Steel slag can emerge from steelmaking at temperatures as high as 1,600 °C, but recovering its heat is difficult because the material is highly viscous and difficult to handle. In the roller-crushing and hot-disintegration process examined by the researchers, molten slag is first crushed and cooled in a semi-open roller-crushing area and then transferred to a closed hot-disintegration tank. Intermittent water spraying triggers exothermic hydration of free calcium and magnesium oxides, promoting internal cracking, particle-size reduction and stabilization of the slag for later use. This treatment produces saturated steam, but the study noted that a substantial portion of the high-temperature sensible heat released during crushing was not recovered.

The proposed configuration attempts to connect two stages that operate at different heat levels. Radiative heating surfaces positioned around and above the roller-crushing region recover high-temperature heat, while hot disintegration supplies saturated steam. Part of the recovered heat preheats feedwater in a water-wall economizer, and the remainder superheats the steam before it enters the turbine. A steam drum provides steam-water separation and a location for chemical dosing and bottom blowdown. The researchers modeled a direct-steam Rankine cycle because the recovered steam can serve as the cycle working fluid; this avoided the additional heat-transfer stage and separate organic-fluid loop that would be required if an organic Rankine cycle were supplied with the steam.

To evaluate the enclosure geometry, the team built a MATLAB model of diffuse-gray surfaces exchanging radiation. The radiation network represented the slag, top surface and aggregated side walls, with slag emissivity set at 0.90 and receiver emissivity at 0.80. The top and side temperatures were prescribed at 120 °C and 25 °C in the main comparison, while convection, radiation involving participating gases or particles, and direct contact heat transfer were excluded. The rectangular enclosure measured 16 by 5 by 4 metres, whereas the cylindrical design had a radius of 5.744 metres and a height of 4 metres. Both provided about 248 m² of combined top-plus-side receiver area, but they did not have identical slag footprints: the idealized slag-emitting area increased from 80 m² in the rectangle to 103.64 m² in the cylinder.

For an idealized 30,000-kilogram slag batch with a constant heat capacity of 1.2 kJ per kilogram per kelvin, the rectangular configuration had a modeled cooling-time mean radiative heat-transfer rate of 13.83 MW, compared with 17.54 MW for the cylindrical configuration. The cylinder’s result was approximately 27% higher under the prescribed surface-radiation conditions. Because the slag-emitting area and view factors changed along with the enclosure shape, this was a comparison of the selected geometries rather than an isolated view-factor gain or a matched-footprint comparison. Sensitivity calculations also showed that lowering slag emissivity from 0.90 to 0.75 reduced the mean rates to 11.66 MW for the rectangle and 14.84 MW for the cylinder. Lowering receiver emissivity from 0.80 to 0.60 changed the modeled cylinder-to-rectangle difference from 26.85% to 23.43%. These calculations describe model sensitivity, not measured uncertainty, and the effects of evolving slag surfaces, enclosure gases, dust, deposits and fouling were not quantified.

The integrated-cycle analysis used Aspen Plus V11 with IAPWS-IF97 water properties and represented the superheater, economizer, steam drum, condenser, pump and turbine. In the selected case, 10,400 kg/h of feedwater entered the flowsheet: 2,400 kg/h passed through the economizer and 8,000 kg/h entered the hot-disintegration heat-recovery section. Their modeled heat duties were 7.247 MW for hot disintegration, 0.267 MW for feedwater preheating and 2.613 MW for steam superheating, giving a total cycle heat input of 10.127 MW. Saturated steam from the drum reached 556.8 °C at 0.2 MPa before entering the expander. The model then calculated 2.068 MW of expander shaft output and a cycle thermal efficiency of 20.4%. The reported cycle power subtracts the represented feed-pump demand from expander shaft output; it is not net exported electricity because generator losses and plant auxiliaries were outside the model boundary.

A literature benchmark tested the baseline calculation without heat supplied by the crushing enclosure. At a hot-disintegration steam pressure of 0.2 MPa and a flow of 2,600 kg/h, the model generated 291.5 kW of expander shaft output, close to the reference value of approximately 300 kW and representing a deviation of about −2.8%. Its modeled efficiency was 15.5%, however, above the literature-reported range of 10–12%, a difference attributed to calculations that did not share fully equivalent component assumptions or efficiency boundaries. The comparison therefore served as a numerical benchmark rather than experimental validation of the integrated design.

The modeled superheating increased the physical exergy carried by the steam entering the expander. Specific physical exergy rose from 586 kJ/kg at 120 °C to 1,031 kJ/kg at 557 °C, an increase of 76%. As steam flow increased from 2,600 to 10,400 kg/h, the inlet-steam physical-exergy rate rose from 0.42 to 2.98 MW and modeled cycle power increased from 291.3 to 2,067.7 kW. The ratio of modeled cycle power to inlet-steam physical exergy remained near 69% in the two cases. This ratio describes conversion within the modeled cycle, not the exergy efficiency of the complete slag-recovery system, because losses in individual recovery sections, slag exergy, generator losses and auxiliary inputs were not included.

Intermittent steam production remains unresolved. Hot disintegration depends on periodic spraying and hydration reactions, whereas the thermodynamic model assumes a steady, time-averaged supply and does not resolve batch-scale transients or water accumulation in the drum. A simplified estimate for a drum containing 20,000 kg of water at 0.2 MPa suggested a characteristic buffering time of approximately 118 seconds, or about two minutes, during an allowable transient pressure decrease to 0.15 MPa. That estimate does not demonstrate that one drum could smooth a complete batch of intermittent production. Staggered operation of multiple hot-disintegration tanks was proposed as a possible way to reduce aggregate flow fluctuations, but measured single-tank steam profiles and plant scheduling records were unavailable, so the arrangement remains an operating assumption. A preliminary cost screen estimated the added equipment at RMB 4.5 million and compared it with an indicative annual electricity value of about RMB 5.33 million at 6,000 operating hours and RMB 0.50/kWh. The resulting ratio of roughly one year is not a definitive payback because installation, civil work, generator and auxiliary consumption, maintenance, downtime, financing, taxation and electricity-price changes were excluded.

Water chemistry presents a separate constraint. Condensate collected from hot-disintegration steam at Henan Jiyuan Iron and Steel Group in China initially contained total calcium and magnesium concentrations of 1.18 and 0.80 mmol/L. In the proof-of-concept dosage series, adding sodium phosphate caused calcium and magnesium to decline sharply before varying non-monotonically. At a sodium phosphate dosage of 5.53 mmol/L, total calcium and magnesium measured 0.009 and 0.085 mmol/L, and equivalent hardness reached 0.188 ± 0.011 mmol/L, 95.2% below the untreated value of 3.944 mmol/L. Visual MINTEQ equilibrium simulations at 15 °C reproduced the general concentration trend and identified hydroxyapatite and magnesium phosphate as possible precipitating solids, but the calculations assumed chemical equilibrium and did not resolve nucleation or precipitation kinetics. Together, the radiation and cycle models and the preliminary water tests support the feasibility of the proposed integration under the studied conditions. They do not establish continuous turbine operation, industrial-scale hardness compliance or long-term chemical stability, which require dynamic pilot testing, independent treatment replicates, long-term scaling studies and validation of turbine control, blowdown, steam purity and auxiliary power.

Subject of Research: Modeled steel-slag waste-heat recovery and preliminary phosphate treatment for Rankine-cycle power generation

Article Title: An integrated waste heat recovery system for Rankine cycle power generation from the steel slag hot disintegration process

Article References: Wu, H., Zhou, T., Bai, R., Xu, Z., Li, Y., Xia, B., Zhang, M., & Yang, H. (2026). An integrated waste heat recovery system for Rankine cycle power generation from the steel slag hot disintegration process. Frontiers in Energy Research, 14, Article 1965673. https://doi.org/10.3389/fenrg.2026.1965673

Image Credits: AI Generated

DOI: 10.3389/fenrg.2026.1965673

Keywords: steel slag, waste-heat recovery, Rankine cycle, hot disintegration, radiative heat transfer, steam superheating, power generation, water hardness, phosphate treatment, steel industry, integrated, waste

The disaster, known as the Kyshtym accident, remains the second most serious radiation catastrophe in history after Chernobyl in 1986. A decade later, in 1987, the improper disposal of a radiotherapy source in Goiânia, Brazil, released cesium-137 into the environment in what became another sobering reminder of the risks of cesium contamination. These events underscore why understanding the chemistry of cesium in solution is not an academic exercise but a matter of environmental protection.

