Remediation of multiple heavy metals contaminated soils by Mn and Fe-added solid wastes: Effect and mechanisms

Soil contaminated by As, Sb, Cd, and Pb has aroused worldwide concern due to their environmental hazards. The application of solid wastes-based stabilizers for simultaneous metallic cations and anions stabilization is still challenging. Herein, the newly Fe-Mn and C-Mn stabilizer was designed via the mechanical mixing of steel slag/ coal fly ash, FeSO4 and natural pyrolusite has been reported. The Mn and Fe addition reduced the extraction content of heavy metals in soil, especially for As. The bioavailability of As, Sb, Cd and Pb was reduced 85.04 %/85.16 %, 67.57 %/64.78 %, 39.15 %/35.12 %, and 51.19 %/23.76 % after 5% addition of Fe-Mn and C-Mn stabilizers for 90 days, respectively. In addition, the migration of heavy metals was suppressed by promoting the transformation of mobile fractions (F1As/Sb + F2As/Sb and B1Cd/Pb + B2Cd/Pb) to residual state (F5As/Sb and B4Cd/ Pb). The application of Fe-Mn and C-Mn stabilizers slightly changed soil properties. The Mn addition promoted the As(III) oxidation, and the generation of more Fe(III) (hydro)oxides, enhancing the adsorption, complexation, and coprecipitation of As, Sb, Cd and Pb. In addition, the reduction of both As(V) and Fe(III) was delayed. This study provides a new strategy for the synergistic use of solid wastes and natural minerals for the remediation of multiple heavy metals-contaminated soils in mining areas.