Solubility of triuranyl diphosphate tetrahydrate (TDT) and Na autunite at 23 and 50 °C

Journal Article
ract, vol. 98, iss. 9-11, pp. 549-554, 2010
Authors
Christopher R. Armstrong, Andrew R. Felmy, Sue B. Clark
Abstract
Abstract In this report we present experimental solubility data for well-characterized triuranyl diphosphate tetrahydrate (TDT: (UO2)3(PO4)2·4H2O) and Na autunite (Na[UO2PO4x H2O) at 23 and 50 °C in NaClO4-HClO4 solutions at pCH+ =2. Duplicate samples of TDT in 0.1, 0.5, 1.0, 2.0 and 5.0 m solutions were equilibrated at 23 and 50 °C. TDT solid was synthesized and characterized with ICP-OES, ATR-IR and powder XRD before and after solubility experiments. The pH of the suspensions were monitored throughout the experiments. Equilibrium was achieved from undersaturation with respect to TDT and oversaturation for Na autunite. Steady-state conditions were achieved in all cases within 82 d. TDT was unstable at ionic strengths above 0.1 m, where its complete conversion to Na autunite was observed. The ion-interaction model was used to interpret the experimental solubility data. The solubility product, logߙK sp, for TDT was determined to be −49.7 and −51.3 at 23 and 50 °C respectively. logߙK sp for Na autunite was determined to be −24.4 (23 °C) and −24.1±0.2 (50 °C).
English