Long-term leaching characteristics of heavy metals from bauxite tailing slurry-based geopolymer backfill: experimental and numerical simulation studies.

This study aimed to evaluate the potential of replacing fly ash (FA) with bauxite tailing (BT) slurry for geopolymer synthesis and investigate the long-term leaching behaviour of BT slurry/FA geopolymers (BFGs) for heavy metal immobilisation. The mechanical properties and heavy metal immobilisation efficiency of BFGs were tested, and numerical simulations were conducted to assess their environmental impact as a backfill material. The results showed that the incorporation of 5 Wt.% BT increased the early compressive strength of the geopolymer without any additional treatment. A small quantity of Cu improved the mechanical strength, while excess heavy metals harmed the geopolymer. Heavy metal immobilisation efficiency decreased with increased heavy metal addition and exceeded 99.9% for Pb and Cu when simulating acid rain leachate. The modified Elovich equation described the leaching kinetics of Cu well, and the leaching rate decreased with time. Numerical analysis indicated that Cu leaching from landfill leachate occurred in three phases, with an initial increase followed by a gradual decrease, stabilisation, and diffusion into the surrounding soil layer. This study provides insight into the material's long-term stability and environmental performance, offering a scientific basis for relevant engineering applications.HighlightsDirect utilisation of unprocessed tailing slurry to synthesise geopolymer.The leaching pattern of Pb and Cu under acidic conditions was explored.The modified Elovich equation effectively describes the leaching kinetics of Cu.The environmental impact of bauxite tailings slurry-based geopolymers was evaluated.