Search Results (747)

This study investigates the synthesis and kinetic behavior of a magnetic biochar derived from avocado seed biomass for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions. Magnetite (Fe₃O₄) was synthesized through different routes, including nitrogen-assisted coprecipitation, redox-controlled coprecipitation, polyol, sol–gel, and sonochemical methods, to evaluate their structural properties and iron incorporation efficiency. Based on compositional and crystallographic analyses, the coprecipitation under an inert atmosphere exhibited improved phase purity and higher Fe₃O₄ content, which was selected for in situ incorporation onto biochar produced by pyrolysis at 450 °C. The resulting magnetic material and composite were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS), confirming the suitability of the synthesis method and the successful deposition of magnetite onto the porous carbon matrix while preserving its structural integrity. Batch adsorption experiments were conducted at pH 2.0 to evaluate the effect of adsorbent dose and initial Cr(VI) concentration. The adsorption process reached equilibrium within 120 min and was better described by the pseudo-second-order kinetic model (R² ≥ 0.98), suggesting that chemisorption governs the rate-controlling step, with diffusion phenomena contributing but not dominating the overall mechanism. The maximum adsorption capacity predicted by the kinetic model reached 42.49 mg g⁻¹ at an initial concentration of 100 mg L⁻¹. The results demonstrate that avocado-seed-derived magnetic biochar represents a sustainable and effective material for chromium-contaminated water treatment, integrating agro-industrial waste valorization with enhanced adsorption performance and magnetic separability. Full article

Bagasse, owing to its low cost and high carbon yield, is a promising precursor for hard-carbon anodes in sodium-ion batteries (SIB). Regulating the microcrystalline state and pore architecture during pyrolysis is key to boosting Na⁺ storage behavior. Here, the pyrolysis kinetics is controlled via stepwise carbonization to construct a defect-ordered island structure within the cellulose-derived carbon skeleton. Retaining sp³-hybridized carbon at low temperatures creates the Na⁺ channel, while acid cleaning selectively dissolves residual metal oxides, removing the electrochemical inert phase and promoting improved ion diffusion. This process also enriches active sites and interlayer spacing in the hard carbon, boosting capacity in the plateau region. In addition, the ash-catalyzed formation of local sp² graphite microcrystals provides electron transport nodes, optimizing Na⁺ diffusion and electronic conductivity. Accordingly, the assembled SIB achieves a high reversible capacity of 378 mAh g⁻¹ at 0.1C and an initial coulombic efficiency of 97%, with the plateau capacity accounting for 59.1% of the total reversible capacity. This work presents a universal thermochemical approach for engineering high-performance carbon anodes with high closed porosity from low-cost biomass precursors, advancing the development of sustainable and efficient SIBs. Full article

This study presents a definitive framework for Cocos nucifera (coconut) shell valorization, integrating high-resolution thermogravimetry with advanced machine learning. Physicochemical analysis confirms a high-energy feedstock (45.7% carbon, 71.5% volatiles), with SEM/XEDS and FTIR revealing heterogeneous, lignocellulosic, catalytic-rich structural matrix. TG/DTG analysis identified distinct degradation windows: hemicellulose (135–395 °C), cellulose (270–430 °C), and protracted lignin decomposition (275–675 °C). Kinetic modeling indicates that pyrolysis follows a third-order (F3) continuous degradation mechanism across the studied range, supported by high correlation coefficients (R² = 0.93–0.96). The mean kinetic and thermodynamic parameters—specifically an activation energy of 165 kJ·mol⁻¹ (calculated across the 10–60 wt% conversion range during hemicellulose and cellulose pyrolysis), a positive activation enthalpy (159 kJ·mol⁻¹), and a Gibbs free energy of activation (155 kJ·mol⁻¹)—suggest that the thermochemical conversion of coconut shell is an endothermic, non-spontaneous process with moderate energy requirements. Furthermore, the integration of kNN machine learning yielded near-perfect predictive metrics (R² ≈ 1.000) using optimized hyperparameters (k = 85 for TG, k = 100 for DTG, and k = 50 for conversion). These findings suggest that coconut shells can be efficiently valorized as a high-energy feedstock, with data enabling reliable and optimized prediction of thermal degradation to minimize experimental waste. Full article

