Separation factor mixed phases

Another solvent extraction scheme uses the mixed anhydrous chlorides from a chlorination process as the feed (28). The chlorides, which are mostly of niobium, tantalum, and iron, are dissolved in an organic phase and are extracted with 12 Ai hydrochloric acid. The best separation occurs from a mixture of MIBK and diisobutyl ketone (DIBK). The tantalum transfers to the hydrochloric acid leaving the niobium and iron, the DIBK enhancing the separation factor in the organic phase. Niobium and iron are stripped with hot 14—20 wt % H2SO4 which is boiled to precipitate niobic acid, leaving the iron in solution. 

Kulprathipanja and coworkers reported the preparation of integrally skinned siUcaUte-1/cellulose acetate flat sheet asymmetric mixed-matrix membranes via phase inversion technique in 1992 [73]. The O2/N2 separation performance of these membranes was investigated. It was demonstrated that the separation factor of... 

Finally, we should mention the phenomenon of incompatibility of mixtures of polymer solutions. It applies to nearly all combinations of polymer solutions when the homogeneous solutions of two different polymers in the same solvent are mixed, phase separation occurs. For example, 10% solutions of polystyrene and poly(vinyl acetate), each in benzene, form two separated phases upon mixing. One phase contains mainly the first polymer, the other phase mainly the second polymer, but in both phases there is a certain amount of the other polymer present. This limited compatibility of polymer mixtures can be explained thermodynamically and depends on various factors, such as the structure of the macromolecule, the molecular weight, the mixing ratio, the overall polymer concentration, and the temperature. 

The process engineering tasks are classified according to the product groups for which they are used. There are four main areas material mixing, material separation, reaction, and phase transformation. The common factor of all the processes in Table 2.1 is of course the high-viscosity phase and consequendy the specific difficulties of the machinery (technical design, dimensioning with respect to forces, torques, drive power, pressures). 

The incompatibility phenomenon relates to both the occupation of a volume of the solution by macromolecules and the weak repulsion between unlike macromolecules. Phase separation in mixed solutions of a large number of biopolymers studied is sensitive to entropy factors given by the excluded volume of the macromolecules. Phase behaviour strongly depends, therefore, on the molecular weight and the conformation of the macromolecules. The excluded volume effect that depends on the size and shape of the macromolecules determines the phase separation threshold, water partition between the phases of WIW emulsions and biopolymer activity in mixed solution (Tolstoguzov 1986, 1991, 1992). 

M DOP, the mixing time being 10 minutes. Under these conditions the Eu/Am separation factor is about 30, and triple extraction transfers 97 europium into the organic phase. 90% Am stay in the aqueous phase, where the content of Eu is no higher than 3%. Americium can then be quantitatively extracted by 0.04 M DOP toluene solution, the phases being mixed for 45 minutes. 

When an ion exchange membrane is equilibrated with a mixed salt solution, the ratio of ions in the membrane phase attains an equilibrium, as for an ion exchange resin.20 The preference of the ion exchange membrane for one of the two counterions is expressed by a separation factor, a , in which the concentration of ions is expressed by equivalent,... 

This application is based on the hydrophilicity of the ion exchange membrane. Though it is not essential to use an ion exchange membrane,219 they show excellent performance in pervaporation for dehydration of organic solvents. Pervaporation is the separation of solvents on the basis of their different affinities for the membrane and different permeation speeds through the membrane phase. The system consists of a liquid mixture to be separated, which contacts one side of the membrane, and a gas phase to permeate under reduced pressure, which is on the other side of the membrane (Figure 6.37). Membrane performance is evaluated by a permeability coefficient (flux) and separation factor (selectivity coefficient). The permeability coefficient, Q, is the permeated solvent through the membrane per unit area and unit time (kgm 2 h1). When a mixed solvent composed of components A and B is separated, the separation factor, a, is defined as... 

Figure 2.13. Plot of the gas-liquid partition coefficients (Ka and Kb) on two stationary phases to estimate the gas-liquid partition coefficients for all solutes at any intermediate mixed-phase composition and the resulting window diagram plot of the separation factor (a) as a function of the volume fraction of the B stationary phase. (From ref. [205] Elsevier)...

The most polar components of an RP-HPLC mobile phase will often be water (HOH), acetonitrile (CH3—C=N), or methanol (CH3OH). The polarity of the mobile phase can be adjusted to values between these by mixing them in different proportions. Even less-polar compounds, such as ethanol, tetrahydrofuran, or diethyl ether, may be added to bring the overall eluent polarity down even more, or to introduce different interaction mechanisms of polarity which may increase the separation factor a between close pairs of analytes. Being at the extreme end of the polarity scale, water is often considered the fundamental component of the mobile phase mixture, and the other less-polar, organic solvents which may be added are termed organic modifiers ... 

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