Search Results (799)

The effects of pyrolysis temperature (400–500 °C) and time (30–90 min) on the yield and chemical and physical properties of biochar produced from almond and pistachio shells were studied using a fixed-bed pyrolyzer. Thermogravimetric analysis (TGA) was employed to characterize the kinetics of thermal degradation of the shells. This study compared the thermal behavior observed by TGA with biochar yields obtained from a fixed-bed pyrolyzer, providing insight into the agreement between laboratory-scale thermogravimetric measurements and fixed-bed pyrolysis performance. Fourier transform infrared spectroscopy (FTIR) was performed for each type of biochar. Results showed higher biochar yields from almond shells (35.0–41.3% dry basis) than from pistachio shells (26.8–36.7% dry basis). Shell type, pyrolysis temperature, pyrolysis time, and their interactions had significant effects on biochar yield. The Derivative Thermogravimetric (DTG) profiles showed distinct thermal decomposition patterns for almond and pistachio shells. Almond shells exhibited broader decomposition regions, while pistachio shells showed more distinct decomposition stages. FTIR analysis of both shell biochars indicated reduced O–H and oxygen-containing groups with increasing pyrolysis temperature and residence time, suggesting greater carbonization, aromatic enrichment, and formation of carbonaceous compounds. Greater biochar yields were obtained from the fixed-bed pyrolyzer than from TGA. A first-order kinetics model adequately described the thermal decomposition of both shell types. Apparent activation energies were 41.83–44.99 kJ mole⁻¹ for almond shells and 58.19–63.58 kJ mole⁻¹ for pistachio shells. Model validation showed a good agreement between the experimental and predicted conversion values. The results provide a basis for evaluating the potential of TGA-derived thermal behavior to inform biochar production conditions in fixed-bed pyrolysis. Full article

Slow pyrolysis of a plastic fraction isolated from municipal waste produced a char, which was then used as a precursor for the synthesis of activated carbon. The process involved thermal conversion at 800 °C and chemical activation using K₂CO₃. The resulting activated carbon was used to remove Pb(II), Cd(II), and Co(II) from aqueous solutions. Physicochemical, structural, and granulometric characterizations of the resulting adsorbent were performed. The obtained material had a specific surface area of 562 m²/g, a total pore volume of 0.328 cm³/g, and a micropore volume of 0.146 cm³/g. To determine the optimal adsorption conditions, the Box–Behnken experiment planning method was used, assuming solution pH, adsorbent mass, and initial metal ion concentration as independent variables, and the percentage removal of the contaminant as the response. Studies on sorption isotherms were conducted using a static method in a periodic system for initial metal ion concentrations ranging from 10 to 250 mg/dm³. The effect of temperature on the adsorption process was analyzed, and the kinetics sorption was investigated. Several adsorption isotherm models were used to describe the adsorption equilibrium. The maximum sorption capacity was 35.5 mg/g for Pb(II), 14.7 mg/g for Cd(II), and 11.6 mg/g for Co(II). The obtained results indicate that the plastic waste based adsorbent exhibits favorable sorption properties for the tested heavy metal ions and may be useful in water and wastewater treatment processes. Full article

The growing demand for renewable biomass energy has driven in-depth research into pyrolysis, in which particle size has emerged as a key factor influencing reaction kinetics and gas release. In this study, beech wood with four different sizes were prepared. A thermogravimetric analyzer (TGA 4000) and a Fourier transform infrared spectrometer (FTIR) were used to analyze the thermal behavior of the biomass under a high-purity N₂ atmosphere at heating rates of 10, 20, and 40 K/min. Conversion rates and activation energies were calculated from the thermogravimetric data using two model-free methods, while infrared spectroscopy was employed to analyze gas composition and release characteristics. The experimental results indicate that changes in particle size significantly affect the DTG curves: as particle size increases, the maximum rate of weight loss gradually rises. In terms of pyrolysis kinetic parameters, the activation energy of the biomass samples increased from 166.42 kJ/mol to 176.07 kJ/mol. Gas release peaks also exhibited a trend of shifting toward higher temperature regions. The primary gaseous products were classified into six functional group/gas categories, with their yields ranked in descending order as follows: CO₂ > CH₂O > CH₃OH > H₂O > CH₄ > CO. Except for CO₂, the yields of all other components increased with increasing particle size. These research findings provide data and guidance for the recovery and reuse of biomass resources, as well as for the modeling of biomass pyrolysis reactors, and the classification, pretreatment, and process optimization of biomass materials, thereby accelerating their practical application. Full article