Formic acid (FA) has emerged as a promising liquid hydrogen storage material, yet efficient photothermal dehydrogenation catalysts with high activity and H₂ selectivity remain challenging. Herein, a polymetallic synergistic PdCu/M-ZNC (where M represents the co-doped In, Sn and Mo species) is fabricated by molten-salt-assisted pyrolysis of ZIF-8 precursors followed by metal incorporation. The unique molten salt environment effectively preserves the porous architecture of ZIF-8, enabling the secure anchoring of PdCu alloy nanoparticles onto the carbonaceous matrix enriched with M-Nₓ coordination sites. Under light irradiation, the PdCu alloy sites kinetically accelerated the overall adsorption and activation of FA molecules. Based on empirical observations and corroborated by the established literature, this alloying effect was inferred to facilitate the C-H bond cleavage and HCOO* desorption processes. Concurrently, the M-Nₓ sites act as efficient electron transfer channels, facilitating the rapid coupling of photogenerated electrons with protons (H⁺) to evolve H₂. Consequently, the optimal catalyst exhibits an enhancement in gaseous product yield (404.46 mmol/g/h) and H₂ selectivity (67.49%) at 75 °C. This work offers a catalyst design that aligns with several principles of green chemistry: it maximizes the atom utilization of precious Pd, incorporates synergistic non-precious metals within MOF-derived frameworks to enhance stability, and leverages solar energy to drive hydrogen production under mild conditions, presenting a more sustainable pathway for hydrogen release from liquid carriers. Full article

Mechanically activated pyrite plays an important role in gold extraction and coal utilization, but its reactivity may change markedly during storage. This study investigates how air deactivation during storage affects the crystal structure and subsequent thermal decomposition behavior of mechanically activated pyrite. Pyrite was mechanically activated and then stored in air for 0, 7 and 180 days. X-ray diffraction (XRD) combined with Rietveld refinement was used to characterize variations in lattice parameters and unit-cell-related structural features, while non-isothermal thermogravimetric–differential scanning calorimetry (TG-DSC) under an argon atmosphere, together with the Flynn–Wall–Ozawa (FWO) method, was applied to evaluate the decomposition kinetics. Air deactivation induced a non-monotonic evolution of lattice parameters and unit-cell volume, which is attributed to combined effects of residual stress relaxation and air-induced surface-related modification during storage. All samples exhibited two mass-loss stages during heating, reflecting stepwise thermal decomposition, and their decomposition behavior varied systematically with deactivation time. The apparent activation energy depended on both conversion fraction and deactivation degree, and nucleation-and-growth-type mechanisms were found to dominate the decomposition process, with their relative contributions evolving with storage time. These results clarify how prior air-deactivation history influences the structural evolution and subsequent thermal decomposition behavior of mechanically activated pyrite and provide useful insight for its storage and utilization in related processes. Full article

Excessive phosphorus discharge from aquaculture effluent significantly contributes to coastal eutrophication, while conventional adsorbents exhibit limited phosphorus removal efficiency in high-salinity, weakly alkaline seawater effluent. This study developed iron/calcium co-modified chlorella biochar (FCBC) through co-impregnation and high-temperature pyrolysis, optimizing the preparation process via the Box–Behnken response surface method. The optimal conditions were identified as an iron concentration of 2.5 mol/L, a calcium concentration of 2.0 mol/L, a pyrolysis temperature of 717 °C, and a duration of 113 min. Under these conditions, FCBC achieved a phosphorus removal rate of 93.23% within 3 h, which was significantly higher than that of the unmodified Chlorella biochar (BC, <8% within the same reaction time). The Fe/Ca co-modification endowed FCBC with a positively charged surface, an increased average pore size of 22.773 nm, and good magnetic responsiveness (saturation magnetization of 6.68 emu·g⁻¹). FCBC demonstrated remarkable adaptability, achieving over 97% phosphorus removal across a pH range of 3 to 11, salinity levels of 5 to 40‰, and phosphorus concentrations of 1 to 15 mg/L. Its adsorption kinetics conformed to pseudo-second-order kinetics (R² = 0.987) and the Freundlich model (R² = 0.971), with efficient phosphorus removal primarily attributed to iron–calcium synergistic effects. FCBC presents significant potential for phosphorus treatment in marine aquaculture effluents. Full article

