Solid Phase Research Articles

Preparation and characterization of cementitious materials from dedioxinized and dechlorinated municipal solid waste incineration fly ash and blast furnace slag

To address the resource utilization issue of MSWI fly ash, a method has been proposed to prepare cementitious materials using harmlessly processed MSWI fly ash (HPFA). After washing and thermal treatment, The physicochemical properties of HPFA were characterized using QXRD, ICP, XRF, and GC-MS. Cementitious materials were prepared using HPFA, gypsum and blast furnace slag (BFS) as raw materials, Through XRD, TG, FTIR, TEM, and SEM-EDS methods, the hydration and hardening characteristics were investigated, and the leaching of heavy metals from solidified materials in simulated surface water and landfill environments was evaluated using ICP-MS. The results indicate that the harmless treatment can effectively reduce the chloride content and dioxins in MSWI FA but still contains heavy metals. The addition of HPFA (10%-50%) can enhance the compressive strength of cementitious materials, accelerate the exothermic process of cement hydration, and increase the total heat release of hydration, implying an improvement in the degree of hydration of the system.HPFA could effectively promote the hydration of gypsum and BFS, resulting in the higher formation of ettringite and C-(A)-S-H（C/S=1，Al/Si=0.3）.The formation of C(Mg/Fe)-(A)-S-H suggests that the Fe-Mg solid solution phase in HPFA may have participated in the hydration reaction. The increased stability of highly cross-linked (Q4) silicate tetrahedral structure with time implies that the material may have good durability. The leaching amount of heavy metals met the standards of Class I surface water in GB3838–2002 and GB5085.3–2007 which implies that the material has environmental safety. This study innovatively provides a preparation path for harmless MSWI fly ash and cementitious material ratios, reveals the hydration mechanism of HPFA in cementitious materials, evaluates the solidification ability of heavy metals, and provides important ideas for the resource utilization of MSWI fly ash.

Revealing the microbial diversity and volatile flavor formation in finger citron kombucha by metagenomic and GC-MS analysis

Kombucha is a kind of health drink formed by the metabolism of Symbiotic Culture of Bacteria and Yeast (SCOBY) composed of yeast, acetic acid bacteria and lactic acid bacteria, which is popular among researchers and fond of consumers because of its antioxidant and hypoglycemic effects. In this study, the finger citron kombucha with different fermentation time (2, 4, 6, 8 day) were analyzed by headspace solid phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and metagenomic sequencing. The results showed that a total of 76 volatiles were identified, including 15 key volatiles, such as linalool, geraniol, α-terpinene, and limonene, which had a great influence on the flavor of kombucha. Metagenomic analysis showed that unclassified-g-Gluconobacter, Komagataeibacter saccharivorans, Gluconobacter-sp.-R71656 and other microorganisms were the dominant species in finger citron kombucha. Through the correlation heat map analysis of volatiles and microbial composition, it was found that Gluconobacter had a positive effect on the formation of most volatiles of kombucha. In addition, Novacetimonas hansenii, Brettanomyces bruxellensis and Wickerhamiella sorbophila were also closely related to the flavor formation of kombucha. This study provided a theoretical basis for finding the key aroma-producing microorganisms in the fermentation process of finger citron kombucha and the subsequent construction of SCOBY.

Biochar-derived dissolved organic matter enhanced the release of residual ciprofloxacin from the soil solid phase

Biochar has been utilized to reduce ciprofloxacin (CIP) residues in soil. However, little is known about the effect of biochar-derived dissolved organic matter (DOM) on residual CIP transformation. Thus, we analyzed the residual soil CIP as influenced by biochar generated from rice straw (RS3 and RS6), pig manure (PM3 and PM6), and cockroach shell (CS3 and CS6) at 300 °C and 600 °C. The three-dimensional excitation-emission matrix (3D-EEM), parallel factor analysis (PARAFAC) and two-dimensional correlation spectral analysis (2D-COS) were used to describe the potential variation in the DOM-CIP interaction. Compared with CK, biochar amendment increased the water-soluble CIP content by 160.7% (RS3), 55.2% (RS6), 534.1% (PM3), 277.5% (PM6), 1160.6% (CS3) and 703.9% (CS6), indicating that the biochar feedstock controlled the soil CIP release. The content of water-soluble CIP was positively correlated with the content of dissolved organic carbon (r = 0.922, p < 0.01) and dissolved organic nitrogen (r = 0.898, p < 0.01), suggesting that the major influence of the water-soluble CIP increase was DOM. The fluorescence quenching experiment showed that the interaction between DOM and CIP triggered static quenching and the creation of a DOM complex. The mean log K of protein-like material (4.977) was higher than that of terrestrial humus-like material (3.491), suggesting that the protein-like material complexed CIP was more stable than the humus-like material. Compared with pyrolysis at 300 °C, pyrolysis at 600 °C decreased the stability of the complex of protein-like material and CIP by 0.44 (RS), 1.689 (PM) and 0.548 (CS). This result suggested that the influence of temperature change was more profound on PM biochar-derived DOM than on RS and CS. These insights are essential for understanding CIP transportation in soil and controlling CIP contamination with biochar.

