Valorisation diagnosis of waste from the decontamination of phosphogypsum leachates through a combined calcium carbonate/hydroxide process
F.J. Soto-Cruz,
S.M. Pérez-Moreno,
E. Ceccotti,
A. Barba-Lobo,
J.P. Bolívar,
M. Casas-Ruiz,
M.J. Gázquez
Affiliations
F.J. Soto-Cruz
Department of Applied Physics, Marine Research Institute (INMAR), University of Cadiz, Campus de Excelencia Internacional del Mar (CEIMAR), Cádiz, Spain; Corresponding author.
S.M. Pérez-Moreno
Research Centre of Natural Resources, Health and the Environment (RENSMA), University of Huelva, Campus de Excelencia Internacional del Mar (CEIMAR), Huelva, Spain
E. Ceccotti
Research Centre of Natural Resources, Health and the Environment (RENSMA), University of Huelva, Campus de Excelencia Internacional del Mar (CEIMAR), Huelva, Spain
A. Barba-Lobo
Research Centre of Natural Resources, Health and the Environment (RENSMA), University of Huelva, Campus de Excelencia Internacional del Mar (CEIMAR), Huelva, Spain
J.P. Bolívar
Research Centre of Natural Resources, Health and the Environment (RENSMA), University of Huelva, Campus de Excelencia Internacional del Mar (CEIMAR), Huelva, Spain
M. Casas-Ruiz
Department of Applied Physics, Marine Research Institute (INMAR), University of Cadiz, Campus de Excelencia Internacional del Mar (CEIMAR), Cádiz, Spain
M.J. Gázquez
Department of Applied Physics, Marine Research Institute (INMAR), University of Cadiz, Campus de Excelencia Internacional del Mar (CEIMAR), Cádiz, Spain
Phosphogypsum is an industrial waste considered as naturally occurring radioactive material. Stack disposal and exposure to the environmental condition involve the production of acid leachates with high potential pollutant loads as heavy metals and radionuclides. In this study, a sequential neutralisation process was applied for cleaning the generated releases, and the two obtained residues were characterised from the physical-chemical and radiological point of view before their valorisation. The cleaning process was made up of two steps: the first one using calcium carbonate until pH = 3.5, and the second one using calcium hydroxide until pH = 12. The residue obtained in the first step was mostly calcium fluoride, while in the second step most phosphates were precipitated, mainly as hydroxyapatite. The final liquid was treated to reduce pH lower than 9, which is the limit included in the current directive for discharges of liquid effluents into coastal waters. The main conclusion was that the solids from the first step could be valorised as an additive in the manufacture of commercial Portland cements and ceramics, while the solids from the second step could be used as raw material for the phosphoric acid manufacture.
