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Phosphate immobilization using an acidic type F fly ash.
D G Grubb1, M S Guimaraes, R Valencia
1School of Civil & Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0355, USA. dgrubb@ce.gatech.edu
Journal of Hazardous Materials
|August 11, 2000
Summary
Type F fly ash effectively immobilizes phosphate, removing up to 100% from solutions and over 85 pore volumes in column tests. This study attributes phosphate immobilization to insoluble aluminum and iron phosphate formation in acidic conditions.
Area of Science:
- Environmental Science
- Geochemistry
- Materials Science
Background:
- Phosphate immobilization in fly ash is crucial for environmental remediation.
- Interactions with Type C fly ash are understood, but Type F mechanisms require further investigation.
- Acidic conditions and fly ash composition influence phosphate interactions.
Purpose of the Study:
- To investigate phosphate immobilization mechanisms in acidic Type F fly ash.
- To compare experimental results with modeling predictions.
- To identify key chemical interactions responsible for phosphate removal.
Main Methods:
- Batch equilibration experiments with Type F fly ash.
- Column studies simulating environmental conditions.
- Phosphate adsorption modeling using the Constant Capacitance Model (CCM).
Main Results:
- Batch experiments showed 100% to 75% phosphate immobilization at 50 and 100 mg P/L.
- Column tests demonstrated sustained removal of 10 mg P/L over 85 pore volumes.
- CCM predictions underestimated immobilization due to fly ash heterogeneity.
Conclusions:
- Phosphate immobilization in Type F fly ash is primarily due to insoluble aluminum and iron phosphate formation.
- The study highlights the effectiveness of Type F fly ash in phosphate remediation.
- Compositional heterogeneity of fly ash impacts adsorption modeling accuracy.