The environmental problem the team targeted is both persistent and growing. Mining, processing, and industrial use of rare earth elements generate acidic leachate streams and tailings laden with dissolved lanthanide ions. When discharged untreated, these effluents contaminate groundwater, surface water, and marine ecosystems. Yet the same streams represent an opportunity: recovering rare earths from industrial process water, acid mine drainage, and electronic waste leachates offers a double dividend, cutting pollution while reclaiming strategically valuable materials. Conventional treatment routes such as chemical precipitation, ion exchange, solvent extraction, and membrane filtration all carry limitations in cost, selectivity, or performance in dilute solutions, which is why adsorption has long been viewed as the most promising alternative.

Metal-organic frameworks, or MOFs, have changed the calculus for adsorption chemistry. These materials consist of metal clusters connected by organic linkers into porous, crystalline lattices with surface areas that can reach thousands of square meters per gram, far exceeding conventional adsorbents like activated carbon, zeolites, and clays. Among the most studied families is UiO-66, a zirconium-based framework prized for exceptional chemical, thermal, and mechanical stability in water. The researchers in this work went a step further by incorporating amine groups into the framework, replacing the standard terephthalic acid linker with 2-aminoterephthalic acid. The lone electron pairs on nitrogen atoms can interact directly with lanthanum ions, adding a chemical binding dimension on top of simple pore-based capture.

Synthesis of the material followed a solvothermal route. Zirconium chloride and 2-aminoterephthalic acid were dissolved in dimethylformamide, acetic acid was added as a modulator, and the mixture was heated at 120 degrees Celsius for 16 hours. The resulting powder was washed and vacuum-dried. X-ray diffraction confirmed a highly crystalline structure with characteristic peaks matching the known UiO-66-NH2 pattern, while field-emission scanning electron microscopy revealed multimodal spherical particles averaging below 200 nanometers in size, though with some aggregation. Nitrogen adsorption measurements yielded a Brunauer-Emmett-Teller surface area of 682 square meters per gram, a dominant pore size of 1.79 nanometers, and a pore volume of 0.27 cubic centimeters per gram, values consistent with the 600 to 1,200 square meter per gram range reported in the literature for this material family.

To find the best operating conditions, the team turned to response surface methodology, specifically a Box-Behnken design. Thirteen experimental trials varied adsorbent dosage and contact time, and a quadratic polynomial model was fitted to the removal data. Analysis of variance confirmed the model was statistically significant, with an F-value of 6.44 and a p-value of 0.0149. The adsorbent dose emerged as the dominant factor, while the coefficient of determination reached 0.82, explaining most of the variability in lanthanum removal. The statistical exercise converged on an optimal recipe: 10 milligrams of adsorbent per 10 milliliters of solution, a pH of 9, and 150 minutes of contact time.

The influence of pH proved particularly revealing. As pH rose from 3 to 7, lanthanum removal actually fell from 98.5 percent to 75.21 percent. The explanation lies in acid-base chemistry at the adsorbent surface: in acidic conditions, the amine groups accept protons and become positively charged, while hydrogen ions compete directly with lanthanum for binding sites. Above pH 7, the picture reverses. The framework surface becomes negatively charged, electrostatic attraction between the surface and the positively charged trivalent lanthanum ions strengthens, and removal efficiency climbs, peaking at pH 9. Adsorbent dosage showed a similar decisive effect, with removal rising from 64 percent to 99.86 percent as the dose increased from 3 to 10 milligrams, reflecting the growing availability of active sites.

Modeling the equilibrium and kinetics of the process provided mechanistic insight. The Freundlich isotherm, which describes multilayer adsorption on heterogeneous surfaces, fit the data better than the Langmuir model, with an R-squared value of 0.9986 and a heterogeneity coefficient of 1.98 indicating favorable adsorption. The Langmuir fit still yielded a maximum capacity of 312.5 milligrams per gram, placing UiO-66-NH2 well above most conventional adsorbents reported for lanthanum, including magnetic clay composites at around 111 milligrams per gram and silica xerogels at under 7. Kinetic analysis showed the pseudo second-order model best described the uptake, with an R-squared of 0.9971, suggesting that chemisorption, the formation of chemical bonds through electron exchange, is the rate-limiting step rather than simple mass transfer.

The Weber-Morris intraparticle diffusion model added a final layer of understanding. The plot produced a single linear line across the entire time interval examined, with a diffusion rate constant of 7.14 milligrams per gram per minute to the one-half power and a positive intercept of 12.8 milligrams per gram. The non-zero intercept indicates that intraparticle diffusion is not the sole rate-limiting factor; boundary-layer resistance and external mass transfer also contribute. Crucially, the absence of multiple linear segments means no transition between diffusion regimes occurred during the experiment, pointing to a single, consistent mass-transfer mechanism governing the process from start to finish.

Perhaps the most compelling demonstration came in seawater, a brutally competitive environment for any adsorbent. Spiked with 100 parts per million of lanthanum, real seawater contains roughly 9,000 parts per million of sodium ions and 1,000 parts per million of magnesium ions, both of which could theoretically crowd out the target metal. Yet when 10 milligrams of UiO-66-NH2 were added and the mixture agitated for 150 minutes, inductively coupled plasma mass spectrometry showed the material captured 87.5 percent of the lanthanum while taking up only 1.1 percent of sodium and 0.5 percent of magnesium in the first cycle. Over five sequential adsorption and acid-elution cycles, lanthanum recovery declined only modestly to 85 percent, while competing ion uptake rose to just 3.2 percent for sodium and 2.2 percent for magnesium.

The authors attribute this selectivity and capacity to two factors working in concert: the microporous architecture with its substantial surface area and pore volume, and the electrostatic and coordinative interaction between electronegative nitrogen atoms in the linkers and the trivalent lanthanum ions. Because lanthanum concentrations in real contaminated waters are typically far lower than those of coexisting cations, the framework’s preference for lanthanum over sodium and magnesium is exactly the property a practical separation technology requires. The researchers suggest that this class of amine-functionalized zirconium MOFs could be extended to remove heavy metals and rare earth elements from seawater and industrial streams alike, turning a stubborn pollution problem into a source of recoverable strategic materials.

Subject of Research: Amine-functionalized zirconium metal-organic framework adsorbent for lanthanum removal from water

Article Title: Amine-terminated zirconium metal-organic framework as an efficient adsorbent for lanthanum removal

Article References: Saranya, J., Ramesh, S., Kumar, R. T. R., & Haldorai, Y. (2026). Amine-terminated zirconium metal-organic framework as an efficient adsorbent for lanthanum removal. Frontiers in Materials, 13, Article 1944659. https://doi.org/10.3389/fmats.2026.1944659

Image Credits: AI Generated

DOI: 10.3389/fmats.2026.1944659

Keywords: metal-organic frameworks, UiO-66-NH2, lanthanum, rare earth elements, adsorption, water treatment, response surface methodology, Freundlich isotherm, adsorption kinetics, seawater selectivity, zirconium MOF, heavy metal removal

The study, published in Frontiers in Carbon, evaluated biochar made from M. baccifera both in its pristine form and after chemical activation, asking a deceptively simple question: how much does activation actually improve cadmium uptake, and what mechanisms drive the binding? The answer, quantified through isotherm and kinetic modeling, is that a potassium hydroxide treatment lifts the maximum adsorption capacity from 15.15 mg/g to 24.39 mg/g, a gain of roughly 60 percent, while the underlying surface area grows by only about 34 percent. That mismatch between porosity and performance is one of the most technically interesting findings of the work, because it points to surface chemistry, not just surface area, as the decisive factor.

To make the adsorbent, the researchers collected dried culms of M. baccifera, washed them, cut them into pieces, and carbonized them in a brick kiln under oxygen-limited conditions. The temperature was ramped gradually to 500 degrees Celsius and held there for four hours before the chamber was allowed to cool while still sealed, preventing oxidation of the freshly formed char. The resulting pristine biochar, designated MPB, was ground and sieved to a uniform 100 mesh, corresponding to particles of roughly 149 micrometers. This is deliberately low-tech pyrolysis, the kind of process that could plausibly be replicated in communities where the bamboo grows, which matters for any technology pitched as a cost-effective water treatment option.

Activation was where the chemistry got aggressive. The team treated the biochar with potassium hydroxide and phosphoric acid at concentrations of 20, 40, 60, and 80 percent, soaking 40 grams of biochar per liter of reagent for 24 hours on an orbital shaker at 150 rpm. The treated material was then heated to 800 degrees Celsius for 30 minutes in a muffle furnace, washed repeatedly with deionized water until the pH was neutral, and dried. When the variants were screened against a 10 mg/L cadmium solution, the 60 percent KOH treatment stood out decisively, achieving 97.89 percent removal. Phosphoric acid activation reached 73.93 percent, while the untreated biochar managed only 51.39 percent. KOH activation was selected for all subsequent experiments.

The reason KOH performs so well is partly textural and partly chemical, and the study disentangles both. During high-temperature carbonization, KOH reacts with carbon in a reaction that produces metallic potassium, hydrogen gas, and potassium carbonate. These products etch the carbon matrix, carving out new pores and exposing edge sites that oxidize on contact with air to form hydroxyl, carbonyl, and carboxyl groups. Nitrogen adsorption-desorption analysis confirmed the textural transformation: the BET surface area rose from 322 to 432 square meters per gram, average pore volume climbed from 0.154 to 0.212 cubic centimeters per gram, and micropore volume grew from 0.084 to 0.108 cubic centimeters per gram. Scanning electron micrographs showed correspondingly more developed pore structures and larger pore openings in the activated material.

