Mineralogical and geochemical investigations have been carried out on organic-rich and inorganic-rich fractions of Ib Valley coal to understand the association and distribution of macerals, minerals, and the occurrence of major, minor, trace, and rare earth elements. Density fractionation was performed using heavy liquids of relative density 2.0 g/ml to generate organic-rich and inorganic-rich fractions, followed by detailed petrography, mineralogy, and geochemical analyses using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The results revealed significant differences in mineralogical composition and elemental associations between the two fractions. The inorganic-rich fraction contained mainly pyrite, siderite, hematite, and some minor sulfides minerals such as chalcopyrite, sphalerite, and galena, with enrichment of trace elements such as Mn, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sn, and Pb. The organic-rich fraction is found to host quartz, clay minerals, apatite, and Ti-oxide with elevated concentrations of Li, Sc, V, Cr, Ge, Ga, Sr, Zr, Nb, Sb, Ba, and W. The rare earth elements, including yttrium (REY), concentration of Ib Valley coal ash is higher than the average REY of global coal ash. In density separation, the REY are found to be enriched in the organic-rich fraction, suggesting their association with aluminosilicates, phosphates, and the oxide bearing phases. These findings provide insights into the mineralogical control on elemental partitioning of Ib Valley coal, with implications for its utilization, environmental impact, and resource management.

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

The article assimilates mineralogical and morphological investigations to carve out a route to beneficiate scheelite values from the Hutti gold mine tailings. Conventional and advanced characterization techniques, such as X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), and Mineral Liberation Analyzer (MLA) have been exploited to ascertain the feed mineralogical behavior, subsequently deriving an effective beneficiation strategy. The gold mine tailing exhibited an ultrafine particle size distribution (d50: 17 mu m) and was predominantly composed of ferromagnesian silicates of amphibole and pyroxene groups along with quartz, arsenopyrite, mica and calcite. The tungsten particles were found to be mineralized in the form of a scheelite mineral (CaWO4), with an average WO3 content of 0.02%. The MLA analysis helped visualize the shapes of different mineral particles and their association with scheelite. It indicated that scheelite particles have an ultrafine particle size distribution (d50 = 10.7 mu m) with a high degree of liberation (about 90% free surface). The ultrafine particle size distribution and a high degree of liberation paved the way for adopting the concentration route via the Falcon concentrator followed by froth flotation. Falcon ended up with gravity concentrate a WO3 recovery of 81.9%; the corresponding grade was as low as 0.19%, primarily due to the presence of coarse and heavy minerals like amphibole, pyroxene, arsenopyrite and pyrite. The froth flotation of the Falcon gravity concentrate using oleic acid as a collector and sodium hexametaphosphate as a depressant could enrich the WO3 content to about 2.8% (about 15 times enrichment). Consequentially, a process flowsheet was proposed based on the pre-concentration studies, which could achieve 2.56% WO3 with an overall recovery of 66%.

The present research highlights the growth of India's iron and steel industry and the increasing demand for energy-efficient iron production methods. The study investigates the use of biochar as a sustainable alternative in the iron ore pelletization process, with the goal of reducing dependence on traditional additives such as coke fines. The evaluation of pelletization performance involved incorporating an organic binder and biochar derived from rice straw as substitutes for bentonite and coke fines, respectively. Various pellet formulations were tested at different induration temperatures to assess their cold compressive strength (CCS), porosity, and metallurgical properties, including the reducibility index (RI), swelling index (SI), and reduction degradation index (RDI). The results indicate that biochar-based pellets exhibit higher CCS and porosity compared to conventional pellets, achieving optimal performance at a lower induration temperature of 1280 degrees C with 0.5 wt% of both the organic binder and biochar. Additionally, the presence of biochar enhances porosity and reducibility while preserving acceptable swelling behaviour. Microstructural and phase transformation analyses further support these findings, shedding light on the mechanisms of pellet consolidation. Overall, the study suggests that biochar, combined with an organic binder, can serve as a viable renewable carbon source, offering an environmentally friendly alternative for sustainable iron production.

