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Various pyrometallurgical processes to produce TiO2 slag have been reviewed, focusing on the solid-state reduction aspects of ilmenite. Most of the upgradation processes from ilmenite to titania slag involve direct smelting of ilmenite and, therefore, are generally considered energy-intensive and not environmentally friendly. On the other hand, the pre-reduction of ilmenite, followed by the smelting processes, is advantageous because of its low energy consumption, furnace stability, and negligible slag foaming. In this paper, the impact of different reducing agents on the ilmenite reduction kinetics has been reviewed. The gas-based reduction techniques, primarily with hydrogen or hydrogen-enriched syngas as reductants, show better reaction kinetics and are more environment-friendly than the carbon-based reduction of ilmenite. Hence, the titania slag production from ilmenite can be made efficient and sustainable by incorporating the pre-reduction concept and gas-based reduction for the pre-reduction step. Numerous ways of improving ilmenite pre-reduction have been investigated intensively, featuring pre-oxidation, additives, mechanical activation, and microwave-assisted reduction. Since ilmenite is a good microwave absorber and the microwave-assisted reduction process provides faster kinetics, the method is also very promising for large-scale applications. [ABSTRACT FROM AUTHOR]

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]

The study focuses on the use of microwave energy in the reduction roasting followed by magnetic separation studies of an Indian Banded Hematite Jasper (BHJ) ore assaying about 48% Fe. Two coals having different origins have been used as the reductants, and the effects of their petrographical characteristics on the microwave-assisted carbothermic reduction have been discussed. The impacts of various process variables such as microwave power, time, ore and coal size have been studied and subsequently optimized using the Taguchi based statistical design. Microwave power and time are found to be the most influential factors, while the particle sizes of the ore and coal play less significant roles. The coal having higher vitrinite reflectance and lower mineral matter is found to be a better reductant in the microwave roasting as it has given rise to a magnetic concentrate of ~64% Fe with a recovery of 68.4% at process conditions such as a power of 6 kW, time of 16 min and C/Fe ratio of 0.15. In contrast, even at the same C/Fe ratio, the coal having lower vitrinite reflectance and higher mineral matter could generate a concentrate with an iron recovery of 34.59%. The X-Ray Diffraction, optical micrographic, Scanning Electron Microscopic (SEM) and Vibrating Saturation Magnetometry (VSM) studies have been used to characterize the microwave roasted products with an intention to understand the phase changes. [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]