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 research, published in Discover Green Chemistry by Yog Prakash Yadav, Madhab Gautam, Anju Kumari Das, Sanjay Singh, Chandradip Kumar Yadav, and Ajaya Bhattarai of Tribhuvan University, examines the combined anticorrosive power of saponin and sodium dodecyl sulfate, or SDS, on mild steel immersed in 0.5 molar sulfuric acid. Saponin is a naturally occurring biosurfactant best known as the source of the foamy lather in soap bark, Quillaja saponaria, and soapnut trees. Its molecules carry multiple polar functional groups, including hydroxyl and carbonyl moieties, alongside nonpolar hydrocarbon regions, giving them the amphiphilic character that defines all surfactants. SDS, by contrast, is a synthetic anionic surfactant familiar to anyone who has read the ingredient list of a shampoo bottle. The team reasoned that if the two molecules could cooperate at the steel–acid interface, the resulting protective film might outperform either compound acting alone.

The experimental design was thorough, combining classical gravimetric testing with modern electrochemical and spectroscopic techniques. Mild steel specimens, cut to 3 by 3 centimeter squares containing less than 0.3 percent carbon, were polished with silicon carbide papers of progressively finer grit, from 180 up to 2000, then cleaned in distilled water and sonicated in ethanol for twenty minutes. Pre-weighed samples were immersed in sulfuric acid solutions of varying concentrations, from 0.0125 to 0.5 molar, at temperatures spanning 298.5 to 328 kelvin, for exposure periods ranging from 3 to 96 hours. Some baths contained saponin alone, others contained saponin with SDS, and control baths contained only acid. After immersion, the specimens were reweighed on a precision semi-micro balance, and the weight loss was converted into corrosion rates expressed in millimeters per year.

The gravimetric results told a clear story. Saponin on its own achieved an inhibition efficiency of 64.30 percent at a concentration of 2.92 grams per liter, meaning nearly two-thirds of the corrosion that would have occurred in plain acid was suppressed. When SDS was added to the saponin solution, the efficiency climbed by 13.35 percentage points to 77.66 percent, and the corrosion rate fell to a minimum of 0.37 mils per year in the mixed system. The researchers attributed this improvement to a synergistic effect: the two surfactants interact in solution to form mixed micelles with improved stability, a conclusion supported by conductivity measurements showing that the critical micelle concentration of saponin drops from 0.734 grams per liter to 0.679 grams per liter when SDS is present. A lower critical micelle concentration means the molecules begin assembling into surface-active aggregates at lower doses, which translates into better surface coverage on the metal.

Electrochemical measurements provided even more striking evidence. In potentiodynamic polarization experiments, using mild steel as the working electrode, a saturated calomel electrode as the reference, and graphite as the counter electrode, the team measured corrosion current densities after stabilizing each system at open circuit potential for thirty minutes. Bare steel in sulfuric acid exhibited a corrosion current density of 2.62 times ten to the minus two milliamperes per square centimeter, a signature of severe attack. SDS alone halved the damage, achieving roughly 50 percent inhibition, while saponin alone reduced the current to 8.64 times ten to the minus three milliamperes per square centimeter, corresponding to 67 percent efficiency. But the mixed saponin–SDS system was in a different league entirely: the corrosion current density plummeted to 8.55 times ten to the minus four milliamperes per square centimeter, yielding an inhibition efficiency of 96.70 percent. Crucially, both the anodic reaction, in which iron dissolves into solution, and the cathodic reaction, in which hydrogen gas evolves, were suppressed, identifying the mixture as a mixed-type inhibitor that does not fundamentally alter the corrosion mechanism.

Electrochemical impedance spectroscopy reinforced the picture. Nyquist plots recorded from 100 kilohertz down to 1 hertz showed a very small semicircle for steel in plain acid, indicating low charge transfer resistance and rapid metal dissolution. With inhibitors present, the semicircles grew dramatically, and the largest capacitive loop, the highest charge transfer resistance, and the lowest double-layer capacitance appeared in the saponin–SDS system. Fitting the spectra to a Randles circuit with chi-square values below ten to the minus two confirmed that the mixed formulation delivers inhibition efficiencies of 70 percent or above at the interface. A higher charge transfer resistance means electrons face a greater barrier moving between the metal and the electrolyte, which is exactly what a dense, well-ordered protective film should produce.

Thermodynamic analysis revealed the nature of the protective layer. The experimental data fit the Langmuir adsorption isotherm closely, with correlation coefficients between 0.94 and 0.98 across all temperatures, indicating that the inhibitor molecules arrange themselves as a single monolayer on the steel surface. The standard Gibbs free energy of adsorption remained below minus 20 kilojoules per mole at every temperature tested, a threshold that points to physical adsorption driven by electrostatic attraction and van der Waals forces rather than the formation of new covalent bonds. Notably, both the enthalpy and entropy of adsorption were positive, meaning the process is endothermic and accompanied by increasing disorder, likely as water molecules are displaced from the metal surface. Consistent with this physical mechanism, inhibition efficiency declined as temperature rose, dropping from 93.46 to 80.57 percent for saponin and from 95.55 to 88.33 percent for the saponin–SDS mixture between 298.5 and 328 kelvin, because thermal agitation loosens the grip of adsorbed molecules.