Iron ore reduction releases a significant amount of greenhouse gases due to coal-based reductants. This communication aims to tackle this challenge by proposing rice straw as a substitute for coal in the reduction roasting of a typical low-grade Indian iron ore with 51.4 % Fe. The usage of rice straw has another advantage because it is a biomass residue produced in large quantities in agricultural countries like India, often lacking viable applications and being primarily incinerated, leading to various environmental problems. X-ray diffraction and optical microscopic studies revealed that the iron ore sample consists of goethite and hematite as the ironbearing minerals having a complex association with the gangue silicate phases, making the physical separation of iron values challenging. Reduction roasting using rice straw followed by magnetic separation successfully generated an iron ore concentrate with about 65 % Fe and a Fe recovery of 77 % at a roasting temperature of 800 degrees C and a residence time of 45 min. Characterization studies involving optical microscopy, scanning electron microscopy, and thermogravimetric studies explained the phase transformation of the iron ore as a function of the reducing conditions correlating it with the grade and recovery of iron at different levels of operating parameters. Kinetics studies indicated that the biomass-assisted reduction behaviour of the iron ore can be divided into three stages, each following a different model.

The present study investigates biodiesel synthesis from acid oil, a waste product from a vegetable oil refinery, and evaluates its effectiveness as a flotation collector in coal flotation. The work also compares its flotation response with diesel and acid oil. The coal contains 40.67% ash, 41.08% fixed carbon, and 18.25% volatile matter. Vitrinite and inertinite are primary macerals, and quartz, kaolinite, and siderite are principal mineral phases in the coal. The coal's isoelectric point (IEP) is at pH 3.5. The functional groups in the coal and collectors were identified using infrared spectrum analysis (ATR-FTIR). The synthesized biodiesel contains both polar (-COOH, -C=O, -C-O-C) and nonpolar (-C-H, -C-C) groups, as well as oxygenated functional groups (hydroxyl, carboxyl, carbonyl). These functional groups promoted hydrogen bonding with oxygen-containing macerals, enhancing flotation. Flotation tests demonstrate that achieving 14% ash-clean coal with 41% yield is possible by consuming 0.74 kg/t bio-diesel and 0.2 kg/t MIBC from 40% ash-feed coal. A further increase to 1.27 kg/t biodiesel dosage achieves 17% ash-clean coal with a 56% yield. These findings suggest biodiesel, derived from renewable resources, is a promising alternative to diesel oil, offering better selectivity in coal flotation.

The rare-earth elements (REEs) have gained enormous economic and scientific attention due to their distinct properties and new applications. Nepheline syenite rock is an important primary source of rare earth minerals. The nepheline syenite rocks from the Rairakhol area, western Odisha, have been characterized for their rare earth mineralogical and textural characteristics. Preliminary beneficiation studies of these rocks were carried out to upgrade the REE values using falcon gravity separation and floatation technique. Hornblende, biotite, K-feldspar, albite, and nepheline are the major mineral constituents of the nepheline syenite where REE-bearing minerals occur as accessory minerals. The REE mineral phases present are zircon, sphene, apatite, allanite, britholite, and REE phosphate, with grain sizes ranging from 10 to 50 microns. Allanite and britholite occupy the intergranular spaces of major mineral phases and occur as thin lines or veins whereas sphene and zircon occur as inclusions within major mineral phases. The flotation study shows that the total REE content of the froth product could be enriched to 1696 ppm, which is three times more than the total REE content (563 ppm) of the feed sample.

