Textural complications of banded iron formation and the potential production of nano-magnetite: a case study from the Central Eastern Desert of Egypt

Abstract

The current work makes integrated value-added, geological and chemical studies on the texturally intricate banded iron formation “BIF” that is represented here, as a case in point, by the Um Nar BIF located in the Central Eastern Desert of Egypt. Geologically, the Um Nar BIF is composed mainly of oxide-rich facies and silicate-rich facies mostly expressed as bands of variable thickness (90–730 µm). Magnetite, martite, goethite, and quartz are detected as the main components of the oxide-rich facies, while epidote, stilpnomelane, and garnet occupy the other facies type. The studied ore can be classified as a low-grade iron ore containing 51.23 wt.% Fe2O3 and 39.64 wt.% SiO2 along with considerable phosphorous content (1.01 wt.% P2O5). These elemental concentrations do not match the recommended benchmarks for iron and steelmaking (e.g.75.78–95.8 wt.% Fe2O3, 5–7 wt.% SiO2, and 0.04 wt.% P2O5). Moreover, the studied BIF has a poor liberation behavior on crushing and grinding due to the complex interlocking of magnetite with quartz and stilpnomelane expressed as a sieve-like texture. This textural complication directed the current work to investigate the potential exploitation of the Um Nar BIF as a precursor of nano-magnetite that is commonly synthesized by ferrous and ferric chlorides. Accordingly, HCl-based agitation leaching followed by co-precipitation was carried out, resulting in ultrafine mesoporous nano-magnetite (2.47–4.27 nm particle size, 120 m2g−1 surface area, 0.55 cm3g−1 pore volume, and 4.88 nm pore diameter) expected to serve in water treatment as an effective adsorbent for heavy metals.