Pretreatment Process Research Articles

Boosting 2G bioethanol production by overexpressing dehydrogenase genes in Klebsiella sp. SWET4adh1+adhE: ANN optimization, scale-up, and economic sustainability

The most significant obstacle in the production of 2G bioethanol lies in transforming the complex carbohydrates found in plant biomass into simpler, fermentable sugars. However, this challenge can be effectively addressed by developing highly efficient lignocellulolytic ethanologenic strains. The current study intended to improve the ethanol productivity of efficient cellulose and hemicellulose metabolizing Klebsiella sp. SWET4 by overexpressing its native ethanologenic genes (adh1, adhE, and nifJ). Among the recombinants, SWET4adh1+adhE exhibited the highest ethanol productivity from banana peel (BP) in facultative anaerobic conditions with a 7.76-fold increase compared to the native strain. Transcript level expression study using qPCR indicated 106.15- and 22.78-fold higher expression of adh1 and adhE gene, respectively at 56 h from BP, whereas, 4.80- and 2.08-fold higher concentrations of respective proteins were obtained after 24 h. ANN and GA-mediated optimization further enhanced biomass and ethanol production to 2.33 and 24.47 g/L, respectively. Hence the ethanol productivity by SWET4adh1+adhE was enhanced by 19.89-fold. The bioreactor kinetic study exhibited diauxic growth of SWET4adh1+adhE and achieved an impressive ethanol yield of 0.44 g/g of carbohydrates, surpassing many 2G bioethanol processes. Despite of single-product scheme, a minimum selling price of $2/kg of distillate was found to make the process economically feasible. The breakeven point of the process was found to be 30% of its total capacity. Techno-economic analysis underscores the feasibility and economic advantages of the current study eliminating the pretreatment steps, and highlighting the process’s innovation and viability in 2G bioethanol production. Elimination of the pretreatment process not only achieved economic sustainability but also significantly enhanced the renewability of bioethanol production endorsing direct biomass conversion to bioethanol.

Enhancing resource recovery from acid whey through chitosan-based pretreatment and machine learning optimization

Acid whey, a dairy byproduct with low pH and high organic content, presents disposal challenges but also potential for resource recovery. In this study, chitosan gel was synthesized and evaluated for turbidity reduction of acid whey. Machine learning (ML) models were employed to predict and optimize the pretreatment process, with the Random Forest algorithm achieving a prediction accuracy of 0.78. Using the Simulated Annealing algorithm, optimal conditions were identified, applying a 2.2 % chitosan solution gel at a dosage of 24 g/L to acid whey at pH 4.6 for 12 h, achieving a 91 % turbidity reduction, a significant improvement over the 71 % obtained prior to optimization. Validation experiments confirmed its effectiveness in predicting and optimizing the pretreatment process. These findings highlight the feasibility of ML in optimizing chitosan pretreatment and demonstrate chitosan gel as a cost-effective, efficient option for acid whey, with potential to enhance resource recovery in the dairy industry.

Rapid Detection of Soil Available Phosphorus using Capacitively Coupled Contactless Conductivity Detection

Background: In China, the traditional method for analyzing soil available phospho-rus is inadequate for large-scale soil assessment and nationwide soil formulation demands. To address this, we propose a rapid and reliable method for soil-available phosphorus detection. The setup includes an on-site rapid pre-treatment device, a non-contact conductivity detection device, and a capillary electrophoresis buffer solution system composed of glacial acetic acid and hydroxypropyl-β-cyclodextrin. Methods: The on-site rapid pre-treatment process includes fresh soil moisture content detec-tion (moisture rapid detector), weighing (handheld weighing meter), stirring (handheld rapid stirrer), and filtration (soil rapid filter) to obtain the liquid sample, and direct injection (capil-lary electrophoresis detector). The phosphate ion detection parameters include capillary size, separation voltage, injection parameters, and electric injection. We used Liaoning brown soil, Henan yellow tidal soil, Heilongjiang black soil, and Anhui tidal soil as standard samples. Additionally, we used mathematical modeling methods and machine learning algorithms to analyze and process research data. Results and Conclusion: Following calibration with standard samples, the experimental blind test samples demonstrated conformity with the national standard method, exhibiting a relative standard deviation of less than 3%. The proposed pre-treatment device and non-contact con-ductivity detector are powered by lithium-ion batteries, rendering them ideal for extended field operations. The non-contact conductivity detector obviates the need for direct contact with test samples, mitigating environmental pollution. Furthermore, the neural network model exhibited the highest level of goodness of fit in chemical data analysis.