Due to the increased demand and limited supply of nickel, the chromite overburden found in Sukinda Valley, Odisha, can be effectively utilized. This study proposes an alternative method for producing high-quality indurated pellets suitable for direct reduced iron production, which can be further smelted to obtain nickel-based alloys in an energy-efficient manner. Excellent quality pellets from low-grade ferruginous chromite overburden were obtained by optimizing various pelletization parameters, such as basicity values, induration temperatures, and duration. The optimal conditions for producing these pellets were found to be a basicity value of 1.0, an induration temperature of 1300 °C, and an induration time of 10 min. These pellets exhibited excellent metallurgical properties and can be used as a burden for subsequent DRI production. The experimental results were further corroborated by various characterization studies, including X-ray diffraction and scanning electron microscopy coupled with energy dispersion spectroscopy analyses. The study found that the recrystallization of hematite phases during the induration process improved the mechanical strength and various other properties of pellets. However, slightly higher basicity and induration parameters impaired pellet consolidation by creating cracks and forming low-melting slag phases.

The present paper outlines the characterization, electrokinetic behaviour, and flotation response of rejected coking coal fines with 32.5% ash generated in a coal washery in Eastern India. The response methodology and central composite rotatable design (RSM-CCRD) were used for the process modelling and optimization of the flotation process using diesel, methyl isobutyl carbinol (MIBC), and sodium hexametaphosphate as a collector, frother, and depressant to maximize ash reduction, yield, and combustible recovery. At optimum condition, a 9.7% clean ash coal was achieved with a 63% yield at collector, frother, and depressant dosages of 0.78, 0.31, and 0.80 kg/ton, respectively. The model prediction and experimental data corroborated sufficiently. Subsequently, within 1 year, the fines oxidized and did not float with the collector. Fourier-transform infrared spectroscopy (FTIR) confirmed surface oxidation on oxidized coal. The oxidized coal responded favourably to acid oil, a vegetable oil refinery waste. With acid oil as a collector, the oxidized coal can upgrade to 12% clean ash coal with a 60% yield; the combustible recovered is 80%. The work indicates successful upgradation of fresh and oxidized coal using the froth flotation process.

The work illustrates the physico-chemical, petrographic characteristics and flotation response of low-grade oxidized coking coal containing 39.5% ash. The maceral composition, surface oxidation, and particle liberation are the factors that affect coal flotation. The oxidized coal requires more collectors than the freshly ground coal. The flotation process modeling and optimization of -0.5 mm coal fraction was carried out using response methodology and central composite rotatable design (CCRD). The diesel, MIBC, and sodium hexametaphosphate are used as collectors, frothers, and depressants to maximize the coal grade, yield, and combustible recovery. At an optimum dosage of 1.35 kg/ton collector, 0.2 kg/ton frother, and 0.5 kg/ton depressant, it is possible to achieve 11.3% ash-clean coal with a 50.72% yield from 39% feed ash coal. The ash, yield, and combustible recovery model prediction matched well with the experimental results. The R-2 of the ash, yield and combustible recovery model are 0.9676, 0.9662, and 0.9692, respectively. The work highlights that Indian coal can upgrade for metallurgical use using a flotation process.

The utilization of mining and industrial wastes is gaining importance worldwide as it is a potential resource of many valuable minerals. The present study is focused on the separation of the fine and ultra-fine size scheelite particles present in the gold mine tailings using a Falcon advanced gravity concentrator. The manuscript reveals the mechanism of separation, segregation of particles, a saturation of the concentrate bed, and the role of different process parameters in the scheelite recovery. The experimental results indicate that the formation of the concentrate bed inside the Falcon bowl constitutes mainly coarse particles in the initial interval, which are later replaced by fine heavy particles. The saturation studies, carried out using different amounts of feed, indicate that the bowl can operate with 830g of feed sample, called the critical mass, beyond which erosion of particles occurs. Considering the Falcon concentrator efficiency is greatly influenced by operating variables such as bowl speed, wash water rate, and feed rates, statistical tools have been used to evaluate the influence of the different variables on yield, enrichment ratio, and recovery of WO3 values. The results indicate that only bowl speed and wash water have a significant effect on the separation efficiency. The optimum results for all the three responses were obtained as 17.16% yield, 4.66 as enrichment ratio, 67.5% of recovery at a rotational speed of 70 Hz, and wash water rate of 4 L/min where feed rate was fixed at 1 kg/min.