But the numbers reveal that texture alone cannot explain the performance jump. If surface area were the whole story, a 34 percent increase in BET area should yield roughly a 34 percent capacity gain. Instead, capacity rose about 60 percent. The missing ingredient is functionalization. Fourier-transform infrared spectroscopy of the activated biochar showed intensified or shifted bands near 3,395 cm⁻¹ for O-H stretching, between 1,684 and 1,589 cm⁻¹ for C=O and C=C vibrations, and between 1,016 and 1,114 cm⁻¹ for C-O stretching. These oxygen-containing groups act as ligands for cadmium ions through metal-oxygen coordination and ion exchange, effectively adding chemical binding sites on top of the physical ones.

The FTIR evidence becomes even more compelling when spectra are compared before and after cadmium loading. The broad O-H/N-H envelope near 3,395 cm⁻¹ decreased in intensity and shifted slightly after cadmium adsorption, consistent with deprotonation and coordination of surface hydroxyl and phenolic groups. The carboxyl C=O band shifted from 1,685 to 1,687 cm⁻¹ in cadmium-bound pristine biochar and to 1,684 cm⁻¹ in the activated material, while the C=O stretching band between 1,572 and 1,589 cm⁻¹ moved to 1,583 and 1,589 cm⁻¹ respectively. The C-O region also shifted. Taken together, these spectral changes point to inner-sphere complexation of cadmium with carboxylate, carbonyl, and phenolic oxygen donors, with concurrent ligand and ion exchange at those sites, as the dominant binding mechanism.

Batch experiments mapped how the process behaves under different conditions. Solution pH proved to be the most influential variable: adsorption capacity increased with rising pH and peaked at pH 5. At lower pH, the abundance of hydrogen ions competes directly with cadmium ions for the same surface sites, suppressing uptake. As pH rises, that competition fades and cadmium can access the hydroxyl, carboxyl, and carbonyl groups identified by FTIR. The researchers deliberately stopped at pH 5 to avoid pushing the chemistry into a regime where cadmium hydroxide would precipitate, which would confound adsorption measurements with simple precipitation. Contact time experiments showed rapid initial uptake, with a substantial fraction of the total adsorption occurring within the first 30 minutes as vacant sites were filled, followed by a slowing rate that approached equilibrium after about 360 minutes. Increasing the initial cadmium concentration from 5 to 30 mg/L progressively saturated the finite adsorption sites, flattening the removal percentage at higher concentrations.

The equilibrium data were then fitted to a battery of isotherm models, and the results tell a coherent mechanistic story. The Langmuir model, which assumes a finite number of energetically uniform sites forming a monolayer, gave the best description, with correlation coefficients of 0.983 for pristine and 0.990 for activated biochar and maximum capacities of 15.151 and 24.39 mg/g respectively. The Sips model, a hybrid of Langmuir and Freundlich, yielded heterogeneity indices of 0.863 and 0.891, values close enough to unity to confirm near-Langmuir behavior. The Fowler-Guggenheim model, which probes lateral interactions between adsorbed molecules, returned negative interaction energies of −15.554 and −36.884 kJ/mol, indicating weak repulsive interactions among adsorbed ions at high surface coverage, though not strong enough to deviate significantly from Langmuir behavior. The Harkins-Jura multilayer model fit poorly, with correlation coefficients of 0.887 and 0.543, ruling out multilayer adsorption. For context, the 24.39 mg/g capacity of the activated bamboo biochar compares favorably with KOH-activated Enteromorpha prolifera biochar at 5.84 mg/g and pyrolytic carbon at 21.7 mg/g, and sits close to activated rice straw biochar at 24.7 mg/g.

Kinetic analysis completed the picture. The pseudo-first-order model produced moderate correlation coefficients but predicted equilibrium capacities far below the measured values, a well-known artifact of fitting only the initial adsorption phase. The pseudo-second-order model, by contrast, matched the experimental capacities almost exactly, with correlation coefficients above 0.999 for both materials and rate constants of 19.37 × 10⁻³ g/mg/min for pristine and 25.64 × 10⁻³ g/mg/min for activated biochar. This indicates that the rate-limiting step involves interactions between two species, typically the adsorbate and an adsorption site, rather than simple first-order decay of available sites. Intraparticle diffusion plots revealed two distinct stages, with a fast initial rate constant of 1.678 mg/g/min⁰·⁵ for the activated biochar dropping to 0.012 mg/g/min⁰·⁵ in the second stage, showing that diffusion inside particles contributes but is not the sole rate-controlling step. Liquid film diffusion, with rate constants of 0.015 and 0.02 cm/s, also plays a role, meaning the overall process is governed by a combination of film transport and intraparticle diffusion alongside the surface reaction.

What makes this study more than another adsorption data point is its grounding in a specific regional resource. Melocanna baccifera dominates large swaths of Northeast India, grows rapidly, and is often treated as a low-value lignocellulosic residue despite its high cellulose and hemicellulose content, which is precisely what makes it a good precursor for porous, oxygen-rich carbon after activation. The authors are candid about the limits of the work: the experiments were conducted in batch mode with synthetic cadmium solutions, and real wastewater carries competing ions, organic matter, and variable pH that could all erode performance. They call for continuous-flow column studies and testing with actual contaminated water as the necessary next steps. Still, the core demonstration stands. A locally abundant bamboo, a kiln, and a potassium hydroxide soak produce an adsorbent that removes nearly 98 percent of cadmium from a 10 mg/L solution and binds it through well-characterized surface chemistry. In a world where water treatment budgets are thin and heavy metal contamination is persistent, that combination of simplicity, low cost, and mechanistic understanding is exactly what scalable remediation requires.

Subject of Research: Cadmium ion adsorption from water using pristine and KOH-activated Melocanna baccifera bamboo biochar, analyzed through isotherm and kinetic modeling

Article Title: Cd(II) adsorption from aqueous solution using pristine and activated Melocanna baccifera biochar: isotherm and kinetics studies

Article References: Lalhruaitluanga, H., Lalchawiliana, K., Khiangte, L., Singh, T. P., & Hauhnar, L. (2026). Cd(II) adsorption from aqueous solution using pristine and activated Melocanna baccifera biochar: isotherm and kinetics studies. Frontiers in Carbon, 5, Article 1720673. https://doi.org/10.3389/frcrb.2026.1720673

Image Credits: AI Generated

DOI: 10.3389/frcrb.2026.1720673

Keywords: cadmium, biochar, Melocanna baccifera, KOH activation, water treatment, adsorption isotherm, adsorption kinetics, Langmuir model, pseudo-second-order, FTIR spectroscopy, heavy metal removal, sustainable adsorbent

The significance of the work lies in how the material was made. Conventional MOF synthesis typically relies on solvothermal or hydrothermal methods that require large volumes of organic solvents, elevated temperatures, and reaction times stretching over hours or days. Mechanochemistry, by contrast, drives chemical reactions through mechanical force. The team combined 25 mmol of the BPDC ligand with 50 mmol of zinc chloride in a 2:1 metal-to-ligand ratio and simply ground the powders for twenty minutes. The slight excess of metal salt, the authors note, ensures full coordination to both carboxylate groups without the need for ball milling, promoting framework formation while leaving minimal unreacted linker behind.

After grinding, the crude powder was washed in ethanol for two hours to strip away unreacted precursors, salts, and unbound ligand, then activated by drying at 50 degrees Celsius for 24 hours. From roughly 12.88 grams of starting materials, the researchers recovered 9.46 grams of product. Because mechanochemical synthesis uses little or no solvent, solvent molecules are far less likely to occupy the pore structure of the final material, preserving the active adsorption sites that make MOFs so effective at capturing dissolved pollutants.

A battery of characterization techniques confirmed that the grinding had indeed produced a genuine crystalline framework rather than a simple physical mixture. Fourier-transform infrared spectroscopy revealed new bands absent from the free ligand, including a broad absorption near 3369 cm⁻¹ attributed to coordinated or adsorbed solvent molecules at zinc centers, alongside shifts in carboxylate vibrations that verify coordination between BPDC ligands and Zn²⁺ ions. X-ray diffraction showed the disappearance of several ligand peaks and slight shifts in the remaining reflections, evidence of structural rearrangement upon framework formation rather than a loss of crystallinity. Energy-dispersive X-ray fluorescence confirmed zinc as the only significant metal in the material, with strong Zn Kα and Kβ emission lines at 8.6 and 9.6 keV.

The porosity measurements were equally encouraging. Nitrogen adsorption–desorption analysis using the BET method yielded a specific surface area of 221.022 m²/g, while Barrett–Joyner–Halenda analysis gave a pore volume of 0.134 cm³/g and an average pore diameter of 2.118 nm, placing the material squarely in the IUPAC mesopore range. Thermogravimetric analysis showed the framework remains stable up to about 310 degrees Celsius, with the organic ligand decomposing between 311 and 512 degrees and the structure collapsing beyond 520 degrees to leave zinc oxide residue. The point of zero charge was measured at pH 6, meaning the surface carries a net negative charge above that value and will electrostatically attract cationic species such as methylene blue.

To move beyond one-factor-at-a-time experimentation, the team employed response surface methodology with a Box–Behnken design, running 29 batch experiments across four variables at three levels each: adsorbent dosage from 0.1 to 0.5 grams, ionic strength from 0 to 0.17 mol/L, contact time from 30 to 120 minutes, and pH from 2 to 12. The resulting quadratic model achieved an R² of 0.9934, meaning 99.34 percent of the variation in dye removal could be attributed to the independent factors, with an adjusted R² of 0.9869 and a non-significant lack-of-fit test. Analysis of variance identified adsorbent dosage, contact time, pH, and their quadratic and interaction terms as statistically significant, while ionic strength played a comparatively minor role.

