Stability of binary complexes of Pb(II), Cd(II) and Hg(II) with maleic acid in TX100-water mixtures

Abstract

Binary complexes of maleic acid with toxic metal ions such as Pb(II), Cd(II) and Hg(II) have been studied in 0.0-2.5% v/v tritonX-100 (TX100) - water media at 303 K  at an ionic strength of 0.16 M. The active forms of the ligand are LH₂, LH^- and L^2-. The derived ‘best fit’ chemical speciation models are based on crystallographic R-factors, χ² and Skewness and Kurtosis factors. The predominant species formed are of the type ML₂, ML₂H and ML₃. The trend in variation of complex stability constants with change in the mole fraction of the medium is explained on the basis of prevailing electrostatic and non-electrostatic forces. The species distribution as a function of pH at different compositions of TX100-water mixtures and plausible speciation equilibria are presented and discussed.

KEY WORDS: Maleic acid, TritonX-100, Toxic metal ions, Mole fraction, Binary complexes

Bull. Chem. Soc. Ethiop. 2014, 28(3), 383-391.

DOI: http://dx.doi.org/10.4314/bcse.v28i3.7