Hydrolysis‐Induced Reactive Extraction of Neodymium by Fluorinated Imidazolium–Based Ionic Liquid System: Evidence of In Situ Formation of NdF 3

The extraction behavior of trivalent neodymium ions was investigated using undiluted imidazolium–based hydrophobic ionic liquids (IL's), that is, 1‐Butyl‐3‐methylimidazolium hexafluoro phosphate [C 4 mim][PF 6 ] in a liquid–liquid biphasic extractive mass transfer system. The extraction behavior has been studied by varying several parameters such as the pH, concentration of the nitrate ion in the aqueous phase, concentration of the ionic liquid cation as well as anion, contact time, and temperature. ICP‐AES and UV–visible absorption spectroscopy were employed to determine the amount of Nd +3 in aqueous as well as ionic liquid phases, subsequently used for calculation of extraction efficiency. The extraction exhibited strong dependency on acidity, temperature, and nitrate ion concentration, and unprecedented extraction efficiencies upto 99% were observed under optimum conditions of 1 M HNO 3 with a contact time of 30–60 min. Detailed physiochemical investigation revealed that apparent high extraction efficiency was driven by in situ precipitation of NdF 3 via release of fluoride ion from the hydrolysis of anion of the ionic liquid. Another observation correlates with decreasing extraction efficiency with an increase in nitrate ion concentration in the aqueous phase, supporting the mechanistic interpretation and competitive complexation. Powder x‐ray diffraction analysis of postextraction solid residues confirmed the formation of NdF 3 as the dominant phase. Thermodynamic studies have been carried out to check the feasibility of the process, revealing that the extraction was endothermic in nature with Δ H 0  ˜ 83.64 kJ mol −1 and is also spontaneous at STP (Δ G 0  ∼−1.94 kJ mol −1 ).