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16 pages, 12750 KB

Open AccessArticle

Assessment of Production Methods and Locations for CO₂ Storage in Seafloor Environment

by Muhammad Towhidul Islam, Vincent Nana Boah Amponsah and Boyun Guo

C 2026, 12(2), 53; https://doi.org/10.3390/c12020053 - 22 Jun 2026

Viewed by 481

Disposing of carbon dioxide (CO₂) in the seafloor environment in its hydrate form provides an efficient means of CO₂ storage in virtually unlimited quantity. The process requires that the in situ condition be above the hydrate-forming pressure and below the [...] Read more.

Disposing of carbon dioxide (CO₂) in the seafloor environment in its hydrate form provides an efficient means of CO₂ storage in virtually unlimited quantity. The process requires that the in situ condition be above the hydrate-forming pressure and below the hydrate-forming temperature and that the bulk CO₂ hydrates have densities greater than seawater density for gravitational stability. The objectives of this study are (1) to find an efficient method for generating stable CO₂ hydrates, (2) to identify the required equipment for efficient production of CO₂ hydrates, and (3) to identify the required water depth in various seawater environments for CO₂ injection. The first objective was achieved using a windowed reactor to observe the floating and settling behavior of generated CO₂ hydrates. CO₂ injection into the chilly water phase and water injection into the cold CO₂ phase were both investigated at various pressures and temperatures. CO₂ injection into the chilly water phase was found to generate bulk CO₂ hydrates of density less than that of water due to the excess CO₂ trapped in the bulk hydrates. Water injection into the cold CO₂ phase was found to generate bulk CO₂ hydrates of density greater than that of water due to the excess water trapped in the bulk hydrates. The second objective was achieved by designing a complete set of equipment to be installed on a ship with an open-bottom reactor assembly attached to the ship. The third objective was achieved by cross-plotting the hydrate-forming pressure curve versus the seawater hydrostatic pressure curve for seven seas and the Arctic Ocean. Results show that the minimum required seawater depth varies from 120 m in the Arctic Ocean to 650 m in the Mediterranean Sea environment. Full article

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

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20 pages, 4252 KB

Open AccessArticle

Microwave-Assisted N,S Co-Doped Reduced Graphene Oxide for Eco-Friendly Environmental Monitoring of Nitrobenzene

by Prathingara Subramanian, Tharini Jeyapragasam, Kandasamy Muthusamy, Vinitha Mariyappan and Rasu Ramachandran

C 2026, 12(2), 52; https://doi.org/10.3390/c12020052 - 17 Jun 2026

Cited by 1 | Viewed by 900

Abstract

A nitrogen/sulfur co-doped reduced graphene oxide (N,S-RGO) material was rationally prepared via a modified Hummers method followed by microwave-assisted reduction. The resulting material was uniformly deposited onto a glassy carbon electrode (GCE) to fabricate an electrochemical sensor for nitrobenzene (NB) detection. The prepared [...] Read more.

A nitrogen/sulfur co-doped reduced graphene oxide (N,S-RGO) material was rationally prepared via a modified Hummers method followed by microwave-assisted reduction. The resulting material was uniformly deposited onto a glassy carbon electrode (GCE) to fabricate an electrochemical sensor for nitrobenzene (NB) detection. The prepared N,S-RGO material was characterized in detail using Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy, confirming the successful incorporation of heteroatoms. Furthermore, electrochemical studies, including cyclic voltammetry (CV) and linear sweep voltammetry (LSV), revealed the enhanced electrical conductivity of the material. The fabricated N,S-RGO/GCE sensor exhibited remarkable electroanalytical performance, achieving a low detection limit (LOD) of 7 nM within a linear concentration range of 0.05 to 147 µM. The enhanced sensing performance is attributed to the synergistic effect of nitrogen and sulfur doping, which improves electron transfer kinetics and abundant active sites for NB reduction. Furthermore, the sensor demonstrated outstanding selectivity toward NB in the presence of common interfering substances. Its practical applicability was confirmed through the successful detection of NB in environmental water samples, yielding convincing recovery rates. These results highlight the potential of the N,S-RGO/GCE platform as an efficient and reliable electrochemical sensor for environmental monitoring of NB contamination. Full article

(This article belongs to the Topic Environmental Pollutant Management and Control)

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22 pages, 3162 KB

Open AccessArticle

Surface-Integrated Hydrogen Sensing Using ZnFe₂O₄–CNT Composite Coatings on Cement-Based Materials with Data-Driven Concentration Prediction

by Mohammadmahdi Abedi, Zivar Azmoodeh and Eloi Figueiredo

C 2026, 12(2), 51; https://doi.org/10.3390/c12020051 - 9 Jun 2026

Viewed by 960

Abstract

Transforming existing structural surfaces into sensing interfaces offers a promising route for scalable hydrogen monitoring in hydrogen-handling facilities, where leakage poses significant safety risks, addressing the limitations of conventional point-based sensors. In this study, a surface-integrated ZnFe₂O₄–CNT (ZFC) composite [...] Read more.

Transforming existing structural surfaces into sensing interfaces offers a promising route for scalable hydrogen monitoring in hydrogen-handling facilities, where leakage poses significant safety risks, addressing the limitations of conventional point-based sensors. In this study, a surface-integrated ZnFe₂O₄–CNT (ZFC) composite coating is developed as a potentially retrofit-compatible sensing solution to enable hydrogen sensing directly on cementitious materials, combining material-level functionality with data-driven concentration prediction. The ZFC composite was synthesized via a hydrothermal method followed by CNT functionalization and composite formation, and was then applied onto cement-based substrates using a thickness-controlled coating approach. Structural and morphological characterization (XRD, FESEM, TEM, BET) confirmed the formation of a hierarchical, porous architecture, while hydrogen sensing performance was evaluated under controlled thermo-hygrometric conditions (24–72 °C, 32–87% RH) at 10,000 ppm H₂. The sensor exhibited stable and reversible responses, with optimal performance at 39–52 °C and a minimum response time of 18 s. An XGBoost model enabled accurate prediction of hydrogen concentration, achieving R² ≈ 0.92 and RMSE ≈ 820 ppm under dynamic exposure. These results demonstrate that coupling redox-active oxide surfaces with conductive CNT networks enables effective surface-based chemiresistive sensing under realistic conditions. The proposed system transforms conventional cementitious materials into smart, surface-integrated hydrogen sensing systems, offering a scalable and retrofit-compatible approach for real-time monitoring in hydrogen-related infrastructure. Full article

