Sustainable beneficiation of high-ash Indian coal: phytochemical-facilitated demineralization and energy enhancement

Improving the quality of high-ash Indian coal remains a significant challenge for enhancing energy efficiency and reducing environmental impact. This study introduces a sustainable beneficiation approach utilizing aqueous stem extracts of Myristica malabarica as a green, plant-derived alternative to conventional chemical leaching agents. Phytochemical characterization confirmed the presence of polyphenols, flavonoids, and chalcones, compounds recognized for their potent chelating and surface-active properties. Bio-extract treatment effectively reduced coal ash content from 35.12% to 31.05%, representing a relative reduction of 11.6%. This demineralization led to significant enrichment in fixed carbon and a substantial increase in gross calorific value (GCV) from 4403 to 4958 kcal/kg. Structural analyses via XRD and FTIR indicated the partial degradation of key crystalline mineral phases, including quartz and kaolinite. SEM-EDS observations corroborated these findings, revealing notable surface decontamination and a significant decrease in the elemental concentrations of silicon and aluminum. These improvements are attributed to the synergistic effects of metal chelation and redox-mediated interactions between the phytochemical constituents and the coal mineral matrix.