| This thesis shows that alternating polyelectrolyte deposition on porous supports yields nanofiltration membranes that allow high water flux along with selective ion transport. Membranes composed of 4.5 to 5 layer pairs of poly(styrene sulfonate) (PSS)/poly(allylamine hydrochloride) (PAH) on porous alumina allow water fluxes of 1 to 2 m3m-2d -1 at 4.8 bar while exhibiting MgSO4 rejections of 96%. In general, divalent-ion rejection increases when the charge of the outer layer of the membrane matches that of the ion being rejected. Increasing the concentration of supporting electrolyte present during deposition of the terminating PSS layer results in a higher surface charge density, and hence higher Na 2SO4 rejections. The use of PSS/poly(diallyldimethylammonium chloride) bilayers as a gutter layer underneath the selective PSS/PAH skin allows for higher water fluxes on both alumina and polymeric supports. Preliminary research shows that the use of polyelectrolyte films for nanofiltration may allow for repair of fouled membranes. Removal of the surface layer (along with fouling material) from the membrane using high pH buffer, and adsorption of a new surface layer may regenerate the membranes. |
