Abstract:
Equilibria of complexation in the ternary systems metal(II) — nitrilotrimethylphosphonic acid — dicarboxylic acid, where metal(II) is cobalt(II) and nickel(II), dicarboxylic acid are oxalic, malonic and succinic acids, has been studied by spectrophotometry at $I = 0.1 (\mathrm{NaClO}_4)$ and $T = (20\pm2)\,^{\circ}$C. It was found that the change in the total concentrations of the reactants and the acidity of the medium leads to flow only competing reactions, without the formation of mixed-complexes. It is shown that the systems M(II) — nitrilotrimethylphosphonic acid — malonic acid with a molar ratio of the reactants of $1:1:5$ are the most effective for practical using from all studied systems. Maximal binding of metal in the complexes in these solutions observed at $3<\mathrm{pH}<11$ for cobalt(II) ions and at $1.8<\mathrm{pH}<11.6$ for nickel(II) ions. It is accompanied by a decrease in the concentration of free metal at $7$–$8$ orders of its initial concentration.
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