The review, led by Jongryeol Yang, Haeun Kwon, Dawon Jeong, and Jin Woong Kim, surveys recent advances in what the authors call nanocellulose interface engineering. Their central message is that cellulose nanocrystals and cellulose nanofibrils, the two principal forms of nanocellulose, already possess the raw ingredients for exceptional emulsion stabilization: natural abundance, biodegradability, high aspect ratios, controllable wettability, and remarkable mechanical strength. What they lack, in their native state, is sufficient hydrophobicity to anchor themselves firmly at oil-water interfaces. The paper describes a growing toolbox of chemical and physical strategies designed to overcome this limitation and unlock applications in pharmaceutical delivery, food preservation, and cosmetic formulation.

To understand why particles can outperform molecules at stabilizing emulsions, the authors turn to a classic piece of colloid science. The adsorption energy of a spherical particle at an oil-water interface follows the relationship E = πr²γ(1 ± cosθ)², where r is the particle radius, γ is the interfacial tension, and θ is the contact angle the particle makes with the interface. Because this energy scales with the square of the particle size, even modest particles experience adsorption energies thousands of times greater than thermal energy, producing what researchers describe as irreversible interfacial anchoring. Once lodged at the boundary between oil and water, a particle essentially cannot be dislodged, which is why Pickering emulsions, named after early twentieth-century observations by Walter Ramsden and Spencer Umfreville Pickering, resist coalescence far better than surfactant-stabilized systems.

Cellulose nanocrystals, or CNCs, present a fascinating paradox. Produced by acid or enzymatic hydrolysis of cellulose fibers, these needle-like particles measure roughly 5 to 20 nanometers across and hundreds of nanometers long, and their surfaces carry negative charges from sulfate groups introduced during processing. That electrostatic repulsion should, in principle, disfavor interfacial adsorption and prevent the close packing needed for robust stabilization. Yet CNCs stabilize emulsions remarkably well, and the review explains why: crystallographic anisotropy. Different crystal faces of a CNC carry different chemistries. The hydrophilic faces, such as the (010) and (110) planes, expose hydroxyl groups and charged species, while the hydrophobic (200) edge planes present minimal polar functionality. When a CNC arrives at an oil-water interface, it orients itself so that its charged faces align with water and its hydrophobic edges dip into the oil, achieving favorable anchoring despite its overall hydrophilic character.

That elegant self-orientation, however, does not solve everything. The same sulfate groups that make CNCs water-soluble also generate intermolecular repulsion that impedes the formation of dense, mechanically strong interfacial networks. One remedy is ionic cross-linking. Simple monovalent salts such as sodium chloride and potassium chloride screen the negative charges, lowering both surface and interfacial tension. More dramatically, divalent metal cations such as zinc nitrate forge genuine cross-links between neighboring nanocrystals. Rheological measurements show that adding divalent metal nitrates transforms CNC suspensions into gel-like materials with enhanced storage and loss moduli, and the resulting three-dimensional networks suppress creaming, aggregation, and coalescence, conferring superior kinetic stability on the emulsions.

Chemical modification offers an even more direct route to better stabilizers. Because cellulose is studded with hydroxyl groups, chemists can graft a wide variety of molecules onto its surface. The review highlights work by Nigmatullin, Xu, and colleagues showing that attaching alkylamine chains of increasing length creates a controlled gradient of surface hydrophobicity. Longer alkyl chains amplify hydrophobic interactions between particles, attenuating electrostatic repulsion and promoting percolated self-associative networks with greater mechanical integrity. Octylamine-modified CNCs substantially reduce surface tension, and cryo-scanning electron microscopy confirms the formation of stable emulsion droplets armored with the modified crystals. In a related approach, Ataeian and colleagues used EDC/NHS coupling chemistry to graft polyamidoamine dendrimers onto CNCs, increasing water contact angles and enabling direct microscopic visualization of how densely the particles assemble on individual droplet surfaces.

