Long-term leaching characteristics of heavy metals from bauxite tailing slurry-based geopolymer backfill:...

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 Cu²⁺ 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 Pb²⁺ and Cu²⁺ when simulating acid rain leachate. The modified Elovich equation described the leaching kinetics of Cu²⁺ well, and the leaching rate decreased with time. Numerical analysis indicated that Cu²⁺ 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 Pb²⁺ and Cu²⁺ under acidic conditions was explored.The modified Elovich equation effectively describes the leaching kinetics of Cu²⁺.The environmental impact of bauxite tailings slurry-based geopolymers was evaluated.