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

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20 pages, 9039 KB

Open AccessArticle

Effects of Co-Solvent and Polymer Composition in Gel Electrolytes on the Performance of Paper Dye-Sensitized Solar Cells

by Yi Kou and Takahide Oya

C 2026, 12(2), 50; https://doi.org/10.3390/c12020050 - 4 Jun 2026

Viewed by 670

Abstract

In this study, we investigated how co-solvent and polymer combinations affect the performance of dye-sensitized solar cells (DSSCs) using TiO₂- and ZnO-modified carbon nanotube (CNT) composite papers as photoelectrodes. Co-solvents such as N,N-dimethylformamide (DMF) and ethylene glycol (EG) were incorporated into [...] Read more.

In this study, we investigated how co-solvent and polymer combinations affect the performance of dye-sensitized solar cells (DSSCs) using TiO₂- and ZnO-modified carbon nanotube (CNT) composite papers as photoelectrodes. Co-solvents such as N,N-dimethylformamide (DMF) and ethylene glycol (EG) were incorporated into polyethylene glycol (PEG)- and poly(ethylene oxide) (PEO)-based gel electrolytes to increase the amount of dissolved I₂/KI redox species and evaluate their influence on the wettability of the electrolyte on CNT composite paper electrodes. PEG-based electrolytes containing DMF or EG improved the fill factor (FF) and power conversion efficiency (PCE) relative to the baseline formulation, with the EG–PEG electrolyte achieving the best single-device PCE of 15.58 × 10⁻³% using the CNT/ZnO composite paper. Replacing PEG with PEO or using PEG + PEO blends led to reduced performance, possibly because the modified polymer composition affected electrolyte wetting, spreading behavior, and penetration into the porous electrode. These results suggest that the wettability and viscosity-related behavior of gel electrolytes are important empirical factors associated with the performance of flexible paper DSSCs, and provide practical guidance for the design of paper-based photovoltaic devices. Full article

(This article belongs to the Special Issue Optical and Electronic Innovations in Carbon Nanotubes)

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11 pages, 7137 KB

Open AccessArticle

Lignin Valorization via Microwave Processing: Conversion to Porous Hydrophilic Carbon Materials

by Larissa Giorgetti Mendes, Paloma Elias da Silva Pellegrini, Eduardo de Souza Esperança, Silvia Vaz Guerra Nista and Stanislav Moshkalev

C 2026, 12(2), 49; https://doi.org/10.3390/c12020049 - 31 May 2026

Viewed by 965

Abstract

Millions of tons of lignin waste are generated annually by the pulp and paper industries and by biofuel production. Current strategies for lignin valorization, biochars and hydrogels, often rely on time-costly and pollutant-generating processes and therefore fail to meet sustainability requirements nor are [...] Read more.

Millions of tons of lignin waste are generated annually by the pulp and paper industries and by biofuel production. Current strategies for lignin valorization, biochars and hydrogels, often rely on time-costly and pollutant-generating processes and therefore fail to meet sustainability requirements nor are economically efficient. In this work, we address the challenge of transforming lignin into a valued-added material. We propose using microwave processing to convert lignin into a functional material that is carbon-rich, structured, hydrophilic, and highly porous. Unlike conventional methods, this process is rapid, occurring in approximately 30 s under normal conditions. It induces graphitization and up to a sixfold volumetric expansion of the lignin precursor sample, leading to the formation of a stable carbon material with high porosity in the form of capsules. The resulting material exhibits strong hydrophilicity, absorbing up to 90% of its volume in water within minutes while enabling controlled release over periods of up to 24 h. This unique combination of ultrafast processing, high water uptake capacity, and controlled-release performance positions the material as a promising alternative to the valorization of lignin. Its properties make it particularly suitable for water management applications in agriculture and urban environments. Full article

(This article belongs to the Topic Functional Carbon-Based Materials and Systems for Energy and Environmental Applications)

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22 pages, 4352 KB

Open AccessArticle

Physicochemical Properties of Pristine and Pyrolyzed CNO Synthesized via Wick Pyrolysis

by Abirami Srinivasan, Avanottingal Bhaskaran Prasanth, C. N. Shyam Kumar and Amrtha Bhide

C 2026, 12(2), 48; https://doi.org/10.3390/c12020048 - 29 May 2026

Viewed by 821

Abstract

Carbon nano-onions (CNOs) were synthesized at ambient conditions using the wick-pyrolysis technique with ghee as a precursor. A high-purity copper substrate produced unique CNOs, differing from those obtained with other metals. To purify the nanoparticles, they underwent treatment with a solvent mixture of [...] Read more.

Carbon nano-onions (CNOs) were synthesized at ambient conditions using the wick-pyrolysis technique with ghee as a precursor. A high-purity copper substrate produced unique CNOs, differing from those obtained with other metals. To purify the nanoparticles, they underwent treatment with a solvent mixture of acetone and deionized water or were pyrolyzed at 1000 °C under nitrogen without a catalyst. Various characterization techniques, including X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), High-Resolution Transmission Electron Microscopy (HR-TEM), and Raman Spectroscopy, confirmed the successful formation of CNOs. Energy Dispersive Spectroscopy (EDS) and Elemental analysis (CHN) indicated the presence of oxygen in treated CNOs. X-ray photoelectron spectroscopy (XPS) revealed binding energies linked to C-O and C=O bonds. The average particle size was found to be 30–50 nm, with some agglomeration in pyrolyzed samples. A significant increase in surface area from 79.7 m²/g to 261.8 m²/g was observed, along with changes in pore radius and volume via Brunauer–Emmett–Teller (BET) analysis. Water contact angles on the CNO surface were measured at 125° and 138°, indicating hydrophobicity. Electrochemical tests on CNO-based composite electrodes yielded a specific capacitance of 109.7 F/g with 96% capacity retention over 5000 cycles. Full article

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17 pages, 11736 KB

Open AccessArticle

Hydrothermal Synthesis of Carbon Microspheres from Lignocellulosic Bio-Oil

by Galina Dobele, Ance Plavniece, Kristine Meile, Kalvis Liepins, Oskars Bikovens, Vilhelmine Jurkjane and Aivars Zhurinsh

C 2026, 12(2), 47; https://doi.org/10.3390/c12020047 - 27 May 2026

Viewed by 957

Abstract

Biomass valorization into carbon-rich materials has attracted increasing attention as a sustainable alternative to fossil-based resources. This work is devoted to the study of hydrothermal carbonization (HTC) of spruce lignocellulose liquid pyrolysis products (the target product of the pyrolysis is levoglucosan)—bio-oil (B). In [...] Read more.