Iron tailings, the major solid waste generated during iron ore beneficiation, possess substantial resource potential, but their utilization remains limited. Although iron tailings can adsorb Cr(VI)-containing oxyanions, their aggregation in aqueous systems restricts adsorption kinetics, resulting in only 24.4% Cr(VI) removal at an initial concentration of 30 mg/L. In this study, an economical biochar–iron tailings composite was synthesized via a one-step pyrolysis method, with biochar serving as a carbon framework to disperse iron tailings and enhance Cr(VI) removal. The composite achieved approximately 50% Cr(VI) removal at 30 mg/L, representing a significant improvement compared with raw iron tailings. In simulated acidic mine wastewater, under optimized conditions of pH 2, a dosage of 0.8 g/L, and 10 mg/L Cr(VI), the composite removed over 95% of Cr(VI) within 8 h and reached 99.95% removal after 24 h. These results demonstrate that biochar effectively alleviates iron tailings aggregation and improves adsorption performance while maintaining a relatively low treatment cost. This biochar–iron tailings composite provides a promising strategy for Cr(VI)-contaminated wastewater treatment and the high-value utilization of iron tailings. Full article

Pyrolysis is a leading route for valorizing lignocellulosic residues, yet detailed multi-step kinetic schemes have so far been deployed only in costly commercial simulators, limiting reproducibility. This work couples thermogravimetric (TGA) characterization with process simulation in the free, open-source simulator DWSIM to predict the pyrolysis product distribution of corn cob from Córdoba, Colombia. The lignocellulosic composition (hemicellulose 24.3 ± 2.9, cellulose 36.4 ± 3.0, lignin 39.3 ± 0.9 wt%) was obtained by deconvolving the derivative thermogravimetric (DTG) curve with a five-parameter asymmetric double sigmoidal (Asym2sig) function (R² > 0.9996). Pseudocomponent activation energies from the Coats–Redfern method (154.2, 124.6, and 29.9 kJ/mol) calibrated the primary reactions of a 17-reaction Ranzi scheme, extended with 18 secondary gas-phase steam reforming reactions. Validated against eight lignocellulosic biomasses, the calibrated model yielded a consolidated R² = 0.853 and average absolute deviation (AAD) = 9.8%, with char predictions most accurate (AAD = 8.9%). For corn cob, a bio-oil-optimized yield of 55.0 wt% was predicted at 500 °C, transitioning to a syngas-rich regime (51.0 wt% gas) at 750 °C. This constitutes the calibrated Ranzi-scheme implementation in DWSIM, offering an accessible, reproducible pathway for biomass pyrolysis modeling. Full article

The traditional precursor-derived ceramic (PDC) route uses micron-sized titanium sources and silicon carbide precursors to prepare Ti₃SiC₂, which limits its application in fine-scale fields. We propose a fully liquid Ti-Si-C-O precursor, consisting of tetrabutyl titanate (TBT) and liquid polycarbosilane (LPCS), inspired by the carbothermal reduction of solid oxides to prepare Ti₃SiC₂. The fully liquid precursor can offer processing advantages that are not achievable through previous PDC processes. The pyrolysis of the TSO-1 (TBT:LPCS = 3:2) undergoes four stages: dehydration condensation (RT~200 °C), alkoxy removal (200~400 °C), inorganic conversion (400~800 °C), and carbothermal reduction (>800 °C). The products of TSO-1 pyrolyzed to 1400 °C and 1600 °C are Ti₃O₅, SiO₂ and TiC, and Ti₃O₅, Ti₂O₃, SiO₂ and TiC, respectively. Increasing the LPCS content in the system can promote the formation of TiC, but will not produce Ti₃SiC₂. This phenomenon stems from the dual constraints: thermodynamically, titanium oxides outcompete SiO₂ for carbon; kinetically, the gaseous escape of effective carbon and its microscale non-uniform distribution further impair the carbothermal reduction of SiO₂. These combined factors prevent the gas–solid reaction from establishing, rendering Ti₃SiC₂ unattainable. Full article

