Membranes Loeb-Sourirajan

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.

Figure 3.8 Scanning electron micrographs of aromatic polyamide (Nomex, Du Pont) Loeb-Sourirajan membranes cast from 22 and 18 wt% Nomex in dimethylacetamide [19]...

Table 3.2 Historically important examples of conditions for preparation of solution-precipitation (Loeb-Sourirajan) membranes...

A typical three-component phase diagram for the components used to prepare Loeb-Sourirajan membranes is shown in Figure 3.11. The comers of the... 

Later Henis and Tripodi [73] showed that membrane defects in anisotropic Loeb-Sourirajan membranes could be overcome in a similar way by coating the membrane with a thin layer of a relatively permeable material such as silicone rubber. A sufficiently thin coating does not change the properties of the underlying selective layer but does plug defects, through which simple convective gas flow can occur. Henis and Tripodi s membrane is illustrated in Figure 3.29. The silicone rubber layer is many times more permeable than the selective layer and... 

During the 1960s and 1970s the Office of Saline Water sponsored development of noncellulosic reverse osmosis membranes. Many polymers were evaluated as Loeb-Sourirajan membranes but few matched the properties of cellulose acetate. Following the development of interfacial composite membranes by Cadotte, this line of research was abandoned by most commercial membrane producers. 

Loeb-Sourirajan membranes based on sulfonated polysulfone and substituted poly(vinyl alcohol) produced by Hydranautics (Nitto) have also found a commercial market as high-flux, low-rejection membranes in water softening applications because their divalent ion rejection is high. These membranes are also chlorine-resistant and have been able to withstand up to 40 000 ppm h of chlorine exposure without degradation.1 The structures of the polymers used by Hydranautics are shown in Figure 5.8. 

Figure 8.8 The technique devised by Henis and Tripodi [23] to seal defects in their selective polysulfone Loeb-Sourirajan membrane...

SCHEMATIC DIAGRAM OF A LOEB-SOURIRAJAN MEMBRANE CASTING MACHINE... 

The first composite reverse osmosis membrane to be developed and described consisted of an ultrathin film of secondary cellulose acetate deposited onto a porous Loeb-Sourirajan membrane.3 The ultrathin film of cellulose acetate was fabricated by a water surface float-casting technique. This has been described to some extent in the published technical literature,4 5 and in considerable detail in several reports on government-funded research projects.3 6 Figure 5.2 illustrates this process schematically. 

S. Loeb, The Loeb—Sourirajan membrane how it came about, ACS Symp. Ser. 153 (1981) 1-9. 

Preparation of Asymmetric Loeb-Sourirajan Membranes, Polymer Letters Edition Vol. 11, pp. 201-205 (l9T3) co-authors M. T. So,... 

HISTORY OF CELLULOSE ACETATE MEMBRANE 2.2.1 Development of Loeb-Sourirajan Membrane... 

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