Research on the Preparation of Carbon-Negative Backfill Materials via Enhanced Carbon Sequestration Using Coal-Based Solid Waste

To tackle the dual challenges of large-scale disposal of coal-based solid waste and safe backfilling of goafs, while aligning with the "dual carbon" goals and enhancing mining area safety, carbon-negative backfilling technology has emerged as a key research hotspot in the field of green mining. However, it still faces issues such as low carbon sequestration efficiency and difficulty in additive recovery. In this study, two methods (NaOH and glycine leaching) were used to enhance the carbon sequestration capacity of coal-based solid waste, and their performance differences under optimal reaction conditions were systematically compared. The experimental results showed that the carbon sequestration capacity of the NaOH alkali activation group was only 26.96 g/kg, while that of the glycine leaching group reached 78.85 g/kg, which was significantly higher than that of the control group and the alkali activation group. Glycine rapidly captures CO₂ through its amino group to generate an active intermediate (carbamate), which greatly accelerates the absorption and conversion process of CO₂. Meanwhile, relying on its zwitterionic properties, glycine effectively buffers the pH value of the reaction system, inhibits the dissolution of CaCO₃ under acidic conditions, thereby promoting the stable precipitation of carbonates and ensuring the continuous progress of the carbon sequestration process. Detection of heavy metal concentrations in the leachate showed that their contents met national discharge standards. In addition, glycine can be recycled and regenerated during the reaction, which reduces additive consumption and demonstrates good economic viability and environmental compatibility. This study confirms that the glycine leaching method not only significantly improves the carbon sequestration efficiency of coal-based solid waste but also has the advantages of recyclability and environmental friendliness, providing a promising technical pathway for achieving efficient, long-term, and stable carbon sequestration in coal-based solid waste backfill materials.