Solvent Extraction of Scandium from the Waste Solution of TiO2 Production Process

• Published in: Transactions of the Indian Institute of Metals 2017-03, Vol.70 (2), p.471-477
• Main Authors: Shibata, J., Murayama, N.
• Format: Article
• Language: English
• Subjects: Aqueous solutions; Chemistry and Materials Science; Corrosion and Coatings; Hydrogen bonds; Infrared spectroscopy; Isotherms; Materials Science; Metallic Materials; Scandium; Separation; Solvent extraction; Solvent extraction processes; Stripping; Sulfuric acid; Technical Paper; Titanium dioxide; Titanium oxides; Tribology; Wastewater; Zirconium
• ISSN: 0972-2815; 0975-1645
• DOI: 10.1007/s12666-016-1008-3

Extraction and stripping properties of Sc 3+ were investigated by using a mixed extractant of Versatic Acid 10 (VA10) and Tri-n-butyl phosphate (TBP). The effect of adding TBP to VA10 was considered by analyzing the binding state of VA10 and TBP by FT-IR. Solvent extraction of scandium from an aqueous solution of Sc 3+ –Ti 4+ –Zr 4+ , which simulated waste water from the titanium oxide manufacturing process, the Bayers process and others, was performed, and the separation factor of Sc 3+ over Ti 4+ and Zr 4+ was investigated. To clarify the operating conditions of a countercurrent multistage process for Sc 3+ , McCabe–Thiele analysis was applied to the extraction isotherm and stripping isotherm of Sc 3+ . The extraction pH of Sc 3+ was found to shift to higher pH, and Sc 3+ was stripped at a lower concentration of H 2 SO 4 by adding TBP to VA10. Addition of TBP to VA10 suppresses the extraction of Sc 3+ and promotes the stripping of Sc 3+ . IR spectra of the organic phase suggested that the dimeric portion of VA10 formed hydrogen bonds with TBP. The extractions of Sc 3+ , Ti 4+ and Zr 4+ were 77, 3 and 8%, respectively. The separation factors of these metal ions were β Sc/Ti  = 100 and β Sc/Zr  = 38 at pH4.6 on extraction with VA10 + TBP from aqueous solutionof Sc 3+ –Ti 4+ –Zr 4+ . Stripping efficiency of 100, 8 and 22% could be achieved for Sc 3+ , Ti 4+ and Zr 4+ , respectively by using 0.5 mol/dm 3 H 2 SO 4 . From these results, it was possible to separate Sc 3+ from impurities such as Ti 4+ and Zr 4+ by countercurrent multistage extraction, and Sc 3+ was recovered by one-stage stripping with 0.5 mol/dm 3 H 2 SO 4 . Extraction of Sc 3+ from the dilute aqueous solution containing 500 mg/dm 3 of Sc 3+ reached 99% at the flow ratio (A/O) = 1.01 in the two-stage countercurrent extraction, and Sc 3+ in the organic phase was stripped to attain a six-fold concentration by applying one-stage stripping with flow ratio of (O/A) = 6.00.