Complexation of Am(III) with Humic Acids of Different Origin

Abstract

The complexation of Am(III) with two humic acids from different origins has been investigated in 0.1 Μ NaC10 4 at pH = 6.0 by UV spectroscopy and radiometric measurement. Both humic acids, extracted from Gorleben groundwater and purchased from Aldrich Co., are purified, protonated and characterized previously. Loading capacities of two humic acids for the Am 3 + ion are determined and taken into account for the evaluation of complexation constants. Experiment verifies a tridentate complexation of Am(III) for both humic acids. The complexation constants are found to be log β = 6.44 + 0.15 Lmol -1 for Gorleben humic acid and log β = 6.39 ±0.14 L moP 1 for Aldrich humic acid.

Europium-binding abilities of dissolved humic substances isolated from deep groundwater in Horonobe area, Hokkaido, Japan

“…Combining Equations (5)- (10), the fraction of the ligand bound can be expressed as Equation (11). (5)- (10), and approximating the term [NO 3 …”

“…Since the extent of binding of radionuclides to deep groundwater HSs is a factor in the degree of the effect, an understanding of this process is an essential subject. In previous studies, the binding abilities of radionuclides have been extensively investigated for HSs isolated from deep groundwaters in a sedimentary rock layer in Gorleben, Germany, and in granitic rock layers in Fja¨llveden, Sweden, and Fanay-Auge`res, France [3][4][5]. These studies indicated that deep groundwater HSs had same degree of affinities for binding radionuclides as HSs obtained from Aldrich and from surface environments.…”

Speciation of Radionuclides in the Environment

“…PbOH + or PbCl + and to adsorption on or co-precipitation with colloidal particles in groundwaters [213], Strong hydrolysis of thorium and polonium, and the extremely low solubility of their oxides/hydroxides are the reason why 232 Th, 230 Th and 2W Po migrate in groundwaters mainly in colloidal forms [214][215][216], Underground repositories of radioactive wastes and the transport of radionuclides from contaminated soils or surface waters may represent significant sources of artificial radionuclides in groundwaters. Release and migration of radionuclides from nuclear wastes strongly depend on their chemical composition and on the speciation of the released radionuclides.…”

“…Colloids may be released from nuclear wastes, or may be formed by precipitation of sparingly soluble compounds of radionuclides and by association of radionuclides with inorganic or organic colloids ('Fremdkolloide', [226,227]) present in groundwaters [214,[228][229][230] [231] were able to show that U(VI), Am(III), Cm(III), and Th were strongly sorbed to aquatic colloids, rich in humic and fulvic substances, whereas Np(V) was negligibly sorbed to these colloids.…”

“…Both elements form insoluble hydroxides which are strongly sorbed by surfaces. Americium and curium are also known for the formation of stable complexes with organic ligands [230,[298][299][300][301][302][303]. Pimpl [287] gave the following decreasing sequence for soil/plant transfer:…”