The desirability function pinpointed optimal conditions of 0.422 grams of adsorbent, an ionic strength of 0.0347 mol/L, a contact time of 61.78 minutes, and pH 11.2, predicting 99.51 percent removal. The experimentally verified value of 99.35 percent at a dye concentration of 30 mg/L fell remarkably close to the prediction, validating the statistical model. The strong pH dependence follows directly from the point of zero charge: above pH 6 the negatively charged surface draws the positively charged dye molecules, and at the highest tested pH of 12 removal peaked, whereas at pH 2 the protonated surface repelled the cationic dye and removal dropped to as low as 29.15 percent.

Isotherm analysis added mechanistic nuance. The Langmuir model, which assumes ideal monolayer adsorption on a homogeneous surface, fit poorly with an R² of just 0.3733. The Freundlich model performed moderately at 0.7089, with an exponent below unity signaling strong surface heterogeneity. The Temkin isotherm gave the closest fit at R² 0.8828, indicating that adsorbate–adsorbent interactions significantly influence the process and that the heat of adsorption decreases linearly with increasing surface coverage, a hallmark of heterogeneous MOF surfaces. The π-electron-rich aromatic rings of the BPDC linker are thought to engage in π–π interactions with the aromatic structure of methylene blue, complementing the electrostatic attraction.

Kinetic performance may be the study’s most striking result. Equilibrium was reached within approximately ten minutes, an abrupt drop in dye concentration occurring in the first ten minutes for all concentrations tested. That is markedly faster than many comparable adsorbents: HKUST-1 required about 60 minutes, Zn/Co-ZIF@CNT composites about 120 minutes, and ZnO-based adsorbents between 15 and 45 minutes. The adsorption followed a pseudo-second-order model with correlation coefficients exceeding 0.9999 across all concentrations, and equilibrium capacity rose from 8.29 to 41.49 mg/g as the initial dye concentration increased from 20 to 100 mg/L, while the rate constant declined under greater site competition.

Thermodynamics completed the picture. Across 298 to 338 K, the Gibbs free energy ranged from −12.465 to −17.396 kJ/mol, confirming a spontaneous process that becomes more favorable at higher temperatures. The positive enthalpy change of 20.026 kJ/mol marks the uptake as endothermic and sits at the boundary of the physisorption range of 2.1 to 20.9 kJ/mol, while the positive entropy change of +112.638 J/mol·K reflects increased randomness at the solid–liquid interface as dye–solvent interactions give way to dye–framework interactions. The authors caution that regeneration, reusability, column studies, real wastewater trials, and competitive adsorption remain outside the current scope, and future work will target improving the relatively low adsorption capacity and probing long-term stability. Still, the demonstration that a mortar and pestle can deliver a statistically optimized, near-complete dye scavenger underscores how green chemistry principles are reshaping the design of water-treatment materials.

Subject of Research: Mechanochemical synthesis of a zinc-based metal–organic framework for optimized adsorptive removal of methylene blue dye from water

Article Title: Response surface methodology optimization of methylene blue dye removal using a mechanochemically synthesized zinc-based metal organic framework with its isotherm, kinetic and thermodynamic insights

Article References: Kabo, K. S., Akeremale, O. K., & Alisi, I. O. (2026). Response surface methodology optimization of methylene blue dye removal using a mechanochemically synthesized zinc-based metal organic framework with its isotherm, kinetic and thermodynamic insights. Discover Chemistry, 3(1), Article 440. https://doi.org/10.1007/s44371-026-00889-x

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00889-x

Keywords: metal-organic frameworks, methylene blue, mechanochemical synthesis, adsorption, response surface methodology, wastewater treatment, zinc-based MOF, isotherm models, adsorption kinetics, thermodynamics, green chemistry, BPDC linker

The target of the study, methylene blue, is far more than a laboratory curiosity. This cationic thiazine dye is produced on an enormous scale for textile dyeing, paper coloring, and medical applications, and its release into waterways poses genuine ecological risks. Studies cited by the authors document toxic effects of methylene blue on the growth, reproduction, and physiology of aquatic organisms such as Daphnia magna, the tiny freshwater crustacean that serves as a sentinel species in ecotoxicology. Conventional remediation approaches, including activated carbon derived from apricot stones, olive pits, and walnut shells, can adsorb the dye, but they bind indiscriminately. In real effluents, where dozens of dissolved organic species compete for binding sites, that lack of selectivity quickly exhausts the adsorbent’s capacity for the one contaminant that actually matters.

The Hacettepe team’s answer draws on molecular imprinting, a technique often described as building a molecular mold. In classical imprinting, the target molecule is mixed with functional monomers and a cross-linker before polymerization; as the polymer network forms around the template, it locks in binding sites complementary to the template’s size, shape, and chemical functionality. Removing the template afterward leaves behind synthetic recognition cavities that can rebind the target with an affinity and selectivity that mimic, in a crude but useful way, the behavior of antibodies. The approach has matured over two decades into a versatile platform, with imprinted polymers now used for sensors detecting proteins, viruses, and biomarkers, as well as for selective extraction of pharmaceuticals, herbicides, and heavy metal ions from environmental waters.

What distinguishes the new study is the method used to attach the imprinted layer to the magnetic core: admicellar polymerization. Surfactant molecules adsorbed onto the nanoparticle surface assemble into bilayers known as admicelles, which solubilize the monomers and the template dye in their hydrophobic interior. Polymerization is then initiated within these surfactant assemblies, growing a thin polymeric film directly on the particle surface. Because the template is present during film formation, the resulting polymer carries imprinted cavities oriented outward, where they are accessible to the surrounding water. The technique, previously applied to coat cellulose, cotton fabric, nanocellulose, titanium dioxide particles, and carbon nanotubes, has the advantage of producing well-defined, surface-localized films without burying recognition sites deep inside a bulky polymer matrix, a common failing of bulk imprinting that leaves many sites unreachable.

The magnetic core beneath the silica shell and polymer film is what makes the system practical. Magnetite nanoparticles respond to an external magnetic field, so once the adsorbent has done its work in a batch of contaminated water, it can be collected in seconds with a simple magnet rather than filtered or centrifuged. The silica coating, a widely used architecture in nanomaterials science, stabilizes the iron oxide core against dissolution and aggregation while providing a chemically versatile surface for further modification. The authors verified each layer of this onion-like structure using a battery of characterization techniques: Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance confirmed the chemical bonds introduced at each modification step, X-ray Photoelectron Spectroscopy probed the surface elemental composition, and Transmission Electron Microscopy imaged the morphology of the coated particles.

Performance testing revealed a system governed by chemistry rather than chance. Adsorption kinetics followed a pseudo-second-order model with a coefficient of determination above 0.99, indicating that the rate-limiting step involves chemical interactions between the dye and the binding sites rather than simple diffusion or weak physical adhesion. The maximum binding capacity of the imprinted polymer-modified nanoparticles was determined to be 5.64 milligrams per gram, with a 95 percent confidence interval spanning 4.52 to 6.76 milligrams per gram. Equilibrium data fit the Freundlich isotherm model better than alternative models, with R squared again exceeding 0.99, a signature of heterogeneous adsorption behavior across binding sites of varying energy. That heterogeneity is exactly what theory predicts for molecularly imprinted systems, where the population of cavities inevitably includes a distribution of imperfectly formed sites alongside a subset of well-ordered, high-affinity ones.

The selectivity results are the study’s most striking numbers. The imprinting factor for methylene blue, which compares binding by the imprinted polymer to binding by a non-imprinted control, reached 7.18. When structurally related competitors were tested, the factor dropped to 3.11 for methylene violet and 1.97 for indigo carmine, showing that the cavities discriminate sharply in favor of the molecule that shaped them. Selectivity coefficients of 2.41 for methylene violet and 3.18 for indigo carmine confirmed the preferential recognition quantitatively. In practical terms, this means the adsorbent can distinguish between dyes that are close chemical cousins, a feat impossible for generic activated carbons whose binding depends only on nonspecific surface interactions. The optimum operating conditions proved refreshingly mild: a neutral pH of 7 and an incubation time of just 35 minutes, conditions compatible with straightforward deployment in real treatment settings.

Reusability, often the Achilles heel of engineered adsorbents, held up impressively. The material maintained its adsorption performance over seven consecutive adsorption-desorption cycles without significant loss of efficiency, a result that matters enormously for any realistic cost assessment of nanomaterial-based water treatment. The authors also moved beyond synthetic laboratory solutions, validating the system on real water samples collected from different natural sources. Demonstrating performance in genuine environmental matrices, with their dissolved salts, natural organic matter, and competing contaminants, is a critical step that many adsorbent studies omit, and it strengthens the case that the imprinted magnetic nanoparticles could function outside the controlled conditions of a chemistry bench.

The broader context makes the work timely. Dye-laden wastewater remains one of the most visible forms of industrial pollution, and the field has seen a surge of interest in magnetically modified adsorbents, from biomass-derived activated carbons to magnetic kaolinite clays and metal-organic framework composites. Molecularly imprinted magnetic adsorbents have been developed for targets as varied as tetracycline, diclofenac, bisphenol-A, phenoxy acid herbicides, and penicillin G, and the Hacettepe group itself previously used admicellar polymerization to build a tetracycline-selective magnetic adsorbent. The new study extends that methodology to a dye pollutant and provides a full analytical treatment of kinetics, isotherms, selectivity, and reusability, the standard metrics by which adsorption science judges a candidate material.