Long-term safety assessment of a radioactive waste repository requires evidence that all relevant chemical processes are known and understood, and that initiated reactions will not lead to an undue release of radionuclides into the geosphere, hydrosphere, or biosphere. One key parameter for assessing the propagation of a radionuclide is its solubility in solutions interacting with the waste. Because disposal is a task encompassing decades, the thermodynamic database underpinning these assessments must operate reliably on a long-term basis.

Extensive databases based on the Pitzer ion interaction model were developed within the Yucca Mountain Project, the THEREDA project, and the ANDRA project, but many of the Pitzer models in these databases for cesium systems are concentration restricted and cannot correctly describe solid-liquid equilibrium in the geochemical and industrial systems of interest for nuclear waste programs. The Pitzer approach, introduced in 1973, represents a significant advance in physical chemistry that has facilitated the construction of accurate computer thermodynamic models for electrolyte solutions. According to Pitzer theory, electrolytes are completely dissociated, and in solution only ions interact with one another.

Two kinds of interactions are observed: a specific Coulomb interaction between distant ions of opposite signs, described by equations of the Debye-Hückel type, and nonspecific short-range interactions between two and three ions, captured by binary parameters of ionic interaction. For mixed ternary systems, the model additionally requires mixing parameters for unlike cation-cation or anion-anion pairs and for triple ion interactions where the ions are not all of the same sign. The elegance of the approach is that these few parameters, once evaluated against experimental data, allow accurate predictions of activities and solubilities across enormous concentration ranges.

To parameterize the new models, the researchers used all available experimental osmotic coefficient data for the whole concentration range of solutions, up to saturation. For the cesium fluoride-water system, raw data at low molality from Hamer and Wu and from Mikulin, together with extrapolated data, were used, and it was established that an extended approach with four parameters — including the beta-two term — and variation of the alpha-one and alpha-two terms leads to the lowest standard model-experiment deviation. For cesium hydroxide-water and cesium sulfate-water, a standard approach with three interaction parameters sufficed.

The team also rigorously tested previously developed Pitzer-based models for five other cesium binary systems — cesium chloride, cesium bromide, cesium iodide, cesium nitrate, and cesium selenate in water — by comparison with experimental osmotic coefficients and recommended activity coefficients. The models giving the best agreement from low to high concentration up to saturation were accepted as correct models for solubility calculations. On the basis of these evaluated parameters, the researchers determined the thermodynamic solubility products and the Deliquescence Relative Humidity of eight cesium solid phases, from cesium fluoride to cesium selenate.

The DRH predictions showed excellent agreement with experimental data determined using the isopiestic method. Beyond binary systems, the study summarized solid-liquid equilibrium models for fifteen cesium mixed ternary systems, pairing cesium salts with magnesium, nickel, manganese, cobalt, copper, and zinc salts in common-anion solutions, as well as mixed cesium-rubidium and cesium-bromide systems. The validated binary parameterizations were used without adjustment to develop the mixed-system models, with mixing parameters evaluated using the solubility approach based on experimental compositions of saturated ternary solutions.

For systems with precipitation of solid solutions, such as cesium chloride-cesium bromide-water, parameters were calculated using the Zdanovskii rule. Carnallite-type minerals of the form MX.MgX2.6H2O, which can incorporate cesium, are interesting not only as natural sources of chemical compounds but also for renewable thermochemical energy storage, since their hydration reactions are exothermic.

Subject of Research: Development of accurate chemical thermodynamic database for geochemical storage of nuclear waste. Part III: Models for predicting solution properties and solid-liquid equilibrium in cesium binary and mixed systems

Article Title: Development of accurate chemical thermodynamic database for geochemical storage of nuclear waste. Part III: Models for predicting solution properties and solid-liquid equilibrium in cesium binary and mixed systems

Article References: Tsenov, T., Donchev, S., & Christov, C. (2022). Development of accurate chemical thermodynamic database for geochemical storage of nuclear waste. Part III: Models for predicting solution properties and solid-liquid equilibrium in cesium binary and mixed systems. BioRisk, 17, 407-422. https://doi.org/10.3897/biorisk.17.77523

Image Credits: AI Generated

DOI: 10.3897/biorisk.17.77523

Keywords: Development, accurate, chemical, thermodynamic, database, geochemical, storage, nuclear, waste, Part, Models, predicting

Because okara is generally considered a soybean-processing waste stream but retains a significant protein component, the researchers treated it as a potential source of biologically active molecules. They broke its proteins into short chains of amino acids through hydrolysis, creating an okara hydrolysate rich in bioactive peptides. The team then evaluated the hydrolysate in vitro using human dermal fibroblasts, cells that contribute to maintaining skin structure and participate in tissue-repair processes. In this cell-based system, the hydrolysate showed antioxidant and anti-inflammatory activity and encouraged fibroblast migration.

The researchers incorporated the okara hydrolysate into PCL to translate the cellular observations into a printable material. Mechanical, thermal and structural analyses indicated that adding the hydrolysate preserved the principal properties of PCL, while the blend supported the extended release of bioactive peptides over time. After fabrication, the printed composite continued to show antioxidant, anti-inflammatory and pro-regenerative features in laboratory testing. It could also be formed into structures with complex geometries, supporting the technical feasibility of using additive manufacturing to produce custom-shaped biomedical products. However, the study did not test a completed wound-care device, healing in people, or performance within living tissue.

The work forms part of the European Union-funded 3DBioPad project, which aims to design and 3D print a biocompatible, bioactive pad for the topical treatment of pain associated with breastfeeding and recovery after breast cancer surgery. Carmen Lammi, a professor at the University of Milan’s Department of Pharmaceutical Sciences, coordinated the interdisciplinary research with Serena Graziosi, a professor in Politecnico di Milano’s Department of Mechanical Engineering, and Raffaele Pugliese, a researcher at the NeMo Lab Research Center at Niguarda Hospital. The project combines pharmaceutical and food science with mechanical design, materials engineering, product design and additive manufacturing, with the broader aim of valorizing a food-industry by-product while developing potential biomedical solutions.

As a materials-development and in-vitro proof of concept, the study shows that peptides extracted from soybean-processing residue can be incorporated into a biodegradable PCL composite without eliminating the polymer’s main properties, and that measurable biological activities can remain after printing. The researchers said they would next produce a biomimetic phantom, an experimental model intended to reproduce some characteristics of breast skin tissue, so the material could be studied under controlled conditions before subsequent validation phases. Until those steps and clinical evaluation occur, the results should not be interpreted as evidence that the composite effectively treats skin wounds, breastfeeding pain or post-surgical pain. Its demonstrated value lies in a laboratory-stage method for producing customizable, biologically active and potentially sustainable materials for future biomedical applications.

Subject of Research: Experimental development of a 3D-printable soybean-okara peptide composite for wound-care applications.

Article Title: From soybean waste to 3D printing: A new biomaterial for skin repair

Article References: From soybean waste to 3D printing: A new biomaterial for skin repair. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: soybean okara, bioactive peptides, 3D printing, wound care, polycaprolactone, dermal fibroblasts, biodegradable materials, food-waste valorization, in-vitro research, soybean, waste, printing

The central challenge is that biomass is not a uniform feedstock. Agricultural residues and other plant materials can contain different proportions of cellulose, hemicellulose, lignin, minerals, and moisture, even when they appear similar. Their particle size and internal structure can also differ. During carbonization, these variations influence how the material decomposes and reorganizes, potentially producing differences in pore networks, surface chemistry, carbon ordering, electrical properties, and transport pathways. As corresponding author Yaning Zhang explained in the news release, “Biomass is not a uniform raw material. Even seemingly similar agricultural residues can behave very differently during carbonization.” The finding suggests that feedstock selection cannot be separated from the performance target: materials intended for supercapacitors, rechargeable batteries, carbon capture, catalysis, or contaminant removal may require different combinations of structure and chemical functionality.

Microwave-assisted pyrolysis is highlighted as a promising approach because microwaves can transfer energy directly into suitable materials. The review reports that this heating method may shorten processing times and improve control over carbon formation compared with conventional heating. The source also cautions against treating the technology as a complete solution. Uneven energy absorption, localized overheating, and variations among reactor designs can lead to inconsistent results. Reliable scale-up would therefore require careful temperature monitoring, accurate energy measurements, and standardized processing conditions. The review does not establish that microwave processing outperforms conventional heating in every application or provide a universally optimal production method; instead, it frames the approach as one part of a broader strategy for controlling material properties.

The analysis also finds that maximizing surface area alone does not guarantee high performance. Accessible pores, useful chemical groups, orderly carbon structures, and pathways that permit movement of charge or other substances must be matched to the intended application. A material with a large internal surface can still underperform if its pores are poorly connected or if its chemistry does not support the relevant reaction. The review’s integrated framework consequently connects four stages: the original feedstock, the manufacturing process, the structure and chemistry of the resulting carbon material, and the behavior required in an application. This relationship offers researchers a more structured alternative to trial-and-error development and could help them identify which precursor and processing combinations are most likely to meet a specified goal.

