Synergistic phosphorus-carboxyl co-modification of dolomite for enhanced immobilization and long-term stabilization...

The high mobility and bioavailability of Pb in acidic soils pose a serious threat to ecosystems and human health. In this study, natural dolomite was sequentially functionalized using ammonium dihydrogen phosphate and succinic acid to prepare P-DO and SU-PO materials. Systematic characterization demonstrated that the specific surface area of the SU-PO increased significantly to 40.37 m² g^-1 after modification, with the formation of abundant mesoporous structures and the successful loading of phosphate and carboxyl functional groups. SU-PO exhibited a high Pb adsorption capacity of 561.18 mg g^-1, superior to the 405.61 mg g^-1 of P-DO. Furthermore, the adsorption process conformed to the Freundlich model, indicating heterogeneous surface characteristics and multilayer adsorption behavior. In soil incubation experiments, the addition of 1.0% SU-PO significantly reduced the DTPA-extractable Pb content, achieving a passivation efficiency of 67.05%. BCR fractionation analysis revealed that the proportion of Pb in the residual fraction increased by 23.70% after SU-PO treatment. Following 30-day aging tests involving F-T and W-D cycles, the residual Pb fraction in the SU-PO treatment group further increased by 30.80% and 31.20%, respectively, confirming its enhanced resistance to environmental disturbances and long-term stability. This study confirms that synergistic phosphate-carboxyl modification can significantly improve the fixation efficacy and durability of dolomite for Pb, providing novel materials and theoretical basis for the sustainable remediation of acidic Pb-contaminated soil.