A non-aqueous solvent extraction (NASX) process for the separation of cobalt and nickel from ethylene glycol and glycerol/water feed solutions using the ionic liquid Cyphos IL 101 has been investigated. The use of undiluted Cyphos IL 101 was critically assessed and compared with solvent extraction systems in which toluene, p-cymene, Shellsol A150, and Shellsol GS190 were used as diluents. While the extraction of cobalt(II) chloride from aqueous solution was possible only at high chloride concentrations, extraction percentages of cobalt higher than 80 % were observed from ethylene glycol and glycerol/water feeds containing 0.8 mol center dot L-1 NaCl. Separation factors over 40,000 for cobalt and nickel could be achieved for extraction with undiluted Cyphos IL 101 from 2.4 mol center dot L-1 NaCl ethylene glycol and 1.6 mol center dot L-1 NaCl glycerol feeds. The distribution ratio of cobalt increased with increasing temperatures in both NASX systems. Studies on the mutual solubility showed that Cyphos IL 101 is highly soluble in ethylene glycol at 21 degrees C (i.e. phosphorus contents up to 432 mg center dot L-1), but it turned out that impurities contributed for 400 mg center dot L-1 to this value. On the other hand, only 87 mg center dot L-1 of Cyphos IL 101 dissolved in glycerol at 21 degrees C. Finally, a conceptual flowsheet for the separation of cobalt and nickel by NASX is presented, including extraction, stripping, and recovery of the solvents.
