Mineralogical Controls on Phosphorus Accessibility During Fe(II)-Catalyzed Recrystallization of Natural Goethitic...

Phosphorus (P) associated with goethitic iron ores remains a major challenge for iron ore beneficiation because much of the P is hosted within Fe-associated mineral domains that are poorly accessible to conventional extraction methods. Here, we investigate Fe(II)-catalyzed recrystallization as a low-temperature mineralogical conditioning strategy for selectively restructuring natural goethitic iron ores and enhancing P accessibility. Two goethite-rich Pilbara ores with contrasting crystallinity, Al-Si-substitution, and structural complexity were reacted with aqueous 57Fe-enriched Fe(II) under circumneutral anoxic conditions. Fe(II) rapidly transferred from solution to the solid phase, driving Fe atom exchange and structural reorganization without formation of new bulk crystalline Fe phases. Isotope tracing revealed substantially greater Fe atom exchange in the Fe-rich, well-crystalline ore (GOL, ∼15%) than in the Al-Si-rich, structurally heterogeneous ore (GOV, ∼7%), demonstrating that natural mineralogical complexity strongly controls Fe(II)-catalyzed recrystallization. Fe(II) treatment generated a transient pulse of dissolved P followed by rapid resequestration into the solid phase, accompanied by a marked increase in operationally defined NaOH-extractable P demonstrating that recrystallization enhances P accessibility rather than removing P directly from the ore. NaOH-extractable P increased to ∼75%-80% of the initial bulk P content in GOL but only ∼35%-40% in GOV, whereas Al remained largely immobile (<10%) and Si exhibited minimal changes in both aqueous and NaOH-extractable pools, confirming that Fe(II)-catalyzed recrystallization selectively restructures Fe-bearing P-hosting domains while largely preserving aluminosilicate and silica-rich components. Collectively, these results establish Fe(II)-catalyzed recrystallization as a mineralogical conditioning step that redistributes Fe-associated phosphorus into more alkali-accessible pools prior to alkaline extraction. The efficiency of this process is governed by crystallinity, Al-Si-substitution, and structural heterogeneity, providing new mechanistic insight into low-temperature mineralogical conditioning strategy for enhanced P extractability of natural goethitic iron ores.