To improve reproducibility, the authors propose standardized methods for characterizing biomass and reporting experimental conditions. They further recommend combining detailed material measurements with machine learning and data-driven modeling, which may reveal relationships that conventional experimental approaches overlook. These recommendations are not presented as a validated predictive model, and the review does not report new machine-learning performance data. It instead argues that more consistent feedstock descriptions, processing records, and structural measurements could make results from different studies more comparable and more useful for designing carbon nanomaterials. Industrial assessment must also include production costs, energy consumption, and environmental impacts, because a laboratory material that cannot be manufactured reliably or sustainably may not be commercially viable. Taken together, the review presents a roadmap for developing biomass-derived carbon materials, but it does not demonstrate commercial deployment, clinical benefits, or a guaranteed improvement in any specific energy or environmental application.

Subject of Research: How biomass feedstock variability affects the structure and performance of biochar-based carbon nanomaterials

Article Title: From agricultural waste to advanced carbon materials: Scientists reveal why the starting material matters

Article References: From agricultural waste to advanced carbon materials: Scientists reveal why the starting material matters. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: biomass, biochar, carbon nanomaterials, agricultural waste, microwave pyrolysis, carbonization, energy storage, carbon capture, materials characterization, machine learning, agricultural, waste

The choice of lanthanum oxide is deliberate and somewhat contrarian. Silver and copper nanoparticles have dominated agricultural antimicrobial research because they kill microbes through ion release and reactive oxygen species generation, but they carry documented drawbacks: high production cost, phytotoxicity at elevated concentrations, and concerns over bioaccumulation in soil microbiota and aquatic organisms. Zinc oxide and copper oxide nanoparticles offer lower cost but raise similar dose-dependent toxicity worries, while titanium dioxide nanoparticles depend on ultraviolet activation that field conditions cannot guarantee. Lanthanum oxide, a rare-earth oxide that has received comparatively little attention as a direct biocontrol agent, combines high chemical stability with a wide bandgap suited to sustained oxidative activity, and comparative studies suggest lanthanum-based compounds generally show lower cytotoxicity and reduced bioaccumulation than their silver or copper counterparts at equivalent antimicrobial concentrations. The authors note, however, that the environmental fate and long-term ecotoxicological impact of lanthanum oxide nanoparticles at agricultural scales remain active areas of investigation that have not been fully characterized for green-synthesized formulations.

The synthesis itself reads like a chemistry lesson in valorized waste. Orange peels collected from a campus canteen were chopped, dried at 40 degrees Celsius, and ground into powder, then steeped in distilled water at 60 degrees Celsius for 15 minutes to release the peel’s rich phytochemical cargo. The filtered extract was combined with a 0.1 molar lanthanum nitrate solution and stirred for three hours at 50 degrees Celsius while the pH was raised to 10 with sodium hydroxide. The dark yellow solution progressively paled as electron-donating polyphenols and hydroxyl-rich phenolic compounds reduced lanthanum(III) ions, and centrifugation yielded a tan pellet corresponding to a lanthanum hydroxide intermediate. Drying at 70 degrees Celsius shifted the material to bright yellow, and a final calcination at 700 degrees Celsius for three hours converted the intermediate into a white powder, the characteristic appearance of pure lanthanum oxide. The entire colorimetric sequence tracks the expected reaction pathway from metal salt to hydroxide intermediate to crystalline oxide, with plant polyphenols serving as natural reducing and capping agents in place of hazardous chemicals such as sodium borohydride or hydrazine.

Characterization confirmed that the plant-mediated route produced a highly crystalline, phase-pure material. Powder X-ray diffraction displayed sharp, well-defined Bragg peaks at 2-theta values of 26.1, 29.9, 39.5, and 48.7 degrees, matching the (100), (101), (102), and (110) reflection planes of cubic lanthanum oxide and aligning with the ICDD reference standard JCPDS No. 00-050-0193. The authors point out that achieving comparable crystallinity through some chemical routes would require harsher conditions, suggesting plant polyphenols broadly support efficient crystalline oxide formation. Ultraviolet-visible spectroscopy revealed a strong absorption peak at approximately 360 nanometers, consistent with literature values for lanthanum oxide nanoparticles synthesized by other green routes, alongside a broad shoulder between 290 and 320 nanometers most plausibly attributed to residual flavonoids from the orange peel extract. Minimal absorbance across the visible region confirmed the wide-bandgap semiconductor behavior typical of the oxide, meaning any photocatalytic response would occur predominantly under ultraviolet excitation.

Field-emission scanning electron microscopy revealed an irregular, flake-like to quasi-spherical morphology rather than the uniform spheres reported in prior green syntheses using other plant extracts, a heterogeneity the researchers attribute to differences in extraction solvent, extract concentration, and synthesis pH that shape nucleation and growth kinetics. The particles aggregated appreciably into clusters, a consequence of the high surface energy of nanoscale materials and the presence of residual phytochemical components acting as stabilizing interfaces between adjacent particles without fully preventing agglomeration. Energy-dispersive X-ray spectroscopy confirmed the elemental composition as 47.4 weight percent lanthanum, 35.9 weight percent oxygen, and 16.7 weight percent carbon, with no peaks corresponding to any other elements, indicating the sample was free of extraneous contamination. The substantial carbon content, together with the deviation of the measured lanthanum-to-oxygen ratio from the theoretical stoichiometric value for pure lanthanum oxide, provides direct quantitative evidence for a retained organic surface layer, a common observation in green-synthesized nanoparticles that reflects both the inherent limitations of EDX for quantifying light elements and the diluting effect of the bio-capping coating on the inorganic signal.

Fourier-transform infrared spectroscopy told a similar story of partial organic retention. The orange peel extract spectrum displayed bands characteristic of its phytochemical constituents: hydroxyl stretching at 3740 and 3336 reciprocal centimeters from free and hydrogen-bonded phenolic and polysaccharide groups, aliphatic C-H stretching at 2924, carbonyl C=O stretching at 1735, aromatic C=C stretching at 1604 characteristic of flavonoid and polyphenolic structures, and C-O-containing linkages at 1245 and 1018. The nanoparticle spectrum showed a markedly simplified profile consistent with thermal decomposition of most organic constituents during calcination, yet it retained O-H bands at 3740 and 3440, residual C-O-related bands at 1380 and 1070, and, most notably, three new absorption bands at 890, 620, and 460 reciprocal centimeters, all attributed to lanthanum-oxygen stretching vibrations. The persistence of the 3740 band in both spectra suggests this specific hydroxyl environment survives thermal treatment largely intact, and the combined FTIR and EDX evidence supports a bio-hybrid nanostructure model in which an inorganic oxide core retains a residual organic surface coating of plant-derived secondary metabolites.

Antifungal testing using the poisoned food technique produced the study’s most striking results. Nanoparticle suspensions at 1, 5, and 15 milligrams per milliliter were incorporated into potato dextrose agar, and 5-millimeter mycelial discs from 7-day-old cultures of Alternaria solani and Colletotrichum capsici were placed at the center of each plate, with three replicates per treatment and colony diameter measured at 24-hour intervals for 7 days. Against A. solani, the tomato early blight pathogen, the nanoparticles achieved complete suppression of mycelial growth at both 5 and 15 milligrams per milliliter, exactly matching the performance of the commercial SAAF fungicide (carbendazim 12 percent plus mancozeb 63 percent) at 5 milligrams per milliliter. Even at the lowest concentration of 1 milligram per milliliter, the particles restricted mycelial expansion by 24.4 percent. Against C. capsici, the chili anthracnose pathogen, inhibition rose stepwise from 9.9 percent at 1 milligram per milliliter to 61.5 percent at 5 and a substantial 86.8 percent at 15, though only the commercial fungicide achieved complete growth restriction. One-way analysis of variance confirmed the overall treatment effects were statistically highly significant for both pathogens.

The kinetic dimension may prove as important as the final efficacy. Against A. solani, the nanoparticles at 15 milligrams per milliliter achieved complete inhibition two days earlier than the commercial fungicide at 5 milligrams per milliliter, on day 2 rather than day 4. While both treatments ultimately reached 100 percent inhibition, the authors argue that more rapid early-stage growth arrest during the critical infection window is expected to limit disease severity and associated yield loss under field conditions. Equally notable was the complete suppression of sporulation observed across all lanthanum oxide-treated plates for both pathogens, an effect that extends beyond simple growth restriction, since spore production is central to secondary disease spread in field conditions. The pathogen-specific difference in susceptibility is most plausibly explained by fungal cell wall architecture: A. solani possesses relatively thin, loosely organized cell walls composed primarily of glucans and chitin with minimal melanization, permitting greater nanoparticle penetration and exposure to reactive oxygen species, whereas Colletotrichum species bear thicker, more heavily melanized cell walls, and melanin is a recognized scavenger of reactive oxygen species that would reduce the bioavailability of nanoparticle-induced oxidative stress at the cell surface and confer partial resistance.

