Masoud Rahbari-Sisakht, Ahmad Fauzi Ismail, Pei Sean Goh
Agricultural irrigation accounts for the large majority of global freshwater withdrawals, and mounting water scarcity is driving increased interest in reusing municipal, industrial, and agricultural wastewater as an irrigation source. Membrane-based treatment spanning microfiltration, ultrafiltration, nanofiltration, reverse osmosis, forward osmosis, membrane bioreactors, and membrane distillation already underpins much of this reuse, but conventional membranes remain constrained by fouling, high energy demand, and an inherent trade-off between removing contaminants and retaining agronomically valuable nutrients. This review examines nanocomposite membranes as a materials-based strategy for overcoming these limitations. It surveys the classification of nanomaterials used in membrane design (zero-to three-dimensional fillers, including metal/metal oxide nanoparticles, carbon nanotubes, graphene oxide, and metal-organic frameworks, as well as emerging bio-based alternatives) and the principal fabrication routes dope blending, interfacial polymerization, surface coating, electrospinning, and in situ growth used to integrate them into polymeric and ceramic matrices. Evidence from the literature is synthesized across key performance dimensions relevant to agricultural reuse: water permeability and flux, fouling resistance and antimicrobial activity, selectivity and contaminant rejection, and mechanical, thermal, and chemical stability, with particular attention to configurations such as photocatalytic and antimicrobial nanofiltration membranes and fertilizer-drawn forward osmosis systems that target nutrient-selective performance. The review finds that nanocomposite modification can produce substantial, mechanism-specific improvements over pristine membranes, but that translating these laboratory-scale gains into field-scale agricultural practice will depend on resolving open questions around nanoparticle leaching and environmental safety, manufacturing scalability, and cost. Emerging directions, including machine-learning-guided membrane design, hybrid process integration, and green-synthesized nanomaterials, are identified as promising routes toward more sustainable, field-ready nanocomposite membrane technologies for agricultural water reuse.
Santanu Chowdhury, Saba Parveen, Shramana Roy Barman
Rapid urbanisation has led to global warming and releasing of CO 2 into the atmosphere which is the primary anthropogenic greenhouse gas, accounting for almost 65% of the radiative forcing that contributes for global warming. With many innovations to mitigate this ongoing climate threat, capturing CO 2 from the atmosphere utilizing membranes-based methods are being focused on in contemporary studies. Membrane separation of CO 2 has higher efficiency, lower energy demand, cost effectiveness and scalability. The present work evaluates the existing membrane-based techniques for CO 2 capture including Polymeric membranes, Inorganic membranes, Mixed Matrix membranes (MMM), Metal organic frameworks (MOFs) based membranes, Nano material infused membrane, Carbon based membranes and biochar-based membranes. Although polymeric membranes have received widespread acceptance for carbon capture (CC), emerging hybrid membranes with multiple carbon capture mechanism, superior mechanical strength and surface chemistry are being extensively studied in recent times. Sustainable and green carbonaceous membranes such as activated carbon and biochar-based membranes formulated from a range of bio-waste is another avenue of recent research that adheres to the circular economy framework. However, there are very few works on biowaste derived biochar membranes for CC, though they show promising efficiency.
