Bimodal normal distribution model for binding of trivalent europium by soil fulvic acid |
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| Authors: | H. S. Shin B. H. Lee H. B. Yang S. S. Yun H. Moon |
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| Affiliation: | (1) Department of Chemistry, Korea Advanced institute of Science and Technology, 373-1 Kusong-dong, Yusong-ku, 305-701 Taejon, (Korea);(2) Korea Atomic Energy Research Institute, P.O. Box 105, 353-606 Taejon, (Korea);(3) Department of Chemistry, Chungnam National University, 305-764 Taejon, (Korea) |
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| Abstract: | Complexation of trivalent europium by a well characterized soil fulvic acid was investigated by equilibrium dialysis titration method ([FA]=24 mg·dm–3, [Eu]t=9.0·10–7–3.5·10–6 mol·dm–3, pH 6.0). The concentrations of the fulvate bound and free europium were measured radiometrically using152Eu as a tracer. The experimental results were evaluated using a bimodal normal distribution model and a plot with two overlapping normal distributions was obtained which gave two means logK (µI=7.0,  I=1.1; µII=4.9, II=0.5) values for binding of europium by two classes of sites in fulvic acid. A multiligand model was assumed for fulvic acid, based upon the Eu(III) luminescence studies (7F0 5D0 excitation) on many organic acids as model ligands. |
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