Extractants phase diagrams

There are many types of phase diagrams in addition to the two cases presented here these are summarized in detail by Zief and Wilcox (op. cit., p. 21). Solid-liquid phase equilibria must be determined experimentally for most binaiy and multicomponent systems. Predictive methods are based mostly on ideal phase behavior and have limited accuracy near eutectics. A predic tive technique based on extracting liquid-phase activity coefficients from vapor-liquid equilib-... 

FIG. 22-85 Phase diagram for a PEG/Dextran, hiphasic, aqueous-polymer system used in liquid-liquid extraction operations for protein separations. Alheiisson, Partition of Cell Particles and Macromolecules, 3d ed., Copyright 1986. Reprintedhy petTTUssion of John Wiley Sons, Inc.)... 

Present production processes use two stage counter-current extraction to remove americium from molten plutonium with magnesium chloride based salts. Both 35 mole % NaCl - 35 mole % KC1 - 3D mole % MgCl2 and 50 mole % NaCl-26 mole % CaCl2 - 24 mole % Mg Cl 2 are used for americium extraction. Figures 4 and 5 show the ternary phase diagrams for these salt systemsU0). 

Sodium-zinc alloys for phase diagram determination are prepared by melting the elements in glass tubes under H2- Samples of NaZujj are prepared by heating zinc for several hours above the melting point of NaZn,3 (557°C) with xs Na in alundum extraction thimbles with N2 or Ar in a steel bomb scaled with copper gaskets. Excess Na was removed by extraction with liq NHj. Both KZn,3 and KCd,2 were prepared in this manner. ... 

Figure 4 Phase diagrams of pectins extracted by water from extruded citrus fibre and by acid from the fibres (upper curve), and of commercial citrus pectins (dm 73%) (lower curve)...

Fig. 5 Mean-field phase diagrams for asymmetric ABA triblocks spanning between diblock (r = 0.0) and symmetric triblock (r = 0.5) limits at segregations of a xN = 20, b /N = 30 and c xN = 40 calculated with SCFT. Dotted curves critical asymmetries rc predicted by SST beyond which short A blocks are extracted from their domains. From [32]. Copyright 2000 American Institute of Physics...

Brady et al. [52] have discussed pressure-temperature phase diagrams for carbon dioxide polychlorobiphenyls and examined the rate process of desorption from soils. Supercritical carbon dioxide was used to extract polychlorobiphenyls and DDT and Toxaphene from contaminated soils. 

As a conclusion to these notes on the assessment and compilation of intermetallic data, we mention a few examples of papers in which criteria to be followed in order to extract from literature data the best version of a phase diagram have been discussed. These are Morral and Gupta (1991) (a figure of merit for predicted phase diagram), Okamoto and Massalski (1991, 1993) (thermodynamically improbable phase diagrams and guidelines for binary phase diagram assessment). See also various comments in several chapters in Cahn (2001). 

This chapter s statistical mechanics method was used to generate phase diagrams as illustrations of multicomponent hydrate equilibria concepts at one isotherm, 277.6 K, the most common temperature in a pipeline on the ocean floor at water depths beyond 600 m. Section 5.2.1 shows the fit if the method to single (simple) hydrates, before the extension to binary hydrate guests in Section 5.2.2. Section 5.2.3 shows the final extension to ternary mixtures of CH4 + C2H6 + C3H8 and indicates an industrial application. Most of the discussion in this section was extracted from the thesis of Ballard (2002) and the paper by Ballard and Sloan (2001). 

Another method for obtaining the extension domain of the organic extractant phase before third-phase formation is to prepare a solution under the conditions of formation of a third phase, and allow it to equilibrate. Chemical analysis of the third phase and the dilute organic phase in equilibrium with the aqueous phase identifies tie-lines in the phase diagrams (Figure 7.5) (a tie-line joins the composition of the two phases (dilute and concentrated) in equilibrium after the splitting of the organic phase into two phases). 

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