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<p>The high concentration of fulvic acid (FA) derived from natural matter in landfill leachates has generated increasing interest, as it plays a significant role in influencing the mobility of potentially toxic elements in landfill groundwater environments. This study examines the adsorption and transport behavior of FA on landfill unmodified and modified loess soil liners, analyzing key factors (initial concentration, organ-bentonite content, reaction time, and soil–water ratio) using a Box–Behnken design-based Response Surface Methodology (RSM-BBD). Additionally, the research objective includes evaluating the adsorption of lead (Pb<sup>2</sup>⁺), providing a comprehensive assessment of the soil liners' performance against both organic and inorganic contaminants. RSM-BBD analysis showed that the higher the hexadecyltrimethylammonium chloride-modified bentonite (HTMAC-B) content, the larger the adsorption capacity of the mixed soil for FA, which proved that FA was mainly adsorbed on the HTMAC-B. Loess + HTMAC-B exhibited the highest capacity, which can be 30.6 times that of loess. The presence of Pb<sup>2+</sup> notably enhanced the adsorption capacity of FA on the loess with HTMAC-B mixture. However, the increase in HTMAC-B content resulted in a decrease in the equilibrium adsorption of FA in the FA-Pb<sup>2+</sup> dual-contaminant system, mainly due to the reduction of adsorbed COO-Pb<sup>+</sup> and (COO)<sub>2</sub>-Pb complexes. When the HTMAC-B content reached 20%, the breakthrough time of Pb<sup>2+</sup> in the modified liner was shortened by 82%. The use of 5% content of HTMAC-B was identified as appropriate to achieve excellent retardation performance for multi-component pollutants such as organics, organic acids and potentially toxic elements. These insights contribute to understanding how geochemical mitigation of humic substances affects the mobility of potentially toxic elements, and from an engineering perspective, the alternative materials presented in this study may facilitate the construction of thinner liners that meet system requirements while exhibiting excellent adsorption performance for multi-component contaminants.</p>

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Impact of fulvic acids on lead adsorption and transport behavior in cationic surfactant modified bentonite-loess liners

  • 期刊论文

  • 发表日期：

    2025年5月26日

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  • Jiawei Wu,
  • Yun Chen,
  • Haijian Xie,
  • Abdelmalek Bouazza,
  • Huaxiang Yan

摘要

The high concentration of fulvic acid (FA) derived from natural matter in landfill leachates has generated increasing interest, as it plays a significant role in influencing the mobility of potentially toxic elements in landfill groundwater environments. This study examines the adsorption and transport behavior of FA on landfill unmodified and modified loess soil liners, analyzing key factors (initial concentration, organ-bentonite content, reaction time, and soil–water ratio) using a Box–Behnken design-based Response Surface Methodology (RSM-BBD). Additionally, the research objective includes evaluating the adsorption of lead (Pb2⁺), providing a comprehensive assessment of the soil liners' performance against both organic and inorganic contaminants. RSM-BBD analysis showed that the higher the hexadecyltrimethylammonium chloride-modified bentonite (HTMAC-B) content, the larger the adsorption capacity of the mixed soil for FA, which proved that FA was mainly adsorbed on the HTMAC-B. Loess + HTMAC-B exhibited the highest capacity, which can be 30.6 times that of loess. The presence of Pb2+ notably enhanced the adsorption capacity of FA on the loess with HTMAC-B mixture. However, the increase in HTMAC-B content resulted in a decrease in the equilibrium adsorption of FA in the FA-Pb2+ dual-contaminant system, mainly due to the reduction of adsorbed COO-Pb+ and (COO)2-Pb complexes. When the HTMAC-B content reached 20%, the breakthrough time of Pb2+ in the modified liner was shortened by 82%. The use of 5% content of HTMAC-B was identified as appropriate to achieve excellent retardation performance for multi-component pollutants such as organics, organic acids and potentially toxic elements. These insights contribute to understanding how geochemical mitigation of humic substances affects the mobility of potentially toxic elements, and from an engineering perspective, the alternative materials presented in this study may facilitate the construction of thinner liners that meet system requirements while exhibiting excellent adsorption performance for multi-component contaminants.