Challenges remain before such materials could see large-scale use, including the economics of nanoparticle synthesis at industrial volumes and the regulatory questions surrounding engineered nanomaterials in environmental applications. Yet the design principles demonstrated here, combining magnetic recoverability, a protective silica interface, and a selectively imprinted polymer skin applied by a scalable surface polymerization technique, point toward a future in which water treatment is not a blunt instrument but a targeted one. If adsorbents can be programmed to recognize specific pollutants the way this one recognizes methylene blue, the prospect of cleaning contaminated water without collateral losses of capacity becomes considerably more tangible.

Subject of Research: Molecularly imprinted polymer-modified magnetic nanoparticles for selective removal of methylene blue dye from water

Article Title: Surface modification of silica-coated magnetic nanoparticles for effective removal of methylene blue from water samples

Article References: Söylemez, M. A., Ozer, D., & Icten, O. (2026). Surface modification of silica-coated magnetic nanoparticles for effective removal of methylene blue from water samples. Journal of Nanoparticle Research, 28(10), Article 266. https://doi.org/10.1007/s11051-026-06789-6

Image Credits: AI Generated

DOI: 10.1007/s11051-026-06789-6

Keywords: magnetic nanoparticles, molecularly imprinted polymers, methylene blue, dye removal, wastewater treatment, admicellar polymerization, silica coating, adsorption kinetics, Freundlich isotherm, selectivity, water purification, nanomaterials

The study, published in Results in Chemistry, describes a dual-functional geopolymer concrete composite synthesised from ground granulated blast-furnace slag, a byproduct of steel processing sourced from Ballari, and sugarcane bagasse ash collected from a sugar factory in the Belagavi district. The researchers combined the two precursors in equal mass and activated them with an alkaline solution of 8 molar sodium hydroxide and sodium silicate mixed at a 1:1.5 mass ratio. Binder, fine aggregate and coarse aggregate were blended at a 1:1.72:2.59 mass ratio, cast into moulds, compacted and cured at room temperature. The result was a workable concrete, with a slump of 112 millimetres, whose compressive strength climbed from 8.53 megapascals at three days to 20.44 megapascals at seven days and 28.97 megapascals at 28 days, comfortably meeting the M25 structural grade target.

What makes the material interesting chemically is the reactive aluminosilicate matrix that forms during geopolymerization. When the alkaline activator dissolves the silica and alumina in the slag and ash, the dissolved species polycondense into a gel network rich in silicon, aluminium and calcium. Scanning electron microscopy revealed a heterogeneous surface studded with irregular particles, agglomerated regions and interconnected voids, the kind of porous architecture that offers both mechanical integrity and abundant access points for pollutant molecules. Energy-dispersive X-ray spectroscopy confirmed a composition dominated by calcium oxide at 48.34 percent, silicon dioxide at 28.09 percent and aluminium oxide at 12.06 percent, with smaller amounts of iron, sodium, magnesium, potassium and sulfur oxides traceable to the precursor wastes and activators.

Spectroscopic analysis filled in the molecular picture. Fourier transform infrared spectroscopy identified broad hydroxyl stretching bands between 3200 and 3600 reciprocal centimetres, H-O-H bending near 1630 to 1650, and the strong asymmetric Si-O-Al and Si-O-Si vibrations between 950 and 1100 that fingerprint the geopolymeric network. X-ray diffraction showed crystalline quartz and a calcium-sodium aluminosilicate phase called bytownite embedded within a broad amorphous hump between 20 and 35 degrees two-theta, the signature of alkali-activated binders. X-ray photoelectron spectroscopy found the surface dominated by oxygen at 37.95 atomic percent, followed by carbon, silicon, sodium, calcium, aluminium and magnesium, indicating a calcium-aluminosilicate surface rich in oxygen-containing groups. Thermogravimetric analysis showed the composite retained roughly 79.2 percent of its mass at 800 degrees Celsius, a mark of good thermal stability.

Porosimetry added the final structural detail: a specific surface area of 49.51 square metres per gram, a total pore volume of 0.076 cubic centimetres per gram and an average pore diameter of 8.03 nanometres, placing the material firmly in the mesoporous regime under IUPAC classification. The nitrogen sorption isotherms displayed an H3-type hysteresis loop between relative pressures of roughly 0.4 and 0.9, associated with slit-shaped pores and irregular, interconnected networks formed by particle aggregation and gel development. Rather than a neatly ordered framework, the pore system is a heterogeneous mix of mesopores, interparticle voids and surface irregularities, which the authors argue is well suited to ferrying phenol molecules toward adsorption sites buried inside the matrix.

Batch adsorption experiments, run in duplicate in 250-millilitre flasks agitated at 150 revolutions per minute, mapped how the composite performs under varying conditions. Adsorption surged during the first hour, reaching 12.21 milligrams per gram, then slowed as internal pores filled and sites became occupied, with equilibrium effectively reached at 180 minutes. Dosage told a classic trade-off story: at 1 gram per litre the capacity peaked near 18.92 milligrams per gram but removal was only about 19 percent, while at 10 grams per litre removal rose to 51.56 percent even as capacity fell to 8.59 milligrams per gram, a consequence of particle aggregation and sites left idle by the fixed phenol concentration. The team settled on 3 grams per litre as the practical optimum, balancing removal efficiency of about 37 percent with efficient use of the material.

Concentration and pH shaped the equilibrium behaviour in revealing ways. As the initial phenol concentration rose from 1 to 100 milligrams per litre, capacity climbed from 0.28 to 18.15 milligrams per gram while removal efficiency dropped from 82.96 to 54.44 percent, reflecting saturation of available sites. Adsorption increased as pH rose from 3 to 9, reaching 16.32 milligrams per gram, but fell back at pH 11. The explanation lies in acid-base chemistry: phenol, with a pKa near 9.9, stays mostly in its neutral molecular form below that threshold, while the composite’s point of zero charge sits around pH 10, so electrostatics play little role. Instead, the gains up to pH 9 reflect reduced competition from hydrogen ions and favourable hydrogen bonding between surface hydroxyl groups and phenol’s oxygen. At pH 11, deprotonation to phenolate ions, a negatively charged surface and hydroxide competition all conspire to suppress uptake. Because performance at neutral pH was nearly as good, the team chose pH 7 for practical operation.

Modelling pinned down the mechanism. Kinetic data fitted the pseudo-second-order model best, with a correlation coefficient of 0.9915 and a calculated equilibrium capacity of 13.81 milligrams per gram closely matching the experimental 12.21, pointing to chemisorption at the surface as the dominant rate behaviour. Intra-particle diffusion plots showed two linear stages, with a non-zero intercept indicating that diffusion alone does not control the rate, and liquid-film diffusion analysis confirmed that external mass transfer contributes during the early phase. On the equilibrium side, the Langmuir model won decisively with a correlation coefficient of 0.9985 and a maximum monolayer capacity of 11.08 milligrams per gram, while the Freundlich model’s strong fit of 0.9951 acknowledged some surface heterogeneity. The Dubinin-Radushkevich model’s poor performance suggested pore-filling is secondary to surface interactions. Taken together with post-adsorption changes in the hydroxyl band of the infrared spectrum and the partially filled pores seen in electron micrographs, the evidence points to hydrogen bonding with hydroxylated aluminosilicate sites, aided by pore diffusion and pore filling, as the principal uptake pathway, with sodium- and calcium-bearing sites playing possible supporting roles.

Reusability results were encouraging if not spectacular. Across six consecutive adsorption-desorption cycles using distilled water as the eluent, desorption efficiency declined from 74.58 percent in the first cycle to 57.33 percent in the sixth, a pattern consistent with a mix of reversible surface interactions and stronger, harder-to-reverse binding, plus some pore blockage. The authors suggest that alternative desorbing agents such as dilute acids, alkaline solutions or organic solvents, along with thermal or oxidation-based regeneration, could push performance further. Benchmarked against previously reported adsorbents, whose capacities range from 1.47 milligrams per gram for sawdust to 14.76 for African potato waste carbon, the composite’s 11.08 milligrams per gram at neutral pH is competitive, and it achieved that figure at a modest 3 grams per litre within 180 minutes.

The broader significance of the work lies in the fusion of two functions usually kept apart. Adsorbents are typically powders or granules with no structural role, while concrete is structural material with no environmental function; this composite is both, valorising two troublesome waste streams in the process. The authors are candid about what remains to be done: fixed-bed column trials to test continuous-flow performance, multi-pollutant experiments to probe competitive and synergistic adsorption, standardised heavy-metal leaching tests to confirm environmental safety, and optimised regeneration strategies for long-term reuse. But the concept, a load-bearing concrete that scrubs phenol from water while diverting steel slag and sugar ash from landfills, offers a glimpse of infrastructure that does more than stand up. It could, in principle, quietly clean as it carries.

