Building up and Characterization of Calcined Marl-Based Geopolymeric Cement

The present study mainly investigates the synthesis of calcined marl-based geopolymeric cement under different synthesis conditions including NaOH concentration, sodium silicate (SS)/sodium hydroxide (SH) mass ratios, solid (S)/liquid (L) mass ratios, calcination temperatures, curing temperatures, curing times, and aging intervals. The studied head sample was obtained from the Abu-Tartur phosphate mine in the Western Desert of Egypt and subjected to chemical and mineralogical characterizations using X-ray fluorescence (XRF), X-ray diffraction (XRD), and Fourier transform–infrared spectroscopy (FT–IR). Regarding calcination, this was conducted at 550, 650, 750, and 850 °C for one hour and resulted in thermal decomposition of calcite and saponite and the formation of new mineral phases including anthophyllite, wollastonite, and silica. On the other hand, the geopolymerization process was initiated by mixing the calcined marl sample with the alkali activation solution at different mixing ratios and varying curing conditions. The compressive strength measurements indicate that 750 °C, 12 M NaOH, 0.6 SS/SH mass ratio, 2 S/L mass ratio, 80 °C curing temperature, 12 h curing time, and 28 days aging time are considered all to be the optimum synthesis conditions of the Abu-Tartur calcined marl-based geopolymer

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