The retained phytochemical layer may itself contribute an independent antifungal component alongside the oxidative and cell-wall-disruptive mechanisms attributed to the inorganic core. Recent work has shown that Citrus limon and Citrus sinensis peel extracts alone suppress potato rot-causing fungal pathogens through their phytochemical content, supporting the rationale that the surface-bound organic layer identified by FTIR and EDX in this study may act in parallel with the oxide’s own bioactivity. This dual-mechanism perspective, in which the antifungal effect derives from both the inorganic oxide core and the retained organic phytoconstituents, is not explicitly addressed in comparable prior green-synthesis lanthanum oxide studies and distinguishes the present work, which the authors describe as the first to synthesize lanthanum oxide nanoparticles specifically from orange peel extract and to test them against these two economically important pathogens.

The findings position peel-derived lanthanum oxide nanoparticles as a promising eco-friendly biocontrol candidate, particularly for managing early blight, while acknowledging that further optimization, whether through higher application concentrations, extended exposure times, or combination with complementary antifungal agents, may be required to achieve comparable efficacy against more resistant pathogens such as C. capsici. The researchers also emphasize that evaluation against a broader collection of phytopathogenic fungi representing different taxonomic groups and host crops will be necessary to establish the generality and spectrum of the observed activity, and that dedicated investigation of environmental fate and ecotoxicological impact at agricultural application scales must precede any large-scale field deployment. Still, by converting an abundant agricultural waste stream, with global orange production exceeding 50 million metric tons annually, into a functional antifungal nanomaterial with a comparatively favorable toxicological profile, the study contributes both a practical waste-to-value pathway and new pathogen-specific efficacy data to the emerging field of rare-earth-oxide green nanotechnology in agriculture.

Subject of Research: Biogenic synthesis and characterization of lanthanum oxide nanoparticles using citrus sinensis peel waste for antifungal applications in crop protection

Article Title: Biogenic synthesis and characterization of lanthanum oxide nanoparticles using citrus sinensis peel waste for antifungal applications in crop protection

Article References: Ramesh, S., Khyathi, A., Mandapati, H. S., S., V., Kumar, V., & Parthasarathi, T. (2026). Biogenic synthesis and characterization of lanthanum oxide nanoparticles using citrus sinensis peel waste for antifungal applications in crop protection. Frontiers in Fungal Biology, 7, Article 1925291. https://doi.org/10.3389/ffunb.2026.1925291

Image Credits: AI Generated

DOI: 10.3389/ffunb.2026.1925291

Keywords: Biogenic, synthesis, characterization, lanthanum, oxide, nanoparticles, citrus, sinensis, peel, waste, antifungal, applications

Biochar is not a new idea. Its origins trace back to the ancient Amazonian Terra Preta soils, where indigenous populations deliberately incorporated charred organic matter into infertile ground to boost fertility and agricultural productivity. Those soils contained stable carbon compounds and showed remarkable nutrient retention and microbial activity compared with surrounding earth, demonstrating centuries ago what modern science now confirms: carbonized biomass can persist in soil for decades to centuries while continuously improving its properties. Today, researchers at institutions including Ganpat University in India are systematically cataloging how this ancient practice can be scaled into industrial climate technology, examining everything from feedstock chemistry to reactor design and carbon market economics.

The technical appeal of biochar lies in its structure. Produced mainly through pyrolysis—the thermochemical decomposition of biomass at temperatures between 300 and 700 degrees Celsius in the absence of oxygen—biochar develops a highly porous architecture with extensive surface area and abundant surface functional groups, including hydroxyl, carboxyl, ketonic carbon, and phenolic groups. These features give the material exceptional adsorption capacity, high cation exchange ability, and prolonged carbon storage. Certain biochars can absorb water up to 400 percent of their own weight thanks to hydrophilic pore networks and irregular particle structures. The three main components of plant biomass—cellulose, hemicellulose, and lignin—each decompose at different temperature ranges during pyrolysis, and their proportions in the feedstock strongly govern the porosity, aromaticity, and stability of the resulting char. Lignin-rich woody biomass, for example, produces biochar with higher fixed carbon content and superior thermal stability because its cross-linked aromatic structure resists microbial degradation and oxidation.

Pyrolysis itself has evolved into a family of technologies, each with distinct trade-offs. Slow pyrolysis, operating between 300 and 550 degrees Celsius with heating rates of just 0.1 to 1 degree Celsius per second and residence times of minutes to hours, maximizes biochar yield at 30 to 50 percent by weight, making it the preferred route for carbon sequestration. Fast pyrolysis, by contrast, uses very high heating rates and vapor residence times under five seconds at 400 to 600 degrees Celsius to produce 50 to 75 percent bio-oil, the renewable liquid fuel, with only 10 to 20 percent char. Flash pyrolysis pushes temperatures to 600 to 1,400 degrees Celsius with heating rates exceeding 1,000 degrees per second, while microwave-assisted pyrolysis generates heat directly within the biomass through electromagnetic interaction with molecular dipoles, enabling uniform volumetric heating that can handle wet feedstocks without extensive pre-drying. Microwave-derived biochars have achieved surface areas of 450 to 800 square meters per gram, rivaling commercial activated carbons. Vacuum pyrolysis, carried out under reduced pressure, suppresses oxidation and secondary cracking to yield bio-oil with heating values between 22.4 and 40 megajoules per kilogram alongside carbon-rich char.

Feedstock selection is equally decisive. Agricultural residues such as rice husk, wheat straw, and corn stover are inexpensive and abundant but carry moderate to high ash content—rice husk is particularly rich in silica, which can block active surface sites and reduce adsorption efficiency. Forestry biomass like sawdust, bark, and wood chips contains high lignin and fixed carbon, producing low-ash, carbon-dense biochar with excellent stability, though collection and transportation from dispersed forest regions raise operational costs. Food and kitchen waste, including fruit peels and spent coffee grounds, offers continuous availability at very low cost but requires pre-drying because of high moisture content. Animal-derived wastes such as poultry litter, cow dung, and pig manure are rich in nitrogen, phosphorus, and minerals, yielding nutrient-enriched biochar valuable for phosphorus recovery, but they also generate high ash levels and may contain antibiotics, pathogens, and heavy metals that demand careful quality monitoring before land application.

The climate mathematics are striking. Large-scale studies on olive tree pruning residues in Spain demonstrated that an optimized pyrolysis plant processing 6.5 tonnes of biomass per hour was energy self-sufficient and capable of permanently removing around 2.68 tonnes of carbon dioxide equivalent per tonne of biochar produced, with annual carbon removal potential reaching approximately 24,450 tonnes. Country-level assessments in China showed that more than 920 kilograms of carbon dioxide equivalent could be sequestered from every tonne of crop residue converted to biochar, with national sequestration potential estimated at 0.50 petagrams of carbon dioxide equivalent annually. Potassium-enriched biochar has been shown to increase carbon storage potential by up to 45 percent. Field experiments applying biochar at rates around 30 tonnes per hectare significantly lowered carbon dioxide, methane, and nitrous oxide emissions while enhancing soil carbon sequestration and corn yields. The mechanism is elegant: pyrolysis converts labile biomass carbon into highly stable polyaromatic carbon networks with low hydrogen-to-carbon and oxygen-to-carbon ratios that resist microbial decomposition for decades to centuries.

Biochar also acts on greenhouse gases through soil microbial pathways. Meta-analytical evidence from studies conducted between 2000 and 2024 shows that biochar application increases the abundance of amoA and nosZ functional genes while reducing nirS gene abundance, producing a notable decline in nitrous oxide emissions. Improved soil aeration and oxygen diffusion suppress the anaerobic conditions that favor methane-producing methanogenic microorganisms, while biochar surfaces provide habitats for methane-oxidizing bacteria. Biochar raises soil pH and stimulates microorganisms carrying the nosZ gene, enhancing the conversion of nitrous oxide to harmless nitrogen gas during denitrification. It further adsorbs ammonium and nitrate ions, reducing nitrogen losses and limiting substrates available for nitrous oxide formation. Emission reductions were particularly effective when biochar and nitrogen fertilizer were applied at moderate rates, with stronger methane mitigation observed in warmer southern paddy systems and greater nitrous oxide reduction in cooler northern regions affected by freeze-thaw cycles.

