Raman spectroscopic characterization of a synthetic, non-stoichiometric Cu-Ba uranyl phosphate.

Crystals of phases belonging to the autunite group (general formula X(2+)(UO2)2(X(5+)O4)2·nH2O), specifically the uranyl phosphates (X(5+)=P) metauranocircite (X(2+)=Ba(2+)), metatorbernite (X(2+)=Cu(2+)) and a barian metatorbenite phase (X(2+)=Cu(2+)/Ba(2+)), have been synthesized in a silica gel medium and characterized by Raman spectroscopy. The Raman spectra showed bands in the range 750-1100 cm(-1), which were attributed to the ν1 and ν3 (PO(4))(3-) and (UO(2))(2+) stretching vibrations. By using the wavenumbers of the most intense and well defined ν1 (UO(2))(2+) vibration, the U-O bonds lengths were calculated for the three uranyl phosphate minerals.

In situ nanoscale observations of metatorbernite surfaces interacted with aqueous solutions.

Metatorbernite (Cu(UO(2))(2)(PO(4))(2)·8H(2)O) has been identified in contaminated sediments as a phase controlling the fate of U. Here, we applied atomic force microscopy (AFM) to observe in situ the interaction between metatorbernite cleavage surfaces and flowing aqueous solutions (residence time = 1 min) with different pHs. In contact with deionized water the features of (001) surfaces barely modify.

Interaction of calcium carbonates with lead in aqueous solutions.

Pure calcium carbonate (calcite and aragonite) solid materials of different particle size (100-200 microm fragments and millimeter-sized single crystals) were interacted with Pb in aqueous solutions at room temperature under atmospheric PCO2. In the case of the micrometer-sized samples, the macroscopic investigation using a batch-type treatment procedure (solutions between 10 and 1000 mg/L Pb) and ICP-AES, SEM-EDS, and powder-XRD showed that the metal is readily removed from the aqueous media by both materials and indicated the sorption processes (mainly surface precipitation leading to overgrowth of cerussite and hydrocerussite crystals) taking place in parallel with surface dissolution processes. The various processes occurring at the calcium carbonate solid-water interface were clearly distinguished and defined in the case of the millimeter-sized samples interacted with 1000 mg/L Pb using a combination of wet-chemical, in-situ (AFM) and ex-situ (AFM, SEM) microscopic, and surface spectroscopic (XPS, 12C-RBS) techniques.