Abstract

BEYER, Lothar; DIETZE, Frank; GONZALEZ, María José  and  MUHAMMED, Mamoun. A study on the complexation of picolinic acid derivatives with Cd²⁺, Ni²⁺ AND Zn²⁺. Rev. Soc. Quím. Perú [online]. 2010, vol.76, n.1, pp.7-24. ISSN 1810-634X.

In the present study we report the complexation of picolinic acid and two of its derivatives, 4-(3-heptyl)pyridine-2-carboxylic acid (43HP2CA) and 6-(3-pentyl)pyridine-2-carboxylic acid (63PP2CA) with Ni2+, Zn2+ and Cd2+. The acid dissociation of the three ligands and complex formation constants with these metal ions were determined by potentiometry in dioxane/water 75% (v/v) as solvent at 25oC. The complexation of either ligands with the metal ions studied follows the order Ni2+ > Zn2+ > Cd2+. The acid dissociation constants of 43HP2CA measured potentiometrically in various dioxane/water mixtures with a composition in the range of 85-15% (v/v), show that the pK_a value increases with the increase of the concentration of dioxane in the medium. The stability constants of 4-(3-heptyl)pyridine-2-carboxylic acid with Zn2+ and Cd2+ were estimated in water solutions at different temperatures and it was found that the processes were exothermic in both cases.

Keywords : extraction of cadmium; nickel and zinc; picolinic acids; acid dissociation; stability constants.

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