GO Membrane Research Articles

Polyethylenimine-assisted preparation of Zr-MOF/GO membranes for radionuclide separation

In this study, a zirconium-metal organic framework/graphene oxide (UiO-66-NH2/GO) nanofiltration membrane has been prepared with the assistance of branched polyethyleneimine (PEI). This PEI-assisted method facilitates a more uniform dispersion of UiO-66-NH2 within the GO membrane, thereby enhancing the structural stability of the membrane during membrane separation. The as-prepared membrane has exhibited excellent performance in removing radioactive strontium ions, which is a trending research field in nuclear wastewater treatment. A comprehensive investigation into the separation mechanism of the PEI-UiO-66-NH2/GO membrane has revealed a synergistic effect involving size exclusion and electrostatic repulsion. Furthermore, the PEI-UiO-66-NH2/GO membrane has consistently achieved high strontium rejection across a wide range of strontium concentrations, pH levels, and even in the presence of other interfering ions. More significantly, the membrane has demonstrated remarkably enhanced capacity for selectively separating binary mixtures of cesium and strontium, offering practical relevance. Our results have indicated that the PEI-UiO-66-NH2/GO membrane holds considerable promise for the separation of strontium ions.

Fabrication of polydopamine/graphene oxide composite membranes for effective radionuclide removal

As the energy consumption surges in the past few decades, the utilization of reliable and cost-effective energy resources with minimum greenhouse gas emission is highly desirable, for which nuclear energy has gained intensive attention. The proper treatment of radioactive process water yet remains challenging, but is of vital importance due to its significant threats to environment and public health. In this work, a polydopamine/graphene oxide (PDA/GO) membrane was developed for radionuclide-contaminated water treatment. By the incorporation of PDA, the interlayer spacing of the GO membrane is regulated, as well as an improved anti-swelling property is achieved. At optimal preparation conditions, the PDA/GO has exhibited a high rejection of 99.9 % towards thorium ions with a satisfying water flux of 5.0 L·m−2h−1. Moreover, the influence of solution pH and thorium concentration on the membrane separation performance is studied. Results have indicated that the PDA/GO membrane presents a new promise for the treatment of radionuclide-contaminated water.

Novel strategy to enhance water flux and stability of low swelling GO/NaY/Nylon membrane to adsorb ciprofloxacin from water

To improve the water flux and stability of GO membrane, GO/NaY/Nylon membrane was prepared, in which zeolite were used to increase the layer spacing of GO nanosheets. And the interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) was employed to improve the stability of membrane. The GO/NaY/Nylon membrane with high content of nanoparticles was first used for antibiotic adsorption. The static thermodynamics, kinetics and isotherm for ciprofloxacin (CIP) were studied. The adsorption mechanism on CIP is chemisorption, conforming to the pseudo-second-order model and Langmuir model, and as the equilibrium concentration (ce) increases, the maximum adsorption capacity of GO/NaY/Nylon membrane first increases rapidly, then reaches a plateau, with a maximum adsorption capacity of 49.2 mg·g−1 at 328 K (ce:45.1 mg·L-1). The GO/NaY/Nylon membrane showed higher water flux and stability than the GO membranes, indicating great promising in removing CIP from aqueous solution.

Tuning the interlayer spacing of graphene oxide membrane via surfactant intercalation for ultrafast nanofiltration

A facile method has been developed to fabricate lamellar composite graphene oxide (CGO) membranes by incorporating positively charged surfactants – cetyltrimethylammonium bromide (CTAB). The interlayer spacing of GO nanosheets was regulated by the sum of both vertical and horizontal alignment of CTAB on the GO surface via electrostatic interaction. The CTAB intercalated GO membrane exhibited an internal layer spacing of 16.97 Å compared to 8.26 Å for the GO membrane. The obtained CGO lamellar membrane with well-defined nanochannels showed ultrafast pure water flux of ∼1112 L h−1 m−2 bar−1 and an excellent separation efficiency of >99 % towards negatively charged organic dye molecules at a high permeation flux of ∼932 L h−1 m−2 bar−1, which was nearly 2.5-fold enhancement compared with that of the pristine GO membrane (∼400 L h−1 m−2 bar−1). The electrostatic and π–π interaction forces between the CGO membrane and organic dye molecules played a major role in the overall dye separation mechanism. Furthermore, the CGO membrane demonstrated excellent stability with no loss in separation performance (>96 % organic molecules rejection) after exposure to various pH solutions and deionized water (DI) water. The current work provides a straightforward approach for the formation of highly tunable and stable CTAB-intercalated GO membranes for ultrafast molecular separation.