The hydrological response of melting ephemeral snowpacks compared to winter rainfall events in a mid-mountainous Pyrenean catchment

AbstractThe hydrological role of ephemeral snowpacks and their differences in stormflow and sediment transport characteristics compared to events triggered by winter rainfall conditions have received limited attention. This study aims to analyze the hydrological and sediment transport responses to rain-on-snow (ROS), melt, mixed, and rainfall events in the Araguás Catchment, situated in a mid-mountain site of the Central Spanish Pyrenees, with a climate strongly influenced by Mediterranean conditions. This catchment represents the transition from a winter ephemeral snow environment to a fully rainfall-dominated site. Results indicate that snowmelt has a modest yet measurable impact on the annual water balance, averaging 10% and rising to 30% during winter (December to February). ROS and melt events consistently exhibited higher mean and maximum discharge and elevated stormflow coefficients compared to mixed and rainfall events. The lowest water infiltration into the soil was observed during melt events, attributed to the potential for frequent freezing soils, specific poor edaphic conditions, and the rapid snowmelt in the area. Consequently, melting events displayed the shortest flood hydrographs among the four analyzed events. The study also underscores precipitation’s almost negligible erodibility capacity in the solid phase and emphasizes the protective role of snow cover in preventing soil erosion. It is important to note that the presented results are significantly influenced by the physiographic, lithological, and edaphic characteristics of the Araguás Catchment. This highlights the importance of conducting more detailed analyses of ephemeral snowpacks in experimental sites under a broader range of environmental conditions for a comprehensive understanding.

Numerical analysis of a protective coating for mining industry feed chute

The selection of materials for the protective coating of a crusher’s feed chute significantly influences the mean time between failures (MTBF) and operational costs associated with the mass production of sulfuric acid at MMG/Kinsevere. Neglecting the condition of the protective coating can pose a serious challenge to production efficiency and result in increased downtime. This study focuses on enhancing industrial productivity in Sulfuric Acid production with minimal maintenance. The investigation explores the quality and type of materials used for the protective coating of the feed chute in the mining industry, particularly at MMG/Kinsevere, utilizing Ansys Fluent and SOLIDWORKS Software for analysis. The paper proposes a Ceramic protective liner for the crusher feed chute due to its superior resistance to erosion compared to other liners. Different feed chute models, constructed with materials like halogenated butyl rubber, 316 stainless steel, and ceramic, underwent analysis. The evaluation of the potential impact on the mean time between failures (MTBF) for different materials used in a protective coating, considering the rate of erosion through computational fluid dynamics (CFD) with ANSYS FLUENT software, is a central aspect of this study. The detailed modeling and simulation reveal that the ceramic material exhibits the most favorable protective coating characteristics, with an erosion rate density of 06.636753 kg/m2s, outperforming halogenated butyl rubber (3.326576 kg/m2s) and 316 stainless steel (2.186633 kg/m2s). The simulation yielded results corresponding to flow rates of 284.19 kg/s for the solid phase and 123.14 kg/s for the liquid phase.

Determination of Azole Fungicide Residues in Fresh Juice by Magnetic Solid Phase Extraction Based on Fe3O4@ZnAl-LDH@MIL-53(Al) Sorbent in Combination with High-Performance Liquid Chromatograph.

