Graphene oxide based membranes for selective ion/molecule transport in water.

Sorption and diffusion selectivity of water-ethanol transport in graphene oxide membranes

The presence of micropollutants, such as pharmaceuticals, in aquatic environments is a major concern due to the risks they pose to living organisms. Given the often inadequate management of wastewater, it is crucial to develop reliable and effective methods to eliminate these contaminants, thus ensuring our safety and protecting the ecosystem. This study aims to test the ability of a polyvinyl chloride/graphene oxide (PVC/GO) composite membrane to adsorb metformin (Met) in an aqueous solution. The graphene oxide was synthesized using the Hummers method from recycled graphite obtained from drilling molds, thereby adding an ecological dimension to this research. This graphene oxide was then used to prepare PVC/GO. The resulting materials were characterized using Fourier-transform infrared spectroscopy, thermogravimetric analysis and Brunauer–Emmett–Teller analysis. The following adsorption parameters were investigated: pH (2–8), temperature (25–40 °C), time (5–30 min), GO content in PVC/GO (0–15%) and initial concentration (4, 6, 8, and 10 mg/L). Adsorption experiments revealed that 75% removal of Met was achieved within 15 min at an optimum concentration of 4 mg/L. Maximum adsorption efficiency of Met was obtained at 40 °C in an acidic medium (pH 2); however, adsorption decreased as the pH increased. Thermodynamic studies indicated that Met adsorption was spontaneous (∆ G ° < 0) and exothermic (∆ H ° < 0) at 25, 30, and 35 °C. However, the process was endothermic and non-spontaneous at 40 °C. Based on the obtained results, PVC/GO 5% was found to be an efficient and promising adsorbent for Met.

Advanced energy-efficient separation methods are becoming increasingly necessary due to industrial emissions, urban runoff pollution, and global water scarcity. In order to overcome the drawbacks of traditional polymeric membranes, such as fouling, limited selectivity, and chlorine sensitivity, graphene oxide (GO) membranes—which are made up of stacked, oxygen-functionalized two-dimensional carbon sheets—offer a remarkable combination of sub-nanometer sieving, ultrafast water transport, and versatile adsorption chemistry. In this review, GO membranes are critically assessed in practical water applications, such as drinking water treatment, industrial effluents (based on pilot-scale textile dyehouse and oilfield research), municipal wastewater, and stormwater. Applications and performance metrics in real water matrices, including dye, PFAS, and metal ions removal, are discussed in detail, along with challenges like scalability, fouling, structural stability, regulatory compliance, and environmental health considerations. The GO structural and chemical properties that are pertinent to membrane performance, fabrication strategies, and bench-scale performance of GO modified surfaces were also discussed in this review article. Practical suggestions are offered in the conclusion section, highlighting the need for extensive safety testing and multi-month pilot studies to hasten the transition of GO membranes from lab experiments to functional water treatment systems.

Graphene Oxide Membranes and Membrane Cascades for Lignin Separation and Fractionation from Biorefinery Streams

Graphene oxide (GO) membranes have emerged as promising candidates for water desalination as a result of their structural and transport properties. In this study, we employ fully atomistic classical molecular dynamics simulations to investigate the performance of monolayer GO membranes featuring pore- and slit-like nanostructures. We analyze the influence of the width of the slits, ranging from 0.8 to 1.5nm, on water transport and salt rejection by monitoring the spatial and temporal distributions of water molecules and ions. Furthermore, we assess the effect of applied pressure on water density profiles and compute the potential of mean force for water molecules traversing the slits. Our results reveal that slits offer tunable transport characteristics and that nanopores generally outperform slits in the combined metrics of water flux and ion exclusion at low pressures. At higher pressures, however, 1.0-1.5nm slits exhibit a permeability gain that can exceed comparable nanopore systems, with a reduction in salt rejection, whereas 0.8nm slits retain near-complete ion exclusion over the range examined. These findings delineate operating regimes in which each architecture is advantageous and guide the optimization of nanostructure design for advanced desalination technologies.

