Solvent Extraction of Rhenium Using Lipophilic N235 in the Hydrophobic Room-Temperature Ionic Liquid

The extraction process of rhenium was investigated in the room-temperature ionic liquid 1-pentyl-3-methylimidazolium bis((trifluoromethane)-sulfonyl)imide ([C5mim][NTf2]) containing N235. At ionic strength ranging from 0.2 to 2.0 mol·kg–1 and temperatures ranging from 293.15 to 318.15 K, the molalities of perrhenate in the aqueous phase were obtained at an extraction equilibrium. The standard extraction constants K0 at diverse temperatures were gained by the Pitzer polynomial approximation method. Thermodynamic characters for the extraction procedure were calculated.