Phosphogypsum as the Secondary Source of Rare Earth Elements

Faizan Khalil (), Francesca Pagnanelli and Emanuela Moscardini
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Faizan Khalil: Department of Chemical Engineering, La Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy
Francesca Pagnanelli: Department of Chemistry, La Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Roma, Italy
Emanuela Moscardini: Eco-Recycling, Viale Palmiro Togliatti 1639, 00155 Roma, Italy

Sustainability, 2025, vol. 17, issue 19, 1-38

Abstract: Phosphogypsum (PG) is a byproduct of the wet phosphoric acid (WPA) production process. Since PG originates from phosphate rock (PR), it holds various concentrations of heavy metal and radionuclide, posing an environmental threat because of its large production and long-term accumulation. In addition to toxic heavy metals, PG may also be an alternative source of rare earth elements (REEs), since over 60% of REEs in PR transfer to PG during acid digestion. With the increasing demand of phosphoric acid (PA), global PG generation is approaching 300 million tons annually. Since 1994, an estimated 6.73 billion tons of PG has been produced worldwide, with approximately 58% (approx. 3.7 billion tons) ending up in stacks. Assuming a conservative REE content of 0.1%, these stacks may hold over 3.7 million tons of REEs. This review discusses phosphoric acid production processes and the transfer of REEs from PR to PG. In addition, it also discusses the current REEs world reserves, their presence in primary and secondary sources, and their uses. The review critically evaluates the research that has been conducted so far and the recent innovations in REE recovery from PG, and discusses the challenges associated with scalability and raw material variability.

Keywords: rare earth elements; phosphogypsum; phosphate rock; REE’s recovery; scale up challenges; REEs occurrence in phosphogypsum; wet phosphoric acid process; secondary resources; industrial waste valorization; hydrometallurgy; resin in leach (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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