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The depletion of high-grade iron ores has necessitated the beneficiation of low-grade iron ores. Flotation is considered the most efficient operation to upgrade the iron content of fine-grained ores that do not respond to gravity or size classification units. Out of several reagents used in iron ore reverse flotation, depressants play a crucial role in selectively making the iron oxides hydrophilic and prohibiting them from reporting to the gangue-rich froth phase. Starch is widely used as the depressant in iron ore flotation. The present paper attempts to highlight different facets of starch as an iron ore depressant. It reviews the important research papers that discuss the origin and chemistry of starch, starch-iron oxide interaction mechanism, and the application of different types of starches and their alternatives in iron ore flotation. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) are finding applications in various domains of physical sciences these days. They are used in organometallic syntheses, catalysis, electrochemistry, fuel, solar cells, lubricants, enzyme, separation technologies, nanomaterials, tissue preservation etc. However, the application of ILs in the area of mineral processing is minimal. Considering the potential use of ILs in metal extraction and many chemical reactions, these compounds may play an essential role in the selective recovery of mineral values from the ores having multiple mineral phases. In this paper, the application of some selected ILs in the mineral flotation studies has been reviewed. The interaction of ILs with the desired mineral phases has been described vide the evidence from zeta potential, X-Ray Diffraction, X-Ray Photoelectron Spectroscopy (XPS), Fourier Transform Infra-Red (FTIR) spectroscopy, Raman spectra as well as molecular modeling studies. The results of the studies carried out on low-grade iron ores have indicated that ILs under investigation can be compared with the conventional iron ore collectors such as dodecylamine. [ABSTRACT FROM AUTHOR]

Abstract Alternative beneficiation strategies are now being adopted to upgrade the iron values in low-grade iron ores that do not respond to physical beneficiation owing to their complex texture and poor liberation pattern. Thermal treatment prior to beneficiation, in order to enhance the liberation and downstream beneficiation operation, is one such method. In this context, a low-grade hematite ore with 56.5% Fe has been subjected to heat treatment followed by grinding and wet high intensity magnetic separation (WHIMS). The magnetic separation results indicate that an enhancement in yield by around 15–20% by weight is possible when the ore is heat-treated at 500–800 °C. The sink and float studies indicate a negligible improvement in mineral liberation arising due to the thermal treatment while the Frantz isodynamic separation results suggest a remarkable increase in the mass magnetic susceptibility value from 14.4 × 10−9 to 30 × 10−9 SI units for the treatment at 500 °C. Detailed mineralogical characterization studies of the heat-treated samples using optical microscopy and Electron Probe Micro Analysis (EPMA) show the development of crystallinity as well as formation of both intergranular and transgranular cracks within the ore thereby facilitating the separation process. Graphical abstract Unlabelled Image Highlights • Enhancement in magnetic separation of a low-grade hematite ore using thermal treatment • Improvement in crystallinity of quartz resulting in better separation from iron phases • Formation of euhedral equigranular quratz crystals from the anhedral inequigranular quartz • Increase in yield by 15–20% with increase in grade by 1.5 to 2% by heat treatment at 500–800 °C. [ABSTRACT FROM AUTHOR]

This work illustrates the reduction roasting and magnetic separation studies of a complex Indian iron ore with 57% Fe that could not be upgraded to > 61% Fe using a flow sheet comprising of the conventional unit operations like scrubbing, jigging, magnetic separation or flotation. The sole reason of the poor response to physical beneficiation was mainly attributed to the inadequate liberation of iron as visualized under the reflected light microscope, which revealed the fine dispersion of silica particles within the hematite grains and vice versa. In order to overcome this problem, the ore was subjected to reduction roasting using conventional as well as microwave heating followed by magnetic separation. The effects of different process variables such as reductant concentration, time, and temperature during the process of roasting were studied and subsequently optimized using the Taguchi statistical design. Optical microscopy and X-ray diffraction (XRD) studies of the roasted mass confirmed the formation of magnetite with simultaneous disappearance of the hematite and goethite phases. In the microwave roasting process, the reduction could be achieved in a considerably shorter time as compared to the conventional roasting, and the formation of undesired non-magnetic iron minerals like fayalite was limited as well. In both the processes, it was possible to achieve an iron ore concentrate having 63–65% Fe accompanied by ~ 85–90% weight recovery. [ABSTRACT FROM AUTHOR]

Indian low grade iron ores mostly contain quartz, gibbsite, and clay as the major impurities. Depending upon the ore characteristics, in many instances froth flotation has to be used to recover the hematite and other iron oxides from the ground ores. In this context, the difference in silica and alumina content in low grade iron ores is brought to bear on the prospects of iron ore flotation. For this purpose, pure minerals like hematite, quartz, gibbsite, and clay have been used to prepare synthetic mixtures and analyzed to determine the difference in floatability. The results are compared against natural iron ores with variations in silica and alumina content. The flotation results with oleic acid and dodecylamine show better recovery of iron values in the hematite–quartz mixture as well as in the naturally occurring high silica ore compared to the hematite–clay mixture and the high alumina ore respectively. Similarly results on a variety of iron ores show that high silica content as quartz in the ore causes less hindrance in the flotation of iron ore, whereas the presence of silica as clay inhibits the flotation response of iron ore. The scanning electron microscopic (SEM) studies indicate that clay particles cover the surface of hematite, making it less selective for interaction with the collector. The surface potential studies of clay and quartz suggest that charge reversal takes place for quartz treated with dodecylamine (DDA), but for the DDA adsorption on clay, negative potential values are noted beyond a pH of 4.6. [ABSTRACT FROM AUTHOR]