(660b) Using Nanocomposite Materials Technology to Improve the Properties of RO Membranes

Composite reverse osmosis (RO) membranes were formed by interfacial polymerization of polyamide thin films over pure polysulfone and nanocomposite-polysulfone porous support membranes. Nanocomposite supports were formed from four different sized amorphous non-porous silica nanoparticles, a crystalline microporous zeolite nanocrystal, and an organic modified form of the zeolite. For each hand-cast membrane, water flux and NaCl rejection were monitored over time for two different applied pressures. Nanocomposite-polysulfone supported RO membranes generally had higher initial permeability and experienced less flux decline due to compaction than pure polysulfone supported membranes. In addition, observed salt rejection generally increased with compaction. Cross-sectional SEM images verified significant reduction in thickness of pure polysulfone supports, whereas nanocomposites better resisted compaction due to enhanced mechanical stability imparted by the nanoparticles. A conceptual model was proposed to explain the mechanistic relationship between support membrane compaction and observed changes in water flux and salt rejection. Nanocomposite-supported RO membranes represent one potential approach to mitigate internal, irreversible fouling due to membrane compaction, particularly in high-pressure applications like seawater desalination.