Experimental Study on the Purification Mechanism of Mine Water by Coal Gangue

Coal mining has caused groundwater pollution and loss. Using a mined area as a water storage space for storing and purifying mine water is a low-cost environmentally friendly mining method. In this study, static and dynamic adsorption experiments on the ions in mine water were carried out using the roof rocks from the Lingxin coal mine. The sample analysis results show that the main chemical composition of the roof is mainly SiO2 and Al2O3. The water chemistry type of the mine water is SO4-HCO3-Cl-Na type, with an average mineralization of about 4000 mg/L. The experimental results show that gangue can stabilize the pH value of mine water with different pH values between 7.5 and 8.5. In the acidic and alkaline environment, the degree of void space increases the adsorption capacity of the gangue, in which the adsorption rate of gangue is between 3% and 5%. The calcium ion reduction rate reaches 75% in static leaching and 70% in dynamic leaching conditions. Medium-grained coarse sandstone has a stronger adsorption capacity than muddy siltstone. The results from this study can support further research on using gangue for water purification purposes in mines, simultaneously reducing the harmful accumulation of gangue and promoting the recycling of highly mineralized water.