Complexation of Nickel with 2-(Aminomethyl)pyridine at High Zinc Concentrations or in a Nonaqueous Solvent Mixture

Abstract

Complexation of Ni2+ with 2-(aminomethyl)pyridine (amp) has been studied at 22 °C using absorption spectroscopy. Effect of high Zn2+ concentration on complex formation in aqueous sulfate solutions and complexation of Ni(ClO4)2 with amp in a nonaqueous methanol/2-methoxyethanol mixture were investigated. The spectra were analyzed using least-squares minimization technique (LS) and partial least-squares method (PLS) to obtain the stability constants and distribution of the complex species. Moreover, complex formation was studied qualitatively by means of continuous variation analysis. The data measured at zinc concentrations of 0.100–1.84 mol·kg–1 indicate only minor deviations from the equilibria calculated using literature stability constants. At the highest zinc concentration, the equilibrium is slightly shifted to higher complexes but no evidence was found of changes in the octahedral complex geometry. Octahedral 1:1, 1:2, and 1:3 complexes were observed also in the nonaqueous solvent mixture but the stability constants were smaller than in aqueous solutions. Moreover, the equilibrium was shifted toward higher complexes, and a higher concentration of the 1:3 complex was obtained in nonaqueous than in aqueous solution. The results are discussed in view of the separation of nickel from concentrated ZnSO4 solutions and of the design of ion-imprinted materials.