The exclusive properties of lithium make it indispensable for its diversified applications, resulting in a steep increase in the present-day demand. In the present investigation, characterization and laboratory beneficiation studies were carried out on the spodumene-bearing lithium pegmatites of India. The major minerals associated with the sample are spodumene, quartz, albite, orthoclase, and muscovite. The chemical analysis results of the collected samples show a variation of Li2O content between 0.02 to 1.85%. The gravity concentration studies were carried out on the feed material with a Li2O content of 1.10%. Gravity concentration studies following heavy liquid separation (HLS), mineral jig, shaking table, and Falcon concentrator were used to enrich the spodumene content. The sink and float analysis on feed material showed that the spodumene mineral is fairly liberated. A better separation of spodumene from the associated silicate gangue was achieved in HLS and mineral jig. Even though fine particles liberated well, separation in the shaking table and Falcon concentrators were inferior due to lower concentration criteria (CC-1.33). Further, the separation efficiency (SE) has been computed for all gravity concentrators. HLS has higher SE than the mineral jig, shaking table, and Falcon concentrator for separating spodumene from the silicate gangue.

Physical separation of the organic and inorganic constituents in coal mostly depends on the degree of association and the manner of their distribution. The liberation of macerals and minerals in coal holds a vital role in the effectiveness of coal-washing technologies. The intent of the study is to observe the effect of particle size on the distribution of both macerals and minerals in coal. Different size fractions were generated, viz. −3350+1000μm, −1000+500μm, −500+212μm, −212+150μm, 150+75μm, 75+45μm and −45μm by using Indian standard sieves. Petrographic studies were carried out for all the size fractions to understand the distribution and the degree of liberation of macerals and minerals with respect to particle sizes. The results showed that the concentration of vitrinite gradually increases while inertinite and liptinite decrease with the decrease in particle size. Mineral matters decrease/increase with particle size depending upon the nature of associated minerals. Also, the particle size influences the type of mineral matter association depending upon their hardness.

This communication delves into a thorough examination of the reduction roasting–magnetic separation process for a low-grade Indian iron ore that is unresponsive to physical separation methods. The process was conducted in a bench-scale rotary kiln, and various parameters such as roasting temperature, roasting time, kiln rotational speed, and reductant dosage were analyzed to determine their effects on the yield and grade of the magnetic product. Additionally, characterization studies were carried out on both the feed and upgraded products to gain a better understanding of the phase transformations that occurred during the reduction roasting process. The experiments were conducted under specific conditions that included a roasting temperature between 650 and 850 °C, a roasting time of 10–60 min, a kiln rotational speed of 3–9 rpm, and a reductant dosage of 15–30

The effects of microwave and conventional oven drying on the drying kinetics and the quality of the ilmenite-coke composite pellets are presented. The drying time was substantially reduced in microwave drying (90 s) compared to conventional oven drying (10 min) for the exact size of composite pellets. The activation energy values in microwave drying were minimal for bigger-sized pellets. An 8–11 mm pellet size was suitable for achieving the desired pellet properties for both drying methods. The microwave-dried pellets showed quite similar dry strengths to that of the oven-dried pellets; however, the reduction performance of the microwave-dried pellets was better owing to the micro-cracks formation, as observed under the electron microscope, in several grains.

High-quality pellets have been developed from a low-grade Indian chromite overburden containing high silica in the present study. The thermodynamic, hot-stage microscopic, and thermogravimetric analyses of the overburden and pellet mixes predict the temperature of formation of low melting slag phases at various basicity. A temperature in the range of 1200 °C to 1300 °C and basicity between 0.10 and 0.15 have been found ideal for the initiation of the slag phases, whereas higher conditions lead to softening of the pellets. The effect of basicity, binder content, induration temperature, and time on the physical and metallurgical properties of the indurated pellets has been investigated. A binder content of 1 wt pct, basicity of 0.15, induration temperature of 1250 °C, and a time of 20 minutes are optimum to provide the desired properties to the pellets. X-ray diffraction and Scanning Electron Microscopy coupled with Energy Dispersion Spectroscopy analysis reveal that under the optimum conditions, hematite recrystallization and slag formation impart the needed strength (133.8 kg/pellet), porosity (27.8 pct), tumbler index (99.2 pct), RI (76.2 pct), and RDI (1.2 pct). Conversely, increasing the basicity and the induration temperature results in the melting of the slag phases and, therefore, impair the consolidation of the pellets.

