Chemical-free synthesis of hematite from natural magnetite for sustainable photocatalytic degradation of dyes in textile wastewater toward agricultural reuse

Abstract

BACKGROUND

Hematite is a promising material for water purification owing to its visible-light activity. This study presents a chemical-free synthesis of hematite via thermal oxidation of naturally occurring magnetite, yielding a sustainable photocatalyst for the treatment of textile industrial wastewater for agricultural reuse. The synthesized hematite was comprehensively characterized to evaluate its physicochemical properties.

RESULTS

Structural analysis confirmed the formation of crystalline hematite with a crystallite size of 64 nm. Morphological studies revealed agglomerated particles predominantly distributed within the 50–300 nm size range. Detailed microstructural characterization showed agglomerated particles composed of nanocrystalline domains of 10–20 nm, with an average particle size of 73 nm and distinct lattice fringes of 0.27 nm, confirming the polycrystalline and phase-pure nature of hematite. Thermal analysis identified the optimal oxidation temperature required for complete phase transformation. Optical characterization revealed a band gap of 1.90 eV, indicating strong visible-light photocatalytic potential. Vibrational analysis further supported the successful formation of crystalline hematite, while magnetic measurements confirmed its weak ferromagnetic behavior. The catalyst exhibited excellent degradation of malachite green (90%) and rhodamine B (82%) within 2 h, retaining 85% and 78% efficiency after five cycles. Scavenger quenching experiments revealed that superoxide radicals (^•O₂⁻) were the dominant reactive species driving degradation. In real textile wastewater, 64% degradation was achieved under sunlight. Seed germination assays with treated water indicated nontoxic effects, confirming suitability for agricultural reuse.

CONCLUSION

Overall, this work demonstrates an eco-friendly, scalable route for producing high-performance hematite catalysts from natural resources for sustainable environmental remediation. © 2026 Society of Chemical Industry (SCI).