Multidimensional nanochannel design and regulation of ultra-thin GOQDs-AGQDs composite membranes

Graphene-based composite membranes with long and tortuous transport paths restricted its efficient and wide application in substance separation and purification field. In this study, we propose a multidimensional mass-transfer channel construction method for fabricating highly permeable 2D laminar membranes with lots of stable molecular transport channels. In particular, a robust GOQDs-AGQDs composite membranes with adjustable interlayer sieving channels were prepared based on vacuum assisted self-assembly by intercalating AGQDs with average size of 7.5 nm between GOQDs with average size of 34.0 nm, which presented highly permeability with plentiful nano-channels in both vertical and horizontal directions. As the mass fraction of doped AGQDs reached to 60 wt%, the best performance of GOQDs-AGQDs composite membranes was obtained, with a functional layer thickness of 24.1 nm, good stability, and strong acid and alkali resistance. The usage of small diameter GOQDs with intercalating smaller diameter AGQDs extremely shortened the transfer channel path and slightly increased the interlayer spacing (8.26 to 8.75 Å), which dramatically improved its permeation flux of 14 times higher than that of the pure GO membrane with similar dye rejection, and reached to 133.3 L·m−2·h−1 under 2 bar at the optimized condition. This study provided insights into self-assembling small-sized 2D nanomaterials into membranes and fine-tuning their nanochannel structure.

A synergistic polyelectrolytes-Zr-MOF hydrated construction graphene oxide nanofiltration with enhanced dye wastewater remediation

In recent years, developing an efficient nanofiltration membrane had been a thorny challenge for dye/salt wastewater purification. In this study, a novel graphene oxide-based nanofiltration membrane (GO/UiO@S-GO-8) was constructed by intercalating the synergistic polyelectrolytes-Zr-MOF hydrated construction (UiO@S-GO) into GO nanosheets. Here, combining the hydrophilic high-density anionic sulfonic groups (SO3-) with cationic amino groups (-NH2), GO-based nanofiltration membrane demonstrated outstanding separation ability, anti-pollution performance and structure stability. Compared to pure GO membrane, benefiting by effective expansion of graphene layer spacing from intercalation effect of UiO@S-GO, the water permeance of GO/UiO@S-GO-8 membrane increased to 8 times (about 66.3 ± 1.5 L m−2 h−1 bar−1). Importantly, the permeances of various dyes wastewater also reached up to 65.1 ± 1.8 L m−2 h−1 bar−1 at the high removal rate (exceeding 99.4%). Furthermore, strong hydratability of polyelectrolytes and hard porous crystal constructed the robust anti-fouling micro/nano rough structures onto the membrane surface, which made flux recovery rate (FRR) of GO/UiO@S-GO-8 enhanced to 96.7 ± 1.3%. Remarkably, the salt-resistant behavior of the polyelectrolytes and porous MOF could maintain the stability of the membrane filtration channels, the GO/UiO@S-GO-8 membrane could realize efficient removal rate of dyes (over 98%) faced the complex dye wastewater with different salt concentrations. Meanwhile, the GO/UiO@S-GO-8 membrane also could maintain the high permeance (46.7 ± 1.5 L m−2 h−1 bar−1) as well as excellent removal rate (97.2 ± 1.4%) after 10 cycle experiments. Hence, the GO/UiO@S-GO-8 nanofiltration membrane with Polyelectrolytes-Zr-MOF hydrated construction possessed a broad application inspiration in the purification of high-salt/dye wastewater.

