Construction of graphene oxide membrane through non-covalent cross-linking by sulfonated cyclodextrin for ultra-permeable butanol dehydration

Adsorption-enhanced Fenton catalytic membrane for high-efficiency, high-quality drinking water treatment

To efficiently remove micropollutants from drinking water, this study developed an adsorption-enhanced Fenton catalytic membrane with a two-dimensional structure composed of graphene oxide loaded with iron-cyclodextrin metal-organic frameworks (FeCD-MOF). As water passes through the interlayer channels, micropollutants and hydrogen peroxide (H2O2) are adsorbed into the voids of the FeCD-MOF and the cavities of the CD. This process increases the concentration of micropollutants and H2O2 in the confined space, thereby significantly enhancing the efficiency of the Fenton catalytic reaction. Under a constant flux of 90 L/m2h and influent concentrations of 10 mg/L bisphenol A (BPA) and 3 mM H2O2, the membrane consistently maintained over 97.4 % BPA removal for 72 h. FeCD-MOF's excellent adsorption properties also enhance the stability of the treated water quality. Even with sudden increases in micropollutant concentration or interruptions in oxidant supply, the membrane maintained over 89.7 % BPA removal for an extended period solely through its adsorption capacity. Experimental results demonstrate that the membrane effectively removes various micropollutants, performs stably across a wide pH range, and resists interference from natural organic matter and ions, making it highly promising for drinking water treatment. Furthermore, compared to other MOF materials, FeCD-MOF has a significantly lower cost, enhancing its practicality.

Design of PDMS/PAN composite membranes with ultra-interfacial stability via layer integration

The interfacial interaction between the selective layer and porous substrate directly determines the separation performance and service lifetime of functional composite membranes. Till now, almost all reported polymeric selective layers are physically in contact with the substrate, which is unsatisfactory for long-term operation. Herein, we introduced a functional composite membrane with ultra-interfacial stability via layer integration between the polydimethylsiloxane selective layer and polyacrylonitrile substrate, where a facile light-triggered copolymerization achieved their covalent bonding. The critical load for the failure of the selective layer is 45.73 mN when testing the interfacial adhesion, i.e., 5.8 times higher than that before modification and significantly higher than previous reports. It also achieves superior pervaporation performance with a separation factor of 9.54 and membrane flux of 1245.6 g m-2 h-1 feeding a 1000 ppm phenol/water solution at 60 °C that is significantly higher than the same type of polymeric ones. Not limited to pervaporation, such a strategy sheds light on the design of highly stable composite membranes with different purposes, while the facile photo-trigged technique shows enormous scalability.

From Sheep Track to Motorway: Supramolecular-Mediated 2D Nanofluidic Channels for Ultrafast Water Transport

Atomic thick 2D materials hold great potential as building blocks to construct highly permeable membranes, yet the permeability of laminar 2D material membranes is still limited by their irregularity sheep track-like interlayer channels. Herein, a supramolecular-mediated strategy to induce the regular assembly of high-throughput 2D nanofluidic channels based on host-guest interactions is proposed. Inspired by the characteristics of motorways, supramolecular-mediated ultrathin 2D membranes with broad and continuous regular water transport channels are successfully constructed using graphene oxide (GO) as an example. The prepared membrane achieves an ultrahigh water permeability (369.94 LMH bar-1) more than six times higher than that of the original membranes while maintaining dye rejection above 98.5%, which outperforms the reported 2D membranes. Characterization and simulation results show that the introduction of hyaluronate-grafted β-cyclodextrin not only expands the interlayer channels of GO membranes but also enables the membranes to operate stably under harsh conditions with the help of host-guest interactions. This universal supramolecular assembly strategy provides new opportunities for the preparation of 2D membranes with high separation performance and reliable and stable nanofluidic channels.

