An amino functionalized iron based biochar for enhanced remediation for lead and lanthanum co-contaminated soil: Stress alleviation and stabilization mechanism

The application of rare earth micro-fertilizers and livestock manure in agricultural production often leads to composite contamination of lead (Pb) and Lanthanum (La) in farmland soils. In this study, biochar (BC) was modified through double amination using ball milling and microwave-assisted grafting technology; meanwhile, Fe nanoparticles were subsequently loaded onto the surface of the modified BC (MN PEI @N BM ). It exhibited excellent adsorption performance, with optimal binding efficiency of 300.01 and 163.68 mg/g for Pb(II) and La(III) in aqueous solutions. When applied at a dosage of 3 %, the DTPA-extractable Pb and La concentrations were significantly reduced by 83.72 % and 90.44 %, respectively, after 25 d of remediation. The intramolecular structural nitrogen, amino/oxygen-containing functional groups, and iron oxides on MN PEI @N BM fully interacted with the Pb and La, facilitating surface complexation and precipitation reactions and promoting the transformation of the active forms of the metals into stable forms in the soil. The application of 1.5 % of MN PEI @N BM alleviated the toxicity of Pb and La to maize seedlings, enhanced the abundance of soil functional microorganisms (i.e. Sphingomonas and Arthrobacter ), and provided essential nutrients to the soil, promoting plant growth and development. The above conclusion demonstrated the promising capability of amino functionalized Fe based BC as a viable solution for addressing soils contaminated with both heavy metals and rare earth elements. • MN PEI @N BM is synthesized by ball milling of ammonia liquor and grafting of PEI. • MN PEI @N BM drops Pb/La bioavailability in soil and relieves stress on maize seedlings. • MN PEI @N BM enhances abundance of toxic metal-resistant and nutrient cycling bacteria. • MN PEI @N BM converts active metal to stable forms via complexation and precipitation.