Helena Hyvönen

Complexation of [S,S] and mixed stereoisomers of N,N′-ethylenediaminedisuccinic acid (EDDS) with Fe(III), Cu(II), Zn(II) and Mn(II) ions in aqueous solution

The protonation and complex formation equilibria of N,N′-ethylenediaminedisuccinic acid (EDDS) in the isomeric form [S,S] and a mixture of EDDS isomers (25% [S,S], 50% [R,S], 25% [R,R]) with Fe(III), Cu(II), Zn(II) and Mn(II) have been studied in aqueous 0.1 M NaCl solution at 25 °C by potentiometric titrations. The calculations were carried out with the computer program SUPERQUAD.

Studies on biodegradable chelating ligands: complexation of iminodisuccinic acid (ISA) with Cu(II), Zn(II), Mn(II) and Fe(III) ions in aqueous solution

In a search for biodegradable chelating ligands for industrial applications, study was made of the protonation and complex formation equilibria of iminodisuccinic acid (ISA) as a mixture of two of its stereoisomers (50% [S,S] and 50% [R,S]) with Cu(II), Zn(II), Mn(II) and Fe(III) ions in aqueous 0.1 M NaCl solution by potentiometric titration at 25 °C. The model of the complexation and the stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. With all metals the complex formation was dominated by stable MLn − 4 complexes. Biodegradable and of low nitrogen content, ISA was found to be a good chelating agent in pulp bleaching.

Complexation of 3-hydroxy-2,2′-iminodisuccinic acid (HIDS) with Mg2+, Ca2+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+ ions in aqueous solution

In a search for environmental-friendly metal chelating ligands for industrial applications, the protonation and complex formation equilibria of 3-hydroxy-2,2′-iminodisuccinic acid with Mg2+, Ca2+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+ ions in aqueous 0.1 mol L−1 NaCl solution were studied at 25°C by potentiometric titration. The model for complexation and the stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. In all cases, complex formation was dominated by stable ML n −4 complexes.

Complexation of N-tris[(1,2-dicarboxyethoxy)ethyl]amine with Ca(II), Mn(II), Cu(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°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.

Complexation of [S,S,S]- and [R,S,R]-isomers of N-bis [2-(1,2-dicarboxyethoxy)ethyl] aspartic acid with Mg(II), Ca(II), Mn(II), Fe(III), Cu(II) and Zn(II) ions in aqueous solution

In a search for environmentally friendly metal chelating ligands for industrial applications, the protonation and complex formation equilibria of [S,S,S]- and [R,S,R]-isomers of N-bis[2-(1,2-dicarboxyethoxy)ethyl] aspartic acid (BCA6) with Mg(II), Ca(II), Mn(II), Fe(III), Cu(II) and Zn(II) ions in aqueous 0.1 M NaCl solution were studied at 25°C by potentiometric titration. The model for complexation and the stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. With all metal ions (M n+), stable ML n−6 complexes dominated complex formation for both isomers. Differences in complexation models were found for binuclear species.

The complexation of novel amino acid derivatives with La(III) ion in aqueous solution

In a search for environmentally friendly metal chelating ligands the complex formation equilibria of N-bis[2-(1,2-dicarboxyethoxy)ethyl] glycine (BCA5), N-bis[2-(1,2-dicarboxyethoxy)ethyl] aspartic acid (BCA6), and N-tris[(1,2-dicarboxyethoxy)ethyl] amine (TCA6) with La(III) in aqueous 0.1 M NaCl solution were studied at 25°C by potentiometric titration. The models of the complexation and stability constants of the different complexes were determined using the computer program SUPERQUAD. With TCA6 and BCA6 complex formation was dominated by stable LaL3− and with BCA5 by LaL2− complexes.

Complexation of N-bis[2-(1,2-dicarboxyethoxy)ethyl]aspartic acid with Cd(II), Hg(II) and Pb(II) ions in aqueous solution

The persistence of widely used chelating agents EDTA and DTPA in nature has been of concern and there is a need for ligands to replace them. In a search for environmentally friendly metal chelating ligands for industrial applications, complex formation equilibria of N-bis[2-(1,2-dicarboxyethoxy)ethyl]aspartic acid (BCA6) with Cd(II), Hg(II) and Pb(II) in aqueous 0.1 M NaNO3 solution were studied at 25°C by potentiometric titration. Complexation was modeled and the stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. With all metal ions, stable ML4− complexes dominated the complex formation. The stabilities of Cd(II), Hg(II) and Pb(II) chelates of BCA6 are remarkably lower than those of EDTA and DTPA. Environmental advantages of the use of BCA6 instead of EDTA and DTPA are better biodegradability and lower nitrogen content with a possibility to save chemicals and process steps in pulp bleaching.

Complexation of some environmentally friendly carboxylic acid ligands with La3+ ion in aqueous solution

In search for environmentally friendly metal chelating ligands for industrial applications, protonation, and complex-formation equilibria of iminodisuccinic acid (IDS), 3-hydroxy-2,2′ -iminodisuccinic acid (HIDS), N,N′-ethylenediaminedisuccinic acid (EDDS), and oxydisuccinic acid (ODS) with La3+ in aqueous 0.1 mol L−1 NaCl solution were studied at 25°C by potentiometric titration. The model for complexation and the stability constants of the different complexes were determined using the computer program SUPERQUAD. Complex formation was dominated by stable LaL− complexes for all tested ligands.

Complexation of iminodisuccinic acid (IDS) and 3-hydroxy-2,2′-iminodisuccinic acid (HIDS) with Cd2+, Hg2+, and Pb2+ in aqueous solution

In a search for environmentally friendly metal-chelating ligands for industrial applications, the protonation and complex formation equilibria of iminodisuccinic acid (IDS) and 3-hydroxy-2,2′-iminodisuccinic acid (HIDS) with Cd2+, Hg2+, and Pb2+ in aqueous 0.1 mol L−1 NaNO3 solution were studied at 25°C by potentiometric titration. Models for complexation and stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. In all cases, complex formation was dominated by stable ML2− complexes.

Complexation of pyrazine-2-carboxamidoxime with Cu(II), Ni(II), Co(II), Zn(II), and Cd(II) ions in aqueous solution

The protonation and complex formation equilibria of pyrazine-2-carboxamidoxime with Cu(II), Ni(II), Co(II), Zn(II), and Cd(II) ions in aqueous 0.1 mol L−1 NaCl solution were studied at 25 °C by potentiometric titration. The model for complexation and the stability constants of the different complexes were determined for each metal ion using SUPERQUAD.