Separations

Fine gangue contamination limits the flotation upgrading of coking coal middlings, yet the relative roles of water entrainment and slime coating remain unclear for different gangue minerals. This study investigated the contamination behaviors of quartz, kaolinite, and calcite through flotation tests, bubble-particle attachment measurements, zeta potential analysis, DLVO calculations, SEM-EDS observations, foam drainage and settling tests. Results showed that the addition of gangue minerals reduced combustible recovery, and the combustible recovery decreased from 91.68% for low-ash coal to 86.87%, 84.77%, and 82.55% for the coal–quartz, coal–kaolinite, and coal–calcite systems, respectively. Quartz exhibited limited coal–gangue association and a stronger tendency toward water entrainment, whereas calcite showed more pronounced surface attachment, consistent with slime-coating contamination. Kaolinite displayed intermediate behavior, with particle association that could not be fully explained by classical DLVO calculations. These findings demonstrated that gangue contamination depended on the combined effects of interfacial interactions, particle association, and water-mediated transport. The integrated approach provides a basis for identifying mineral-specific contamination tendencies and developing targeted strategies to improve flotation selectivity.

Regeneration of catalysts through arsenic and alkaline rare earth removal can not only solve the environmental problems caused by the stacking of deactivated catalysts and arsenic pollution, but also reduce the economic investment required to produce new catalysts. After analyzing the structure and composition of the spent V₂O₅–WO₃/TiO₂ catalysts obtained from a power factory, their existence, form and content were determined for As and Ba. NaClO was used as both an oxidant and a base source in leaching As. It first oxidizes the highly toxic and adsorbed stable As(III) into the more water-soluble As(V). Meanwhile, the OH⁻ produced by hydrolysis provides an alkaline environment, promoting the conversion of As⁵⁺ to soluble AsO₄³⁻ and facilitating the desorption and dissolution of As from the catalyst. Taking into account the removal rate of arsenic and the loss of active ingredients, the optimal process conditions were determined. The BaSO₄ was removed using the EDTA complexation method and the optimal conditions were determined. The elution and regeneration process not only removed arsenic but also effectively unblocked the pore structure of the catalyst. The redox capacity of the regenerated catalyst was significantly enhanced, and the number and strength of acid sites and the denitrification performance were also effectively restored.

The volatile aroma of Osmanthus fragrans flowers is governed by both cultivar background and extraction technique, yet their relative contributions remain unquantified. Here, four representative cultivars from Xianning, China—‘Boye Yingui’ (BYYG), ‘Daye Jingui’ (DYJG), ‘Xiaoye Dangui’ (XYDG), and ‘Mantiaohong’ (MTH)—were processed in parallel by solid-phase microextraction (SPME), solvent extraction of intact flowers (IF), solvent extraction of ground flowers (GF), and rotary distillation (RD), and the resulting profiles were analyzed by GC-MS combined with PCA, Venn analysis, and ANOVA. In total, 78 volatile compounds in seven chemical classes were detected across the 16 cultivar–method combinations. Variance partitioning showed that the extraction method, rather than the cultivar, was the dominant source of variation (77.2–79.2% of total variance). RD preferentially enriched alcohols (73.9–78.6%) and esters (up to 19.8%) but largely eliminated aldehydes, alkenes, and alkanes; SPME produced the highest relative proportions of ketones and alkenes in its volatile profile; and GF delivered the broadest compound coverage and the most unique compounds in three of the four cultivars. DYJG accumulated the most linalool (10.6 ± 6.4%), whereas MTH was distinguished by γ-decalactone (11.2 ± 6.6%, reaching 19.3% under RD). A target-component-oriented method–cultivar matching strategy is proposed for the efficient utilization of O. fragrans aroma resources.