Study on the Pb2+ Consolidation Mechanism of Gangue-Based Cemented Backfill

Coal mining produces a large amount of gangue that pollutes the environment, causing surface subsidence and damaging the groundwater systems. Backfill mining is an effective technology used to solve this problem, but there is a risk of polluting the groundwater due to the heavy metal ions present in the backfill material. Pb2+ has been determined to be a representative element because of its existence in coal gangue samples but not in fly ash. The risk of gangue-based cemented backfill causing groundwater pollution can be evaluated by studying the Pb2+ leaching from gangue under various conditions. When comparing the leaching amounts of Pb2+ from the coal gangue particles and the test blocks, it was found that cement filling has an obvious consolidation effect on the Pb2+ in coal gangue. The above process shows that cemented backfill has an obvious consolidation effect on the Pb2+ in gangue. The results of the theoretical analysis, X-ray, and SEM show that the consolidation mechanism can be divided into four modes: physical encapsulation, ion exchange, ion adsorption, and chemical reaction. The results are of great significance for revealing the leaching mechanism of the heavy metals in coal gangue, assessing the risk of heavy metal pollution in groundwater via gangue-cemented backfill, and improving the mining theory of the gangue-cemented filling and groundwater protection.