Biochar has attracted increasing attention as a low-cost catalyst for biomass pyrolysis due to its developed pore structure, abundant surface functional groups and tunable physicochemical properties. In this study, biochars loaded with alkali and alkaline earth metal (AAEM) species were prepared by pyrolyzing cellulose impregnated with different chloride and acetate salts, including NaCl, KCl, CaCl₂, MgCl₂, CH₃COONa, CH₃COOK, (CH₃COO)₂Ca and (CH₃COO)₂Mg. The resulting AAEM-loaded biochars were subsequently employed as catalysts for cellulose pyrolysis to investigate their effects on product distribution, particularly levoglucosan (LG) and levoglucosenone (LGO) formation. SEM and XRD analyses revealed that the AAEM precursor significantly affected the morphology and phase composition of the biochars. Chloride-derived biochars retained crystalline salt phases or formed corresponding metal oxides, whereas acetate-derived biochars exhibited more dispersed metal-containing species. The introduction of AAEM-loaded biochars generally decreased bio-oil and LG yields while increasing char production, indicating enhanced secondary cracking and repolymerization reactions. Among the investigated catalysts, alkali metal-loaded biochars exhibited stronger inhibition toward LG formation than alkaline earth metal-loaded biochars. The catalytic effects followed the order of C-KCl ≈ C-NaCl > C-MgCl₂ > C-CaCl₂ for chloride-derived biochars and C-CH₃COOK ≈ C-CH₃COONa > C-(CH₃COO)₂Mg > C-(CH₃COO)₂Ca for acetate-derived biochars. Notably, C-(CH₃COO)₂Ca and C-(CH₃COO)₂Mg slightly promoted LGO formation, which was attributed to the synergistic effects of alkaline earth metal species, surface oxygen-containing functional groups and acetate-derived intermediates on dehydration reactions. Thermogravimetric and kinetic analyses further demonstrated that AAEM-loaded biochars reduced the apparent activation energy of cellulose pyrolysis and facilitated thermal decomposition. These findings provide new insights into the catalytic role of AAEM-loaded biochars and suggest a promising strategy for regulating anhydrosugar selectivity, particularly for the production of high-value LGO from biomass pyrolysis. Full article

Vacuum residue (VR) is one of the more difficult heavy fractions to process in petroleum refining, and the development of clean utilization technologies for vacuum residue has become a major research focus in the petrochemical industry. This paper discusses the compositional and structural characteristics of vacuum residue from Karamay (KVR) using methods such as ultimate analysis, FTIR, and TG-DTG. The thermal gravimetric kinetics analysis was conducted based on TG-DTG curves at different heating rates. Ultimate analysis revealed that KVR has a high H/C atomic ratio (1.84), and combined with the strong peaks at 2920 cm⁻¹ and 2850 cm⁻¹ in its infrared spectrum, it indicates that KVR is mainly composed of aliphatic compounds, with aromatic compounds being relatively few. High-temperature simulated distillation showed that KVR had a broad boiling-range distribution, with the temperature corresponding to a cumulative recovery of 86.4% exceeding 720 °C, indicating the presence of a certain proportion of ultra-high-boiling components in KVR. The Coats–Redfern kinetic model shows significant variations in activation energy (Ea) at different temperature ranges and reaction orders. Kinetic studies using non-model methods show smaller differences in Ea derived from four different non-model methods. Overall, KVR’s pyrolysis process is complex, with Ea ranging between 100 and 300 kJ/mol. Full article

Biomass-derived porous carbons are promising sustainable adsorbents for wastewater treatment. However, most reported materials require chemical activation, while the relationships between biomass precursor, pore structure, adsorption mechanism, and regeneration remain insufficiently understood. In this work, non-activated carbon materials were prepared from Juglans regia (JR) and Allium sativum (AS) biomass by pyrolysis at 400 and 900 °C and evaluated for the removal of methylene blue (MB), rhodamine B (RB), crystal violet (CV), and malachite green (MG). Carbonization at 900 °C markedly enhanced porosity, yielding a surface area of 790 m² g⁻¹ for JR900 and 177 m² g⁻¹ for AS900, together with predominantly microporous structures and negatively charged surfaces at neutral pH. The pseudo-second-order model best described adsorption kinetics, while intraparticle diffusion analysis indicated a multistep adsorption process. Equilibrium data were well fitted by both Langmuir and Freundlich isotherm models. JR900 exhibited the highest adsorption capacities for MB (321 mg g⁻¹) and RB (304 mg g⁻¹), whereas AS900 showed superior performance toward MG (278 mg g⁻¹). Stable dynamic filtration, efficient regeneration, and nearly complete dye recovery demonstrate the potential of these non-activated biomass-derived carbons for sustainable dye removal and recovery from water. Full article

