Effect of triton-X100 on ternary complexes of cobalt(II), nickel(II), copper(II) & zinc(II) with aspartic and citric acids

Abstract

A computer based investigation has been made pH-metrically on the chemical speciation of mixed ligand complexes in ternary systems consisting of cobalt(II), nickel(II), copper(II) and zinc(II) with aspartic and citric acids in various concentrations (0.0–2.5% v/v) of the triton-X 100 surfactant solution maintaining an ionic strength of 0.16 mol dm^-3 with sodium hydroxide at 303.0+0.1 K. These ligands interact with the metal ions to form MLXH^2-, MLX₂H^4- and MLX^3- species. The trend of the variation in log β values with changing dielectric constant as well as with mole fraction of the surfactant is explained based on the electrostatic interactions of the side chains of the ligands, charge neutralization, chelate effect, stacking interactions and hydrogen bonding. The existence of different ternary species is established from modelling studies using the computer program MINIQUAD75. Distribution diagrams with different pH-compositions of surfactant and structures of plausible ternary complexes are also presented.