Precipitate Formation of Nickel 8-Quinolinol Complexes from Solutions Containing Perchlorate and Sulfate Ions

Abstract

Based on the fact that several kinds of anions take part in the solvent extraction of nickel with 8-quinolinol(Hql), the precipitate formation of nickel 8-quinolinol complexes was examined using aqueous nickel(II) solutions containing perchlorate and sulfate anions. The precipitate formed at pH 4.0 from the perchlorate solution contains a large amount of perchlorate ions; its mole ratio of nickel, 8-quinolinol and perchlorate ion is close to 1:3:0.5, which is that of the dimeric ion-pair complex, [Ni₂ql₃(Hql)₃]ClO₄. The precipitate formed at pH 9.0 contains no perchlorate ion; it seems to be the mixture of Niql₂2Hql and Niql₂2H₂O. On the other hand, the precipitate formed from the sulfate solution contains no sulfate ions, regardless of pH. The precipitates formed in the range of pH 4-8 seem to be a mixture of Ni₂ql₄2Hql, Niql₂2Hql or Niql₂2H₂O according to pH, but the precipitate for pH 9.0 is Niql₂2H₂O. The composition of these precipitates was ascertained and is discussed on the basis of the results of their TG-DTA and IR spectra.