C | September 2026 - Browse Articles

23 pages, 11899 KB

Open AccessArticle

Influence of the Porous Structure of Activated Carbons on the Retention of Cigarette Smoke Constituents

by Luigi Madeo, Carlo Poselle Bonaventura, Pietro Figliuzzi, Carlo Siciliano, Anastasia Macario, Alfonso Policicchio, Assunta Perri and Pierantonio De Luca

C 2026, 12(3), 71; https://doi.org/10.3390/c12030071 - 11 Sep 2026

Viewed by 263

Abstract

Cigarette smoke is a significant source of indoor air pollution, containing particulate matter and numerous volatile and semi-volatile organic compounds. This study evaluates the adsorption performance of two commercial activated carbons, Nuchar SA 1500 (SA) and Filtercarbon PHA (PHA), correlating their pore structure [...] Read more.

Cigarette smoke is a significant source of indoor air pollution, containing particulate matter and numerous volatile and semi-volatile organic compounds. This study evaluates the adsorption performance of two commercial activated carbons, Nuchar SA 1500 (SA) and Filtercarbon PHA (PHA), correlating their pore structure with their ability to retain cigarette smoke contaminants. A two-stage laboratory filtration system was developed to analyze the non-retained fraction using a downstream cellulose filter, employed as an indirect indicator of adsorption efficiency. BET/NLDFT, SEM/EDS, and thermogravimetric analyses show that Nuchar SA 1500, characterized by a more developed micro-mesoporous network, retains a larger fraction of particulate matter and condensable compounds compared with Filtercarbon PHA. Based on preliminary investigations, which revealed a markedly higher adsorption behavior for Nuchar SA 1500, the analytical focus was directed toward this material; consequently, GC–MS analysis was performed only on Nuchar SA 1500, excluding Filtercarbon PHA. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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22 pages, 5217 KB

Open AccessArticle

Modeling of CO₂-Based Fischer–Tropsch Synthesis over a Cu/Zn/K-Promoted Fe Catalyst: Influence of Reaction Kinetics and Multi-Fixed-Bed Reactor Design

by Florian Mai and Andreas Jess

C 2026, 12(3), 70; https://doi.org/10.3390/c12030070 - 9 Sep 2026

Viewed by 282

Abstract

CO₂ hydrogenation by reverse water–gas shift (RWGS) directly combined with subsequent Fischer–Tropsch synthesis (FTS) in a single fixed-bed reactor represents a promising route for converting renewable hydrogen and captured carbon dioxide into hydrocarbons. However, the attainable CO₂ conversion is limited by [...] Read more.

CO₂ hydrogenation by reverse water–gas shift (RWGS) directly combined with subsequent Fischer–Tropsch synthesis (FTS) in a single fixed-bed reactor represents a promising route for converting renewable hydrogen and captured carbon dioxide into hydrocarbons. However, the attainable CO₂ conversion is limited by thermodynamic constraints of the RWGS, product inhibition of FTS, and intraparticle diffusion limitations. In the present work, intrinsic and effective reaction models were developed for a potassium-promoted FeCuZnK catalyst to investigate the interaction between intrinsic catalyst kinetics and internal diffusion phenomena. An intrinsic Langmuir–Hinshelwood–Hougen–Watson (LHHW) model was established using fine catalyst particles (d_p ≤ 150 µm) and subsequently extended to coarse catalyst particles (d_p ≈ 2 mm) by introducing an effectiveness factor. The intrinsic model identified water as the dominant inhibiting species, whereas the already high RWGS activity of the FeCuZnK catalyst leads to a rapid approach of the thermodynamic equilibrium, indicating that an increase in activity would only provide limited improvements. The effective model accurately reproduced the behavior of technical catalyst particles and was subsequently applied to multi-reactor concepts with intermediate water removal. A five-stage reactor cascade increased the attainable CO₂ conversion from approximately 55% to 85% under otherwise identical operating conditions. The results demonstrate that reactor design and water management provide greater potential for process intensification than further increases in intrinsic catalyst activity alone. Full article

(This article belongs to the Special Issue Advanced Catalysis for CO₂ Conversion and Utilization)

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24 pages, 11639 KB

Open AccessArticle

Eco-Friendly Chitosan/Graphene Oxide Hybrid Nanoparticles as a Dual-Action Platform for Methylene Blue Removal and Antimicrobial Water Treatment

by Marco Fiore, Michele Pellegrino, Giuseppe Cirillo, Ludovica Scorzafave, Manuela Curcio, Roberta Pino, Michele De Luca, Stefania Marsico, Francesca Iemma and Fiore Pasquale Nicoletta

C 2026, 12(3), 69; https://doi.org/10.3390/c12030069 - 1 Sep 2026

Viewed by 208

Abstract

This work reports the synthesis and characterization of sustainable, multifunctional chitosan/graphene oxide hybrid nanoparticles (GOCS_NPs) prepared via a low-temperature ionotropic gelation method utilizing sodium tripolyphosphate as a green crosslinker. Combined DLS and TEM analyses confirmed the successful formation of submicron spherical [...] Read more.

