Effective lead passivation in soil by bone char/CMC-stabilized FeS composite loading with phosphate-solubilizing...

Area of Science:

• Environmental Science
• Soil Science
• Bioremediation

Background:

• Phosphate-solubilizing bacteria (PSB) offer economical and eco-friendly lead (Pb) passivation in soil.
• Existing methods require improvement for efficient and stable lead remediation.

Purpose of the Study:

• To design and evaluate a novel bone char (BC)-supported biochemical composite (CFB1-P) for lead passivation in soil.
• To investigate the efficiency and mechanisms of CFB1-P in remediating lead-contaminated soil.

Main Methods:

• A composite (CFB1-P) was synthesized using bone char, phosphate-solubilizing bacteria (PSB), iron sulfide (FeS), and carboxymethyl cellulose (CMC) at a 1:1:1 ratio.
• Batch experiments were conducted to assess Pb(II) adsorption capacity and passivation efficiency in contaminated soil.
• Characterization of lead fractions and crystal structures was performed post-remediation.

Main Results:

• The CFB1-P composite achieved a high passivation efficiency of 65.47% and enhanced PSB phosphate solubilization to 140.72 mg/L.
• Maximal monolayer Pb(II) uptake was 452.99 mg/g across a wide pH range (2.0-6.0).
• Application of 3% CFB1-P reduced labile Pb fractions from 29.05% to 6.47% in soil within 10 days, converting them to stable forms.

Conclusions:

• CFB1-P effectively passivates lead in soil through combined mechanisms including chemical precipitation, complexation, electrostatic attraction, and biomineralization.
• The formation of stable lead compounds like Pb5(PO4)3OH, Pb3(PO4)2, and PbS contributes to efficient remediation.
• CFB1-P presents a viable and efficient alternative for remediating lead-contaminated soils.