The global water crisis has pushed researchers to revisit one of nature’s oldest separation mechanisms, and a comprehensive new review published in Polymer Bulletin suggests that forward osmosis, a membrane process long overshadowed by its pressure-driven cousin reverse osmosis, may finally be ready to move from laboratory curiosity to large-scale deployment. Ajay Lohar and Pragnesh N. Dave of the Department of Chemistry at Sardar Patel University in Gujarat, India, have synthesized the latest developments in membrane engineering and draw solute design, presenting a technical roadmap for a technology that could clean water at a fraction of the energy cost of conventional desalination.
The appeal of forward osmosis lies in its fundamental physics. Where reverse osmosis forces water through a semi-permeable membrane against its natural osmotic gradient using high-pressure pumps that consume substantial electricity, forward osmosis exploits osmotic pressure differences to drive water spontaneously across the membrane. On one side sits the feed solution, which may be seawater, brackish groundwater, or industrial wastewater; on the other sits a concentrated draw solution with a higher osmotic pressure that pulls pure water through the membrane. The result is diluted draw solution, from which clean water must subsequently be extracted and the draw agent recovered. Because the process operates at low or near-zero hydraulic pressure, it consumes dramatically less energy, and because fouling mechanisms in low-pressure environments are milder and more reversible than in pressurized systems, the membranes last longer and clean more easily.
The technology’s history stretches back further than many realize. Landmark studies in the mid-1970s demonstrated that drinking water could be extracted from seawater by forward osmosis, and early work explored applications ranging from emergency hydration bags using sugar as a draw solute to the concentration of fruit juices and dilute industrial wastes. Yet for decades the field was constrained by two stubborn problems: membranes that performed poorly under the peculiar conditions of osmotically driven flow, and draw solutes that were either too expensive, too toxic, or too difficult to regenerate. The new review argues that both bottlenecks are now being dismantled.
Concentration polarization is the central physical challenge. In pressure-driven membranes, polarization occurs on the feed side; in forward osmosis, a more insidious phenomenon called internal concentration polarization develops inside the porous support layer of the membrane itself, effectively shielding the selective layer from the full osmotic driving force. The review emphasizes the critical role of membrane orientation, noting that classic work by Gray, McCutcheon, and Elimelech showed how positioning the active layer toward the feed versus the draw solution radically changes internal polarization behavior and flux. Modern membrane design therefore focuses on minimizing the structural parameter, a metric that combines support layer thickness, tortuosity, and porosity. Thin-film composite membranes, in which an ultrathin polyamide selective layer is formed by interfacial polymerization on top of an engineered polysulfone support, have become the workhorse architecture. Recent work shows that enlarging support layer pore size, incorporating nanofibre interlayers, and improving connectivity between the selective layer and the support all reduce internal concentration polarization and boost water flux.
The frontier of membrane engineering now extends well beyond conventional thin-film composites. The review catalogs a striking array of advanced materials: graphene oxide laminates assembled layer by layer, sometimes stiffened with carbon nanotubes to restrain interlayer swelling; metal-organic framework nanoparticles embedded in the polyamide film to tune its free volume and hydrophilicity; electrospun nanofiber supports incorporating amorphous silica for high-flux desalination; and even two-dimensional MXene composites, which have recently been used to concentrate mango juice in food processing and to drive seawater desalination in combination with thermoresponsive draw agents. Inkjet-printed graphene oxide nanofiltration layers and cross-linked graphene quantum dot membranes represent approaches borrowed from precision manufacturing and nanomaterials chemistry. Nanofiltration-based selective layers, with their looser polyamide networks, have proven particularly valuable in hybrid systems, offering both antifouling behavior and high water permeability.
On the other side of the membrane, the draw solute problem is being attacked with equal creativity. Inorganic salts such as sodium chloride, magnesium chloride, copper sulfate, aluminum sulfate, ferric sulfate, and zinc sulfate deliver high osmotic pressures, but recovering them from the diluted draw solution typically demands energy-intensive evaporation or precipitation chemistry. The review documents innovative recovery routes, including metathesis precipitation for copper sulfate and reagent-based regeneration for zinc sulfate, alongside parametric studies comparing ammonium bicarbonate draw solutions that can be recovered by gentle heating. Fertilizer-drawn forward osmosis has emerged as one of the most elegant solutions for agriculture: nutrients such as calcium nitrate, NPK blends, and zinc nitrate serve as the draw agent and, after dilution, are applied directly to crops as fertigation, eliminating the need for draw recovery altogether. Recent bench- and pilot-scale studies have validated this approach for seawater dewatering and even real domestic wastewater treatment using slow-release fertilizers.