This work reports the synthesis and characterization of sustainable, multifunctional chitosan/graphene oxide hybrid nanoparticles (GOCS_NPs) prepared via a low-temperature ionotropic gelation method utilizing sodium tripolyphosphate as a green crosslinker. Combined DLS and TEM analyses confirmed the successful formation of submicron spherical nanoparticles with a mean diameter of 295 ± 15 nm (PDI 0.26), and GOCS_NPs were evaluated as a dual-action platform for the adsorption of a model cationic dye, Methylene Blue (MB), and for antimicrobial remediation against Staphylococcus aureus and Escherichia coli. Equilibrium adsorption studies revealed that incorporating GO dramatically increased the maximum monolayer adsorption capacity from 2.78 mg g⁻¹ (for CS_NPs) to 37.16 mg g⁻¹ (for GOCS_NPs), closely following the Langmuir and Sips models through a pseudo-second order sorption mechanism. Furthermore, desorption investigations demonstrated that the GOCS_NPs maintained substantial adsorption performance over multiple adsorption–desorption cycles under controlled conditions. Concurrently, GOCS_NPs exhibited a dose-dependent enhancement in antibacterial efficacy, showing greater activity against Gram-negative E. coli (MIC of 1.25 mg mL⁻¹) than against Gram-positive S. Aureus (MIC of 2.50 mg mL⁻¹). Overall, these findings elucidate the structure–property–performance relationships of these carbon–biopolymer hybrid nanocomposites, validating their suitability as an advanced, eco-friendly, and reusable platform for comprehensive and sustainable wastewater remediation. Full article

(This article belongs to the Special Issue Carbon Nanohybrids for Biomedical Applications (2nd Edition))

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22 pages, 6096 KB

Open AccessArticle

Parameter and Process Optimization for Low-Concentration CO₂ Capture Using Mixed Alkanolamine Solutions

by Tieya Jing, Liqian Zhao, Zhenhua Cheng, Juan Zhou, Xu He, Zongtai Li, Hui Zhang, Jian Sun and Xiaoxiang Jiang

C 2026, 12(3), 68; https://doi.org/10.3390/c12030068 - 30 Aug 2026

Viewed by 167

Abstract

To reduce the high energy consumption of conventional alkanolamine-based CO₂ capture, a rate-based CO₂ capture model was developed in Aspen Plus using a DETA/AEP mixed amine absorbent identified through preliminary screening experiments. The effects of key operating parameters of the absorber [...] Read more.

To reduce the high energy consumption of conventional alkanolamine-based CO₂ capture, a rate-based CO₂ capture model was developed in Aspen Plus using a DETA/AEP mixed amine absorbent identified through preliminary screening experiments. The effects of key operating parameters of the absorber and stripper on system performance were systematically investigated, and the energy-saving potentials of interstage cooling, rich-solvent splitting, and their combined process were explored. The results show that the optimal operating parameters are as follows: lean-solvent temperature of 40 °C, flow rate of 150 m³/h, concentration of 35 wt.%, absorber packing height of 10 m, stripper operating pressure of 2 bar, rich-solvent feed stage at the fifth stage, and feed temperature of 105 °C. Under these optimized conditions, the model-predicted specific regeneration energy consumption of the conventional process was 6.08 GJ/t CO₂. Introducing interstage cooling at the ninth stage reduced the specific regeneration energy consumption to 5.42 GJ/t CO₂. Rich-solvent splitting, with a split ratio of 15% and hot rich-solvent feeding at the sixth stage, further reduced the value to 3.45 GJ t⁻¹ CO₂. When the two strategies were integrated, the specific regeneration energy consumption decreased to 3.38 GJ/t CO₂, corresponding to a 44.41% reduction compared with the conventional process. Full article

(This article belongs to the Section Carbon Cycle, Capture and Storage)

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12 pages, 1500 KB

Open AccessArticle

Boron Incorporation Efficiency in Diamond: Influence of Gas Composition, Crystal Orientation, and Substrate Temperature

by Vincent Mortet, Mahebub Alam, Patrik Straňák, Kildong Sung, Yan Busby, Lutz Kirste and Wolfgang Klesse

C 2026, 12(3), 67; https://doi.org/10.3390/c12030067 - 27 Aug 2026

Viewed by 272

Abstract

In this work, boron incorporation in diamond grown by microwave plasma-enhanced chemical vapor deposition is investigated as a function of methane concentration, boron precursor concentration, crystalline orientation, oxygen addition to the plasma, and deposition temperature. The boron incorporation efficiency, i.e., the ratio between [...] Read more.

