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Abstract Using lignite as an adsorbent and subsequently as a material for coal water slurry (CWS) preparation represents an alternative method for coal chemical wastewater treatment. However, the components in these wastewaters could affect the CWS performance, especially ammonia nitrogen (NH 4 +-N). The influencing mechanism of NH 4 +-N was studied through adsorption method. Associated with adsorption reaction model, Fourier transform infrared spectrum and zeta potential detection, it was found that the adsorption reaction of NH 4 +-N, driven by ion-exchange interactions with H+ of –OH and –COOH on the lignite surface, displayed a typical monolayer mode and was much faster than that of NSF which displayed a double-layer mode and was adsorbed preferentially at hydrophobic sites. In binary adsorption, the adsorption amount of NSF was increased remarkably by adding NH 4 +-N. This was attributed to the modified lignite surface and hydrophilic group by NH 4 +-N that decreased the surface electronegativity as well as the electrostatic repulsion among –SO 3 − in NSF molecules. The enhanced adsorption of NSF resulted in capturing more water molecules in hydration film surrounding the particles in CWS. The hydration film was then thickened and stabilized, thus leading to a decrease in free water for CWS flowing. As a result, the apparent viscosity was increased, and CWS tended to be dilatant. In addition, the thickened and stabilized hydration film also increased the yield stress of CWS prepared with NH 4 +-N, resulting in improved stability. [ABSTRACT FROM AUTHOR]

A newly designed two-grade fractal model for improving the packing state in brown coal water slurry (BCWS), which was built on the fractal theory and modified by separating the size into two grades, was investigated systematically. Packing efficiency (PE) and regression levels of the fractal model in various particle systems were analyzed. The results showed that the PE of brown coal particle system is determined mainly by the fractal characteristics of particles under 74 μm and the packing state in BCWS can be significantly improved when the fractal dimension is around 2.6–2.7. In addition, the two-grade fractal model fits the PSDs for various particle systems with different graduation ratios of coarse samples (CS), fine samples (FS) and ultra-fine samples (UFS) well. PE reaches the maximum value when the graduation ratio is 7:0:3 (CS:FS:UFS) and the fractal dimension is 2.7080, which is consistent with the calculated results. It was confirmed by the slurry preparation experiment that the maximum solid loading of BCWS increased by 2.9% through optimizing the packing state using two-grade fractal model. [ABSTRACT FROM AUTHOR]

In the coal water slurry (CWS) industry, it is essential to achieve high packing density of product particles in order to obtain a high concentration without affecting the flowability. In this study, a method based on an index E is proposed for evaluating the packing density of particles in CWS with given particle size distribution (PSD) and tested on bituminous and lignite coal. These two types of coal were ground and mixed in different proportions to obtain different packing densities. The experimental results show that the CWS concentration increased with E , implying the good applicability of the proposed method. By calculating E for different PSDs, it was found that the packing got closest when the parameters in Rosin–Rammler equation and Alfred equation were 0.75–0.85 and ~ 0.5, respectively. In addition, the packing density for unimodal PSD is generally lower than that for multimodal PSD. In contrast, the average sizes of the mixed samples did not affect the packing status in CWS and the product concentration consistently. With some adjustments, the proposed method can also be used to evaluate the tapped packing density of dry coal powders, with some applicability. [ABSTRACT FROM AUTHOR]

The preparation of hierarchical porous silica aerogels from coal gasification fine slag (CGFS) offers an effective approach to achieving high-value utilization of solid waste and reducing the production cost of solid adsorbent matrix materials. However, the main challenges involve overcoming technical barriers to efficiently and value-added conversion of CGFS into silica aerogels with CO₂ adsorption properties, as well as elucidating the phase transformation mechanisms during the synthesis process. In this study, CGFS was used as the raw material to obtain a silicon-containing precursor through pre-decarbonization (with ash content as high as 99.82 %) and alkali dissolution treatment. A hierarchical porous silica aerogel was then synthesized using an efficient hydrothermal process. The effect of alkali dissolution on silicon extraction and the phase transformation mechanisms were thoroughly discussed, and the leaching mechanism was analyzed through thermodynamic and kinetic models. The results showed that the high leaching rate of silicon was attributed to the presence of a large amount of amorphous SiO₂ in the decarbonized fine slag (DCFS), while the formation of zeolite Na-P1 and hydroxysodalite during the alkali dissolution process affected the efficiency of silicon extraction. Then, the structural formation mechanism and CO₂ adsorption properties of the hierarchical porous silica aerogels were analyzed using N₂ adsorption-desorption and CO₂-TPD. The SiO₂-1-30-0.5 exhibited a high CO₂ adsorption ability of 1.53 mmol g−1, and the CO₂ adsorption capacity maintained 94.78 % of the original value and after 5 adsorption-desorption cycles. [Display omitted] • Hierarchical porous silica aerogels were efficiently synthesized using DCFS. • The phase transformation and silicon leaching mechanism during the alkali dissolution process of DCFS were revealed. • The structural formation mechanism and CO 2 adsorption properties of hierarchical porous silica aerogels were studied. • The sample showed CO 2 adsorption capacities of 1.53 mmol g−1 at 273K. [ABSTRACT FROM AUTHOR]

