Highly Efficient Arginine Intercalated Graphene Oxide Composite Membranes for Water Desalination

Eco-friendly kappa-carrageenan-nano zerovalent iron hydrogel water and wastewater purification

Sustainable water management is crucial for reducing environmental impact, improving public health, and contributing to the United Nations' Sustainable Development Goals (SDGs). This study introduces a novel hydrogel composite membrane for wastewater treatment and desalination. The membrane was fabricated by cross-linking kappa-carrageenan (κC) with nano-zerovalent iron (nZVI) using polyethyleneimine (PEI) to produce a porous structure hydrogel membrane of high water flux and contaminant rejection via adsorption and reduction processes, leveraging the properties of kappa carrageenan and nZVI. Experiments showed an increased water flux and rejection rate for the hydrogel membrane by increasing the pressure from 10 psi to 30 psi. In initial tests with 2 g/L of NaCl or MgSO4, the membrane exhibited 98 % rejection of divalent Mg2 + ions and 90 % rejection of Na+ ions at 30 psi and 17.98 L/M2H water flux. The hydrogel's contaminant separation mechanisms involve a combination of size exclusion, electrostatic repulsion, and hydrophilic-hydrophobic polarity rejection. Leachate wastewater treatment by the membrane achieved 11 L/m2h water flux at 30 psi and an outstanding rejection rate of more than 98 % for divalent ions, such as Li+, Pb2+, Cd2+, Co2+, and Cu2+, and 61 % rejection of organic matter of 165.68 mg/L initial concentration. Due to membrane fouling, the water flux decreased in the second and third filtration cycles, while membrane rejection remained unchanged. The dead-end filtration mode facilitated metal ions recovery at the end of the experiments, recording 68.32 % and 66.31 % recovery for lead and lithium ions. This novel hydrogel provides a promising and sustainable solution for water purification and valuable heavy metals recovery from solutions to support the circular economy.

Efficient separation of Mg2+/Li+ using reduced GO membranes modified by positively charged arginine

Nanofiltration has emerged as an effective technique for the selective separation of mono- and divalent ions, such as Mg2+/Li+ mixtures, and plays a crucial role in lithium extraction from salt lakes. In this study, a graphene oxide (GO) membrane with positively charged channels was prepared by crosslinking arginine (Arg) onto GO nanosheets, followed by vacuum filtration to form the membrane, and then thermal reduction (Arg-rGO). The Arg-rGO membrane exhibits high performance in the ion separation of a typical brine with a Mg2+/Li+ mass ratio of 20. The separation factor (S Li/Mg) reached up to 45.6-two times the highest separation factor reported-while maintaining an advanced water permeance of 21.3 L m-2 h-1 bar-1. Furthermore, the Mg2+/Li+ mass ratio was reduced from 20 to 0.2 after two-stage crossflow filtration with high flux under high pressure. The observed separation performance can be attributed to the synergistic effect of electrostatic repulsion and size-exclusion. These findings confirmed efficient separation of Mg2+/Li+ using GO membranes, demonstrating potential for practical application in lithium extraction from salt lakes.

Chitosan-blended membranes for heavy metal removal from aqueous systems: A review of synthesis, separation mechanism, and performance

The environmental pollution caused by heavy metal ions has become a serious global environmental issue. Heavy metal contaminants released from industrial effluents, agricultural runoff, and human activities, can enter into water resources. The toxicity of these heavy metal ions even at trace concentrations presents a substantial hazard to both aquatic systems and human well-being. The membrane separation processes have become more promising sustainable techniques for the separation of metal ions from the effluent. The research efforts have been concentrated on improving the synthesis of membranes and membrane materials to facilitate the sustainable separation of heavy metals. The application of chitosan in the fabrication of membranes is getting more attention. Chitosan, a natural polysaccharide derived from chitin, is abundant in nature and has active hydroxyl and amino groups suitable for the separation of heavy metal ions. It exhibits excellent chelating tendency, biocompatibility, and biodegradability. The functionalization of chitosan to improve its mechanical strength, chemical stability, and antifouling properties has become an ongoing area of research. This review examines the synthesis and efficient applications of chitosan blended membranes. The review concludes by outlining the current challenges and proposing future research prospects to enhance the applicability of chitosan-blended membranes in environmental remediation.