Synthesis and Application of LTA Zeolite for the Removal of Inorganic and Organic Hazardous Substances from Water: A Review

Industrialization and human activities have caused significant environmental challenges, with water pollution posing severe risks to human health. This underscores the urgent need for effective water treatment solutions. Zeolites, known for their high specific surface area and stability, have gained increasing attention as adsorbents for water treatment. Among zeolites, LTA varieties stand out due to their low Si/Al ratio, which enhances ion-exchange capacity, and their cost-effectiveness. This review focuses on the synthesis of low-silica LTA zeolites, particularly zeolite A, using natural materials and solid wastes without relying on organic-structure-directing agents (OSDAs). Common pretreatment processes for such synthesis are also highlighted. The review further explores the applications of LTA zeolites in water treatment, emphasizing their exceptional performance in adsorbing inorganic and organic pollutants. In particular, LTA zeolites are highly effective at removing inorganic cation pollutants through ion exchange. An updated ion-exchange selectivity order, based on previous studies, is provided to support these findings. Overall, this review aims to guide future research and development in water treatment technologies.

Impurity Impacts of Recycling NMC Cathodes

AbstractThe skyrocketing demands for electric vehicles cause large quantities of spent lithium‐ion batteries (LIBs) and pressure on the global supply chain, leading to raw materials shortages and cost increases. In LIBs, LiNixMnyCozO2(NMC) cathodes are one of the major cathode materials. Thus, recycling NMC cathodes from spent lithium‐ion batteries is emerging because they contain abundant valuable materials, which can be considered unique “mineral” sources. Impurities are one of the main concerns for introducing recovered materials back into new battery manufacture because impurities are typically considered to impair the properties of recovered materials. However, some impurities can beneficially act as dopants or coatings. To comprehensively understand the effects of different impurities and treat impurities properly, this review summarizes the origin and species of possible impurities which can be introduced during different pretreatment processes, analyzes the methods to remove impurities, and discusses the effects of impurities on the regeneration process and recovered materials. This work also outlines future perspectives for fundamental research about impurities and relevant challenges of the recycling industry, helps academia and manufacturers to create new impurity standards of recovered cathode materials, and suggests opportunities for achieving a circular economy for the lithium‐ion batteries industry.

Using Polyvinyl Chloride and Screen-Printed Electrodes for the Determination of Levofloxacin in the Presence of Its Main Photo-Degradants in River Water: A Comparative Study

The application of membrane sensors for the detection and quantification of pharmaceutical environmental contaminants has become a significant goal in recent years. Due to the widespread application of levofloxacin hemihydrate (LEVO) in medicine, its occurrence in the environment, especially in surface water bodies like rivers, is quite likely. Extended exposure of river water to sunlight and the photo-degradability of LEVO may facilitate its photo-degradation. To measure LEVO in the presence of its principal photo-degradants, two sensitive and selective membrane electrodes were designed. A polyvinyl chloride electrode (PVCE) and a screen-printed electrode (SPE) were constructed for the selective analysis of the investigated drug. Phosphomolybdic acid was used to prepare a lipophilic ion pair with the studied drug. All test parameters were optimized to achieve the best electrochemical performance. The electrodes demonstrated a linear range from 1 × 10−6 M to 1 × 10−2 M. The PVCE and SPE demonstrated slopes of 55.80 ± 0.70 mV/decade and 56.90 ± 0.50 mV/decade, respectively. The aforementioned sensors demonstrated satisfactory performance within a pH range of 3.0 to 5.0. The fabricated sensors were successfully utilized to accurately quantify LEVO in the presence of its primary photo-degradants. The membranes were effectively utilized to measure LEVO in river water samples without requiring pre-treatment processes.

Membrane Foulant Removal by Ozone-Biocarrier Pretreatment Technology for Industrial Wastewater Reclamation

During wastewater reclamation, organic matter is considered the dominant foulant that shortens the lifetime of ultrafiltration (UF) membranes during operation. Additionally, the mineralization efficiency of organic matter in secondary effluent is typically low due to nonbiodegradable carbon sources. Herein, a combination of ozone and a porous biocarrier reactor was applied as a novel pretreatment system to enhance organic matter removal in the effluent in a lab-scale evaluation and pilot test. The results indicated that 70% of the biopolymer was removed, and the chemical oxygen demand (COD) removal efficiency was 1.8 times higher in this combined process than in the process with a porous biocarrier alone. The UF flux increased by 16% after the combined ozonation and porous biocarrier pretreatment process compared with the process with no pretreatment. Interestingly, the genus Flavobacterium (15.59%), containing biopolymer-degrading bacteria, was observed only in the combined ozone plus porous biocarrier process. Moreover, the results show that biopolymers can be removed through the combined ozone and porous biocarrier process due to partial ozone degradation, confirming that this combined process is one of the better pretreatment procedures for organic matter removal and improves the flux of UF during the wastewater reclamation process.