Lamellar structured GO-Melamine nanocomposite membranes with varying d-spacing for efficient organic solvent nanofiltration (OSN)

There is a lot of research being done on GO lamellar 2D membranes for separating organic solvents and dyes. These membranes are highly sought-after due to their exceptional characteristics. However, existing challenges include inadequate solvent permeability and limited dye rejection capacity due to swelling of membranes. In this study, we proposed a novel technique that employs low-pressure assisted filtration to fabricate nanocomposite membranes using GO and melamine. Remarkably, these composite membranes exhibited outstanding separation performance for dyes (≥99.06 %) in organic solvents, regardless of their positive or negative charges or when present in mixtures. The optimum GO-M0.02 nanocomposite membrane exhibits impressive organic solvent flux (J), attaining a value as high as 50.8 L/m2h (acetone), which is 6.57 times greater than that of the pure GO membrane. Furthermore, these GO-Melamine nanocomposite membranes showed excellent durability against both common and harsh organic solvents, and the flux of solvents through the GO-M0.02 nanocomposite membrane remained almost unchanged even after being immersed in methanol for up to one week. Additionally, the membrane exhibited consistent solvent flux and rejection rates for methyl green during continuous filtration. These results highlight the exceptional stability and immense potential of GO-melamine nanocomposite membranes for real organic solvent nanofiltration.

Synergistic contribution of sulfonated poly(ether sulfone) and iminodiacetic acid functionalized-graphene oxide nanosheets towards enhancing cationic dye wastewater purification using nanocomposite membranes

Water purification and wastewater treatment can be achieved using membrane technologies. However, conventional poly(ether sulfone) (PES) membranes suffer from hydrophobicity, fouling issues, and insufficient dye removal. In this study, hydrophilic sulfonated PES (sPES) and iminodiacetic acid-functionalized graphene oxide (IDA-GO) nanosheets were incorporated into the PES membranes to enhance cationic dye removal efficiency. PES/sPES membranes containing 0.05–0.2 wt% IDA-GO nanosheets were fabricated via phase inversion. PES/sPES@IDA-GO membrane and IDA-GO nanosheets were fully characterized using various analytical techniques. With a negative surface charge, the PES/sPES@IDA-GO membrane is a good candidate to remove cationic days. Compared with pristine PES membranes, hydrophilic nanosheets improve membrane porosity, hydrophilicity, and mechanical properties. Further altering the membrane structure by incorporating IDA-GO nanosheets into the PES/sPES-based casting solution increased the porosity and mean pore radius. Using PES/sPES@IDA-GO membrane containing IDA-GO nanosheets as low as 0.1 wt%, values of 99.9 % 19.4 L/m2.h were achieved for dye rejection and pure water flux, respectively. Tuning membrane properties using sPES and IDA-GO nanosheets enabled exceptional cationic dye removal. This offers a facile approach to engineering high-performance PES membranes for effective wastewater purification and environmental remediation applications.

Deciphering the role of 2D graphene oxide nanofillers in polymer membranes for vanadium redox flow batteries

This comprehensive review article explains the influence of various GO and GO-polymer membrane modifications for VRFB, which range from cation and anion exchange to amphoteric and zwitterionic membranes.

Ultrahigh separation property of GO membrane for dissolved organic compound in high-salt brine

The membrane separation technology for the removal of dissolved organic compounds still faces numerous challenges in concentrated salt solution. In this work, the GO/PES membrane was successfully fabricated only adjusting the pH value without any cross-linking agent. The morphology, surface charge distribution, and separation performances were characterized in detail. Results demonstrated the GO/PES membrane exhibited excellent separation performances for tributyl phosphate, sulfonated kerosene and bis(2-ethylhexyl) phosphate with the corresponding flux of 630, 560 and 600 L‧m−2‧h−1, and separation efficiency of 93.1 %, 95.6 % and 96.5 %, respectively, exhibiting both high selectivity and permeability. Meanwhile, the GO/PES membrane exhibited almost 100 % separation efficiency with flux of 1430 L‧m−2‧h−1 for methylene blue solution. Impressively, the GO/PES membrane showed ultrahigh separation efficiency for 200 Da without influences on ions when the salt content was 327 g‧L−1. Furthermore, the GO/PES membrane exhibited robust structural stability and excellent separation performances, which can endure 2000 times folds and corrosion in HCl, NaOH and NaCl for two weeks without separation performances decline. This study highlighted the broad application prospects in the treatment fields of high-salt solution.

