Abstract: To efficiently remediate combined heavy metal-contaminated soil with high concentrations in mining areas,this study explored the simultaneous passivation effects of organo-modified bentonite on Cd,Pb and Zn in composite contaminated soil using various organic modifiers.Sodium dodecyl sulfate (SDS) and tetraethylenepentamine (TEPA) were selected as opti mal modifiers through initial screening.Under optimal modification conditions,the reduction rates of available Cd,Pb and Zn in soil increased from 10.23%,11.50% and 12.80% for unmodified bentonite to 31.53%,41.64% and 37.72% for SDS-modi fied bentonite,and to 21.62%,32.56% and 37.35% for TEPA-modified bentonite,respectively.Characterization using FTIR, XRD and SEM-EDS confirmed successful loading of organic modifiers onto bentonite.TEPA enhanced heavy metal immobiliza tion through complexation by amino groups,while SDS facilitated immobilization via electrostatic attraction and ion exchange by sulfonic groups.Additionally,organic intercalation reconstructed the pore network of bentonite,forming an intercalation-exfoliat ion coexistent structure and increasing the average pore diameter,thereby optimizing mass transfer pathways.Organo-modified bentonite significantly improved the remediation efficiency of heavy metal composite contaminated soil through a dual mecha nism of "pore structure optimization combined with functional group binding".

Key words: combined heavy metal contamination,soil remediation,organo-modified bentonite,simultaneous passivation, modification mechanism