Perhaps the most striking demonstration of molecular design comes from Tang and colleagues, who grafted polystyrene chains specifically onto the end groups of CNCs rather than their side surfaces. The result is a surfactant-mimicking architecture in which each particle carries a hydrophilic crystalline body and hydrophobic polymer tails. Emulsions stabilized by these amphiphilic CNCs exhibited exceptional coalescence resistance, maintaining their structural integrity for four months of storage. Such longevity, achieved without any molecular surfactant, illustrates how deliberately engineered particle geometry can rival or exceed conventional emulsifiers while avoiding their toxicity concerns.

Cellulose nanofibrils, or CNFs, behave differently from their crystalline cousins. With diameters of 10 to 50 nanometers and lengths of several micrometers, these flexible filaments do not simply sit at interfaces; they weave them. CNFs form interconnected fibrillary films at oil-water boundaries while simultaneously building three-dimensional networks in the surrounding water, restricting both droplet coalescence and droplet mobility. The review emphasizes that the degree of fibrillation is critical: completely nanofibrillated CNFs adsorb irreversibly onto droplet surfaces and form entanglement networks that raise viscoelastic moduli, whereas incompletely fibrillated material allows droplet deformation and eventual coalescence. Complementary strategies, including TEMPO-mediated oxidation that converts C6 hydroxyl groups into carboxylates and cationic modification with glycidyltrimethylammonium chloride, further tune charge and adhesion, with TEMPO-oxidized CNF emulsions maintaining consistent droplet size distributions for thirty days.

The most advanced engineering targets the remaining weaknesses of CNF films: porosity that lets internal phases leak out, and vulnerability to crystallization-induced destabilization when the encapsulated material is waxy or crystalline. Metal-phenolic network technology addresses the first problem by coating CNF-armored droplets with dense layers of phenolic compounds and metal ions. Park and colleagues validated the mechanism using DLVO theory, showing that the metal-phenolic coating amplifies hydrophobic interaction energies between CNFs and oil droplets, enabling stable emulsions even under low-energy vortexing. The phenolic layer adds antioxidant functionality, protecting oxidatively fragile cargo. For the second problem, metal-organic membranes built from metal cations and organic ligands create comprehensive envelopes around droplets, preventing leakage and confining crystal growth within the droplet interior. These membranes also promote interdroplet association networks that raise bulk viscosity and preserve long-term structural stability, and dual-chain hydrophobically modified CNFs have stabilized high-internal-phase emulsions exceeding 74 volume percent oil.

The authors are candid about the obstacles between laboratory success and industrial reality. Manufacturing nanocellulose at scale remains expensive and energy-intensive, with acid hydrolysis, TEMPO oxidation, and mechanical fibrillation all consuming significant resources, and batch-to-batch variability undermines the reproducibility that commercial products demand. Regulatory frameworks for nanomaterials in food, cosmetics, and pharmaceuticals are still underdeveloped, and comprehensive toxicological data remain scarce. The long-term degradation behavior of nanocellulose-stabilized interfaces under storage conditions is also poorly understood, complicating shelf-life predictions. Still, the review concludes that nanocellulose has already demonstrated remarkable colloidal stability, with reported formulations exceeding one month of ambient storage without phase separation. With greener processing, standardized safety protocols, and scalable formulation design, these plant-derived nanomaterials could transform how industry stabilizes everything from ice cream to injectable drug carriers, replacing a century of surfactant chemistry with engineered wood at the nanoscale.