Construction of energy consumption monitoring system for energy saving equipment in seawater desalination based on whale algorithm

ABSTRACT Seawater desalination has emerged as a pivotal solution to address freshwater scarcity in coastal regions, with China being a prominent adopter of this technology. This paper compares three large-scale seawater desalination projects in China: the Six Heng Water Treatment Plant, the Caofeidian Desalination Project, and the Huaihai Yu Huan Power Plant Desalination Project. Each project employs distinct desalination technologies, including reverse osmosis and dual-membrane processes. We evaluate these systems’ operational parameters, performance indicators, and cost-effectiveness over their operational lifespans. Key considerations include seawater intake, pretreatment processes, reverse osmosis desalination, energy recovery systems, and post-treatment mineralisation. The analysis highlights these desalination plants’ efficiency, sustainability, and economic viability in addressing freshwater demands in their respective regions. Insights from this comparative study contribute to optimising seawater desalination processes, enhancing water resource management, and guiding future infrastructure development efforts in coastal areas.

Enhancement of Photocatalytic Activity in BiFeO3 Nanoparticles through Electrical Polarization

This study investigates the enhancement of photocatalytic properties in BiFeO3 nanoparticles through an additional electrical polarization (poling) pretreatment process. BiFeO3, a promising multiferroic material with a narrow bandgap of ≈2. 12 eV, is well‐suited forvisible light‐driven photocatalysis. However, its photocatalytic efficiency isoften limited by insufficient photogenerated charge availability. To address this, a poling process was employed to align the ferroelectric domains within BiFeO3 nanoparticles, improving charge separation and enhancing photocatalytic activity. The findings reveal that the poling process preserves the intrinsic bandgap of BiFeO3, maintaining its visible light absorption capability. Steady‐state photoluminescence spectroscopy shows a marked increase in the intensity in poling‐treated samples, indicating enhanced charge carrier generation. Photo degradation experiments using Indigo dye as a model pollutant demonstrate that poling‐treated BiFeO3 achieves a remarkable photodegradation efficiency of 99%, compared to 56% for untreated BiFeO3. Additionally, the poling‐treated BiFeO3 retains 65% of its initial efficiency after four cycles, highlighting its durability for sustained environmental applications. This study underscores the effectiveness of poling in enhancing the photocatalytic performance of BiFeO3 nanoparticles, providing valuable insights into the development of efficient photocatalysts via domain engineering for environmental purification technologies.

The Effect of Alkaline Pretreatment of Spent Malting Grains for Biogas Production, Mathematical Modeling and Process Optimization

Spent grains from brewing industries are considered a suitable source for biogas production due to their high accessibility and affordability. However, lignocellulosic material, due to its fiber content (cellulose, hemicellulose, and lignin), meets implementation issues in the anaerobic digestion process. To enhance the efficiency of anaerobic digestion of brewery spent grain, an alkaline treatment was performed using sodium hydroxide (NaOH). The parameters of alkaline treatment were temperature (T) and soda-spent grain ratio (S/D). The characterization of the raw spent grains indicates that the organic matter (OM), total organic carbon (TOC), nitrogen (N), protein (P), N/C ratio, and pH were 99%, 57.39%, 3%, 18.75%, 19.13%, and 5.6, respectively. The respective contents of hemicellulose, cellulose, and lignin were 33.3%, 30.4%, and 6.5%. The pre-treatment process yielded a 5% reduction in hemicellulose and a 43% reduction in cellulose while increasing the volume of biogas produced from 0 to 577 mL. After pre-treatment, two biodigesters produced volumes of 23.03 mL/per day (100 °C with a soda/spent grain ratio of 0.01%) and 22 mL/per day (28 °C with a soda/spent grain ratio of 0.05%). The mathematical model showed an interaction between temperature and S/D ratio. The predictive modeling analysis presented that the maximum volume of biogas can be obtained as 23.3 mL/per day after pre-treatment of spent grains at 100 °C with a NaOH/spent grain ratio of 0.01.