Coal gasification fine slag (FS) is a by-product of coal gasification with significant potential for resource utilization. However, the low recovery rate of residual carbon greatly restricts its resource utilization and harmless disposal. In this paper, a spiral separator was used to recover FS, followed by the use of oil agglomeration separation technology to enhance the selection of concentrate. The separation mechanism of the oil agglomeration process was analyzed through EDLVO theoretical calculation. Finally, the ecological risk of metal element speciation in the separated products was assessed with Risk Assessment Code (RAC) and the Ratio of Secondary Phase to Primary Phase (RSP). The results showed that by optimizing the separation parameters, efficient separation of residual carbon and ash components could be achieved at the pulp flow of 1.0 m3·s−1 and pulp density of 5%, with the ash content of the obtained concentrate, middlings, and tailings products being 42.11%, 40.45%, and 88.46%, respectively. Concentrates were reselected using oil agglomeration separation technology at the oil dosage of 25% and a stirring time of 15 min, and the ash content of the obtained clean coal and tailings were 18.04% and 93.04%, while the clean coal yield of this grade accounted for 38.48% of the total sample. The EDLVO theory indicated that the emulsified kerosene enhanced the hydrophobicity of the residual carbon particles, increasing the difference in hydrophobicity between the carbon and ash particles, thereby strengthening the recleaning effect of concentrate. The RSP evaluation method confirmed that metal element levels in tailings are within safe limits, which could be used for direct secondary resource utilization. This study provided a theoretical basis and technical guidance for the separation and resource utilization of FS. [ABSTRACT FROM AUTHOR]

Ammonia nitrogen and phenol are typical inorganic and organic pollutants in the coal chemical wastewater, respectively. In this study, the adsorption characteristics of ammonia nitrogen and phenol on lignite were investigated through experimental and molecular dynamics simulations. The results show that the adsorption of ammonia nitrogen was carried out via ion exchange, which was significantly faster than the adsorption of phenol driven by the π–π interaction. In the binary adsorption, the surface electronegativity of lignite decreased with the adsorption of ammonia nitrogen thereby promoting the adsorption of phenol. However, the extent of ammonia nitrogen adsorption was slightly reduced in the presence of phenol. Molecular dynamics simulation results indicated that the adsorption of phenol molecules on the lignite surface was closer than that of ammonium ion. The addition of ammonium ions could enhance the adsorption of phenol molecules on the lignite surface. The simulation results were well consistent with the experimental findings. This study indicates lignite has a promising potential in coal chemical wastewater adsorption pretreatment. [Display omitted] • Lignite adsorption was based on mesopores and oxygen functional groups. • The adsorption rate of NH 4 +-N on lignite was faster than that of phenol. • The adsorption quantity of phenol on lignite was increased by NH 4 +-N. • MD Simulation provided atomic-scale details of adsorption. [ABSTRACT FROM AUTHOR]

