Application of Rice Husk and Corn Cob as Sustainable Reductants in the Roast Reduction of a Low-Grade Iron Ore: Characterization and Statistical Evaluation

Abstract

The iron ore industry faces the depletion of high-quality iron ores, necessitating the upgrading of low-quality ores. One alternative beneficiation technique, such as reduction roasting followed by magnetic separation, is suitable for processing low-grade iron ores that do not respond to physical beneficiation. However, reduction roasting produces significant CO2 emissions owing to its reliance on coal as a reductant. This research study aims to reduce emissions and promote carbon neutrality by utilizing two agricultural residues, rice husk and corn cob, as alternative reductants. The reduction roasting experiments were optimized using the response surface methodology, and under optimal conditions, a grade of 65-66% Fe with a recovery of 91-92% could be achieved from a low-grade iron ore containing about 42% Fe. Characterization studies of the roasted products, conducted using electron probe microanalysis and optical microscopy, revealed the sequential growth of the magnetite phase as a function of the reduction parameters. Vibrating sample magnetometry studies correlated the reduction trend with the magnetic properties of the ore. Similarly, Fourier transform infrared spectroscopy and thermogravimetric analysis explained the reasons behind the suitability of the biomass residues as iron oxide reductants.