In this work, boron incorporation in diamond grown by microwave plasma-enhanced chemical vapor deposition is investigated as a function of methane concentration, boron precursor concentration, crystalline orientation, oxygen addition to the plasma, and deposition temperature. The boron incorporation efficiency, i.e., the ratio between the boron concentration in diamond and the gas-phase boron-to-carbon ratio, spans several orders of magnitude and can exceed unity for all investigated crystalline orientations. Overall results demonstrate that methane concentration and the substrate’s crystalline orientation are key factors governing boron incorporation. The temperature study reveals that boron incorporation is also governed by thermally activated boron-loss mechanisms. Finally, all results show that boron incorporation is not exclusively controlled by the plasma composition but also by surface growth mechanisms. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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20 pages, 2171 KB

Open AccessArticle

Pore-Size-Specific Evaluation of Commercial Biochars for Apparent Removal of the Boar-Taint Compounds Indole and Skatole Under Fecal Matrix Conditions

by Franziska Witte, Andreas Juadjur, Volker Heinz, Christian Visscher, Jochen Weiss and Nino Terjung

C 2026, 12(3), 66; https://doi.org/10.3390/c12030066 - 27 Aug 2026

Viewed by 283

Abstract

Indole and skatole are microbial tryptophan degradation products occurring in intestinal and fecal matrices and contribute to boar taint. Biochar is discussed as a carbonaceous adsorbent for reducing these compounds, but the link between pore-size-specific surface area and removal under complex fecal matrix [...] Read more.

Indole and skatole are microbial tryptophan degradation products occurring in intestinal and fecal matrices and contribute to boar taint. Biochar is discussed as a carbonaceous adsorbent for reducing these compounds, but the link between pore-size-specific surface area and removal under complex fecal matrix conditions remains insufficiently understood. This study evaluated the apparent removal of skatole and indole by ten commercial biochar samples, including selected related material variants, under fecal matrix conditions to identify pore-size-specific descriptors associated with adsorption. With this approach, differences associated with drying, loading, biomass, and production were also explored. Pore-structural properties were characterized by nitrogen physisorption and compared across several data-reduction models. For interpretation, non-local-density-functional-theory-derived pore-size-specific surface area, ranging from 8.3 to 572.0 m²/g, was used to define functional pore-size classes relevant to small aromatic molecules. Geometry-based molecular dimensions and conservative molecular footprints of indole and skatole were used to estimate theoretical monolayer loading potential. Indole generally showed higher apparent loading than skatole, and apparent monolayer-reference ratios reached up to 20.57 for indole and 3.16 for skatole, confirming that experimentally observed apparent loading could exceed the conservative geometric monolayer reference. This indicates that surface area provides a structural reference rather than a direct prediction of removal under fecal conditions. Full article

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26 pages, 695 KB

Open AccessArticle

Mathematical Modeling of Biochar Pore Descriptors from Pyrolysis Temperature: Semi-Empirical Correlations for BET Surface Area, Total Pore Volume, and Mean Pore Diameter of Lignocellulosic Feedstocks

by Jesús D. Rhenals-Julio, Jorge M. Mendoza, Andrés F. Jaramillo, Calixto José Rhenals and Antonio Bula Silvera

C 2026, 12(3), 65; https://doi.org/10.3390/c12030065 - 14 Aug 2026

Viewed by 476

Abstract

Predicting the pore structure of lignocellulosic biochar from pyrolysis conditions without exhaustive experimental characterization remains an open challenge. We fit semi-empirical Arrhenius-type and power-law correlations linking pyrolysis temperature to

S_{BET}

,

V_{T}

, and

{\bar{d}}_{p}

by nonlinear least squares, [...] Read more.

Predicting the pore structure of lignocellulosic biochar from pyrolysis conditions without exhaustive experimental characterization remains an open challenge. We fit semi-empirical Arrhenius-type and power-law correlations linking pyrolysis temperature to

S_{BET}

,

V_{T}

, and

{\bar{d}}_{p}

by nonlinear least squares, using 45 literature records from seven open access studies (12 feedstocks, 300–800 °C). The central finding is that feedstock category, not temperature alone, dominates variance in

S_{BET}

: pooled calibration explains only

R^{2} = 0.199

(RMSE = 183 m² g⁻¹), whereas feedstock-stratified fitting recovers accuracy (e.g., RMSE = 43.6 m² g⁻¹ for grasses, a within-study estimate from a single source). The Arrhenius and power-law forms are statistically indistinguishable (

Δ AIC < 2

); the Arrhenius form is adopted for physical interpretability. Pooled fits reach

R^{2} = 0.691

(

V_{T}

) and

0.563

(

{\bar{d}}_{p}

). Leave-one-study-out cross-validation (RMSE = 184 m² g⁻¹) confirms that reliable prediction requires calibration data within the target feedstock category. The correlations are descriptive tools valid within their calibration envelope, not general predictive models. Estimation uses no machine learning; a benchmark against OLS and random forest models confirms that greater flexibility improves in-sample fit but not out-of-sample generalization. Full article

(This article belongs to the Special Issue Carbon Innovations in Renewable Energy Systems and Environmental Sustainability)