Sludge from coal chemical industry is hazardous and difficult to disposal. In this study, a coal chemical sludge was mixed with lignite, coking coal and lean coal to prepare coal-sludge-slurry(CSS) for gasification and combustion. The results showed that the addition of sludge changed CSS from the dilatant fluid to the yield pseudo-plastic fluid. The stability of CSS was observed increasing, while the preparation concentration was decreased at the same viscosity requirement. A combination of BET analysis and EDLVO theory calculation was carried out to study the behavior among particles and water in CSS. Sludge could attract considerable water, increasing the viscosity of slurry. Besides, sludge might connect with coal particles to structure a three-dimensional network which would be destroyed by agitation and then released trapped water, resulting in the pseudo-plasticity of CSS. The network could also prevent the aggregation of particles and improve the stability of slurry. Unlabelled Image • Coal-sludge-slurry were prepared by three coals and sludge from coal liquefaction. • The addition of sludge made slurry more stable as TSI max decreased from 0.93 to 0.24. • Sludge made slurry more pseudo-plastic as fluidity index n reduced from 1.11 to 0.63. • Sludge connected with coal particles to form a network according to EDLVO calculation. [ABSTRACT FROM AUTHOR]

\nHIGHLIGHTSThe resource utilization of coal gasification fine slag (FS) and the harmless treatment of dyeing wastewater are crucial for establishing a zero-emission industrial system and a circular economy. This study used FS as raw material and divided it into two particle sizes through ultrasonic pretreatment enhanced wet sieving. The composite materials were synthesized via an alkaline hydrothermal process from different components in FS was compared, and applied as adsorbents for the removal of methylene blue from printing and dyeing wastewater. Finally, the kinetic and thermodynamic model developed for MB from printing and dyeing wastewater. The maximum adsorption of MB by the composite material prepared from low carbon component (<0.125 mm) could reach more than 180 mg·g−1. The research results have important theoretical and practical value for guiding the high-value utilization of FS and its application in dye wastewater treatment. The alkali-soluble hydrothermal technique synthesized the composites.Methylene blue maximum adsorption capacity of 180 mg·g−1.The composites’ kinetic and thermodynamic adsorption properties on MB were clarified.The reaction mechanisms of different components in FS were elucidated.The alkali-soluble hydrothermal technique synthesized the composites.Methylene blue maximum adsorption capacity of 180 mg·g−1.The composites’ kinetic and thermodynamic adsorption properties on MB were clarified.The reaction mechanisms of different components in FS were elucidated. [ABSTRACT FROM AUTHOR]

Coal gasification fine slag is a solid waste of difficult-to-separate nature. In this study, the residual carbon was enriched from fine slag by conventional flotation. The optimal flotation results in the concentrates yield of 59.01%, the concentrates ash content of 37.64%, and the flotation perfect index of 41.12%, respectively. Under the identical conditions, step release flotation exhibits abnormal results, i.e., the lowest ash content is concentrates 3 (C 3) corresponding to 29.21%. The particle distribution analysis of concentrates 1 (C 1) to concentrates 5 (C 5) and tailings (T) shows that particles of the highest carbon content transfer to C 3 , while dominated by ash are enriched in T. Additionally , the particle structure characteristics (with SEM, BET surface area, BJH pore volume/average pore width, FHH fractal characteristics) demonstrate that the particles differ in pore's volume, average width, and interior smoothness. This concludes that it is the larger pore volume, the wider average pore width, and the smoother pore interior that contributes to the greater amount of diesel adsorption and therefore easier release of carbon-content particles in flotation. Such regularities of particle transfer in flotation and release mechanism manifest the flotation specificities of gasification fine slag, which may provide a scientific reference for effectively enriching residual carbon in coal gasification fine slag. [Display omitted] • Conventional flotation upgrades coal gasification fine slag with η as 41.12%. • Concentrates 3 (C 3) abnormally contains the lowest ash content of 29.21%. • Analysis of particle distribution reveals regularities of particle transfer. • Particle structure study learned the release mechanisms of particles. • Flotation specificities of coal gasification fine slag were clarified. [ABSTRACT FROM AUTHOR]

• The dynamic process of bubble and bubble-coal aggregation were visualized. • Bubble distributions in ultrasonic fields were studied by image processing. • Entrapment and entrainment led to a slight increase of clean coal ash. • The highest clean coal yield and combustible recovery obtained at 100 kHz. Ultrasonic flotation was an effective method to float fine coal. In this study, the effects of the standing waves with different frequencies on ultrasonic flotation were investigated. The dynamic processes of bubble and coal-bubble were revealed by a high-speed camera. The results showed that under the action of Bjerknes force, bubble aggregates were formed within 450 ms and coal bubble aggregates were formed within 20 ms. The bubble aggregates were statistically analyzed by image processing method. The number of aggregates and small bubbles in the ultrasonic field at 100 kHz was greater than those at 80 and 120 kHz. Besides, 100 kHz ultrasonic flotation achieved the highest yields of clean coal (35.89%) and combustible recovery (45.77%). The cavitation bubbles acted as either a "medium" or an "inclusion", entrapping and entraining the coal particles in the flotation pulp. It promoted the aggregation of bubbles with coal particles, so the flotation efficiency was effectively improved in the presence of ultrasonic standing waves. [ABSTRACT FROM AUTHOR]

