Complexation of N-tris[(1,2-dicarboxyethoxy)ethyl]amine with Ca(II), Mn(II) and Zn(II) in aqueous solution

In a search for environmentally friendly metal chelating ligands for industrial applications, the protonation and complex formation equilibria of N-tris[(1,2-dicarboxyethoxy) ethyl] amine (TCA6) with Ca(II), Mn(II), Cu(II) and Zn(II) ions in aqueous 0.1 M NaCl solution were studied at 25 degrees C by potentiometric titration. A model for complexation and stability constants of the complexes were determined. With all of the metals, complex formation was dominated by ML4-. Comparison of TCA6 and six other chelating agents showed TCA6 to be suitable for applications where strong calcium binding is essential.