Search Results (222)

Considering carbon neutrality and fossil fuel depletion, biomass is becoming increasingly important as a renewable and sustainable energy source. However, understanding of process-dependent characteristics relevant to char production remains limited. This study investigated the carbonization of mushroom waste medium (MWM) via conventional carbonization (CC; i.e., pyrolysis), hydrothermal carbonization (HTC), and microwave-assisted carbonization (MAC), and evaluated their suitability for desired char properties and target applications. For all methods, increasing reaction temperature led to carbon densification, with decreased oxygen and hydrogen contents and increased carbon and fixed carbon fractions. However, the extent of these transformations depended on the reaction environment. HTC achieved carbon enrichment and the highest higher heating value (HHV) at relatively low temperatures. In contrast, CC required higher temperatures to achieve comparable carbonization levels but showed a marked increase in BET surface area at higher temperatures. MAC exhibited intermediate characteristics under moderate conditions. HTC also facilitated potassium and chlorine removal, which may reduce operational issues during thermal utilization. These results indicate trade-offs among carbon densification, char yield, surface structure, and inorganic matter content. Rather than identifying a universally superior process, this study demonstrates that the suitability of each method depends on the desired properties and applications of MWM-derived char, providing a practical basis for appropriate process selection. Full article

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 study demonstrates the rapid microwave-assisted upcycling of diverse bio-wastes—including aloe vera industrial leaf waste (av), corn cob agricultural residues (cc), and soft slaughterhouse (sh) by-products (pork liver, lung, and heart) into high-surface-area activated carbons for efficient hexavalent chromium removal via ZnCl₂-activated microwave pyrolysis. To process the challenging high-moisture animal organs, a hybrid approach combining microwave-assisted hydrothermal pre-treatment with subsequent ZnCl₂-activated microwave pyrolysis was developed to promote chemical dehydration and aromatic network development. Structural characterization by N₂ porosimetry, FT-IR, Raman, and XRD confirmed the formation of stable, amorphous porous networks, with surface development strongly dependent on both precursor type and pyrolysis temperature. The materials exhibited high specific surface areas (BET) of 1442, 1120, and 775 m²/g for cc, av, and sh, respectively, and they also demonstrated high water dispersibility. Cr(VI) adsorption data were best described by the Langmuir isotherm model, while thermodynamic analysis confirmed the spontaneous and endothermic adsorption process. The maximum adsorption capacities (qmax) at pH 3 were 157, 112, and 71 mg/g for the activated carbons derived from cc, av, and sh, respectively. Agricultural-derived carbons exhibited superior adsorption performance, whereas all materials remained competitive, demonstrating a potential sustainable circular-economy strategy for waste valorization. Full article

Carbon-based materials like activated carbon (AC) are frequently applied for water treatments and remediation. The increasing use and functionalization of AC, especially with the recent mandate to implement quaternary treatments to remove organic micropollutants (Directive 2024/3019), may inadvertently introduce AC or leachate products to aquatic bodies. Such occurrences pose potential risks to inhabiting organisms, which have been understudied. This study assessed the environmental safety of an AC obtained from spent brewery grains (SBG)—a lignocellulosic biomass—through microwave pyrolysis with potassium carbonate activation. The resulting AC (SBG-AC) was washed, sieved (powder, particle size ≤ 180 µm), and tested for its ecotoxicological effects on the marine mussel Mytilus galloprovincialis at doses of 5, 25, and 50 mg/L. After 28 days of exposure (with weekly water renewal), biochemical parameters related to the mussels’ metabolic capacity and oxidative status were evaluated. Exposure to SBG-AC stimulated the energy metabolism in M. galloprovincialis, at the expense of internal energy reserves (such as glycogen). Although SBG-AC exposure induced antioxidant responses, the significant increase in lipid peroxidation and protein carbonylation at the higher doses (particularly 50 mg/L) suggests that these protective mechanisms were insufficient to prevent oxidative damage. Overall, while SBG-AC offers an effective alternative for water treatment, its ecotoxicity at higher doses raises concerns, emphasizing the need for careful risk assessment and containment measures. Full article

