Liquid membrane system parameters

The Madonna Berkeley (ver.3) solver of ODE, the set of parameters, and initial conditions describing a liquid membrane system (listed in Table 13.2) were applied to numerically investigate the properties of CPS. The main relations resulting from the computations were time-dependent values of (1) the concentration profiles of transported and antiported species in a liquid... 

Selectivity parameters, needed for the BOHLM or BAHLM module design and their determination techniques, are analyzed. Selectivity can be controlled by adjusting the concentration, volume, and flow rate of the LM phase. Such control of the selectivity is one of the advantages of the bulk liquid membrane systems in comparison with other liquid membranes configurations and Donnan dialysis techniques. The idea of dynamic selectivity and determination techniques are presented and discussed. 

Continuing progress is being made in the methemeiical modeling of mass transport in liquid-membrane systems. This should contribute to a better understanding of the parameters that control the rate and efficiency of liquid-membrane processes. 

An important number of references have been published dealing with many applications of supported liquid membranes. Mathematical modeling of the process has been developed and it can be generalized and applied to the determination of the response of different systems containing more than one solute. After evaluation of the parameters, process optimization can be applied using common optimization procedures, as described in the text. 

Shere, A.J. and Cheung, H.M. (1988). Effect of preparation parameters on leakage in liquid surfactant membrane systems. Sep. Sci. Technol, 23, 687-701. 

From the basic parameters initial concentration of ions, their standard transfer potential, distribution coefficients for neutral components, equilibrium constants of reactions taking place in the system, volume of phases, and temperature, a unique general problem for the Galvani potential difference and distribution concentration of all components was established. A numerical solution to the problem with the help of computer program EXTRA.FIFIl provided a good means for quantitative investigation of the liquid-liquid interface. It is also useful for the study of liquid-liquid extraction, electroextraction, voltammetry at interface of two immiscible electrolyte solutions (ITIES) [15,18], liquid-liquid membrane ion-selective electrodes, biomembrane transport, and other fields of science and engineering. 

In such a system, the parameters which affect system performance are a) the total carrier concentration (Cj), b) the solute concentration on each side of the membrane (C q feed, Cm - sweep), c) the forward and reverse rate constants (k and k2 respectively), d) the membrane thickness (L), and e) the diffusion coefficients of the three components In the liquid membrane (Dji, D3, and D/13). 

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 design and scale-up of liquid-membrane separation processes need separation and concentration mathematical models as reported in Section 29.2.1. When complex solutions such as wastewaters are treated, several simplifications according to the specific characteristics of the system are usually assumed in order to reduce the number of parameters and mathematical complexity of the EPT model. From a kinetic point of view, the transport through the membrane... 

Non-linear phenomena such as temporal oscillations and chemical waves in the case of chemical reactions are governed by the autocatalytic reaction (positive feedback) and reaction where the product of autocatalysis is destroyed by some other species (negative feedback). Of course in the case of chemical waves (spatio-temporal oscillations), diffusion does play a role, and the concept of reaction diffusion equation is evoked to predict the dependence of velocity of chemical waves on different parameters. In this chapter, we propose to discuss electrical potential oscillations generated due to coupling of volume flux, solute flux and electric current through solid-liquid interface (membrane systems), liquid-liquid interface, solid-liquid-liquid interface (density oscillator) and liquid-liquid-vapour interface. 

Ideal separation factor Ideal solution Immersion precipitation Immobilised liquid membranes Inorganic membranes Integrally skinned membranes Imcrfaciai polymerisation Interaction parameter Interactive systems Ion-exchange Ionic membranes Ionic strength Isoelectric point Isotaciic polymers... 

The radiol) tic stability of the liquid membrane phase is a fundamental parameter to be evaluated to effectively use the SLM system for the separation of metal ions from HLW. For this purpose, some tests were carried out increasing the radiation dose from OMGy to 1.8 MGy. Obtained results evidenced no significant decrease of the permeability of Am(III) when the radiation dose was lower than 0.46 MGy. However, the permeability decreased almost linearly by increasing the radiation dose from 0.46 to 1.8 MGy (Table 9.9). 

Liquid membrane separation systems possess great potential for performing cation separations. Many factors influence the effectiveness of a membrane separation system including complexation/ decomplexation kinetics, membrane thickness, complex diffusivity, anion type, solvent type, and the use of ionic additives. The role that each of these factors plays in determining cation selectivity and flux is discussed. In an effort to arrive at a more rational approach to liquid membrane design, the effect of varying each of these parameters is established both empirically and with theoretical models. Finally, several general liquid membrane types are reviewed, and a novel membrane type, the polymeric inclusion membrane, is discussed. 

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. 

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