Construction of Ion-Imprinted Graphene Oxide Mixed-Matrix Membranes for Selective Adsorption and Separation of Tm3

Efficient adsorption and separation of rare earth from other similar rare earth wastewater has become an urgent demand for resource utilization of ion-type rare earth minerals in China. Herein, thulium (Tm) ion-imprinted graphene oxide (GO)-doped polyether sulfone (PES) membranes (GO-TII/PES-2 membranes) were prepared, in which ion-imprinted graphene oxide was applied as an efficient Tm3+ ionic ligand in the imprinted layer and polyether sulfone was applied as a carrier in the membrane matrix to achieve the selective adsorption and separation of Tm3+ and neighboring rare earth ions. Combined with an ion rectifier, the separation and purification performances of Tm3+ were explored. The separation factors β(Tm3+/Tb3+), β(Tm3+/Sm3+), β(Tm3+/Nd3+), and β(Tm3+/Ce3+) in the dynamic adsorption process increased significantly from 1.22, 1.04, 1.04, and 1.02 for nonimprinting to 3.07, 3.91, 3.91, and 3.33 for imprinted membranes. The GO-TII/PES-2 membrane adsorbed about three times more Tm3+ than the nonionic-imprinted (GO-NII/PES) membrane by adding a color developer and quantifying Tm3+ based on a fast and easy UV-photometric method. After eight dynamic permeations, the adsorption of Tm3+ by the GO-TII/PES-2 membrane decreased by only 13%, indicating that the membrane has good reuse performance. Additionally, the investigation examined the influence of Tm3+ on wheat seed germination, underscoring its potential application in agriculture and the importance of adsorbing and separating rare earth ions.

Ultrahydrophilic Inorganic Nanosheet-Based Nanofiltration Membranes for High Efficiency Separations of Inorganic Salts and Organic Dyes

Two-dimensional (2D) inorganic nanomaterials have garnered extensive attention in the fabrication of inorganic nanofiltration membranes due to their unique structures and properties. In this study, we developed a facile process for fabricating large-scale ultrahydrophilic nanofiltration membranes using layered titanate H1.07Ti1.73O4·nH2O nanosheets (HT-ns). A drying deposition process was used to fabricate HT-ns membranes on a poly(tetrafluoroethylene) (TF) substrate. To enhance the bonding strength between the substrate and the deposited HT-ns membrane, the substrate surface was modified with a Cu2+-adsorbed silane monomolecular layer, connecting a negatively charged HT-ns membrane and a positively charged substrate surface. The fabricated HT-ns membrane exhibited an excellent rejection performance for inorganic salts and dye molecules. The ultrahydrophilicity of HT-ns membrane with a low water contact angle of 31° results in an ultrafast water permeance, which is approximately 6 times higher than that of a simple graphene-based nanofiltration membrane. The results open a new avenue to a new category of ultrahydrophilic nanofiltration membranes.

Shear-aligned graphene oxide nanosheets incorporated PVDF composite membranes for selective dye rejection with high water flux

Membrane technology is crucial in addressing water pollution challenges, particularly in removing dyes from wastewater. This study presents a novel approach to fabricating shear-aligned graphene oxide (GO) nanosheets incorporated polyvinylidene fluoride (PVDF) membranes for achieving exceptional dye rejection efficiency while maintaining high water flux. The membranes were prepared by dispersing graphene oxide within a PVDF matrix and subsequent subjection to shear alignment techniques. Shear and flow-induced alignment were explored to achieve precise and controlled alignment of graphene oxide flakes within the PVDF matrix. The resulting membranes exhibited enhanced structural integrity and optimized molecular packing of PVDF and GO, enabling them to selectively reject dyes while allowing efficient water permeation. The fabricated membranes were extensively characterized using appropriate testing methods. The results demonstrated that the shear-aligned GO sheets infused PVDF composite membranes exhibited outstanding dye rejection (96-99%) performance, surpassing conventional membranes while maintaining high water flux. This innovative membrane fabrication approach holds significant promise for advanced water treatment applications, offering a sustainable solution for selective dye removal and efficient water purification.