In this study, chicken bone biochar (CBC) was prepared from waste chicken bones via oxygen-limited pyrolysis. A magnetic component (Fe₃O₄) was introduced, and the composite was embedded in a sodium alginate (SA) gel network, successfully constructing magnetic chicken bone biochar/sodium alginate composite gel beads (M-CBC/SA). The experimental results showed that under the conditions of pH = 4.5, 25 °C, and an adsorbent dosage of 0.5 g/L, the removal efficiency of M-CBC/SA toward 50 mg/L U(VI) reached 91.67%, corresponding to an adsorption capacity of 91.67 mg/g. The adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm model, with a theoretical maximum adsorption capacity of 322.58 mg/g, indicating that the adsorption was dominated by monolayer chemisorption. The material exhibited excellent magnetic separability and good anti-interference ability against coexisting ions such as K⁺, Na⁺, Cl⁻, and SO₄²⁻, and its adsorption behavior was only weakly affected by ionic strength. Characterization by XRD, FTIR, XPS, SEM-EDS and other techniques revealed that the immobilization mechanism of U(VI) involved the synergistic effects of dissolution–precipitation (the formation of a new autunite phase), surface complexation (involving hydroxyl and phosphate groups), ion exchange (exchange with Ca²⁺), and electrostatic attraction. Using waste chicken bones as the raw material, this composite achieves both efficient uranium immobilization and convenient magnetic separation, fully embodying the environmental concept of “treating waste with waste”, and shows promising application prospects in the treatment of uranium-containing wastewater. Full article

Semi-coking wastewater generated during coal pyrolysis contains extremely high concentrations of refractory organic pollutants, resulting in elevated chemical oxygen demand (COD) and posing significant environmental risks, making efficient COD removal a critical challenge for sustainable wastewater treatment in the coal chemical industry. In this study, a porous carbon-based resin (XDA-1G) was investigated as an adsorbent for COD removal from semi-coking wastewater. The adsorption performance and underlying mechanisms were systematically evaluated through adsorption isotherm, kinetic, and thermodynamic analyses, combined with structural characterization using FTIR, XPS, BET, XRD, and SEM–EDS. The resin exhibited a high COD removal efficiency of up to 91% with a maximum adsorption capacity of 2182 mg g⁻¹. Kinetic analysis followed the pseudo-second-order model, while the Freundlich isotherm best described the equilibrium behavior, indicating heterogeneous adsorption. Thermodynamic parameters confirmed that the adsorption process is spontaneous and endothermic. Spectroscopic and structural analyses revealed that COD removal is mainly governed by synergistic mechanisms including π–π interactions between aromatic pollutants and the carbon framework, hydrogen bonding with oxygen-containing functional groups, and pore filling within the hierarchical porous structure. These findings demonstrate the strong potential of porous carbon-based resins as efficient adsorbents for treating high-strength industrial wastewater. Full article

The valorization of biomass waste into advanced electrode materials presents a promising pathway toward sustainable electrochemical energy storage. Herein, a silicon-doped carbon material (Si-CTS-Carbon) is synthesized from chitosan via an in situ reaction with silicon tetrachloride (SiCl₄) and subsequent controlled pyrolysis. When evaluated as an anode for lithium-ion batteries (LIBs), Si-CTS-Carbon exhibits a high reversible capacity of 509.2 mAh g⁻¹ with 99% capacity retention after 100 cycles at 0.05 A g⁻¹. For sodium-ion battery (SIB) applications, it achieves a stable reversible capacity of 155.4 mAh g⁻¹ under identical conditions. Structural and electrochemical analyses reveal that the robust C–O–Si covalent network effectively accommodates volume variation of silicon and enhances structural integrity during cycling. Furthermore, the hierarchically porous architecture shortens ion diffusion pathways, leading to improved Li⁺/Na⁺ transport kinetics. This work demonstrates a viable strategy for fabricating high-performance battery anodes by synergistically doping silicon into biomass-derived carbon, enabling practical biowaste valorization for energy storage. Full article

