Carbonate and bicarbonate trace metal complexes: Critical reevaluation of stability constants

The anions HCO3- and CO32- could play a major complexing role for trace metals in CO2 rich thermomineral water. The aim of this paper is to provide a complete thermochemical data set concerning the aqueous complexes of some divalent metal complexes (Fe, Mn, Ni, Co, Cu, Pb, Zn, Cd) with the ligands HCO3- and CO32-. When not previously determined experimentally, stability constants and enthalpies of formation of the complexes were estimated at 25°C from empirical correlations or theoretical approaches. The distribution of the trace metal species in typical water samples is given, indicating that the importance of complexes with bicarbonate cannot be neglected in that type of water.