Microscopic and spectroscopic examinations made the protection visible. Optical microscopy revealed extensive pitting and roughening on steel immersed in plain acid, while saponin-treated surfaces were noticeably smoother and the saponin–SDS surfaces were the most intact of all, retaining much of the original polished finish. Field-emission scanning electron microscopy confirmed these observations at higher magnification, showing that the mixed inhibitor preserved the polished surface even in a highly corrosive environment. Energy-dispersive X-ray analysis added elemental proof: carbon and oxygen signals increased on saponin-treated steel, and sulfur appeared when SDS was included, confirming that a carbon-, oxygen-, and sulfur-rich organic film had deposited over the iron. Fourier-transform infrared spectroscopy identified the functional groups involved, including broad hydroxyl stretches near 3400 wavenumbers, carbonyl stretches near 1700, and the characteristic sulfate vibrations of SDS between 1200 and 1300 wavenumbers, with the spectra indicating physical interactions and cooperative adsorption rather than the formation of a new chemical compound.

What makes this work resonate beyond the laboratory is its environmental framing. More than 60 percent of synthetic surfactants used industrially ultimately reach aquatic ecosystems, where petroleum-derived compounds can persist, accumulate in organisms, and harm aquatic life. By anchoring a biodegradable, plant-derived molecule at the heart of the formulation and using the synthetic component only as a synergistic partner, the Nepali team has sketched a template for greener corrosion control: formulations that are effective at low doses, inexpensive, and far less damaging when released. The authors note that efficiency does decline over prolonged immersion as the protective film partially desorbs, and that thermal stability remains a limitation, so engineering challenges remain before industrial deployment. Still, the demonstration that a soap bark extract and a detergent molecule can jointly block more than 96 percent of electrochemical corrosion in sulfuric acid is a vivid reminder that some of the most advanced materials science solutions may be growing quietly in trees, waiting to be tested against humanity’s oldest chemical enemies.

Subject of Research: Synergistic corrosion inhibition of mild steel in sulfuric acid using saponin and sodium dodecyl sulfate

Article Title: Anticorrosive efficacy of saponin and sodium dodecyl sulfate on mild steel specimens immersed in acidic medium

Article References: Yadav, Y. P., Gautam, M., Das, A. K., Singh, S., Yadav, C. K., & Bhattarai, A. (2026). Anticorrosive efficacy of saponin and sodium dodecyl sulfate on mild steel specimens immersed in acidic medium. Discover Green Chemistry, 1(1), Article 10. https://doi.org/10.1007/s44509-026-00008-0

Image Credits: AI Generated

DOI: 10.1007/s44509-026-00008-0

Keywords: corrosion inhibition, mild steel, saponin, sodium dodecyl sulfate, sulfuric acid, surfactants, electrochemical polarization, impedance spectroscopy, Langmuir adsorption isotherm, green chemistry, biosurfactants, physical adsorption

The study, published in the journal Environmental Geochemistry and Health by a team led by Hongyang Wang of Liaoning University together with colleagues from Northeastern University and Inner Mongolia Yitai Guanglian Coal Chemical, addresses a stubborn technical bottleneck. Coal seam water injection, in which water is pumped into a seam ahead of mining to pre-wet the coal, has long been a frontline dust control strategy. But conventional water struggles to infiltrate the pore and fracture networks of deep coal, especially when mixed metallic substances within the coal matrix block penetration. The result is uneven wetting, dry zones that shatter into inhalable dust during extraction, and suppression rates that fall far short of what occupational health standards demand.

The researchers’ solution is a composite formulation built from three widely available components: sodium gluconate, abbreviated SG, fatty alcohol polyoxyethylene ether known as AEO-3, and sodium fatty alcohol polyoxyethylene ether sulfate, or AES. Each ingredient plays a distinct role. Sodium gluconate, a chelating agent, is capable of binding the metallic substances dispersed in the coal, thereby clearing obstacles that would otherwise impede water movement through the coal’s internal pore structure. AEO-3, a nonionic surfactant, and AES, an anionic surfactant, work in combination to lower the surface tension of the injection solution and reduce the contact angle at the water-coal interface, two of the most important physical parameters governing how readily a liquid spreads across and soaks into a hydrophobic solid surface.