Biomass valorization into carbon-rich materials has attracted increasing attention as a sustainable alternative to fossil-based resources. This work is devoted to the study of hydrothermal carbonization (HTC) of spruce lignocellulose liquid pyrolysis products (the target product of the pyrolysis is levoglucosan)—bio-oil (B). In addition, the fractionated B compounds, including the phenol-enriched fraction remaining after anhydrosugar removal, were evaluated as potential precursors for hydrochar production. Hydrochars were produced at 200, 250, and 300 °C and characterized using SEM, revealing that spherical morphology agglomerates can also be obtained from the phenol-enriched fraction. The chemical composition and structural evolution of the hydrochars were investigated by Py-GC/MS, elemental analysis, and FTIR, demonstrating the significant influence of both precursor composition and carbonization temperature on hydrochar chemistry. In addition, the organic compounds in the process water were analyzed using UHPLC and complementary chemical analysis. The results show that the chemical composition of the precursor strongly influences the yield, morphology, and chemical composition of the obtained hydrochar. Full article

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

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22 pages, 1668 KB

Open AccessReview

Carbon Quantum Dots as Emerging Antibacterial Nanomaterials: Strategies to Enhance Their Activity

by Hong Yin, Wenjing Chen, August Bratovic, Rachel W. Li and Ivan Cole

C 2026, 12(2), 46; https://doi.org/10.3390/c12020046 - 27 May 2026

Cited by 2 | Viewed by 1592

Abstract

Carbon quantum dots (CQDs) exhibit multiple antibacterial mechanisms, making them more effective than conventional antibiotics, which typically act through a single mode of action. These mechanisms include membrane disruption, biofilm inhibition, reactive oxygen species (ROS) generation, and photodynamic (PDT) or photothermal (PTT) effects [...] Read more.

Carbon quantum dots (CQDs) exhibit multiple antibacterial mechanisms, making them more effective than conventional antibiotics, which typically act through a single mode of action. These mechanisms include membrane disruption, biofilm inhibition, reactive oxygen species (ROS) generation, and photodynamic (PDT) or photothermal (PTT) effects under light irradiation. Extensive research has been conducted to reinforce these mechanisms and improve the antibacterial performance of CQDs, aiming to reduce required CQD dosages and combat bacterial resistance. This review systematically summarizes structural and functional design strategies reported since 2020. We categorized these strategies into selecting antibacterial molecules as precursors, controlling particle size, surface modification, doping with non-metal and metal elements, and forming functional composites to enable light activation, synergetic effects, and multifunctionality. For each category, we provide representative CQD examples, in terms of their preparation, physicochemical properties contributing to antibacterial performance, and possible structure–activity relationships. Finally, the review highlights limitations and proposes future research directions for developing antibacterial CQDs for clinical translation. Full article

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

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19 pages, 6565 KB

Open AccessArticle

Effects of Feedstock Type and Pyrolysis Duration on Functional Properties of Biomass-Derived Charred Materials Under Low-Temperature Pyrolysis

by Zonghui Chu, Tsuneyoshi Endo, Tsugiyuki Masunaga, Eiji Nishihara and Sadahiro Yamamoto

C 2026, 12(2), 45; https://doi.org/10.3390/c12020045 - 25 May 2026

Viewed by 937

Abstract

Low-temperature pyrolysis around 250 °C represents a mild carbonization that differs from conventional high-temperature biochar production, and the role of pyrolysis duration under mild thermal conditions remains insufficiently understood. In this study, plant residues, including rice straw, sorghum leaves and stems, barley straw, [...] Read more.

Low-temperature pyrolysis around 250 °C represents a mild carbonization that differs from conventional high-temperature biochar production, and the role of pyrolysis duration under mild thermal conditions remains insufficiently understood. In this study, plant residues, including rice straw, sorghum leaves and stems, barley straw, and mixed woodchips, were converted into charred materials under low-temperature pyrolysis at 250 °C (4 h, 12 h) and compared with those produced at 500 °C (4 h). Pyrolysis at 250 °C (4 h) resulted in higher solid yields (51.9–72.8%) and higher recovery of carbon and nitrogen, whereas yields declined to 27.2–31.6% at 500 °C. Materials produced at 250 °C preserved abundant oxygen-containing functional groups, exhibited lower pH, and showed significantly higher cation exchange capacity (up to 93.68–119.91 cmol_c/kg at 12 h). Prolonged treatment at 250 °C enhanced humification, increasing the carbon extracted from humic acid by 25.3–237.9%, whereas humic substances were largely decomposed at 500 °C. Structural analyses indicated that low-temperature chars maintained reactive surface chemistry, while high-temperature chars showed greater aromaticity and porosity, particularly for wood-derived materials (378.5 m²/g). Overall, low-temperature pyrolysis produces functionally active carbon materials suitable for saline-sodic soil amendment and nutrient management, whereas 500 °C pyrolysis generates more aromatic and porous materials better suited for long-term carbon stability and physical soil conditioning. Full article

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

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15 pages, 3000 KB

Open AccessArticle

Response Surface Optimization of Lead Sorption by Pinus roxburghii Cone-Derived Activated Carbon: Performance Assessment and Optimization

by Aditi, Dharmendra, Aditya Thakur, Chetna Tewari and Sumit Kumar

C 2026, 12(2), 44; https://doi.org/10.3390/c12020044 - 25 May 2026

Cited by 1 | Viewed by 758

Abstract

The pervasive issue of lead contamination in water systems necessitates the development of advanced and sustainable remediation methodologies. Powdered activated carbon synthesized from Pinus roxburghii has been meticulously evaluated as a high-performance capture medium to remove sequestration of lead ions from aqueous systems [...] Read more.

