Formation And Transport Processes Of Contaminants In Coal Gangue

Coal gangue, as the solid waste produced during coal mining, was usually piled up near the coal mining sites without any protection. The coal gangue stored in deep underground maintains geo-chemically stable. However, it will be no longer stable when it is exposed on the surface. Especially during the period of deposit and when the coal gangue was not protected properly, it would be physically and chemically weathered, and the dissolved harmful substances would discharged into the water, soil and air environment through volatilizing and leaching, which in turn may impact to the surrounding environments.The coal gangue was sampled from an abandoned coal mining site, which is located in Shiguai, Baotou, and its chemical and mineral compositions were analyzed. A series lab tests were carried and the lechate at the field site had been mornitered for one year in order to get better understanding on the formation and transport processes of the contaminants in coal gangue. The coal mine solid waste crashed into particles and sieved for the further lab tests, which included (1) batch reaction tests with different particle sizes, ratio between solid and liquid, and pH and (2) saturated and unsaturated column tests. The results showed that particle sizes, ratio between solid and liquid, and pH significantely affected the dissolution processes and inflow rates stronly affacted the releasing load of contaminants in the outlet. PHREEQC was applied to model the formation and reactive transport processes of the contaminants that occurred within the test columns. The modelled results well represented the element concentrations meathered in the outlet. This indicated that PHREEQC could interpretat the characteristics of the multiple mineral dissolution, hydro-geochemical reaction, and transport processes.