CHARACTERIZATION AND DISSOLUTION BEHAVIOR OF A BECQUERELITE FROM SHINKOLOBWE, ZAIRE

The solubility of becquerelite (Ca(UO2)(6)O-4(OH)(6).8H(2)O) from Shin kolobwe (Zaire) has been determined at 25 degrees C as a function of p H under a nitrogen atmosphere. Leached and unleached samples were char acterized by a variety of analytical methods that include optical micr oscopy, x-ray powder diffraction (XRD), electron microprobe analysis ( EMPA), and conventional scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopic analysis (EDS). A least-squares minimi zation of the measured total aqueous uranium concentration in equilibr ium with natural becquerelite using the NEA uranium database (Grenthe et al., 1992) gives a solubility constant of log K-s0(0) = 29 +/- 1, s ignificantly lower than values reported for synthetic becquerelite: lo g K-s0 = 43.2 (Vochten and Van Haverbeke, 1990). Copyright (C) 1997 El sevier Science Ltd.