Selective recovery of rhenium from molybdenite flue-dust leach liquor using solvent extraction with TBP

The selective extraction of rhenium from the leach liquor of molybdenite roasting flue-dust and its subsequent stripping were investigated using the solvent extraction technique. In this study, tri-butyl phosphate (TBP) as organic extractant in kerosene and metals bearing solution (in mg/L: 6042 Mo, 208 Re, 534 Cu, 1982 Fe, 32 Mg, and 19 Pb) were used as the organic and aqueous feed, respectively. The extraction curve as a function of equilibrium pH depicted the maximum separation of rhenium at high acid concentration, i.e., pHeq(ext.) = −0.3. The variation of TBP concentration and pHeq(ext.) revealed the formation of [HReO4⋅3TBP] adduct in the organic phase. A quantitative rhenium extraction (>99.6%) could be yielded while contacting the metal-bearing aqueous with 0.65 mol/L TBP at unit phase ratio, as predicted by the McCabe-Thiele diagram for extraction isotherm. A study on thermodynamic parameters indicated for the spontaneity of exothermic extraction process. The stripping of rhenium from loaded TBP as a function of pH yielded an efficient recovery at pHeq(strip) ≥ 3.0. On a metal-to-metal basis the selective recovery of >99% rhenium has demonstrated the potential of present work.