Abstract <p>To explore the impact of mine water composition on the spontaneous combustion properties of coal samples, the physicochemical characteristics of untreated raw coal (RC) and coal samples soaked in mine water (SC) were comparatively analyzed. The findings indicate that the chemical components of mine water significantly influence the spontaneous combustion behavior of coal. Electron microscopy experiments demonstrated noticeable changes in the surface morphology and pore structures of SC, leading to an increased oxidation rate and a heightened risk of spontaneous combustion. Energy dispersive spectroscopy (EDS) analysis revealed a decrease in carbon content alongside an increase in oxygen and sulfur concentrations on the SC surface, further facilitating the spontaneous combustion process. Simultaneous thermal analysis experiments indicated that characteristic temperatures, such as pyrolysis and ignition points of SC, were generally lower than those of RC, suggesting a stronger propensity for spontaneous combustion. ¹³C NMR results showed a higher content of oxygen-containing functional groups in SC compared to RC, although the aromatic carbon content remained similar. A comprehensive evaluation suggests that SC exhibits an enhanced tendency towards spontaneous combustion. Additionally, programmed temperature experiments revealed that temperatures at which SC generated spontaneous combustion indicator gases were consistently lower than those observed for RC, reinforcing the conclusion that SC possesses a higher spontaneous combustion tendency. In summary, soaking coal samples in mine water substantially increases their spontaneous combustion risk by modifying their physicochemical properties.</p>