**Roles of Facilitated Transport Through HFSLM in Engineering Applications**

A.W. Lothongkum1, U. Pancharoen2 and T. Prapasawat1 *1Department of Chemical Engineering, Faculty of Engineering, King Mongkut's Institute of Technology Ladkrabang, Bangkok, 2Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand* 

### **1. Introduction**

176 Mass Transfer in Chemical Engineering Processes

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For a number of manufacturing processes, separation, concentration and purification are important to handle intermediates, products, by-products and waste streams. In this regards mass and heat transfer play a significant role to attain efficient results. Concern to the separation operations, they can be classified as energy-intensive interphase mass transfer processes and less energy- or less material-intensive intraphase mass transfer processes (Henley & Seader, 1981). With environmental and energy constraints in these days, for sustainability it is of much concern the requirements of process intensification and looking for the most effective operation based on green chemistry concepts (Badami, 2008; Escobar & Schäfer, 2010; Matthews, 2007). Membrane technologies are a potential sustainable solution in this point of view. In contrast to the energy-intensive interphase mass transfer processes as distillation and extraction, membrane separation is an intraphase-mass-transfer process without the energy-intensive step of creating or introducing a new phase. It involves the selective diffusion of target species through the membrane at different rates. Although membrane operations are a relatively new type of separation process, several of them are fast-growing and successfully not only in biological systems but also a large industrial scale, e.g., food and bioproduct processing (Jirjis & Luque, 2010; Lipnizki, 2010). They can apply for a wide range of applications and provide meaningful advantages over conventional separation processes. In applications of controlling drug delivery, a membrane is generally used to moderate the permeation rate of a drug from its reservoir to the human body. In applications for safety regulations of food packaging, the membrane controls the permeation of undesirable constituents completely. In separation purposes, the membrane allows one component in a feed mixture to permeate itself but prohibits permeation of others. Among several membrane types, supported liquid membranes (SLMs) or immobilized liquid membranes (ILMs) containing carriers or extractants to facilitate selective transport of gases or ions draw high interest of the researchers and users in the industry as they are advanced economical feasible for pre-concentration and separation of the target species. So far, four types of supported liquid membrane modules (spiral wound, hollow fiber, tubular and flat sheet or plate and frame) have been used in the industry (Baker, 2007; Cui et al., 2010). The

Roles of Facilitated Transport Through HFSLM in Engineering Applications 179

4. Organic compounds separation, organic pollutants recovery from wastewaters

The performance of membrane relates closely to its structure, material and module. It is known that porous membranes can be classified according to their structures into microporous and asymmetric membranes. Microporous membranes are designed to reject the species above

In case of membrane materials, polymeric or organic membranes made of various polymers (e.g., cellulose acetate, polyamide, polypropylene, etc) are cheap, easy to manufacture and available of a wide range of pore sizes. However, some limitations like pH, temperature, pressure, etc can impede the applications of polymeric membranes. On the other hand, ceramic or inorganic membranes have advantages of high mechanical strength, high chemical and thermal stability over the polymeric membranes but they are brittle and more

In terms of membrane modules, the development of membrane module with large surface areas of membrane at a relatively low manufacturing cost is very important. Resistance to fouling, which is a particularly critical problem in liquid separation, depends on the membrane module. Of four types of the SLM modules (spiral wound, hollow fiber, tubular and flat sheet or plate and frame), hollow fiber module (Fig.1) has the greatest surface areato-volume ratio resulting in high mass transfer coefficient and is the most efficient type of

Fig. 1. The hollow fiber module (http://www.liquicel.com/product-information/gas-

**Feed inlet Feed outlet**

**Stripping outlet Stripping inlet**

**Hollow fiber**

**Baffle Tube Housing**

**Distribution tube**

6. Fermentation or enzymatic conversion-recovery-separation (bioreactors)

their ratings. They can get blocked easily compared to asymmetric membranes.

8. Wastewater treatment including biodegradable-separation techniques

3. Flat sheet, spiral wound module membranes

2. Biotechnological products recovery-separation 3. Pharmaceutical products recovery-separation

**2.1 Membrane structures, materials and modules** 

**Cartridge**

4. Hollow fiber membranes

5. Gas separations

expensive.

transfer.cfm)

7. Analytical applications

5. Capillary hollow fiber membranes - Classification based on applications 1. Metal-separation concentration

hollow fiber supported liquid membrane (HFSLM) is renowned as a favorable system to separate valuable compounds or pollutants at a very low concentration and has specific characteristics of simultaneous extraction and stripping of the low-concentration target species in one single stage, non-equilibrium mass transfer, high selectivity and low solvent used.

This chapter describes transport mechanisms in HFSLM and shows some applications with reference to our up-to-date publications, for example

