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Spent carbon cathode (SCC) is one of the major hazardous solid wastes generated during the overhaul of electrolysis cells in the aluminum production process. SCC is not only rich in carbon resources but also contains soluble fluoride and cyanide, which gives it both recycling value and significant leaching toxicity. In this study, we explore the properties, emissions, and disposal strategies for SCC. Pyrometallurgy involves processes such as vacuum distillation, molten salt roasting, and high-temperature roasting. Hydrometallurgy describes various methods used to separate valuable components from leachate and prepare products. Collaborative disposal plays a positive role in treating SCC alongside other solid wastes. High-value utilization provides an approach to make full use of high-purity carbon-based materials. Finally, we analyze and summarize future prospects for the disposal of SCC. This study aims to contribute to the large-scale treatment and resource utilization of SCC while promoting circular economy principles and green development initiatives. [ABSTRACT FROM AUTHOR]

Ni‐rich cathode material possesses a considerable theoretical capacity, yet achieving their full capacity potential remains challenging. Elevating its operation voltage is an effective approach, while the stability of Ni‐rich cathode material is relatively poor, which is limited by Li+/Ni2+ mixing. Herein, a strategy of cation/anion co‐doping is proposed for single‐crystal ultrahigh‐nickel cathode LiNi0.92Co0.04Mn0.04O2 operated at 4.5 V. The enhancement mechanism is explicitly revealed by in situ/ex situ tests and theory calculations. Specifically, Mo6+ and F− are introduced to construct an appropriate Li+/Ni2+ antisite defects structure at the particle surface, which can maintain the low‐defect Li+ layered channel inside the bulk simultaneously, inducing a stable access portal for Li+ transport from the cathode/electrolyte interface. More importantly, the Li+/Ni2+ antisite passivation layer on the surface can uphold the stability of Li‐layer and optimize the reactive behavior of Ni2+, thus boosting the interfacial stability and reducing the lattice mismatch. As a result, it can achieve high capacity (204 mAh g−1 at 1 C) and stable retention during long‐term high‐voltage measurements both in half‐cell (87.1% after 200 cycles) and full‐cell (91.9% after 400 cycles). This facile strategy provides a feasible technical reference for further exploiting the ultrahigh‐capacity of Ni‐rich cathode for commercial application. [ABSTRACT FROM AUTHOR]

Baking is the most costly and critical process in anode preparation, and the study from the microscopic scale is conducive to the optimisation of anode baking process. In this research, a hybrid simulation method of reactive force field molecular dynamics (ReaxFF-MD) and force-biased Monte Carlo (fbMC) was proposed to understand the interaction mechanism between coal tar pitch (CTP) and calcined petroleum coke (CPC) during kneading and baking processes, and to explore the optimal ratio of CTP from the molecular scale. Results showed that the CTP content of 14 wt.% was beneficial for anode production. The mechanism of anode coking behaviour at high temperatures was also analyzed. The carbonisation of CTP during high-temperature baking broke the carbon rings and formed straight chains, exposing active carbon atoms that can bond with the remaining layers. As the high-temperature simulation progresses, the carbon chains at the bonding sites became increasingly cyclized and aromatised, which made the layered structure of the baked block similar to that of graphite. The generation of various volatile hydrocarbons during the baking process was observed, namely CH4, C2H4, C2H2, C2H6, and C3H6. This work provides theoretical basis for process optimisation. [ABSTRACT FROM AUTHOR]

High-sulfur petroleum coke (petcoke) is generally used as fuel in industries, but the S and N in petcoke will damage the environment during the combustion process. Gasification of petcoke could reduce pollution from S/N-containing compounds. Supercritical water gasification (SCWG) is a new direction with good potential because of its high activity and accelerated reaction characteristics. This work used the reactive molecular dynamics (ReaxFF) simulation to explore the removal and conversion mechanisms of S and N during the SCWG of petcoke. The simulation results showed increasing the pressure and temperature could improve the desulfurization speed. S removal began with the conversion of thiophene-S into C1–4S (mainly C2S) or COS, followed by the conversion into H1–2S in the presence of a large number of hydrogen atoms. The removal of N began with the conversion of pyrrole/pyridine-N into C1–3N(mainly CN). Then, CHON and CON were successively formed. The behaviour of S/N in SCWG could be summarised as follows: thiophene-S → CxS + H → HS + H → H2S, thiophene-S → CxOS + H → CHOS, pyrrole/pyridine-N → CxN/HCxN → CN → CHON → CON, H2N → HON. [ABSTRACT FROM AUTHOR]