Manufacturing and Improving Reduced Graphene Oxide (rGO) Membranes for Use as Highly Sensitive Humidity Sensors Based on the Mechanism of Proton Conductivity

Sodium carboxymethyl cellulose intercalated graphene oxide membranes for efficient and selective separation of cationic dyes

Layer-by-layer polyvinyl alcohol intercalated graphene oxide membrane with sodium alginate for ethanol dehydration via pervaporation

With many studies reporting high water flux and strong solute rejection, graphene oxide membranes (GOMs) show clear potential. Motivated by these findings, we establish a standard operating protocol (SOP) for the reliable and reproducible evaluation of GOM performance. Our procedure begins with permeability measurements of a blank large-pore polymer template, followed by incremental GO deposition to track performance changes. We found that the polymer template, even with only half-coverage of GO, showed a significant drop in water flux. We identify a minimum GO thickness of approximately 140 nm on the polymer template with 47 mm diameter is necessary to achieve complete GO coverage and ensure reliable membrane performance with a water flux of ~100 LMH bar −1 and dye removal of ~70 %. Similar behaviors are also observed in the hollow fibre (HF) membrane system, indicating the importance of such practices in industrial applications. Together, these results provide a reliable procedure for benchmarking GOMs and for guiding their translation from laboratory studies to industrial operation. Recent reports on very high-water flux and high rejection rates for graphene oxide membranes (GOMs) prompted us to develop good practices for performance measurements. Our systematic study shows that incomplete GO coverage on the substrate can result in overestimated or erroneous water flux values, suggesting the importance of standard work procedures (SOP) for GOM performance evaluations. • Incomplete GO coverage on the substrate results in overestimated water flux values. • GO thickness ~140 nm on flat and hollow-fibre polymer template ensures complete coverage. • 140 nm GO coating provides reliable water flux ~100 LMH/bar and dye removal ~70 %.

Optimization of interlayer spacing and pore structure in multilayer graphene oxide membranes via pressure-driven molecular dynamics simulations

Toward scalable diffusio-osmotic power generation with Pt-decorated reduced graphene oxide membranes

Influence of Pd nanoparticles on the structural stability and hydrogen separation of graphene oxide membranes

Graphene oxide (GO) is a promising nanomaterial for membrane-based desalination due to its tunable interlayer structure and abundant surface functionalities. This study synthesized and characterized a graphene oxide titanium dioxide (GO–TiO₂) composite membrane via vacuum-assisted filtration to enhance seawater desalination performance. Characterization using XRD, FTIR, SEM, and contact angle analysis confirmed uniform TiO₂ incorporation, which expanded GO interlayer spacing from 0.77 nm to 0.90 nm, increased hydrophilicity, and improved structural stability. Forward osmosis (FO) tests using 3.5 wt% NaCl feed solution showed that the GO–TiO₂ membrane achieved over 99% salt rejection and a 125% increase in water flux compared to pristine GO membranes. TiO₂ acted as a nano-spacer and hydrophilic agent, reducing GO restacking and facilitating water transport. These results indicate that the GO–TiO₂ composite membrane offers enhanced permeability, selectivity, and durability, making it a promising candidate for sustainable seawater desalination.

This study reports the fabrication and characterization of aluminum-functionalized graphene oxide (GO–Al) composite membranes for solid polymer electrolyte applications. The aim of this work is to investigate how aluminum functionalization modifies the interlayer structure of graphene oxide membranes and influences ion transport behavior. Graphene oxide was synthesized via the Tour method and functionalized with Al³⁺ ions derived from AlCl₃ at different loadings of 3.52, 14.68, and 25.93 wt%. Intercalation of trivalent aluminum ions induced an expansion of the GO interlayer spacing from 0.8125 to 0.8278 nm and promoted the conversion of epoxy (C–O–C) groups into hydroxyl (C–OH) and carboxyl (C–OOH) groups through the formation of stable Al–O–C coordination bonds. These structural modifications enhanced membrane hydrophilicity, structural stability, and ion transport capability. Raman spectroscopy revealed increased structural disorder, while thermogravimetric analysis indicated improved thermal stability with reduced total weight loss. Electrochemical impedance spectroscopy demonstrated a significant enhancement in ionic conductivity from 0.282 to 0.553 S·m⁻¹, attributed to Grotthuss-type ion hopping through hydrated transport pathways. Among the investigated compositions, the GO–Al 25.93% membrane exhibited the most favorable balance between interlayer expansion, defect structure, and ionic transport performance, highlighting its potential as a solid polymer electrolyte.

