PubMed · 13732306
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R C PALMER, D K DAVIS, W V WILLIS. 1961. A remote sampling system for high-level gamma sources.. https://doi.org/10.1016/0020-708x(61)90109-0
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A physiologically descriptive model of the biological behavior of cesium in the human body has been constructed around a detailed blood flow model. The rate of transfer from plasma into a tissue is determined by the blood perfusion rate and the tissue-specific extraction fraction of Cs during passage from arterial to venous plasma. Information on tissue-specific extraction of Cs is supplemented with information on the Cs analogues, K and Rb, and known patterns of discrimination between these metals by tissues. The rate of return from a tissue to plasma is estimated from the relative contents of Cs in plasma and the tissue at equilibrium as estimated from environmental studies. Transfers of Cs other than exchange between plasma and tissues (e.g. secretions into the gastrointestinal tract) are based on a combination of physiological considerations and empirical data on Cs or related elements. Model predictions are consistent with the sizable database on the time-dependent distribution and retention of radiocesium in the human body.
In this study, a series of saturated column experiments were conducted to investigate effects of colloids on Cs transport in two types of porous media (Hanford sediment characteristic of 2:1 clay minerals and silica Ottawa sand). The colloids used were obtained by reacting Hanford sediment with simulated tank waste solutions. Because of the highly nonlinear nature of Cs sorption found in batch experiments, we used two different concentrations of Cs (7.5 x 10(-5) M and 1.4 x 10(-8) M) for the transport experiments. The presence of colloids facilitated the transport of Cs through both Hanford sediment and Ottawa sand via association of Cs with mobile colloidal particles. Due to the nonlinearity of the Cs sorption, the colloid-facilitated Cs transportwas more pronounced atthe low Cs concentration (1.4 x 10(-8) M) than at the high concentration (7.5 x 10(-5) M) when expressed relative to the inflow Cs concentration. In the absence of colloids, no Cs moved through the 10-cm long columns during the experiment within about 20 pore volumes, exceptfor the high Cs concentration in the Ottawa sand where a complete Cs breakthrough was obtained. Also, it was found that colloid-associated Cs could be partially stripped off from colloids during the transport. The stripping effect was controlled by both Cs concentration and sorption capacity of the transport matrix.
We report here the synthesis and characterization of two new classes of chelating fibers, namely, (1) polymercaptopropylsilsesquioxane (PMPS) and (2) copper(II) ferrocyanide complexed with poly[1-(2-aminoethyl)-3-aminopropyl]silsesquioxane (Cu-FC-PAEAPS) fibers. These fibers were evaluated for selective removal of trace amount of mercury and cesium ions respectively in the presence of competing metal ions from water. The PMPS and Cu-FC-PAEAPS fibers were prepared by coating their corresponding soluble prepolymers, which are derived from mercaptopropyltrimethoxysilane and [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane monomers, respectively, on a glass fiber substrate, followed by a cross-linking step at 120 degrees C. The fibers were characterized through infrared spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). These novel materials are extremely efficient in removing low concentrations of mercury and cesium ions from water in the presence of high concentrations of sodium or potassium ions. They were shown to remove trace mercury and cesium contaminants effectively to well below parts per billion concentrations under a variety of conditions.