Surface state study of the pre-treatment process for electroless plated aluminum alloys for EP mandrels

Surface state study of the pre-treatment process for electroless plated aluminum alloys for EP mandrels

Ecofriendly and biocompatible biochars derived from waste-branches for direct and efficient solid-phase extraction of benzodiazepines in crude urine sample prior to LC-MS/MS.

Biochars (BCs) derived from waste-branches of apple tree, grape tree, and oak were developed for direct solid-phase extraction (SPE) of five benzodiazepines (BZDs) in crude urine samples prior to liquid chromatography-tandem mass spectrometry (LC-MS/MS)determination. Scanning electron microscopy, elemental analyzer, X-ray diffractometry, N2 adsorption/desorption experiments, and Fourier transform infrared spectrometry characterizations revealed the existence of their mesoporous structure and numerous oxygen-containing functional groups. The obtained BCs not only possessed high affinity towards BZDs via π-π and hydrogen bond interactions, but also afforded the great biocompatibility of excluding interfering components from undiluted urine samples when using SPE adsorbents. Variables affecting SPE of target analytes were systematically optimized including pH, ionic strength, dilution ratio, washing solution, desorption solvent, and its volume. The method of BC-based SPE combined with LC-MS/MS exhibited awide linear range of 0.03-100ng/mL, alow detection limit of 0.01-0.08ng/mL, and satisfactory recovery of 77.6-106% for the studied BZDs. Notably, this method allowed the possibility of direct loading of undiluted urine samples and avoided tedious filtration and dilution steps, which significantly simplified the pretreatment process. Additionally, these BC sorbents derived from waste-branches were ecofriendly and cost-effective, providing a sustainable alternative for the traditional SPE sorbents. Thus, the proposed method has promising application for ecofriendly, simple, efficient, and reliable monitoring of BZDs in urine samples.

Design and fabrication of superhydrophobic microstructured grooved substrates to suppress the coffee-ring effect and enhance the stability of Sr element detection in liquids using LIBS.

A new technique has been developed to enhance the stability of laser-induced breakdown spectroscopy (LIBS) in the analysis of dry droplets by mitigating the coffee ring effect (CRE) on substrates with superhydrophobic microstructured grooves. The substrate was prepared from a laser-etched pure copper base, resembling the surface of a lotus leaf, creating a biomimetic superhydrophobic substrate. The superhydrophobic microstructured grooved substrate contained an array of dome-shaped cones with heights of approximately 140 μm and 100 μm, arranged in a periodic pattern of high-low-high. The superhydrophobic properties of the substrate not only evaporation-induced thermal capillary action but also initiated the Marangoni flow, which moves from the periphery to the center of the droplet as it evaporates. This flow mechanism effectively mitigated the CRE by transporting the analyte from the bottom edge of the droplet across its surface to the central peak. To assess how these superhydrophobic microstructured grooved substrates impede the formation of coffee rings, LIBS was deployed to analyze samples from both structured and unstructured grooved substrates. The results indicated that the relative standard deviation (RSD) of the spectral intensity for Sr I at 407.67 nm in substrates with a superhydrophobic microstructured groove edge length of 0.8 mm was 3.6%. In contrast, for the unstructured grooved substrate and a side length of 0.9 mm, the RSD was significantly higher at 25.4%. This research demonstrates that substrates with superhydrophobic microstructured grooves are capable of effectively mitigating the CRE. Additionally, the study examined how the dimensions of these grooves impact the plasma characteristics across two distinct configurations. Based on these observations, calibration curves for Sr were developed using substrates with groove side lengths of 0.6 mm and 0.8 mm. The performance of the superhydrophobic microstructured grooved substrate was satisfactory, exhibiting determination coefficients (R2) of 0.994 and 0.995 for the Sr element. The detection limits (LOD) were notably low at 0.16 μg mL-1 and 0.11 μg mL-1. The average relative standard deviations (ARSD) were 7.2% and 4.9%, respectively. These results demonstrate that the superhydrophobic microstructured grooved substrate effectively mitigates the CRE, thereby enhancing the detection sensitivity and prediction accuracy for heavy metals. This provides a robust reference for selecting platforms using LIBS technology in the pre-treatment process.

Complicated pollution characteristics (particulate matter, heavy metals, microplastics, VOCs) of spent lithium-ion battery recycling at an industrial level.

