Complexes of Pb(II), Cd(II) and Hg(II) with L-phenylalanine in the presence of non-ionic surfactants, at an ionic strength of 0.16 mol dm -3 and temperature 303 K are investigated pH-metrically. The existence of different binary complex species is established from modelling studies using the computer program MINIQUAD75. The increased stability of the complexes with increasing micellar content is explained by electrostatic forces. The influence of the micelles on the chemical speciation is discussed based on the mole fraction of the medium. Distribution diagrams of various species of the complexes in relation to pH are presented.
Complexation of toxic metal ions with maleic acid in (0.0-2.5% w/v) cetyltrimethylammonium bromide (CTAB)-water mixtures has been studied pH-metrically at ambient conditions and an ionic strength of 0.16 mol L -1 . The existence of different binary species was established from modelling studies using the computer program MINIQUAD75. The best-fit chemical models were selected based on statistical parameters such as the crystallographic R factor and sum of the squares of residuals in mass-balance equations. The models for binary complex systems contain the chemical species ML 2 , ML 2 H and ML 3 for Pb(II), Cd(II) and Hg(II) in CTAB-water mixtures. The trend in the variation of stability constants with change in the mole fraction of the medium was explained based on electrostatic and non-electrostatic forces. Distribution of the species with pH at different compositions of CTAB-water mixtures was also presented.
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, χ 2 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.
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