Acidified Ionic Liquid Assisted Recovery of Vanadium and Nickel from Oilsands Bitumen

Extraction of vanadium and nickel from diluted oil sands bitumen was investigated. The extraction was performed using HCl acidified ionic liquids, aqueous NaCl diluted ionic liquids, and water diluted ionic liquids to evaluate the relative contributions of acidity, dilution, and ionic strength on the extraction efficiency of ionic liquids. Experiments were conducted with 1-methylimidazolium chloride ([HMIM]-Cl), 1-ethyl-3-methyl imidazolium chloride ([EMIM]-Cl), 1-butyl-3-methyl imidazolium chloride ([BMIM]-Cl), and 1-ethyl-3-methyl imidazolium diethyl phosphate ([EMIM]-DEP). Acid concentration was varied over the range 0.1–10 M, and dilution was varied over the range 2–30 wt %. The study included an evaluation of the change in viscosity on dilution, and it was found that heavy oil viscosity mixing rules could adequately describe the change in viscosity on dilution. The combined effect of the dissociation equilibria and partitioning of the resulting metal containing species between the phases provided a plausible explanation to unify all of the observations in this work. It could explain the differences between vanadium and nickel extraction, as well as the differences in extraction behavior of the ionic liquid mixtures. Acidification of the ionic liquids influenced the dissociation equilibria of the metal ions (VO2+ or Ni2+) and the organic bases, e.g., porphyrins. The anionic species in the ionic liquid (Cl– or [PO4(C2H5)2]−) affected the extent of metal ion exchange and its partitioning between the oil and ionic liquid phases. Nickel was efficiently extracted as the chloride salt. Diethylphosphate was a better counterion to facilitate vanadium extraction.