Uranyl sorption

Ivanovich M, Harmon RS (eds) Clarendon Press, Oxford, p 34-61 Giammar DE, Hering JG (2001) Time scales for sorption-desorption and surface precipitation of uranyl on goethite. Environ Sci Technol 35 3332-3337... 

Fowle et al. (2000) have measured the sorption by a soil bacterium (B. subtilis) of uranyl in 0.1 M NaC104 at 25°C as a function of pH, time, and solid solute ratio, using a batch technique. The stoichiometiy and thermodynamic stability of the important uranyl-surface complexes indicated that uranyl formed two different surface complexes, one involving neutral phosphate functional groups, and another with deprotonated carboxyl functional groups, on the bacterial cell wall ... 

UOt sorption from uranyl acetate at pH 5.4 Boehm and Brand after Stanton and Maatman (253) 145 62... 

This paper is devoted to the sorption of uranyl, which exhibits a complex aqueous and surface chemistry. We review briefly the sorption behaviour of An in the environment, and illustrate the variety of environmental processes using published data of uranyl sorption in the Ban-gombe natural reactor zone. After summarizing the general findings of the mechanisms of An sorption, we then focus particularly on the current knowledge of the mechanisms of uranyl sorption. A major area of research is the influence of the aqueous uranyl speciation on the uranyl surface species. Spectroscopic data of U(VI) sorbed onto silica and alumina minerals are examined and used to discuss the role of aqueous uranyl polynuclear species, U02(0H)2 colloids and uranyl-carbonate complexes. The influence of the mineral surface properties on the mechanisms of sorption is also discussed. 

Uranyl sorption processes in the Bangombe natural reactor zone... 

Fig. 2. Sorption edges and DLM fitting curves of (a) neptunyl on alumina gel, and (b) uranyl on quartz at different ionic strengths (I.S.) using experimental conditions and model parameters listed in Table 2. Uranyl data are from Mignot (2001).

Results and discussion. Uranyl colloids are formed in the blank and sorption samples at... 

Macroporous anion-exchange resin, useful for the sorption of uranyl nitrate, has been prepared by suspension polymerization of 4-methyl-2-vinylpyridine with trimethylene glycol dimethacrylate... 

Figure 3 Sorption and desorption edges for uranyl on goethite. Each sample contained 60m L goethite and 100p,gmL uranium. The sorption edge was measured 2 d after uranium addition desorption samples were contacted with the uranyl solution at pH 7 for 5 d, the pH was adjusted to cover the range of interest, and the samples were re-equilihrated for 2 d prior to sampling (see also Bryan and Siegel, 1998).

The dependence of a on the composition of the groundwater can also be described in terms of more fundamental thermodynamic parameters. This can be illustrated by considering the sorption of uranyl (UOl ) onto a generic surface site (>SOH) of a mineral... 

For simplicity, in this equation, we have assumed that activities are equal to concentrations and brackets refer to activities. C is a units conversion constant = Vy m relating void volume Vy (mL) in the porous media and the mass m (g) of the aquifer material in contact with the volume Vy, is the formation constant for an aqueous uranyl complex, and the superscripts i, j, k describe the stoichiometry of the complex. The form that the sorption binding constant takes is different for the different sorption models shown in Figure 4 (e.g., see Equation (5)). Leckie (1994) derives similar expressions for more complex systems in which anionic and cationic metal species form poly dentate surface complexes. Equation (7) can be derived from the following relationships for this system ... 

Figure 5 Calculated theoretical for sorption of uranyl onto a goethite substrate as a function of pH at fixed total carbon concentration in the presence of a sequestering agent (EDTA). are shown for several levels of calcium concentration. Surface area of the substrate is 100 L total carbon is fixed at 1.5 X 10 M and total uranium...

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