The pervasive issue of lead contamination in water systems necessitates the development of advanced and sustainable remediation methodologies. Powdered activated carbon synthesized from Pinus roxburghii has been meticulously evaluated as a high-performance capture medium to remove sequestration of lead ions from aqueous systems through batch adsorption studies. These adsorption dynamics were optimized by Response Surface Methodology integrated with Central Composite Design, enabling precise calibration of crucial influential factors such as pH, contact time, and adsorbent dosage. Morphological analysis conducted using Scanning Electron Microscopy confirmed a highly porous structure, while Fourier Transform Infrared Spectroscopy identified functional groups, such as hydroxyl groups coupled with carbonyl groups, which exhibit strong metal affinity. Under optimal conditions, a pH of 8.2, a time of 140 min, and an adsorbent dosage of 0.03 g/L resulted in a maximum lead removal efficiency of 99.86%. Validation trials substantiated the reproducibility of the process, yielding a marginally diminished efficiency of 98.62 ± 1.24%. The integration of RSM not only validated the statistical significance of the experimental outcomes but also reinforced the predictive accuracy. This study demonstrates the critical interplay of adsorption parameters and highlights the physicochemical properties of Pinus roxburghii-based activated carbon, emphasizing its potential for advanced water purification processes. Full article

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

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2 pages, 168 KB

Open AccessEditorial

Editorial for C—Journal of Carbon Research: 10th Anniversary Special Issue

by Craig E. Banks

C 2026, 12(2), 43; https://doi.org/10.3390/c12020043 - 15 May 2026

Viewed by 400

Abstract

The 10th Anniversary Issue of C—Journal of Carbon Research has concluded with the publication of 21 high-quality papers [...] Full article

(This article belongs to the Special Issue 10th Anniversary of C — Journal of Carbon Research)

28 pages, 9073 KB

Open AccessReview

Remediation of Heavy Metals and Organic Pollutants in Soil by Biochar: A Comprehensive Review

by Weijian Zhang, Zaiwang Zhang and Zenghui Diao

C 2026, 12(2), 42; https://doi.org/10.3390/c12020042 - 12 May 2026

Cited by 2 | Viewed by 2001

Abstract

In recent years, soil contamination by heavy metals and organic pollutants has become a serious environmental problem. Biochar is a highly carbonaceous, water-insoluble porous material made from biomass feedstock through a thermochemical conversion process, and it has been widely used in the remediation [...] Read more.

In recent years, soil contamination by heavy metals and organic pollutants has become a serious environmental problem. Biochar is a highly carbonaceous, water-insoluble porous material made from biomass feedstock through a thermochemical conversion process, and it has been widely used in the remediation of various soil pollutants. However, previous reviews on the modification of biochar and the remediation reaction mechanism of heavy metals and organic pollutants by biochar in soil were still not sufficiently comprehensive. Based on the current research status of the remediation of heavy metals and organic pollutants by biochar in soil, this review systematically summarized biomass feedstock types, pyrolysis methods and their applicable scenarios, as well as the modification strategies of biochar, including pore structure modification, surface functional group modification, surface charge modification, and magnetic modification. It also comparatively discussed the adsorption of heavy metals by biochar mainly through electrostatic attraction, ion exchange, complexation/precipitation, cation−π interaction, and redox transformation, while the adsorption of organic pollutants via π−π/EDA interactions, electrostatic attraction, hydrogen bonding, hydrophobic partitioning, and pore filling were outlined. The review also discussed competitive effects among pollutants during biochar adsorption under co-contamination scenarios, as well as the synergistic interactions between biochar and soil microorganisms or plants. In addition, the review addressed recent progress in field-scale applications of biochar, as well as the current state of research on aging effects, ecological risks, and economic feasibility. Finally, it identifies key research directions that warrant further attention. This review highlighted the mechanistic differences between heavy metal stabilization and organic pollutant removal in soil by biochar, and provided mechanistic insight and guidance for biochar-based soil remediation. Full article

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

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44 pages, 3980 KB

Open AccessReview

A Review of Recent Advancements in the Application of Monoethanolamine for CO₂ Capture

by Rahul R. Bhosale

C 2026, 12(2), 41; https://doi.org/10.3390/c12020041 - 11 May 2026

Viewed by 1352

Abstract

Monoethanolamine (MEA) remains the predominant solvent for carbon dioxide (CO₂) capture due to its rapid reaction kinetics, substantial absorption capacity, and demonstrated industrial effectiveness. Despite its established status, MEA-based systems are undergoing continuous development to lower energy requirements, enhance solvent stability, [...] Read more.

Monoethanolamine (MEA) remains the predominant solvent for carbon dioxide (CO₂) capture due to its rapid reaction kinetics, substantial absorption capacity, and demonstrated industrial effectiveness. Despite its established status, MEA-based systems are undergoing continuous development to lower energy requirements, enhance solvent stability, and expand operational adaptability. This review provides a critical assessment of recent progress in MEA-based CO₂ capture, encompassing molecular-level understanding, advancements in reactor and process design, solvent modification strategies, and system-wide optimization. Recent theoretical and experimental research has improved the understanding of CO₂ absorption mechanisms in MEA, highlighting the effects of reaction-product buildup, interfacial phenomena, and free amine availability on mass-transfer efficiency. Reboiler duty and comparable work have significantly decreased as a result of advances in process intensification, improved regeneration systems, and energy-integration techniques. New hybrid strategies that partially decouple capture from thermal regeneration, such as combined absorption–mineralization pathways, show promise for long-term CO₂ sequestration. To address regeneration energy, corrosion, degradation, and cyclic stability, this review examines advances in MEA-based solvents, including aqueous blends, non-aqueous and biphasic systems, ionic liquids, and deep eutectic solvent hybrids. It also critically assesses the trade-offs of developments in intensified contactors, surfactants, nanomaterials, and catalysts. The growing role of digital optimization, machine learning, and computational modeling in MEA process design and control is highlighted. Overall, this analysis underscores MEA’s continued importance as a versatile platform for next-generation carbon capture, utilization, and storage. Full article

