Evolution Of Functional Groups Research Articles

Kinetics of pyrolysis and Computational Fluid Dynamics modeling of low metamorphic coal

AbstractThis study explores the low‐temperature pyrolysis kinetic of low metamorphic grade coal from Northern Shaanxi, utilizing Fourier transform infrared (FT‐IR) spectroscopy to analyze the characteristics of various functional groups over a 293–1023 K temperature range. A kinetic model, correlating with the pyrolysis behaviors of these groups, was developed through thermal analysis kinetics. Computational fluid dynamics (CFD) technology simulated the furnace's flow dynamics, allowing an examination of the physical field alterations and functional group evolution during pyrolysis. Results showed that the pyrolysis kinetic functions for aromatic C–H, C=C, C–O, and •OH, along with temperature, pressure, and velocity fields, were successfully integrated into the simulation. This integration provided detailed insights into the temperature profile, pressure distribution, flow velocities, and functional group distribution in the furnace. Aliphatics, exhibiting the largest mass fraction and wide pyrolysis temperature range, and •OH radicals with the highest activation energy were concentrated in the furnace's pyrolysis zone center. C=C's distribution was influenced by aromatic C–H and aliphatics, showing a complementary pattern. The oxygen‐containing groups C–O and C=O had similar pyrolysis mechanisms and uniform distribution. The functional groups' mass fractions were ranked from highest to lowest as follows: aliphatics > •OH > aromatic C–H > C–O > C=C > C=O.

Visualization and Analysis of Mapping Knowledge Domains for Coal Functional Groups

ABSTRACT In this paper, a systematic review of the research on functional groups in coal is presented. In recent years, the research on functional groups in coal has been extended from the macroscopic level to the microscopic layer, and a large number of studies have shown that functional groups have significant effects on various properties of coal, such as gas adsorption and spontaneous combustion. To understand the current status and future trends of research on functional groups in coal, this study analyzed 3956 papers on this topic published in the Web of Science (WOS) core database from 2000 to 2022. The spatial and temporal distribution characteristics of publications, authors, countries, institutions, and major journals were visualized using VOSviewer and CiteSpace. Keyword co-occurrence and burst analysis are used to reveal the research status and hotspots in this field. The results show that the development of research on functional groups in coal goes through three stages: the fluctuating development period, the steady development period, and the results explosion period; China, USA, Australia, Japan, and India are the most active countries in the field of coal functional groups research, and China has a greater advantage in the number of publications and influence. A core group of institutions, mainly research universities, has been formed in this field, and Fuel, Energy and Fuels and Fuel Processing Technology are the main source journals for published results on coal functional groups. At present, the framework of basic theories and research methods is complete, and the study of functional groups for gas adsorption, the analysis of the evolution of functional groups in the process of coal thermodynamic behavior, and the characteristics of functional group categories and distribution in coal are the main knowledge framework basis for the study of functional groups in coal. The research on coal functional groups has been extended to the molecular level, and in the future, quantum chemistry, molecular simulation, and fine characterization research of functional groups will become the frontier of research in the field of coal functional groups.

Graphene oxide under the nanoscope: A comprehensive study of nanoindentation behavior

Graphene oxide membranes are expected to become one of the most important materials for technological applications due to their highly reactive surface, being directly related to their atomistic configuration. The understanding of its structure and physicochemical properties under mechanical deformation is becoming crucial in the development of new applications; however, the role of the different functional groups in the membrane and their response to external factors like indentation is still unclear. Nanoindentation experiments show elastic behavior when the penetration is small compared to the indenter radius and the membrane diameter. Molecular Dynamics simulations for large 3-layer graphene oxide membranes were carried out for a 50% oxidation content and the inclusion of epoxy and hydroxy groups. Simulations showed an elastic modulus similar to experimental values. After the elastic regime, the mechanical behavior is dominated by the evolution of functional groups. A quasi-elastic regime is uncovered, where unloading leads to self-healing of broken bonds. Finally, large indenter penetration leads to fracture, with fracture stress similar to experimental values.

