Spectrophotometric and Calorimetric Studies of Np(V) Complexation with Sulfate at 10-70oC

Journal Article · Mon Jun 16 04:00:00 EDT 2008 · Journal of Thermal Analysis and Calorimetry

OSTI ID:961592

Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian; Friese, Judah I

Sulfate, one of the inorganic constituents in the groundwater of nuclear waste repository, could affect the migration of radioactive materials by forming complexes. Spectrophotometric and microcalorimetric titrations were performed to identify the Np(V)/sulfate complex and determine the equilibrium constants and enthalpy of complexation at 10-70 C. Results show that the complexation of Np(V) with sulfate is weak but slightly enhanced by the increase in temperature. The complexation is endothermic and becomes more endothermic with the increase in temperature. The enhanced complexation at elevated temperatures is due to the increasingly larger entropy of complexation that exceeds the increase in enthalpy, suggesting that the complexation of Np(V) with sulfate is entropy-driven.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Chemical Sciences Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 961592
• Report Number(s): LBNL-421E
• Journal Information: Journal of Thermal Analysis and Calorimetry, Journal Name: Journal of Thermal Analysis and Calorimetry; ISSN 1418-2874
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ENTHALPY
ENTROPY
RADIOACTIVE MATERIALS
RADIOACTIVE WASTES
SULFATES