“Green” Chemical Separation of ［RuI4-］ by Extraction from a Phase-Separation System of C2H5OH-H2O-(NH4)2SO4

It was found that Ru3+ in the form of ［RuI4-］ can be separated by extraction from a phase-separation system of C2H5OH-H2O mixture with optimum volumic ratio of 3 to 7 (e.g., mix 3.0 mL of C2H5OH with 7.0 mL of H2O) in which solid (NH4)2SO4 is added to attain to a concentration of 0.3 g·mL-1 ［i.e. 3 g of (NH4)2SO4 in 10 mL of solution］ and KI is added to attain a concentration of 3.0×10-3mol·L-1. When this mixture is shake thoroughly, phase-separation between C2H5OH and H2O takes place giving a clear interface between the 2 phases, and ［RuI4-］ enters into the C2H5OH phase in form of an association complex of ［RuI4-］［C2H5OH2+］. Optimum acidity of the extraction system was found in the range of pH 0.5 to 4.4. Separation of Ru3+ from binary and multiple mixture with 12 other metal ions (Al3+, Zn2+, Mn2+, Pb2+, Ni2+, Cr3+, Ga3+, Co2+, Fe3+, Mg2+, Ag+ and V5+) was tested further, giving satisfactory results with values of recovery of Ru3+ range from 98.9% to 99.5%. It was shown that the proposed method is beneficial to environmental protection, as it prevents the use of harmful organic solvents.