Size-controlled graphene oxide for highly permeable and fouling-resistant outer-selective hollow fiber thin-film composite membranes for forward osmosis

Spinel ferrite nanoparticles as potential materials in chlorophenol removal from wastewater

Persistent organic pollutants (POPs) including chlorophenols (CPs) are increasing in water effluents, creating serious problems for both aquatic and terrestrial lives. Several research attempts have considered the removal of CPs by functionalised nanomaterials as adsorbents and catalysts. Besides the unique crystal structure, spinel ferrite nanomaterials (SFNs) own interesting optical and magnetic properties that give them the potential to be utilised in the removal of different types of CPs. In this review, we highlighted the recent research work that focused on the application of SFNs in the removal of different CP substances based on the number of chlorine atom attached to the phenolic compound. We have also discussed the structure and properties of SFN along with their numerous characterisation tools. We demonstrated the importance of identifying the structure, surface area, porosity, optical properties, etc. in the efficiency of the SFN during the CP removal process. The reviewed research efforts applied photocatalysis, wet peroxide oxidation (WPO), persulfate activated oxidation and adsorption. The studies presented different paths of enhancing the SFN ability to remove the CPs including doping (ion substitution), oxide composite structure and polymer composite structure. Experimental parameters such as temperature, dosage of CPs and SFN structure have shown to have a major effect in the CP removal efficiency. More attention is needed to investigate the different properties of SFN that can be tailored through different techniques and expected to have major role in the removal mechanism of CPs.

Forward Osmosis Membranes: The Significant Roles of Selective Layer

Forward osmosis (FO) is a promising separation technology to overcome the challenges of pressure-driven membrane processes. The FO process has demonstrated profound advantages in treating feeds with high salinity and viscosity in applications such as brine treatment and food processing. This review discusses the advancement of FO membranes and the key membrane properties that are important in real applications. The membrane substrates have been the focus of the majority of FO membrane studies to reduce internal concentration polarization. However, the separation layer is critical in selecting the suitable FO membranes as the feed solute rejection and draw solute back diffusion are important considerations in designing large-scale FO processes. In this review, emphasis is placed on developing FO membrane selective layers with a high selectivity. The effects of porous FO substrates in synthesizing high-performance polyamide selective layer and strategies to overcome the substrate constraints are discussed. The role of interlayer in selective layer synthesis and the benefits of nanomaterial incorporation will also be reviewed.

State-of-the-Art Organic- and Inorganic-Based Hollow Fiber Membranes in Liquid and Gas Applications: Looking Back and Beyond

The aggravation of environmental problems such as water scarcity and air pollution has called upon the need for a sustainable solution globally. Membrane technology, owing to its simplicity, sustainability, and cost-effectiveness, has emerged as one of the favorable technologies for water and air purification. Among all of the membrane configurations, hollow fiber membranes hold promise due to their outstanding packing density and ease of module assembly. Herein, this review systematically outlines the fundamentals of hollow fiber membranes, which comprise the structural analyses and phase inversion mechanism. Furthermore, illustrations of the latest advances in the fabrication of organic, inorganic, and composite hollow fiber membranes are presented. Key findings on the utilization of hollow fiber membranes in microfiltration (MF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), pervaporation, gas and vapor separation, membrane distillation, and membrane contactor are also reported. Moreover, the applications in nuclear waste treatment and biomedical fields such as hemodialysis and drug delivery are emphasized. Subsequently, the emerging R&D areas, precisely on green fabrication and modification techniques as well as sustainable materials for hollow fiber membranes, are highlighted. Last but not least, this review offers invigorating perspectives on the future directions for the design of next-generation hollow fiber membranes for various applications. As such, the comprehensive and critical insights gained in this review are anticipated to provide a new research doorway to stimulate the future development and optimization of hollow fiber membranes.

Thin Film Biocomposite Membrane for Forward Osmosis Supported by Eggshell Membrane

There is a general drive to adopt highly porous and less tortuous supports for forward osmosis (FO) membranes to reduce internal concentration polarization (ICP), which regulates the osmotic water permeation. As an abundant waste material, eggshell membrane (ESM) has a highly porous and fibrous structure that meets the requirements for FO membrane substrates. In this study, a polyamide-based biocomposite FO membrane was fabricated by exploiting ESM as a membrane support. The polyamide layer was deposited by the interfacial polymerization technique and the composite membrane exhibited osmotically driven water flux. Further, biocomposite FO membranes were developed by surface coating with GO for stable formation of the polyamide layer. Finally, the osmotic water flux of the eggshell composite membrane with a low structural parameter (~138 µm) reached 46.19 L m⁻² h⁻¹ in FO mode using 2 M NaCl draw solution.

