Solrox 0200 membrane

Plasma polymerization has been explored in considerable detail as a potential route to composite reverse osmosis membranes. Yasuda has written an excellent review covering the fundamentals and progress of plasma polymerization through 1974.88 Advances since then have not been particularly promising from a commercial standpoint, with the exception of the Solrox membrane (see below). 

Table 5.7, taken from a July 1982 technical bulletin by Sumitomo Chemical, lists performance data for a series of Solrox membrane grades that can be made by this process. Of these, the Solrox SC-0200 has been manufactured in tubular form on a semicommercial basis and used within the Sumitomo organization on organic chemical concentration applications. Table 5.8 lists organic rejections for the SC-0200 membrane. 

These organic rejections, while greatly exceeding the capabilities of cellulose acetate membranes, are not appreciably different than rejection levels exhibited by aromatic polyamide membranes (FT-30, Permasep B-9). Nor do they match the organic rejection characteristics of the PEC-1000 membrane. The Solrox membrane is not resistant to chlorine, and its water flux is somewhat low (about 25 gfd at 650 psi net driving pressure). Consequently, it has not become a significant competitive membrane in the world marketplace. 

A membrane designated "Solrox" made by Sumitomo Chemical Company is closely related to the above plasma polymerized composite membranes. A 1980 report by T. Sano described the Sumitomo process (31). A support film was cast from a polyacrylonitrile copolymer containing at least 40 mole percent acrylonitrile. The support film was dried and exposed to a helium or hydrogen plasma to form a tight cross-linked surface skin on the porous polyacrylonitrile support film. Data in a U.S. Patent issued in 1979 to Sano et al showed that the unmodified support film had a water flux of 87 gfd (145 L/ sq m/hr) at 142 psi (10 kg/sq cm). After the plasma treatment a reverse osmosis test using 0.55 percent NaCl at 710 psi (4895 kPa) showed 10.5 gfd (17.5 L/sq m/hr) flux at 98.3 percent salt rejection (32). This membrane appears to fall between a conventional asymmetric membrane and a composite membrane. If the surface skin is only cross-linked, one might call it a modified asymmetric membrane. However, if the surface skin is substantially modified chemically to make it distinct from the bulk of the membrane it could be considered as a composite type. 

Table 5.8 Organic Solute Rejections of SOLROX SC-0200 Membrane in Comparison with Cellulose Acetate Membrane...

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