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47 pages, 7467 KB

Open AccessReview

Advancements in Green Pretreatment, Thermochemical Conversion, and By-Product Valorization of Lignocellulosic Biomass for Energy Applications

by Harrison Appiah, Sang Hyeok Park and Jovale Vincent Tongco

C 2026, 12(3), 64; https://doi.org/10.3390/c12030064 - 14 Aug 2026

Viewed by 969

Abstract

The urgent need for bio-based functional materials has driven a shift away from fossil-fuel-sourced materials toward renewable lignocellulosic biomass (LCB). This comprehensive review explores the advancements in LCB carbonization between 2020 and 2026, marking a shift from traditional, low-yield combustion processes toward highly [...] Read more.

The urgent need for bio-based functional materials has driven a shift away from fossil-fuel-sourced materials toward renewable lignocellulosic biomass (LCB). This comprehensive review explores the advancements in LCB carbonization between 2020 and 2026, marking a shift from traditional, low-yield combustion processes toward highly selective and sustainable thermochemical conversion pathways. The primary objective of this review is to evaluate the integration of green pretreatment strategies, conversion technologies, and efficient valorization of the aqueous effluents and by-products. The goal of green pretreatment is to overcome the inherent recalcitrance of LCB without the use of harsh chemicals and reaction conditions, specifically highlighting the effectiveness of deep eutectic solvents (DESs) and ionic liquids (ILs). The review also evaluates the emerging conversion technologies, including hydrothermal carbonization (HTC), microwave-assisted pyrolysis (MAP), and the synergistic co-pyrolysis of LCB with synthetic polymeric wastes. Another novel concept in preparing hard carbon and other related materials is the “lignin-first” biorefinery strategy, which facilitates the subsequent production of high-value aromatic monomers, platform chemicals, and biofuels. The engineered carbon materials are increasingly utilized well beyond their traditional use as solid fuels. The products have been proven to be excellent for use in high-performance energy conversion and storage, serving as renewable bio-based electrode materials for supercapacitors and carbon electrodes in next-generation batteries. Full article

(This article belongs to the Special Issue Carbon Materials for Electrochemical Energy Storage and Conversion)

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12 pages, 1715 KB

Open AccessArticle

Observation and Analysis of Luminescence of a Colloidal-Organized Suspension of Nanodiamond

by Artashes Karmenyan, Elena Perevedentseva, Pooja Manik Badgujar, Nikolai Melnik and Chia-Liang Cheng

C 2026, 12(3), 63; https://doi.org/10.3390/c12030063 - 31 Jul 2026

Viewed by 484

Abstract

This paper investigates the spectral properties of colloidally ordered systems formed from 100 nm nanodiamonds (NDs) synthesized using the high-pressure high-temperature (HPHT) method. Despite the polydispersity and irregular shape of the particles, aqueous ND suspensions can colloidally order via repeated centrifugation-induced sedimentation. To [...] Read more.

This paper investigates the spectral properties of colloidally ordered systems formed from 100 nm nanodiamonds (NDs) synthesized using the high-pressure high-temperature (HPHT) method. Despite the polydispersity and irregular shape of the particles, aqueous ND suspensions can colloidally order via repeated centrifugation-induced sedimentation. To the best of our knowledge, this is the first spectroscopic study of such ordered ND systems. In our study, we obtained colloidally ordered ND structures, evidenced by the formation of rainbow-colored layers in the centrifuge tubes. Fragments extracted from these layers were subjected to microscopic and spectroscopic characterization. Spectroscopic measurements with 488 nm wavelength laser reveal modulated emission in a narrower spectral range, lying within the characteristic broad emission band of NDs and indicating the formation of ordered structures with a characteristic micrometer scale. In view of the intrinsic luminescence of NDs, we propose that these structures are best regarded as analogous to colloidal photonic crystals with intrinsic luminescence. This concept can significantly extend the functionality of ND-based materials and offers new opportunities for fundamental optical studies and practical photonic applications. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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24 pages, 4610 KB

Open AccessArticle

Structure–Property Assessment of Graphene Oxide in Gypsum/Plaster: Effects of Thermal Treatments on the Water and Mechanical Resistance

by Daniel Firmino, Pedro de Araujo, Caroline Araujo and Marcos Ghislandi

C 2026, 12(3), 62; https://doi.org/10.3390/c12030062 - 29 Jul 2026

Cited by 1 | Viewed by 512

Abstract

A structure–property assessment of coating plaster reinforced with a low dosage (0.01 wt%) of graphene oxide (GO) was investigated to address the intrinsic mechanical and thermal limitations of gypsum in civil construction. Nanocomposite specimens were characterized in terms of hydration kinetics (setting time), [...] Read more.