The recycling of spent lithium-ion batteries has become a common concern of the whole society, with a large number of studies on recycling management and recycling technology, but there is relatively little study on the pollution release during the recycling process. Pollution will restrict the healthy development of the recycling industry, which makes relevant research very significant. This paper monitored and analyzed the battery recycling pretreatment process in a formal factory, and studied the pollution characteristics of particulate matter, heavy metals, and microplastics under different treatment stages. In addition, the release characteristics of VOCs during pyrolysis were also studied. When the green pretreatment process was used, PM10 concentration in most processing units was below 100μg/m3, indicating that the overall pollution prevention and control effect in the workshop is well-done. Particulate matter in workshop contained a large amount of metal components, mainly Fe, Cu, Co, Mn, Ni, etc. Microplastics were widely distributed in ground dust, and small-size microplastics are suspended in the air for a long time because of Brownian motion. Collecting ground dust and particulate matters is beneficial for controlling the emission of microplastics. During thermal treatment, Ethylene carbonate and dimethyl carbonate in the electrolyte would enter the atmosphere, and a large amount of short chain hydrocarbons released together, forming VOCs pollution. This study summarized distribution characteristics of different pollutants in a battery recycling factory. The basic pollution data provided are beneficial for improving the recycling technology of spent lithium-ion battery.

Recovery of iron as hematite and separation of trivalent lanthanide ions from spent hard disk magnet leach liquor using [P66614][Cy272] ionic liquid.

The widespread use of neodymium-iron-boron (NdFeB) magnets has raised concerns about the environmental impact of their disposal, prompting the need for sustainable recycling strategies. Traditional solvents used in recycling are toxic and flammable, making them risky to use. Ionic liquids are safer and greener options with low vapor pressure, high stability, and less flammability. This study introduces an eco-friendly recycling approach utilizing the [P66614][Cy272] ionic liquid to selectively extract iron and recover rare earth elements (REEs) from the leach liquor of waste NdFeB magnets. Pre-treatment processes enhanced metal concentration before leaching, including demagnetization, grinding, and screening. Optimal leaching conditions: 2 mol L-1 HCl, 80 °C, 10 g L-1 pulp density, and 90 minutes, resulted in complete leaching of REEs (Dy, Pr, Nd), iron, and boron. Using 0.01 mol L-1 [P66614][Cy272] ionic liquid, 100% of the iron was removed from the leach liquor with minimal co-extraction of REEs (∼4%). Precipitation of iron leading to Fe2O3 (hematite) after calcination and is verified through XRD and SEM-EDS analyses. The ionic liquid also enabled 81.1% recovery of HCl from the leach liquor, reducing neutralization needs and operational costs. Subsequent REEs separation using 0.01 mol L-1 [P66614][Cy272] ionic liquid demonstrated high selectivity, achieving separation factors of 18.55 (Dy/Pr) and 15.52 (Dy/Nd) at pH 2.03. Dy(iii) was successfully separated from NdFeB leach solutions using counter-current extraction, leaving 6.0 mg L-1 in the raffinate, requiring two extraction stages at a 2 : 3 organic-to-aqueous phase (O/A) ratio. The reusability of the ionic liquid further enabled a sustainable, closed-loop recycling process. This approach highlights the potential for integrating ionic liquids into green technologies for NdFeB magnet recycling, ensuring resource recovery while minimizing environmental impact.

The effects of leaching and pyrolysis on particle synthesis and their impact on thermal conductivity and cooling rates of waste PCB-dispersed quenchants

Abstract This study investigates the effects of pre-treatment processes—leaching and pyrolysis—on synthesizing particle-dispersed quenchants derived from waste printed circuit boards (PCBs) for enhanced heat treatment applications. The process begins with milling PCB powder with and without pre-treatment, followed by thermal conductivity and cooling rate analysis of synthesized quenchants. Findings reveal that full pre-treated particles, which undergo leaching and pyrolysis, achieve significantly smaller sizes, up to 80.4%, compared with the half-pre-treated particles. The better improvement was due to the breakdown of epoxy resin used in the PCB. The particle size reduction enhances the quenchant's thermal conductivity up to 17.47% for the quenchant with 0.5% dispersed particle. Similarly, the maximum cooling rate was improved by 16.93% for the same quenchant. Quenching tests on S45C medium carbon steel demonstrate that particle-dispersed quenchants increase the hardness of the quenched steel, maximized at 57.8 HRC, because of the higher density of the Martensite phase developed by the higher cooling rate. This research highlights the value of pre-treatment in optimizing quenchant performance, with potential implications for improved efficiency in industrial heat treatments.

