Membrane Preparation Method

Phase Inversion (Solution Precipitation). Phase inversion, also known as solution precipitation or polymer precipitation, is the most important asymmetric membrane preparation method. In this process, a clear polymer solution is precipitated into two phases a soHd polymer-rich phase that forms the matrix of the membrane, and a Hquid polymer-poor phase that forms the membrane pores. If precipitation is rapid, the pore-forming Hquid droplets tend to be small and the membranes formed are markedly asymmetric. If precipitation is slow, the pore-forming Hquid droplets tend to agglomerate while the casting solution is stiU fluid, so that the final pores are relatively large and the membrane stmcture is more symmetrical. Polymer precipitation from a solution can be achieved in several ways, such as cooling, solvent evaporation, precipitation by immersion in water, or imbibition of... 

Fig. 17 Summary of composite imprinted membrane preparation methods...

Their historical developments and various membrane preparation methods will be discussed in Chapters 2 and 3, respectively. Chapter 4 reviews the general separation and non-separation properties of the membranes and the methods by which they are measured. Chapter 5 presents commercial membrane elements and modules and their application features which are followed by discussions of liquid-phase separation applications in Chapter 6. Many of those applications are commercially practiced. Potential gas separation and other applications (such as sensors and supports for liquid membranes) will be discussed in Chapter 7. 

In this major section the fundamentals and the main problems of these pressure-driven membrane processes will be summarized. A short overview will then be given of the membrane preparation methods and the most common materials used. Their application in organic media will then be reviewed in more detail, followed by comments on the current commercial membrane market and some perspectives for the future. 

BasUe et al. [46] studied the WGSR in a palladium membrane reactor and showed the importance of the membrane preparation method in obtaining high-quality membrane materials. Magnetron sputtering, physical vapour deposition and co-condensation techniques were applied to realize submicron palladium... 

Kariduraganavar, M.Y., Nagarale, R.K., Kittur, A.A. and Kulkarni, S.S. 2006. Ion-exchange membranes Preparative methods for electrodialysis and fuel cell applications. Desalination 197 225-246. 

Porous ceramic membranes have been reviewed from the viewpoint of membrane preparation methods and applications for separation. These new classes of porous ceramic membranes hold considerable promise in applications such as separation at high temperatures. A membrane reaction where separation and reaction is combined in one system, will be realized using porous ceramic membranes, since most chemical reactions occur at high temperature where polymeric membranes cannot be applied. The preparation of porous ceramic membranes, which need to have uniform pore sizes, to be as thin as possible without defects, seems to represent a different strategy from conventional preparation of ceramic bulk bodies. This new research field of ceramic processing will contribute much to the development of membrane science and technology. 

As it has been pointed out in past years [2], the most critical concerns of the alkaline membrane fuel cell technology are the low conductivity and the relatively poor stability of the anion exchange membranes that exist in the first years of the alkaline membrane fuel cell development. Before discussing these main concerns, a short review of anion exchange membrane preparation methods is presented. 

Chapter 4 is the most comprehensive chapter of the book on the carbon membrane preparation. In this chapter selection of the polymeric precursor membrane, preparation of polymeric membrane, pre-treatment before pyrolysis, pyrolysis and membrane post-treatment are dealt with. Furthermore, the membrane preparation method is described in this chapter as much in detail as possible. 

Dependence of the membrane properties from the membrane preparation method. In the case of very weak polybases, such as POSAI, it was possible to mix the polybase with the polymeric sulfonic acid in the same (dipolar-aprotic)... 

The separation layer, either porous or dense, can be formed using different methods such as sol-gel and template routes, hydrothermal synthesis, chemical vapor deposition (CVD), or physical sputtering, depending on the membrane material and its application. These membrane preparation methods will be described in the following chapters of this book for different membranes and membrane reactors. We note that the preparation of inorganic membranes involves a multi-step high-temperature treatment process. Therefore, inorganic membranes are much more expensive than polymeric ones. 

In an industrial use, the following two characteristics are important. First, pore size must be appropriate for the purpose of separation. Smaller pore size is not necessarily better because it may be necessary to concentrate a valuable (useful component such as an enzyme) and also necessary to purify (separation of impurities that are larger than a valuable) by permeating a valuable. Furthermore, a narrow pore size distribution is also important. Thus, the membrane preparation method used in the production of MF/UF must capable of the selective production of a specified range of pore sizes from a wide range of pore sizes. Second, economic efficiency must be adequate to allow for the variations in pore sizes needed. The economic efficiency can be represented by the formula ... 

Typical membrane preparation methods and features and examples of materials of membranes obtained by each of the methods are shown in Table 5.2. A list of certified MF/UF membranes for water supply based on the certified membrane modules for water supply... 

In this nanocomposite membrane preparation method, inorganic nanoparticles with functional groups can be connected with polymer chains by covalent bonds. However, the problem of the aggregation of inorganic fillers in the fabricated membranes still remains. Figure 19.9 shows the in situ polymerization method. 

This chapter will focus on composite membranes for hydrogen separation and, specifically, on Pd and Pd-alloy composite membranes. Preparation methods will be described, and chemical and physical stability in relation to specific applications will be discussed. Performances in membrane reactors and significant developments up to and including the prototype scale will be also presented. 

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