Simultaneous Regulation of Surface Properties and Microstructure of Graphene Oxide Membranes for Enhanced Nanofiltration Performance

The surface properties and microstructure of graphene oxide (GO)-based membranes are both crucial for enhanced nanofiltration performance. Herein, a GO nanofiltration membrane is fabricated with regulatable surface properties and microstructure via a facile two-step impregnation in KOH and following HCl aqueous solutions. The type and number of oxygen-containing groups in GO membranes change with fewer C-O-C/C-OH and C═O but more COOH groups, and they are readily regulated by alkaline treatment time, which enables enhanced surface hydrophilicity and larger surface ζ potentials. Meanwhile, a few tiny defects are present in the GO sheets, which could increase the number of pores and decrease the length of water nanochannels. Such surface properties and microstructure together determine the excellent nanofiltration performance of the GO membranes with fast and selective water permeation, e.g., ∼99.5% rejection toward CBB G250 and flux of 56.9 ± 1.0 L m-2 h-1. This work provides insights into the design of high-performance two-dimensional laminar membranes.

A critical review on graphene oxide membrane for industrial wastewater treatment

An important way to promote the environmental industry's goal of carbon reduction is to promote the recycling of resources. Membrane separation technology has unique advantages in resource recovery and advanced treatment of industrial wastewater. However, the great promise of traditional organic membrane is hampered by challenges associated with organic solvent tolerance, lack of oxidation resistance, and serious membrane fouling control. Moreover, the high concentrations of organic matter and inorganic salts in the membrane filtration concentrate also hinder the wider application of the membrane separation technology. The emerging cost-effective graphene oxide (GO)-based membrane with excellent resistance to organic solvents and oxidants, more hydrophilicity, lower membrane fouling, better separation performance has been expected to contribute more in industrial wastewater treatment. Herein, we provide comprehensive insights into the preparation and characteristic of GO membranes, as well as current research status and problems related to its future application in industrial wastewater treatment. Finally, concluding remarks and future perspectives have been deduced and recommended for the GO membrane separation technology application for industrial wastewater treatment, which leads to realizing sustainable wastewater recycling and a nearly "zero discharge" water treatment process.

Application of polysaccharide-based metal organic framework membranes in separation science

Polysaccharide/MOF composite membranes have captured the interests of many researchers during decontamination of polluted environments. Their popularity can be attributed to the relatively high chemical and thermal stabilities of these composite membranes. Chitosan is among the polysaccharides extensively used during the synthesis of hybrid membranes with MOFs. The applications of chitosan/MOF composite membranes in separation science are explored in detail in this paper. Researchers have also synthesised mixed matrix membranes of MOFs with cellulose and cyclodextrin that have proved to be effective during separation of a variety of materials. The uses of cellulose/MOF and cyclodextrin/MOF membranes for the removal of environmental pollutants are discussed in this review. In addition, the challenges associated with the use of these mixed matrix membranes are explored in this current paper.

Conferring doorman characteristic and superior nano-scratch stability to graphene oxide membranes via tailoring channel microenvironment

Graphene oxide (GO) membranes with doorman characteristic, tunable nanochannel microenvironment and high interfacial adhesion were fabricated.

Recent Developments in Nanoporous Graphene Membranes for Organic Solvent Nanofiltration: A Short Review

Graphene-based membranes are promising candidates for efficient organic solvent nanofiltration (OSN) processes because of their unique structural characteristics, such as mechanical/chemical stability and precise molecular sieving. Recently, to improve organic solvent permeance and selectivity, nanopores have been fabricated on graphene planes via chemical and physical methods. The nanopores serve as an additional channel for facilitating ultrafast solvent permeation while filtering organic molecules by size exclusion. This review summarizes the recent developments in nanoporous graphene (NG)-based membranes for OSN applications. The membranes are categorized depending on the membrane structure: single-layer NG, multilayer NG, and graphene-based composite membranes hybridized with other porous materials. Techniques for nanopore generation on graphene, as well as the challenges faced and the perspectives required for the commercialization of NG membranes, are also discussed.