Nano-Fe2O3/C composites are widely used in the electrochemical energy storage field. Preparing nano-Fe2O3/C composites via graphitising the amorphous carbon inserting nano-Fe2O3 particles is potential if the influence mechanism of nano-Fe2O3 on the graphitisation of amorphous carbon is explored in-depth. Here, an amorphous carbon model (a-C model) and a nano-Fe2O3-inserting model (C\Fe2O3 model) were built via the liquid-quench method, and the reaction of Fe2O3 and C during graphitisation was explored via the reactive force field (ReaxFF) simulation. The results showed that nano-Fe2O3 could inhibit the graphitisation of amorphous carbon, and the mechanism was revealed. The Fe2O3 molecules collided with the aromatic carbon layer because of the thermal motion, which caused the breaking of the carbon layer and the generation of CO2 and Fe. Certain Fe reduced from Fe2O3 destroyed the aromatic carbon layers by the strong affinity between Fe and C atoms and generated intercalation compounds (FeCx). Furthermore, the regularisation and stacking of large carbon layers were impeded. Thus, the graphitisation of amorphous carbon was inhibited. [ABSTRACT FROM AUTHOR]

Fresh activated carbon (FAC) was oxidised by nitric acid and then the silane coupling agent was grafted onto the surface of FAC under ultrasonic conditions to obtain modified activated carbon (MAC). The chemical oxygen demand was used as the main evaluation index in the wastewater. The effects of benzene, aniline, 2‐mercaptobenzothiazole and methylene blue on the adsorption mechanism and performance of FAC prior and postmodification were investigated by different adsorption models. All of them fitted the Langmuir monomolecular adsorption model. The adsorption capacity of MAC was 1.07, 1.12, 1.56 and 0.62 times that of FAC, respectively, which had a better adsorption effect on hydrophobic organic compounds. The maximum adsorption capacity increased due to the existence of competitive adsorption in multicomponent absorption. Texture properties of activated carbon were characterised by scanning electron microscopy, Fourier Transform‐infrared and Brunauer–Emmett–Teller theory, which show that the surface morphology became spongy, and that Si–O–C and Si–O infrared peaks appeared. In addition to the mesopore volume, the specific surface area, pore volume and micropore volume decreased slightly after the modification. [ABSTRACT FROM AUTHOR]

Structural features of a green Qingdao petroleum coke (produced at ∼ 500 °C) were investigated by image analysis of high-resolution transmission electron micrographs, XRD, and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). The fringe length distribution was comprised mostly of fringes <20 Å, with a peak at 5–7 Å. The MALDI-TOF MS data also indicated an abundance of low molecular weight material 250–300 Da. The coke had considerable preferential orientation within the field of view of the micrograph. However, the degree of ordering was poor with fringe stacking occurring for ∼20% for the fringes, with a mean of 2.11 fringes. XRD also indicated low ordering as expected for a lower quality, low temperature coke. The poor nanostructure-level order was a result of small fringe lengths, with curvature (present in 42% of the fringe) likely contributing. It is thus a partially ordered system, with order varying over length scales. An image-guided construction strategy capable of controlling the degree of order (utilizing Fringe3D and Vol3D) was used to construct an atomistic structural representation (C 3717 H 1830 N 54 O 134 S 109 ) incorporating many experimental parameters. The structure was comprised of preferentially orientated molecules, but with the observed limited stacking, incorporating both curvature frequency and extent. [ABSTRACT FROM AUTHOR]

