Graphene-based nanosheet functionalized membranes - industrial applications

Membrane separations is the umbrella term typically given to operations including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), membrane distillation (MD) and pervaporation (PV). These technologies are widely employed in a diverse number of industries. The primary tradeoff that researchers strive to enhance, regardless of the application (whether gas or solvent separations, water purification or ion/proton transport) is the balance between the flux and the selectivity (e.g., retention of valuable proteins, rejection of unwanted compounds or organic matter and micro-organisms, diffusion of methanol in fuel cells). Foulant molecules such as bacteria, proteins or organic matter can lead to a decline in membrane performance, flux and selectivity. Foulants can adhere or adsorb on the membrane surface and/or in the membrane pores, requiring process controls such as backflushing for reversible fouling, and requiring chemical cleaning in the case of irreversible fouling. This within the thin film active layer of RO/NF membranes, and many more; some of these approaches are summarized within this chapter. This chapter provides a review of the incorporation of, in particular, carbon nanosheets such as graphene and derivatives such as GO, into polymeric and ceramic membranes for application in a wide variety of industries. The focus is on the enhancement of productivity and reduction in fouling characteristics provided by appropriate incorporation of nanosheets during membrane fabrication. Case studies detailing the industries/processes for which they are employed are summarized within each section, the challenges associated with the particular operations and how the incorporation of nanosheets can help to address those challenges are discussed, along with directions for future research.