Beyond agriculture, biochar is emerging as a low-cost adsorbent for wastewater treatment. Sewage-sludge biochar produced through pyrolysis demonstrated a DNA adsorption capacity of 1 milligram per gram, five times higher than iron-oxide-coated sand, with removal efficiencies of 85 percent for antibiotic resistance genes and 97 percent for total environmental DNA. Date palm biochar prepared at 600 degrees Celsius achieved 64 percent phenol removal with an adsorption capacity of 15.93 milligrams per gram. The material removes contaminants through adsorption, ion exchange, pore filling, electrostatic attraction, surface complexation, and precipitation, with oxygen-containing functional groups forming complexes with heavy metal ions including lead, cadmium, copper, and chromium. Modified biochars containing iron oxides, magnetic nanoparticles, or nitrogen functional groups exhibit improved adsorption capacity through additional catalytic and redox reactions, and the material also serves as a support matrix for biofilm development that enhances microbial degradation of organic pollutants.

The review is candid about risks. Biochar produced from contaminated feedstocks such as sewage sludge, animal manure, and municipal biosolids may concentrate heavy metals including cadmium, lead, chromium, nickel, copper, zinc, and arsenic during pyrolysis, because organic matter is volatilized while inorganic elements remain in the solid fraction. Low-temperature or incomplete pyrolysis can increase the formation and retention of polycyclic aromatic hydrocarbons, dioxins, and pharmaceutical residues, while manure-derived biochar may contain veterinary antibiotics and high salt levels that harm soil microorganisms if applied excessively. High levels of toxic PAHs are mainly associated with poor reactor design, uneven heating, and vapor condensation rather than feedstock type alone, meaning proper process control can significantly reduce contamination. The review proposes a comprehensive quality framework spanning feedstock characterization, pretreatment, pyrolysis process control, leaching tests, ecotoxicological evaluation, certification against international biochar standards, and long-term field monitoring before large-scale deployment.

Looking ahead, the review envisions future biochar systems integrating artificial intelligence, machine learning, and Internet of Things technologies to optimize process control and industrial scalability, alongside co-pyrolysis, microwave-assisted modification, life cycle assessment, and techno-economic analysis to improve efficiency and sustainability. Economic opportunities through carbon trading systems, subsidies, and reduced dependence on fertilizers and irrigation inputs may further encourage large-scale adoption. The authors caution that biochar is not a universal solution—its effectiveness is highly site-specific, influenced by feedstock composition, pyrolysis conditions, aging behavior, and soil interactions, and adverse effects on soil microorganisms, earthworms, and crop growth have been reported under certain conditions. Greater collaboration among researchers, policymakers, industries, and farmers will be essential to establish transparent carbon policies and strengthen international cooperation. If those challenges can be met, the ancient practice of burying charred biomass in soil may become one of the most scalable carbon-negative technologies available, transforming the world’s waste streams into valuable resources while accelerating global climate neutrality goals.

Subject of Research: From biowaste to biochar: sustainable pathways for waste valorization, environmental benefits, and practical uses

Article Title: From biowaste to biochar: sustainable pathways for waste valorization, environmental benefits, and practical uses

Article References: Kumar, Y. (2026). From biowaste to biochar: sustainable pathways for waste valorization, environmental benefits, and practical uses. Frontiers in Environmental Engineering, 5, Article 1890725. https://doi.org/10.3389/fenve.2026.1890725

Image Credits: AI Generated

DOI: 10.3389/fenve.2026.1890725

Keywords: biowaste, biochar, sustainable, pathways, waste, valorization, environmental, benefits, practical, uses, scientific research

Switzerland’s approach stands out internationally. While most European countries plan to bury only their intermediate-level waste and keep low-level waste in surface or near-surface facilities — trenches, concrete vaults, or aboveground mounds — Swiss federal law demands that all radioactive waste go into a deep geological repository. The reasoning is rooted in a principle of intergenerational fairness: the protection of humans and the environment must be guaranteed in the long term without imposing unreasonable burdens on future generations. Once the repository is closed, no monitoring, maintenance, or repair may be required. That is a tall order when some of the waste contains long-lived radionuclides such as chlorine-36, which is why Swiss regulators require a safety demonstration stretching to one million years.

The provisional design reads like a blueprint for passive self-destruction of the barriers’ weaknesses — in the best possible sense. Waste from nuclear power plant operations and dismantling, along with material from research, medicine, and industry, is first conditioned in cementitious matrices inside 100 to 200 litre drums. These drums are packed into concrete containers, which are then stacked in dead-end emplacement caverns up to 250 metres long and roughly 11 metres in diameter. Every void between containers and cavern wall is backfilled with a deliberately porous mortar known as M1, made from uniformly sized aggregate bound by a strictly limited quantity of cement. The trick is that the cement paste is too sparse to fill the gaps between grains, leaving a coarse, gas-permeable pore network that can store and release gas while the grain-supported skeleton keeps the tunnels from converging once the rock support eventually degrades.

Sealing the system is an engineering feat in itself. Each cavern is closed with a gas-permeable but water-limiting seal built from an 80:20 sand-bentonite mixture, placed in direct contact with the Opalinus Clay after partial removal of the rock support. The sand grains form a rigid support matrix that carries external stresses, while the saturated bentonite swells to fill the pore space within that skeleton, creating a low gas entry pressure so gas can escape into the operational tunnels without building dangerous pressures. A transition layer of calcareous aggregates — chosen because they sit in chemical equilibrium with both cement and clay — prevents pore clogging at the interfaces, and a low-pH concrete abutment mechanically stabilizes the whole sealing section while guarding against accidental flooding and human intrusion.

But the real magic of the Swiss concept lies in its chemistry. Cementitious materials dominate the near field, and their defining property is the ability to maintain a high-pH porewater environment. Freshly hydrated cement produces porewater with a pH above 13, buffered by dissolved alkali hydroxides. As the cement ages through what the researchers describe as degradation stages, the mineral portlandite takes over as a chemical buffer, holding the pH above 12.5. Only when portlandite is fully exhausted does the pH drift down toward about 10, governed by the incongruent dissolution of calcium-silicate-hydrate phases, the C-S-H minerals that give cement its fabric and serve as the key phase for radionuclide sorption in Nagra’s safety assessment. This alkaline environment is a chemical fortress: it promotes the passivation of metal surfaces, keeping steel corrosion rates slow and gas generation correspondingly low, while simultaneously limiting the degradation of organic materials and suppressing microbial activity.

Here the story takes an unexpected turn — into the physics of water scarcity. Every chemical reaction that degrades the repository, from metal corrosion to organic breakdown to pozzolanic reactions, requires water. And Opalinus Clay is extraordinarily stingy with it. Because of the host rock’s low permeability, the emplacement caverns are expected to remain only partially saturated for several hundreds of thousands of years. The saturation history of the repository becomes the master variable controlling its chemical evolution. Water that does accumulate tends to pool at the bottom of the caverns, driven by gravity and the low capillary strength of the coarse backfill mortar, whose dominant pore sizes range from sub-millimetre to a few millimetres. The container concrete, by contrast, has much higher capillarity and will saturate first, particularly in the bottom row of containers, where reinforcement corrosion will eventually cause spalling and disintegration.

The capillary contrast between materials creates a subtle equilibrium that works in the repository’s favour. When two partially saturated porous materials with different water retention curves are in contact, suction equalizes at their interface, and the material with higher capillary strength draws in more water. This means very limited water transfer occurs from the saturated container walls toward the drier container infill mortar, at least for a long time. Even more striking, once the gas pressure generated inside the cavern reaches hydrostatic conditions, further inflow of water from the Opalinus Clay is physically prevented — a self-regulating mechanism that helps maintain partially saturated conditions for several hundred thousand years. In the unsaturated upper regions of the caverns, elevated pH levels persist longest, and Nagra is already exploiting this insight by strategically allocating critical waste packages to the upper part of the disposal area.

Modelling of a single barrel of heterogeneous operational waste with limited water availability, tracked over 160 years, delivered a finding with profound implications. The combined effect of high corrosion rates in the internal waste metal pipes, where pH is low and humidity transport is restricted, caused partial drying out inside the drum. Gas production rates were then controlled by the slow water and humidity fluxes from the outside toward the waste compartment, and they came out far smaller than rates calculated assuming unlimited water. The water initially present within waste packages is consumed relatively quickly, leading to desaturation, a drop in reactivity, and a final halting of chemical reactions until new water becomes available. In other words, the repository has a built-in chemical thermostat: it runs hot with reactivity only when water is present, and switches itself off when that water is exhausted.