A structure–property assessment of coating plaster reinforced with a low dosage (0.01 wt%) of graphene oxide (GO) was investigated to address the intrinsic mechanical and thermal limitations of gypsum in civil construction. Nanocomposite specimens were characterized in terms of hydration kinetics (setting time), wettability (water contact angle), and compressive behavior across a range of post-fabrication thermal treatments at 200 °C, 250 °C, and 300 °C. Although the incorporation of 0.01 wt% GO maintained the ultimate compressive strength of the matrix (~13.8 MPa), it fundamentally transformed the pre-yield behavior, doubling the initial structural stiffness (slope) from 8.7 to 18.7 MPa·mm⁻¹. This mechanical enhancement suggests the role of GO as a structural anchor capable of bridging micro-voids and restricting microcrack propagation. Beyond 200 °C, phase transformation via gypsum dehydration into basanite and anhydrite phases, validated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), led to a severe reduction in compressive strength for both neat and reinforced matrices. Crucially, however, the GO-reinforced composites retained a 76% higher structural stiffness compared to the neat plaster within this post-thermal regime. Additionally, thermal activation at 200 °C induced a critical surface modification, elevating the water contact angle to 68.1° because of partial GO thermal reduction, as confirmed by coupled TG/FTIR analysis. These findings demonstrate that while GO does not suppress the intrinsic chemical dehydration of the calcium sulfate matrix, it provides vital mechanical stabilization to the crystalline network, significantly enhancing rigidity and deformation resistance under severe thermal stress. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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25 pages, 3573 KB

Open AccessArticle

rGO/ZnO/CuO Hybrid-Coated Stretch Textiles for Flexible Thermoelectric and Electrothermal Applications

by Bilal Alam Khan, Muhammad Zaman Khan, Azam Ali and Shahid Ali Shaukat

C 2026, 12(3), 61; https://doi.org/10.3390/c12030061 - 22 Jul 2026

Viewed by 559

Abstract

Flexible thermoelectric textiles have emerged as promising materials for wearable energy harvesting and electrothermal applications because they combine mechanical flexibility with the ability to convert low-grade heat into electrical energy. In this study, reduced graphene oxide/zinc oxide/copper oxide (rGO/ZnO/CuO) hybrid nanocomposites were synthesized [...] Read more.

Flexible thermoelectric textiles have emerged as promising materials for wearable energy harvesting and electrothermal applications because they combine mechanical flexibility with the ability to convert low-grade heat into electrical energy. In this study, reduced graphene oxide/zinc oxide/copper oxide (rGO/ZnO/CuO) hybrid nanocomposites were synthesized and deposited onto Cotton–Nylon–Spandex (80:15:05) stretch fabrics using a silicone elastomer-assisted coating process to develop flexible conductive textiles. The influence of nanocomposite loading (2–8 g/100 mL elastomer) on the structural, electrical, thermal, and thermoelectric properties of the coated fabrics was systematically investigated. SEM, EDX, XRD, and Raman analyses confirmed the successful formation and uniform distribution of the rGO/ZnO/CuO hybrid coating on the textile substrate. Increasing the nanocomposite loading progressively reduced the electrical resistance from approximately 42 to 18 MΩ, indicating the formation of an interconnected conductive network, while the Seebeck coefficient increased from 0.049 to 0.056 mV K⁻¹ (49–56 μV K⁻¹). The measured effective thermal conductivity of the coated textile decreased from approximately 12 to 2.68 W m⁻¹ K⁻¹, reflecting changes in the thermal transport behavior of the composite coating. The coated fabrics also exhibited stable electrical performance under repeated bending, stretching (up to 80% strain), and washing, together with improved thermal stability and uniform Joule-heating behavior. These results demonstrate that the rGO/ZnO/CuO hybrid coating provides an effective strategy for developing flexible, mechanically durable, and multifunctional conductive textiles with potential applications in wearable thermoelectric energy harvesting and smart heating systems. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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26 pages, 36852 KB

Open AccessArticle

Influence of Manufacturing Process and Material Configuration on the Mechanical and Elastic Properties of Kevlar–Carbon Hybrid Laminates

by Ciprian Ionuț Morăraș, Teodor Adrian Badea, Viorel Goanță, Lucia Raluca Maier, Alexa-Andreea Crisan and Paul Doru Barsanescu

C 2026, 12(3), 60; https://doi.org/10.3390/c12030060 - 21 Jul 2026

Viewed by 565

Abstract

The present study investigates the combined influence of manufacturing route and material configuration on the mechanical, elastic, viscoelastic, and impact behavior of Kevlar–carbon hybrid laminates. Three eight-ply laminate configurations (V1, V2, and V3) were manufactured through distinct technological routes: fully prepreg-based hot pressing, [...] Read more.

