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.