The review also confronts the enemies within — the organic materials that make up a substantial mass of L/ILW. Polyvinylchloride, ion exchange resins, bitumen, plastics, polycarboxylates, cellulose, and Plexiglas are pressed into standardized 200 litre drums and embedded in cement matrices. Their degradation produces methane, contributing to the overall gas volume; carbon dioxide, which carbonates the cement and erodes the high-pH conditions; and complexing ligands that could enhance radionuclide mobility. Carbonation is the central concern, because dissolved carbon dioxide reacts with calcium from hydrated cement phases to form calcium carbonates, releasing water in the process and reducing both the sorption capacity of the hardened cement paste and its ability to passivate steel. Nagra’s safety assessment accounts for this through a mass balance approach that classifies waste into groups with corresponding sorption values and assigns waste types to slow- or fast-corroding conditions for gas calculations.

At the interfaces where cement meets clay, decades of experimental work at the Mont Terri underground rock laboratory and natural analogue studies at Maqarin in Jordan have shown that the interaction is remarkably tame. Fresh cement porewater, with its pH above 13 and high calcium and hydroxide concentrations, meets the neutral pH 7 porewater of Opalinus Clay, driving diffusion-dominated mineral reactions. Yet the alteration remains limited: clay minerals dissolve and transform into secondary minerals such as zeolites only within a few decimetres of the interface over 100,000 years, and beyond that a zone of elevated pH 8 to 9 develops without significant mineralogical change, extending just a few metres into the host rock. The reduction of free connected pore space at the interface actually slows the geochemical alteration processes, and the beneficial properties of the Opalinus Clay are not impaired. Taken together, the review concludes that the cementitious near field acts as an effective barrier to radionuclide transport over extended periods, delivering immobilization, retention, and controlled release of radionuclides — and that the system understanding gained through numerous studies over recent decades provides strong evidence for the robustness of its evolution and its ability to fulfil its safety functions for a million years to come.

Subject of Research: The safety case for a deep geological repository in Switzerland: engineered barriers for low- and intermediate-level waste disposal

Article Title: The safety case for a deep geological repository in Switzerland: engineered barriers for low- and intermediate-level waste disposal

Article References: Martin, L., Kosakowski, G., Guillemot, T., & Papafotiou, A. (2026). The safety case for a deep geological repository in Switzerland: engineered barriers for low- and intermediate-level waste disposal. Frontiers in Nuclear Engineering, 5, Article 1843726. https://doi.org/10.3389/fnuen.2026.1843726

Image Credits: AI Generated

DOI: 10.3389/fnuen.2026.1843726

Keywords: safety, case, deep, geological, repository, Switzerland, engineered, barriers, low-, intermediate-level, waste, disposal

The scale of the plastic problem provides the backdrop. Approximately 330 million tons of plastic are produced annually, and projections cited in the study indicate that plastic waste generation may reach 12 billion tons by 2050. PET alone accounts for roughly 30% of global plastic consumption, finding its way into beverage bottles, food packaging, containers, and textile fibers. Although mechanical recycling of PET is encouraged, effective recycling rates remain limited by collection difficulties, separation costs, and contamination. Because these polymers degrade slowly and can release toxic compounds such as phthalates and bisphenol-A, and because they fragment into microplastics already detected in water, soil, and air, researchers are increasingly turning to chemical upcycling strategies that convert plastic residues into high-value functional materials.

The Brazilian team chose one of the most ambitious of these strategies: turning PET waste into solid acid catalysts for esterification reactions related to biofuel production. The synthesis began with transparent two-liter bottles from a single soft drink brand, collected in Manaus, washed, dried, and cut into small pieces to ensure reproducibility. The plastic pieces were then subjected to chemical activation in aqueous medium with either zinc chloride (ZnCl2) or potassium carbonate (K2CO3) in a 1:1 mass ratio, heated at 80 °C for 3 hours under magnetic stirring, followed by heat treatment at 100 °C for 24 hours. The activated samples were carbonized in a tubular oven under a nitrogen atmosphere at temperatures ranging from 500 to 700 °C for the ZnCl2 route, while the K2CO3 route required 800 °C. After washing with hydrochloric acid solution and drying, the materials were functionalized by sulfonation in concentrated sulfuric acid, anchoring sulfonic acid (–SO3H) groups onto the carbon structure to confer catalytic activity.

The choice of activating agent proved decisive. ZnCl2 promotes pore formation through oxidative, templating, and gasification mechanisms: during pyrolysis, thermal dehydration of zinc oxide chloride hydrate generates gaseous ZnCl2, which reacts with carbon atoms via reduction reactions, eliminating parts of the carbon atoms and leaving behind channels that form the pore network. K2CO3, by contrast, develops pores primarily through dehydration reactions, the water-gas reaction, and the formation of gaseous potassium metal via reduction of the carbonate by carbon atoms above 760 °C. These distinct mechanisms produced markedly different textures. The K2CO3-activated sample CPK-8 achieved the highest specific surface area of 732 m2 g−1 and total pore volume of 0.61 cm3 g−1, with micropore and mesopore volumes of 0.28 and 0.32 cm3 g−1 respectively. The ZnCl2-activated sample carbonized at 600 °C, CPZn-6, reached 272 m2 g−1 with total, micropore, and mesopore volumes of 0.36, 0.14, and 0.22 cm3 g−1. Nitrogen adsorption isotherms classified the ZnCl2-derived materials as IUPAC type I(a), dominated by micropores centered around 0.9 nm, while CPK-8 showed type I(b) isotherms with H4 hysteresis characteristic of micro-mesoporous carbons with pores centered at 0.7 nm.

Counterintuitively, the material with the highest surface area was not the best catalyst. The K2CO3-activated sample achieved only 65% conversion of oleic acid to methyl oleate, and its performance decreased by 52% after the first reuse. The researchers attribute this to the fact that activation with K2CO3 favors more stable carbon surfaces with lower concentrations of oxygenated functional groups, which hinders effective incorporation of sulfonic acid groups during functionalization. The catalytic behavior of sulfonated carbons, the study concludes, depends more on the density and accessibility of acidic sites than on surface area alone.

The best overall performance came from CPZn-6*, the ZnCl2-activated sample carbonized at 600 °C and sulfonated at 80 °C for 2 hours. This catalyst achieved 88% conversion to methyl oleate and remained effective through the third reuse cycle, a stability advantage over comparable plastic-derived catalysts reported in the literature, which typically show pronounced conversion decreases after the second cycle. The sulfonic group density of CPZn-6*, measured by Boehm titration at 1.31 mmol g−1, is comparable or superior to catalysts derived from coconut shells (0.63–1.18 mmol g−1) and microwave-assisted syntheses (1.12 mmol g−1). Notably, CPZn-6* achieved its high conversion under relatively mild sulfonation conditions of 80 °C for 2 hours, whereas previous PET-derived catalysts required severe conditions of 150 °C for 15 hours and exhibited surface areas below 133 m2 g−1. Increasing the carbonization temperature from 500 to 700 °C raised conversion from 63% to 90% for CPZn-7*, but that catalyst, despite slightly higher acidity of 1.43 mmol g−1, lost stability after the second cycle. The 600 °C activation condition apparently promoted the most stable incorporation of –SO3H groups within the porous structure, contributing to improved resistance against leaching.

An extensive characterization campaign validated the structure and chemistry of the materials. Thermogravimetric analysis recorded three mass loss events for the activated carbons: water desorption between 30 and 150 °C, decomposition of the carbonaceous material between 150 and 350 °C, and thermal decomposition of the PET polymer into volatile species such as CO2 between 360 and 500 °C. For the sulfonated samples, mass losses between 150 and 360 °C attributed to strongly attached sulfonic groups were 14%, 10%, and 15% for CPZn-5*, CPZn-6*, and CPZn-7* respectively, consistent with the Boehm titration results. FT-IR spectroscopy confirmed covalently bonded sulfonic groups through a vibration band at 1,025 cm−1 associated with the O=S=O bond, while thermogravimetry coupled to mass spectrometry detected released water, SO2, and SO3 gases from decomposition of the sulfonic functionalities. Scanning electron microscopy revealed rough, irregular surfaces with cavities of various sizes in the activated carbon, which facilitate reagent diffusion and acid group anchoring; after sulfonation, the surface became smooth and compact. Energy-dispersive spectroscopy showed an increase in oxygen (16% by weight) and sulfur (5% by weight) after sulfonation, confirming effective anchoring of the acid sites.

