Spatial distribution and leaching behavior of pollutants from phosphogypsum stocked in a gypstack: Geochemical characterization and modeling.
J Environ Manage
; 193: 567-575, 2017 May 15.
Article
em En
| MEDLINE
| ID: mdl-28242112
ABSTRACT
Phosphogypsum (PPG) is the byproduct of the production of phosphoric acid and phosphate fertilizers from phosphate rocks (PR) by acid digestion. Despite the technical feasibility, the impurities present in this waste make its reuse critical and large amounts of PPG are stockpiled, resulting in the production of polluted acid leachates. The aim of the present study was to characterize the spatial variability and evolution in time of a 20-year-old gypstack and to study the geochemical behavior of the waste in order to assess the best management options. Chemical and mineralogical analyses were performed on core samples taken from 4 different depths of the stack down to 13.5 m. Despite the high homogeneity shown by chemical and mineral characterization, leaching tests revealed a different chemical behavior with depth. pH-dependent leaching tests were also performed to measure the acid neutralization capacity of the studied matrices and to determine the leachability of the elements or pollutants of concern as a function of pH. The study was focused on Ca, Fe Na, Si, Cd and Sr and on F-, PO43- and SO42- anions. The geochemical modeling of these tests with PHREEQC enabled the identification of the minor phases controlling the solubilization of the elements analyzed. Validation of the model by the simulation of a column leaching test suggested that the model could be used as a predictive tool to assess different management scenarios.
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Base de dados:
MEDLINE
Assunto principal:
Fosfatos
/
Fertilizantes
Tipo de estudo:
Prognostic_studies
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article