In this work, a magnetic adsorption material based on metal-organic framework (Fe3O4@ZnAl-LDH@MIL-53(Al)) was synthesized and used as an adsorbent in the process of magnetic solid phase extraction. Then, a high-performance liquid chromatograph was used to quantitatively detect triazole fungicides in samples. In order to verify the successful preparation of the material, a series of characterization analyses were carried out. Besides, the key parameters that may affect the extraction efficiency have been optimized, and under optimal conditions the three triazole fungicides showed good linearity in the range of 10-1000μg/L (R2 ≥ 0.9796); Limit of detections were ranged from 0.013 to 0.030μg/mL. Finally, the established method was applied to the detection of triazole fungicides in four fresh juice samples. The results showed that the target analyte was not detected in all the test samples. By detecting the recoveries (73.3-104.3%) and coefficient variation (RSD ≤ 6.8%) of triazole fungicides in fortified samples, it proved that this established method meets the requirements of pesticide residue analysis and showed excellent application potential.

Effect of Fluorine and Phosphorus Impurities in Phosphogypsum on Microstructure and Mechanism of α‐Type Hemihydrate Gypsum Crystals

AbstractIn this study, phosphogypsum (PG) is simulated by doping fluorine and phosphorus ions in an analytically pure reagent of gypsum dihydrate. The influence of fluorine and phosphorus impurity and content on the dehydration reaction process of phosphogypsum and its crystalline micromorphology is assessed during the preparation of α‐type gypsum hemihydrate in the reversed‐phase microemulsion system and its mechanism. The results show that when the fluorine content increases from 0 to 1.0 mol L−1 (ωNaF = 1.0 mol L−1), the dehydration process of dihydrate gypsum will be greatly slowed down. Scanning electron microscopy (SEM) analysis showed that even a small amount of F− (ωNaF = 0.2 mol L−1) can significantly inhibit the formation of α‐type hemi‐hydrated gypsum. When ωH3PO4 = 0.10 mol L−1, the water of crystallization content in the solid phase of the sample decreased to 5.24% after 90 min, which is significantly lower than during the same period of the benchmark group. However, there is a threshold value for the effect of phosphorus on the microscopic morphology of the α‐type gypsum hemihydrate crystals, when ωH3PO4 ≤ 0.04 mol L−1, the crystal morphology is basically unaffected. Moreover, when ωH3PO4 continued to increase, the defects on the crystal surface increased.

A Comprehensive Parametric CFD Investigation on Packed Bed Thermal Energy Storage System with Encapsulated Solid–Solid Phase Change Materials in Discharging Mode

A Comprehensive Parametric CFD Investigation on Packed Bed Thermal Energy Storage System with Encapsulated Solid–Solid Phase Change Materials in Discharging Mode

Solid–Liquid Two-Phase Flowmeter Flow-Passage Wall Erosion Evolution Characteristics and Calibration of Measurement Accuracy

Solid–liquid two-phase flowmeters are widely used in critical sectors, such as petrochemicals, energy, manufacturing, the environment, and various other fields. They are indispensable devices for measuring flow. Currently, research has primarily focused on gas–liquid two-phase flow within the flowmeter, giving limited attention to the impact of solid phases. In practical applications, crude oil frequently contains solid particles and other impurities, leading to equipment deformation and a subsequent reduction in measuring accuracy. This paper investigates how particle dynamic parameters affect the erosion evolution characteristics of flowmeters operating in solid–liquid two-phase conditions, employing the dynamic boundary erosion prediction method. The results indicate that the erosion range and peak erosion position on the overcurrent wall of the solid–liquid two-phase flowmeter vary with different particle dynamic parameters. Erosion mainly occurs at the contraction section of the solid–liquid two-phase flowmeter. When the particle inflow velocity increases, the erosion range shows no significant change, but the peak erosion position shifts to the right, primarily due to the evolution of the erosion process. With an increase in particle diameter, the erosion range expands along the inlet direction due to turbulent diffusion, as particles with lower kinetic energy exhibit better followability. There is no significant change in the erosion range and peak erosion position with an increase in particle volume fraction and particle sphericity. With a particle inflow velocity of 8.4 m/s, the maximum erosion depth reaches 750 μm. In contrast, at a particle sphericity of 0.58, the minimum erosion depth is 251 μm. Furthermore, a particle volume fraction of 0.5 results in a maximum flow coefficient increase of 1.99 × 10−3.