X-ray photoelectron spectroscopy provided the most precise picture of how sulfur is bonded to the carbon matrix. The C1s spectrum of CPZn-6* showed a peak at 286.1 eV assigned to C–S bonds, strongly suggesting that sulfur was chemically incorporated into the carbonaceous structure rather than merely physically adsorbed. The high-resolution S2p spectrum revealed the characteristic doublet at 167.8 and 168.9 eV, binding energies characteristic of sulfur in the S6+ oxidation state associated with sulfonic acid groups. The O1s spectrum showed a component at approximately 534.0 eV attributed to O=S=O species, providing additional evidence of successful functionalization. According to the literature cited by the authors, the presence of C–S bonds in highly defective carbons derived from polymeric precursors contributes to improved thermal and chemical stability of sulfonated catalysts, explaining the resistance to leaching observed during reuse cycles.

The catalytic optimization revealed clear parameter sensitivities. Sulfonation temperature mattered greatly: 80 °C yielded the maximum 88% conversion, while 60 °C dropped the yield to approximately 70%, and temperatures above 100 °C also reduced performance, apparently because excessive temperatures partially degrade the carbonaceous structure and its anchoring sites. Sulfonation time, by contrast, was not the predominant parameter, with conversion stabilizing around 85% from 2 to 8 hours, suggesting rapid saturation of sulfonic groups on the PET-derived carbon matrix. In the esterification reaction itself, conducted in a high-pressure reactor with an oleic acid to methanol molar ratio of 1:12 and 5% catalyst loading, conversion increased with temperature up to 100 °C and with reaction time up to 1 hour, both reaching the 88% maximum. Higher temperatures decreased the yield, likely because accelerated methanol evaporation reduces reactant availability, and longer reaction times favored interaction of the water byproduct with the hydrophilic sulfonic groups, contributing to partial deactivation through competitive adsorption and site hydration.

The deactivation mechanism was confirmed spectroscopically. After four consecutive reaction cycles, the FT-IR band at 1,025 cm−1 attributed to sulfonic groups disappeared, and thermogravimetric profiles of the reused catalyst showed reduced mass loss associated with sulfonic group decomposition, corroborating the conversion drop below 50% in the third cycle due to leaching of the –SO3H groups. The catalytic activity of CPZn-6*, the authors conclude, is strongly associated with the preservation of surface acidic groups during reuse. Despite this limitation, the study demonstrates that PET waste can be converted into functional carbon-based catalysts with potential application in sustainable biofuel processes, offering what the researchers describe as a sustainable and promising alternative for reusing PET waste while mitigating the environmental problems associated with plastic accumulation in landfills, soils, and oceans.

Subject of Research: Porous carbons from pet waste: structure–property relationships and catalytic performance in esterification reactions

Article Title: Porous carbons from pet waste: structure–property relationships and catalytic performance in esterification reactions

Article References: Santos, J. L., Araujo, R. O., Ribeiro, F. C. P., Guimarães, M. N., Lima, V. M. R., & De Souza, L. K. C. (2026). Porous carbons from pet waste: structure–property relationships and catalytic performance in esterification reactions. Frontiers in Carbon, 5, Article 1873847. https://doi.org/10.3389/frcrb.2026.1873847

Image Credits: AI Generated

DOI: 10.3389/frcrb.2026.1873847

Keywords: PET waste, porous carbon, heterogeneous catalysis, esterification, biodiesel, sulfonation, plastic upcycling, Frontiers in Carbon, Porous, carbons, waste, structure

The target application is alkaline water electrolysis, one of the most mature and cost-effective routes to green hydrogen because it relies on non-precious-metal electrodes and concentrated potassium hydroxide electrolyte. Conventional alkaline electrolyzers use porous diaphragms, such as the commercial Zirfon 500 separator, whose electrolyte-filled pores conduct hydroxide ions. This design carries an intrinsic trade-off: increasing porosity lowers ionic resistance but raises the risk of hydrogen and oxygen gas crossover, which threatens product gas purity and can create hazardous gas mixtures. Anion exchange membranes avoid this problem by conducting hydroxide ions through fixed cationic groups, but those groups degrade under concentrated KOH at elevated temperatures. Ion-solvating membranes offer a third path: they are dense films that transport potassium and hydroxide ions through an absorbed KOH/water phase, without any fixed ionic groups that could be chemically attacked.

The challenge for ion-solvating membranes is that their conductivity depends entirely on how much electrolyte the polymer retains. The team chose poly [2,2′-(1,4-naphthalene)-5,5′-bibenzimidazole], or NPBI, as the matrix because its rigid aromatic backbone and bulky naphthalene units preserve dimensional stability in hot concentrated alkali. However, dense NPBI still limits ion transport because conduction is governed by the amount and distribution of the retained KOH/water phase. The researchers therefore synthesized NPBI by polycondensing 3,3′-diaminobenzidine with 1,4-naphthalenedicarboxylic acid in Eaton’s reagent, achieving a yield above 78 percent, and then dispersed BDC-ZIF-8 filler at loadings of 10 to 50 weight percent relative to the polymer mass. The membranes were cast from DMAc solutions and dried to an average thickness of 23 ± 2 micrometers, roughly twenty times thinner than the 500-micrometer Zirfon reference separator.

The upcycling chemistry itself is elegant. Transparent PET bottles were washed, dried, and cut into flakes, then depolymerized in an ethanol/water mixture with sodium hydroxide at 80 °C for 12 hours under ambient pressure. Acidification with hydrochloric acid to a pH below 3 precipitated the recovered BDC with a yield exceeding 98 percent. Elemental analysis confirmed the recovered linker contained 57.53 weight percent carbon and 3.71 weight percent hydrogen with no detectable nitrogen or sulfur impurities, matching commercial BDC. The team then combined zinc nitrate hexahydrate, 2-methylimidazole, and the recovered BDC in a molar ratio of approximately 11.1:10.0:1.0 and heated the mixture solvothermally at 140 °C for 24 hours. The resulting BDC-ZIF-8 retained the main diffraction peaks of the ZIF-8 framework at 7.3, 10.4, and 12.7 degrees, while developing additional weak peaks at 8.3 and 9.1 degrees that reflect secondary coordination environments introduced by the dicarboxylate linker.

Porosity measurements revealed why this filler is so effective at retaining electrolyte. Nitrogen adsorption isotherms showed type I behavior with a hysteresis loop, indicating coexisting micropores and mesopores. The Brunauer–Emmett–Teller specific surface area reached 1488 square meters per gram, with a micropore volume of 0.56 cubic centimeters per gram and a total pore volume of 1.45 cubic centimeters per gram. Fourier-transform infrared spectroscopy confirmed that the free carboxylic acid C=O stretching peak near 1670 wavenumbers disappeared after framework formation, replaced by asymmetric and symmetric carboxylate stretching peaks at approximately 1558 and 1378 wavenumbers, alongside Zn–N stretching near 422 wavenumbers. These spectral features demonstrate that the carboxylate groups of the upcycled linker coordinated directly with zinc ions, creating polar interaction sites that can hydrogen-bond with water molecules and hydrated potassium ions inside the membrane.

After three days of immersion in 6 M KOH at 80 °C, the electrolyte uptake data told a clear story. The polymer/filler solid fraction decreased from 49 percent in pristine NPBI to 40 percent in the 40 weight percent membrane, while the water fraction rose from 34 to 37 percent and the KOH fraction climbed from 17 to 23 percent. Contact angle measurements reinforced this picture: the DI water contact angle of dry membranes fell from 71.46 to 55.67 degrees as filler loading increased, and after KOH doping all membranes became extremely wettable, with KOH contact angles below 10 degrees. Crucially, the rigid BDC-ZIF-8 domains acted as physical reinforcing phases that suppressed excessive swelling. Pristine NPBI showed relatively large thickness and volume changes after electrolyte uptake, whereas the mixed-matrix membranes exhibited more stabilized dimensional changes despite their higher electrolyte fractions, preserving lateral dimensional stability.

Gas-blocking integrity survived the filler incorporation. Bubble point pressures of the KOH-doped membranes ranged from 6.2 to 6.5 bar, comparable to the 6.1 ± 0.4 bar of pristine NPBI and far exceeding the 2 ± 1 bar of commercial Zirfon 500. Ex situ hydrogen permeability of the wet membranes measured between 0.395 and 0.418 Barrer, essentially unchanged from the 0.571 Barrer of pristine NPBI and roughly 160 times lower than the 89.6 Barrer of Zirfon 500. Mechanical testing showed that moderate filler loadings strengthened the membranes: dry tensile stress increased from 70.20 MPa in pristine NPBI to 78.17 and 79.35 MPa at 20 and 30 weight percent filler, respectively, and after KOH doping the 20 weight percent membrane reached 55.97 MPa, a 47.87 percent increase over doped pristine NPBI. However, the 40 weight percent membrane weakened dramatically to 38.74 MPa dry and 24.57 MPa doped, reflecting filler aggregation and interfacial heterogeneity that concentrate stress during deformation.