• Entrained-flow gasification coal fine slag can be upgraded by ultrasonic flotation. • Ultrasonic flotation perfect index (η) is 12.60% higher than conventional flotation. • The ash content of ultrasonic flotation concentrates is as low as 27.11%. • Ultrasonic emulsification improved the stability of bubbles in flotation. Entrained-flow gasification coal fine slag is a low value and difficult-to-separate solid waste. In this work, ultrasonic flotation experiments are adopted to enrich the residual carbon and are compared to conventional flotation. The concentrate yield and concentrate ash content decrease by 9.94% and 16.54%, respectively, with the flotation perfect index 12.60% higher. Scanning electron microscopy/energy-dispersive X-ray spectroscopy and thermogravimetric analysis show that the ultrasonic flotation has a positive effect on the residual carbon enrichment. Furthermore, the wet screening results prove that the ultrasonic flotation has a more significant crushing effect on the entrained-flow gasification coal fine slag particles than conventional flotation, mainly benefitting the flotation of small particles (i.e. 0.15–0 mm size fractions). Moreover, after ultrasonic emulsification, the collector can be dispersed more evenly and the surface tension of the collector-deionized water system is decreased, which is beneficial to improving the selectivity of the collector. In addition, with ultrasonic pretreatment at 180 W for 4 min in pulp and emulsification at 180 W for 20 s in the collector-deionized water system, the bubbles in the froth layer are the smallest and most stable, and the merging of the bubbles becomes less obvious. [ABSTRACT FROM AUTHOR]

A Rh(III)-catalyzed C–H activation-desymmetrization of diazabicycles with o -vinylphenols as an efficient approach to alkenyl-substituted aminocyclopentenes is reported. This protocol represents another classic example for direct C–H activation of terminal alkenes using enol as directing group. The reaction features the ease of the preparation of starting materials, fast and high efficiency, broad substrate scope and 100% atom economy, thus provides a valuable entry to synthesize novel substituted cyclopentenes. [ABSTRACT FROM AUTHOR]

[Display omitted] • CGW from a typical airflow bed was investigated for closed water circulation. • The clarified layer was due to organics while sediment layer was NH 4 + and Ca2+. • CGW components reduced the wettability, Zeta potential and porosity of particles. • Competitive adsorption existed between NNO and organics with benzene ring in CWWS. • Cations reduced the hydrophobic and electrostatic repulsion energies of particles. Coal gasification wastewater (CGW) as a substitute for clean water to prepare coal water slurry, which serves as gasification/combustion feedstock, can simultaneously achieve wastewater management and resource utilization. The purpose of this work was to investigate the effects of internal components (i.e., oils, phenols, nitrogen heterocyclic compounds, and inorganic cations) in CGW on the slurryability and dispersion/aggregation behavior of lignite and their co-slurrying mechanisms through experimental and the extended DLVO (eDLVO) theoretical calculations. Results showed that compared to lignite water slurry (LWS), the maximum solids concentration (ω max) of coal gasification wastewater slurry (CWWS) increased by 0.80%, with a lower pseudo-plasticity. The organic compounds adsorbed competitively on the hydrophobic regions of lignite improved the slurrying capability of CWWS by decreasing the wettability, Zeta potential, roughness and pore structure of the particles. By contrast, the static stability of CWWS decreased, and its kinetic stability index (TSI) increased from 0.23 to 0.33. From the backscattering spectra, dodecane caused the creaming process of the slurry, while the clarification process was attributed to phenol and nitrogen heterocyclic compounds. Inorganic cations, especially NH 4 + and Ca2+, significantly reduced the hydrophilic and negative charges on the particle surface, which were the main unfavorable factors leading to particle aggregation and sedimentation. The eDLVO theoretical calculation results exhibited that inter-particle interaction in CWWS was determined by the hydrophobic energy (E h) and electrostatic energy (E e) and their dropped from 1.79 × 10−16 J and 5.16 × 10−17 J to −4.67 × 10−16 J and 2.59 × 10−17 J respectively. [ABSTRACT FROM AUTHOR]

