Chlorine Resistant PBI RO Permselective Membranes.

Abstract : A study was carried out to develop a chlorine-resistant polybenzimidazole (PBI) reverse osmosis (RO) membrane capable of desalting seawater in a single pass to yield potable water. Flux values as high as 28 gfd and rejections in the range of 94-98% were attained with unsupported flat disc specimens from membranes cast on a small laboratory apparatus. Transfer of the laboratory technology to a commercial type roll coater eventually produced satisfactory fabric supported membranes. Development of spiral wound module fabrication techniques ultimately yielded leak-free modules. Time and funding constraints precluded optimization of RO properties to meet the single pass seawater desalination flux and rejection targets. Chlorine sensitivity tests demonstrated that PBI is not chemically degraded. Unsupported disc samples in 5 ppm chlorine showed 90% declines in flux accompanied by increases in rejection. Fabric-supported membranes in spiral wound module configuration showed relatively stable flux values up to 1000 hours. Rejections increased somewhat at the same time. (Author)