Simultaneous remediation of heavy metals in mining soil using nZVI-supported attapulgite

Soils in and around mining areas are frequently co-contaminated with heavy metals, posing risks to crop safety and human health. Nano zero-valent iron (nZVI) shows promise for multi-metal stabilization but is hindered by aggregation and oxidation. In this study, nZVI-supported attapulgite (nZVI@A) was synthesized by liquid-phase reduction and evaluated for stabilization of Cd, Cr, Cu, Ni, Pb, and Zn in contaminated mine soil and for reduction of maize metal uptake. Pot trials and stabilization tests were conducted, during which extractable fractions, sequential speciation, soil pH, CEC, EC, and metal concentrations and translocation in maize tissues were measured. Experimental results indicated that the stabilization effect was optimal at an nZVI-to-attapulgite mass ratio of 1:3. Significant reductions in extractable concentrations were observed for all target metals, with decreases in acid-extractable fractions and increases in residual fractions, indicating conversion to more stable forms and reduced bioavailability. Metal accumulation and translocation factors in maize were markedly lowered. The stabilization effect was attributed to synergistic adsorption by attapulgite and nZVI-driven precipitation and redox transformations. NZVI@A is proposed as a promising, potentially scalable in-situ amendment for multi-metal immobilization; field-scale validation and long-term stability assessment are recommended.