The conversion of waste textiles into valuable products is an effective route to mitigate low-value solid waste accumulation and recover energy. In this work, nickel and potassium were introduced into textile waste via an impregnation method, and their roles in microwave-assisted catalytic pyrolysis were investigated with a focus on hydrogen production. The results show that co-loading 1 wt.% Ni and 0.4 wt.% K significantly enhances gas formation, with a total gas yield of 67.47% and a hydrogen yield of 52.57 mmol/g. Hydrogen production was markedly improved compared with the untreated textiles, the physical mixing methods, and the conventional pyrolysis. Structural characterization by XRD and SEM mapping confirmed that K addition effectively suppressed the agglomeration of Ni species. FTIR analysis suggests that a synergistic catalytic effect between K and Ni promotes the conversion of macromolecular components into smaller gaseous products. The improved hydrogen production can be associated with the combined effect of enhanced Ni dispersion and promoted decomposition reactions. This work provides new insights into the design of alkali-promoted Ni catalysts for efficient hydrogen production from textile waste under microwave pyrolysis conditions. Full article

FeAl_xO_y powders, fabricated by solution combustion synthesis (SCS), are promising catalysts for microwave-assisted pyrolysis of methane. However, the effects of SCS parameters on the pyrolysis are not well understood. In the present work, two fuels (citric acid and glycine), two Fe:Al molar ratios, and two heating modes (a hotplate and a muffle furnace) are tested. All catalysts exhibit CH₄ conversion of around 70% and H₂ composition of about 93%. The process is one to two orders of magnitude more efficient than conventional pyrolysis. Increasing the Fe:Al ratio from 1:1 to 2:1 and using a hotplate improve H₂ generation efficiency. Use of glycine decreases the CO₂:H₂ ratio, but citric acid yields more readily reducible products due to differences in phase evolution, detected by X-ray diffraction analysis. Scanning electron microscopy and energy-dispersive X-ray spectroscopy reveal carbon nanotubes and exsolution of Fe. FeAl_xO_y catalysts, prepared via incipient wetness impregnation, are ineffective. Full article

Nitrogen and phosphorus are the primary pollutants responsible for eutrophication in water bodies, and their effective removal is crucial for water environmental protection. Biochar, owing to its porous structure and surface functional groups, exhibits excellent adsorption performance for nitrogen and phosphorus, which can be significantly enhanced through metal modification. In this study, magnetic biochar (MBC) was prepared from spent mushroom substrate via FeCl₃ impregnation and microwave pyrolysis, and its adsorption performance for NH₄⁺ and PO₄³⁻ was systematically evaluated. The physicochemical properties of MBC were characterized using scanning electron microscopy, thermogravimetric analysis, specific surface area and pore structure analysis, vibrating sample magnetometry, and Fourier transform infrared spectroscopy. The results showed that the saturated magnetization of MBC was 7.86 emu/g, the specific surface area was 37 m²/g, and the material exhibited a mesoporous structure with high thermal stability. The adsorption process followed pseudo-second-order kinetics, and the mechanisms involved electrostatic interactions, surface complexation, and pore filling. Isotherm studies indicated that the maximum adsorption capacities of MBC for NH₄⁺ and PO₄³⁻ were 16.25 mg/g and 14.99 mg/g, respectively. Thermodynamic analysis revealed that the adsorption of NH₄⁺ was exothermic, whereas that of PO₄³⁻ was endothermic. Furthermore, MBC maintained an adsorption efficiency of up to 93% after ten adsorption–desorption cycles, demonstrating excellent reusability. Full article