Subject of Research: Dual-functional geopolymer concrete from agro-industrial wastes for phenol adsorption from water

Article Title: Evaluation of agro-industrial waste-derived concrete composite for phenol adsorption: Process optimization, kinetics, isotherm modelling and mechanistic insights

Article References: S.V., M., B.V., C., M.S., S., K., S., Y.M., P., S., S., Girish, C. R., Mohan, B., & A., S. M. (2026). Evaluation of agro-industrial waste-derived concrete composite for phenol adsorption: Process optimization, kinetics, isotherm modelling and mechanistic insights. Results in Chemistry, 31, Article 103954. https://doi.org/10.1016/j.rechem.2026.103954

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103954

Keywords: geopolymer concrete, phenol adsorption, ground granulated blast-furnace slag, bagasse ash, waste valorization, water treatment, adsorption kinetics, Langmuir isotherm, mesoporous materials, alkali activation, hydrogen bonding, sustainable construction

The environmental problem the team targeted is anything but trivial. Ammonium, the workhorse nitrogen compound of modern agriculture, leaches relentlessly from fertilized fields into rivers, lakes, and coastal waters. Once there, it fuels eutrophication—the runaway growth of algae and seaweed that suffocates aquatic ecosystems. The consequences are particularly visible in regions like the Caribbean, where massive seaweed blooms linked to nutrient enrichment and warming oceans have damaged coastal ecosystems and disrupted local livelihoods. With global sugarcane production topping two billion metric tons annually and banana production adding another 139 million metric tons, the residues from these crops represent both a disposal burden and, as this study shows, an untapped resource.

The core innovation lies in how the banana waste was used. Rather than relying on laboratory-grade reagents and specialized equipment—the standard approach in most biochar modification research—the team created a modifying extract from banana peel powder and banana peel ash. The peel contributes oxygen-rich organic compounds such as hydroxyl, carboxyl, and phenolic groups, while the ash supplies alkali metals, particularly potassium and sodium. The researchers mixed 20 grams of peel powder with 4 grams of ash in either hydrochloric acid or sodium hydroxide solution, stirred the mixture at 80 degrees Celsius for four hours, and filtered out the resulting extract. Direct characterization of the dried extract confirmed its dual nature: Fourier-transform infrared spectroscopy revealed hydroxyl, carboxylate, and carbon-oxygen functional groups, while energy-dispersive X-ray spectroscopy showed the residue was 52.37 percent oxygen by weight, with sodium at 20.36 percent and potassium at 14.31 percent.

The sugarcane bagasse itself was first converted to biochar through pyrolysis in a nitrogen atmosphere. Using a central composite design to balance carbonization quality, yield, and pore development, the team settled on a pyrolysis temperature of 600 degrees Celsius and a residence time of 69 minutes. The resulting pristine biochar, labeled SC-Opt, boasted a respectable BET surface area of 123.62 square meters per gram. The researchers then tried both pre-treatment—soaking raw bagasse in the extract before pyrolysis—and post-treatment—soaking the finished biochar afterward—with acidic and basic versions of the extract, producing four candidate materials.

The winner was SC-Pre-B, the biochar pre-treated with the basic banana peel-ash extract, and its performance profile challenges one of the field’s most intuitive assumptions. Pre-treatment with the basic extract collapsed the biochar’s surface area from 123.62 square meters per gram down to just 1.00 square meter per gram, as salt crystals deposited within micropores and the compromised biomass structure fused during pyrolysis. Yet this seemingly destructive change coincided with a dramatic improvement in ammonium uptake. In screening experiments, the pristine biochar adsorbed a mere 0.7 milligrams of ammonium-nitrogen per gram, while SC-Pre-B achieved roughly 4 milligrams per gram—nearly a sixfold increase. Under optimized isotherm conditions, the material reached an experimental maximum adsorption capacity of 17.11 milligrams per gram. The message is unambiguous: for ammonium capture, surface chemistry trumps physical surface area.

The mechanistic explanation rests on three pillars documented through an impressive battery of analytical techniques. First, zeta potential measurements showed that modification pushed the biochar’s surface charge to as negative as minus 52 millivolts, creating a powerful electrostatic pull on positively charged ammonium ions. Second, X-ray diffraction and electron microscopy confirmed that alkali metals from the ash had been embedded throughout the biochar, with potassium chloride crystallites identified as sylvite. These weakly bound potassium and sodium ions serve as exchangeable sites: elemental analysis before and after adsorption showed potassium and sodium levels dropping as nitrogen content rose, direct evidence that ammonium ions had swapped places with the native cations. Third, infrared spectroscopy revealed shifts in hydroxyl and carboxylate bands after adsorption, indicating hydrogen bonding as a secondary stabilizing interaction.

The adsorption kinetics followed a familiar but instructive pattern. A pseudo-second-order model best described the overall uptake, with rapid initial adsorption during the first six hours as abundant negatively charged and exchangeable sites captured ammonium, followed by slower uptake as the process moved into less accessible regions. Segmented intraparticle diffusion analysis identified three distinct stages with progressively decreasing rate constants, and the non-zero intercepts confirmed that diffusion contributed to—but did not solely control—the process. Notably, the researchers were careful to frame the 24-hour contact time as an operational endpoint rather than proof of complete equilibrium, since the final diffusion stage had not flattened to zero. On the isotherm side, the Langmuir-Freundlich model edged out its competitors with the lowest residual sum of squares, Akaike information criterion, and Bayesian information criterion values, pointing to heterogeneous adsorption sites with varying affinities, though the Langmuir model remained statistically comparable.

The study is refreshingly honest about its limitations. A competing-ion experiment showed that potassium ions, even at molar ratios below that of ammonium, significantly suppressed ammonium uptake—capacity fell from 3.4 to 2.2 milligrams per gram as potassium concentrations rose from 15 to 90 milligrams per liter. This revealed that SC-Pre-B operates through non-specific cation exchange rather than selective ammonium binding, meaning performance in real wastewater, with its cocktail of competing ions, would likely fall short of the synthetic-solution results. Reusability testing over five water-regeneration cycles showed the material retained about 57 percent of its initial capacity, a partial but incomplete recovery that reflects the difficulty of regenerating ion-exchange adsorbents with plain water instead of salt or acid solutions.

What makes this work resonate beyond the laboratory is its accessibility. The modification required only moderate heating, stirring, and basic equipment—no ultrasound baths, no ball mills, no rare-earth dopants. Previous efforts to boost biochar’s ammonium capacity have achieved higher numbers, such as 111.87 milligrams per gram for iron-and-nitrogen-modified walnut shell biochar, but at the cost of reagent intensity and technical complexity that put them out of reach for many of the regions where eutrophication hits hardest. By contrast, SC-Pre-B’s moderate capacity of 17.11 milligrams per gram compares respectably with other modified biochars when differences in experimental conditions are considered, and its entire production chain—from sugarcane juice shop to banana research institute—embodies the circular bioeconomy in miniature.

The road to practical application remains long. The authors themselves emphasize that validation with real wastewater, improved selectivity, optimized regeneration protocols, and careful environmental assessment of the acid and base used in extract preparation are all needed before the technology leaves the bench. There is also tantalizing potential in the spent material: ammonium-laden biochar could conceivably serve as a slow-release soil fertilizer, closing the nutrient loop entirely, though its release behavior would need thorough evaluation. For now, the study stands as an elegant proof of concept that the chemistry of waste can outperform the chemistry of the catalog—turning peel and pulp into a filter that defends the very waters that agriculture has fouled.

Subject of Research: Waste-derived biochar modification for ammonium removal from water

Article Title: Sustainable modification of sugarcane bagasse with a novel banana peel ash extract for enhanced ammonium adsorption

Article References: Morgan, H. M., Jr., Yen, T.-B., & Tsai, W.-T. (2026). Sustainable modification of sugarcane bagasse with a novel banana peel ash extract for enhanced ammonium adsorption. Discover Chemistry, 3(1), Article 451. https://doi.org/10.1007/s44371-026-00912-1

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00912-1

Keywords: biochar, ammonium adsorption, sugarcane bagasse, banana peel ash, water treatment, eutrophication, cation exchange, agricultural waste, circular economy, pyrolysis, zeta potential, adsorption kinetics

Corn silk, the fibrous tuft of styles that emerges from an ear of maize, has essentially no commercial value and is usually left to rot on fields after harvest. Yet chemically, it is a treasure. Composed of cellulose and lignin, its surface is densely decorated with oxygen-bearing functional groups, including carbonyl, carboxyl and hydroxyl moieties, along with amine groups from proteins. Prior research had already shown that raw corn silk can capture lead, copper, zinc and cadmium from aqueous solutions, but its capacity to bind hexavalent chromium had never been systematically explored. A team of Iraqi researchers, led by Dhufr Abdulghani Omer and Doha Neithal Saad, recognized that this abundant biowaste could serve as the backbone of a next-generation adsorbent, provided they could solve a fundamental practical problem that has long plagued powdered biosorbents: how to retrieve them from treated water.

Their solution was to make the material magnetic. Using a straightforward co-precipitation method, the researchers dispersed five grams of cleaned, sun-dried and milled corn silk powder in water, then added an iron salt solution containing ferric and ferrous chloride in a two-to-one molar ratio. When ammonium hydroxide was dripped in at sixty degrees Celsius, the mixture turned black, the visual signature of magnetite, or Fe3O4, nanoparticles nucleating on the fibrous corn silk scaffold. The resulting material, dubbed M-CSC, was filtered, washed to neutral pH and dried overnight in a vacuum oven. The elegance of the approach lies in its integration of two complementary functions: the corn silk contributes a rich landscape of chemical binding sites, while the embedded magnetite grants the composite a property that no amount of filtration or centrifugation can match, namely the ability to be pulled out of a suspension with a simple external magnet.