Evolution of oxygen-containing functional groups on coal char surface during gasification in H2O/CO2

Gasification converts coal into syngas (CO and H2) for downstream utilization. The most important reaction in an autothermal gasifier is the char−H2O/CO2 reaction. The evolution of C(O) complexes on the coal char surface directly determines the pathways and rates of CO and H2 generation. This study mainly used a fixed bed reactor to prepare Zhundong coal char with different reaction levels in H2O and CO2, and its surface carboxyl, lactone, phenolic hydroxyl, and hydroxyl functional groups were systematically analyzed by using Boehm titration, FT-IR, and XPS. The results show that the contents of the four oxygen-containing groups in raw coal are in the order of carboxyl＞lactone＞phenol hydroxyl＞hydroxyl. In H2O gasification, the lactone groups were more susceptible to H2O resulting in a significant increase in carboxyl content at the early stage of the reaction. The hydroxyl, as a very active group in the reaction, and the amount of its generation and consumption was very obvious. The phenolic hydroxyl−the least thermally stable group among these four types of groups, was unable to participate in the inter-transformation between oxygen-containing functional groups during the gasification. During CO2 gasification, the hydroxyl was rapidly consumed at the initial stage of the reaction and then shown a slow growth trend, and the newly generated hydroxyl would continue to undergo dehydrogenation to form new functional groups. At the end of the reaction, the transformation of other oxygen-containing functional groups into more stable carbonyl groups leads to a sudden increase in the content of carboxyl and lactone. In this work, Boehm titration was introduced into the determination of oxygen-containing functional groups on the surface of char during gasification in H2O/CO2.

New insights into the effect of pyrolysis temperature on the spectroscopy properties of dissolved organic matter in manure-based biochar.

Dissolved organic matter (DOM) derived from biochar takes a crucial role in transport and bioavailability toward contaminants; hence, it is undeniable that a thorough analysis of its properties is important. So far, the effect of pyrolysis temperature on the functional groups, components, and evolutionary sequence of manure-based biochar DOM has not been adequately investigated. Here, DOM was released from two typical livestock manures (cow and pig) at five pyrolysis temperatures (300 ~ 700°C), and it was explored in depth with the aid of moving window 2D correlation spectroscopy (MW-2D-COS) and heterogeneous 2D correlation spectroscopy (hetero-2D-COS). The results demonstrated that the concentration, aromaticity, and hydrophobicity of DOM were greater at high temperatures, and more DOM was liberated from cow manure-based biochar at identical temperature. Protein-like compounds dominated at high temperatures. The pyrolysis temperatures of final configuration transformation points of the fulvic acid-like component and the aromatic ring C=C in DOM were 400°C and 500°C, respectively. Moreover, Fourier transform infrared spectroscopy combined with two-dimensional correlation analysis indicated that the functional group evolution of DOM depends on the pyrolysis temperature and feedstock type. The study provides a new perspective on manure management and environmental applications of biochar.

Diesel soot combustion in air-NO environment: Evolution of functional groups on soot surfaces

It is inevitable for NO to be involved in the soot combustion in diesel particulate filters (DPFs), so giving full play to the NO oxidation activity is one of the most effective means to improve the DPF regeneration performance. In this work, based on the results of programmed temperature oxidation (TPO) experiments, Fourier transfer inference spectroscopy, and X-ray photoelectron spectroscopy, the evolution of surface functional groups was seriously analyzed to explore the soot oxidation mechanism. The results revealed that with the presence of NO in the air atmosphere, the concentration of -ONO2 groups showed an increasing trend in the early oxidation stage of 0–20 % oxidation degree (OD) and then slowly decreased during 20–80 % OD, while the variations in CH functional group concentration were directly related to the concentration NO in the air atmosphere. COO functional group is easy to decompose, and NO promotes COO's generation and decomposition. The sp3/sp2 hybrid ratio is strongly correlated with CO (carbon‑oxygen double bond), but the content of CO is also affected by the desorption of COO functional groups. It is worth noting that when the soot oxidation degree is at 50 %–80 % OD, CO groups are converted to CO functional groups.