Biomass-derived carbon-based electromagnetic wave (EMW) absorbers have attracted significant attention for their abundant availability and environmentally friendly characteristics. A novel strategy combining biomass templates with a ZIF-67-assisted approach was developed to fabricate Co₃O₄@C composites via pyrolysis. This work demonstrates that the intrinsic structure of biomass templates can be effectively leveraged to regulate both the microstructure and the electromagnetic properties of the resulting composites, enabling tunable microwave absorption performance. Among the prepared samples, M3 exhibits the lowest reflection loss (RL) of −54.79 dB at a thickness of 4.61 mm, and achieves an effective absorption bandwidth (EAB) of 3.43 GHz at 2.82 mm. This superior performance originates from the synergistic optimization of impedance matching and the coupling of dielectric and magnetic loss mechanisms. The porous biomass-derived carbon framework not only enhances multiple scattering and impedance matching but also provides abundant interfaces to induce strong interfacial and dipole polarization. Meanwhile, the uniform in situ growth of ZIF-67-derived Co₃O₄ nanoparticles introduces enhanced magnetic loss through exchange resonance, while structural defects further promote multiple dielectric relaxation processes. This study presents a novel waste-to-value strategy for the rational design of hierarchical composite absorbers, offering high-performance EMW absorption while demonstrating a low-cost, environmentally friendly, and scalable route for converting natural wood waste into functional materials. This work not only provides new insights into constructing high-performance, lightweight, and cost-effective EMW-absorbing materials but also aligns with the principles of sustainable development, resource efficiency, and green chemistry. Full article

A lightweight and high-efficiency microwave-absorbing material was developed via an in situ solvothermal pyrolysis strategy by anchoring sphere-like Fe₃O₄ nanostructures onto bamboo-derived porous carbon (BPC). The resulting composites preserve the intrinsic anisotropic honeycomb architecture of bamboo while introducing uniformly distributed magnetic nanoparticles, enabling synergistic dielectric–magnetic loss. Electromagnetic parameters, alongside impedance matching, were successfully modulated through the optimization of precursor concentrations. Of the evaluated materials, BPC-0.9 stood out for its intense attenuation, recording an RL_min of −45.17 dB at a 1.8 mm thickness. Furthermore, a significant effective absorption bandwidth of 6.65 GHz was attained by the BPC-0.6 sample at only 2.2 mm. Several factors contribute to the boosted efficiency, starting with conductive and interfacial polarization losses paired with multiple scattering events. Furthermore, magnetic loss components, encompassing eddy current effects as well as natural and exchange resonances, play a pivotal role in optimizing the material’s response. Furthermore, radar cross-section (RCS) modeling reveals a substantial reduction of 19.9 dB·m², verifying the material’s viability for real-world stealth technologies. Our findings offer a straightforward methodology for fabricating magnetic carbon structures from biomass with adjustable dielectric responses, underscoring their potential in high-performance energy conversion and low-density microwave absorption. Full article

The accelerating generation of waste streams is observed globally. Spanning lignocellulosic biomass, plastic waste, sewage sludge, and industrial residues, this review presents both an urgent management challenge and a compelling materials opportunity. Carbon materials derived from these waste streams offer a sustainable route to functional carbons applicable in electrochemical energy storage, adsorption, heterogeneous catalysis, and high-temperature applications. Yet their rational design remains constrained by incomplete understanding of the relationships between feedstock composition, processing pathway, structural characteristics, and functional performance. This review provides an integrated analysis of waste-derived carbon materials from processing pathways to structure–property–function relationships. The principal feedstock categories are examined for their compositional characteristics and implications for carbon yield and structure. Five primary processing routes are assessed. The five routes examined are pyrolysis, hydrothermal carbonisation, physical and chemical activation, and microwave-assisted processing. They are assessed comparatively with emphasis on structural outcomes and governing parameters. The resulting structural characteristics are discussed. These are morphology, hierarchical pore architecture, surface chemistry, heteroatom doping, and crystallinity. They are discussed alongside their characterisation methods and known limitations as performance predictors. Structure–property relationships are examined quantitatively. Heteroatom-doped hierarchical porous carbons achieve 612 F/g specific capacitance. Turbostratic hard carbons deliver 450 mAh/g sodium storage with over 90% retention. Hierarchical porous carbons demonstrate CO₂ uptake of 5.0 mmol/g and dye adsorption exceeding 9000 mg/g under optimised laboratory conditions; these values reflect individual studies and are not directly comparable across systems. Biomass-derived sulfonated carbon catalysts sustain biodiesel yields above 90% over multiple cycles. Challenges of feedstock variability, process scalability, environmental compliance, and economic feasibility are addressed, and machine learning-guided design, standardised characterisation methodology, and circular economy policy frameworks are identified as key enablers for translating laboratory performance into industrial reality. Full article

