(217cz) Composite Asymmetric Bi-Layer PVA-Cellulose Ultrafiltration Membranes

In this study asymmetric hybrid Poly (vinyl alcohol) (PVA) hydrogels were functionalized with iminodiacetic acid (IDA) and Cu²⁺ to optimize the flux, selectivity, and anti-biofouling capabilities of membranes used for water desalination. The use of asymmetric membranes allows for a small mesh size at the surface to eliminate the transport of unwanted species as well as a mesh size gradient along the membranes thickness to minimize transport resistance. In addition to the advancement in transport capabilities by an asymmetric membrane, functionalizing it with a metal such as copper, which interferes with microorganisms’ DNA replication, eliminates the accumulation of microorganisms that are likely to congregate at the membranes surface. Thus, the proposed membranes will reduce the amount of biofouling which tends to alter the membranes flux. Therefore, functionalizing membranes with an IDA-Cu²⁺ complex should maintain flux and decrease biofouling.  The three types of composite asymmetric bi-layer membranes (CABMs) were formed using 1.25% (v/v) and 2.5% (v/v) of the cross-linking agent Glutaraldehyde (GA); (type 1) Nitrogen gas was applied to an ultrafiltration device to impregnate cellulose acetate support membranes with asymmetric PVA layer, (type 2) coated cellulose acetate support membranes with asymmetric PVA layer using a spin-coater and (type 3) manually coated cellulose acetate support membranes with asymmetric PVA layer. Characterization on CABMs using Fourier Transform Infrared spectroscopy (FTIR), Atomic Absorption spectroscopy (AAS), and Scanning electron microscopy (SEM) showed differences in the degree of cross-linking, functionalization by metal attachment and impregnation respectively. SEM micrographs indicate that membranes developed using the Ultrafiltration cell allowed for two homogenous gels to amalgamate leading to a more uniform asymmetric membrane. As an indirect measure of functionalization AAS results suggest that type 3 membranes attached the most Cu²⁺, however the stability of the membranes were compromised. FTIR spectra confirm impregnation in support membranes with asymmetric PVA layer. The membrane performance was evaluated using a dead-end filtration, where preliminary flux data suggest that CABMs have a 66% decrease and 5% increase in flux compared to support membranes coated with a 1.25% and 2.5%(v/v) GA concentration homogenous layers respectively.