Thermodynamic properties of gluconic acid (HGH(4)(aq)) complexation with Nd(III) have been studied in acidic solutions at 25 degrees C and 1.0M NaClO4 by potentiometry, spectrophotometry and calorimetry. Three Nd(III)/gluconate complexes were identified in solutions of pC(H) 2.5-4.5. The formation constants and the complexation enthalpies are: log beta(1) =2.55 +/- 0.05 and Delta H-1 degrees = -(8.22 +/- 0.23) kJ mol(-1) for Nd(GH(4))(2+), log beta(2)=4.45 +/- 0.05and Delta H-2 degrees = -(15.3 +/- 0.4) kJ mol(-1) for Nd(GH(4))(2)(+), and log beta(3) = 5.60 +/- 0.15 and Delta H-3 degrees = -(24.6 +/- 0.6) kJ mol(-1) for Nd(GH(4))(3)(aq). The thermodynamic parameters indicate that gluconic acid, like other alpha-hydroxycarboxylic acids, forms stronger complexes with Nd(III) than simple monocarboxylic acids, likely by the participation of the alpha-hydroxyl group during complexation. The same type of binding appears to occur with Ca2+ and NpO2+ as the 1:1 stability constants are linearly correlated with the effective cationic charges of the metal cations
Complexation of gluconic acid with Nd(III) in acidic solutions: A thermodynamic study.
ZANONATO, PIER LUIGI;
2007
Abstract
Thermodynamic properties of gluconic acid (HGH(4)(aq)) complexation with Nd(III) have been studied in acidic solutions at 25 degrees C and 1.0M NaClO4 by potentiometry, spectrophotometry and calorimetry. Three Nd(III)/gluconate complexes were identified in solutions of pC(H) 2.5-4.5. The formation constants and the complexation enthalpies are: log beta(1) =2.55 +/- 0.05 and Delta H-1 degrees = -(8.22 +/- 0.23) kJ mol(-1) for Nd(GH(4))(2+), log beta(2)=4.45 +/- 0.05and Delta H-2 degrees = -(15.3 +/- 0.4) kJ mol(-1) for Nd(GH(4))(2)(+), and log beta(3) = 5.60 +/- 0.15 and Delta H-3 degrees = -(24.6 +/- 0.6) kJ mol(-1) for Nd(GH(4))(3)(aq). The thermodynamic parameters indicate that gluconic acid, like other alpha-hydroxycarboxylic acids, forms stronger complexes with Nd(III) than simple monocarboxylic acids, likely by the participation of the alpha-hydroxyl group during complexation. The same type of binding appears to occur with Ca2+ and NpO2+ as the 1:1 stability constants are linearly correlated with the effective cationic charges of the metal cationsPubblicazioni consigliate
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