Solvent Extraction of Molybdenum (Vi) from Aqueous Solution Using Ionic Liquids as Diluents

This work deals with the recovery of Molybdenum (VI) (Mo) from aqueous solutions carried out by solvent extraction (SX) using the bis(2-ethylhexyl) phosphoric acid (D2EHPA) diluted in kerosene and compared with two hydrophobic room temperature ionic liquids (RTILs) as potential replacements of the kerosene. These RTILs were 1-butyl-3-methyl-imidazolium bis (trifluoromethylsulfonyl) imide, [bmim][Tf2N], and 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [omim][Tf2N], because of its excellent properties such as negligible vapor pressure, high hydrophobicity and better extraction capacity than conventional organic diluents. Experimental results indicate that the extraction stoichiometry agrees with a cation exchange with formation of a neutral complex. The use of the selected RTILs as diluents involves higher extraction percentages for the whole measured range of extractant concentration and aqueous-organic ratios, reducing four times the required volume of diluent compared to the experiments carried out with kerosene. Furthermore, the proposed extraction medium offers excellent stripping capacity when a solution of ammonium carbonate is used as a stripping phase. © 2016 Elsevier B.V.