Chiral induction and amplification of achiral molecules induced by chiral compounds in solid matrices

Abstract To demonstrate chiral induction and amplification in the solid state, we investigated co-crystals prepared from (S)- or (R)-1-phenylethylamine and achiral biphenyl-4-carboxylic acid by solvent-free crystallization. The chiroptical and optical properties of the co-crystals were characterized by circular dichroism spectroscopy, Fourier transform infrared spectroscopy, and time-dependent density functional theory calculations, revealing chiral induction and amplification in the solid phase.

Enhancing flame retardancy and dielectric performance of epoxy resins through benzoxazine-phosphorus modification

A P/N-containing flame retardant, DOPOBH, was synthesized with salicylaldehyde, p-aminophenol, 9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide (DOPO) and formaldehyde. The performance of DOPOBH in flame retardant modification of 4,4′-diaminodiphenyl sulfone(DDS)/diglycidyl ether of bisphenol A (DGEBA, E−44) system was studied in terms of limiting oxygen index (LOI), vertical burning testing (UL-94) and cone calorimeter test (CCT). When the phosphorus content was 1.5 wt% of the whole system, DOPOBH modified epoxy resin (EP/P1.5) exhibited excellent flame retardancy (achieving a UL-94 V-0 rating and the LOI value of 35.2 %). Compared with pure EP, a 54.3 % decrease of peak heat release rate (PHRR) and ca. 5 times of residue (with an intumescent structure) was obtained with EP/P1.5 in CCT. Based on the results of CCT, scanning electron microscope (SEM), thermal gravimetric analysis (TGA) and thermogravimetry-infrared spectroscopy (TG-IR), DOPOBH was verified to play important roles in both gas phase and solid phase. In addition, the addition of DOPOBH could improve the dielectric properties of epoxy resin and provide new strategies for high-performance applications in electronic packaging.

Understanding aging characteristics of a pyrotechnic initiator through performance modeling in Closed Bomb Tests

AbstractWe conducted an analysis of the natural aging characteristics of an electric pyrotechnic initiator stored for 11 years, using 10‐cm3 Closed Bomb Tests (CBTs). For the comparative analysis, we utilized the closed bomb test data from other three batches that were tested 11 years ago when they were produced. Notably, two aged samples exhibited peculiar phenomena in terms of maximum pressure and the time taken to reach it, both of which are the performance indicators of Closed Bomb Tests. The time taken to reach maximum pressure increased in both aged samples compared to the pristine samples. Additionally, while one aged sample demonstrated a higher maximum pressure, the other displayed a significantly lower value compared to the pristine ones. Through statistical analysis of test results from three batches of the reference samples and one batch of aged samples led us to propose the existence of a natural aging effect on the initiator. The increase in time taken to reach maximum pressure compared to the reference samples can be attributed to the phenomenon of an increasing particle size distribution of spherical combustion particles in the present combustion model. Furthermore, the aging of the binder of the initiator charge likely contribute to a relative increase in the size of the combustion particles due to the binder hardening over time. To explain the phenomenon of the pressure initially reaches its maximum value on the CBT pressure‐time curve and subsequently decrease, we introduce the concept of condensation, where the gas phase transitions into liquid and solid phases.

Ceria nanoparticles: biomedical applications and toxicity.

Ceria nanoparticles (CeO2 NPs) have become popular materials in biomedical and industrial fields due to their potential applications in anti-oxidation, cancer therapy, photocatalytic degradation of pollutants, sensors, etc. Many methods, including gas phase, solid phase, liquid phase, and the newly proposed green synthesis method, have been reported for the synthesis of CeO2 NPs. Due to the wide application of CeO2 NPs, concerns about their adverse impacts on human health have been raised. This review covers recent studies on the biomedical applications of CeO2 NPs, including their use in the treatment of various diseases (e.‍g., Alzheimer's disease, ischemic stroke, retinal damage, chronic inflammation, and cancer). CeO2 NP toxicity is discussed in terms of the different systems of the human body (e.‍g., cytotoxicity, genotoxicity, respiratory toxicity, neurotoxicity, and hepatotoxicity). This comprehensive review covers both fundamental discoveries and exploratory progress in CeO2 NP research that may lead to practical developments in the future.

