Humic Acid Binding of Trivalent Tl and Cr Studied by Synchronous and Time-Resolved Fluorescence.

The complexation of Tl(III) and Cr(III) with groundwater humic acids (HA) was investigated at pH 4.5 and 5.5 using different fluorescence methods. These comprised both quenching measurements of the continuous and synchronous fluorescence of the HA ligand, and an ion competition method based on the time-resolved laser-induceed fluorescence of HA-bound Eu(III). Modelling of the experimental data using an electrostatic discrete site approach (Model V) yielded comparable values of intrinsic binding constants for each of the studied metal, independently of sample conditions (pH, metal: ligand ratio) and fluorescence method used. The results confirmed the validity of fluorescence techniques in the analysis of low concentration metal ion-HA interactions, and also indicated that, besides the aquo ion and the first hydroxo complex, also other species may bind to humic acids.

BIDOGLIO Giovanni;  FERRARI D.;  SELLI Elena;  SENA Fabrizio;  TAMBORINI Giordano; 

1997-09-18

JRC15356

https://publications.jrc.ec.europa.eu/repository/handle/JRC15356,