(745c) Spray-Assembled Composite Polymer-Clay Thin Films As Selective Layers in Reverse Osmosis Membranes

Kovacs, J., Massachusetts Institute of Technology

The development of novel membranes for use in continuous reverse osmosis (RO) processes can reduce the operating costs for modern desalination operations through increasing selectivity and reducing the cost of manufacturing.  Composite, cross-linkable polyelectrolyte and clay thin films assembled via the layer-by-layer (LbL) deposition process can serve as a substitute for the polyamide selective layer in commercially-available membrane systems.  The flexibility of the spray layer-by-layer (spray-LbL) assembly process enables the deposition of large asymmetric thin films orders of magnitude faster than possible through traditional dip-LbL processing.  Composite thin films were assembled on polysulfone nanofiltration membranes, with the composition and physical properties fine-tuned by manipulating the film assembly conditions such as spray time of the film components as well as the number of layers deposited.  Using mathematical modeling on data collected from dead-end permeation experiments, permeability coefficients for water and salt through selective layers of varying film composition were calculated.  These experimental results confirm the viability of using composite polyelectrolyte-clay thin films as selective layers, with significant increases in water permeability observed when compared against commercially-available polyamide membranes.