Evaluating the remediation potential of MgFe2O4-montmorillonite and its co-application with biochar on heavy metal-contaminated soils

Abstract

In this work, a novel and efficient magnesium ferrite-modified montmorillonite (MgFe₂O₄-MMT) compound was prepared. MgFe₂O₄-MMT and biochar were mixed at 0:10, 1:9, 3:7, 4:6, and 10:0 w/w combinations and were used for heavy metal immobilization in soil polluted with multiple heavy metals. MgFe₂O₄-MMT can significantly increase soil alkalinity, and it exhibited the most optimal effect in immobilization of heavy metals in soil. The amounts of Cd, Pb, Cu, and Zn that were extracted by the toxicity characteristic leaching procedure (TCLP) decreased by 58.4%, 50.3%, 42.9%, and 24.7%, respectively. MgFe₂O₄-MMT can immobilize heavy metals through electrostatic interactions and cation exchange processes. Although, the immobilization of potentially toxic elements by MgFe₂O₄-MMT and biochar was inferior to that by MgFe₂O₄-MMT. The combined application of MgFe₂O₄-MMT and biochar dramatically increased the diversity and richness of the soil bacterial community. The Chao1 index for M3B7 treatment group was 1.7 and 1.2 times higher than that for the control and MgFe₂O₄-MMT treatment groups, respectively. The combination of biochar and MgFe₂O₄-MMT might be a cost-effective and ecological remediation approach for mild Pb and Cd contamination.

Keywords: Biochar; Immobilization; Magnesium ferrite; Montmorillonite; Potentially toxic element.