Study on release law and biological toxicity of heavy metals in coal gangue leaching solution

In order to get a comprehensive understanding of coal gangue in the pile in the process of coal gangue release law and environmental hazards, an acidic coal gangue stack in Guizhou was taken as the research object, using static leaching, dynamic leaching with different solid-liquid ratio and different particle size under the condition of coal gangue releasing regularity of heavy metals in the leaching solution was studied, at the same time, and the luminosity of dynamic leaching solution of coal gangue with different particle sizes was measured by Photobacterium phosphoreum T3 method to analyze its biological toxicity. The results show that: ① During static leaching: the larger the solid-liquid ratio, the smaller the pH value of the static leaching solution, and the larger the contents of sulfate, Fe and Mn elements, while the dissolution amount of heavy metals does not change significantly with the increase of the solid-liquid ratio. For coal gangue with different particle sizes, under the same leaching conditions, the concentration of heavy metals dissolved in the medium particle size is relatively large; ② During dynamic leaching, with the increase of leaching time, the pH value of the leaching solution gradually increases, and the leaching concentration of sulfate and heavy metals gradually decreases. The cumulative amount of heavy metals released by gangue with different particle sizes is different. The relationship between the cumulative heavy metal release amount and time of coal gangue with different particle sizes was fitted twice, and it was found that the release rate of heavy metals is not affected by particle sizes. The release rate of heavy metals is the fastest at the initial leaching stage, and then slows down gradually until it becomes stable; ③ The relative luminosity of undiluted eluviate solution is 0, showing a highly toxic state.After being diluted 100 times, the relative luminescence intensities of different particle sizes are in the range of 56%—65%. The lowest luminescence rate of coal gangue with medium particle size is 56, so its biological toxicity is the highest. The linear fitting results of different heavy metal concentrations and luminescence showed that the six heavy metals studied all had inhibitory effects on luminescence bacteria, among which Zn, Pb and Mn played the main inhibitory role.