Study on fluoride leaching regularity of natural minerals in Shendong Mining Area

As coal mining is shifted to the deep in Shendong mining area and fluorine concentration in mine water is increasing, it is of great significance to study the main sources of fluoride for the control of fluoride pollution in mine water. In order to further prove that natural fluorine-containing minerals are the main source of fluorine in mine water, it is necessary to deeply understand the leaching process of natural fluorine-containing minerals in mine water.Take the Shendong mining Area as an example, the water quality change law of mine water at different depths was analyzed, the fluoride content change of rock mining areas at different depths was studied, and the fluoride leaching regularity of natural fluorine-containing minerals in mine water was discussed. The results show that the fluoride concentration in the mine water exceeds the standard value of class III fluoride on the surface, and the proportion of fluorine-containing minerals in natural minerals increases,when the coal mining depth is more than 120 m. Through analyzing the anion and cation components of the mine water, it is believed that the fluoride in the mine water mainly comes from the leaching of fluorine-containing minerals in deep coal mining. Further study on the leaching law of fluorine-containing minerals under different water rock interaction conditions shows that the leaching of fluoride in fluorine-containing minerals can be accelerated by increasing the strength of water rock interaction; When the rock water ratio was increased (more than 1∶50), the fluoride leaching concentration of some fluorine-containing minerals was greater than 1.0 mg/L; Especially under acidic or alkaline conditions, the insoluble fluorides in fluorine-containing minerals were dissolved due to ion exchange and leaching equilibrium mechanism.To sum up, the high fluoride (more than 1.0 mg/L) in mine water was caused by fluoride leaching, because fluoride in natural fluorine-containing minerals is dissolved out under certain water rock interaction conditions. It is an important guidance to accurately control the fluoride leaching of natural minerals under complex geological conditions.