Determination of zinc in dried nuts by slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS) with citric acid-coated magnetic nanoparticle (CAMNP) based solid phase extraction (SPE)

This study reports a sensitive method for trace zinc using slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS) with citric acid-coated magnetic nanoparticle-solid phase extraction (CAMNP-SPE). To increase the efficiency, we univariately optimized the pH, buffer volume, CAMNP mass, eluent concentration and volume, mixing type and time, temperature, and interaction time. The study identified the limits of detection and quantification values for CAMNP-SPE-SQT-FAAS under the specified optimum conditions to be 12.30 and 41.00 μg L−1, respectively. The newly developed method improved the detection power of traditional FAAS by 13.25 times. The findings of this study report a sensitive and accurate method to determine trace zinc in complex matrices.

Exploring the influence of additives on the ignition, combustion and quenching of electrically controlled solid propellants

AbstractThe influence of additives on the decomposition and combustion characteristics of electrically controlled solid propellants was investigated through small scale experiments. Carbon black and aluminum additives were explored in a polyethylene oxide, lithium perchlorate propellant. Additives were used to improve the voltage response and their impact on ignition and combustion was characterized. The data showed that conductive additives can mitigate the loss of solid phase conductivity through solvent evaporation and that ignition delay decreases with higher voltage and solid phase conductivity. Steady‐state combustion experiments showed that electrical decomposition of the propellants proceeded more rapidly than a purely thermal stimulus illustrating the importance of electrochemistry in ECSP combustion. The combined effects of pressure and voltage on combustion rates were summarized in Saint‐Robert's burn relations. The regression rates increased with both applied voltage and pressure. The pressure deflagration limit of propellants with the carbon black additive was significantly reduced compared to a neat PEO/LP propellant, whereas the addition of 10 % aluminum did not affect the pressure deflagration limit.

HYGROSCOPIC WATER CONTENT AS AN INDICATOR OF SOIL DISPERSITY:THERMODYNAMIC BASIS AND EXPERIMENTAL VERIFICATION

The adsorption properties of dispersed systems are determined by their surface energy, therefore the indicators of hygroscopy (adsorbed water content) and dispersity (specific surface area of the solid phase) of soils and sediments are in close mutual correlation. This well-known empirical fact received a new fundamental interpretation based on the theory of disjoining water pressure according to Deryagin in the form of a thermodynamic equation connecting the specific surface area, hygroscopic water content of soil samples and the relative humidity of the air in the laboratory room. The theoretical equation allowed us to substantiate the methodology for quantifying the hydrophilic specific surface area of soil samples based on widespread data on their hygroscopy. A comparison of the new method with the standard BET-analysis of the specific surface area, as well as with the previously proposed physically based method for its determining by the slope of thermodynamic water retention curves, showed their statistically reliable agreement in a wide range of estimated specific surface area values from 5 to 340 m2×g-1 for soil samples of different genesis and texture.

Effect of multi wall carbon nanotubes during semi-solid to solid phase transformation in eutectic Al-Si alloy

The study explores numerically the combined effect of the base metal pouring temperature and MWCNT (multi wall carbon nanotubes) during semi-solid to solid solidification of Al-Si-MWCNT composite material. The semi-solid to solid solidification actually differs significantly both qualitatively and quantitatively from the liquid to solid solidification. During solidification of Al-Si-MWCNT composite material, the melt temperature and the cooling rate play crucial roles in the phase transformations. During liquid to solid solidification, the MWCNT significantly affects the cooling rate, leading to multiple recalescence phenomena, and influences the formation and evolution of the columnar and globular grains. Under the same condition, the MWCNT also impacts the silicon segregation, causing fluctuations in the silicon phases and its redistribution. However, during the semi-solid to solid solidification, it is observed that by decreasing the melt temperature into a semi-solid state, the segregation rate of silicon decreases which enhances more homogeneous CNT distribution. It also increases the globular volume fraction and dominates the columnar growth. Overall, the future trend of semi-solid to solid solidification of Al-Si-MWCNT composite materials lies in optimizing their properties for specific applications, expanding their use across diverse industries, and promoting sustainable manufacturing practices.

