Purpose <p>Due to the persistence and limited degradation capacity of Ni, Ni concentrations in soil are gradually increasing, posing a great challenge for soil remediation. The objective of this study was to remediate Ni contaminated soil using ferromanganese modified biochar (FMBC) and to elucidate its stabilization mechanism.</p> Materials and methods <p>In this study, using SEM-EDS, XRD, FTIR, XPS as well as adsorption thermodynamic and kinetic models, study the binding characteristics of the material and Ni and the stabilization mechanism of the material on Ni -contaminated soil. Toxicity Characteristic Leaching Profile (TCLP) and BCR sequential extraction procedures were used to study the stabilizing effect of this material on Ni in soil in soil incubation tests.</p> Results and discussion <p>The experimental results show that multilayer chemisorption is the dominant adsorption mechanism, and the stabilization process is mainly dominated by hydrogen bonding, ion exchange of Fe/Mg-O and Ni(II), conjugation effects of aromatic groups containing π-bonds, ketone, carboxyl or ester groups, and surface complexation. TCLP leaching Ni concentrations in contaminated soil can be reduced by over 98% after 30 days of stable recovery at 1% material dosage. Besides, weak acid extractable and reducible Ni concentrations were reduced by 33% and 24%, respectively. Meanwhile, oxidizable and residual Ni concentrations increased by 44% and 14%, respectively.</p> Conclusions <p>These results suggest that Ni in soils has changed from a highly mobile and bioavailable state to a more stable and less ecotoxic state. Therefore, FMBC is a highly promising material for the remediation of Ni-contaminated soils.&#xa0;</p> Graphical Abstract <p></p>