Thermodynamics of neptunium(V) complexation with sulfate in aqueous solution
| Autor: | David Fellhauer, Thomas Sittel, Petra J. Panak, Andrej Skerencak-Frech, Martin M. Maiwald |
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| Rok vydání: | 2018 |
| Předmět: |
Exothermic reaction
Aqueous solution Absorption spectroscopy 010405 organic chemistry Chemistry Enthalpy Analytical chemistry Thermodynamics Atmospheric temperature range 010402 general chemistry Mole fraction 01 natural sciences Atomic and Molecular Physics and Optics 0104 chemical sciences Specific ion interaction theory Ionic strength General Materials Science Physical and Theoretical Chemistry |
| Zdroj: | The Journal of Chemical Thermodynamics. 116:309-315 |
| ISSN: | 0021-9614 |
| Popis: | The complexation of NpO 2 + with sulfate is studied in aqueous solution using absorption spectroscopy. The total ligand concentration (Na 2 SO 4 ), ionic strength (NaClO 4 ), and temperature (T = 20–85 °C) is varied, yielding detailed information on the thermodynamics of the complexation reaction. A single complex species (NpO 2 (SO 4 ) − ) is identified by peak deconvolution of the absorption spectra. The molar fraction of the complex species increases with increasing temperature. The conditional stability constants log β′ 1 (T) are calculated and extrapolated to zero ionic strength for each temperature condition with the specific ion interaction theory (SIT). The determined log β 0 1 (T) values increase by approximately one logarithmic unit in the studied temperature range. Furthermore, the log β 0 1 (T) values are linearly correlated with the reciprocal temperature. Thus, fitting the data according to the integrated Van’t Hoff equation yields the standard reaction enthalpy (Δ r H 0 m ) and entropy (Δ r S 0 m ) of the formation of the NpO 2 (SO 4 ) − complex. The results show an endothermic reaction which is solely driven by the reaction entropy. In addition, the binary SIT ion-ion interaction coefficient e(Na + , NpO 2 (SO 4 ) − ) of the complex species is determined. |
| Databáze: | OpenAIRE |
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