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

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17 pages, 633 KB

Open AccessReview

Rational Functional Design of Carbon Quantum Dots for Food Safety and Preservation: A Critical Review

by Ziting Zhang and Juan Du

C 2026, 12(2), 40; https://doi.org/10.3390/c12020040 - 11 May 2026

Cited by 1 | Viewed by 1629

Abstract

Carbon quantum dots (CQDs) have attracted considerable attention as versatile fluorescent nanomaterials in the domains of food safety and preservation, primarily due to their tunable photoluminescence, high aqueous dispersibility, and favorable biocompatibility. Although numerous reviews have documented the synthesis and extensive applications of [...] Read more.

Carbon quantum dots (CQDs) have attracted considerable attention as versatile fluorescent nanomaterials in the domains of food safety and preservation, primarily due to their tunable photoluminescence, high aqueous dispersibility, and favorable biocompatibility. Although numerous reviews have documented the synthesis and extensive applications of CQDs, a focused critical assessment specifically addressing how rational surface functionalization and heteroatom doping impact their performance within complex food matrices remains absent. This review provides a targeted analysis of the interplay between the functional design of CQDs, including both surface group engineering and elemental doping, and their practical efficacy in food-related applications. Initially, a concise overview of the fundamental aspects of CQDs relevant to their functionality is presented, emphasizing the origin and role of surface chemical groups and pivotal photophysical sensing mechanisms. Subsequently, the core of the review critically evaluates recent advancements (particularly those from 2022 onward) in the use of functionalized CQDs for detecting food contaminants (such as heavy metals, pesticide residues, antibiotic residues, pathogens, and additives) and in food preservation techniques, including active packaging, antioxidative and antimicrobial coatings, and photodynamic inactivation. Through a systematic comparison of analytical figures of merit and the effects of various matrices across different design approaches, we delineate both the established capabilities and the current limitations of CQD-based technologies in realistic food systems. The review concludes by identifying ongoing challenges, specifically, batch-to-batch consistency, the long-term safety profile of CQDs in food-contact applications, and the translation gap from laboratory innovation to industrial practice, and outlines prospective research directions. The overarching aim of this work is to provide a structured framework for understanding how deliberate functional design can lead to improved performance, thereby guiding the rational development of next-generation CQD-based materials for ensuring food quality and public health. Full article

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

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22 pages, 3567 KB

Open AccessArticle

Impact of Sodium Dodecyl Sulfate Sonochemical Byproducts on the Gel-Based Purification of Single-Walled Carbon Nanotubes

by Laurique N. Hughes, Natasha Mastalka-Tatro and Kevin Tvrdy

C 2026, 12(2), 39; https://doi.org/10.3390/c12020039 - 6 May 2026

Viewed by 1073

Abstract

The chirality-specific study of single-walled carbon nanotubes (SWCNTs) necessitates their solution-phase processing with tip-horn sonication in the presence of a stabilizing surfactant such as sodium dodecyl sulfate (SDS), a process that has been shown to introduce sonochemical side-products such as dodecanol, dodecanal, and [...] Read more.

The chirality-specific study of single-walled carbon nanotubes (SWCNTs) necessitates their solution-phase processing with tip-horn sonication in the presence of a stabilizing surfactant such as sodium dodecyl sulfate (SDS), a process that has been shown to introduce sonochemical side-products such as dodecanol, dodecanal, and dodecene. This work employs single-column interactions within the overloading regime to quantitatively assess the impacts of dodecanol, dodecanal, and dodecene on the ability to purify SWCNTs using Sephacryl S-200 hydrogel. Increasing concentrations of each additive caused a corresponding decrease in the number of SWCNTs adsorbed to the gel, with a 50% reduction in SWCNT uptake realized at 0.75–1.00 mM for all three additives. Per-chirality adsorption selectivity was unaffected by relatively low additive concentration, but it was significantly hindered nearer the solubility limit of each additive. Elution efficiency from each gel was independent of additives, additive concentration, and SWCNT chirality. Mechanistically, these findings suggest the integration of each additive within the micelle structure of SDS. While the concentration of each additive introduced during tip-horn sonication is insufficient to impact gel-based SWCNT purification, the presence of dodecanol impurities within as-purchased SDS have the potential to significantly impact the purification outcome, suggesting that future studies of gel-based SWCNT purification should be carried out with SDS purified by recrystallization. Full article

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

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16 pages, 1800 KB

Open AccessArticle

Palm Leaf-Derived Activated Carbon as a Dual Adsorbent–Catalyst for Methyl Orange Removal: Catalytic Oxidation and Kinetic Insights

by Samah Daffalla

C 2026, 12(2), 38; https://doi.org/10.3390/c12020038 - 30 Apr 2026

Viewed by 709

Abstract

A mesostructured activated carbon (PL–AAC) was engineered from palm leaf biomass via a specific chemical activation protocol and systematically evaluated as a bifunctional adsorbent–catalyst for the advanced oxidative removal of methyl orange (MO) from aqueous media. Physicochemical characterization confirmed the successful transformation of [...] Read more.

