N. Yutthasaksunthorn
Georgia Institute of technology,
United States
Keywords: membrane, graphene oxide, separation, fractionation of depolymerized plastic
Summary:
Advances in polymer recycling and upcycling are leading to creation of new complex organic feedstocks containing depolymerization products. Fractionation and separation of such streams with membranes is an attractive target towards developing industrially viable recycling/upcycling processes, but currently available membranes are challenged in these situations. Graphene oxide (GO)-based membranes have already exhibited the potential to revolutionize nanofiltration of aqueous streams, but their use in organic-phase nanofiltration is much less developed. While GO materials are well known for their chemical stability, there are no reliable methods to fabricate and tune organophilic GO membranes. In this work, we invert GO membranes from hydrophilic membranes into organophilic membranes by controlled chemical reduction processes, while simultaneously preventing the collapse of the GO nanosheets into graphite. The strategy is to prepare a series of pillared (intercalated) GO membranes using specific types of intercalants; Toluidine Blue O (TBO) and Solvent Green (SG) then perform controlled reduction using varying concentration of hydriodic acid as reductant and applying the vacuum-assisted processes to organophilic membranes with retaining pillaring (and hence the porosity). The detailed adsorption, diffusion, and permeation measurements are conducted to understand the transport mechanisms in the disordered GO membrane structures. We have fabricated and initially characterized a set of tunably reduced/modified GO-based nanofiltration membranes that are promising for operation in a range of solvent environments. The pillared membranes have the tunable interlayer spacing between 0.8-1.2 nm before reduction. The controllable reduction processes invert the membranes to have a hydrophobic to hydrophilic structures ratio between 3 - 4.5. In particular, The reduced pillaring TBO-GO membranes possess higher permeance of the range of organic solvents. Going forward, the real mixtures from polyethylene depolymerization will be characterized for permeation properties using tailored membranes. Success in the proposed work will enable new applications in the depolymerization area and potentially in many other organic separation processes.