Rare earth elements (REEs) as emerging soil contaminants have attracted increasing concerns. Efficient, economical, and eco-friendly soil amendments for REEs-contaminated farmland in-situ remediation are exigently needed. Herein, phosphorus-modified metakaolin (MK-P) was synthesized as a soil amendment to immobilize REEs in soil and reduce their bioaccumulation in water spinach ( Ipomoea aquatica Forssk. ). MK-P was developed by the combination of mechanochemical and thermal treatments using metakaolin and KH 2 PO 4 as raw materials. Our results indicated that the aluminum potassium phosphate and active Al–O–P sites were generated within MK-P, facilitating the immobilization of REEs and the controlled release of phosphorus. The application of 3% MK-P significantly reduced the content of available REEs in soil by 76.7%–99.2% and reduced the REE contents in the shoots (edible parts) of water spinach by 43.0%–57.3%. Correlation analysis suggested that the enhancement for REE immobilization using MK-P could be ascribed to the increase of soil pH and available P. Furthermore, the application of MK-P led to the amelioration of soil fertility, which subsequently increased plant yield by 14.8%–20.1% under MK-P treatment. These findings suggest that MK-P can be used as a promising soil amendment to minimize REE bioavailability in REEs-contaminated soil and improve soil quality.
Deng Wenchao,Wang Guanghui,Wang Bing,Deng Nansheng
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.
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