Subject of Research: Nanocellulose interface engineering for stabilizing Pickering emulsions

Article Title: Advanced nanocellulose interface engineering for Pickering emulsion stabilization

Article References: Yang, J., Kwon, H., Jeong, D., & Kim, J. W. (2025). Advanced nanocellulose interface engineering for Pickering emulsion stabilization. Advances in Industrial and Engineering Chemistry, 1(1), Article 25. https://doi.org/10.1007/s44405-025-00021-0

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00021-0

Keywords: nanocellulose, Pickering emulsions, cellulose nanocrystals, cellulose nanofibrils, interface engineering, emulsion stabilization, surfactants, surface modification, metal-phenolic networks, metal-organic membranes, drug delivery, colloid science

The appeal of nanocellulose begins with its feedstock. Unlike synthetic ion-exchange resins or petroleum-derived adsorbents, cellulose can be extracted from wood, cotton, agricultural residues, and even bacterial fermentation, making it renewable, inexpensive, and biodegradable. At the nanoscale, cellulose takes two dominant forms that behave very differently in water. Cellulose nanocrystals, or CNCs, are rigid rod-like crystals typically prepared by acid hydrolysis, while cellulose nanofibrils, or CNFs, are long, flexible filaments obtained through mechanical disintegration, often combined with chemical pretreatments such as TEMPO-mediated oxidation, carboxymethylation, or deep eutectic solvent processing. Both forms carry an abundance of surface hydroxyl groups, which serve as chemical handles for grafting functional ligands, and both can be tuned to carry carboxyl, amino, thiol, or other charged groups that bind metal ions with high affinity.

Conventional adsorbents, the review notes, generally suffer from limited adsorption capacity, poor recyclability, and unsustainable raw material sources. Activated carbons, clays, and chitosan derivatives have all been tried against heavy metals with varying degrees of success, but the practical record shows recurring failures at scale: adsorbents saturate quickly, regenerate incompletely, and shed fines into treated water. Hydrogels sidestep several of these problems. As swollen three-dimensional networks, they offer internal pore space where metal ions can diffuse and be captured, and their soft, water-rich structure provides an ideal matrix for embedding functional nanomaterials, from carbon dots to metal-organic frameworks to nanoparticles of zero-valent iron. Crucially, hydrogels can be cast into beads, sheets, sponges, or monoliths that are easy to handle, pack into columns, and retrieve from treated water without filtration losses.

One of the review’s most valuable contributions is its mechanistic distinction between the two families of nanocellulose hydrogels. CNC-based hydrogels achieve synergistic adsorption through the functional groups arrayed on their crystal surfaces and through the composite networks formed when nanocrystals reinforce polymer matrices such as polyacrylamide or sodium alginate. Within these networks, metal ions are captured primarily by complexation and ion exchange, mechanisms that can be quantified and optimized by adjusting the surface charge density, aspect ratio, and crosslinking chemistry of the nanocrystals. In contrast, CNF-based hydrogels exploit their continuous fiber networks: the long fibrils create interconnected channels that promote mass transport deep into the gel, while the fibril surfaces bind ions electrostatically and trap them within the pore network. This combination of electrostatic attraction and pore entrapment gives CNF gels their characteristic high uptake and rapid kinetics, particularly for cations such as Cu(II) and Pb(II).

Performance, the review shows, hinges on chemistry. Carboxymethylated cellulose nanofibrils can remove copper ions efficiently because their deprotonated carboxylate groups exchange sodium or hydrogen for dissolved metal cations. Polyethylenimine grafted onto nanocellulose through microwave-assisted synthesis has demonstrated ultra-high adsorption capacity for lead and phosphate, an amine-rich surface that chelates cations while simultaneously binding anions. For the oxyanion chromium(VI), the chemistry flips: positively charged sites are needed, so researchers have grafted poly(acryloyl hydrazide) onto cellulose nanocrystals or used poly(m-aminobenzene sulfonate)-functionalized nanofibrils, achieving excellent adsorption capacities. Thiol-modified cellulose sponges capture mercury ions through soft-soft sulfur-metal interactions, while Fe-Cu alloy coatings on nanocrystals combine lead removal with antibacterial function, a dual capability relevant to real waters that carry both chemical and microbial hazards.