This review critically evaluates current PA6 recycling technologies, with a specific focus on caprolactam-oriented chemical recycling pathways, including hydrolysis, pyrolysis, glycolysis, ammonolysis, hydrothermal treatment, ionic-liquid-assisted depolymerization, and microwave-assisted processes. Reported caprolactam yields vary significantly depending on reaction conditions and catalyst systems, ranging from below 60 wt% in conventional hydrolysis to above 90 wt% under optimized catalytic, hydrothermal, or microwave-assisted conditions. Among these approaches, microwave-assisted hydrolysis and catalytic depolymerization have emerged as particularly promising, offering substantially reduced reaction times (minutes rather than hours), improved energy efficiency, and high monomer selectivity at moderate temperatures (typically 200–350 °C). This review integrates kinetic modeling approaches, analytical methods for monitoring depolymerization, and downstream separation considerations that govern monomer purity and recyclability. Key challenges, including energy demand, feedstock contamination, scalability, and economic competitiveness, are critically discussed in relation to industrial implementation. Overall, hydrolysis-based and microwave-assisted chemical recycling routes are the most viable pathways for closed-loop recycling of PA6. Future progress will rely on integrated reaction–separation–repolymerization designs, catalyst optimization, and process intensification to enable sustainable and industrially relevant PA6 circularity. Full article

Within a waste biorefinery framework, integrating agro-industrial by-products into the circular economy requires a detailed understanding of the thermochemical conversion behaviour of low-grade carbonaceous materials. This study evaluates the co-pyrolysis characteristics of Soma lignite (SL) and pectin-rich sugar beet pulp (SBP) as a sustainable route for upgrading these resources into clean energy carriers. Interactions between the two feedstocks were analysed by thermogravimetric measurements, triple-region kinetic modelling, and quantitative synergy indices at six mixing ratios, including the pure samples (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 wt% SL:SBP). The Reactivity Index ($R_{\mathrm{m}}$) increased from 0.97 × 10⁻⁴ s⁻¹K⁻¹ for pure SL to 8.65 × 10⁻⁴ s⁻¹K⁻¹ for the 20:80 blend, showing that SBP acts as a highly reactive biomass component that accelerates devolatilisation in the main pyrolysis region. Synergy analysis indicated a shift from inhibitory behaviour in coal-rich blends to slightly positive synergy in SBP-rich mixtures, with the onset of positive $\Delta TC$ around 60 wt% SBP under the present single-heating-rate, non-replicated TGA conditions. This tentative threshold-like behaviour suggests that a critical level of literature-supported, hypothesised hydrogen-donating biomass radicals may be required to overcome the structural resistance of the coal matrix. Within these experimental limitations, the apparent macro-kinetic deviations and first-order Arrhenius parameters suggest that SL/SBP co-pyrolysis follows a complex, non-additive pathway that should be further validated by multi-heating-rate and product characterisation studies in future work. The primary contribution of this work lies in proposing this distinct threshold-like biomass fraction at the macro-kinetic level that governs the transition from heat-transfer-limited antagonism to radical-influenced synergy in low-rank coal and pectin-rich biomass blends. Overall, the combined $\Delta TC$, $\Delta E$ and $R_{\mathrm{m}}$ descriptors provide useful macro-kinetic benchmarks for guiding the optimisation of thermochemical processes for low-grade carbonaceous resources. Full article

