(340c) Chemically Crosslinking Graphene Oxide and Chitosan for Scalable Water Treatment Membranes

Graphene Oxide (GO) has emerged as a next generation material for water treatment. Although numerous studies have focused on the use of GO as an adsorbent material, recent models proposed in the literature suggest that graphene oxide can be effectively applied toward membrane technologies. However fabrication of GO membranes for separation processes has been limited to small-scale vacuum filtration with an anodized aluminum oxide Anodisc®. This is due to the need for aluminum (Al) ions to crosslink the stacked GO layers preventing the membranes from breaking down from electrostatic repulsion in water. The acidic nature of GO causes Al ions to leach into the GO solution and crosslink oxygen functionalities between the GO lamellar layers keeping the membrane intact when submerged. The vacuum-assisted self-assembly (VASA) method is effective but limits the scale and scope in which these membranes can be studied and used.

To remedy this problem GO was crosslinked with chitosan (CSGO) to form a composite material that can be wet cast and fabricated at any size via convective deposition. The CSGO membraneâ??s performance was tested in a crossflow reactor and challenged with a positively charged dye (methylene blue). The CSGO membranes were able to remove 100% of methylene blue from solution at concentrations ranging from 1-100 ppm. Mass balances obtained from the concentrate and permeate are indicative of size exclusion for the mechanism of removal. The flux rates for these solutions ranged from 2-4.5 LMH with a transmembrane pressure of 50psi. Future work involves increasing the flux across the membrane, while maintaining removal rates, and challenging CSGO composites with negatively charged dyes, radionuclides, divalent and monovalent salts.