Molecular-level insights into the temperature-dependent formation dynamics and mechanism of water-soluble dissolved organic carbon derived from biomass pyrolysis smoke

Water soluble organic carbon (WSOC) derived from biomass pyrolytic smoke is deposited through atmospheric aerosols, negatively affecting aquatic ecological quality and safety. However, the temperature-dependent molecular diversity and dynamic formation of smoke-derived WSOC remain poorly understood in water. Herein, we explored the molecular-level formation mechanism of pyrolytic smoke-derived WSOC in water to explain the evolution, heterogeneous correlations, and sequential responses of molecules and functional groups to increasing pyrolysis temperature. Two-dimensional correlation spectroscopy was used to innovatively establish the characteristic correlations between spectroscopy and Fourier transform-ion cyclotron resonance mass spectrometry. Temperature-dependent formation of WSOC exhibited diversity in absorbance/fluorescent components, unique/common molecules, and their chemical parameters, showing the simultaneous formation and degradation reactions. The common WSOC molecules with lower and higher degrees of oxidation showed significant positive and negative correlations with the fluorescent components, respectively. The primary sequential response of WSOC molecules to increasing pyrolysis temperature (lignin-like molecules → unsaturated hydrocarbons, condensed aromatic molecules → lipid-like/aliphatic-/peptide-like molecules) corresponded to the temperature response of functional groups (carboxylic/alcoholic → polysaccharides → aromatics/amides/phenolic/aliphatic groups), demonstrating well synergistic relationships between them. These novel findings will contribute to the comprehensive understanding and assessments of potential environmental behavior or risks of WSOC in aquatic ecosystems.

A surrogate shale oil model based on a multi-objective fusion adaptive optimization considering its pyrolysis characteristics

A surrogate shale oil model was proposed based on model compounds with optimal proportions to reduce the complexity of Huadian shale oil to analyze its pyrolysis kinetics. There are mainly n-alkanes and n-olefins with C8–C36 in shale oil according to GC-MS results, a small amount of aromatics and alcohols, as well as trace of esters, ketones and nitriles, etc. Pyrolysis behavior of shale oil was investigated by Py-GC-MS and FTIR, including the evolution of pyrolytic products and functional groups. Here, n-eicosane, 1-octadecene, pentadecanol and nonylbenzene were selected as surrogates based on GC-MS result. To obtain the optimal surrogate model, a novel multi-objective fusion adaptive optimization function with constraints was proposed to determine the optimal weighting factor of each component from the pareto optimal set. Then, the detailed pyrolysis kinetic mechanisms containing 745 species and 19392 reactions were developed to study its thermochemical conversion. Moreover, the skeletal mechanism reduced by decoupling and directed relation graph (DRG) was used to describe the thermal flow reactivity of these four components. In sum, this work provides an integrated description of shale oil pyrolysis, and gives a new method for studying the pyrolysis of oil shale intrinsically.

Pressure-driven multiple optoelectronic evolution in CsMoO3(IO3) with dual functional [MoO6] and [IO3] groups

Pressure-induced optoelectronic changes were observed in CsMoO3(IO3) by evolutions of dual functional groups, including piezochromism, second harmonic generation transformation, and the enhancement of the photocurrent switching ratio.