Carbon-based bifunctional oxygen electrocatalysts with rationally designed architectures are essential for high-performance rechargeable zinc–air batteries (ZABs), yet the concurrent optimization of catalytic activity, durability, and mass transport remains challenging. Herein, hierarchical ZnCo carbon nanofibers/carbon nanotubes (CNFs@CNTs) are fabricated via single-nozzle electrospinning followed by melamine-assisted pyrolysis under a ZnCl₂-regulated atmosphere. During thermal treatment, Co species embedded within carbon nanofibers catalyze in situ carbon nanotube growth, while ZnCl₂ vapor modulates the carbonization process and surface chemistry, collectively generating a hierarchical CNFs@CNTs architecture with high surface area and abundant exposed active sites. As a result, ZnCo CNFs@CNTs exhibit outstanding bifunctional ORR/OER activity, surpassing Zn-free and Co-free counterparts. Combined structural and electrochemical analyses reveal that the synergistic interaction between Co active centers and Zn-assisted carbon structural regulation enhances reaction kinetics and long-term stability. When implemented as air electrodes in rechargeable ZABs, ZnCo CNFs@CNTs deliver high power density, reduced charge–discharge polarization, and excellent cycling durability, demonstrating strong practical applicability. This work presents an effective strategy for constructing hierarchical CNFs@CNTs composites via electrospinning and dual-component thermal regulation, offering new insights into the design of high-efficiency bifunctional air electrodes for advanced ZABs. Full article

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

Steam Explosion (SE) is a relatively newly developed physicochemical pretreatment method that has received increasing attention since it can effectively upgrade biomass for further utilization. During SE, biomass is first exposed to high-temperature, high-pressure steam and then rapidly depressurized. This process efficiently breaks down the lignocellulosic structure, reduces moisture content, and increases fixed carbon and calorific value. It also enhances biomass grindability and densification, making it more suitable as a renewable solid fuel. This review carefully discusses the fundamental principles of SE and its effects on particle characteristics. Then, the types of SE reactors (mainly composed of batch reactors and continuous reactors) are systematically compared, and the challenges in scaling up and commercialization are discussed. Also, the characteristics of pyrolysis or gasification of biomass pretreated by SE are described in detail. Studies indicate that SE is beneficial for the enhancement of product quality. Finally, the prospects and future challenges in the development of SE (including superheated steam explosion, reaction kinetics improvement, and heat and mass transfer intensification) are presented and discussed. Full article

The presence of pharmaceutical residues, such as ibuprofen, in aquatic environments poses a growing environmental challenge due to their persistence and potential ecotoxicological effects. In this study, a novel biohybrid composite based on pyrolysed rice husk (biochar) modified with Bacillus cereus cells was developed for the efficient removal of ibuprofen from aqueous solutions. The material was comprehensively characterised using SEM, BET, TGA, CHN analysis, and FTIR spectroscopy. Pyrolysis significantly increased the surface area (up to 300 m² g⁻¹) and porosity compared to raw rice husk, while bacterial immobilisation introduced additional functional groups, enhancing surface heterogeneity. Batch adsorption experiments demonstrated a clear improvement in adsorption capacity in the order of rice husk < biochar < composite. The maximum Langmuir adsorption capacities were 4.86, 11.68, and 13.73 mg g⁻¹ for rice husk, biochar, and the composite, respectively. Isotherm modelling indicated that ibuprofen adsorption was best described by the Langmuir and the Freundlich models, suggesting a combination of monolayer adsorption and heterogeneous surface interactions. Isotherm analyses (D–R energy values < 9 kJ mol⁻¹) indicate that ibuprofen removal occurs predominantly through physisorption, governed by π–π interactions, hydrogen bonding, and surface heterogeneity rather than chemisorption. Kinetic studies revealed rapid adsorption behaviour, with pseudo-first-order and pseudo-second-order models providing the best fit (R² up to 0.997). The Weber–Morris model confirmed that intraparticle diffusion contributed to the process but was not the sole rate-limiting step. The enhanced performance of the composite is attributed to synergistic effects between physicochemical adsorption on the porous carbon matrix and interactions with bacterial cell wall functional groups. The developed composite represents a low-cost, sustainable, and highly effective material for ibuprofen removal from contaminated water. Full article