Simultaneous alleviation of Sb and Cd availability in contaminated soil and accumulation in Lolium multiflorum Lam. After amendment with Fe–Mn-Modified biochar

In this study, we assessed the capacities of biochar derived from tea branches (hereafter referred to as biochar) and Fe–Mn-modified biochar (MnFe2O4-biochar) to immobilize Sb and Cd in contaminated soils and reduce the bioavailability of Sb and Cd in Lolium multiflorum Lam.. The results of pot experiments indicated that the application of biochar and MnFe2O4-biochar significantly (P < 0.05) improved the soil properties (e.g., pH, nutrient contents, organic content, and enzyme activity). Moreover, the concentrations of extractable Sb and Cd decreased significantly (P < 0.05) with increasing addition of MnFe2O4-biochar, whereas biochar amendment only effectively reduced the extractable Cd content. Sequential extraction analysis demonstrated that the exchangeable Sb and Cd were transformed into less accessible forms, effectively reducing their toxicity, after addition of MnFe2O4-biochar. Finally, amendment with MnFe2O4-biochar significantly (P < 0.05) decreased the accumulation of both Sb and Cd in Lolium multiflorum Lam., subsequently reducing their phytotoxicity. Our findings suggest that MnFe2O4-biochar may be used for the low-cost, effective, and eco-friendly passivation of Sb and Cd in co-contaminated soil.