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 di luted with kerosene with tri-n-butyl phosphate (TBP) employed as a phase mo difier. 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 pos sible separation of cobalt and nickel. Increasing the concentration of Na-C yanex 272 increased the percentage extraction of both metal ions. The speci es 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 nicke l while for cobalt, the percentage extraction increased up to 303 K, beyond which the extraction decreased. Separation factors obtained with binary mi xture 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 al one. (C) 1999 Elsevier Science B.V. All rights reserved.