Distribution coefficient for

Figure 4-23. Calculated and experimental selectivities and distribution coefficients for the type-I ternaries in the 2,2,4-trimethyl pentane-cyclohexane-furfural-benzene system.

By comparing the ratio of the distribution coefficients for a pair of ions, a separation factor (or relative retention) is obtained for a specific experimental condition. 

The principle of headspace sampling is introduced in this experiment using a mixture of methanol, chloroform, 1,2-dichloroethane, 1,1,1-trichloroethane, benzene, toluene, and p-xylene. Directions are given for evaluating the distribution coefficient for the partitioning of a volatile species between the liquid and vapor phase and for its quantitative analysis in the liquid phase. Both packed (OV-101) and capillary (5% phenyl silicone) columns were used. The GG is equipped with a flame ionization detector. 

In most cases, the activator impurity must be incorporated during crystal growth. An appropriate amount of impurity element is dissolved in the molten Ge and, as crystal growth proceeds, enters the crystal at a concentration that depends on the magnitude of the distribution coefficient. For volatile impurities, eg, Zn, Cd, and Hg, special precautions must be taken to maintain a constant impurity concentration in the melt. Growth occurs either in a sealed tube to prevent escape of the impurity vapor or in a flow system in which loss caused by vaporization from the melt is replenished from an upstream reservoir. 

Extraction from Aqueous Solutions Critical Fluid Technologies, Inc. has developed a continuous countercurrent extraction process based on a 0.5-oy 10-m column to extract residual organic solvents such as trichloroethylene, methylene chloride, benzene, and chloroform from industrial wastewater streams. Typical solvents include supercritical CO9 and near-critical propane. The economics of these processes are largely driven by the hydrophihcity of the product, which has a large influence on the distribution coefficient. For example, at 16°C, the partition coefficient between liquid CO9 and water is 0.4 for methanol, 1.8 for /i-butanol, and 31 for /i-heptanol. 

The selectivity of a gel, defined by the incremental increase in distribution coefficient for an incremental decrease in solute size, is related to the width of the pore size distribution of the gel. A narrow pore size distribution will typically have a separation range of one decade in solute size, which corresponds to roughly three decades in protein molecular mass (Hagel, 1988). However, the largest selectivity obtainable is the one where the solute of interest is either totally excluded (which is achieved when the solute size is of the same order as the pore size) or totally included (as for a very small solute) and the impurities differ more than a decade in size from the target solute. In this case, a gel of suitable pore size may be found and the separation carried out as a desalting step. This is very favorable from an operational point of view (see later). 

Kj = equilibrium distribution coefficient for component, i Kf = equilibrium distribution coefficient for component to which relative volatilities are referred... 

The distribution coefficient for n-heptane (solute i) distributed between ethylene glycol (solvent 1) and benzene (solvent 2) at 25°C is given as the ratio of mass fractions... 

The relatively large values of Vmax indicate, however, that the separation will be lengthy and the elution bands broad, particularly for the bromide band. The use of a more concentrated solution of eluant significantly reduces the values °f Vmax and the elution bands become much sharper. Thus the distribution coefficient for bromide using a 0.35M potassium nitrate solution is 6.5 and using the same column, Vmax = (6.5 x 4) + 4 = 30 mL. 

Burger and coworkers (5) in 1952 reported that some distribution coefficients for Pu022+ in organic-aqueous systems at lighted conditions were different from those observed for dark conditions, and those authors believed that some Pu022+ had been photochemically reduced. That reduction was confirmed by others (6) in 1965, and in 1969 a report suggested that most aqueous plutonium reactions were affected by light (7 ). 

Figure 7. Distribution Coefficient for Americium Extraction vs MgC12 Concentration in the NaCl-KCl-MgCl2 and NaCl-CaCI2 MgC12 Salt Systems.

It has been determined that there is a distribution coefficient for the impurities between crystal and melt which favors the melt. We can see how this arises when we reflect that impurities tend to cause formation of intrinsic defects within the crystal and lattice strain as a result of their presence. In the melt, no such restriction applies. Actually, each impurity has its own distribution coefficient. However, one can apply an average value to better approximate the behavior of the majority of impurities. 

Here, we show two cases for impurity segregation between melt and crystal as it grows in time. Note that an initial purification occurs in both cases but the distribution coefficient for the case on the right is such that the amount of impurity actually incorporated into the crystal, ki Cq. 

The effect of irradiation on the extractability of sulfoxides towards plutonium, uranium and some fission products were studied by Subramanian and coworkers . They studied mainly the effect of irradiation on dihexyl sulfoxide (DHSO) and found that irradiation did not change the distribution coefficient for Ru, Eu and Ce but increases the distribution coefficient for Zr and Pu. When comparing DHSO and tributyl phosphate (TBP), the usual solvent for the recovery and purification of plutonium and uranium from spent nuclear fuels, the effect of irradiation to deteriorate the extraction capability is much larger in TBP. Lan and coworkers studied diphenyl sulfoxides as protectors for the gamma radiolysis of TBP. It was found that diphenyl sulfoxide can accept energy from two different kinds of excited TBP and thus inhibits the decomposition of the latter. 

