EXTRACTION, SEPARATION, AND DETERMINATION OF NICKEL AND BISMUTH WITH 1-(2-PYRIDYLAZO)-2-NAPHTHOL IN AQUEOUS THIOCYANATE MEDIA

Nickel(II) and bismuth(III) are quantitatively extracted from aqueous thiocyanate solutions, adjusted to pH 4.0-9.0 and 3.5-5.0, respectively, using solutions of 1-(2-pyridylazo)-2-naphthol (PAN) in tri-n-butyl phosphate (TBP). The extracted species of nickel and bismuth have the formulas [Ni(PAN)SCN].4TBP and [Bi(PAN)SCN]X-TBP, respectively. Polyurethane foam treated with TBP solution containing PAN is used successfully for the quantitative retention and recovery of nickel and bismuth from aqueous thiocyanate solutions in the column extraction mode. The preconcentration of small amounts (10 mug) of nickel and bismuth from dilute aqueous solutions (1 L) is also possible, with a recovery of 95-97%. The feasibility of using PAN-foam for selective detection and semiquantitative determination of nickel and bismuth in aqueous thiocyanate media is examined. The detection limits of nickel and bismuth by the foam batch method are 0.05 and 0.50 ppm, respectively. Lower concentrations of these metal ions are easily detected in dynamic tests using PAN-foam columns. Semiquantitative determination of nickel and bismuth is also achieved in both the batch and column methods by using the appropriate color scales.