Earth sciences waste disposal investigations, January--June 1966

Eliason, J.R.

doi:10.2172/4005110

Cited by 5 publications

(5 citation statements)

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“…The rate of formation of > SiOH groups on the surface of quartz is extremely slow at normal temperatures and in neutral media. Consequently, the number of -OH groups on the surface of quartz tion a sharp increase in selectivity was observed, indicating a small number of sites highly specific for Cs + [19]). The selectivity of kaolinite above 1 % loading (Ä^a = 32 ± 3) , is similar to values reported in the literature [7,20].…”

Section: Fig 2 Sorption Ratio R §(Cs)mentioning

confidence: 99%

Chemistry of Radioactive Cesium in the Hydrosphere and in the Geosphere

Lieser

Steinkopff

1989

Radiochimica Acta

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Cesium /Sorption of Cesium/Colloids/Clay minerals /Ion exchange SummaryCesium is sorbed with relatively high selectivity by clay minerals. Accordingly, in groundwaters Cs is found in high amounts in suspended matter or in colloids, if these consist of or contain clay minerals. The sorption of Cs in sediments is also mainly determined by the presence of clay minerals and the sorption ratio at low salinity is found to be roughly proportional to the clay content in the sediments. Furthermore, with the same sediment the sorption ratio is inversily proportional to the concentration of NaCl which proves that ion exchange on the clay minerals is the prevailing sorption mechanism for Cs.It is shown that the sediments contain small amounts of sorption sites of high selectivity for Cs + which govern the sorption behaviour at very small concentrations of Cs + ions. These sorption sites are also responsible for Cs + sorption on suspended particulates of clay in the groundwaters.

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Section: Fig 2 Sorption Ratio R §(Cs)mentioning

confidence: 99%

Chemistry of Radioactive Cesium in the Hydrosphere and in the Geosphere

Lieser

Steinkopff

1989

Radiochimica Acta

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“…Molecular theories that treat ion binding to clay minerals and that account for groundwater and clay composition could assist in predicting the transport properties of radioactive ions in the environment. The binding strengths of cesium to a variety of clay minerals have been determined experimentally. − Without exception, cesium has been found to bind to clays most selectively among the alkali-metal cations. Cesium binding strengths are also known to increase with clay layer charge 10 and to depend significantly upon layer-charge location. , Existing theories of ion binding, reviewed recently, , are based either on simple electrostatic descriptions of ion−water and ion−clay interactions or upon empirical hard and soft, acid and base concepts.…”

Section: Introductionmentioning

confidence: 99%

Molecular Computer Simulations of the Swelling Properties and Interlayer Structure of Cesium Montmorillonite

1998

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The crystalline swelling properties and interlayer structure of a cesium montmorillonite clay were investigated using molecular computer simulations. Two classes of dry-clay structures, proposed previously to explain X-ray diffraction and NMR experiments, were identified using Monte Carlo annealing calculations. Hydrated clays with water contents ranging from 0.044 to 0.440 gH 2 O/gclay were investigated using molecular dynamics simulations. Layer spacings calculated as a function of water content were found to be similar to experimental swelling curves, showing a distinct plateau at the monolayer-hydrate spacing. Hydration energies were calculated as a function of water content and expressed in three complementary forms. The immersion energy form was found to be most useful, revealing an apparently global minimum in the swelling-coordinate energy that corresponds to the monolayer hydrate. This is in agreement with experimental measurements and may help clarify the energetic origins of discrete, crystalline swelling processes in clay minerals. For two- and four-layer hydrates, cesium ions readily formed two different types of inner-sphere complexes with the clay surface. Ions associated with negatively charged tetrahedral substitution sites formed exclusively inner-sphere complexes and occupied hexagonal cavities adjacent to the substitutions. Other cesium ions occupied both inner-sphere and outer-sphere configurations with roughly equal probability. The ease with which cesium associates with the clay surface may be responsible for the formation of monolayer hydrates in cesium-substituted clays and for selective binding of cesium to many clay minerals.

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“…For T greater than 800 °C, these particles may emit positive ions. The montmorillonite clay used in this study has the formula (Al3.i4Feo.i52Mgo.6o)(SÍ8)-C>2o(OH)4(Nao.i8Cao.2i) (17), in which the first parentheses represent octahedrally coordinated ions; the second, tetrahedrally coordinated ions; and the last, exchangeable cations. Among these constituents, the most probable positive ion emitted at high temperature would be Na+ due to its relatively low positive ion work function (about 3.8 eV for pure Na metal, which may be lower with the presence of impurities).…”

Section: Resultsmentioning

confidence: 99%