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Stabilization and solidification of Pb in cement matrices.
Maria A C Gollmann1, Márcia M da Silva, Angela B Masuero
1Instituto de Química, UFRGS, Av. Bento Gonçalves, 9500 Porto Alegre, 91509-900 RS, Brazil.
Journal of Hazardous Materials
|March 30, 2010
Summary
Incorporating lead (Pb) into cement matrices requires careful curing. Longer curing times and a pH of 8 significantly reduce lead leaching, though extended curing may decrease compressive strength.
Area of Science:
- Materials Science
- Environmental Engineering
- Geochemistry
Background:
- Lead (Pb) contamination poses environmental risks.
- Solidification/stabilization (S/S) is a common method for immobilizing hazardous waste.
- Cementitious matrices are frequently used for S/S applications.
Purpose of the Study:
- To investigate the effect of curing time and pH on lead leaching from cement matrices.
- To evaluate the mechanical properties of lead-incorporated cement.
- To characterize the structural changes in the cement matrix after lead incorporation.
Main Methods:
- Cement matrices with incorporated lead were prepared.
- Leaching behavior was monitored using graphite furnace atomic absorption spectroscopy (GF-AAS).
- Mechanical strength was assessed via unconfined compressive strength (UCS) tests.
- Metal mobility was analyzed using X-ray fluorescence (XRF) spectrometry.
- Matrix characterization employed DRIFTS, TGA, SAXS, and XRD.
Main Results:
- Extended curing times significantly reduced lead leaching.
- Optimal lead immobilization was observed at pH 8.
- Increased curing time led to a decrease in compressive strength.
- TGA and DRIFTS confirmed that hydration excess did not cause strength reduction.
- XRF indicated lower calcium (Ca) concentration in lead-amended matrices.
Conclusions:
- Longer curing periods and controlled pH are crucial for effective lead stabilization in cement.
- The observed decrease in compressive strength with extended curing requires further investigation.
- Understanding the interaction between lead and cement components is key for optimizing S/S processes.
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