Synergistic conversion of red mud, coal gangue, and Moutai-flavor baijiu wastewater into a plant‑growth‑supporting soil‑like material: mechanisms and optimization

The global challenge of managing industrial solid wastes demands innovative solutions beyond conventional disposal. Herein, we present a "waste-treats-waste" strategy that synergistically converts red mud (RM), coal gangue (CG), and Moutai-flavor baijiu wastewater into a plant-growth-supporting soil-like material. The acidic wastewater provided organic acids and microorganisms for bio-dealkalization, while CG served as a physical scaffold preventing compaction. This co-treatment triggered a geochemical cascade: unstable aluminosilicates (e.g., Katoite) underwent incongruent dissolution, with released ions re-precipitating as thermodynamically stable phases (e.g., Amesite)—a mineral transformation that effectively immobilized heavy metals within crystal lattices under the tested conditions. Leaching concentrations of all metals fell below Chinese regulatory limits (GB/T 14848-2017 and GB 5084-2021). Plant bioassays demonstrated robust germination and sustained growth of Sudan grass and alfalfa, with optimal performance at RM:CG ratios of 8:12 to 4:16. Metagenomic profiling revealed the emergence of a resilient microbial ecosystem dominated by uncultured Acidobacteriaceae, driving organic degradation and nutrient cycling. This work establishes a closed-loop framework transforming hazardous industrial residues into ecologically functionamaterials, offering a scalable pathway for circular economy implementation and ecological restoration.