Spent carbon cathode (SCC), a hazardous solid waste discharged from the aluminum electrolysis industry, has a serious environmental pollution risk. This study aims to explore an environmental friendly process for dissociating toxic substances and recovering valuable components from SCC. Parameters of molten salt-assisted roasting and water leaching were optimized. A possible dissociation mechanism of toxic substances was proposed. Results showed that 99.12% of cyanide was decomposed and 96.63% of fluoride was leached under optimal conditions. The recovery route of fluoride was designed according to the solution equilibrium chemical calculation and the difference in solubility and particle size between the recovered products. Exhaust gas with a high concentration of CO and CO 2 was used for the carbonation of the leaching solution to recover cryolite. Effects of reaction conditions on precipitation mass and phase composition of recovered cryolite were investigated in detail. Characterization results indicated that the crystallinity and particle size of cryolite recovered under optimal conditions were extremely similar to those of commercial products. Finally, NaF and Na 2 CO 3 were separated and recovered via evaporative crystallization combined with selective filtration. This proposed process with circular economy and green chemistry characteristics is expected to recover valuable components while minimizing environmental hazards of SCC. ga1 • 99.12% of cyanide was decomposed and 96.63% of fluoride was leached via treatment. • Graphite carbon, Na 3 AlF 6 and NaF were recovered from spent carbon cathode (SCC). • Exhaust gas was successfully used to recover cryolite from the leaching solution. • Sodium carbonate as a reactant can be recovered and recycled. • A low-pollution emission and circular economy process for SCC was proposed. [ABSTRACT FROM AUTHOR]

• More than 95% of fluorine was separated from spent cathode carbon (SCC). • Mechanical activation significantly enhanced the alkali fusion treatment of SCC. • Simultaneous conversion of multiple fluorides was achieved under acid-free conditions. • Non-toxic and high-quality graphite carbon was separated from SCC. Spent cathode carbon (SCC) is the largest and most inevitable hazardous solid waste continuously discharged from the aluminum electrolysis industry. In this study, mechanical activation was used to assist alkali fusion treatment in dissociating toxic substances and recovering graphite carbon from SCC. The effect of mechanical activation (i.e., milling speed, ball-to-material mass ratio, and milling time) on the alkali fusion treatment was investigated. Its effect on the physicochemical properties of SCC–Na 2 CO 3 mixtures was also analyzed through particle size distribution, Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy, X–ray diffraction and thermogravimetric analysis–differential scanning calorimetry. Results showed that mechanical activation enhanced the alkali fusion treatment by improving the physical separation of fluoride, the mixing uniformity and reaction contact area of SCC and Na 2 CO 3 , and promoting the conversion of Na 2 CO 3 to Na 2 O. The formation of agglomerates was the main reason that the carbon content of recovered graphite carbon and the fluoride ion leaching rate increased initially then decreased with the increment in mechanical activation conditions. Under optimal mechanical activation conditions, the carbon content of recovered graphite carbon and the fluoride ion leaching rate increased from 89.35% and 76.50% (non-activated sample) to 93.93% and 95.02%, respectively, indicating that mechanical activation assisted alkali fusion treatment effectively enhanced the separation efficiency of fluoride and graphite carbon. In addition, thermodynamic analysis of the alkali fusion treatment and characterization of recovered graphite carbon (under the optimal mechanical activation conditions) were performed. Results demonstrated that the simultaneous conversion of multiple fluorides (i.e., Na 3 AlF 6 and CaF 2) and oxidative decomposition of cyanide in SCC can be achieved via mechanical activation assisted alkali fusion treatment. These findings indicate that mechanical activation–assisted alkali fusion treatment is a promising method for the detoxification and utilization of SCC. [ABSTRACT FROM AUTHOR]

