Graphene Oxide Quantum Dots Incorporated into a Thin Film Nanocomposite Membrane with High Flux and Antifouling Properties for Low-Pressure Nanofiltration

Graphene oxide quantum dots (GOQDs), novel carbon-based nanomaterials, have attracted tremendous research interest due to their unique properties associated with both graphene and quantum dots. In the present study, thin film nanocomposite (TFN) membranes comprising GOQDs dispersed within a tannic acid (TA) film were fabricated by an interfacial polymerization reaction for low-pressure nanofiltration (NF). The resultant TA/GOQDs TFN membranes had measurably smoother and more hydrophilic, negatively charged surfaces compared to the similarly formed TA thin film composite (TFC) membrane. Owing to the loose active layer structure and the combination of Donnan exclusion and steric hindrance, the TA/GOQDs TFN membrane showed a pure water flux up to 23.33 L/m²·h (0.2 MPa), which was 1.5 times more than that of pristine TA TFC membrane, while high dye rejection to Congo red (99.8%) and methylene blue (97.6%) was kept. In addition, the TA/GOQDs TFN membrane presented better antifouling properties, which was ascribed to the favorable changes in membrane hydrophilicity, ζ-potential, and surface roughness. These results indicated the great potential of such membranes in wastewater treatment, separation, and purification in many industrial fields

High-Performance PEBA2533-Functional MMT Mixed Matrix Membrane Containing High-Speed Facilitated Transport Channels for CO₂/N₂ Separation

A novel mixed matrix membrane was fabricated by establishing montmorillonite (MMT) functionalized with poly­(ethylene glycol) methyl ether (PEG) and aminosilane coupling agents in a PEBA membrane. The functional MMT played multiple roles in enhancing membrane performance. First, the MMT channels could be used as high-speed facilitated transport channels, in which the movable metal cations acted as carriers of CO₂ to increase the CO₂ permeability. Second, due to mobility of long-chain aminos and reversible reactions between CO₂ and amine groups, the functional MMT could actively catch the CO₂, not passively wait for arrival of CO₂, which can facilitate the CO₂ transport. At last, PEG consisting of EO groups had excellent affinity for CO₂ to enhance the CO₂/N₂ selectivity. Thus, the as-prepared functional MMMs exhibited good CO₂ permeability and CO₂/N₂ selectivity. The functional MMM doped with 40 wt % of MMT-HD702-PEG5000 displayed optimal gas separation with a CO₂ permeability of 448.45 Barrer and a CO₂/N₂ selectivity of 70.73, surpassing the upper bound lines of the Robeson study of 2008