Understanding the Improved Sodium Ion Storage in Wood-Derived Hard Carbon Anodes by Hydrogen Treatment

Biomass carbon, as a renewable resource, has the ability to be a hard carbon anode material for sodium-ion batteries. Its performance is highly reliant on the surface functional group. Through our work, successfully synthesized the high-performance hard carbon by the treatment of the hydrogen reduction process of rose willow. Moreover, the effects of hydrogen reduction on the evolution of functional groups and the relevant electrochemical performance have been investigated. After undergoing hydrogen reduction treatment, hard carbons’ surface features and layer spacing were greatly enhanced. In addition, the partial surface C=O group was reduced to C-O, which led to the Na+ adsorption active sites and pseudo-capacity increased, thus improving the dynamics of the electrode process. As anticipated, the resulting hard carbon exhibited a capacity of 325 mAh g−1, with an initial coulomb efficiency (ICE) of 80.84%. This study is in an effort to demonstrate the possibility of biomass-based carbon materials in preparation for future commercial applications of sodium-ion batteries.

Evolution and oxidation properties of the functional groups of coals after water immersion and air drying

The evolution of functional groups, the gas generation laws in oxidation and temperature increase, and the oxidation kinetics parameters of the coal samples immersed in water for 30 days, 90 days, and 150 days (hereinafter referred to as 30 d coal, 90 d coal, and 150 d coal, respectively) were analyzed through Fourier transform infrared spectrometer, programmed temperature increase test system, and thermal gravimetric analyzer to disclose spontaneous combustion and the influencing mechanism of long-flame coals immersed in water for a long period. Results show that the aliphatic hydrocarbon and the hydroxyl contents of the coal samples increase after water immersion and air drying. In particular, the aliphatic hydrocarbon contents in 30 d coal, 90 d coal, and 150 d coal increase from 12.61 % for raw coal to 15.84 %, 14.08 %, and 13.90 %, respectively, whereas the hydroxyl content increases from 48.75 % for raw coal to 50.77 %, 50.13 %, and 49.23 %, respectively. In the low-temperature oxidation process, the CO output increases, and the apparent activation energy declines. When the temperature is 200 °C, the CO outputs of 30 d coal, 90 d coal, and 150 d coal are 28088, 25421, and 22112 ppm, which are 37.4 %, 24.4 %, and 8.2 % higher than the CO output of raw coal (20437 ppm), respectively. The apparent activation energy decreases from 65.7 kJ mol−1 for raw coal to 61.12 kJ mol−1, 63.08 kJ mol−1, and 64.5 kJ mol−1. According to the comparison of characteristic temperature points, the temperature of the mass extreme (T3) and the temperature of ignition point (T4) of the immersed coal samples both decrease. The T3 values of 30 d coal, 90 d coal, and 150 d coal decrease from 282.71 °C for raw coal to 274.87, 278.33, and 280.50 °C, whereas their T4 values decrease from 424.24 °C for raw coal to 419.23, 420.14, and 423.42 °C, respectively. This study proves that water immersion increases the oxidative activity of coals, thereby simplifying spontaneous combustion.

Apparent activation energy of mineral in open pit mine based upon the evolution of active functional groups

This study aimed to investigate the mechanism of mineral spontaneous combustion in an open pit. On the study of coal and mineral mixture in open pit mines, as well as through the specific surface area and Search Engine Marketing (SEM) experiments, the specific surface area and aperture characteristics of distribution of open pit coal sample and pit mineral mixture samples were analyzed. Thermal analysis experiments were used to divide the oxidation process was divided into three stages, and the thermal behavior characteristics of experimental samples were characterized. On the basis of the stage division, we explored the transfer law of the key active functional groups of the experimental samples. The apparent activation energy calculation of the key active groups, performed by combining the Achar differential method with the Coats–Redfern integral method, microstructural and oxidation kinetic properties were revealed. The resulted showed that the mixed sample had high ash, the fixed carbon content was reduced, the specific surface area was far lower than the raw coal, the large aperture distribution was slightly higher than the medium hole, the micropore was exceptionally low, the gas adsorption capacity was weaker than the raw coal, the pit coal sample had the exceedingly more active functional groups, easy to react with oxygen, more likely to occur naturally, and its harm was relatively large. The mixed sample contained the highest C–O–C functional group absorbance. The functional groups were mainly influenced by the self-OH content, alkyl side chain, and fatty hydrocarbon in the sample. The main functional groups of the four-like mixture had the highest apparent activation energy, and the two reactions were higher in the low-temperature oxidation phase.

