Comparison of Immobilization Efficiency of Two Plant-Based Biochar for Pb-Contaminated Soil

The present study explores the utilization of a stabilization technique to immobilize lead (Pb) in contaminated soil, considering it a remediation strategy. As stabilizing agents, two forms of biochar derived from plants were utilized: wood biochar (WB) and oilseed biochar (OB). Binder doses ranging from 0 to 10 wt% were applied to the Pb-contaminated soil and were left to cure for up to 28 days. The effectiveness of the remediation was measured using the leaching potential technique (TCLP test) and the sequential extraction procedure (SEP). Additionally, an assessment of the mechanical strength of stabilized soil was also carried out. Scanning electron microscopy (SEM) was performed to understand the immobilization mechanism. Findings indicated a decrease in TCLP-Pb levels corresponding with an increase in biochar dosage, with oilseed biochar demonstrating superior immobilization capabilities compared to wood biochar. Application of 5 wt% for OB and 10 wt% WB were sufficient to satisfy the TCLP regulatory level of 5 mg/L. The chemical extraction procedure revealed that high levels of Pb immobilization were primarily associated with lower F1 and F2 fractions (weak and soluble) and higher F3 and F4 fractions (insoluble and stable). In addition, the results of the SEM examination demonstrated that the effective Pb passivation was strongly connected with the lead precipitates generated by both biochar.