Separation of Cu impurities from spent lithium-ion batteries (LIBs) before precipitating other valuable metals is critical to improve the quality of final products. Currently, the main process for separating Cu impurity from spent LIBs by extraction and precipitation has the disadvantage of being high cost and complicated process. In this work, the surface characteristics of spent LIBs materials before and after thermal treatment are explored, and the effects of the concentration of ammonium salts, temperature, and pulp density on the leaching of Cu impurity are investigated. The novel process proposed in this work removes Cu impurities from spent LIBs materials using a solution of (NH 4) 2 CO 3 at low concentration. The results suggest that organics on the spent LIBs surface can be effectively removed by heating at a temperature of 505 °C to avoid the influence of organics on the removal of Cu impurities. Furthermore, the results of the leaching experiment demonstrate that (NH 4) 2 CO 3 displays an excellent leaching effect on Cu compared to NH 4 Cl, (NH 4) 2 SO 4 , and NH 4 HCO 3. The leaching efficiency of Cu at the concentration of 0.25 mol/L (NH 4) 2 CO 3 , temperature 80 °C and leaching time of 120 min reaches 99.1%. On the contrary, the leaching efficiencies of Ni, Co, and Mn are <4% on average. The thermodynamic analysis proves the potential for removing Cu impurities from spent LIBs materials using a solution of (NH 4) 2 CO 3 at low concentration. The process lays the foundation for the subsequent hydrometallurgical process to recover other metals. • Proposing a novel method to separate Cu impurity from spent lithium-ion batteries. • Realizing a low leaching efficiency of valuable metals (Ni, Co, Mn). • Evaluation of thermodynamic analysis to separate Cu impurity. • Investigation and analysis of leaching conditions. [ABSTRACT FROM AUTHOR]

• A green acid-leaching process is developed to recover valuable metals. • The application of the reagent regime can greatly reduce environmental pollution. • The acid-leaching mechanism has been preliminarily studied. • Kinetic analysis is performed to better understand the leaching process. The traditional inorganic acid leaching method for recycling spent ternary lithium-ion batteries (NCM) materials presents serious environmental pollution and unsafe problems. In this study, a green leaching process for recovering valuable metals from the spent NCM materials using dl -malic acid as the leaching agent and glucose as the reductant is developed, and systematicalsly investigates the leaching kinetics and interface reaction. The results suggest that the leaching efficiencies of Ni, Co, Mn, and Li reach 90.14 %, 90.58 %, 98.66 %, and 98.53 %, respectively, under the optimal conditions of 1 mol/L dl -malic acid, 0.5 g/g glucose, 90℃ leaching temperature, and 25 g/L pulp density for 120 min. The apparent activation energies for leaching of Ni, Co, Mn, and Li are determined as 55.45, 76.08, 39.42, and 42.09 kJ/mol, respectively, indicating that the surface chemical reaction is the rate-controlling step during this leaching process. This process can be an environmentally friendly alternative method to recover valuable metals from spent NCM. [ABSTRACT FROM AUTHOR]

[Display omitted] • The slurryability of the mixed slurry was facilitated most with the lignite/DCLR mass ratio of 5:5. • The maximum solid concentration of the mixed slurry increased from 41.70 wt% to 53.91 wt%. • The combustion process of the mixed slurry was more concentrated and violent. • The DCLR promoted organic pollutant emissions in the wavenumber range of 1500–500 cm−1. • Except for Pb and Zn, more than 85% of Cr, Cu, and Ni were intercepted in solid residues. Direct coal liquefaction residue (DCLR) as an auxiliary feed material with lignite to prepare coal water slurry (CWS), which is then used as combustion fuels, enables recycle resources of DCLR and diminishes its impact on the surrounding environment. This paper aims to study the slurryability, combustion characteristics, and typical pollutant emissions of the lignite water slurry (LWS), DCLR water slurry (DCLRWS), and lignite-DCLR water slurry (L-DWS). Results showed that the DCLR and lignite were complementary in physicochemical properties for preparing the L-DWSs. The maximum solid concentration (ω max) of the DCLR was 73.19 wt% with poor static stability, whereas that of the LWS was 41.70 wt% with high pseudoplasticity. By contrast, the ω max of the L-DWS-5 prepared from the lignite and DCLR at mass ratio of 5:5 was 53.91 wt% with lower pseudoplasticity and static stability. Meanwhile, combustion experiments confirmed that the introduced DCLR was effective in improving the ignition, burnout, and comprehensive combustion performance of the L-DWS. The Q net, p of the slurrying samples increased from 6.70 MJ/Kg for the LWS to 14.41 MJ/Kg for the L-DWS-5. And the addition of the DCLR exhibited slight influences on the emissions of NOx and SO 2 , but significantly increased HCN and other organic compounds such as C n H m , CO, and NH 3 emissions. Furthermore, except for Pb and Zn, more than 85% Cr, Cu, and Ni were intercepted in solid residues. [ABSTRACT FROM AUTHOR]

