Chemical speciation of ethylenediamine-N,N′- disuccinic acid (EDDS) and its metal complexes in solution
1999
Whitburn, Joanne S. | Wilkinson, Stephen D. | Williams, David R.
Computer simulation of chemical speciation has been used to assess the ability of the readily-biodegradable ligand SS-EDDS⁴⁻ to replace the non readily-biodegradable ligand EDTA⁴⁻. Potential replacement ligands for EDTA⁴⁻, from the EDDS⁴⁻ homologous series, which are readily biodegradable were assessed for their technical compatibility with EDTA⁴⁻ using chemical speciation analysis based upon computer modelling. Chelating agents considered were EDTA(ethylenediaminetetraacetic acid), EDDS (ethylenediamine-N,N’-disuccinic acid), EDDM (ethylenediamaine-N,N’-dimalonic acid), and EDDG (ethylenediamine-N,N’-diglutaric acid) all producing 4-anionic ligands upon deprotonation. Formation constants with Ba²⁺, Sr²⁺, Mg²⁺, Ca²⁺, Mn²⁺, Cd²⁺, Co²⁺, Zn²⁺, Pb²⁺, Ni²⁺ , Cu²⁺, Hg²⁺ and Fe³⁺ions are listed (Table 2), some being determined as part of this study. The speciation modelling suggests that varying the total concentration conditions and using a limited supply of the EDDS ligand can, relative to EDTA, increase the complexing of Cu²⁺ in the presence of other ions, by a factor of 13, giving rise to the ‘more for less’ concept.
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