Crystal structure and stability in aqueous solutions of Na0.5[NpO2(OH)1.5]∙0.5H2O and Na[NpO2(OH)2]

The ternary neptunium(V) (Np(V)) hydroxides Na0.5[NpO2(OH)1.5]·0.5H2O (I) and Na[NpO2(OH)2] (II) were synthesized in aqueous NaOH solutions at T = 80 °C, and their crystal structures were determined to be monoclinic, P21, Z = 2, a =5.9859(2), b = 10.1932(3), c = 12.1524(4) Å, β = 98.864(1)°, V = 732.63(4) Å3 for (I) and orthorhombic, P212121, Z = 4, a =5.856(7), b = 7.621(9), c = 8.174(9) Å, V = 364.8(7) Å3 for (II). By combining the detailed structural information with results from systematic solubility investigations, a comprehensive chemical and thermodynamic model of the Np(V) behavior in NaCl−NaOH solutions was evaluated. The results reveal a great stability of the ternary Na−Np(V)−OH solid phases that significantly enhances the predominance field of the entire Np(V) redox state to high alkalinity.

FELLHAUER David;  LEE Jun-Yeop;  DIBLASI Nicole A.;  WALTER Olaf;  GAONA Xavier;  SCHILD D.;  ALTMAIER M.; 

2022-09-19

AMER CHEMICAL SOC

JRC129461

0002-7863 (online),   

https://pubs.acs.org/doi/10.1021/jacs.2c03479,    https://publications.jrc.ec.europa.eu/repository/handle/JRC129461,   

10.1021/jacs.2c03479 (online),