To effectively and cleanly handle the direct coal liquefaction residue (DCLR), a two-phase microwave reaction system was designed based on poly-generation lignite technology, that performed both individual pyrolysis and co-pyrolysis, to investigate the effect of microwave co-pyrolysis of lignite with different addition of DCLR on the pyrolysis products characteristics. The experimental results demonstrated the presence of synergism during microwave co-pyrolysis, which enhanced the condensation reaction of different free radicals, and thus increased the char (upgraded lignite, UL) yield by 6.14–10.42%. The DCLR showed excellent catalytic effects as consumable absorbents in terms of heating rate, and char and gas yields, and it eventually converted into high value-added combustible gases (CO, CH 4 , and H 2). Furthermore, when compared to the individual pyrolysis sample and lignite, the co-pyrolysis samples' chemical structures were progressively aromatized, and exhibited significantly lower O/C ratios, re-adsorption moisture content, and reactive groups and available sites. Moreover, the pore structures on the surface for the co-pyrolysis samples were dominated by cracks, blowholes, and open-ended fissures, which gradually decreased as DCLR contents increased. Combustion behavior and kinetic analysis confirmed that microwave co-pyrolysis changed activation energy (E a) distribution of ULs and thus improving their combustion performance. Therefore, microwave co-pyrolysis of lignite with DCLR was an effective and economical approach for clean utilization DCLR and obtaining high-quality lignite fuel. • Combined lignite upgrading and clean utilization DCLR via microwave co-pyrolysis. • Synergistic effects between lignite and DCLR increased char yield by 6.14–10.42%. • The highest thermal effect was obtained when lignite was mixed with 15 wt% DCLR. • The DCLR intensified the chemical structure's evolution while reducing the porosity. • Lignite after co-pyrolysis exhibited difficulty in igniting, but combusted easily. [ABSTRACT FROM AUTHOR]

As the composition of direct coal liquefaction residue (DCLR) is complex and difficult to handle, more importantly its dielectric properties are excellent, it is used as consumable wave-absorbents to enhance the microwave pyrolysis of lignite for slurryability improvement. The effects of the different additions of DCLR on the evolution of pyrolysis products were studied by using gas chromatography, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and low-temperature N 2 adsorption analysis. The results indicated that microwave-assisted pyrolysis with DCLR was a promising method for improving slurryability of lignite and an effective method for utilizing DCLR. The introduced DCLR accelerated the heating rate of the process of microwave upgrading lignite, facilitating the decomposition of active oxygen-containing functional groups and aliphatic hydrocarbons and then their transformation into stable ether groups and aromatic structures. In the meantime, it was converted into gaseous products, mainly composed of H 2 , CO, and CH 4 , and solid products with high quality. Additionally, the cyclization and aromatization of organic structures were improved, as well as the order degree of aromatic systems, especially with 12 wt% of DCLR added. Furthermore, the existing and newly formed structures of micropores and mesopores in the upgraded lignite (UL) were remarkably reduced with the increase of DCLR contents. The re-absorption capacity was dramatically reduced and the slurryability of UL was improved as a result of the changes in chemical properties and pore structures. The maximum solid concentration of lignite water slurry (LWS) increased from 41.73 wt% to 65.42 wt% with lower pseudo-plasticity and static stability. • Direct coal liquefaction residue was used as consumable microwave absorbent. • The absorbent was eventually converted into gases with highly added value. • Infrared and Roman parameters were combined to reflect the char structure. • The absorbent promoted aromatization of organic structure while reduced porosity. • The maximum solid concentration of lignite water slurry reached 65.42 wt%. [ABSTRACT FROM AUTHOR]