Characterization confirmed that the synthesis had worked as designed. Fourier-transform infrared spectroscopy revealed new peaks at 630 and 567 inverse centimeters corresponding to iron-oxygen stretching vibrations, alongside subtle shifts in the hydroxyl and carbonyl bands that indicated coordination between the magnetite and the biomass. X-ray diffraction showed the characteristic reflections of cubic spinel Fe3O4 superimposed on the semi-crystalline cellulose pattern, and application of the Debye-Scherrer equation yielded a crystallite size of roughly 6.2 nanometers, placing the magnetic domains firmly in the nanoscale regime. Nitrogen adsorption measurements classified the composite as mesoporous, with a BET surface area of 139.49 square meters per gram, a total pore volume of 0.0873 cubic centimeters per gram and an average pore diameter of about 4.14 nanometers, an architecture well suited to granting chromium species access to interior binding sites.

The magnetic performance proved equally impressive. Vibrating sample magnetometry recorded a saturation magnetization of 27.23 electromagnetic units per gram for the fresh composite, falling to 16.44 after chromium uptake, a decline attributable to the non-magnetic chromium layer shielding part of the magnetite contribution. Crucially, the material retained strong magnetic sensitivity even after adsorption, meaning a magnet could still retrieve it from treated water. Zeta potential measurements added a mechanistic clue: the composite carried a positive surface charge of plus 27 millivolts, which dropped to plus 5 millivolts after exposure to chromium, evidence of strong electrostatic attraction between the positively charged surface and the negatively charged HCrO4 and Cr2O7 anions that dominate acidic solutions.

Batch adsorption experiments mapped out the optimal operating conditions with statistical rigor. Solution pH emerged as the single most influential variable, with removal efficiency peaking at 97.71 percent at pH 2, where the predominant HCrO4 anion enjoys favorable electrostatics and the adsorbent surface remains heavily protonated. An adsorbent dose of 0.5 grams delivered a maximum removal efficiency of 98.65 percent for a 100 milligram per liter chromium solution, while contact time experiments showed rapid uptake within the first hundred minutes and near-equilibrium at 120 minutes, at which point removal reached 98.88 percent. Temperature worked against the process: removal slipped from 98.89 percent at 20 degrees Celsius to 96.71 percent at 50 degrees Celsius, and the adsorption capacity climbed toward 19.58 milligrams per gram as initial concentration rose, driven by the steepening concentration gradient between bulk solution and adsorbent surface. One-way analysis of variance confirmed that every parameter, from pH to contact time, exerted statistically significant effects, with pH registering the largest F-value at over 107,000.

Modeling the equilibrium and kinetic data painted a picture of a heterogeneous, multi-mechanism process. Among four isotherm models tested, the Temkin equation fit best with a correlation coefficient of 0.942, followed closely by Langmuir, which estimated a maximum monolayer capacity of 24.04 milligrams per gram, nearly identical to the experimental value. The Dubinin-Radushkevich mean adsorption energy of 15.379 kilojoules per mole suggested physical adsorption reinforced by stronger surface interactions. Kinetic analysis favored the Elovich model, whose high correlation coefficient of 0.964 points to an energetically non-uniform surface with sites of varying affinity, while the pseudo-second-order model also performed well. Thermodynamics sealed the energetic story: negative Gibbs free energy values across the 20 to 50 degree Celsius range confirmed spontaneous adsorption, a negative enthalpy change of minus 32.1 kilojoules per mole confirmed the exothermic character, and a negative entropy change of minus 93.27 joules per mole per kelvin reflected the loss of configurational freedom as chromium species became immobilized on the surface.

Spectroscopic evidence after adsorption filled in the molecular details. The hydroxyl stretching band shifted and weakened, the carbonyl band migrated, and the iron-oxygen bands moved, collectively indicating hydrogen bonding, complexation with carbonyl and amide groups, and surface coordination onto iron sites. A new band near 947 inverse centimeters, associated with chromium-oxygen vibrations, provided direct spectral confirmation of uptake. Energy-dispersive X-ray analysis detected elemental chromium on the spent adsorbent surface and revealed depletion of surface potassium, magnesium and calcium cations, hinting at an ion-exchange contribution. The authors were careful to note that a proposed reduction of hexavalent chromium to the less toxic trivalent form remains speculative, since their analytical methods could not distinguish chromium oxidation states, and they recommend X-ray photoelectron spectroscopy for definitive speciation in future work.

Perhaps the most consequential result for real-world deployment came from the regeneration trials. Using 0.1 molar sodium hydroxide to strip the adsorbed chromium, the team cycled the same adsorbent sample through five successive adsorption-desorption rounds. Removal efficiency began at 98.88 percent and declined to 84.62 percent by the fifth cycle, a loss the authors attribute to partial blocking of active sites and incomplete desorption, though they caution that these mechanisms were not directly verified. Retaining roughly 85 percent of its original performance after five cycles, the composite demonstrates the kind of reusability that determines whether a laboratory curiosity can become a practical water treatment technology. Taken together, the findings position magnetic corn silk composite as a low-cost, environmentally benign and magnetically recoverable adsorbent, and they illustrate a broader principle gaining momentum in materials science: that agricultural residues once dismissed as worthless can be transformed, with modest chemistry, into sophisticated functional materials that tackle some of the world’s most stubborn water pollution problems.

Subject of Research: A magnetic corn silk composite adsorbent for removing hexavalent chromium from contaminated water

Article Title: Magnetic corn silk composite: a sustainable approach for efficient removal of hexavalent chromium from aqua

Article References: Omer, D. A., Mahmood, A. S., Mohammed, H. A., & Saad, D. N. (2026). Magnetic corn silk composite: a sustainable approach for efficient removal of hexavalent chromium from aqua. Results in Chemistry, 31, Article 103960. https://doi.org/10.1016/j.rechem.2026.103960

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103960

Keywords: hexavalent chromium, corn silk, magnetic adsorbent, Fe3O4 nanoparticles, water treatment, adsorption, agricultural waste, co-precipitation, isotherm modeling, adsorption kinetics, thermodynamics, wastewater remediation

Rhodamine B is not a harmless colorant. The xanthene dye is widely used in textiles, inks, and even as a tracer in water studies, but exposure has been linked to harmful effects in aquatic organisms. Recent research cited by the team documents damage to the antioxidant system and photosynthesis of the aquatic plant Hydrilla verticillata, as well as ALS-like behavioral symptoms in zebrafish. Because conventional treatment plants are not designed to remove such synthetic organic molecules, adsorption has emerged as an attractive remediation strategy: it is simple, does not produce toxic byproducts when the right adsorbent is chosen, and can be scaled using packed columns or batch dosing. The challenge lies in finding adsorbents that are fast, efficient, and reusable, which is precisely where the graphene family enters the story.

The researchers prepared their two adsorbents from the same starting point. Graphene oxide was synthesized using the well-established Hummers method, in which graphite is oxidized and exfoliated into single sheets decorated with oxygen-containing functional groups such as hydroxyl, epoxy, and carboxyl moieties. Reduced graphene oxide was then produced by treating the graphene oxide with hydrazine hydrate under ultrasonication, a process that strips away many of those oxygen groups and restores a more graphitic, carbon-rich surface. The difference between the two materials is subtle but chemically profound: graphene oxide is hydrophilic and negatively charged across a wide pH range, while reduced graphene oxide is more hydrophobic and carries fewer charged sites. To confirm what they had made, the team deployed a battery of characterization tools, including Fourier-transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, and zeta potential measurements, each of which tracks the structural and surface changes that accompany reduction.

The adsorption experiments were systematic, varying solution pH, contact time, adsorbent dosage, and initial dye concentration. The results revealed a striking dependence on acidity. Graphene oxide performed best at pH 4, where it removed 99.94 percent of the dye, while reduced graphene oxide reached its optimum under alkaline conditions at pH 8, achieving 99.83 percent removal. This divergence makes chemical sense. Rhodamine B is a cationic dye, meaning it carries a positive charge in solution, and it is therefore drawn electrostatically to negatively charged surfaces. Graphene oxide, dense with ionizable oxygen groups, presents a strongly negative surface at acidic to neutral pH, maximizing the attraction. Reduced graphene oxide, having lost many of those groups, relies more on pi-pi interactions between the aromatic rings of the dye and the restored graphitic domains, and its optimum shifts accordingly. Equilibrium was reached remarkably quickly: ten minutes for graphene oxide and fifteen minutes for reduced graphene oxide.

Speed alone does not reveal mechanism, so the team fitted their kinetic data to established models. The pseudo-second-order model described the process best for both adsorbents, a result with real mechanistic weight. Unlike the pseudo-first-order model, which assumes the uptake rate depends only on the amount of vacant surface sites, the pseudo-second-order model implies that the rate-limiting step involves chemical interactions between the adsorbate and the surface, a hallmark of chemisorption. In practical terms, the dye molecules are not merely weakly clinging to the carbon sheets through van der Waals forces; they are engaging in specific electronic interactions, whether electrostatic attraction to charged sites, hydrogen bonding with oxygen groups, or pi-pi stacking with aromatic regions. This conclusion was reinforced by the isotherm analysis, which examined how much dye the materials could hold as a function of equilibrium concentration.

Among the isotherm models tested, the Redlich-Peterson equation provided the best fit, with the exponent beta taking values of 0.811 for graphene oxide and 0.880 for reduced graphene oxide. Because beta lies between zero and one, the result signals that neither a purely homogeneous Langmuir surface nor a purely heterogeneous Freundlich surface applies; instead, adsorption proceeds across a heterogeneous landscape of binding sites with varying energies. The maximum experimental adsorption capacities came out at 9.99 milligrams per gram for graphene oxide and 4.80 milligrams per gram for reduced graphene oxide. The lower capacity of the reduced material reflects its diminished inventory of oxygen functional groups, even though it compensates with superior stability. For a water-treatment engineer, these numbers matter less for their absolute magnitude than for what they reveal: the chemistry of the surface, not just its area, dictates performance.