Effective management of organic wastes is essential for green and low-carbon development. Conventional technologies, including incineration, pyrolysis, hydrothermal carbonization (HTC), gasification, anaerobic digestion (AD), and composting, have supported waste reduction and basic resource recovery, but they remain limited in high-efficiency conversion and high-value utilization. This review comparatively evaluates these conventional routes together with advanced and intensified technologies, including microwave-assisted pyrolysis (MAP), plasma treatment, supercritical water gasification (SCWG), and flash joule heating (FJH), with emphasis on suitable feedstocks, performance characteristics, application boundaries, and integration potential. In general, wastes with high moisture content are more suitable for HTC, AD, and SCWG, whereas relatively dry wastes and wastes with high carbon content are more suitable for pyrolysis, gasification, plasma treatment, and FJH upgrading. The review also discusses representative integrated pathways, such as HTC-SCWG, pyrolysis and plasma coupling, AD and gasification coupling, and pyrolysis and FJH coupling, which may improve carbon conversion, broaden product portfolios, and reduce residual pollutants. However, large-scale implementation is still constrained by feedstock heterogeneity, heat and mass transfer limitations, catalyst deactivation, reactor corrosion, and system cost. Overall, no single technology is universally optimal; technology selection should depend on feedstock properties, moisture content, and target products. Full article

Developing lightweight materials that simultaneously achieve efficient electromagnetic wave absorption and robust corrosion resistance remains a significant challenge for marine stealth and electromagnetic protection applications. The main obstacle lies in the rational integration of electromagnetic attenuation capability, impedance matching, and corrosion protection. In this work, a multilayer carbon-structured BaTiO₃@C nanocomposite (CSTB-x) was successfully fabricated via freeze-drying combined with in situ pyrolysis. During the carbonization process, chitosan (CS) was transformed into a nitrogen-doped multilayer porous carbon framework, while BaTiO₃ particles were embedded into the carbon matrix to construct a BaTiO₃@C heterostructure. Benefiting from optimized impedance matching and the synergistic contributions of conduction loss, dipolar polarization, and interfacial polarization, CSTB-1.0 delivered a minimum reflection loss (RL_min) of −48.07 dB at 6.16 GHz with a thickness of 3.32 mm, and achieved a maximum effective absorption bandwidth (EAB) of 7.04 GHz at a thickness of 1.88 mm. In addition, CSTB-1.0 exhibited a low corrosion current density (8.93 × 10⁻⁶ A/cm²) and a high polarization resistance (7.87 × 10³ Ω∙cm²), indicating excellent corrosion protection performance. The enhanced corrosion resistance is mainly attributed to the barrier effect of the multilayer carbon framework and the tortuous diffusion pathways generated by the porous and core–shell structures. Moreover, the material showed a minimum radar cross-section (RCS) value of −41.25 dBsm, demonstrating remarkable electromagnetic scattering suppression capability. These results provide a feasible strategy for the design and fabrication of marine stealth materials with integrated microwave absorption and corrosion resistance. Full article