A mesostructured activated carbon (PL–AAC) was engineered from palm leaf biomass via a specific chemical activation protocol and systematically evaluated as a bifunctional adsorbent–catalyst for the advanced oxidative removal of methyl orange (MO) from aqueous media. Physicochemical characterization confirmed the successful transformation of the lignocellulosic precursor into a hierarchically porous carbon framework, exhibiting enhanced surface area (2 → 56 m²/g), increased pore volume (0.0106 → 0.0227 cm³/g), and a dominant mesopore distribution (~3–5 nm). FTIR analysis revealed the presence of oxygen-containing functional groups (hydroxyl, carbonyl, and carboxyl), while SEM images demonstrated the formation of interconnected pore channels. Nitrogen adsorption–desorption isotherms showed Type IV behavior with H4 hysteresis, confirming the presence of narrow slit-shaped mesopores and micropores. This study introduces the novel application of palm leaf-derived activated carbon as a dual-function material that integrates adsorption and catalytic oxidation within a single system. Under acidic conditions (pH 2–3), PL–AAC in the presence of H₂O₂ achieved near-complete MO removal (≈98–100%), driven by the synergistic interaction between adsorption and in situ generation of reactive hydroxyl radicals. Kinetic analysis revealed that the degradation follows a pseudo-second-order model (R² = 0.916), indicating that surface-mediated interactions govern the process. Furthermore, PL–AAC maintained high catalytic efficiency over four regeneration cycles with negligible performance loss, demonstrating excellent stability and reusability. These findings highlight the effective valorization of palm leaf waste into a sustainable, low-cost, and high-performance material for advanced wastewater treatment applications. Full article

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

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37 pages, 10800 KB

Open AccessReview

Review of the Studies on Chemical Kinetics of C1–C4 Alkanes Combustion in O₂/CO₂ Environment Based on Laminar Burning Velocity, Ignition Delay Times and Species Concentration Measurements

by Sergey Osipov, Vadim Yakovlev, Polina Golosova, Dmitry Pisarev and Andrey Rogalev

C 2026, 12(2), 37; https://doi.org/10.3390/c12020037 - 26 Apr 2026

Viewed by 730

Abstract

Direct-fired supercritical CO₂ cycles are considered a promising way to reduce CO₂ emissions in the energy sector. One of the key elements of such cycles is a combustor, in which natural gas is burned at supercritical pressures up to 300 atm [...] Read more.

Direct-fired supercritical CO₂ cycles are considered a promising way to reduce CO₂ emissions in the energy sector. One of the key elements of such cycles is a combustor, in which natural gas is burned at supercritical pressures up to 300 atm in an O₂/CO₂ environment. Understanding the chemical combustion kinetics of C1–C4 alkanes, the main components of natural gas, in a supercritical CO₂-diluted medium is important for designing such combustors. This article provides an overview of studies on the chemical kinetics of C1–C4 alkanes combustion in CO₂ at ultra-high pressures. It has been established that with increasing pressure, regardless of the diluent, CH₃O₂ and HO₂ chemistries start to significantly influence the combustion of alkanes, but at the moment this influence is not sufficiently understood. Influence of CO₂ dilution on kinetics is mainly thermal, but the chemical effect is also significant. At the same time, the direct chemical effect of CO₂ is more important for the laminar burning velocity, while the indirect third-body effect is more important for the ignition delay time. However, the available literature lacks experimental measurements of the laminar burning velocity in a CO₂ environment at pressures above 70 atm, which limits the current understanding of chemical kinetics at supercritical pressures. Full article

(This article belongs to the Special Issue Hydrogen Energy and Carbon Capture, Utilization and Storage (CCUS))

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23 pages, 3425 KB

Open AccessArticle

Evaluation of Ordered Mesoporous Carbon as a Robust and Efficient Adsorbent for the Removal of Metanil Yellow from Aqueous Solutions

by Bharti Gaur, Jyoti Mittal, Hadi Hassan, Alok Mittal and Richard Thornton Baker

C 2026, 12(2), 36; https://doi.org/10.3390/c12020036 - 24 Apr 2026

Viewed by 1203

Abstract

Metanil Yellow (MY), a highly toxic azo dye used in food products, was removed from aqueous solution using a metal- and halide-free ordered mesoporous carbon (OMC) adsorbent. MY exhibited a strong affinity towards OMC in batch as well as column operations, and OMC [...] Read more.

Metanil Yellow (MY), a highly toxic azo dye used in food products, was removed from aqueous solution using a metal- and halide-free ordered mesoporous carbon (OMC) adsorbent. MY exhibited a strong affinity towards OMC in batch as well as column operations, and OMC performed much better than previously reported adsorbents. The pH, dye concentration, adsorbent dosage, and contact time were optimised, and detailed adsorption experiments were performed under these conditions. Several isotherm models were fitted to the adsorption data, showing that the Langmuir and the Freundlich adsorption models were followed. Adsorption was spontaneous and endothermic at all measurement temperatures. On the basis of pH studies, enthalpy data, and adsorption isotherm analysis, adsorption was determined to be by physisorption. In kinetics studies, the adsorption process was found to be pseudo-second order with interparticle diffusion as the rate-limiting step. Column experiments using a fixed bed of OMC resulted in almost 100% column efficiency and a fractional column capacity of 0.999. During adsorption/desorption cycles of the exhausted column, 99.71% of the dye was recovered after the first cycle and 97.66% after the eleventh. These findings indicate that OMC is a promising and efficient material for the adsorptive removal of toxic MY dye. Full article

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

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29 pages, 4706 KB

Open AccessReview

From Production to Market: Challenges and Opportunities of Graphene-Related Materials

by Gimhani Danushika, Pei Lay Yap, Siavash Aghili, Gurleen Singh Sandhu and Dusan Losic

C 2026, 12(2), 35; https://doi.org/10.3390/c12020035 - 22 Apr 2026

Cited by 5 | Viewed by 5273

Abstract

Graphene-related materials (GRMs) possess exceptional electrical, mechanical, thermal, and surface properties, offering significant potential across broad sectors and applications in electronics, energy storage, composites, and environmental technologies. Despite extensive investment in academic research and translation, large-scale industrial adoption of GRMs remains slower than [...] Read more.

