Upcycling Municipal Solid Incineration Fly Ash into Layered Double Hydroxide Nanomaterials: Heavy Metal Immobilization and Environmental Risk Assessment

Municipal solid waste incineration fly ash (MSWI FA) represents a significant environmental challenge due to its high content of toxic heavy metal (HM) and large-scale generation. This study demonstrates the feasibility pathway for converting hazardous MSWI FA into well-crystallized layered double hydroxide nanosheets (LDH-FA). Sodium dimethyl dithiocarbamate (SDD) was incorporated as a chelating stabilizer to enable synergistic HM immobilization during acid leaching and crystallization. High-resolution transmission electron microscopy (HRTEM) confirmed the characteristic two-dimensional nanosheet morphology with interlayer spacings consistent with LDH structures, while elemental mapping revealed homogeneous distribution of Pb and Zn within the nanosheet matrix. SDD dosages higher than 1.0 wt% effectively suppressed HM leaching, and Pb concentrations were controlled below 0.1 mg/L and Zn maintained at minimal levels. BCR sequential extraction analysis further demonstrated that SDD treatment effectively transformed HMs from bioavailable acid-soluble fractions to stable forms. This investigation establishes an innovative approach to MSWI FA resource utilization and provides mechanistic insights into HM stabilization within LDH nanostructures, offering a scientific basis for safer applications of waste-derived nanomaterials.