The present study investigates the combined influence of manufacturing route and material configuration on the mechanical, elastic, viscoelastic, and impact behavior of Kevlar–carbon hybrid laminates. Three eight-ply laminate configurations (V1, V2, and V3) were manufactured through distinct technological routes: fully prepreg-based hot pressing, Kevlar-prepreg/dry-carbon hand lay-up followed by vacuum curing, and multi-stage hybrid consolidation combining repeated hot pressing with subsequent vacuum curing. The experimental characterization included tensile tests according to ASTM D3039, compression tests according to ASTM D695, determination of Young’s modulus from extensometer measurements and Poisson’s ratio using strain-gauge instrumentation, dynamic mechanical analysis (DMA), and low-velocity impact tests under controlled energy conditions. The novelty of this work consists in the integrated process–configuration–property comparison of these Kevlar–carbon hybrid routes within the same experimental framework, rather than in a generic demonstration that manufacturing affects composite laminates. The V1 laminate exhibited the highest strength-related performance, reaching an average tensile strength of 335.88 MPa and a compressive strength of 165.85 MPa, and it also showed the highest DMA storage modulus at 30 °C, E’ = 53.42 GPa. The V2 laminate presented lower tensile performance but the most pronounced damping response, with the highest tanδ peak value. The Young’s modulus determined from the extensometer measurements was 29.26 ± 1.45 GPa for V1, 26.10 ± 0.22 GPa for V2, and 29.52 ± 1.27 GPa for V3, indicating comparable longitudinal stiffness for the V1 and V3 laminates. The results indicate that the measured behavior is governed by the combined effects of reinforcement form, matrix/resin arrangement, consolidation route, and laminate architecture. Direct quantification of laminate compaction, fiber volume fraction, and void content was outside the scope of the present experimental campaign and is identified as a necessary step for future validation. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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18 pages, 8425 KB

Open AccessArticle

Preparation and Sorption Properties of Graphene Oxide and Melamine Composite Aerogels

by S. A. Baskakov, Yu. V. Baskakova, A. V. Zharkovskaya, D. A. Chernyaev, E. N. Kabachkov, M. V. Zhidkov and Y. M. Shulga

C 2026, 12(3), 59; https://doi.org/10.3390/c12030059 - 13 Jul 2026

Viewed by 657

Abstract

In this study, composite aerogels based on graphene oxide (GO) and melamine (MM), obtained by freeze-drying of hydrogels after ultrasonic treatment of aqueous suspensions, have been systematically studied for the first time. It was shown that the addition of melamine leads to an [...] Read more.

In this study, composite aerogels based on graphene oxide (GO) and melamine (MM), obtained by freeze-drying of hydrogels after ultrasonic treatment of aqueous suspensions, have been systematically studied for the first time. It was shown that the addition of melamine leads to an increase in the aerogel density from 12 to 22 mg/cm³, a change in its color, and the formation of a structure reminiscent of nacre. Using IR spectroscopy, Raman scattering, TGA, and DSC, it was established that during synthesis, partial reduction of GO, hydrolysis of sulfate groups, and strong intermolecular (including possible covalent) interactions between the components occur. The exothermic peak for GO aerogel (ΔH ~1480 J/g, ~220 °C) shifts to a lower temperature region in the composite. MM/GO composite aerogels demonstrate record sorption capacity for organic solvents (up to 86 g/g) and mineral-oil (66 g/g), significantly surpassing known analogs. A key limitation was identified—the leaching of melamine by water, which reduces water sorption by 15 times after the first cycle. The obtained materials can be considered promising for eliminating spills of organic liquids and petroleum products. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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16 pages, 2863 KB

Open AccessArticle

Valorization of Vigna trilobata Rind Waste into Activated Carbon for Efficient Iron Removal from Aqueous Solutions

by Vamsee Krishna Kodali, Randhi Uma Devi, K. Sri Lakshmi, Damaraju Lakshmi Lavanya and Bala chandu Koya

C 2026, 12(3), 58; https://doi.org/10.3390/c12030058 - 9 Jul 2026

Viewed by 526

Abstract

Iron (Fe) contamination of water sources has become an increasing environmental concern, creating the need for effective, environmentally friendly, and cost-effective technologies for Fe(III) removal from aqueous systems. In the present work, the possibility of using the sulfuric acid-activated carbon made of Vigna [...] Read more.

Iron (Fe) contamination of water sources has become an increasing environmental concern, creating the need for effective, environmentally friendly, and cost-effective technologies for Fe(III) removal from aqueous systems. In the present work, the possibility of using the sulfuric acid-activated carbon made of Vigna trilobata rind waste for treating water contaminated with Fe ions was explored. The characteristics of the synthesized material were identified by physical, chemical, and spectroscopic methods, and its Fe ion sorption efficiency was studied experimentally in batch mode under various conditions. Equilibrium, kinetics, and thermodynamics of Fe ion removal by the prepared adsorbent were determined. The obtained adsorbent had a BET surface area of 20.55 m² g⁻¹ and showed high experimental adsorption capacity with the highest observed uptake of 19.81 mg g⁻¹. Based on the experimental results, the equilibrium data could be best described by the Langmuir equation (R² = 0.978). Kinetic analysis showed that the rate-limiting step in Fe ion sorption was intraparticle diffusion (R² = 0.921). Thermodynamic calculations indicated that the adsorption process occurred spontaneously (ΔG° = −4.31 to −6.53 kJ mol⁻¹) and endothermically (ΔH° = +7.11 kJ mol⁻¹). A comparative analysis showed that the sorption capacity of the studied adsorbent corresponded to that reported for the analogous materials produced from other biomasses. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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39 pages, 1739 KB