Graphene-related materials (GRMs) possess exceptional electrical, mechanical, thermal, and surface properties, offering significant potential across broad sectors and applications in electronics, energy storage, composites, and environmental technologies. Despite extensive investment in academic research and translation, large-scale industrial adoption of GRMs remains slower than projected. This review systematically analyzes the global graphene manufacturing landscape using available data from 100 commercial producers, with a focused evaluation of manufacturing technology, types and forms of produced GRMs, raw material sources, product forms, industrial quality control and characterization practices. Graphite-based production routes, particularly graphene oxide (GO) and reduced graphene oxide (rGO), dominate in the market due to their scalability and cost advantages. However, substantial inconsistencies in the quality of produced GRMs, characterization and standardization depth, analytical evidence, and technical data sheets (TDSs) remain widespread. A SWOT (strengths, weaknesses, opportunities and threats) analysis of emerging graphene in the industry highlights technological maturity and expanding market demand but reveals critical weaknesses and challenges in quality, standardization and cost–performance alignment. Overall, quality of manufactured materials, quality control transparency, and standardization rather than material manufacturing limitations emerge as the primary barriers to the widespread commercial realization of graphene. Full article

(This article belongs to the Special Issue 10th Anniversary of C — Journal of Carbon Research)

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23 pages, 1630 KB

Open AccessReview

Impact of Microplastics in Biosolids on Carbon Cycling and Food Systems

by Sung Hee Joo

C 2026, 12(2), 34; https://doi.org/10.3390/c12020034 - 21 Apr 2026

Viewed by 1351

Abstract

Microplastics (MPs) are increasingly recognized as persistent, carbon-based contaminants in biosolids produced during wastewater treatment. As biosolids are widely applied to land or disposed of via landfilling and incineration, the incorporation of microplastic-derived carbon into managed and natural ecosystems raises important questions regarding [...] Read more.

Microplastics (MPs) are increasingly recognized as persistent, carbon-based contaminants in biosolids produced during wastewater treatment. As biosolids are widely applied to land or disposed of via landfilling and incineration, the incorporation of microplastic-derived carbon into managed and natural ecosystems raises important questions regarding carbon cycling, organic carbon stability, and long-term environmental implications. This review synthesizes current knowledge on the occurrence, characteristics, and fate of microplastics in biosolids, with particular emphasis on their interactions with native organic matter and their influence on carbon-related processes. This work critically assesses how MPs in biosolids influence carbon dynamics, including their role as a persistent carbon pool, interactions with soil organic matter, effects on microbial activity and decomposition, and implications for carbon sequestration and turnover after land application. The review also considers indirect consequences for food systems and human exposure through carbon-associated pathways. Significant knowledge gaps remain regarding the quantification of microplastic-associated carbon stocks and fluxes, transformation processes during biosolid treatment and soil incorporation, and the long-term persistence of this carbon fraction. Methodological challenges in measuring and reporting MPC are briefly highlighted, alongside their implications for understanding MPs as an emerging component of the terrestrial carbon cycle and for sustainable biosolid management. Full article

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

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29 pages, 3827 KB

Open AccessArticle

Fe/N/C Catalyst Production by Collinear CO₂ Laser Pyrolysis: Toward a Specific Mass-Weighted Energy-Deposited (J.g⁻¹) Parameter Opening Discussion on FeN_x Site Formation

by Henri Perez, Claire Dazon, Pierre Lonchambon, Suzy Surblé, Emeline Charon, Mathieu Frégnaux, Arnaud Etcheberry, Charles Rivron and Olivier Sublemontier

C 2026, 12(2), 33; https://doi.org/10.3390/c12020033 - 15 Apr 2026

Viewed by 1226

Abstract

We report the synthesis of Fe/N/C ORR electrocatalysts by an original collinear CO₂ laser pyrolysis of liquid aerosol droplets in various configurations and compared them to a catalyst synthesized in the classical perpendicular one. While the precursors were always injected at the [...] Read more.

We report the synthesis of Fe/N/C ORR electrocatalysts by an original collinear CO₂ laser pyrolysis of liquid aerosol droplets in various configurations and compared them to a catalyst synthesized in the classical perpendicular one. While the precursors were always injected at the bottom side of the reactor, two collinear configurations of the laser entry into the reactor are considered: by the Top Side (T.S.) or by the Bottom Side (B.S.). The two corresponding catalysts sets show significant different ORR performances. An in-depth XPS analysis and fitting of the N1s spectra allowed for drawing the ORR performance as a function of FeN_x sites components. An original approach considering the energy delivered to a quantity of precursors in J.g⁻¹, linked to the flame temperature feature, evidenced very different conditions for perpendicular CO₂ laser pyrolysis and each of the two collinear configurations. This mass-weighted energy delivered in the classical perpendicular configuration is too low to allow for the formation of FeN_x sites and the resulting ORR performance is extremely poor, suggesting a marginal role of nitrogen species without interaction with iron atoms. In contrast, the delivered mass-weighted energies are sufficient in both collinear configurations to produce FeN_x sites. The ORR performance for catalysts produced in these both configurations is positively correlated with the amount of energy deposited on the precursors. The ORR performance in the T.S. laser configuration is positively correlated to the amount of FeN_x sites. The best performing catalysts obtained in the B.S. configuration show an opposite variation. These trends, and the ORR performance degradation of B.S. catalysts under prolonged chronoamperometry are discussed in light of the effect of temperature on the formation of the various kind of FeN_x sites. A tentative explanation is given, considering that N1s XPS fitting with a single FeN_x component may hinder the fact that Pyridinic sites components may contain a part of FeN_x sites, as suggested by theoretical calculation from the literature. The best catalysts obtained in this work by collinear configuration show similar performances to those obtained by double stage perpendicular pyrolysis previously reported with an ORR onset potential of ~860 mV. Full article

(This article belongs to the Special Issue 10th Anniversary of C — Journal of Carbon Research)

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33 pages, 4051 KB

Open AccessArticle

Carbons from Pistachio Nutshells Activated with Phosphoric Acid and Microwave Treatments: Towards Sustainable Sorbents for Treating Water

by Magdalena Sobiesiak, Monika Parcheta and Rosa Busquets

C 2026, 12(2), 32; https://doi.org/10.3390/c12020032 - 10 Apr 2026

Viewed by 1176

Abstract

Activated carbons are usually prepared from natural precursors (e.g., fruit stones or nutshells) by carbonization and activation processes carried out at 400–1000 °C. They exhibit well-developed porosity, and chemical activation introduces hydrophilic functional groups on their surface, providing excellent sorption properties. However, the [...] Read more.