Membranes Based on Aminated Graphene Oxide with High Selectivity Toward Organic Substances

In this work, membranes based on graphene oxide, modified with oleylamine, have been prepared by a simple wet chemistry protocol without the use of complex equipment, elevated temperature, and additional reagents. The membrane material was characterized by a set of physicochemical methods: thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffractometry, and X-ray photoelectron spectroscopy. The prepared membranes are stable in both aqueous and organic media. The membranes have a high flux for organic substances and do not permeate water at room temperature and atmospheric pressure. The selectivity of the membranes toward organic substances increases with their thickness. The highest flux among the tested organic liquids is registered for methanol. The membranes have high selectivity toward ethanol/1-butanol and acetone/1-butanol pairs, which opens up the possibility of separating actual industrial mixtures. The membrane retains 90% of methylene blue from the alcohol solution. Our work expands the possibilities of using modified GO-based membranes in purification and filtration technologies.

Two-Dimensional MXene-Based Electrocatalysts: Challenges and Opportunities

MXene, regarded as cutting-edge two-dimensional (2D) materials, have been widely explored in various applications due to their remarkable flexibility, high specific surface area, good mechanical strength, and interesting electrical conductivity. Recently, 2D MXene has served as a ideal platform for the design and development of electrocatalysts with high activity, selectivity, and stability. This review article provides a detailed description of the structural engineering of MXene-based electrocatalysts and summarizes the uses of 2D MXene in hydrogen evolution reactions, nitrogen reduction reactions, oxygen evolution reactions, oxygen reduction reactions, and methanol/ethanol oxidation. Then, key issues and prospects for 2D MXene as a next-generation platform in fundamental research and real-world electrocatalysis applications are discussed. Emphasis will be given to material design and enhancement techniques. Finally, future research directions are suggested to improve the efficiency of MXene-based electrocatalysts.

Highly efficient mica-incorporated graphene oxide-based membranes for water purification and desalination

Graphene oxide (GO) has become the most attractive material for membrane technology owing to its potential application as a nanofiller in water treatment, purification, and desalination. In this study, we incorporated mica as a cross-linking reagent to increase the interlayer spacing and stability of GO sheets and fabricated a mica/GO (MGO) membrane for the first time. The MGO membrane (260 ± 10 nm) exhibits 100% rejection for biomolecules such as tannic acid (TA) and bovine serum albumin (BSA) and >99% rejection for multiple probe molecules, such as methylene blue, methyl orange, congo red, and rhodamine B. The high rejection of membranes can be attributed to the surface interaction of mica with GO nanosheets through covalent interaction, which enhances the stability and separation efficiency of the membranes for probe ions and molecules. This ultrathin MGO membrane also exhibits much better water permeability at 870 ± 5 L m-2 h-1 bar-1, which is 10-100 times greater than that reported for pure GO and GO-based composite membranes. Additionally, the membrane shows high rejection for salt ions (70%). Furthermore, the stability of the MGO membranes was evaluated under various conditions, and the membranes demonstrated remarkable stability for up to 60 days in a neutral environment.

Nanodiamonds: A Cutting-Edge Approach to Enhancing Biomedical Therapies and Diagnostics in Biosensing

Nanodiamonds (NDs) have garnered attention in the field of nanomedicine due to their unique properties. This review offers a comprehensive overview of NDs synthesis methods, properties, and their uses in biomedical applications. Various synthesis techniques, such as detonation, high-pressure, high-temperature, and chemical vapor deposition, offer distinct advantages in tailoring NDs' size, shape, and surface properties. Surface modification methods further enhance NDs' biocompatibility and enable the attachment of bioactive molecules, expanding their applicability in biological systems. NDs serve as promising nanocarriers for drug delivery, showcasing biocompatibility and the ability to encapsulate therapeutic agents for targeted delivery. Additionally, NDs demonstrate potential in cancer treatment through hyperthermic therapy and vaccine enhancement for improved immune responses. Functionalization of NDs facilitates their utilization in biosensors for sensitive biomolecule detection, aiding in precise diagnostics and rapid detection of infectious diseases. This review underscores the multifaceted role of NDs in advancing biomedical applications. By synthesizing NDs through various methods and modifying their surfaces, researchers can tailor their properties for specific biomedical needs. The ability of NDs to serve as efficient drug delivery vehicles holds promise for targeted therapy, while their applications in hyperthermic therapy and vaccine enhancement offer innovative approaches to cancer treatment and immunization. Furthermore, the integration of NDs into biosensors enhances diagnostic capabilities, enabling rapid and sensitive detection of biomolecules and infectious diseases. Overall, the diverse functionalities of NDs underscore their potential as valuable tools in nanomedicine, paving the way for advancements in healthcare and biotechnology.