High-ash coal, also known as low-grade coal, has becomes a viable alternative in recent years to high-quality coal because available resources have become increasingly scarce due to extensive mining activity. This work aims to provide a comprehensive understanding of the structural characteristics of high-ash coal and construct a plausible molecular structure to elucidate its chemical reactivity in future applications. Its properties were investigated using Solid-state ¹³C nuclear magnetic resonance (¹³C NMR), X-ray photoelectron spectroscopy analysis (XPS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The molecular structure was constructed and validated using Material Studio, LAMMPS Software Package, and MATLAB program. The characterization results revealed that high-ash coal contains 72.15% aromatic carbon, significantly surpassing the percentage of aliphatic carbon (27.85%). The ratio of bridgehead carbon to peripheral aromatic carbon was calculated as 0.67, indicating that the pentacene is the main carbon skeleton form in the high-ash coal structure. Furthermore, oxygen-containing functional groups presented as C=O/O–C–O, C–O, and COO– within the structure along with pyridine and pyrrolic structures. Consequently, the molecular structure comprises pentacene with aliphatic carbon chains, such as methylene, that connect the benzene rings and form a three-dimensional network. The results of a simulated IR spectrum and contact angle simulation aligned with the experimental results, validating the molecular structure of high-ash coal. The chemical formula for the high-ash coal model was determined as C₂₀₃H₁₈₉N₇O₆₁S with a molecular weight of 3734.79.

The increasing global market size of high-energy storage devices due to the boom in electric vehicles and portable electronics has caused the battery industry to produce a lot of waste lithium-ion batteries. The liberation and de-agglomeration of cathode material are the necessary procedures to improve the recycling derived from spent lithium-ion batteries, as well as enabling the direct recycling pathway. In this study, the supercritical (SC) CO₂ was innovatively adapted to enable the recycling of spent lithium-ion batteries (LIBs) based on facilitating the interaction with a binder and dimethyl sulfoxide (DMSO) co-solvent. The results show that the optimum experimental conditions to liberate the cathode particles are processing at a temperature of 70 °C and 80 bar pressure for a duration of 20 min. During the treatment, polyvinylidene fluoride (PVDF) was dissolved in the SC fluid system and collected in the dimethyl sulfoxide (DMSO), as detected by the Fourier Transform Infrared Spectrometer (FTIR). The liberation yield of the cathode from the current collector reaches 96.7% under optimal conditions and thus, the cathode particles are dispersed into smaller fragments. Afterwards, PVDF can be precipitated and reused. In addition, there is no hydrogen fluoride (HF) gas emission due to binder decomposition in the suggested process. The proposed SC-CO₂ and co-solvent system effectively separate the PVDF from Li-ion battery electrodes. Thus, this approach is promising as an alternative pre-treatment method due to its efficiency, relatively low energy consumption, and environmental benign features.

The dynamic migration of mineral particles within spiral separators and its control via structural parameters are not yet fully understood, hindering efficiency improvements. To this end, a set of spiral separators with systematically adjusted structural parameters was designed. Extensive sampling of a 1–0.25 mm coal slurry yielded 120 samples from 6 separators, across 5 turns and 4 radial streams. Sink-float analysis revealed a well-defined three-stage separation mechanism: the roughing stage involves rapid segregation of light and heavy particles, while intermediate-density particles remain widely distributed; the intensified cleaning stage governs the radial migration of intermediate-density particles while simultaneously enriching the high-density and low-density fractions; and the final cleaning stage stabilizes the particle distribution and redirects misplaced particles. The influence of key structural parameters was also quantified: the composite cross-section outperformed cubic parabolic and elliptical profiles, markedly enhancing the separation of high-density and medium-high-density particles from the lighter product; increasing the trough inclination angle significantly promoted the radial inward migration of medium-high-density particles; a reduced pitch-to-diameter ratio effectively concentrated high-density and medium-high-density particles within inner and middle regions. Based on these insights, a “process intensification” strategy was proposed and materialized in a novel spiral separator design featuring stage-optimized, multi-parameter coordination. Performance evaluation demonstrated a separation efficiency of 94.74% under equivalent product quality constraints, a substantial improvement over conventional design. This work provides a fundamental, stage-specific understanding of particle separation dynamics and establishes a practical basis for the advanced design of high-efficiency spiral separation systems.

Fluorapatite is a typical phosphate rock resource. Fluorapatite tends to generate fine mud agglomeration, which induces dehydration challenges owing to its inherently fine particle size and negative surface charge. In this paper, phosphate tailings slurries from a phosphate mine in Hubei Province, China, were selected as the research object, and flocculation–dehydration experiments were conducted using anionic, cationic, and nonionic polyacrylamide (PAM) flocculants. The results show that the maximum settling velocity is 51 mm/s and the moisture content of filter cake is 41.54%, which were obtained when the unit consumption of cationic flocculant with molecular weight 12 million was 1000 g/t. The mechanism of sedimentation and dehydration was studied by infrared spectroscopy and a particle size analyzer. The results showed that polyacrylamide was effectively adsorbed on the mineral surface, and the size of flocs increased significantly. Finally, the mechanism of sedimentation and dehydration was proposed. It has important guiding significance for the efficient solid–liquid separation and water circulation of fluorapatite mineral processing wastewater.