Valorization of Philippine phosphogypsum through optimized calcium extraction via salt and acid leaching for indirect mineral carbonation applications

Phosphogypsum (PG), a by-product of phosphate fertilizer production, poses several environmental risks including heavy metal contamination, geotechnical stability of tailing ponds, and radioactivity levels. Only 15% of PG is being utilized for cement and agricultural applications. Current developments have been exploring PG for mineral carbonation (MC). In this study, the calcium extraction process from Philippine PG was established and optimized via salt and acid leaching. Optimal Ca extraction efficiencies of 18.3% (2.5 M NaCl, 38°C, 60 min, and 26 mL/g L/S ratio) and 93.0% (2.3 M HCl, 62°C, 60 min, and 26 mL/g L/S ratio) were obtained for salt and acid leaching, respectively. Life cycle impact assessment of a theoretical MC plant utilizing acid leaching for Ca extraction showed that while constructing an MC plant offsets benefits brought by carbon capture, mineral resource use, reduced landfill, and process water recirculation can still be achieved. This study proves that local PG can be a potential feedstock for indirect MC with manageable environmental impacts that can be further worked on with green extraction methods and possible resource recovery.