Using of chelating resin to study the kinetic desorption of Eu(III) from humic acid-Al₂O₃ colloid surfaces

The association of organic-inorganic colloid-borne trace elements was investigated. Radionuclide ^152+154Eu(III) was chosen as a representative and chemical homologue for trivalent lanthanide and actinide ions present in radioactive nuclear waste. Effect of pH and contact time of organic-inorganic/Eu(III) on the kinetic dissociation of Eu(III) from HA-Al ₂O₃ colloids was studied. The kinetic desorption behavior of sorbed ^152+154Eu(III) from humic acid-γ-Al₂O ₃ colloids was studied at pH values of 4.5 ± 0.2, 5.3 ± 0.2 and 6.5 ± 0.2, respectively, by the addition of the chelating resin. The experimental results suggest that the fractions of irreversible sorption of radionuclide ^152+154Eu(III) to HA-Al ₂O₃ colloids increase with increasing pH values, and are independent of aging time. At least two different species, "weak" and "strong" dissociation fractions, are required to simulate the kinetic desorption of ^152+154Eu(III) from HA-Al₂O₃ colloids. The species of Eu(III) sorbed on HA-Al₂O₃ colloids move from "weak" sites to "strong" sites with increasing aging time, whereas the fractions of irreversible sorption are independent of aging time. The results are important for the evaluation of radionuclides' behavior in the environment.