• • PFMBC at 5% dosage reduced bioavailable Cd, Pb, and Zn by 73.44%, 90.10%, and 69.33% after 60 days, respectively, outperforming BC and FMBC, demonstrating a breakthrough in Zn stabilization in multi-metal contaminated soils.
• • The synergistic combination of phosphate, iron-manganese oxides, and biochar promotes the transformation of heavy metals from acid-soluble and reducible fractions to residual fractions, enhancing long-term stability and reducing environmental risk.
• • PFMBC significantly improved soil physicochemical properties, with pH adjustment and increased surface functional groups (FTIR) and formation of stable mineral phases (XRD), providing structural support for metal immobilization.
• • The material addresses the bottleneck of Zn fixation in co-contaminated systems by mitigating competitive adsorption between Cd and Zn and providing multiple binding mechanisms, offering a cost-effective and environmentally compatible solution for field-scale remediation.