Effect of oxygen-containing functional groups on the micromechanical behavior of biodegradable plastics and their formation of microplastics during aging

Biodegradable plastics (BPs) are more prone to generate harmful microplastics (MPs) in a short time, which have always been ignored. Oxygenated functional group formation is considered to be a key indicator for assessing microplastic formation, while it is difficult to characterize at a very early stage. The micromechanical properties of the aging plastic during the formation of the MPs are highly influenced by the evolution of oxygen-containing functional groups, however, their relationship has rarely been revealed. Herein, we compared changes in the physicochemical properties of BPs and non-degradable plastic bags during aging in artificial seawater, soil, and air. The results showed that the oxidation of plastics in the air was the most significant, with the most prominent oxidation in BPs. The accumulation of carbonyl groups leads to a significant increase in the micromechanical properties and surface brittleness of the plastic, further exacerbating the formation of MPs. It was also verified by the FTIR, 2D-COS, AFM, and Raman spectroscopy analyses. Furthermore, the increased adhesion and roughness caused by oxygen-containing functional groups suggest that the environmental risks of BPs cannot be ignored. Our findings suggest that the testing of micromechanical properties can predicate the formation of the MPs at an early stage.

Pyrolysis behavior of tar-rich coal with various coal-forming environments: A TGA and in-situ transmission FTIR study

Tar-rich coal, abundant in northwestern China, undergoes variations in the coal-forming environment, resulting in diverse occurrences of tar-rich coal and its molecular structures across regions and layers. The pyrolysis process of these coals also differs accordingly. This study investigated four coal samples with different tar yields and indicative of various coal facies using thermogravimetric analysis and in-situ transmission FTIR, and revealed that coal facies significantly affect tar yield by controlling the molecular structure. In particular, coal samples formed in a stronger reducing environment contain higher levels of aliphatic and oxygen-containing functional groups. Consequently, during pyrolysis, a substantial proportion of Cal-Cal, Cal-H, Cal-O, and Cal-N bonds were broken, contributing to approximately 30–60 % of the total cracked bonds, and X18 exceeded Z52 by a significant 21.55 %, leading to higher tar yields. In-situ transmission FTIR observations indicated that coal samples formed in a stronger reducing environment exhibit higher contents of –CH2–, –CH–, C–O, and CO structures, which decompose more rapidly after 400 °C, and X18 with the highest decomposition of 18.51 % in C–O, while Z52 had the minimum. Moreover, coal samples formed in a stronger reducing environment exhibit a more significant reduction in –CH– structures compared to –CH2– and free-ends –CH3 structures beyond 400 °C, while coal samples formed in a weaker reducing environment display higher reductions in free-ends –CH3 and –CH2– structures than –CH– structures. The formation of gaseous products during coal pyrolysis is closely linked to the decomposition and evolution of residual coal functional groups, with increased accumulation observed under more enhancing and reducing conditions. These findings offer valuable insights into optimizing tar-rich coal resource utilization and the development of effective pyrolysis techniques.

Stage changes in the oxidizing properties of long-term water-soaked coal and analysis of key reactive groups