Hydrophobic functionalization of graphene oxide film by pulsed hexamethyldisiloxane plasma

Abstract Graphene oxide (GO) membranes show good separation performance in membrane distillation processes, which require at least a single-sided hydrophobic surface to resist liquid penetration, but such hydrophobic GO membrane cannot be facilely prepared by conventional wet chemical processes. Here, a pulsed plasma hexamethyldisiloxane (HMDSO) process was investigated, with the highest surface contact angle of 124° obtained. The results demonstrate that a plasma deposition process can provide a proper route to prepare surface-selective hydrophobic GO films, which facilitates their applications for membrane distillation processes and related fields.

Effect of the electron irradiation on the ion permeation through the GO membrane

Effect of the electron irradiation on the ion permeation through the GO membrane

An efficient composite membrane to improve the performance of PEM reversible fuel cells

In this study innovative composite Nafion/GO membranes are tested at different GO loading (0.5% wt., 1% wt. and 1.5% wt.) in electrolyser and fuel cell mode (Unitized reversible fuel cell). Baseline Nafion membranes were used for comparison.Water uptake (WU), ion exchange capacity (IEC), tensile strength, TGA (thermogravimetric analysis) and SEM (scanning electron microscope) analysis are discussed. The SEM revealed the inclusion of GO into the Nafion matrix while the TGA showed an increased thermal stability of the membrane attributed to the inclusion of the carbon material. Moreover, the addition of GO improves the membrane tensile strength, obtaining a maximum enhancement of nearly 90%, while reducing the elongation ratio (80% for the Nafion and 45% for the 1.5% wt. GO membrane). Water uptake increased when increasing the content of GO due to its hydrophilic nature recording the highest values for the membrane with 1.5%wt. of GO (23% against 10% for the Nafion). An increase of IEC (almost 14%) is noticed when GO content is increased. The beneficial effect of GO on the IEC can be attributed to a non-uniform distribution of GO into the Nafion matrix but needs further investigation.Both fuel cell and electrolyser polarization curves were carried out using MEAs with an active area of 9 cm2 and a thickness of 50 μm. The temperature and the pressure were set to 20 °C and 1 atm respectively. Regarding fuel cell mode, the optimum loading of GO has been found to be 0.5%, registering the highest performance, 13% higher than Nafion. Regarding the electrolyser mode, the GO 0.5% wt. membrane, showed performance comparable to the Nafion. A comparison between Nafion based membranes at higher thicknesses showed that, adopting GO, it is possible to obtained similar performance with a reduced membrane thickness, keeping almost equal the performance and the average round trip efficiency (26.1% for the GO and 26.6% for the Nafion). In commercial applications such characteristics allows to strongly reduce the cost of materials.Durability and stability of the GO/Nafion membrane should be properly investigated in successive studies as such membranes are subjected to a rapid deterioration of their performance.

Catalytic two-dimensional Pd decorated graphene oxide membrane for efficient 4-nitrophenol reduction

Catalytic Pd decorated graphene oxide (Pd/GO) membrane with efficient catalytic activity was developed by in-situ reduction of Pd2+ on GO nanosheets followed by vacuum filtration. A high 4-nitrophenol (4-NP) reduction efficiency was achieved by using the Pd/GO catalytic membrane with layered structure because of evenly distribution of Pd nanoparticles (NPs) in the interlayer space of GO membrane, ensuring sufficient contact between 4-NP molecules and Pd NPs. The apparent kinetic rate constant and turnover frequency (TOF) reached to 138.4 s−1 and 813 h−1 under a continuous-flow system using 4000 mg/L of 4-NP at 20 °C. During a 300 min of continuous-flow catalysis, the 4-NP conversion was kept above 98% at 20 °C. This high catalytic efficiency of the Pd/GO catalytic membrane under high 4-NP concentration and continuous-flow catalysis made it promising and competitive in the application of catalytic membrane for efficient catalytic process.

