Purification of crude In(OH) 3 using the functionalized ionic liquid betainium bis(trifluoromethylsulfonyl)imide

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 20; no. 2; pp. 412 - 424
• Main Authors: Deferm, Clio, Luyten, Jan, Oosterhof, Harald, Fransaer, Jan, Binnemans, Koen
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2018
• Subjects: Aluminum; Ascorbic acid; Cadmium; Green chemistry; Heavy metals; Indium; Ionic liquids; Ions; Iron; Leaching; Lead; Nickel; Purification; Separation; Solvent extraction; Stripping; Temperature; Zinc
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/C7GC02958F

The recovery of indium from a crude indium( iii ) hydroxide using the ionic liquid betainium bis(trifluoromethylsulfonyl)imide, [Hbet][Tf 2 N], was investigated. Leaching and solvent extraction were combined in one step using the thermomorphic properties of the [Hbet][Tf 2 N]–H 2 O system. During leaching (80 °C) a homogeneous phase was formed. Upon lowering the temperature below the lower critical solution temperature (UCST), the dissolved metals distributed themselves between the two phases. The optimal leaching/extraction conditions were determined to be a leaching time of 3 hours at 80 °C in a 1 : 1 wt/wt [Hbet][Tf 2 N]–H 2 O mixture. Large separation factors (>100) between In( iii ) and Al( iii ), Ca( ii ), Cd( ii ), Ni( ii ) and Zn( ii ) were obtained implying an easy separation. Fe( iii ), As( v ) and Pb( ii ) are co-extracted. The separation factor between indium and iron was improved to >1000 by addition of ascorbic acid to reduce Fe( iii ) to Fe( ii ). The stripping was done very efficiently by HCl solution. The ionic liquid was regenerated during the stripping step. By combining a prehydrolysis and hydrolysis step, indium( iii ) hydroxide with a purity >99% was obtained.