RECOVERY OF INDIUM (III) FROM MIXED HYDROCHLORIC ACID - SULPHURIC ACID MEDIA BY SOLVENT EXTRACTION WITH CYANEX 301®

Publisher Website
Google Scholar
Abstract
The solvent extraction of indium(III)from mixed 0.5 to 1 mol.L hydrochloric acid + 2 to 4 mol.L−1 sulphuric acid solutions simulating flue dust leaching solutions was investigated. In addition to In(III) typically present at about 1 g.L-', the flue dust leaching solutions contain As(III), Cd(II), Cu(II) Fe(IH) and Zn(II), with concentrations ranging between 3 and 25 g.L*1. After preliminary investigation, bis(2,4,4-trimethylpentyl)phosphinodithioic acid Cyanex 301® was selected as extractant. Indium(III) is efficiently extracted by Cyanex 301® in the range of hydrochloric acid and sulphuric acid concentrations encountered in the flue dust leaching solutions. However, such an extraction is not at all selective with respect to As(III), Cd(II), Cu(II) and Fe(III), and only partially selective with respect to Zn(II). Thus, it is recommended to eliminate As(III) and Cu(II) from the solutions by cementation ori iron prior to extraction of In(III) by Cyanex 301(r). Moreover, during the cementation of arsenic and copper, iron(III) is reduced into iron(II) which is not extracted by Cyanex 301®from such acidic solutions. As a result, only Cd(II) and, at a lesser degree, Zn(III) interfere with the extraction of In(III). In fact, these two metal species can be separated from indium(III) by selective stripping in appropriate hydrochloric acid media (typically 4.5 - 5 mol.L1HCI). Finally, indium(III) can be recovered from the organic Cyanex 301®solution by stripping with a more concentrated (typically 7 mol.L-')hydrochloric acid solution.