To elucidate the impact of prolonged water immersion on the evolution of key active functional groups during the low-temperature oxidation of coal, the programmed temperature ramping method, in-situ Fourier transform infrared spectroscopy (in-situ FTIR), microcalorimetry (C80) experiments, thermodynamic analysis, and gray and Pearson correlation analysis were performed. The analysis involved coal samples exposed to different immersion durations (3, 6, 9, and 12 months). The results reveal that long-term water immersion exerts a stage-wise influence on the oxidation characteristics of coal, with the critical time point being 6 months. Before this period, the gradual accumulation of active sites progressively enhances the oxidation characteristics. However, after 6 months, the generation of active sites is suppressed, resulting in a gradual weakening of the coal's oxidation behavior. Correlation analysis revealed that the correlation between free hydroxyl groups and gaseous products is strongest in coal immersed for 6 months (A6), with a correlation coefficient of 0.91. During the accelerated oxidation stage, the heat released from the soaked coal is significantly greater than that in other stages, which promotes the formation of C=O and –COOH functional groups and further reduces the apparent activation energy. According to the Coats–Redfern method, A6 exhibits the smallest apparent activation energy—only 30 % of the original value of coal. The correlation between free hydroxyl groups and apparent activation energy is strongest at this stage, with a correlation coefficient of 0.92. This indicates that free hydroxyl groups and the accelerated oxidation stage are, respectively, the key active functional groups and critical phases in the coal oxidation process.

Evolution of surface functional groups and aromatic ring degradation upon treatment of polystyrene with hydroxyl radicals

The surface properties of hydrocarbon polymers are inadequate for numerous applications. Hence, they require alteration via functionalisation with desired functional groups. Hydroxyl groups are often preferred, since they enable appropriate polarity for the irreversible grafting of desired molecules. In this study, the surface kinetics resulting from the treatment of polystyrene with hydroxyl (OH) radicals from the gas phase was fundamentally investigated through a precisely-designed experiment. Polystyrene samples were exposed to various known fluences of OH radicals, and the evolution of surface functional groups versus the OH fluence was monitored using high-resolution X-ray photoelectron spectroscopy (XPS). The fluences of OH radicals varied between 1 × 1018 and 4 × 1023 m−2 in the process of finding a threshold fluence for the formation of specific groups. The surface concentration of carbonyl (C=O) groups could be measured using XPS at a fluence of approximately 5 × 1020 m−2. The C=O groups became measurable at a fluence of approximately 1.5 × 1021 m−2, and carboxyl (COOH)/ester groups at approximately 4 × 1021 m−2. As deduced from the XPS, a concentration of C=O groups at approximately 5 % occurred before the degradation of the aromatic ring. The formation of other oxygen-functional groups required opening of the aromatic ring. The results have been explained using a two-step process, considering available theories vis-a-vis initial stages in the functionalisation of PS with polar functional groups.

Synergistic effect triggered by Fe2O3 and oxygen-induced hydroxyl radical enhances formation of amino-phenolic humic-like substance

Metal oxides play a promising role in the transformation of polyphenols and amino acids involved in naturally occurring humification. The objective of this study was to explore the synergistic interactions between Fe2O3 and O2 in the formation of humic substances under a controlled O2 atmosphere (0%, 21% and 40% O2 levels). The results indicate that an O2 level of 21% with Fe2O3 was optimal for humic acid (HA) production. Hydroxyl radicals (∙OH) formed and promoted the formation of HA in the presence of O2, and O2 improved the enhancing capacity of Fe2O3 by oxidizing Fe(II) to Fe(III). Moreover, the combination of these processes resulted in a synergistic improvement in humification. The evolution of functional groups in HA suggested that O2 promoted the formation of oxygen-containing groups such as lipids, and Fe2O3 was conducive to the formation of dark-coloured polymers during the darkening process of humification. Furthermore, the O2 level of 40% inhibited the formation of HA by reducing the transformation from Fe(III) to Fe(II). The XRD results showed few changes in the composition of Fe2O3 before and after humification, which indicated that Fe2O3 was a catalyst and an oxidant. The heterospectral UV–Vis/FTIR results suggested that ∙OH attacked phenolic rings to form the aromatic ring skeleton of HA and benefit the ring-opening copolymerization of humic precursors. In addition, structural equation modelling demonstrated that dissolved Fe was the key parameter affecting the HA yield. These findings provide new insights into the synergism of O2-mediated ∙OH production associated with metal oxide-facilitated humification.