Tailoring the interlayer channel structure of graphene oxide membrane with conjugated cationic dyes for butanol dehydration

For the design of high-performance GO membrane, the structure of intercalation material is a key consideration due to its decisive impacts on nanosheet assembly and mass transfer channel structure. Herein, conjugated cationic dyes were incorporated into GO interlayer channels. The large π-conjugated structure and delocalized positive charge can form π-π and electrostatic interactions with the non-oxidized region and negatively-charged group on GO nanosheet, respectively. Through interlayer cross-linking, the nanosheet orientation and interlayer bonding can be improved, conferring the membrane with higher anti-swelling capacity, more ordered channel structure, and controllably tailored interlayer d-spacing. The electron cloud density and planar structure of cationic dye molecules are evidenced to be critical in influencing membrane structure and separation performance. After incorporating conjugated cationic dyes, the separation factor for water/butanol separation can reach 5.3 times of that of pristine GO membrane, while the permeate flux also increases by 20%. This work provides a category of promising intercalation materials for GO membranes with good potential application in butanol dehydration.

Chiral gold nanoparticles/graphene oxide membranes with ultrahigh and stable permeance for sieving and enantioseparation

In accurately balancing membrane permeability and separation coefficient, effectively preventing membrane collapse in separation process is the core to improve the efficiency of membrane separation for two-dimensional materials. Here, we used L-cysteine (L-Cys) functionalized gold nanoparticles as scaffolds and spacers and fabricated a multi-effect separation membrane with GO nanosheets. The as-prepared membrane performed the following as a separation membrane: (1) As a robust spacer, the gold nanoparticles, prevented the collapse of the GO sheet and thus the membrane showed stability; (2) The existence of amphiphilic L-cysteine enabled the possibility of regulating the GO sheets layer spacing between 16.9 and 17.8 Å by pH, which achieves controllable ultrahigh permeance for size sieving. The maximum permeation rate of the membrane can reach 216.6 L m−2 h−1 bar−1, which is much greater than that of pure GO membrane; (3) Further, we demonstrate the following properties of the as-prepared membranes embedded with amphiphilic chiral gold nanoparticles for the enantiomer separation. The membrane has high enantioselectivity for Pen racemates, and its chiral separation factor and permeation rate can reach 1.83 and 21.7 L m−2 h−1 bar−1, respectively.

Fundamental Understanding of Ultrathin, Highly Stable Self-Assembled Liquid Crystalline Graphene Oxide Membranes Leading to Precise Molecular Sieving through Non-equilibrium Molecular Dynamics

Self-assembled graphene oxide lyotropic liquid crystal (GO LLC) structures are mostly formed in aqueous medium; however, most GO derivatives are water insoluble, so processing GO LLCs in water poses a practical limitation. The use of polar aprotic solvent (like dimethyl sulfoxide) for the formation of GO LLC structures would be interesting, because it would allow incorporating additives, like photoinitiators or cross-linkers, or blending with polymers that are insoluble in water, which hence would expand its scope. The well-balanced electrostatic interaction between DMSO and GO can promote and stabilize the GO nanosheets' alignment even at lower concentrations. With this in mind, herein we report mechanically robust, chlorine-tolerant, self-assembled nanostructured GO membranes for precise molecular sieving. Small-angle X-ray scattering and polarized optical microscopy confirmed the alignment of the modified GO nanosheets in polar aprotic solvent, and the LLC structure was effectively preserved even after cross-linking under UV light. We found that the modified GO membranes exhibited considerably improved salt rejection for monovalent ions (99%) and water flux (120 LMH) as compared to the shear-aligned GO membrane, which is well supported by forward osmosis simulation studies. Additionally, our simulation studies indicated that water molecules traveled a longer path while permeating through the GO membrane compared to the GO LLC membrane. Consequently, salt ions permeate slowly across the GO LLC membrane, yielding higher salt rejection than the GO membrane. This begins to suggest strong electrostatic repulsion with the salt ions, causing higher salt rejection in the GO LLC membrane. We foresee that the ordered cross-linked GO sheets contributed to excellent mechanical stability under a high-pressure, cross-flow, chlorine environment. Overall, these membranes are easily scalable, exhibit good mechanical stability, and represent a breakthrough for the potential use of polymerized GO LLC membranes in practical water remediation applications.