Several studies highlighted in the review push the technology toward intelligence, not just capacity. Fluorescent carbon dots incorporated into cellulose nanofibril and chitosan hydrogels allow simultaneous sensing and scavenging, so the same material that removes Cu(II) and Cr(VI) signals its progress optically, enabling operators to monitor saturation in real time. Stimuli-responsive designs add another layer: pH-responsive nanocellulose/alginate/metal-organic framework hydrogels can regulate ion uptake with changes in acidity, opening possibilities for triggered regeneration or controlled release. Mechanical durability, long the Achilles’ heel of hydrogel adsorbents, has been addressed through double-network architectures, ion-induced crosslinking with cations such as zinc, and physically crosslinked, self-healing composites of polyacrylamide and cellulose nanofibers that survive repeated deformation during column operation.

Cost and sustainability, the review emphasizes, are as decisive as performance. Low-cost production routes using agricultural waste feedstocks, including rice husk, banana rachis, sugarcane bagasse, barley straw, ramie fibers, garlic and agave waste, and licorice residue, demonstrate that nanocellulose adsorbents can be sourced from materials that would otherwise be burned or landfilled. Ball milling, mechanochemical processing, deep eutectic solvents, formic acid and choline chloride pretreatments, and Fenton-based oxidation have all been deployed to liberate nanocellulose from these matrices with reduced energy and chemical inputs compared with traditional sulfuric acid hydrolysis and intensive homogenization. Studies that tracked the economics of dicarboxylic nanocellulose for copper removal report competitive costs against commercial alternatives, suggesting that sustainability here need not come at a premium.

Real-world validation is beginning to appear. Nanocellulose/alginate composite beads modified in situ have been tested for purifying mining effluents, one of the harshest chemical environments any adsorbent can face, and porous sodium alginate/cellulose nanofiber microspheres have been evaluated in wastewater matrices rather than clean laboratory solutions. Rice husk-derived nanocellulose scaffolds have shown highly efficient removal of heavy metal ions from contaminated water, and nitro-oxidized nanofibrils from banana rachis have delivered both effective lead removal and strong structural films. Yet the review is blunt about the remaining gaps. Scalable, low-cost preparation remains an obstacle: many laboratory protocols rely on exotic reagents, long reaction times, or energy-intensive homogenization that would be difficult to reproduce at a treatment plant. Antifouling performance in complex water matrices is another unresolved challenge, since organic matter, oils, and microbial biofilms compete for surface area and can poison binding sites far faster than heavy metals arrive.

The authors close by sketching a roadmap for engineering translation. Future development, they argue, should prioritize functional designs that combine adsorption with detection and self-reporting, architectures that resist fouling in chemically complex effluents, and manufacturing processes validated on waste-derived feedstocks at industrially relevant scales. If those goals are met, nanocellulose hydrogels could shift heavy metal remediation away from energy-hungry precipitation and membrane processes and toward a quieter, greener model: materials grown from plants, deployed as soft three-dimensional networks, and returned harmlessly to the biosphere when spent. For a world in which four decades of sediment records show heavy metal contamination resurging even in highly regulated coastal waters, the prospect of a renewable adsorbent that captures lead from water and can be built from rice husks is more than a laboratory curiosity. It is a plausible piece of the global water security puzzle, and the detailed mechanistic understanding assembled in this review brings the field measurably closer to the day when that piece can be put into service.

Subject of Research: Nanocellulose-based hydrogels for heavy metal removal from contaminated water

Article Title: Review: nanocellulose-based hydrogels for heavy metal removal from water

Article References: Zuo, R., Wu, S., Sun, D., & Liu, Y. (2026). Review: nanocellulose-based hydrogels for heavy metal removal from water. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13763-z

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13763-z

Keywords: nanocellulose, hydrogels, cellulose nanocrystals, cellulose nanofibrils, heavy metal removal, water treatment, adsorption, agricultural waste, green adsorbents, wastewater remediation, stimuli-responsive materials, pollution