Porous Glass and Metal Membranes

Porous glass has been available for transpon studies for several decades, but its use as a membrane material commercially started only in the early 1980s. Its uses have been mostly in the biotechnology area. Porous silver membranes were available in the mid-1960s in the form of tubes and later in the shape of a disk. The use of silver membranes, however, has been limited. Porous stainless steel membranes have been used for years as high-quality filters or supports for dynamic membranes. 

Practically all the major industrial producers of inorganic membranes in the 1980s were involved in various aspects of the gaseous diffusion operations discussed above. 

It is estimated that a total of more than 100 million porous membrane tubes have been made using the French technology. The process has been found to be very reliable and 

Some of those developments at Oak Ridge were believed to spin off in some form at Union Carbide and some aspects of the efforts led to the commercialization of dyiuunically formed membranes primarily for ultrafiltration and hypeiTiltration (reverse osmosis) applications. In these dynamic membranes, a mixture of zirconium hydroxide and polyacrylic acid deposited on a porous support which provides the necessary mechanical strength. The support is mostly made of porous carbon although porous ceramic and stainless steel are also used. These non-sintered membranes, in great contrast to most of the membranes discussed in this book, are formed in situ and require periodic regeneration with new zirconium hydroxide and polyacrylic acid. 

The dynamic membranes originally developed by Union Carbide are protected by three core patents U.S, 3977967, 4078112, and 4412921 (Trulson and Litz, 1976 Bibeau, 1978 and Leung and Cacciola, 1983) and their foreign equivalents. Those patents cover a broad range of metal oxides such as zirconia, gamma alumina, magnesia alumina spinel, tantalum oxide and silica as the membrane materials and carbon, alumina, aluminosilicates, sintered metals, fiberglass or paper as the potential porous support materials. However, their marketed product, trade named Ucarscp membranes, focused on dynamic membranes of hydrous zirconium oxide on porous carbon support. 

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