Transport in many dense polymer membranes used for reverse osmosis, organic solvent nanofiltration, pervaporation, and gas separation has traditionally been interpreted through the solution–diffusion model, which treats the membrane as a dense, nonporous polymer phase where molecules dissolve and diffuse under concentration gradients. Although this framework has been useful for correlating membrane performance, its mechanistic foundation for water and solvent transport is contradicted by current experimental and molecular simulation evidence. Observations from positron annihilation lifetime spectroscopy, scattering methods, spectroscopic probes, and molecular dynamics simulations demonstrate that polymer membranes, long considered dense and nonporous, contain interconnected (sub)nanometer free-volume networks rather than isolated transient cavities. These molecular pathways provide a more physically grounded basis for interpreting transport across diverse membrane processes. Here, we synthesize recent experimental and molecular simulation evidence to establish interconnected pore networks as a unifying mechanistic framework for transport across major classes of dense polymer membranes. In pressure-driven liquid separations, solvent transport is governed by pressure-driven viscous flow through interconnected, solvent-filled pore networks. In pervaporation, liquid-like and vapor-like domains coexist within the membrane, indicating an internal phase transition rather than evaporation only at the downstream surface. In glassy gas-separation polymer membranes, permeability and selectivity are governed by pore connectivity, molecular sieving, and gas–wall interactions. Together, these insights shift membrane design from optimizing empirical solubility and diffusivity parameters toward engineering pore size, connectivity, tortuosity, and pore-wall chemistry.
Prashan M. Rodrigo, Bishweshwar Pant, Sunith B. Madduri, Raghava R. Kommalapati
An integrated approach combining Fe 3 O 4 nanoparticle-loaded biochar-assisted pretreatment and air-gap membrane desalination (AGMD) was investigated for treating phosphate-rich wastewater. This study addresses key limitations of conventional coagulants, such as residual chemical load and limited removal efficiency. Fe 3 O 4 nanoparticles were co-precipitated on oakwood biochar (Fe 3 O 4 /BC). The Fe 3 O 4 /BC composite acts as a coagulant that can be rapidly separated under an applied magnetic field. This study systematically evaluated the pretreatment performance for turbidity and phosphate removal in phosphate-rich wastewater. A 94% phosphate and 77% turbidity reduction was obtained with a 2.5 g L -1 Fe 3 O 4 /BC dosage. In parallel, hydrophilic polyethersulfone (PES) and hydrophobic polytetrafluoroethylene (PTFE) membrane configurations were tested in AGMD with and without Fe 3 O 4 /BC-assisted pretreatment. The AGMD permeate flux, overall energy efficiency, and membrane fouling were compared in PES/AGMD, PT + PES/AGMD, PTFE/AGMD, and PT + PTFE/AGMD processes. A 21 times greater initial flux was obtained with the PES membrane in AGMD at 70 °C and 27.3 °C hot feed and coolant temperatures than with the PTFE membrane. However, higher flux reduction and higher salt deposition were observed on the hydrophilic PES membrane without pretreatment. The energy consumption for the PES/AGMD, PT + PES/AGMD, PTFE/AGMD, and PT + PTFE/AGMD processes were 1.516, 1.492, 4.559, and 4.245 kWh L -1, respectively. Overall, the Fe 3 O 4 /BC-assisted pretreatment combined with AGMD presents a promising strategy for phosphate-rich municipal wastewater treatment. This enables effective contaminant removal while protecting membrane performance and reducing operational costs. Further work will focus on the reusability of Fe 3 O 4 /BC as a coagulant, long-term membrane performance, and pilot-scale validation.
Facing global energy shortages and environmental pollution, hydrogen energy is recognized as a key energy source for future energy transition due to its high energy density and zero-emission characteristics. The electrocatalytic hydrogen evolution reaction (HER), as an efficient hydrogen production method, has attracted widespread attention from researchers. Among numerous electrocatalytic materials, polymers have garnered significant attention due to their tunable molecular structures, low cost, high stability, and versatility in facilitating hydrogen evolution reactions (HER), oxygen evolution reactions (OER), oxygen reduction reactions (ORR), carbon dioxide reduction reactions, and nitrate reduction reactions. Based on studies of the mechanisms underlying these catalytic reactions, significant progress has been made in optimizing the properties of polymer materials. Therefore, this review summarizes the research advances in polymer-based electrocatalytic hydrogen production and discusses the challenges and future directions in the field of polymer-based electrocatalytic water splitting for hydrogen generation. It is expected to provide valuable insights and references for exploring and studying other catalytic reactions.