When the distribution coefficient for the desired solute from aqueous solutions into even the best of solvents is unfavourable it may become attractive to superimpose reaction. Consider the. separation of citric acid from aqueous solutions, for which physical extraction is unattractive. Here we can use a bulky tertiary amine, e.g. tri-2-ethylhexylamine, which has a very low solubility in water, and dissolve it in a suitable, water-insoluble solvent this will... 

These are more general, and they can perform log D calculation at any pH and ionic strength. The distribution coefficient for monoprotic base given by Eq. (2) can be simplified to Eq. (3) assuming that only the neutral form of a molecule will partition into the organic phase and thus D is zero. 

Tetko, I. V., Poda, G. I. Application of ALOGPS 2.1 to predict logD distribution coefficient for Pfizer proprietary compounds. J. Med. Chem. 2004, 47, 5601-5604. 

One of the first bed materials was based on the extractant diamyl amylphosphonate (DAAP marketed under the name U-TEVA-Spec ) and was designed for purification of the tetravalent actinides (U (IV), Th (IV), Pu (IV)) and hexavalent uranium (U(VI)). This material is characterized by high (>10-100) distribution coefficients for U and Th in significant (>3 M) concentrations of both nitric and hydrochloric acids, and so is useful for both U and Th purification (Horwitz et al. 1992 Goldstein et al. 1997 Eikenberg et al. 2001a). 

An additional material based on the extractant octyl-phenyl-N,N-diisobutyl-carbamoylmethylphosphine oxide, or CMPO, (marketed under the name TRU-Spec) has also been widely utilized for separations of transuranic actinides (Horwitz et al. 1993a) but is also useful for uranium-series separations (e.g., Burnett and Yeh 1995 Luo et al. 1997 Bourdon et al. 1999 Layne and Sims 2000). This material has even greater distribution coefficients for the uranium-series elements U (>1000), Th (>10000), and Pa. As shown in Figure 1, use of this material allows for sequential separations of Ra, Th, U, and Pa from a single aliquot on a single column. Separations of protactinium using this material (Bourdon et al. 1999) provide an alternative to liquid-liquid extractions documented in Pickett et al. (1994). 

To be absolutely correct the terms in., the brackets should be activities and not concentrations, also, two of the terms involve stationary phase activities that cannot be easily evaluated. The weight distribution coefficient for the analyte A" is designated as and is given by ... 

NRC. 1981. Distribution coefficients for radionuclides in aquatic environments. National Research Council, Washington DC National Academy Press. 

Another perspective provided by this model is the effect of three physiochemical parameters—solubility, distribution coefficient, and molecular mass—on transcoreal flux. All of these properties can be influenced by molecular design. The effects of these properties are illustrated in Fig. 13, in which the logarithm of the flux is plotted as a function of solubility and distribution coefficient for two different Mr. Several features of the model are depicted, and these qualitative, or semi-quantitative, aspects presumably encompass the principles of corneal permeation. 

Major problems are associated with using the linear distribution coefficient for describing adsorption-desorption reactions in groundwater systems. Some of these problems include the... 

By taking the ratio of the distribution coefficients for the two Components i and j, the separation factor can be defined, which is analogous to relative volatility in distillation ... 

Fig. 7.10. Correlation between in vivo Peff (determined with the Loc-I-Gut technique in humans) and octanol/buffer (pH 6.5) distribution coefficients for several common drugs. Drugs with octanol/buffer (pH 6.5) distribution coefficients >0 are highly permeable and well absorbed in humans (fa > 90%).

As the concentration of Na+, K+, Ca2+, Mg2+, Cl" ions in potable water usually have the value of 100 - 500 mg/1 and the concentration of radionuclides is very low, the sorbents must have high selectivity and distribution coefficient for Cs+, Sr2+, Co2+, I" ions. Moreover these sorbents must be very cheap because the filters cannot operate for a long time due to accumulation of radioactivity. Unfortunately most of known resins cannot be used in the filters for these purposes. 

Equilibrium data correlations can be extremely complex, especially when related to non-ideal multicomponent mixtures, and in order to handle such real life complex simulations, a commercial dynamic simulator with access to a physical property data-base often becomes essential. The approach in this text is based, however, on the basic concepts of ideal behaviour, as expressed by Henry s Law for gas absorption, the use of constant relative volatility values for distillation and constant distribution coefficients for solvent extraction. These have the advantage that they normally enable an explicit method of solution and avoid the more cumbersome iterative types of procedure, which would otherwise be required. Simulation examples in which more complex forms of equilibria are employed are STEAM and BUBBLE. 

The values of P and selectivity factors are calculated from the experimentally derived solute polarity distribution coefficient for the test solutes ethanol, dioxane, and nitromethane. The solute distribution... 

The distribution coefficient for a given extraction experiment is 98.0. If the concentration in the extracting solvent is 0.0127 M, what is the concentration in the original solvent ... 

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