Development of Chlorine Resistant Membranes, Polyimide Membranes and Porous Substrates

摘要

Concurrent studies were carried out for the development of chlorine-resistant composite membranes, polyimide (PI) membranes, and porous substrates for composite membranes. A synthesized tertiary polyimide (based on poly (oxetane) secondary diamine) was used to develop composite membranes which were evaluated for reverse osmosis (RO) performance on chlorinated feeds. A novel tertiary polyurethane (reaction of piperazine and ethylene bischloroformate) was also synthesized, and tested in composite membrane application using thin film deposition. Further, continuous machine fabrication technology was examined for asymmetric polyimide membranes having competitive RO performance, and PI thin film deposition was studied to form composite membranes. New porous supports were also developed, characterized, and successfully used in continuous thin film composite membrane formation. Refinements in formulation and fabrication conditions for PI membranes resulting in continuous machine casting in a 1-foot width to give membranes with exceptional transport properties. Control of key variables gave 50-foot long runs of continuous PI membrane with 14-17 GFD flux and 97-98% salt rejection. The results clearly demonstrate the ability to fabricate asymmetric (continuous sheet) PI membrane from commercial polymer and to incorporate this into a standard spiral element configuration.