Abstract—Soil stabilization is a remediation method that involves the application of stabilizing materials to the contaminated soil to reduce heavy metal mobility in the soil by changing their forms from mobile to a less mobile form. The heavy metals can be categorized into five fractions, in decreasing mobility order, exchangeable (Ex), carbonate-bound (Carb), iron-manganese bound (FeMnO), organic (Org), and residual (Res) fraction. This study attempts to evaluate the lignin and a commercial plant extract as stabilizing materials for heavy metal immobilization, specifically on copper (Cu) and Nickel (Ni). Lignin showed significant effect on the heavy metal mobility as observed from the change in distribution of the heavy metal fractions. The FeMnO bound Cu in samples treated by lignin was reduced by approximately 23% while the Org Cu increased by 23%. The Carb Ni slightly reduced from 3.71% to 1.47% while the FeMnO and Org Ni increased by about 8% and 9% respectively. The FeMnO Cu in the samples treated by plant extract slightly reduced by 1.81%–3.56%, with increasing reduction as the concentration increases. The Pearson correlation analysis suggest that the increase in pH reduces the mobility of heavy metals by reducing the Carb fraction of the heavy metals (Cu: r=−0.872; Ni: r=−0.915). The soil organic matter (OM) could be the main factor for heavy metal immobilization as OM has strong, positive correlation with the Org fraction of the heavy metals (Cu: r=0.942; Ni: r=0.938). In short, lignin was found to have better stabilizing effect than the plant extract.

Keywords—heavy metal immobilization, lignin, plant extract, soil remediation

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Cite: Li Na Lee, Xinxin Guo, Lee Muei Chng, Matsura Ibrahim, and Mohammed JK Bashir, "Effect of Lignin and Commercial Plant Extract on the Fractionation of Heavy Metals in Multi-Metal Contaminated Soil," International Journal of Environmental Science and Development vol. 15, no. 2, pp. 63-68, 2024.

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