A novel sulfuric acid pretreatment process for the efficient flotation separation of copper and lead: the key role of atmosphere and pressure

A novel sulfuric acid pretreatment process for the efficient flotation separation of copper and lead: the key role of atmosphere and pressure

Adding colour to ion-selective membranes.

An idea of using ion-exchanger salt containing optically active cations to prepare ion-selective membranes is proposed. Although the presence of an ion-exchanger in the composition of neutral ionophore based sensors is necessary, the choice of available salts for cation-selective sensors preparation, is usually limited to sodium or potassium compounds. In this work we propose application of an alternative salt, using a cation optically active both in absorption and emission mode as a mobile one. Thus, coloured ion-selective membranes can be obtained. This in turn opens new possibilities of monitoring the state of the receptor layer as well as allows direct analytical application of ion-selective membranes in simple optical mode with all benefits related to eliminating the necessity of using reference electrodes. As a model system Nile blue derivative of tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ion-exchanger was prepared and used to obtain potassium or calcium selective sensors. Selective exchange of ions between the membrane and solution, leading to an increase in optical signal of the solution, can be used to quantify the presence of analyte ions. Thus the sensor pretreatment process is becoming a source of analytical information. The applicability of this approach was verified in determining the presence of potassium ions in the vast majority of interfering ions, e.g. present as impurities in the reagent grade calcium chloride. The resulting potassium ions contents was well comparable with values obtained in course of ICP-MS approach.

Recycling of acid-pretreatment hydrolyzates of rice straw for high bioethanol production by S. cerevisiae and P. stipitis fermentation

ABSTRACT The current study developed a strategy to recycle the acid-pretreated hydrolyzate for multiple pretreatments of rice straw to increase the soluble sugar content in the medium, thereby enhancing bioethanol conversion. This process recovered a maximum glucose concentration of 10.4 g/L and xylose: 44.5 g/L in the recycled acid-pretreated rice straw hydrolyzate obtained after the third pretreatment. This resulted in a 2.4-fold increase in glucose recovery and a 2.3-fold increase in xylose recovery compared to the initial pretreatment process. For both glucose and xylose conversion strategies, a co-culture of hexose fermenting S. cerevisiae and P. stipitis, capable of fermenting both pentose and hexoses was employed. The maximum bioethanol titer achieved from the co-culture of S. cerevisiae and P. stipitis was 11.29 g/L. However, applying a sequential culture approach of S. cerevisiae followed by P. stipitis with an intermediate heat inactivation at 50°C resulted in an improvement of bioethanol titer to 12.39 g/L with productivity of 0.258 g/L/h. This led to an improvement in 2.9-fold and 1.2-fold bioethanol titer in comparison to sole fermentation by S. cerevisiae and P. stipitis, respectively. The reuse of acid pretreated hydrolyzate for high recovery of soluble sugar and subsequent fermentation by sequential culture strategy can maximize lignocellulosic bioethanol production.

Effects of particle size and pretreatment methods on the morphometry of grass charcoal particles: Implications for morphometric analysis of microcharcoal particles

The morphometry of sedimentary charcoal particles illuminates the source fuel types. This study explores the variation in morphometry (specifically, the length-to-width (L/W) ratio) of charcoal particles of different sizes, using charcoal collected from Miscanthus sinensis (Japanese pampas grass) fields following controlled burning. We also investigated the impact of pretreatment processes on sedimentary microcharcoals. The results indicate a general decrease in the L/W ratio with decreasing particle size, with the microcharcoal exhibiting a substantial decrease. The mean L/W ratios for size categories of 250 µm–1 mm, 125–250 µm, 63–125 µm, and <63 μm in size are 6.42, 5.54, 4.94, and 3.45, respectively. Furthermore, pretreatment processes for microcharcoal decrease the L/W ratio. Consequently, the L/W ratio of grass microcharcoal (<125 μm) likely falls within 50–80% of the ratios observed in grass macrocharcoal (>125 μm), necessitating caution in interpreting microcharcoal data. Our findings emphasize the importance of considering particle size and pretreatment effects when interpreting paleofire records and highlight the need for further research to establish robust cutoff values for fuel type inference based on charcoal morphometry, particularly for microcharcoal.