Food industry wastewater containing synthetic dyes threatens ecological safety and human health. Therefore, efficient and environmentally friendly adsorbents that can remove synthetic food dyes from wastewater are urgently needed. In this work, a self-nitrogen-doped biochar (GSNBC), used for adsorption of food dyes including carmine and tartrazine, was facilely prepared by employing ginger straw waste as the carbon precursor and NaHCO₃ as a mild and relatively benign pore-forming agent via one-step pyrolysis. The as-prepared GSNBC featured well-developed porous structures, a specific surface area of 1712.52 m² g⁻¹, and rich oxygen- and nitrogen-containing functional surface groups. Particularly, GSNBC performed ultrafast adsorption, with approximately 90% of the equilibrium capacity within 1 min (600.13 mg g⁻¹ and 580.24 mg g⁻¹ for carmine and tartrazine, respectively), and reached adsorption equilibrium at about 10 min. In addition, it exhibited excellent regenerability. The adsorption kinetics and isotherms fit well with pseudo-second-order and Langmuir models. DFT calculations indicated that π–π stacking and hydrogen bonding were mainly responsible for the adsorption. This study presents not only a promising and efficient adsorbent for the remediation of dye-laden food industry wastewater but also a sustainable route for the resource utilization of ginger straw waste. Full article

This study investigated the effect of replacing N₂ with CO₂ on the pyrolysis behavior, char structure evolution, and kinetics of Fushun (FS) and Changji (CJ) oil shales. Non-isothermal thermogravimetric experiments were conducted at 5, 10, 20, and 40 °C·min⁻¹ under N₂ and CO₂ atmospheres, and the resulting chars were characterized by FTIR, XPS, BET, and SEM. Kinetic parameters were evaluated using Friedman, FWO, KAS, Starink, and Vyazovkin iso-conversional methods. Both oil shales underwent three stages: moisture release, main organic-matter pyrolysis, and high-temperature mineral decomposition. Increasing the heating rate shifted T_s and T_max to higher temperatures and intensified volatile release. At 40 °C·min⁻¹, replacing N₂ with CO₂ increased T_s from 322.6 to 399.3 °C for FS and from 368.1 to 377.3 °C for CJ, while reducing the maximum mass-loss rates to 6.81 and 8.66%·min⁻¹, respectively. N₂ favored pore development, increasing the specific surface areas of FS and CJ chars to 14.1402 and 6.1464 m²·g⁻¹, whereas CO₂ caused pore blockage in FS char and reduced its surface area to 2.7783 m²·g⁻¹. XPS showed that CO₂ promoted the formation or preservation of oxygen-containing surface carbon, especially C=O and O–C=O groups. The E_α values first decreased and then increased with conversion and were generally lower in CO₂ than in N₂. The average activation-energy differences between the two atmospheres were 23.5 and 43.2 kJ·mol⁻¹ for FS and CJ, respectively. These results provide experimental and kinetic data for modeling primary oil shale pyrolysis and subsequent char combustion and gasification under CO₂-rich conditions. Full article

Biochar (BC) is widely utilised to enhance methane production from the anaerobic digestion (AD) process due to its physicochemical properties. This study investigates the influence of biochar pretreatment on its behaviour and performance in AD systems. Pre-treated biochar derived from different feedstocks via slow pyrolysis was applied in Biochemical Methane Potential (BMP) tests at a dosage of 0.25% (w/v), and its impact on both the methane yield and digestion kinetics during cellulose degradation was evaluated. Pre-treatment was performed via steam autoclaving, serving as both a sterilisation and surface-modification step aimed at improving the physicochemical characteristics of biochar, particularly its capacity for microbial immobilisation. The results demonstrated that the effect of autoclave pretreatment on methane production was strongly feedstock-dependent. Autoclaved rice husk biochar (AC-RH550) markedly inhibited methane production, whereas autoclaved softwood biochar (AC-SW550) exhibited the best performance among all biochars tested, achieving the highest methane yield of 382.2 (mL CH₄ g⁻¹ VS), corresponding to an increase of 18.3% compared to non-pretreated SW550 and 9.2% relative to the control. This improvement is attributed to the modifications in biochar surface properties, promoting improved microbial activity and biofilm formation potentially improving direct interspecies electron transfer (DIET). Additionally, biochar may act as a buffering agent and provide adsorption sites for inhibitory intermediates such as VFA. Cell immobilisation experiments further confirmed that autoclaving enhanced biochar porosity and hydrophilicity, encouraging better colonisation and biofilm formation. Scanning electron microscopy (SEM) and microbial analyses verified increased cell attachment on pretreated biochars. Overall, these findings highlight the critical role of pretreatment in optimising biochar functionality for anaerobic digestion applications and cell immobilisation. Full article

