Sourirajan

T. A. Orafino, in S. Sourirajan, ed., Rererse Osmosis and Synthetic Membranes, National Research CouncU, Ottawa, Ontario, Canada, 1977, p. 313. 

The seminal discovery that transformed membrane separation from a laboratory to an industrial process was the development, in the early 1960s, of the Loeb-Sourirajan process for making defect-free, high flux, asymmetric reverse osmosis membranes (5). These membranes consist of an ultrathin, selective surface film on a microporous support, which provides the mechanical strength. The flux of the first Loeb-Sourirajan reverse osmosis membrane was 10 times higher than that of any membrane then avaUable and made reverse osmosis practical. The work of Loeb and Sourirajan, and the timely infusion of large sums of research doUars from the U.S. Department of Interior, Office of Saline Water (OSW), resulted in the commercialization of reverse osmosis (qv) and was a primary factor in the development of ultrafiltration (qv) and microfiltration. The development of electro dialysis was also aided by OSW funding. 

Fig. 11. Schematic of Loeb-Sourirajan membrane casting machine used to prepare reverse osmosis or ultrafiltration membranes. A knife and trough is used to coat the casting solution onto a moving fabric or polyester web which enters the water-filled gel tank. After the membrane has formed, it is washed...

Fig. 12. Scanning electron micrograph of an asymmetric Loeb-Sourirajan membrane.

Cellulose acetate Loeb-Sourirajan reverse osmosis membranes were introduced commercially in the 1960s. Since then, many other polymers have been made into asymmetric membranes in attempts to improve membrane properties. In the reverse osmosis area, these attempts have had limited success, the only significant example being Du Font s polyamide membrane. For gas separation and ultrafUtration, a number of membranes with useful properties have been made. However, the early work on asymmetric membranes has spawned numerous other techniques in which a microporous membrane is used as a support to carry another thin, dense separating layer. 

Interfdci l Composite Membra.nes, A method of making asymmetric membranes involving interfacial polymerization was developed in the 1960s. This technique was used to produce reverse osmosis membranes with dramatically improved salt rejections and water fluxes compared to those prepared by the Loeb-Sourirajan process (28). In the interfacial polymerization method, an aqueous solution of a reactive prepolymer, such as polyamine, is first deposited in the pores of a microporous support membrane, typically a polysulfone ultrafUtration membrane. The amine-loaded support is then immersed in a water-immiscible solvent solution containing a reactant, for example, a diacid chloride in hexane. The amine and acid chloride then react at the interface of the two solutions to form a densely cross-linked, extremely thin membrane layer. This preparation method is shown schematically in Figure 15. The first membrane made was based on polyethylenimine cross-linked with toluene-2,4-diisocyanate (28). The process was later refined at FilmTec Corporation (29,30) and at UOP (31) in the United States, and at Nitto (32) in Japan. 

Reverse Osmosis. This was the first membrane-based separation process to be commercialized on a significant scale. The breakthrough discovery that made reverse osmosis (qv) possible was the development of the Loeb-Sourirajan asymmetric cellulose acetate membrane. This membrane made desalination by reverse osmosis practical within a few years commercial plants were installed. The total worldwide market for reverse osmosis membrane modules is about 200 million /yr, spHt approximately between 25% hoUow-ftber and 75% spiral-wound modules. The general trend of the industry is toward spiral-wound modules for this appHcation, and the market share of the hoUow-ftber products is gradually falling (72). 

S. Loeb and S. Sourirajan, "Sea Water Demineralisation by Means of an Osmotic Membrane," in Saline Water Conversion-11, Fidvances in Chemistry Series Number 28, American Chemical Society, Washington, D.C., 1963. 

S. Sourirajan and T. Matsuura, Reverse OsmosisjPltrafiltration Principles, National Research Council of Canada, Ottawa, Canada, 1985. 

S. Sourirajan, "Reverse Osmosis— Process Eundamentals" in The Encyclopedia of Environmental Science and Engineering Gordon and Breach Science Pubbshers, Inc., New York, 1976, p. 738. 

Orofino, T. A. (1977). Technology of hollow fiber reverse osmosis systems. In Reverse Osmosis and Synthetic Membranes (S. Sourirajan, eds.), pp. 313-341 National Research Council, Ottawa, Canada. 

Sourirajan, S., and Matsuura, T. (1985). Reverse Osmosis/Uitrafiltration Process Principles, National Research Council, Ottawa, Canada. 

A. F. Turbak, ed. Synthetic Membranes. Washington, DC American Chemical Society, 1981 S. Sourirajan and T. Matsuura (eds.). Reverse Osmosis and Ultrafiltration. Washington, DC American Chemical Society, 1985. 

S. Sourirajan. Reverse Osmosis. New York Academic Press, 1970. 

Commercial interest in RO began with the first high-flux, high-NaCl-retention Loeb-Sourirajan anisotropic cellulose acetate membrane. Practical application began with the thin film composite (TFC) membrane and implementation for seawater desalination at Jeddah, Saudi Arabia [Muhurji et ak. Desalination, 76, 75 (1975)]. 

Uhlhom, R. J. R., K, Keizer and A. J. Burggraaf. 1989. Formation of and gas transport properties in ceramic membranes. In Advances in Reverse Osmosis and Ultrafiltration eds. T. Matsuura and S. Sourirajan, pp. 239-59. Nat. Res. Council Canada, Ottawa. 

It is little wonder then that so many contributors from so many countries throughout the world responded so enthusiastically to the initial announcement regarding the organization of a symposium to recognize, honor, and pay tribute to Drs. Sidney Loeb and S. Sourirajan on the 20th anniversary of their initial contribution. 

I know that I speak for all of their many friends when I take this opportunity to wish Drs. Loeb and Sourirajan continued good health and, if possible, even more success in their future research and development efforts. 

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