Portioning distribution ratio

ILs-separation processes have also been appHed for actinides in aqueous solution by the incorporation of -octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide as the extractant. The portioning distribution ratios for Pu, Th and... 

Extraction Between Two Phases When the sample is initially present in one of the phases, the separation is known as an extraction. In a simple extraction the sample is extracted one or more times with portions of the second phase. Simple extractions are particularly useful for separations in which only one component has a favorable distribution ratio. Several important separation techniques are based on simple extractions, including liquid-liquid, liquid-solid, solid-liquid, and gas-solid extractions. 

What must a solute s distribution ratio be if 99% of the solut in a 50.0-mF sample is to be extracted with a single 50.0-mF portion of an organic solvent Repeat for the case where two 25.0-mF portions of the organic solvent are used. 

Impurities present in the organic phase may sometimes be removed by backwashing. The organic extract when shaken with one or more small portions of a fresh aqueous phase containing the optimum reagent concentration and of correct pH will result in the redistribution of the impurities in favour of the aqueous phase, since their distribution ratios are low most of the desired element will remain in the organic layer. 

Distribution Ratio (DR) The DR relates the concentration of an amine present in the steam phase to that concentration in the condensate phase (vapor-liquid distribution ratio). Consequently, it identifies in which condensate production region of a steam-condensate system any particular amine will concentrate and thus provide protection against corrosion. It also helps to indicates the portion of amine loss due to vaporization in a condenser or venting of a deaerator. The expression for DR is shown here ... 

The results of two investigations from two diverse locations provided evidence that this distribution ratio might be due to reversible sorption-desorption reactions. Scientists at Argonne National Laboratory (ANL) equilibrated filtered Lake Michigan water with sediments that had been contaminated with Pu ten years earlier. As many as nine extractions on the same portions of sediment produced essentially identical values(15). Noshkin has observed that the concentrations of plutonium in the waters of Enewetak remain relatively constant although there is a continual replacement of water at an estimated residence time of 144 days (16). The concentration corresponds well with that predicted from the experimental distribution ratio between lagoon sediment and water. 

In general, with a sufficiently large equilibrium constant (distribution ratio) and a rapid rate of attainment of equilibrium, quantitative transfer from one phase to another can be made in a single stage. For such highly favorable systems, batch liquid-liquid extractions can be used in which one phase is equilibrated with several successive fresh portions of a second phase. Such batch separations are most effective when one component remains quantitatively in one phase while another distributes itself between the two phases. 

As the number of extractions approaches infinity, the volume of organic phase for each extraction approaches zero. In practice, little is gained by dividing the volume of extractant into more than four or five portions, because is approached asymptotically. Equation (23-11) is useful in determining whether a given extraction is practicable, using a reasonable value of V JV, or whether an extractant with a more favorable distribution ratio should be sought. 

The ratio of the amount extracted to the amount remaining is called the distribution ratio. There are many situations in which the distribution ratio is low, which would require large amounts of solvent if separatory funnels were used exclusively. This can be very expensive in both chemical and labor costs, and the additional cost of solvent disposal is now often prohibitive. Continuous extractors, in which a small volume of solvent is used to extract a portion of the compound, then evaporated, condensed, and used again, are an ideal solution. This process can be repeated for days if necessary and at the end, there is only a small volume of solvent to remove and dispose of Continuous extractors that involve solvents both heavier and lighter than water are discussed in Chapter 10. A widely used apparatus for continuously extracting components from solids is the batch extractor developed by Soxhiet. The sample is placed in a porous paper thimble and then placed in a horizontal tube with a closed bottom. The extraction solvent is dripped onto the top of the solid, percolates through it, and siphons off after a short time, the process is repeated as often as necessary. Soxhiet extraction is covered in Chapter 10. 

Ninety-six percent of a solute is removed from 100 mL of an aqueous solution by extraction with two 50-mL portions of an organic solvent. What is the distribution ratio of the solute ... 

For a solute with a distribution ratio of 25.0, show by calculation which is more effective, extraction of 10 mL of an aqueous solution with 10 mL organic solvent or extraction with two separate 5.0-mL portions of organic solvent. 

For residues in whole commodities, including the edible portion, there is no universal distribution ratio because the amount of residue in the edible portion varies from pe.stjcidc... 

In these extractants, HNO3 interaction with the extractant occurs with the carbamoyl portion of the molecule (Horwitz etal. 1981), leaving the solvating phosphorus portion of the molecule to interact with the metal ion. These compounds are indeed more efficient extractants of the trivalent metal ions from acidic solutions, able to extract trivalent actinide and lanthanide ions from relatively dilute nitric-acid solutions. Horwitz et al. (1981) have studied the separation of the lanthanides and trivalent actinides from Am to Fm (table 2) using dihexyl-N, N-diethylcarbamoyl-methylphosphonate (DHDECMP) and aqueous nitrate solutions. Steadily decreasing distribution ratios are observed for the lanthanides, but nearly constant D s are found for the trivalent actinides. Group separation does not appear feasible while interlanthanide (but probably not interactinide) separations are possible. However, substitu-... 

Other methods attempt to probe the stmcture of the foam indirectly, without directly imaging it. Eor example, since the Hquid portion of the foam typically contains electrolytes, it conducts electrical current, and much work has been done on relating the electrical conductivity of a foam to its Hquid content, both experimentally (15) and theoretically (16). The value of the conductivity depends in a very complex fashion on not only the Hquid content and its distribution between films and borders, but the geometrical stmcture of the bubble packing arrangement. Thus electrical measurements offer only a rather cmde probe of the gas Hquid ratio, a quantity that can be accurately estimated from the foam s mass density. 

Volume resistance is the ratio of direct voltage applied to the electrodes to that portion of current between them that is distributed through the volume of the specimen. 

Assume that we have a program we will run on np processors and that this program has a serial portion and a parallel portion. For example, the serial portion of the code might read in input and calculate certain global parameters. It does not make any difference if this work is done on one processor and the results distributed, or if each processor performs identical tasks independently this is essentially serial work. Then the time t it takes the program to run in serial on one processor is the sum of the time spent in the serial portion of the code and the time spent in the parallel portion (i.e., the portion of the code that can be parallelized) is t = tg + tp. Amdahl s law defines a parallel efficiency, Pe, of the code as the ratio of total wall clock time to run on one processor to the total wall clock time to run on np processors. We give a formulation of Amdahl s law due to Meijer [42] ... 

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