Quantitative Insights into Phosphate-Enhanced Lead Immobilization on Goethite
Wanli Lian1, Guanghui Yu2, Jie Ma1
1Key Laboratory for Environmental Factors Control of Agro-Product Quality Safety, Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China.
Environmental Science & Technology
|June 24, 2024
Summary
Phosphate addition improves lead immobilization on metal oxides through electrostatic effects and ternary complex formation. Precipitation of hydropyromorphite also contributes, especially at higher concentrations.
Area of Science:
- Environmental Geochemistry
- Surface Chemistry
- Computational Chemistry
Background:
- Geochemical models struggle to accurately predict lead (Pb) immobilization in environmental settings.
- Understanding Pb-PO4 interactions on metal oxides is crucial for environmental remediation.
Purpose of the Study:
- To investigate the molecular mechanisms of phosphate (PO4)-induced Pb immobilization on metal (hydr)oxides.
- To quantify the roles of electrostatic synergy, ternary complexation, and precipitation in Pb immobilization.
Main Methods:
- Utilized the Charge Distribution MUlti-SIte Complexation (CD-MUSIC) model.
- Employed X-ray absorption fine structure (XAFS) spectroscopy.
- Performed density functional theory (DFT) calculations.
Main Results:
- Phosphate enhances bidentate Pb adsorption on goethite via electrostatic synergy at low concentrations.
- Monodentate-O-sharing Pb-PO4 ternary structures form on goethite at low pH and high PO4 concentrations.
- Hydropyromorphite precipitation occurs at high pH and high Pb/PO4 concentrations, with an optimized log Ksp of -82.02.
Conclusions:
- This study provides quantitative molecular-level insights into Pb immobilization mechanisms.
- Optimized CD-MUSIC model parameters and validated them with XAFS and DFT.
- Findings will help resolve controversies regarding Pb distribution in environmental samples.
Keywords:
CD-MUSIC modelX-ray absorption fine structuredensity functional theoryleadphosphateprecipitationternary complexMore Related Videos
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