Open AccessReview

Carbon-Based Microfluidic Sensors for Water Monitoring

by Guihe Li and Jia Yao

C 2026, 12(3), 57; https://doi.org/10.3390/c12030057 - 7 Jul 2026

Cited by 1 | Viewed by 1575

Abstract

Carbon-based materials, including graphene, carbon nanotubes, laser-induced graphene, and pyrolyzed glassy carbon, are widely used in sensing applications due to their high conductivity, large surface area, and tunable surface chemistry. Meanwhile, microfluidic systems enable precise fluid handling, reduced sample consumption, and enhanced analytical [...] Read more.

Carbon-based materials, including graphene, carbon nanotubes, laser-induced graphene, and pyrolyzed glassy carbon, are widely used in sensing applications due to their high conductivity, large surface area, and tunable surface chemistry. Meanwhile, microfluidic systems enable precise fluid handling, reduced sample consumption, and enhanced analytical performance through improved mass transport and device miniaturization. The integration of carbon-based materials with microfluidic platforms has enabled the development of compact, portable, and highly sensitive devices for water monitoring. This review summarizes recent advances in carbon-based microfluidic sensors for water monitoring applications. Key carbon materials and their sensing mechanisms, particularly electrochemical transduction, are discussed. Various microfluidic integration strategies, including paper-based devices, polymer-based devices, MEMS-based systems, and flexible platforms, are highlighted, with emphasis on mass transport enhancement and overall system performance. Representative recent advances in carbon-based microfluidic sensors for water monitoring, including the detection of heavy metal ions, nutrients, and emerging contaminants, are reviewed. Finally, challenges related to scalable manufacturing, long-term operational stability, biofouling/surface fouling, and reproducible system integration are discussed, together with future perspectives on intelligent carbon-based microfluidic platforms featuring AI-assisted analytics, sense-response functionality, and self-healing and dynamic antifouling capabilities for water monitoring. These advances are expected to enable real-time, low-cost, and field-deployable water monitoring systems for environmental protection and public health management. Overall, this review highlights the critical role of integrating carbon-based sensing materials with microfluidic engineering in advancing next-generation water monitoring technologies. Full article

(This article belongs to the Special Issue Carbons for Health and Environmental Protection (2nd Edition))

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17 pages, 2183 KB

Open AccessArticle

Biochar in Anaerobic Digestion: Part 2—Laser-Induced Breakdown Spectroscopy and Ultimate Analysis for Prediction of Biochar Higher Heating Value

by Abdullah Al Saadi, Nour EI Houda Chaher, Hans Korte, Abdallah Nassour, Michael Nelles and Jan Sprafke

C 2026, 12(3), 56; https://doi.org/10.3390/c12030056 - 30 Jun 2026

Viewed by 753

Abstract

Reliable estimation of biochar’s calorific value is essential for optimizing its use as a renewable energy source. Traditional bomb calorimetry provides accurate measurements but is hindered by its destructive, time-consuming nature, limiting the high-throughput screening capabilities needed for large-scale deployment. In this study, [...] Read more.

Reliable estimation of biochar’s calorific value is essential for optimizing its use as a renewable energy source. Traditional bomb calorimetry provides accurate measurements but is hindered by its destructive, time-consuming nature, limiting the high-throughput screening capabilities needed for large-scale deployment. In this study, an innovative, non-destructive approach utilizing laser-induced breakdown spectroscopy (LIBS) combined with advanced multivariate analysis is presented for predicting the Higher Heating Value (HHV) of biochar derived from pine and beech biomass. The developed empirical model incorporates spectral signatures of key elements: carbon, hydrogen, nitrogen, sulfur, and oxygen. Model validation using 36 independent biochar samples revealed a statistically significant correlation between experimentally measured and LIBS-predicted HHVs (p-value = 0.045, t-statistic = 2.08). The developed model yielded a mean absolute error (MAE) of 1.33 MJ kg⁻¹ and a root mean square error (RMSE) of 1.72 MJ kg⁻¹. The findings demonstrate the feasibility of using LIBS-derived elemental data for rapid HHV estimation and provide a basis for further model refinement through the inclusion of additional biochar types and calibration datasets. The model effectively captures the complex nonlinear relationships between spectral features and energy content, addressing the heterogeneity inherent in biochar matrices. These findings highlight LIBS’s potential as a rapid, scalable, and environmentally sustainable tool for real-time biochar evaluation. Implementing this approach could significantly accelerate biomass resource assessment, optimize bioenergy production, and advance sustainable energy management strategies aligned with global environmental goals. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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15 pages, 9559 KB