As exploration expands into deep and unconventional petroleum systems, light oil and condensate have become key targets for reserve growth and production enhancement. This study employs the gold tube pyrolysis of kerogens from Cretaceous Qingshankou shale to investigate the role of hydrocarbon (HC) expulsion in light oil and condensate generation during thermal maturation. The results show that HC expulsion significantly reduces overall HC yields and alters their chemical composition. Specifically, compared with immature kerogen, n-hexane-extracted mature kerogen (EasyR_o = 0.96%) exhibited reductions of 60%, 57%, and 50% in C₁₅₊ compounds, C_6–14 HCs, and C_1–5 gases, respectively. Moreover, the generation window of C_6–14 HCs (a proxy for light oil) is narrowed and shifted toward lower maturity. Kinetic parameters were further used to establish two separate evolutionary models for methane, wet gas, light oil, and heavy oil. Based on these models, the shale oil resource potential of the first member of the Qingshankou Formation, the Qijia–Gulong Sag, is estimated to be (6.95–8.80) × 10⁶ ton/km² for the no-HC-expulsion scenario and (3.63–3.85) × 10⁶ ton/km² for the significant-HC-expulsion scenario (HEE = 84.35%). These results provide a valuable reference for assessing the light oil and condensate potential of high-maturity Qingshankou shale in the Songliao Basin. Full article

Algal cultivation has attracted significant attention due to CO₂ biocapture and potential for biofuel generation. Enormous generation of waste polymer often poses an environmental problem due to non-biodegradability. This study comprehensively analyses the thermal degradation characteristics of blue–green alga, Leptolyngbya subtilis JUCHE1 (LS) and waste textile polyester (WTP) and their mixtures (LS1P3 (1:3); LS1P1 (1:1); LS3P1 (3:1)) during co-pyrolysis. The interaction between LS and WTP during co-pyrolysis has been assessed through the verification of synergism using different blending ratio and through the comparison of the corresponding values of the Comprehensive Pyrolysis Index (CPI). The composite, LS1P3, exhibited the highest synergism and the maximum value of CPI. Isoconversional models (FWO, Starink, Bosewell and Tang) have been used to predict the activation energies (E_a). Thermodynamic parameters, namely, heat of reaction (ΔH), Gibbs free energy change (ΔG) and entropy change (ΔS), have also been determined for all. The average value of E_a for LS1P3 is also the lowest (96.015 kJ/mol) among all composites. The Master plot method identifies that there is a shift of reaction mechanism from phase boundary type (R2 and R3) for LS and WTP to a P2-type acceleratory reaction rate mechanism for LS1P3. The lowest average value of ΔH and the highest values of ΔG and ΔS for LS1P3 co-pyrolysis also support the least consumption of energy and the highest favorability under present conditions. The product yield distribution of co-pyrolysis in the isothermally operated conditions (450 °C) also establishes the superiority of LS1P3. Yields of pyro-oil and pyro-gas are the highest among all composites. The study ensures the future application prospects of co-pyrolysis of LS and WTP as a means for generation of energy resources (pyro-oil and pyro-gas) and chemicals (pyro-char). Full article

Biochar has attracted increasing attention for aquatic pollution control, particularly due to its capacity to accelerate the rate-limiting steps of denitrification in wastewater treatment. While early research primarily focused on the adsorption capacity of biochar, recent studies have increasingly investigated its role as a redox-active mediator that facilitates electron transfer. This review critically synthesizes the multifaceted mechanisms of biochar-enhanced denitrification, establishing a link between synthesis parameters (feedstock, pyrolysis kinetics) and physicochemical functionalities (pore architecture, redox-active functional groups). Specifically, we elucidate how precise regulation of pyrolysis temperature dictates the dominant electron transfer pathway: low-temperature biochar (<500 °C) facilitates electron shuttling via oxygen-containing functional groups (e.g., quinone moieties), whereas high-temperature biochar (>700 °C) promotes direct interspecies electron transfer (DIET) through graphitic conduction. We systematically decouple biochar-mediated electron transfer into three pathways: functional group-driven shuttling, solid-state conductive matrix transfer via conjugated π-electrons, and material-assisted DIET. Crucially, we emphasize that validating true DIET requires direct biological evidence of electroactive machinery. Furthermore, the review details how biochar modulates the biological microenvironment, upregulating key denitrification genes (narG, nirS/K, nosZ) and enriching functional microbial consortia. By integrating advances in surface modification—such as heteroatom doping and metal loading—we propose strategies to engineer biochar for optimized nitrate-to-nitrogen conversion. Future perspectives underscore the need for balancing electron-donating capacity with structural stability, developing low-energy functionalization techniques, and conducting life-cycle assessments to facilitate the scale-up of sustainable, high-efficiency nitrogen removal systems. Full article