Sorption edge

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).

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).

As discussed previously (Section 9.06.3.1.1), plots of pH sorption edges (see Figure 3) are useful in summarizing the sorption of radionuclide by substrates that have amphoteric sites (i.e., SOH, SO , SOHJ). The pH sorption edges of actinides are similar for different aluminosilicates (quartz, a-alumina, clinoptUolite, montmorillo-nite, and kaolinite). For example, Np(V) and U(VI) exhibit similar pH-dependent sorption edges that are independent of specific aluminosilicate identity (Bertetti et al, 1998 Pabalan et al., 1998). Under similar solution conditions, the amount of radionuclide adsorbed is primarily a function of the surface area. This observation has led several workers to propose that the amount of actinide sorption onto natural materials can be predicted from the surface site density and surface area rather the specific molecular structure of the surface (Davis and Kent, 1990 Turner and Pabalan, 1999). 

Figure 2. Sorption edge of Fe on ferrihydrite, data from Liger et at. (1999), model with surface complexation constants estimated from linear free energy relation fLFERj and model optimized on the data of Liger et al.

Fig. 7-9. TLM solid solution model calibration and predictions for Co(ll) sorption to a-AUO, at low and high surface coverage (A) model calibration to high coverage data, t/f) Surface complexatiou and solid solution model predictions of representative pi I sorption edges. (O surface complexatiou and solid solution model predictions of a sorption isotherms at pi I / t>. and ) surface couiplexa-lion and solid solution. a sorption isotherm at pi 11> (alter Kal/ Hayes, 19 ISh).

Geochemical speciation combined with ion exchange Sorption edges and sorption isotherms MINTEQ Study of sorption of divalent metals in calcite [8]... 

Sorption and desorption edges for uranyl on goethite. Each sample contained 60 L goethite and uranium. The sorption edge was measured 2 d after uranium addition desorption samples were... 

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