Sulfur Modified Biochar Supported Ferrous Sulfide Composite for the Immobilization of Cadmium in Contaminated Soil

The contamination of soil with cadmium (Cd) poses a significant risk to both food safety and human health. It is crucial to urgently identify an effective technology for remediating Cd-contaminated soil. In the present study, a novel sulfur modified biochar supported ferrous sulfide (FeS@SBC) composite was fabricated by calcination and hydrothermal method. Indoor culture, column leaching, and pot experiments were employed to examine the immobilization effect of FeS@SBC on Cd in contaminated soil. The outcomes illustrated a significant immobilization effect on the Cd-contaminated soil with the application of FeS@SBC. After incubating the soil with the stabilizer for 28 d, the Cd that was previously highly mobile underwent a transformation into an immobilized state. In the experiment on leaching using simulated acid rain, the treatment with FeS@SBC showed a noteworthy decrease in the cumulative loss and leaching efficiency of Cd when compared to the control experiment. It achieved reductions of 70.9% and 71.6%, respectively. The adsorption and immobilization mechanisms resulted from co-precipitation, ion exchange and surface complexation. In the outdoor pot experiment, after 28 d of growth, the water spinach in contaminated soil treated with FeS@SBC has a better growth compared to the control group, with a biomass increase of 134.95%. Additionally, the values of BCF and TF of Cd decreased by 62.25% and 40.39%, respectively, and the available concentration of Cd in the soil decreased by 23.87%. The FeS@SBC composite shows promise as an effective stabilizer for remediating Cd-contaminated soil.