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-Al2O3 colloids was studied. The kinetic desorption behavior of sorbed 152+154Eu(III) from humic acid-γ-Al2O3 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-Al2O3 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.