The ion transport improvements translated directly into cell performance. Area resistance measured in 6 M KOH at 80 °C fell from 0.067 Ω cm² in pristine NPBI to 0.062, 0.046, 0.040, and 0.037 Ω cm² at 10, 20, 30, and 40 weight percent filler, respectively, all below the 0.079 Ω cm² of Zirfon 500. In zero-gap single cells with bare nickel felt electrodes, the current density at 1.8 V rose from 0.291 A cm⁻² for pristine NPBI to 0.704 A cm⁻² for the 40 weight percent membrane, and at 2.0 V the same membrane delivered 1.809 A cm⁻² compared with 0.913 A cm⁻² for pristine NPBI. Electrochemical impedance spectroscopy confirmed the trend: high-frequency resistance dropped from 0.290 Ω cm² for pristine NPBI to 0.166 Ω cm² for the 40 weight percent cell. The loading-dependent trade-off became apparent in long-term testing, however. During 500 hours of ex situ alkaline exposure, the 10 and 20 weight percent membranes maintained low area resistance stably, while the 30 and 40 weight percent membranes, despite their lower initial resistance, showed gradually increasing resistance over time.

The alkaline stability analysis of the filler itself explains this behavior. When BDC-ZIF-8 powder was aged in 6 M KOH at 80 °C for up to 21 days, the imidazolate C=N vibration peak and the coordinated carboxylate stretching peaks gradually weakened, indicating partial modification of the BDC–Zn coordination environment. Yet the Zn–N vibration near 422 wavenumbers remained detectable after 21 days, and scanning electron microscopy showed the powders retained their overall particle morphology with only surface roughening. After three months of alkaline exposure, all membranes maintained continuous structures without macroscopic cracks, confirming that the resistance increase at high filler loading arose from morphological heterogeneity rather than membrane collapse. Based on its balanced mechanical properties, low cell resistance, and stable long-term behavior, the 20 weight percent membrane was selected for continuous operation, sustaining 100 hours at 0.3 A cm⁻² in 6 M KOH at 80 °C with an average cell voltage of 1.798 V and a maximum of 1.804 V.

This study demonstrates that waste PET can be upcycled into a functional electrolyte-retaining metal–organic framework filler for next-generation alkaline electrolyzers, closing a loop between plastic recycling and green hydrogen production. The findings also carry a clear design lesson: filler loading must be optimized to balance electrolyte retention, ion transport, membrane morphology, and alkaline stability, because the lowest initial resistance does not necessarily correspond to the most stable long-term performance. As hydrogen economies scale up and plastic waste streams continue to grow, strategies that convert one problem into the solution for another could prove decisive. The researchers note that further studies under practical operating conditions are needed to evaluate the applicability of these membranes in larger alkaline water electrolysis systems, but the demonstration that a discarded beverage bottle can help split water into hydrogen marks a compelling step toward circular clean-energy materials.

Subject of Research: Materials Science

Article Title: Waste PET-derived BDC-ZIF-8 as an electrolyte-retaining filler for NPBI-based ion-solvating mixed-matrix membranes in alkaline water electrolysis

Article References: Park, S. J., Seo, J., Lee, Y.-R., Choi, Y.-W., Choi, J., & Lee, J. H. (2026). Waste PET-derived BDC-ZIF-8 as an electrolyte-retaining filler for NPBI-based ion-solvating mixed-matrix membranes in alkaline water electrolysis. Frontiers in Membrane Science and Technology, 5, Article 1892925. https://doi.org/10.3389/frmst.2026.1892925

Image Credits: AI Generated

DOI: 10.3389/frmst.2026.1892925

Keywords: alkaline water electrolysis, BDC-ZIF-8, ion-solvating membranes, metal–organic framework, NPBI, waste PET, green hydrogen, mixed-matrix membranes, Waste, PET-derived, electrolyte-retaining, filler

The study, led by PhD student Yuwei Zhao, analyzed two years of hourly methane observations collected from the Mineola Tower, a National Institute of Standards and Technology monitoring site located on Long Island. The tower is strategically positioned to sample air flowing out of Manhattan and western Long Island during westerly winds. By utilizing data from January 2023 through December 2024, the research team was able to capture detailed seasonal patterns in emissions. The researchers estimate that methane emissions associated with natural gas use amounted to approximately 1.7% of all gas delivered through the system, representing a substantial loss of fuel that consumers are paying for but not fully utilizing.

Based on retail prices from 2023 and 2024, the researchers calculated that this wasted natural gas is equivalent to nearly $300 million. This financial loss underscores the economic impact of inefficient energy use, in addition to the environmental consequences. Methane is a potent greenhouse gas, possessing more than 80 times the global warming potential of carbon dioxide over a 20-year timescale. Because methane remains in the atmosphere for only about a decade, reducing its emissions offers a relatively quick method to slow near-term global warming, making the identification of these sources particularly timely for climate mitigation efforts.

To distinguish between different sources of methane, the study team conducted intensive measurement campaigns at the Mineola Tower during the summer of 2023 and the winter of 2024. They measured methane, ethane, and carbon monoxide at high frequency to chemically identify and separate raw natural gas leaks from the incomplete combustion occurring in buildings. The analysis revealed a distinct seasonal cycle in emissions, with methane levels peaking during the winter heating season, declining through the spring, and rising again during the summer cooling season before increasing further in the subsequent heating season. This pattern highlighted the importance of year-round monitoring, as the summertime signal indicated that cooling systems also contribute significantly to emissions.

Natural gas accounted for the vast majority of methane emissions throughout the year, representing 99% of total emissions in February and 98% in May. During the summer cooling months, natural gas still accounted for 85% to 88% of total methane emissions. Co-author Róisín Commane, an Associate Professor in Columbia’s Department of Earth and Environmental Sciences, noted that while winter heating was expected to dominate, the significant summertime signal suggested that large buildings using natural gas-powered cooling systems were a major contributor. This finding challenges the assumption that methane emissions are primarily a winter phenomenon and emphasizes the need for comprehensive seasonal tracking.

The researchers identified incomplete combustion as the dominant signal detected at the Mineola Tower in both heating and cooling seasons. They distinguished this from pipeline leaks by looking for a correlation between methane and carbon monoxide, a byproduct produced when natural gas does not burn completely. Natural gas leaks that occur before the gas reaches customers would not exhibit this combustion signature. The data showed that only 6% of the identified natural gas plumes in winter and 7% in summer lacked a combustion signature, indicating that pipeline leaks were detected less frequently at the tower than methane associated with inefficient burning in buildings. This suggests that the focus on fixing underground leaks, while important, may not address the primary source of urban methane emissions.

The study provides the first monthly analysis tracking methane emissions before and after natural gas reaches customers in the NYC metropolitan area. The researchers’ methods enabled them to distinguish between natural gas released without combustion and inefficiently burned gas from heating and cooling systems. Methane emissions also closely tracked real-time natural gas deliveries across the study area, further supporting the conclusion that emissions were driven mainly by natural gas use after it reaches customers. This close relationship between delivery and emissions helps explain why previous estimates of methane emissions in the New York metropolitan area have exceeded national and global inventory estimates, which often rely on different methodologies and may overlook these specific combustion-related losses.

Previous studies had estimated two to five times more methane emissions in the New York area than those accounted for in official inventories. Despite ongoing efforts to fix pipeline leaks, methane emissions in cities have remained higher than expected, suggesting that important sources were being overlooked. The authors argue that inefficient use of natural gas, including incomplete combustion, accounts for much of this missing methane and should be incorporated into future calculations and policy frameworks. By identifying this overlooked pathway, the study offers cities a new opportunity to reduce methane emissions while simultaneously saving consumers millions of dollars lost to wasted natural gas.

The findings also have broader implications for a warming climate. Rising temperatures and more frequent and intense extreme weather events are expected to increase demand for both heating and cooling. Without a transition to cleaner energy sources, greater use of natural gas to meet this increased demand could lead to higher methane emissions in urban areas. Reducing these emissions could offer a significant near-term opportunity for climate mitigation, as the rapid atmospheric decay of methane means that cuts to its sources can have a noticeable impact on global warming within a decade. The research highlights the importance of improving appliance efficiency and exploring alternative energy sources to address both the environmental and economic costs of natural gas use in major cities.

Subject of Research: Unused natural gas behind NYC’s $300 million waste of a potent greenhouse gas

Article Title: Unused natural gas behind NYC’s $300 million waste of a potent greenhouse gas

Article References: Unused natural gas behind NYC’s $300 million waste of a potent greenhouse gas. (n.d.). Original publication

Image Credits: AI Generated

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Keywords: Unused, natural, behind, million, waste, potent, greenhouse, scientific research