Synthesis of tailing slurry-based geopolymers for the highly efficient immobilization of heavy metals: Behavior and mechanism

This study utilized an untreated bauxite tailing (BT) slurry to synthesize geopolymers to reduce material drying and calcination costs and achieve resource utilization of the BT slurry. The effects of BT content, liquid-to-solid (L/S) ratio, sodium silicate modulus, and concentration on compressive strength were analyzed, along with the geopolymer`s resistance to water-induced erosion and its ability to immobilize Pb ²⁺ and Cu ²⁺ . The results demonstrated that increasing BT content resulted in a decrease in compressive strength, but the complete substitution of fly ash (FA) with BT slurry resulted in a 28 d compressive strength of 4.89 MPa. Although BT slurry-based geopolymers (BTGs) had good resistance to water-induced in stability because of their dense structure, the addition of heavy metals weakened their mechanical strength. Leaching tests showed that the BTGs had an immobilization efficiency of greater than 96.5% for Pb ²⁺ and between 93% and 96% for Cu ²⁺ in landfill leachate, and all immobilization efficiencies for heavy metals in acid rain leachate exceeded 99.9%. The outcomes of characterization studies revealed that Pb ²⁺ and Cu ²⁺ engaged in geopolymerization and immobilized through the chemical bonding of T (Si, Al) − O − M (Pb, Cu) and physical sealing. This study presents a low-energy-consumption technology that effectively enhances the utilization of BT slurry. In situ material extraction can be used to remediate contaminated soils in tailing pond areas.