Mechanism of modified plant fibers in enzyme-induced carbonate precipitation for bio-solidification of fine tailings

Enzyme-induced carbonate precipitation (EICP) has emerged as a sustainable alternative to conventional methods for stabilizing the heavy-metal-rich tailings due to its environmental friendliness. Nevertheless, its mineral precipitation efficiency and reinforcement performance in the bio-solidification of fine-grained tailings remain limited, primarily owing to the lack of effective nucleation drivers and the inherent brittleness of the precipitates. In this study, a novel mineralization strategy was proposed, in which mineralization-modified straw fibers (MSF) were synergized with EICP to achieve the green bio-solidification of fine graphite tailings (GT). The results showed that the MSF-EICP treatment significantly enhanced the mechanical strength, heavy-metal immobilization, and mineral precipitation efficiency of GT compared with conventional EICP. At an MSF dosage of 1.5%, the unconfined compressive strength, splitting tensile strength, and CaCO₃ yield of GT were increased by 73.81%, 239.06%, and 60.78%, respectively, while the strength ratio was reduced by 48.71%. The leachate pH of MSF-EICP-treated GT stabilized between 7.91 and 8.14, with heavy-metal immobilization efficiencies reaching 89.69~100%. Mechanistically, MSF-EICP promoted the formation and uniform distribution of carbonates through the synergistic effects of mineralization regulation and interfacial nucleation induction, while the construction of a three-dimensional bio-cementation network reshaped the pore structure of GT, thereby markedly improving mineral deposition efficiency and structural stability. Overall, this study overcomes the limitations of conventional biomineralization technologies in GT treatment and provides new insights into the multi-scale bio-solidification of GT using modified EICP.