Liquid membrane separation system design

Rational Design of Liquid Membrane Separation Systems... 

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. 

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... 

Figure 1 shows several types of mass transfer or diffusion cells, which are of the simplest design for performing bulk liquid membrane (BLM) processes. Each of the devices is divided into two parts a common part containing the membrane liquid, M and a second part in which the donor solution F and acceptor solution R are separated by a solid impermeable barrier. The liquid, M contacts with the two other liquids and affects the transfer between them. All three liquids are stirred with an appropriate intensity avoiding mixing of the donor and acceptor solutions. For a liquid-ion exchange in a BLM system. Fig. 2 shows the transfer mechanism of cephalosporin anions, P , from donor (F) to acceptor (R) solution... 

The humidification of the reactant gases could be successfully realized by using membrane humidifiers [34, 35]. The water content of a wet stream can be transferred across a semi-permeable membrane to a dry stream (Fig. 4.8). The membrane separates the dry stream compartment from the other compartment crossed by with liquid water or wet stream. Theoretically the dry stream could increase its water vapor content along the entire interface area of the membranes from the inlet up to close the saturation value at the exit of the device. The design includes a tubular form for the humidifier and a counterflow to optimize the exchange. This device could be more suitable for FCS management with respect not only to bubbler humidifier but also to water vapor injection method, as the last systems need additional equipments, make the whole system complex and increase... 

An ion-selective electrode (ISE) is a sensor with a membrane which is designed so that its potential indicates the activity of a specific ion in an electrolyte solution. The membrane may be a solid, either crystalline or glassy, or a liquid. The best known ISE is the glass electrode used to determine pH. The membrane not only develops a potential difference which responds to the unknown ionic activity in the test solution, but it also separates completely the test solution from the internal reference solution of the ISE. Three different ISEs involving glass, crystalline, and liquid membranes are shown in fig. 9.6. All of these systems involve an internal reference electrode. In each case, the membrane is at the bottom of the ISE, which is dipped into the test solution. More details about each of these electrodes are given in the following discussion. 

Huge amounts of liquid byproduct and waste effluents in the fertilizer industry contain various heavy metals, some of which are highly toxic. Cd, Cu, and Zn are commonly encountered in these effluents and are selected for selective removal studies using liquid membrane systems [1-7, 14-17]. Below, experimental and calculated data, obtained for Cd, Cu, and Zn separation, are used for the BAHLM process design considerations. 

We can now design a preliminary pilot setup. We use a spiral-type, flowing liquid membrane module, developed by the Teramoto group [87, 88], in which the effective membrane area is about 40% of the total membrane area (the increase of the membrane area is mainly due to blocking of the membrane surface by spacers, and by the adhesive used to seal the sides of the module). For our system, the total feed-side membrane area is 570 m and the total strip-side membrane area is 763 m , in which 360 m is the area needed for the separation of the strip solution concentrated by copper. By designing standard, three-compartment spiral-type BAHLM modules, with 100 m of the membrane on each side (feed and strip), and two-compartment modules, with 200 m of the membrane, we will obtain a setup, of six standard three-compartment modules and one two-compartment module connected in consecutive order (see Fig. 6.7). After the fourth module, we will... 

In 1979, Baadenhuijsen and Seuren-Jacobs [2] were the first to report on a FI gas diffusion separation system with a semi-permeable dimethylsilicone rubber membrane, used for the determination of carbon dioxide in plasma. In the same year. Zagatto et al.[3] introduced an isothermal distillation FI system in which ammonia diffused from a flowing donor liquid film across an air-gap and absorbed by a flowing acceptor film on the opposite side of the gap. However, later developments on gas diffusion separations mainly followed the approach of Baadenhuijsen and Seuren-Jacobs, obviously due to its simpler design and higher versatility. The first theoretical study on an FI gas-diffusion separation system was attempted by van der Linden [4], who used a tank-in-series model for the mathematical evaluation of the separation process. 

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. 

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