Porous Media and Filtration

Abstract

It seems that the importance of filtering particles from a fluid stream was first recognised for public health reasons. Indeed, the fact that membranous sacs such as bladders could prevent particle dust inhalation was already known to the Romans, and is mentioned by Plinius [21]. However, the generalized use of filters had to wait until technology was sufficiently advanced. In the beginning of the 20th century, Zsigmondy and Bachmann [27] developed the first cellulose derivative membrane filters with great relevance for colloid chemistry. In the early 1960s, the USA produced the first membrane filter made of silver. Besides being electrical conductors, these filters had also the advantage of being very stable in a wide temperature range (140 K to 640 K). The application of the discovery of the phenomenon of etching charged particle tracts in solids, see Fleischer et al. [11], led to the production of nuclepore filters. These filters are characterized by having a very smooth and uniform structure, and high selectivity to submicron particles. Cellulose derivative membrane and nuclepore filters are known as pore filters, see Figure 27.1. Filters made of sintered metals, poly vinyl chloride and Teflon, are examples of these type of filters.