Sulfonated Polymer Composites NS-200 Membrane

Several composite membranes have been prepared based on sulfonated polymers. These are typically formed on microporous polysulfone supports by solu- 

The most outstanding property of the NS-200 membrane was its extremely high salt rejection. In simulated seawater tests, salt rejection levels of 99.8 to 99.9% were rountinely observed. Typical performance in a 1,500 psi test on 3.5% synthetic seawater at 25°C was 20 gfd and 99.9% salt rejection. In a few instances, laboratory samples of NS-200 membranes with fluxes of 40 to 50 gfd under these same test conditions were obtained. 

In subsequent efforts on the commercialization of this membrane, in flat sheet form, water fluxes of up to 23 gfd (99.6% salt rejection) at 800 psi on simulated seawater72 and 50 gfd (98% salt rejection) on 0.5% sodium chloride at 250 psi73 were achieved. 

Membrane instability was believed to result from hydrolytic cleavage of sulfate and sulfonate esters in the sulfonated polyfurane resin. This hydrolysis would entail some depolymerization of the resin and concurrent formation of ionic sulfonate groups, causing the membrane to absorb water and swell in monovalent salt solutions. Oxidation by dissolved oxygen is another potential 

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