Characteristics of synovial trihybrid nanofluid activation energy and Marangoni convective flow: A Computational framework of local thermal non-equilibrium

The impact of nonlinear heat source and activation energy on magnetized Synovial trihybrid nanofluid Marangoni convective flow across a sheet combining two viscosity models is investigated in this study. Heat sources, activation energy, and conditions of local thermal non-equilibrium (LTNE) are all considered in the modelling. Based upon energy equations, the LTNE model provides unique heat transport for both liquid and solid phases. This leads to the utilization of different temperature profiles for the fluid and solid phases in this work. A trihybrid fluid is created by combining the basic fluid blood with MWCNT (multi-wall carbon nanotubes), SWCNT (single-wall carbon nanotubes) and sliver nanoparticle. This study significant potential in several fields. The effects of parameters on friction between joints are examined, which aids in the analysis of the lubricant nature of Synovial trihybrid nanofluid. A significant finding of the current work is that the thermal profiles decrease with higher values of the Concentration-dependent viscosity parameter, but the velocity profile increases. An increase in the inter-phase heat transfer characteristic raises the liquid phase's thermal profile while lowering the solid phase's thermal profile.

UiO-66@Fe3O4 nanocomposite as an adsorbent in dispersive solid phase extraction of metformin in surface water and wastewater

Metformin, an anti-hypoglycemic medication, has been used for decades due to its efficiency and is the most consumed pharmaceutical drug worldwide. Consequently, monitoring its concentration in environmental water is important due to its suspected effect on human health and aquatic life. This study reported the extraction, preconcentration, separation and determination of metformin (MET) in waters. Dispersive solid phase extraction (dSPE) using UiO-66@Fe3O4 nanocomposite as a sorbent was used to extract and preconcentrate MET. The high-performance liquid chromatography-diode array detector (HPLC-DAD) achieved the separation and quantification of MET in the samples. Experiemental design was used to optimise influential variables in the extraction and preconcentration of MET. The linearity, limit of detection (LOD) and limit of quantification (LOQ) for MET were 0.5–100 μg L−1 (R2 = 0.9987), 0.16 μg L−1 and 0.53 μg L−1, respectively. The intraday (n = 10 same-day replicates) and interday (n = 5 consecutive days) precisions reported as relative standard deviations (RSD %) were less than 5%. The accuracy of the method expressed as percentage recovery (%R) ranged from 84 to 112%. The method was applied to extract and preconcentrate MET in wastewater and river water samples. The MET was detected in greater concentrations in wastewater than in river water samples. The validation based on specificity, trueness, linearity, precision, and application to the analysis of MET in real samples showed that the combination of dSPE and HPLC-DAD methods is applicable for MET monitoring in surface water and wastewater. Furthermore, the dSPE/HPLC-DAD method was rapid, simple and suitable for estimating the concentrations of MET in South African surface water and wastewater for the first time. Lastly, the environmental risk caused by the occurrence of MET in surface water was investigated in terms of hazard quotient (HQ). The HQ values were less than unity, suggesting a low possibility risk for the aquatic organisms.

Impact of salt content on Douchi metabolites: biogenic amines, non-volatile compounds and volatile compounds.

The excessive salt intake associated with Douchi has become a topic of controversy. Addressing this concern and enhancing its market competitiveness necessitates the application of salt reduction fermentation in Douchi. Therefore, to promote the application of salt reduction fermentation in Douchi, a comprehensive study was undertaken aiming to investigate the differences in biogenic amines, volatile compounds and non-volatile compounds in Douchi with varying salt content. The findings unequivocally demonstrate that salt hampers the formation of metabolites in Douchi. As the salt content increased, there was a significant decrease (P < 0.05) in the levels of total acid, amino-type nitrogen and free amino acids in Douchi. Notably, when the salt content exceeded 80 g kg-1, there was a substantial reduction (P < 0.05) in putrescine, lactic acid and malic acid levels. Similarly, when the salt content surpassed 40 g kg-1, β-phenethylamine and oxalic acid levels exhibited a significant decline (P < 0.05). Furthermore, the results of E-nose and principal component analysis based on headspace solid phase microextraction gas chromatography-mass spectrometry revealed notable discrepancies in the volatile compound content between Douchi samples with relatively low salt content (40 and 80 g kg-1) and those with relatively high salt content (120, 160 and 200 g kg-1) (P < 0.05). By employing partial least squares discriminant analysis, eight distinct volatile compounds, including o-xylene, benzaldehyde and 1-octen-one, were identified. These compounds exhibited higher concentrations in Douchi samples with relatively low salt content (40 and 80 g kg-1). The sensory results showed that Douchi samples with lower salt content exhibited higher scores in the soy sauce-like and Douchi aroma attributes. In conclusion, this study significantly enhances our understanding of the impact of salt on metabolites in Douchi and provides invaluable insights for the development of salt reduction fermentation in this context. © 2024 Society of Chemical Industry.