To probe the interaction at the level of individual electrons, the researchers turned to density functional theory, a quantum-chemical method that computes the electronic structure of molecules and surfaces. The calculations confirmed favorable adsorption energies and electronic interactions between the Rhodamine B molecule and both graphene oxide and reduced graphene oxide surfaces, lending theoretical support to the experimental picture of chemisorption on heterogeneous sites. Computational studies of this kind are increasingly common in adsorption research because they can distinguish between competing binding geometries and identify which functional groups contribute most to the interaction, information that is difficult to extract from bulk experiments alone. Here, the agreement between simulation and measurement strengthens confidence that the proposed mechanism is not an artifact of curve fitting.

Reusability is where many promising adsorbents stumble, since spent materials that cannot be regenerated quickly become waste themselves. Both adsorbents in this study maintained significant dye-removal activity over four consecutive adsorption-desorption cycles, with reduced graphene oxide showing enhanced stability across the repeated use. That durability, combined with the rapid equilibration times, suggests a practical pathway toward real deployment, although the authors’ data cover laboratory-scale batch experiments rather than continuous-flow systems. The modest adsorption capacities also indicate that these materials would likely be most valuable as polishing agents for low-concentration dye streams, or as components of composites, rather than as bulk sorbents for heavily contaminated industrial effluent.

Perhaps the most socially resonant finding concerns what happens after the dye is gone. The team evaluated the treated water using seed germination experiments, a standard phytotoxicity assay in which seeds are grown in the treated solution and their germination and early growth are compared against controls. Water that had been treated with the graphene-based adsorbents showed minimal harmful effects on germination, indicating that the cleanup did not merely relocate the toxicity into the water column and that the effluent could potentially be repurposed for irrigation or discharge with reduced environmental risk. Given that Rhodamine B contamination is a documented problem in regions with dense textile manufacturing, a treatment train that ends with water safe enough for plants represents a meaningful step toward circular water use.

The study, funded by the Centre of Excellence in Emerging Materials at TIET and India’s DST-PURSE program, adds to a growing body of evidence that two-dimensional carbon materials are versatile platforms for water remediation. Its particular contribution lies in the head-to-head comparison of graphene oxide and reduced graphene oxide under identical conditions, which isolates the role of surface oxygen chemistry in dye capture, and in the multi-pronged verification that spans experiment, modeling, and computation. As dye pollution continues to threaten aquatic ecosystems, the message from Patiala is that sometimes the fastest cleanup comes from the thinnest materials, and that understanding why they work is the key to making them work better.

Subject of Research: Adsorption of Rhodamine B dye from water using graphene oxide and reduced graphene oxide

Article Title: Adsorption and kinetics study on Rhodamine B removal over graphene oxide and reduced graphene oxide

Article References: Tyagi, A., Chudasama, B., & Ali, A. (2026). Adsorption and kinetics study on Rhodamine B removal over graphene oxide and reduced graphene oxide. Environmental Science and Pollution Research, 33(28), 14178-14200. https://doi.org/10.1007/s11356-026-38167-z

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38167-z

Keywords: graphene oxide, reduced graphene oxide, Rhodamine B, adsorption, water treatment, dye removal, adsorption kinetics, pseudo-second-order model, Redlich-Peterson isotherm, density functional theory, phytotoxicity, environmental remediation

Chloramphenicol is a broad-spectrum antibiotic that has become a poster child for a growing class of environmental contaminants known as active pharmaceutical ingredients. These compounds slip into rivers, lakes, and groundwater through hospital effluents, pharmaceutical plant discharges, improperly discarded medications, landfill leachate, and urban runoff. Detected universally at trace concentrations ranging from nanograms to micrograms per liter, they resist conventional treatment. Chloramphenicol is particularly worrying because of its limited biodegradability, cytotoxicity, potential to drive antimicrobial resistance, and capacity for endocrine disruption even at vanishingly low levels. Standard remedies, from biological degradation and coagulation to ozonation and activated carbon adsorption, each carry drawbacks: they can be compound-specific, energy-intensive, incomplete, or prone to generating toxic transformation products.

The core challenge, the authors note, lies in the complex physicochemical behavior of pharmaceuticals in water. Many behave as weak acids whose charge state shifts with pH, turning from neutral molecules into negatively charged species as acidity drops. That shift can trigger electrostatic repulsion between contaminant and adsorbent, gutting removal efficiency. At trace levels, weak driving forces and competition from natural organic matter and coexisting ions compound the problem. What is needed, the researchers argue, is a multifunctional, magnetically recoverable adsorbent that can grab antibiotics quickly, selectively, and repeatedly under realistic conditions.

Enter iron oxide. Magnetite, or Fe3O4, has long attracted attention in water treatment because it does double duty: it adsorbs contaminants and, thanks to its magnetic character, can be pulled out of treated water with a simple magnet, eliminating the need for filtration or centrifugation. But bare magnetic nanoparticles come with a notorious flaw. They aggregate, clumping together and sacrificing the very active surface area that makes them useful, while also being awkward to handle and reuse. Embedding them in a polymer matrix solves much of this, providing structural stability and dispersing the particles across a larger working surface.

The team’s material is a composite of polystyrene, cellulose acetate, and Fe3O4 nanoparticles, dubbed PS+CA@Fe3O4. Fabrication begins with dissolving polystyrene and cellulose acetate in warm dimethylformamide, then dispersing the nanoparticles with vigorous stirring followed by ten minutes of probe sonication to break up agglomerates. The homogeneous suspension is then electrospun: pushed through an 18-gauge needle at 1.8 milliliters per hour under a 12-kilovolt electric field toward a rotating drum collector positioned 12 centimeters away. After roughly two to two-and-a-half hours of collection and an overnight vacuum dry at 40 degrees Celsius, the result is a fluffy, cotton-like magnetic polymeric adsorbent rather than the dense membrane most electrospinning studies aim to produce.

The deliberate choice to operate at low polymer concentration is the study’s central insight. Insufficient chain entanglement means the spinning jet cannot sustain a continuous, smooth fiber, so bead-on-string morphology emerges instead. Where conventional wisdom sees failure, the researchers see function. The spherical bead domains act as localized adsorption microenvironments rich in accessible surface, while the connecting nanofibers maintain structural connectivity throughout the network. The resulting low-density, loosely packed three-dimensional architecture offers a variety of pore sites, reduced packing density, and shortened diffusion pathways, all of which accelerate mass transfer and give chloramphenicol molecules more chances to encounter active sites on the polystyrene, cellulose acetate, and magnetite components.

A battery of characterization techniques backs up the design. Field-emission scanning electron microscopy revealed the interwoven fibrous network studded with bright-contrast spots indicating well-dispersed Fe3O4. Fourier-transform infrared spectroscopy confirmed the coexistence of all three components, with a fingerprint band near 540 to 600 wavenumbers marking Fe-O stretching from embedded magnetite. X-ray diffraction showed sharp peaks matching the spinel cubic magnetite phase with no impurity phases such as maghemite or hematite, while the amorphous polymer matrix showed up only as a featureless baseline. X-ray photoelectron spectroscopy found the surface composed of roughly 90.68 percent carbon, 6.87 percent oxygen, and 2.45 percent iron, consistent with a polymer-dominated surface carrying iron-containing species. Nitrogen adsorption measurements classified the material as mesoporous, with a BET surface area of 19.36 square meters per gram, an average pore diameter of 31.36 nanometers, and a pore volume of 0.167 cubic centimeters per gram.

Two further measurements illuminate why the material works so fast. Contact angle tests showed pristine polystyrene fibers are strongly hydrophobic at 135.09 degrees, but the composite drops to 85.50 degrees, a shift the authors attribute to oxygen-containing cellulose acetate groups. That enhanced wettability lets water move freely through the structure, speeding delivery of contaminant molecules to active sites. Meanwhile, vibrating sample magnetometry recorded saturation magnetization of about 84 electromagnetic units per gram for pure Fe3O4 and about 48 for the composite, the reduction reflecting dilution by the nonmagnetic polymer. Crucially, both samples showed negligible remanence and low coercivity, a soft-magnetic, near-superparamagnetic character that means the spent adsorbent can be recovered cleanly with a magnet and will not clump together on its own.

Adsorption performance lived up to the architectural promise. In batch experiments across initial chloramphenicol concentrations of 50 to 120 parts per million, removal climbed rapidly within the first 30 to 40 minutes, reaching roughly 70 to 80 percent for all concentrations before plateauing as available sites filled. Kinetic modeling told a clear mechanistic story: the pseudo-second-order model fit superbly, with correlation coefficients between 0.9971 and 0.9997 across the full concentration range, while the pseudo-first-order model lagged behind. That pattern points to chemisorption, surface-controlled uptake governed by site availability, likely through pi-pi stacking between the aromatic rings of polystyrene and the antibiotic, hydrogen bonding between chloramphenicol’s hydroxyl and amide groups and cellulose acetate’s oxygen functionalities, and possible electrostatic interactions. Diffusion analysis with Boyd’s model suggested external film diffusion and surface adsorption jointly control the rate, with intraparticle diffusion playing a secondary role. Equilibrium data were best described by the Langmuir isotherm, indicating predominantly monolayer adsorption, with a maximum capacity of 22.42 milligrams per gram, a figure that edges out biochars, modified clays, molecularly imprinted magnetic chitosan polymers, and carbon nanotubes reported in the literature, which top out between 10 and 21.35 milligrams per gram.

