caa a22 4500 378878425 CHVBK 20180305123426.0 cr unu---uuuuu 161128e20031201xx s 000 0 eng 10.1524/ract.91.12.751.23416 doi (NATIONALLICENCE)gruyter-10.1524/ract.91.12.751.23416 Thermodynamic model for the solubility of ThO2(am) in the aqueous Na+-H+-OH--NO3--H2O-EDTA system [Elektronische Daten] [Yuanxian Xia, Andrew R. Felmy, Linfeng Rao, Zheming Wang, Nancy J. Hess] The solubility of ThO2(am) in the aqueous Na+-H+-OH--NO3--H2O-EDTA system as a function of pCH⁺ (= -log[H+]) and variable NaNO3 (0.5M to 6.0M) has been determined. The experimental observations show that between pCH⁺ values 4.2 to 8.2, a stoichiometric 1:1 Th-EDTA complex forms that completely saturates the added chelate concentration. Th concentrations then decrease linearly with increasing pCH⁺ at pCH⁺>9.0. These changes in solubility are not predicted by currently available thermodynamic models. The ion-interaction model of Pitzer was used to interpret these solubility data. Thermodynamic analysis indicates that the speciation under basic conditions is dominated by monomeric mixed Th-OH-EDTA complexes. X-ray absorption near-edge spectroscopy confirmed the absence of the higher order ( e.g. dimeric) species. The equilibrium constants for the following reactions were determined from analysis of the solubility data: ThO2(am) + EDTA4- + 2H2O ↔ Th(OH)2EDTA2- + 2OH-, log K = -6.0; and ThO2(am) + EDTA4- + 2H2O ↔ Th(OH)3EDTA3- + OH-, log K∼-7.5. Pitzer ion-interaction parameters for the Th(OH)2EDTA2- and the Th(OH)3EDTA3- species were calculated. It was also determined that the solubility method for examining the complexation of tetravalent actinides with EDTA is limited to relatively high aqueous EDTA concentrations, relative to the amount of ThO2(am) precipitate, owing to the adsorption of the EDTA chelator by the solid phase. © 2003 Oldenbourg Wissenschaftsverlag GmbH Laboratory techniques, experiments nationallicence Analytical chemistry nationallicence Inorganic chemistry nationallicence Xia Yuanxian aut Felmy Andrew R. aut Rao Linfeng aut Wang Zheming aut Hess Nancy J. aut Radiochimica Acta/International journal for chemical aspects of nuclear science and technology Oldenbourg Wissenschaftsverlag GmbH 91/12/2003(2003-12-01), 751-760 0033-8230 91:12/2003<751 2003 91 ract https://doi.org/10.1524/ract.91.12.751.23416 text/html Onlinezugriff via DOI 1 research article jats NATIONALLICENCE 856 40 https://doi.org/10.1524/ract.91.12.751.23416 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Xia Yuanxian aut NATIONALLICENCE 700 1- Felmy Andrew R. aut NATIONALLICENCE 700 1- Rao Linfeng aut NATIONALLICENCE 700 1- Wang Zheming aut NATIONALLICENCE 700 1- Hess Nancy J. aut NATIONALLICENCE 773 0- Radiochimica Acta/International journal for chemical aspects of nuclear science and technology Oldenbourg Wissenschaftsverlag GmbH 91/12/2003(2003-12-01), 751-760 0033-8230 91:12/2003<751 2003 91 ract CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-gruyter