Emulsion liquid membranes parameters

Co-anion type and concentration are examined as parameters that can be varied to achieve various metal cation separations in macrocycle-facilitated emulsion liquid membranes. Membrane systems where the metal is present in the source phase as a complex anion or as a neutral complex (cation-anion(s)) are discussed. The experimental separations of Cd(II) from Zn(II) and/or Hg(II), Au(I) from Ag(I), and Au(III) from Pd(II) or Ag(I) are given to illustrate separation design using these membrane systems. The separations are discussed in terms of free energies of hydration, distribution coefficients, and equilibrium constants for the various interactions that occur. 

The preparation and splitting of emulsions are the key parameters in an emulsion liquid membrane process. A very stable emulsion which avoids any loss of emulsified droplets is a prior condition for the feasibility of the process. However, the more stable the emulsion, the more difficult to split it. So both steps are dependent on each other and have to be optimized, also with regard to cost optimization. In the present work, we try to calculate the flow pattern in the two steps using CFD (computational fluid dynamics) software in order to improve the design of the two steps. 

Mass transfer in emulsion liquid membrane (ELM) systems has been modeled by six differential and algebraic equations. Our model takes into account the following mass transfer of the solute across the film between the external phase and the membrane phase chemical equilibrium of the extraction reaction at the external phase-membrane interface simultaneous diffusion of the solute-carrier complex inside globules of the membrane phase and stripping of the complex at the membrane-internal phase interface and chemical equilibrium of the stripping reaction at the membrane-internal phase interface. Unlike previous ELM models fi om which solutions were obtained quasi-analytically or numerically, the solution of our model was solved analytically. Arsenic removal fi om water was chosen as our experimental study. Experimental data for the arsenic concentration in the external phase versus time were obtained. From our analytical solution with parameters estimated independently, we were able to obtain an excellent prediction of the experimental data. 

The following parameters were calculated to characterize the emulsion liquid membrane transport processes ... 

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