Uranium isotherms

Sorption isotherms were also measured for sorption of selenium, technetium, tin, radium, uranium, neptunium, plutonium, and americium on the reference Mabton Interbed solids. The GR-1A groundwater composition was used in these experiments. Two temperatures (23°C 2°C and 60°C 1°C) were used, and both oxidizing and reducing conditions were used for each radionuclide. 

Figure 1. Cesium and Uranium Isotherms for Sorption on Sandstone at 23(o), 60(D), and 85°C(A). Oxidizing Conditions Were Used for Cesium and Reducing Conditions for Uranium.

Tin and americium were so extensively sorbed under all conditions that isotherm data could not be obtained. These elements are not significantly mobile in the Mabton Interbed aquifer. Values of Freundlich constants for technetium, radium, uranium, neptunium, and plutonium are given in Table IV. The Freundlich equation did not fit the selenium sorption data very well probably because of slow sorption kinetics or precipitation. Precipitation was also observed for technetium at 23°C for concentrations above 10 7M. This is about the same solubility observed for technetium in the sandstone isotherm measurements. Linear isotherms were observed only in the case of radium sorption. In general, sorption on the Mabton Interbed was greater than on the Rattlesnake Ridge sandstone. This is probably due to the greater clay content of the Mabton standard. 

Figure 3. Sorption and Desorption Isotherms for Uranium Sorption on Mabton Interbed Solids, (a) Oxidizing Conditions, (b) Reducing Conditions.

Figure 3. Pressure-composition isotherms for uranium-hydrogen system...

Pure hydrogen for the isotherm determinations, and also for hydriding the alloys used in the x-ray study, was obtained by the thermal decomposition of uranium hydride. Table I gives the composition of the hydrides used in this program, as obtained by vacuum-fusion analysis. 

The phase boundaries which are indicated by these isotherms represent slight shifts from those of the zirconium-hydrogen system, and show that no unexpected change results from small uranium additions. 

Hydrogen-Absorption Isotherms. The isotherms for the 25 weight % uranium alloy constitute a family of curves closely resembling each other. Seven of the 13 isotherms which were measured are plotted in Figure 3. Isotherms intermediate between each adjacent pair were omitted to reduce the complexity of the plot. The isotherms at 572° C. (not shown) and at 601° C. cross only two phase boundaries, because they are below the eutectic temperature. 

Figure 3. Hydrogen-absorption isotherms for zirconium-25 weight % uranium alloy...

FIG. 12 Effect of surface chemistry on the adsorption isotherms of uranium. (Adapted from Ref. 245.)... 

Figure 10.7 Adsorption isotherm describing the adsorption of uranyl (UO +) species onto suspended amorphous ferric hydroxide at pH 7.23 and 25°C. The vertical line denoting saturation with respect to schoepite [U02(0H)2 H2OI has been computed from the pH and dissolved uranyl concentration. The enrichment factor, E.F., equals K,. Reprinted from Geochim. et Cosmochim. Acta, Vol. 53(6), D. Langmuir, Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits, pp. 547-569,...

Gonzalez-Luque and Streat [45] determined the isotherms for the sorption and desorption of uranium from synthetic phosphoric acid solutions in the presence of interfering cations, such as Fe(II) and Ca(II), with these different impregnated resins and one commercial aminophosphinic acid ion-exchange resin. The effect of phosphoric concentration on uranium... 

The surface complex formation constants and the protolysis constants were optimized by using the experimentally obtained data sets and the computer code FITEQL (Herbelin and Westall, 1996). Surface site densities were evaluated from adsorption isotherms at pH 6.5 and a total uranium concentration of 1x10" M. The formation of ferrihydrite during the batch sorption experiment was identified by Mossbauer spec-... 

In an area where the crust is being uplifted, the fission-track dates of apatite increase with increasing elevations of the collecting sites and record the time that has elapsed since the samples cooled through the 60°C isotherm. All of the fission-track dates in the Transantarctic Mountains post-date the intrusion of the sills of Ferrar Dolerite which had already cooled before the apatites and other uranium-bearing minerals began to accumulate fission track. 

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