(485e) Optimizing Polysulfone Mixed Matrix Membranes for High Permeate Flux in Membrane Distillation

The development of low-cost membranes specific to Membrane Distillation (MD) remains a major challenge to the progression of the technology towards commercialization. This is because the desirable properties and morphology for an ideal MD membrane are fundamentally different from most commercially available membranes. MD membrane should be hydrophobic and highly porous. The hydrophobicity is so that liquid water does not pass through, and high porosity allows for more space for the water vapor molecules to pass through. Polysulfone is a well-known hydrophobic and thermally resistant polymer, which makes it a good polymer candidate to produce laboratory fabricated membranes.

Additives to the membrane matrix are known to affect the pore-formation mechanism. Morphological studies on GO mixed matrix membranes show that the GO particles tend to aggregate near the surface of the membrane, contributing to a stronger negative surface charge due to the oxygen-containing functional groups. Adding graphene oxide (GO) can increase the hydrophilicity and surface charge of the membrane. This hydrophilicity can be engineered by using thiolated graphene, with sulfur-containing functional groups such as thiol. The sulfur would theoretically contribute less hydrophilicity than the oxygen, due to sulfur having a lower electronegativity oxygen on the Pauling scale.

In this research study, Polysulfone/Graphene Oxide and Polysulfone/Thiolated Graphene mixed matrix membranes were produced using the phase inversion method and tested for permeate flux and salt rejection on MD. Wet phase inversion is a well-known method that can be used to produce membranes in the laboratory without the need for overly sophisticated technology. Morphological studies of fabricated membranes were done using SEM. The effects of membrane thickness, coagulation temperature, and graphene-type additive weight percentage on the permeate flux and salt rejection were quantified.