Alteration, adsorption and nucleation processes on clay–water interfaces: Mechanisms for the retention of uranium by altered clay surfaces on the nanometer scale

Schindler, Michael; Legrand, Christine A.; Hochella, Michael F.

doi:10.1016/j.gca.2014.12.020

Cited by 34 publications

(16 citation statements)

References 85 publications

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“…These range from biomineralisation [17,18], to rock-forming silicates such as feldspars [11,19,20], natural and synthetic garnets (e.g., [21,22], or minerals of secondary origin such as phosphates and phyllosilicates [23][24][25][26]. Rare materials such as carbonado diamonds and meteorites have also been addressed (e.g., [27][28][29][30][31][32]).…”

Section: Research Topics Addressed By Integrated Fib-sem and Tem Micrmentioning

confidence: 99%

Focused Ion Beam and Advanced Electron Microscopy for Minerals: Insights and Outlook from Bismuth Sulphosalts

et al. 2016

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This paper comprises a review of the rapidly expanding application of nanoscale mineral characterization methodology to the study of ore deposits. Utilising bismuth sulphosalt minerals from a reaction front in a skarn assemblage as an example, we illustrate how a complex problem in ore petrology, can be approached at scales down to that of single atoms. We demonstrate the interpretive opportunities that can be realised by doing this for other minerals within their petrogenetic contexts. From an area defined as Au-rich within a sulphosalt-sulphide assemblage, and using samples prepared on a Focused Ion Beam-Scanning Electron Microscopy (SEM) platform, we identify mineral species and trace the evolution of their intergrowths down to the atomic scale. Our approach progresses from a petrographic and trace element study of a larger polished block, to high-resolution Transmission Electron Microscopy (TEM) and High Angle Annular Dark Field (HAADF) Scanning-TEM (STEM) studies. Lattice-scale heterogeneity imaged in HAADF STEM mode is expressed by changes in composition of unit cell slabs followed by nanoparticle formation and their growth into "veins". We report a progressive transition from sulphosalt species which host lattice-bound Au (neyite, lillianite homologues; Pb-Bi-sulphosalts), to those that cannot accept Au (aikinite). This transition acts as a crystal structural barrier for Au. Fine particles of native gold track this progression over the scale of several hundred microns, leading to Au enrichment at the reaction front defined by an increase in the Cu gradient (several wt %), and abrupt changes in sulphosalt speciation from Pb-Bi-sulphosalts to aikinite. Atom-scale resolution imaging in HAADF STEM mode allows for the direct visualisation of the three component slabs in the neyite crystal structure, one of the largest and complex sulphosalts of boxwork-type. We show for the first time the presence of aikinite nanoparticles a few nanometres in size, occurring on distinct (111) PbS slabs in the neyite. This directly explains the non-stoichiometry of this phase, particularly with respect to Cu. Such non-stoichiometry is discussed elsewhere as defining distinct mineral species. The interplay between modular crystal structures and trace element behaviour, as discussed here for Au and Cu, has applications for other mineral systems. These include the incorporation and release of critical metals in sulphides, heavy elements (U, Pb, W) in iron oxides, the distribution of rare earth elements (REE), Y, and chalcophile elements (Mo, As) in calcic garnets, and the identification of nanometre-sized particles containing daughter products of radioactive decay in ores, concentrates, and tailings.

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Section: Research Topics Addressed By Integrated Fib-sem and Tem Micrmentioning

confidence: 99%

Focused Ion Beam and Advanced Electron Microscopy for Minerals: Insights and Outlook from Bismuth Sulphosalts

et al. 2016

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“…Previous works reported that the adsorption of UO 2 2+ on smectite follows two main mechanisms: ion-exchange through outer-sphere complexation at low pH and low ionic strength, whereas at near-neutral pH and high ionic strength through inner-sphere complexation on the edge sites controls the sorption mechanism [14,18,26,29,31,33,34].…”

Section: Introductionmentioning

confidence: 99%

Influence of pH, layer charge location and crystal thickness distribution on U(VI) sorption onto heterogeneous dioctahedral smectite

Guimarães

Rodríguez‐Castellón

Algarra

et al. 2016

Journal of Hazardous Materials

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“…This effect has been experimentally examined in great detail with respect to the types of sorption complexes, changes in pH and the ionic strength of the electrolyte solution, and concentrations of U [22][23][24][25][26][27][28][29][30]. Dong et al [28] studied the sorption of uranyl species onto kaolinite and goethite, two of the most dominant minerals in sandstonehosted uranium deposits, and showed that kaolinite was a stronger sorbent than goethite at pH < 4.…”

Section: Introductionmentioning

confidence: 99%

Origin and Role of Kaolinization in Roll-Front Uranium Deposits and Its Response to Ore-Forming Fluids in the Yili Basin, China

et al. 2018

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Kaolinite is a common mineral found in most Chinese sandstone-hosted uranium deposits. It occurs particularly in coal-bearing clastic rocks in northwest China, such as the uranium deposits in the Yili Basin, which is well known for hosting several largescale roll-front uranium deposits. Previous studies have provided limited information on the origin of kaolinization and its role in the uranium mineralization. This study uses gas hydrocarbon, fluid inclusions, O and H isotope analysis, and scanning electron microscopy observations to investigate the formation of kaolinite in ore-hosting rocks from the Mengqiguer uranium deposit in the southern margin of the Yili Basin and to determine its role in the uranium mineralization. Results suggest that kaolinization is intense in the coal-and ore-bearing clastic rocks and that it is related to leaching of feldspar by acidic fluids. Vermicular kaolinite was formed by hydrocarbon-bearing fluid generated from coal and carbonaceous mudstone during a shallow-burial diagenetic stage at low homogenization temperatures ranging from 69 to 78 ∘ C and at relatively high salinities of 7.6−11.0 wt% NaCl eq . Consequently, silicate minerals (such as feldspar) were leached and created secondary pores that hosted the subsequently formed uranium minerals. In contrast, micritic kaolinite was formed by infiltration of meteoric fluid enriched in U and O 2 at low homogenization temperatures of 51−63 ∘ C and low salinities of 1.2−3.7 wt% NaCl eq . U 6+ was sorbed by the micritic kaolinite through cation exchange, forming a U-bearing kaolinite complex; it was also reduced by pyrite and carbon detrital, thereby precipitating at the acidic oxidation front. The results of this study confirm that intense kaolinization is closely related to uranium mineralization in coal-bearing clastic rocks.

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Alteration, adsorption and nucleation processes on clay–water interfaces: Mechanisms for the retention of uranium by altered clay surfaces on the nanometer scale

Cited by 34 publications

References 85 publications

Focused Ion Beam and Advanced Electron Microscopy for Minerals: Insights and Outlook from Bismuth Sulphosalts

Focused Ion Beam and Advanced Electron Microscopy for Minerals: Insights and Outlook from Bismuth Sulphosalts

Influence of pH, layer charge location and crystal thickness distribution on U(VI) sorption onto heterogeneous dioctahedral smectite

Origin and Role of Kaolinization in Roll-Front Uranium Deposits and Its Response to Ore-Forming Fluids in the Yili Basin, China

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