Open AccessArticle

Dislocation Reactions in a Crystal of Soft Particles in the Form of a Transversely Compressed Bundle of Carbon Nanotubes

by Olga V. Andrukhova, Andrey A. Ovcharov, Daria A. Durasova, Vladimir A. Bryzgalov, Arseny M. Kazakov, Marat A. Ilgamov, Elena A. Korznikova and Sergey V. Dmitriev

C 2026, 12(3), 55; https://doi.org/10.3390/c12030055 - 29 Jun 2026

Viewed by 410

Abstract

Properties of defects in crystals composed of soft particles, such as colloids, differ markedly from those in metals. In this work, dislocation reactions in a bundle of carbon nanotubes (CNTs) are investigated using relaxational molecular dynamics. The problem is reduced to a two-dimensional [...] Read more.

Properties of defects in crystals composed of soft particles, such as colloids, differ markedly from those in metals. In this work, dislocation reactions in a bundle of carbon nanotubes (CNTs) are investigated using relaxational molecular dynamics. The problem is reduced to a two-dimensional model, where the strain state of the CNT bundle is fully determined by the cross-sectional shapes of the nanotubes arranged in a close-packed triangular lattice. A pair of edge dislocations with opposite topological charges is introduced into an uniaxially compressed bundle, and their relaxational dynamics are analyzed as a function of the distance d between the parallel planes along which the dislocations glide. When the dislocations move in the same plane (d = 0), they annihilate, restoring a defect-free structure. For negative distances (d < 0), their interaction results in the formation of a vacancy (d = −1), a bivacancy (d = −2), extended voidions (d = −3, −4), or dislocation dipoles (d < −4). In contrast to metals, vacancy clusters containing more than two missing particles in CNT bundles relax into extended voidions. For positive distances (d > 0), the dislocation reaction generates interstitial-type defects in the form of crowdions, which at sufficiently large separations (d > 4) can also be interpreted as dislocation dipoles. In most cases, except for d = 0 and d = 1, dislocation glide enables complete relaxation of the initial shear strain, even in the presence of defects. However, for d = 0 and d = 1, dislocation annihilation or immobilization limits plastic deformation, resulting in only partial stress relaxation. The observed effects are due to the elliptization of the cross-sections of soft carbon nanotubes in the cores of defects. These findings highlight significant differences in defect behavior between crystals of deformable particles and conventional metallic systems. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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26 pages, 3192 KB

Open AccessReview

Recycling of Petroleum-Based Lubricants into High-Value Petrochemicals and Carbon-Based Materials

by Sandugash Tanirbergenova, Dildara Tugelbayeva, Nurzhamal Zhylybayeva, Aizat Aitugan, Arailym Akimbek, Kairat Tazhu, Gulya Moldazhanova and Zulkhair Mansurov

C 2026, 12(3), 54; https://doi.org/10.3390/c12030054 - 25 Jun 2026

Viewed by 1196

Abstract

Waste lubricating oils (WLOs) represent a major stream of hazardous petroleum-based residues, with global generation exceeding 24 million tons annually. Improper disposal of WLOs poses risks to soil, water, and air quality, while their chemical composition makes them a potential secondary resource within [...] Read more.

Waste lubricating oils (WLOs) represent a major stream of hazardous petroleum-based residues, with global generation exceeding 24 million tons annually. Improper disposal of WLOs poses risks to soil, water, and air quality, while their chemical composition makes them a potential secondary resource within circular economy frameworks. This review summarizes conventional, advanced, and emerging technologies reported for the recycling and valorization of WLOs into high-value petrochemicals and carbon-based materials. Established processes such as acid–clay treatment, solvent extraction, and vacuum distillation are discussed together with more recent approaches, including catalytic upgrading, hydrotreatment, membrane separation, and thermochemical conversion methods such as pyrolysis and catalytic cracking. Reported data on process performance, environmental considerations, techno-economic indicators, and life cycle assessment outcomes are comparatively analyzed to outline current trends, technical challenges, and future development directions in WLO recycling. Particular attention is given to thermochemical pathways capable of generating carbonaceous materials, including carbon black, porous carbons, and functional carbon nanostructures with potential applications in adsorption, catalysis, electrochemical systems, and tribological formulations. Hybrid and integrated process configurations described in the literature are highlighted for their potential to improve recovery efficiency, enhance product quality, and reduce environmental burdens. In addition, recent life cycle assessment (LCA) and techno-economic analysis (TEA) studies are reviewed to provide insight into the environmental and economic implications of advanced re-refining systems. Overall, the reviewed literature indicates that WLO recycling represents not only an important element of sustainable lubricant management but also a promising waste-to-carbon strategy for the production of value-added carbon-based materials and petrochemical products. Full article

(This article belongs to the Special Issue Advances in Carbon-Based Materials)

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C, Volume 12, Issue 3 (September 2026) – 18 articles

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