their loaded [P66614][NO3] ionic liquid by 1/1 A/O ratio of acidified water, 800 r/min stirring speed, and 25 °C. After nine cycles, the extraction and stirring efficiency for the La, Ce, and Nd drop to about 80%. The extraction and stripping parameters are applied to the RE leachate from PG to gain the RE oxide with an assay of 92.67%. Rare earth ions were extracted from phosphogypsum leachate using trihexyl(tetradecyl)phosphonium nitrate ionic liquid, moreover, the rare earth ions were stripped from their loaded ionic liquid. REEs were precipitated from the stripping solution to obtain the rare earth concentrate. [Display omitted]