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Phosphogypsum chemistry under highly anoxic conditions
A Carbonell-Barrachina1, R D DeLaune, A Jugsujinda
1División Tecnología de Alimentos, Departamento Tecnología Agro-Alimentaria, Universidad Miguel Hernández, Alicante, Spain.
Waste Management (New York, N.Y.)
|September 7, 2002
Summary
Phosphogypsum (PG) byproduct can be safely used in wetlands. Under reducing and neutral to alkaline conditions, PG addition increases sulfide, reducing toxic metal solubility and environmental risk.
Area of Science:
- Environmental Science
- Geochemistry
- Soil Science
Background:
- Phosphogypsum (PG) is a major industrial byproduct with environmental concerns due to metal leaching.
- High metal concentrations in PG limit its safe environmental application.
- Sulfate reduction in PG and its impact on metal solubility are critical factors.
Purpose of the Study:
- To investigate the reduction of sulfate in PG and the role of sulfide production.
- To determine the effect of sulfide on reducing toxic metal concentrations in aquatic environments.
- To assess the influence of redox and pH conditions on metal solubility in PG-amended sediments.
Main Methods:
- Equilibration of Mississippi River alluvial sediment amended with PG.
- Controlled redox (-250 mV) and pH (5.5, 6.5, 7.5) conditions were maintained.
- Analysis of metal and sulfate concentrations in sediment suspensions.
Main Results:
- PG addition significantly increased sulfide levels in sediment.
- Sulfide precipitation effectively reduced the solubility of spiked heavy metals (Cd, Cr) and natural trace elements (As, Ba, Cd).
- Low pH (5.5) led to higher metal and sulfate release, while neutral to alkaline conditions favored metal immobilization.
Conclusions:
- PG can be safely utilized in neutral to alkaline sediments and reducing environments.
- Sulfide production under these conditions mitigates the risk of toxic metal release into wetland ecosystems.
- Environmental management of PG requires careful consideration of redox and pH conditions.