Graphene-Oxide-Grafted Natural Phosphate Support as a Low-Cost Ceramic Membrane for the Removal of Anionic Dyes from Simulated Textile Effluent

A novel natural phosphate/graphene oxide (GO) composite membrane was successfully fabricated using two steps: (i) silane chemical grafting and (ii) dip-coating of a GO solution. First, the low-cost disk ceramic support used in this work was fabricated out of Moroccan natural phosphate, and its properties were thoroughly characterized. The optimized ceramic support was sintered at 1100 °C following a specific heat treatment based on thermogravimetric analysis (TGA) and differential thermal analysis (DTA); it exhibited a permeability of 953.33 L/h·m2·bar, a porosity of 24.55%, an average pore size of 2.45 μm and a flexural strength of 22.46 MPa. The morphology analysis using SEM showed that the GO layer was homogenously coated on the crack-free Moroccan phosphate support with a thickness of 2.8 μm. The Fourier transform infrared spectrometer (FT-IR) results showed that modification with silane could improve the interfacial adhesion between the GO membrane and the ceramic support. After coating with GO on the surface, the water permeability was reduced to 31.93 L/h·m2·bar (i.e., by a factor of 142). The prepared GO/ceramic composite membrane exhibited good efficiency in the rejection of a toxic azo dye Congo Red (CR) (95.2%) and for a simulated dye effluent (87.6%) under industrial conditions. The multi-cycle filtration tests showed that the rejection rate of CR dye remained almost the same for four cycles. Finally, the flux recovery was also studied. After 1 h of water cleaning, the permeate flux recovered, increased significantly, and then remained stable.

Graphene oxide laminates intercalated with Prussian blue nanocube as a photo-Fenton self-cleaning membrane for enhanced water purification

The separation performance of nano-laminated graphene oxide membranes is heavily decided by their nanoscale structures. Antifouling properties of the membrane have an influence on membrane performance significantly beside tuning 2D GO interlayer spacing. Herein, we intercalated a photo-Fenton catalytic Prussian blue nanocubic into graphene oxide laminates to fabricate a GO/PB membrane through a simple vacuum filtration process, the 2D nano-channel was characterized and simulated by SEM and Molecular dynamics (MD) simulations. The PB nanocubic can not only serve as nano pacers to prevent the restacking of GO nanosheets and adjust 2D nanochannels, but endow the membrane with photo-Fenton self-cleaning function. As a consequence, the GO/PB membrane presents a high separation efficiency (∼100% dye rejection), and the water permeability is nearly 2 times higher than that of the pristine GO membrane under synergistic separation and photo-Fenton self-cleaning processes. Scavenging experiments and characterization results indicated the active species of h+ and ·OH play a major role in the degradation process. In addition, the GO/PB membrane exhibited outstanding antifouling performance and reusability, retaining high dye removal efficiency (>95%) and high water-permeability (∼132.7 Lm−2h−1bar−1) after three separation cycles with photo-Fenton treatment in each cycle. Moreover, full-scale zebrafish toxicology assays have indicated that the dye stock solution exerted significant toxic effects on zebrafish with increased mortality and malformations compared to the control, while the filtrate induced negligible toxic effects. Overall, this work reveals the dual roles of PB as nanospacers and photo-Fenton catalytic nano-filler, providing a new concept for the development of hybrid nanolaminated membranes for water purification and textile wastewater treatment.

Fabrication of cross-linked highly stable graphene oxide membrane for dye removal

ABSTRACT Clean water is essential to our health, community and economy, but also its availability remains a major challenge even today. Graphene oxide membranes have shown significant promise in addressing this problem. A great deal of research has been conducted and is still being done to produce a stable graphene oxide membrane with high permeability and rejection rate. In this study, a highly stable GO membrane was fabricated using a simple vacuum filtration technique by the addition of TRIS and PEG. This is the first paper to discuss the potential for this combination to remove dyes and how it can result in the formation of a stable membrane. The membranes were characterised in detail using various characterisation techniques such as XRD, XPS, AFM, etc., and their ability in dye removal was investigated using UV–Vis spectroscopy. The stability of the developed membranes was tested using ultrasonication, and it was found that the membranes could remove the organic dyes (MB and CR) even at high concentration of dye (20 ppm) and with rejection percentage of 95% for both dyes. Furthermore, the membranes showed good water permeability with a value of 183 Lm−2h−1bar −1 emphasising its high potential for water purification.