TY - JOUR
T1 - Thermodynamic study on the U(VI) complexation with dicarboxylates by calorimetry
AU - Kirishima, A.
AU - Onishi, Y.
AU - Sato, N.
AU - Tochiyama, O.
N1 - Funding Information:
Acknowledgment. This study has been partially supported by the Grant-in-Aid for Scientific Research (A) of Japan Society for the Promotion of Science (JSPS) and the Grant-in-Aid for Young Scientists (B) of The Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT).
PY - 2008
Y1 - 2008
N2 - The thermodynamic quantities (ΔG, ΔH and ΔS) of U(VI) complexation with oxalate, malonate, succinate, glutarate, adipate, phthalate, tartronate and malate, and of Eu(III) complexation with succinate, glutarate and adipate were determined by potentiometric and calorimetric titration techniques. The obtained thermodynamic quantities indicated that these complexation reactions are mainly driven by the entropy changes while the enthalpy changes are nearly zero or preventing the complexation. The thermodynamic quantities of 1:1 U(VI) complexes with 5 dicarboxylates having different carbon chain lengths (-OOC-(CH2) n-COO-) showed an interesting tendency, that is, -ΔH decreased and T ΔS increased systematically with increasing the length of the carbon chain from n = 2 to 6. The comparison of T ΔS values of 1:1 carboxylate formation with U(VI) and Eu(III) showed that T ΔS of U(VI) were always lager than those of Eu(III). The entropies of 1:1 complex formation of U(VI) with hydroxycarboxylates were always smaller than those with carboxylates of the same carbon chain length, while the enthalpies of uranyl hydroxycarboxylates were always larger. This tendency was also observed in the protonation and the complex formation of Eu(III).
AB - The thermodynamic quantities (ΔG, ΔH and ΔS) of U(VI) complexation with oxalate, malonate, succinate, glutarate, adipate, phthalate, tartronate and malate, and of Eu(III) complexation with succinate, glutarate and adipate were determined by potentiometric and calorimetric titration techniques. The obtained thermodynamic quantities indicated that these complexation reactions are mainly driven by the entropy changes while the enthalpy changes are nearly zero or preventing the complexation. The thermodynamic quantities of 1:1 U(VI) complexes with 5 dicarboxylates having different carbon chain lengths (-OOC-(CH2) n-COO-) showed an interesting tendency, that is, -ΔH decreased and T ΔS increased systematically with increasing the length of the carbon chain from n = 2 to 6. The comparison of T ΔS values of 1:1 carboxylate formation with U(VI) and Eu(III) showed that T ΔS of U(VI) were always lager than those of Eu(III). The entropies of 1:1 complex formation of U(VI) with hydroxycarboxylates were always smaller than those with carboxylates of the same carbon chain length, while the enthalpies of uranyl hydroxycarboxylates were always larger. This tendency was also observed in the protonation and the complex formation of Eu(III).
KW - Carboxylic acid
KW - Enthalpy
KW - Entropy
KW - Europium(III) complex
KW - Stability constant
KW - Uranium(VI) complex
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U2 - 10.1524/ract.2008.1540
DO - 10.1524/ract.2008.1540
M3 - Article
AN - SCOPUS:56649094301
SN - 0033-8230
VL - 96
SP - 581
EP - 589
JO - Radiochimica Acta
JF - Radiochimica Acta
IS - 9-11
ER -