Characterization of polymeric membranes: sulfonated polysulfones

Sulfonated polysulfone has been shown to possess desirable physical properties for use as a reverse osmosis desalination membrane. In this work, an extensive of dense membranes made from sulfonated polysulfone having 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0 degree of sulfonation is described. The degree of sulfonation (D.S.) was maintained during the membrane fabrication process as evidenced by IR analysis. The effect of the degree of sulfonation and the counter ion, namely Na and K, on the properties of the membrane were examined. The hydrophilic nature of the material increased with increasing degrees of sulfonation, as evidenced by water uptake and the contact angle of water on the membrane surface. The amount of water increased from 0.6% for polysulfone to 19.2% for sodium salt of sulfonated polysulfone with D.S. of 1.0, and 12.2% for potassium salt of sulfonated polysulfone with D.S. of 1.0. The contact angle of water on polysulfone membranes was 75.1°. The contact angle of water decreased to 25.5° and 60.3° for sodium and potassium salt of sulfonated D.S. = 1.0) polysulfone, respectively. The decrease in the contact angle of water indicated an increase in the hydrophilicity of the membrane surface. Both the water uptake study and the contact angle measurement indicated greater hydrophilicity for the sodium salts of sulfonated polysulfone when compared to the potassium salts of sulfonated polysulfone for a given degree of sulfonation. The nature of the water within the membrane was found to be less hydrogen-bonded when compared to the bulk water. The surface of the membrane and the polymer powder was found to be different by ESCA analysis, and were also different from the bulk of the material. Neither the membrane surface nor the polytner powder surface had the same stoichiometry as the bulk. Ion exchange occurred not only on the membrane surface, but extended into the bulk with an overall ion exchange of about 80%. Electrical properti.es of the membranes were investigated by measuring the partial ionic conductivity and the selectivity of the membrane. The electrolyte/membrane/ electrolyte system showed ohmic behaviour. The membrane potential difference under applied transient current was greatly dependent on the nature of the cation, whereas the nature of the anion had no effect. The activation energy had minimal dependence on the membrane thickness, but depended on the nature of the electrolyte system. The effective size of the ion-conducting channels seemed to increase with higher degrees of sulfonation, probably due to a swelling process. SEM photomicrographs were taken to study membrane morphology and, in some cases, performance as a reverse osmosis membrane could be predicted from the SEM photomicrographs .

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Chemistry

Department dc:contributor.department

Chemistry

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1981

Author dc:creator

• Kang, Yoonok

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/71146

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/71146