Extraction studies of cobalt (II) and nickel (II) from chloride solutions using Na-cyanex 272. Separation of Co(II)/Ni(II) by the sodium salts of D2EHPA, PC88A and Cyanex 272 and their mixtures

Solvent extraction studies of cobalt and nickel have been carried out from 1 M chloride solutions using the sodium salt of Cyanex 272 as extractant diluted with kerosene with tri-n-butyl phosphate (TBP) employed as a phase modifier. Extraction of metal ions increases with increasing aqueous phase pH. The pH(0.5) value difference of 1.25 with Na-Cyanex 272 indicates the possible separation of cobalt and nickel. Increasing the concentration of Na-Cyanex 272 increased the percentage extraction of both metal ions. The species extracted into the organic phase appears to be associated with 2 mol of extractant. The observed loading capacity of 99.5% for cobalt and 83.7% for nickel with 0.025 M Na-Cyanex 272 indicates that the extractant is pure in form. Increase of temperature increases the percentage extraction of nickel while for cobalt, the percentage extraction increased up to 303 K, beyond which the extraction decreased. Separation factors obtained with binary mixture of extractants gave a Value 5.6 times higher in the case of Na-PC88A as extractant and Na-Cyanex 272 as synergist than that for Na-Cyanex 272 alone. (C) 1999 Elsevier Science B.V. All rights reserved.