Microwave-assisted pyrolysis (MAP) has emerged as a revolutionary technology for converting solid waste into high-value hydrocarbons. However, conventional pyrolysis and traditional single-function catalysts often face an inevitable “performance trade-off” involving severe mass transfer resistance, poor microwave absorption, and rapid coking. This review systematically summarizes the recent evolution of catalyst design toward advanced multi-site composites. It highlights the synergistic mechanisms of integrating microwave-responsive cores, hierarchical pore networks, and metal-acid bifunctional sites to achieve ultrafast localized heat transfer, targeted bond cleavage, and in-situ coking suppression. Furthermore, this paper critically examines current bottlenecks in scaling MAP to industrial levels. To address these challenges, we discuss emerging solutions, including hydrogen-enriched co-pyrolysis, non-destructive in-situ regeneration, and the integration of machine learning frameworks for intelligent process optimization. Full article

This research systematically investigated the catalytic pyrolysis of Arab Heavy (AH) and Arab Light (AL) crude oils using NiO supported on Al₂O₃ or ZSM-5 in a microwave-assisted reactor, with particular emphasis on hydrogen (H₂) generation and value-added chemicals. To understand how both the catalyst and feedstock affect reaction products, gas and liquid products as well as catalyst activity were carefully examined. The production of H₂ and olefins was significantly enhanced by the NiO/Al₂O₃ catalyst, especially when using AL crude. This is most likely due to favorable metal-support interactions that increase the dehydrogenation activity. However, when paired with lighter feedstock, NiO/ZSM-5 greatly increased paraffin production and encouraged light alkane synthesis in both phases. GC-MS and FTIR spectroscopy confirmed that NiO/Al₂O₃ produced liquid products richer in aromatics while also containing a significant fraction of paraffins. Remarkably, the AL over NiO/Al₂O₃ combination showed very little liquid recovery, indicating that gas generation was higher in these reaction conditions. These results showed how H₂ selectivity and hydrocarbon routes in NiO/ZSM-5 and NiO/Al₂O₃ are controlled by various microwave-catalyst interactions. This work further highlights the importance of matching catalyst properties with feedstock type to control product selectivity, with NiO/Al₂O₃ showing particular promise for H₂-focused applications. Full article

The co-pyrolysis of Chlorella vulgaris (CV) and Eucalyptus branches (EP) offers a promising strategy to enhance bio-oil yield, improve resource utilization efficiency, and alleviate environmental pressures. In this study, the microwave-assisted co-pyrolysis of CV and EP at a mass ratio of 2:1 was investigated, focusing on the catalytic performance of Ni-X (X = Mg, Cu, Fe) bimetallic modified HZSM-5 zeolites. The effects of these catalysts on pyrolysis characteristics, product distribution, and bio-oil composition were systematically evaluated. Experimental results showed that the 15% Ni-Cu/HZSM-5 catalyst exhibited the best catalytic performance, achieving the highest bio-oil yield of 16.83%; it also elevated the R_m to 0.0687 wt.%/s and reduced T_s to 2084 s. Composition analysis revealed that Ni-Cu/HZSM-5 significantly promoted the formation of hydrocarbons, increasing their relative content from 11.59% (C2E1 Group) to 28.92%, while effectively suppressing the formation of nitrogen-containing compounds, reducing their content by 5.05%. Based on these results, a possible reaction pathway is proposed in which the Ni-Cu/HZSM-5 catalyst may enhance heteroatom removal through hydrodeoxygenation (HDO) at the Ni-Cu sites, followed by cracking and aromatization at the HZSM-5 acid sites. This effect may be complemented by preferential adsorption of oxygenated intermediates over nitrogen-containing species, which could help suppress the formation of nitrogenous heterocycles. This work provides theoretical guidance for the application of bimetallic zeolite catalysts in microalgae/lignocellulose co-pyrolysis, alongside a viable pathway for valorizing Eucalyptus by-products to produce high-quality bio-oil. Full article