The most visually striking new class of draw solutes consists of engineered nanoparticles and soft materials. Dextran-coated and pectin-coated magnetite nanoparticles can pull water across the membrane and then be recovered with a simple magnet; poly-sodium-acrylate coatings, sodium alginate sulfate shells, and carbon quantum dots functionalized with sodium ions all aim to combine high water dispersibility with low reverse solute flux. Hydrogels and microgels add another dimension: stimuli-responsive polymer gels that swell to draw water and then collapse when heated, electrically stimulated, or exposed to carbon dioxide, releasing the captured water without any pumping. Polymer-graphene composite hydrogels, strong ionic hydrogels based on 2-acrylamido-2-methylpropane sulfonate, and poly(ionic liquid) hydrogels have all demonstrated enhanced flux, with particle size and crosslinking density emerging as key design variables. Dendrimers, the branched tree-like macromolecules, offer high osmolality at low concentration, and recent dendrimer-coated magnetic nanoparticles combine electrostatic drawing power with magnetic recovery, while dual-responsive versions switch with both temperature and carbon dioxide.
Perhaps the most consequential shift highlighted by the review is the rise of ionic liquids and deep eutectic solvents as next-generation draw agents. Ionic liquids, molten salts with tunable structures, can be engineered to exhibit upper critical solution temperature behavior, phase-separating from water above a specific temperature so that clean water is released with modest heating. Functionalized imidazolium ionic liquids, thermosensitive magnetic variants, and poly(ionic liquid) gels have all shown strong performance, and a 2025 bench-scale demonstration with cost analysis of thermoresponsive ionic liquid desalination suggests the economics are becoming credible. Deep eutectic solvents, low-cost eutectic mixtures of simple hydrogen-bonding components such as choline chloride and glycerol or citric acid, are attractive precisely because they are cheap, biodegradable, and easy to formulate. Studies have shown they can reclaim water from diverse feed streams, enrich low-abundance DNA and proteins for biotechnology, extract lithium from battery recycling wastewaters, and remove dyes from contaminated effluents. Notably, the review’s authors have themselves published work demonstrating that a citric acid–choline chloride (1:1) deep eutectic solvent is a promising draw solute for efficient dye removal, and oligomeric deep eutectic solvents and deep-eutectic-decorated magnetic nanoparticles have both been engineered to reduce reverse diffusion while simplifying regeneration.
The review also situates forward osmosis within a broader ecosystem of hybrid processes, which may be where its commercial future truly lies. Pairing forward osmosis with nanofiltration creates the widely studied FO-NF configuration for seawater desalination and wastewater reuse; coupling it with membrane distillation allows thermally driven draw recovery at pilot scale; and integrating it with reverse osmosis can dewater the concentrate streams that plague inland desalination plants. Resource recovery is a rapidly growing application, with techno-economic analyses showing that phosphorus, nitrogen, and water can be recovered from dilute human urine. Electric fields are being applied to suppress fouling, and machine learning is entering the field in earnest, with neural networks and AI-guided optimization now being used to predict flux, optimize membrane formulations, and guide performance prediction for polymeric membranes, including applications in boron recovery.
None of this erases the challenges. Reverse solute flux remains the field’s most persistent liability, contaminating the feed and eroding the driving force over time. Concentration polarization still caps achievable fluxes, and the mismatch between laboratory membranes and commercially available modules continues to slow scale-up. The authors point toward these problems directly, arguing that progress will depend on simultaneously engineering membranes with low structural parameters and designing draw solutes with high osmotic pressure, low diffusivity across the membrane, and simple, energy-efficient regeneration. If those goals can be met, forward osmosis could extend well beyond desalination into wastewater treatment, resource recovery, product concentration, and emergency water supply, positioning osmotic pressure, rather than hydraulic pressure, as the driving force behind the next generation of water purification.
Subject of Research: Recent advances in forward osmosis membrane engineering and draw solute development for water desalination, wastewater treatment, and resource recovery
Subject of Research: Chemistry
Article Title: Forward osmosis in the modern era: recent progress in membrane engineering and draw solute
Article References: Lohar, A., & Dave, P. N. (2026). Forward osmosis in the modern era: recent progress in membrane engineering and draw solute. Polymer Bulletin, 83(11), Article 598. https://doi.org/10.1007/s00289-026-06654-5
Image Credits: AI Generated
DOI: 10.1007/s00289-026-06654-5
Keywords: Forward osmosis, Membrane engineering, Draw solutes, Deep eutectic solvents, Water desalination, Wastewater treatment
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Denise Maddox. (September 10, 2026). Modern forward osmosis: advances in membrane engineering and draw solutes. Scienmag. https://scienmag.com/modern-forward-osmosis-advances-in-membrane-engineering-and-draw-solutes/
Denise Maddox. “Modern forward osmosis: advances in membrane engineering and draw solutes.” Scienmag, 10 September 2026, https://scienmag.com/modern-forward-osmosis-advances-in-membrane-engineering-and-draw-solutes/. Accessed 10 September 2026.
Denise Maddox. “Modern forward osmosis: advances in membrane engineering and draw solutes.” Scienmag. September 10, 2026. https://scienmag.com/modern-forward-osmosis-advances-in-membrane-engineering-and-draw-solutes/
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