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

M Ramanaiah,S G Sri,B B V Sailaja

doi:10.4314/bcse.v28i3.7

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 LH 2 , LH - and L 2- . The derived ‘best fit’ chemical speciation models are based on crystallographic R-factors, χ 2 and Skewness and Kurtosis factors. The predominant species formed are of the type ML 2 , ML 2 H and ML 3 . 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

Highlights

The toxicity, bio-availability, bio-degradability, bio-accumulation, persistence, mobility, solubility, extractability and many other critical properties of chemical species depend on their form and nature [1,2,3]
This paper reports a speciation study of binary complexes of Pb(II), Cd(II) and Hg(II) with maleic acid using nonionic micelles to stabilize intermediates
The following conclusions have been drawn from the modeling studies of the speciation of binary complexes of Pb(II), Cd(II) and Hg(II) with maleic acid in TX100-water mixtures

Summary

INTRODUCTION

The toxicity, bio-availability, bio-degradability, bio-accumulation, persistence, mobility, solubility, extractability and many other critical properties of chemical species depend on their form and nature [1,2,3]. The International Union of Pure and Applied Chemistry (IUPAC) [4] has differentiated ‘speciation’ from ‘functionality’ by defining speciation as the process yielding evidence of the molecular form of an analyte Even if this is the objective of all studies, operationally speciation is determined by the physicochemical properties of the real natural entities. By binding the metal ions electrostatically to the negatively charged micellar surface, their effective concentration is substantially increased. It has been demonstrated that water insoluble metal chelates can be solubilised with a micellar solution of non-ionic surfactant such as TX100. This solubilisation technique is frequently utilized in analytical procedures [8]. The effect of variation in asymmetry potential, liquid junction potential, activity coefficient, sodium ion error and dissolved carbon dioxide on the response of the glass electrode was accounted for by a correction factor [12, 13]

Analytical procedures

RESULTS AND DISCUSSION

CONCLUSION