Membrane‐based enantioselective separation offers various advantages, making it a promising method for chiral separation. However, its realistic application remains a challenge due to limitations in current separation performance. Here, we propose a new type of chiral graphene oxide membrane that exhibits a tyrosine racemates separation factor up to 20.1, as well as a preferential enantiomer flux of 4.5 mmol m −2 h −1 , superior to those of the most advanced membranes. Moreover, the chiral sieving application of this graphene oxide membrane is extended to four different chiral amino acids representing two distinct classes. These abundant oxygen‐containing groups in the graphene oxide membrane allow the extensive functionalization of chiral amino acids. Theoretical analyses reveal the significant interaction differences between the functionalized‐graphene oxide sheets and D‐ or L‐chiral amino acids, maintaining the remarkable chiral separation performance of this graphene oxide membrane. Besides, the novel fast protein liquid chromatography‐compatible column was further developed via stacking these chiral graphene oxide membranes, facilitating more efficient, lower operational requirement, and cost‐effective enantioselective separation, a capability that other reported high‐performance liquid chromatography‐compatible‐only materials lack. Therefore, this study not only highlights the superior performance of the specifically designed graphene oxide membrane for chiral amino acid separations but also provides an accessible, cost‐effective, and highly efficient approach for chiral separation.

Graphene oxide (GO), with its unique two-dimensional structure, adjustable functional groups, and tunable nanofluidic channels, has emerged as a promising platform for bio-inspired neuromorphic computing. This perspective explores the structural and functional analogies between GO membranes and biological ion channels, emphasizing GO’s ability to support selective ion transport, stimuli-responsive behavior, and synaptic plasticity. Recent advances in material engineering and device integration have enabled GO-based artificial synapses, including memristors and ion-gated transistors, to emulate key neuronal features such as excitatory postsynaptic currents, paired-pulse facilitation, and spike-timing-dependent plasticity with sub-millisecond response times and picojoule-level energy consumption. Moreover, the incorporation of GO with polymers, quantum dots, and semiconductors has facilitated multimodal control via electric, optical, and chemical inputs. Together, these developments position GO as a powerful material system for future neuromorphic devices that operate in aqueous and dynamic biological environments, paving the way toward brain-inspired hardware, neuroprosthetics, and intelligent biointerfaces.

Interplay of charge composition and nanochannel confinement in ion separation through graphene oxide membranes.

Graphene oxide membranes (GOMs) are a promising material for next-generation membrane technologies. However, the mechanisms underlying their ion transport remain unclear, limiting the ability to optimise their design for specific applications. In this study, we systematically quantify ion transport by calculating the individual ion diffusion coefficients of GOMs equilibrated in LiCl, NaCl, KCl, and MgCl 2 and binary mixtures of the monovalent salts across varied external salt concentrations. We demonstrate that counter-ion diffusion coefficients generally remain unaffected by external salt concentration, while chloride co-ion diffusion coefficients increase with concentration up to ∼0.3 M before plateauing, primarily influenced by electrostatic interactions between the membrane fixed charge groups and ions, rather than membrane water content. Interestingly, the diffusion coefficients of Na + and Cl - ions in the GOMs are comparable to those in polymeric membranes, challenging previous reports of significantly enhanced ion transport in GOMs. Rather, our analysis reveals that ion permeability in GOMs is predominantly dictated by solubility effects rather than diffusion. In monovalent binary salt systems, counter-ion diffusion coefficients were generally lower than those of single-salt systems, while chloride diffusion coefficients remained comparable, reflecting the influence of ion interactions and membrane hydration on ion transport. We also find that the water permeability of the GOMs is low and does not show the promise of ultrafast water transport identified in early studies. • Ion diffusion coefficients determined through sorption, conductivity and permeation experiments • Counterion diffusivity independent of external salt concentration • Chloride co-ion diffusivity varies with water uptake and external salt concentration • Ion diffusivities are comparable to those in polymeric membranes • Counter-ion diffusivity lower in a binary salt mixture than in the equivalent single salt solution

Mechanistic insights into toxic metal adsorption in multicomponent systems using graphene oxide membranes: kinetic, equilibrium, and reuse studies