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Published on: November 9, 2015
Partitioning of radionuclides and trace elements in phosphogypsum and its source materials based on sequential
A J G Santos1, B P Mazzilli, D I T Fávaro
1Laboratório de Radiometria Ambiental, Instituto de Pesquisas Energéticas e Nucleares, Av. Prof. Lineu Prestes, 2242 Cidade Universitária, CEP 05508-000 São Paulo, Brazil.
Journal of Environmental Radioactivity
|December 27, 2005
Summary
Phosphogypsum, a fertilizer industry waste, contains impurities like radionuclides and rare earth elements. These elements are not readily bioavailable, posing no threat to aquatic environments.
Area of Science:
- Environmental Chemistry
- Geochemistry
- Radiochemistry
Background:
- Phosphogypsum is a major industrial byproduct of phosphoric acid production.
- It contains impurities, including radionuclides (U and Th decay series) and rare earth elements (REE), from source phosphate rock.
- Concerns exist regarding the potential radiotoxicity and environmental impact of these enriched elements.
Purpose of the Study:
- To assess the bioavailability of radionuclides (Ra, Pb, Th), REE, and Ba in phosphogypsum from Brazilian producers.
- To determine the association of these elements with the main phosphogypsum matrix (CaSO4) versus impurity fractions.
- To evaluate the potential threat to the surrounding aquatic environment.
Main Methods:
- Sequential leaching experiments were performed on phosphogypsum samples.
- Extraction targeted different fractions to determine element mobility and association.
- Analysis focused on the distribution of specific radionuclides (226Ra, 210Pb, 232Th), REE, and Ba.
Main Results:
- Radionuclides (Ra, Pb) were primarily found in the non-CaSO4 "iron oxide" fraction.
- Only a small percentage (13-18%) of these radionuclides were in the most labile fractions.
- Thorium (Th), REE, and Ba were predominantly in the residual, insoluble phase.
Conclusions:
- Enriched elements in phosphogypsum are not directly associated with the CaSO4 matrix.
- The majority of radionuclides, REE, and Ba are in less mobile fractions.
- Phosphogypsum impurities do not pose a significant threat to the surrounding aquatic environment due to low bioavailability.
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