Interactions between cellulose and lignin during pyrolysis: Evolutions of condensed-phase functional groups and gas-phase volatile fraction

Understanding cellulose-lignin interactions during biomass pyrolysis is important to improve the overall product distribution and quality. In the current study, the condensed-phase cellulose-lignin interactions during biomass pyrolysis from 100° to 600°C were systematically investigated with in-situ diffuse reflectance infrared Fourier transform spectroscopy and modified perturbation correlation moving-window two-dimensional correlation spectroscopy. It was found that compared to the individual component pyrolysis, the decomposition peak, evident by thermogravimetric analysis, of cellulose-lignin co-pyrolysis became wider and shifted to higher temperature range. The cellulose-lignin interactions further promoted the formations of char, and H2O, CH3/CH2, CO, aromatic-containing compounds. With simultaneous IR identification of gaseous products and condensed-phase remaining, the detailed interaction mechanism was elucidated as: 1) hydrogen donation from cellulose hydroxyl to lignin Cα could promote the lignin rearrangement at low temperature range through quinone methide structure; 2) the reactive species from homolytic cracking of lignin could abstract hydrogen from CH/CH2 groups of cellulose to generate phenolic compounds; 3) dehydration reactions of cellulose was therefore enhanced to promote char formation.

Synergistic effect on low-pressure pyrolysis of biomass-plastic mixture as representative of Tibetan tourism solid waste

Tibetan tourism solid waste (TSW) has attracted worldwide attention due to its increased production and the potential environmental risks associated with its improper disposal. According to a survey on TSW, catering industry is the main source of TSW, thus a mixture of starch and low-density polyethylene (LDPE) was selected to simulate Tibetan TSW, and pyrolysis of single and mixed components has been performed in a vertical tube furnace with variable pressure. The effects of temperature (400–700 ℃) and pressure (0.02–0.1 MPa) on the distribution of pyrolysis products and the composition of the gas and liquid phases were investigated. The results show that the simulated TSW pyrolysis has a synergistic effect, more obviously, promoting the production of C1-C3 hydrocarbons in the gas phase and inhibiting the production of oxygenated organic matter in the liquid phase. In addition, the properties of the simulated TSW pyrolysis process and the time evolution of various functional groups were studied by TG-FTIR, and it was observed that the simulated TSW pyrolysis followed two stages of degradation: biomass degradation from 250° to 370 °C and then plastic degradation from 420° to 510 °C. This study provides basic knowledge of thermochemical process in Tibet, thus paving the way for clean and efficient treatment of TSW.

Sulfate resistance and degradation mechanism of basalt fiber modified graphite tailings cement-based materials

This paper delves into the modification mechanism and deterioration mechanism of basalt fiber (BF) on the sulfate resistance of graphite tailings (GT) cement-based materials. Initially, the comprehensive properties of basalt fiber modified graphite tailings cement mortar (BFM-GTCM) under different sulfate cycles, such as apparent morphology, water absorption and mechanical characteristics were investigated. Subsequently, the relationship between the evolution of microstructure, interface stability, pore structure, chemical composition and functional groups of BFM-GTCM and its resistance to sulfate erosion under different cycles was revealed by various microscopic characterization and analysis methods (SEM/XRD/MIP/FTIR/DSI). Simultaneously, a corrosion coefficient-pore structure relationship model was also put forth based on multivariate regression theory, and the mechanism enhancing BFM-GTCM resistance to sulfate attack was investigated. The results demonstrated that a suitable blend of BF and GT can prevent sulfate ion penetration, significantly slow down the generation of corrosion products (AFt and gypsum) in cement mortar during sulfate attack, postpone the occurrence of new cracks and the growth of existing ones, improve pore structure, and significantly lessen the degree of durability degradation of BF-GTCM. Among them, 0.3% BF addition and 20% GT replacement was the ideal ratio.