Interlayered Forward Osmosis Membranes with Ti3C2Tx MXene and Carbon Nanotubes for Enhanced Municipal Wastewater Concentration

Forward osmosis (FO) hybrid systems have the potential to simultaneously recover nutrients and water from wastewater. However, the lack of membranes with high permeability and selectivity has limited the development and scale-up of these hybrid systems. In this study, we fabricated a novel thin-film nanocomposite membrane featuring an interlayer of Ti₃C₂T_x MXene intercalated with carbon nanotubes (M/C-TFNi). Owing to the enhanced confinement effect on interfacial degassing and increased amine monomer sorption by the interlayer, the resulting M/C-TFNi FO membrane has a greater degree of cross-linking and roughness. In comparison with the thin-film composite (TFC) membrane without an interlayered structure, the M/C-TFNi membrane attained a water flux that was four times higher and a lower specific salt flux. Notably, the M/C-TFNi membrane exhibited excellent concentration efficiency for real municipal wastewater and enhanced rejection of ammonia nitrogen, which breaks the permeability-selectivity upper bound. This study provides a new avenue for the rational design and development of high-performance FO membranes for environmental applications.

Fabrication and Characterization of Sulfonated Graphene Oxide-Doped Polymeric Membranes with Improved Anti-Biofouling Behavior

In this study, cellulose acetate (CA) was blended with sulfonated graphene oxide (SGO) nanomaterials to endow a nanocomposite membrane for wastewater treatment with improved hydrophilicity and anti-biofouling behavior. The phase inversion method was employed for membrane fabrication using tetrahydrofuran (THF) as the solvent. The characteristics of CA-SGO-doped membranes were investigated through thermal analysis, contact angle, SEM, FTIR, and anti-biofouling property. Results indicated that anti-biofouling property and hydrophilicity of CA-SGO nanocomposite membranes were enhanced with addition of hydrophilic SGO nanomaterials in comparison to pristine CA membrane. FTIR analysis confirmed the successful decoration of SGO groups on CA membrane surface while revealing its morphological properties through SEM analysis. Thermal analysis performed using DSC confirmed the increase in thermal stability of CA-SGO membranes with addition of SGO content than pure CA membrane.

Antiviral Nanomaterials for Designing Mixed Matrix Membranes

Membranes are helpful tools to prevent airborne and waterborne pathogenic microorganisms, including viruses and bacteria. A membrane filter can physically separate pathogens from air or water. Moreover, incorporating antiviral and antibacterial nanoparticles into the matrix of membrane filters can render composite structures capable of killing pathogenic viruses and bacteria. Such membranes incorporated with antiviral and antibacterial nanoparticles have a great potential for being applied in various application scenarios. Therefore, in this perspective article, we attempt to explore the fundamental mechanisms and recent progress of designing antiviral membrane filters, challenges to be addressed, and outlook.

2D Nanocomposite Membranes: Water Purification and Fouling Mitigation

In this study, the characteristics of different types of nanosheet membranes were reviewed in order to determine which possessed the optimum propensity for antifouling during water purification. Despite the tremendous amount of attention that nanosheets have received in recent years, their use to render membranes that are resistant to fouling has seldom been investigated. This work is the first to summarize the abilities of nanosheet membranes to alleviate the effect of organic and inorganic foulants during water treatment. In contrast to other publications, single nanosheets, or in combination with other nanomaterials, were considered to be nanostructures. Herein, a broad range of materials beyond graphene-based nanomaterials is discussed. The types of nanohybrid membranes considered in the present work include conventional mixed matrix membranes, stacked membranes, and thin-film nanocomposite membranes. These membranes combine the benefits of both inorganic and organic materials, and their respective drawbacks are addressed herein. The antifouling strategies of nanohybrid membranes were divided into passive and active categories. Nanosheets were employed in order to induce fouling resistance via increased hydrophilicity and photocatalysis. The antifouling properties that are displayed by two-dimensional (2D) nanocomposite membranes also are examined.