Mechanism and experimental study on the solidification of salt ions in mine water by alkali-activated coal-based solid waste cementitious material

This study summarizes the mechanisms of alkali-activated materials in solidifying salt ions in mine water with high TDS and the research progress of novel technologies, while also analyzing relevant domestic application scenarios and key technical challenges.Alkali-activated cementitious backfill materials were prepared using mine water with high TDS, coal gangue, fly ash, ordinary portland cement, and additives.By investigating the content of different additives, the compressive strength of test specimens and the ion concentration in the soaking solution were measured.The results indicated that the test specimens with the addition of 4.8% industrial water glass demonstrated the optimal compressive strength.Based on this, calcium oxide was additionally introduced as an additive, while high-temperature pretreatment was applied to fly ash.Ultimately, the solidification rate of chloride ions reached 87.54%, and the solidification rate of sulfate ions was greater than or equal to 98.72%.Experimental results demonstrate that alkali-activated materials based on coal-based solid waste can effectively solidify salt ions in mine water.Under coexisting conditions of Cl^- and SO₄^2-, the priority of ion solidification must be considered, and aluminum sources should be rationally allocated through mix proportion optimization.Pretreatment of fly ash is an effective method to enhance the performance of alkali-activated materials, significantly improving ion solidification efficiency and resource utilization rates.For mine water with varying water quality characteristics, customized formulation schemes should be developed and combined with pretreatment processes to achieve efficient solidification and resource utilization of salt ions.