Coal is notoriously water-repellent. Its surface is dominated by hydrophobic carbon structures with relatively few oxygen-containing functional groups, the chemical handles to which water molecules can attach. The SAA formulation changes this chemistry. According to the team’s laboratory characterization, treatment with the agent increased the number of oxygen-containing functional groups on the coal surface, giving water more anchoring points and improving wettability at the molecular scale. At the same time, the surfactants promoted agglomeration of micron-sized coal dust particles, causing individual fine grains to clump into larger, heavier particles that settle out of the air more readily. The effect on particle size distribution was quantifiable: the median particle size, known as the D50 value, increased by 22.58 percent compared with untreated dust.

To test how these microscopic changes translate into real dust control performance, the team constructed a custom dust-suppression simulation system in the laboratory. The apparatus allowed them to generate airborne coal dust under controlled conditions and measure how effectively different spray solutions captured it. When SAA-treated water was used, the effective dust-suppression rate reached 71.50 percent. That figure is 2.17 times the performance of traditional water-mist dust suppression, meaning the formulated agent more than doubled the capture efficiency achievable with plain water alone. For an industrial process where even marginal gains in suppression translate into measurably lower respirable dust exposures for miners, a performance margin of this size is significant.

The most consequential part of the study, however, took place underground. The researchers carried out on-site dust suppression tests at the 3-802 working face of a production coal mine, injecting SAA-treated water into the seam using standard water injection equipment. Before injection, dust sampling established baseline conditions. After treatment, the average coal dust particle size at the face had risen to 2.53 times its pre-injection value, confirming that the agglomeration effect observed in the laboratory survived the journey from bench to bordeline. Larger particles mean less respirable dust, faster settling and cleaner air at the point where miners actually work.

Monitoring across multiple underground measurement points showed total dust suppression rates ranging from 60 to 84 percent, a broad but consistently strong performance envelope that reflects the natural variability of ventilation, mining activity and seam conditions across a working face. Beyond improving air quality, the treatment appeared to influence the mechanical behavior of the coal itself. The team reports that SAA water injection reduced the tendency of the coal to fracture and generate dust, a property linked in earlier research to burst liability, the dangerous propensity of some deep coal seams to fail suddenly and violently. By softening this tendency, the agent may offer a secondary safety benefit against rock bursts and coal bursts, phenomena that remain among the most feared hazards in deep mining.

What distinguishes this work from many prior surfactant studies, the authors argue, is the full chain of evidence it assembles. Laboratory mechanism analysis, surface chemistry characterization, particle size measurement, simulation chamber testing and underground field trials are all presented in a single integrated study, closing the gap that so often separates promising bench chemistry from deployable engineering practice. The funding came from the National Natural Science Foundation of China under grant 52427805, and the work involved authors from Liaoning University’s School of Environmental Sciences, Northeastern University’s School of Resources and Civil Engineering, and Inner Mongolia Yitai Guanglian Coal Chemical, a collaboration that pairs academic environmental science with direct industrial access.

The implications extend beyond a single mine. Deep coal mining is expanding in major producing nations, and occupational dust exposure remains a leading cause of preventable disease among miners, including coal workers’ pneumoconiosis, an incurable and often fatal lung condition. The health burden of coal dust has been documented extensively in the occupational health literature, and regulators continue to tighten permissible exposure limits. Technologies that make existing controls, such as water injection and water sprays, substantially more effective without requiring wholesale redesign of mining equipment are therefore valuable. The SAA formulation uses relatively inexpensive, commercially available chemicals, which the authors suggest positions it for practical engineering application.

Challenges remain before widespread adoption. Field performance will need to be validated across seams of different rank, metamorphic grade and mineralogy, since the wetting behavior of coal varies considerably with its chemical composition. Long-term dosing, environmental discharge and cost at scale will also require scrutiny. Nevertheless, the reported numbers give the approach credibility: a doubling of mist suppression efficiency in the lab, suppression rates of up to 84 percent underground, and a measurable reduction in fracturing tendency all point toward a wetting agent that does more than tweak surface tension. By combining chelation, nonionic and anionic surfactant synergy, and verified field performance, the SAA study offers deep coal mines a concrete new tool in the long-running fight against dust, and offers miners something even more precious: cleaner air at the coal face.

Subject of Research: A composite SAA wetting agent for enhancing coal seam water injection and dust suppression in deep coal mining

Article Title: High-efficiency ‘SAA’ wetting agent for coal mine dust control: from preparation and mechanism to field application

Article References: Wang, H., Zhao, T., Wang, H., Wang, H., Leng, Y., Pan, Y., Xu, L., & Zhu, Y. (2026). High-efficiency ‘SAA’ wetting agent for coal mine dust control: from preparation and mechanism to field application. Environmental Geochemistry and Health, 48(15), Article 600. https://doi.org/10.1007/s10653-026-03491-3

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03491-3

Keywords: coal mining, dust suppression, wetting agent, coal seam water injection, surfactants, deep mining, occupational health, coal dust, sodium gluconate, wettability, Environmental Geochemistry and Health, rock burst