Development of a Composite Reverse Osmosis Membrane for Single Pass Seawater Desalination

摘要

The objective was to develop an improved reverse-osmosis composite non-cellulosic membrane for the single pass desalination of seawater, and to demonstrate its performance in the form of four inch diameter spiral elements. Three membranes were investigated. One membrane consisted of an active barrier layer of polymerized and sulfonated furfuryl alcohol deposited on the surface of a cloth-backed polysulfone microporous support (SPFA membrane). This membrane exhibited outstanding initial reverse-osmosis properties (water fluxes up to 23 gfd at 99.6% salt rejection with simulated seawater at 800 psi), but was inherently unstable. The seat of the instability is believed to lie in the hydrolytic cleavage, with attendant depolymerization, of sulfate ester groups present in the barrier layer. Another membrane consisted of a sulfonated, phenol-aldehyde resin on the same polysulfone support (SPAR). This membrane was also inherently unstable for the reason noted above. The third membrane, which consisted of a sulfonated polyphenylene oxide on the same polysulfone support (SPPO), was found to be unsuitable for the single pass desalination of seawater. It was concluded from the overall experimental data that the fabrication of composite membranes at elevated temperatures in the presence of sulfuric acid is probably attended by complex side reactions, one or more of which could easily lead to membrane instability.