The authors are candid about the limits of their evidence. The XPS analysis was survey-level and performed only on the pristine adsorbent, so the proposed molecular interactions, while chemically plausible, remain to be confirmed by post-adsorption spectroscopy, and no direct control comparison against bead-free fibers of identical composition was included. Still, the conceptual contribution stands on its own: a defect-to-function design philosophy that treats electrospinning’s morphological instability as a tunable engineering variable rather than a nuisance. The adsorbent also showed excellent reusability and stability in the study, and its magnetic recovery addresses one of the biggest practical headaches of nanoparticle-based water treatment. The researchers caution that chloramphenicol served as a single model contaminant, and that testing in mixed pharmaceutical systems, real wastewater matrices, and continuous-flow modules is the necessary next step. If those trials succeed, the lesson of this work could ripple far beyond one antibiotic: sometimes the fastest route to a better material is not eliminating the flaw, but learning what the flaw is for.

Subject of Research: Electrospun magnetic polystyrene-cellulose acetate nanofibrous adsorbents for chloramphenicol removal from water

Article Title: Exploiting electrospinning-induced bead-on-string morphology for enhanced surface accessibility and chloramphenicol adsorption onto magnetic nanofibrous adsorbents

Article References: Ranjan, R., Kullappan, M., Gumfekar, S. P., & Sabapathy, M. (2026). Exploiting electrospinning-induced bead-on-string morphology for enhanced surface accessibility and chloramphenicol adsorption onto magnetic nanofibrous adsorbents. Results in Chemistry, 31, Article 103918. https://doi.org/10.1016/j.rechem.2026.103918

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103918

Keywords: electrospinning, bead-on-string morphology, chloramphenicol, magnetic adsorbent, Fe3O4 nanoparticles, water treatment, pharmaceutical pollution, adsorption kinetics, polystyrene, cellulose acetate, nanofibers, antimicrobial resistance

The study, published in the journal Results in Engineering, was carried out by Irina Ceban, Crina Vicol and Maria Mihet, who prepared two activated carbons from walnut shells using citric acid as a mild, biodegradable modifying agent. The shells were washed, dried at 150 degrees Celsius for 24 hours, crushed and sieved, then impregnated with a 50 percent citric acid solution before thermal treatment. The researchers deliberately chose two very different processing routes: one sample, designated AC450-A, was heated to 450 degrees Celsius in air, while the second, AC600-N, was heated to 600 degrees Celsius under a flow of nitrogen. After treatment, both materials were washed to constant filtrate pH and dried, yielding two carbons with strikingly different personalities.

The central question was deceptively simple: does it pay more to preserve the oxygen-rich functional groups that citric acid installs on a carbon surface, or to build a more carbonized, thermally stable structure? Citric acid is prized in adsorbent design because it grafts carboxylic, hydroxyl and carbonyl functionalities onto carbon, creating sites that can bind metal ions through ion exchange, electrostatic attraction and surface complexation. But heat works against this chemistry. As treatment temperature rises, the carbon framework condenses and aromatizes, becoming more stable, while thermally labile oxygen groups are progressively burned off or transformed. The Moldovan team set out to quantify exactly where that balance falls.

Characterization told the story in fine detail. Elemental analysis showed carbon content climbing from 81.37 percent in AC450-A to 84.90 percent in AC600-N, while hydrogen fell from 3.92 to 2.93 percent, a signature of deeper carbonization and structural condensation. Sulphur was undetectable in both samples, confirming the purity of the walnut shell precursor. Fourier-transform infrared spectroscopy revealed the chemical consequences: the lower-temperature sample retained stronger O-H, C=O and C-O bands, indicating abundant oxygen-containing surface groups, whereas the 600-degree sample showed enhanced aromatic C=C features and diminished oxygen signals, consistent with a more condensed, carbon-rich framework.

Perhaps the most surprising finding came from nitrogen adsorption measurements. Both carbons exhibited extremely low BET surface areas, just 0.35 square metres per gram for AC450-A and 0.98 square metres per gram for AC600-N, three orders of magnitude below conventional activated carbons, which typically range from several hundred to more than 1000 square metres per gram. The isotherms were Type II-III, indicating essentially nonporous or macroporous materials with negligible microporosity. Yet both samples removed iron efficiently. This apparent paradox, a carbon with almost no measurable porosity that still captures metal ions, points squarely at surface chemistry rather than physical surface area as the dominant retention mechanism, echoing classic work by Boehm and others showing that oxygen functionalities govern metal adsorption on oxidized carbons.

The point of zero charge reinforced this picture. Using potentiometric titration under argon with sodium chloride electrolytes at three ionic strengths, the team determined pHpzc values of 3.58 for AC450-A and 2.94 for AC600-N. Below these thresholds the surfaces are protonated and positively charged; above them, carboxylic and phenolic groups deprotonate, generating negatively charged sites that attract cationic iron species. Suspension pH measurements, both below 4.0, confirmed the strongly acidic character imparted by the citric acid treatment, and scanning electron microscopy showed AC450-A as a rough, cracked, defect-rich surface while AC600-N appeared denser and more homogeneous, with EDX detecting calcium in the latter, likely concentrated from the natural mineral fraction of the shells after high-temperature carbonization.

Batch adsorption experiments across the pH 2 to 10 range revealed strongly pH-dependent behaviour. At pH 2, apparent removal was modest, roughly 5.2 milligrams per gram for AC450-A and 6.3 for AC600-N, because protonated surfaces and a flood of competing hydrogen ions shut down binding sites. As pH rose above the points of zero charge, deprotonation opened the door to electrostatic attraction and complexation. The highest apparent removal, 23 to 26 milligrams per gram for AC450-A and 27 to 31 for AC600-N, occurred at pH 9 to 10. Crucially, the authors caution that these high-pH values cannot be read as true adsorption capacities: at alkaline pH, ferrous iron hydrolyzes, and in the presence of dissolved oxygen it oxidizes to Fe(III), which precipitates as sparingly soluble hydroxides. Because no adsorbent-free precipitation blanks were run, adsorption, oxidation, hydrolysis and precipitation could not be quantitatively separated, and the results are framed honestly as overall iron removal.

Kinetic modelling added an empirical layer. The pseudo-second-order model of Ho and McKay clearly outperformed the Lagergren pseudo-first-order equation, with coefficients of determination reaching 0.997 for AC450-A and 0.999 for AC600-N, and calculated equilibrium capacities closely matching experimental values at most concentrations. The team, however, resists over-interpretation: a good fit to a pseudo-second-order equation is not proof of chemisorption, and the kinetic data were interpreted alongside the spectroscopic and surface-charge evidence rather than in isolation. Equilibrium data were fitted with four isotherm models, and the Langmuir equation won decisively, with R-squared values up to 0.998 for AC450-A and 0.999 for AC600-N. Model-derived monolayer capacities rose with temperature, from 4.47 to 6.76 milligrams per gram for AC450-A and from 4.62 to 9.27 for AC600-N between 20 and 40 degrees Celsius, and separation factors between zero and one confirmed favourable uptake across the entire concentration range.

Thermodynamics painted a nuanced picture. Gibbs free energies were negative at all three temperatures for both carbons, confirming spontaneous retention, but the van’t Hoff analysis yielded an apparent endothermic enthalpy of about +32.6 kilojoules per mole for AC450-A against a strongly exothermic -95.9 kilojoules per mole for AC600-N, with entropy changes of +207.9 and -217.2 joules per mole-kelvin respectively. With only three temperatures and limited linearity, the authors treat these numbers cautiously, refusing to assign a mechanism from them alone. The same discipline applies to the Dubinin-Radushkevich adsorption energies, which were explicitly not used to distinguish physical from chemical binding, a refreshing departure from common practice in the adsorption literature.

The broader significance of the work lies in its integrated approach and its honesty. Rather than chasing a headline capacity number, the study demonstrates that iron removal by these walnut-shell carbons is governed by a pH-dependent interplay of surface chemistry, iron speciation and thermal history, and that a carbon with almost no BET surface area can still perform meaningfully if its surface is rich in the right oxygen functionalities. The trade-off is clear: AC450-A preserves the carboxyl-rich chemistry that favours metal binding, while AC600-N gains carbonization, thermal stability and a modestly larger surface. For regions like Moldova, where walnut cultivation generates vast shell residues, the work offers a template for converting agricultural waste into water-treatment materials using a benign, food-grade acid. The authors note that model single-solute solutions were used, and that regeneration, competitive adsorption and performance in real waters remain open questions, but the foundation is laid: sometimes the smartest adsorbent is not the most porous one, but the one whose surface chemistry is preserved with care.

Subject of Research: Citric acid-modified activated carbons from walnut shells for Fe(II) adsorption from aqueous solutions

Article Title: Preparation and characterisation of citric acid-modified activated carbons for the adsorption of Fe(II) ions from aqueous solutions

Article References: Ceban, I., Vicol, C., & Mihet, M. (2026). Preparation and characterisation of citric acid-modified activated carbons for the adsorption of Fe(II) ions from aqueous solutions. Results in Engineering, 32, Article 113432. https://doi.org/10.1016/j.rineng.2026.113432

Image Credits: AI Generated

DOI: 10.1016/j.rineng.2026.113432

Keywords: activated carbon, walnut shells, citric acid modification, Fe(II) adsorption, water treatment, heavy metals, biomass valorisation, point of zero charge, Langmuir isotherm, adsorption kinetics, surface functional groups, Republic of Moldova