Coal gangue is regarded as a potential source of aluminum and silica. In this work, acid leaching behaviors of aluminum, iron, and silica in coal gangue were investigated using hydrochloric acid as leaching agent. Chemical and mineralogical compositions of coal gangue and the leached residue were determined by X-ray diffraction (XRD), X-ray fluorescence, and Fourier transform infrared spectroscopy. XRD results indicated that kaolinite and boehmite were the predominant minerals in coal gangue. During elevated temperature acid leaching, mineral phases gradually decomposed, and aluminum and iron ions were dissolved in the acid leaching solution. However, the carbonaceous material and the product of silica were not dissolved in acid and were abundant in leached residue. The extraction efficiency of Al and Fe from coal gangue depended on coal gangue size, liquid–solid ratio, temperature and leaching time. Extraction efficiency of Al and Fe increased with increased liquid–solid ratio, temperature, and leaching time. Under the same conditions, SiO 2 content in the ash of leached residue also increased. The optimum technological conditions for aluminum and iron extraction were obtained with a coal gangue size of 74 μm at a liquid–solid ratio of 3:1 to react at 180 °C for 4 h. After evaporation and crystallization, selective precipitation by adding sodium hydroxide solution, carbon decomposition, and calcination, alumina with a purity of 98.70% was prepared from acid leaching solution. Finally, a suitable amount of low ash anthracite was introduced to the leached residue, and the product of SiC was produced by carbon thermal reduction method. The product had a yield and purity of 72.72% and 76.01%, respectively. [ABSTRACT FROM AUTHOR]

Anthracite graphitization was catalyzed by reduced iron particles, where iron was introduced in the form of Fe 2 O 3 , reduced during the carbothermal reaction. This graphite as an alternative solution for the lithium-ion battery anode material, and the precursor of the anode material was obtained. The degree of graphitization of synthetic graphite regulated via changing the amount of Fe 2 O 3 and catalytic temperature. Graphite with the graphitization degree of 96.51% was obtained under the conditions of the catalytic temperature of 2400 °C, Fe 2 O 3 content of 20%. HRTEM of graphite after Fe-catalyzed graphitization revealed that the graphite layer spacing gradually approached the ideal graphite. Molecular dynamics (MD) provides significant insight into the mechanism of Fe-catalyzed graphitization at the molecular level. The mechanism of Fe-catalyzed graphitization was inevitably related to the formation and breakage of Fe–C bonds. With the formation and breakage of Fe–C and C–C bonds, a regular aromatic 6-membered ring was finally formed due to the strong bonding between Fe and C. Fe promoted the integration of irregular 5- and 7-membered rings into two regular aromatic 6-membered rings. These two processes were continued in the process of catalytic graphitization. This result provided MD support to explore the mechanism of Fe-catalyzed graphitization. [Display omitted] • An alternative anode material is produced by catalytic graphitization of coal via Fe. • Graphite with graphitization degree of 96.51% was obtained. • MD provided significant insight into the catalytic mechanism at the molecular level. • The catalytic mechanism of Fe on graphitization is investigated via the ReaxFF. • Two mechanisms explained the exact mechanism of Fe2O3 catalyzing anthracite. [ABSTRACT FROM AUTHOR]

• A complex and largest scale anthracite coal representation (C 115925 H 42127 O 892 N 764 S 919) constructed. • Coal model captures, organization (stacking and degree of orientation), molecule curvature, heteroatom functionality, and much of the micropore size distribution. • A wide variety of chemical and physical parameters were consistent with experimental data. A large-scale (C 115925 H 42127 O 892 N 764 S 919) atomistic representation of Fenghuangshan anthracite was constructed using an image-guided approach informed by high-resolution transmission electron (HRTEM) micrographs. Additional structural information was obtained from solid state 13C NMR, XRD, laser desorption ionization mass spectra (LDIMS), XPS, and gas adsorption. The structure captures the crystalline characteristics, aromaticity, organization (stacking and degree of orientation), molecule curvature, heteroatom functionality, and much of the micropore size distribution. Construction used Fringe3D and Vol3D scripts to generate slice and volumetric representations with others added heteroatoms. Curvature in the aromatic components was generated manually by adjusting 5- and 7-membered rings frequency and placement. The micropore size distribution was included by incorporating additional pores to supplement the inherent porosity created between structural components. The use of flattened pores also demonstrated a measure of control over pore shapes and captured the coalification induced pore orientation within anthracite coal. Cross-linking is currently omitted however as the frequency and placement are unknown and an automated appropriate cross-linking approach while retaining orientation and stacking is not yet available. [ABSTRACT FROM AUTHOR]