Activated carbons are usually prepared from natural precursors (e.g., fruit stones or nutshells) by carbonization and activation processes carried out at 400–1000 °C. They exhibit well-developed porosity, and chemical activation introduces hydrophilic functional groups on their surface, providing excellent sorption properties. However, the high temperatures required during thermal treatment increase production costs. In this work, cost-reducing methods for preparing carbon sorbents are proposed. Carbonization of H₃PO₄ activated waste pistachio nutshells was performed using classical pyrolysis (500 or 550 °C, 30 min, N₂ atmosphere) and microwave treatment (power 1000 W, 20 min). The properties of the synthesized carbons were characterized using thermogravimetry and spectroscopic techniques including infrared (ATR), Raman, photoelectron (XPS) spectroscopies, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). Porous structure parameters were determined using nitrogen adsorption experiments. The efficiency of Pb²⁺ removal from spiked ultrapure, tap and river water was evaluated by batch sorption experiments and inductively coupled plasma–mass spectrometry. The most porous carbons were those prepared at 500 and 550 °C, with specific surface areas of 910 and 256 m²/g, respectively. Surface phosphates increased the Pb²⁺ sorption efficiency to 99% from ultrapure water, at an initial concentration of 300 µg Pb²⁺/L. The material obtained with the microwave method was not fully carbonized and remained nonporous, but it also exhibited 99% Pb²⁺ uptake from ultrapure water due to the presence of oxygen-containing surface groups. The Pb²⁺ removal from spiked tap and river water reached up to 84% and 94%, respectively, at the spiking level of 300 µg Pb²⁺/L. Full article

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

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30 pages, 1363 KB

Open AccessReview

Engineered Biochar for the Sequestration of Textile Fibrous Microplastics: From Mechanistic Insights to Rational Functional Design

by Kiara Cruz and Simeng Li

C 2026, 12(2), 31; https://doi.org/10.3390/c12020031 - 7 Apr 2026

Viewed by 1923

Abstract

Microplastic pollution has emerged as a major environmental concern due to its persistence, widespread distribution and potential risks to ecosystems and human health. Among the various types of microplastics, fibrous microplastics (FMPs) account for 60% to 90% of all detected microplastic particles in [...] Read more.

Microplastic pollution has emerged as a major environmental concern due to its persistence, widespread distribution and potential risks to ecosystems and human health. Among the various types of microplastics, fibrous microplastics (FMPs) account for 60% to 90% of all detected microplastic particles in surface waters, primarily originating from synthetic textile production, laundering, and wastewater discharge. Their elongated morphology, high aspect ratio, and complex surface chemistry differentiate them significantly from microplastic fragments or beads, creating unique challenges for effective removal in water treatment systems. In recent years, engineered biochar has attracted increasing attention as a promising and sustainable material for microplastic removal due to tunable pore structure, surface chemistry, and adsorption capacity. However, existing reviews largely discuss microplastic removal in general terms, with limited attention to the distinctive properties of textile FMPs and their implications for biochar design and performance. This review provides a comprehensive and focused analysis of the functional characteristics of biochar that enable the effective removal of textile FMPs in water systems. First, the environmental significance and physicochemical characteristics of textile-derived FMPs are summarized. Next, the major mechanisms governing biochar–microplastic interactions, including physical interception, adsorption, and aggregation processes, are discussed. The review then examines key functional characteristics of engineered biochar, such as pore structure, surface functional groups, hydrophobicity, and composite modifications, that enhance the sequestration of FMPs. Finally, current technological challenges, research gaps, and future directions for developing scalable biochar-based solutions for textile microplastic mitigation are discussed. By linking the unique properties of textile FMPs with the functional design of biochar, this review provides a framework to guide the development of more effective and sustainable treatment strategies for reducing microplastic contamination in aquatic environments. Full article

(This article belongs to the Topic Converting and Recycling of Waste Materials)

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21 pages, 9064 KB

Open AccessArticle

Mathematical Modeling of Soot Formation and Fragmentation of Carbon Particles During Their Pyrolysis Under Conditions of Removal from the Front of a Forest Fire

by Nikolay Viktorovich Baranovskiy and Viktoriya Andreevna Vyatkina

C 2026, 12(2), 30; https://doi.org/10.3390/c12020030 - 1 Apr 2026

Cited by 1 | Viewed by 1069

Abstract

The object of the study is a single heated carbonaceous particle of relatively small size, 0.003 to 0.01 m. Main hypothesis: The formation of soot particles and black carbon particles is caused by the thermochemical destruction of dry organic matter of forest fuel [...] Read more.

The object of the study is a single heated carbonaceous particle of relatively small size, 0.003 to 0.01 m. Main hypothesis: The formation of soot particles and black carbon particles is caused by the thermochemical destruction of dry organic matter of forest fuel and the mechanical fragmentation of coke residue. The aim of the study is to conduct numerical simulations of heat and mass transfer in a single heated carbonaceous particle, taking into account the soot formation process and assessing its fragmentation with regard to heat exchange with the external environment in a 2D setting. As part of this study, a new model of heat and mass transfer in a pyrolyzed carbonaceous particle was developed, taking into account its step-by-step fragmentation (fragmentation tree model with four secondary particle formations from the initial particle). The calculations resulted in the distributions of temperature and volume fractions of phases in the carbonaceous particle across various scenarios. Scenarios of surface fires (initial temperatures of 900 K and 1000 K), crown fires (1100 K), and a firestorm (1200 K) for typical vegetation (pine, spruce, birch) are considered. Cubic carbonaceous particles are considered in the approximation of a 2D mathematical model. To describe heat and mass transfer in the structure of the carbonaceous particle, a differential equation of thermal conductivity with corresponding initial and boundary conditions of the third type is used, taking into account the gross reaction in the kinetic scheme of pyrolysis and soot formation. Differential analogues of partial differential equations are solved using the finite difference method of second-order approximation. Options for using the developed mathematical model and probabilistic fragmentation criterion for assessing aerosol emissions are proposed. Recommendations: The suggested mathematical model must be incorporated with mathematical models of forest fire plume and aerosol transport in the upper layers of the atmosphere. Moreover, probabilistic criteria for health assessment must be developed for the practical use of the suggested mathematical model. Full article

(This article belongs to the Topic Environmental Pollutant Management and Control)

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