The present article discusses the contrasting characteristics of fireclay from two stratigraphically and geologically different locations of Odisha, eastern India, viz. (i) Talabasta from Cuttack district (FC1) belonging to Upper Gondwana Formation and (ii) Basundhara coal mines (FC2) of Lower Gondwana Formation of Jharsuguda district. The study focuses on micro-morphological, mineralogical, and geochemical characteristics of fireclay from the above locations and compare between them in respect of their refractory applications. The micro-morphological and mineralogical analysis inferred the predominance of quartz, kaolinite in both samples along with minor halloysite, goethite, and ilmenite in their various fractions. Layered hexagonal kaolinite, nanohedral kaolinite aggregates, and cylindrical halloysite are recognized under FESEM in FC1. In contrast, in FC2, the kaolinite is poorly crystallized, appears as anhedral to subhedral grains, or aggregates of very fine clay. The compositional analysis using XRF of bulk and its two size fractions (−75 + 45 and −45 μm) indicates FC1 to be rich in SiO 2 and shows relatively less Al 2 O 3 , Fe 2 O 3 , TiO 2 , and K 2 O content than FC2. FTIR pattern, DSC and TGA pattern, and ash fusion temperature between FC1 and FC2 also show some difference. It is surmised that both fireclay samples have desired heat resistance (> 1400 °C) needed for refractory application. However, the AFT of FC1 can be further enhanced by decreasing silica content, and the AFT of FC2 can be improved by reducing Fe content through its proper processing.

With gradually diminishing Fe grade in tandem with the ever-increasing demand for high-grade iron ores, iron ore industries are now focusing on the beneficiation of low-grade iron ore fines, mainly considered waste. Besides, the scarcity of water at many of the mines’ sites and the new water conservation policies of the governments have necessitated research on suitable dry beneficiation routes. In this context, an effort has been made to evaluate the efficacy of a dry classification unit, such as the VSK separator, in upgrading the iron values of two low-grade Indian iron ore fines, named Sample 1 and Sample 2. The mineralogical studies, involving scanning electron microscopy and X-ray diffraction, suggest that Sample 1 is a low-grade blue dust sample (51.2wt% Fe) containing hematite and quartz as the major minerals, while Sample 2 (53.3wt% Fe) shows the presence of goethite in addition to hematite and quartz. The experiments, carried out using Box—Benkhen statistical design, indicate that blower speed, followed by feed rate, is the most influencing operating parameter in obtaining a good product in the VSK separator. At optimum levels of the operating factors, a fines product with ∼55wt% Fe at a yield of ∼40% can be obtained from Sample 1, while Sample 2 can be upgraded to ∼56wt% Fe at a yield of ∼85%. The results suggest that the VSK separator can be employed as an efficient intermediate unit operation in a processing circuit to upgrade the iron contents of iron ore fines.

The Rairakhol alkaline complex situated in western Odisha consists of litho assemblages such as mafic-rich nepheline syenite, mafic-poor nepheline syenite and leucocratic syenite. These rocks have been investigated with respect to their mineralogy and chemistry with a special focus on their rare earth element (REE) content. Petrographic study reveals that the rocks are mainly medium to coarse grained with hypidiomorphic granular texture and composed of variable proportions of microcline/orthoclase, perthite, nepheline, albite, amphibole, biotite. The accessory minerals are calcite, sphene, zircon, thorium uranium oxide, apatite and opaques (mainly ilmenite, magnetite, pyrrhotite). Petrochemical analyses confirm that these nepheline syenites are typically miaskitic to marginally agpaitic with agpaitic coefficient [(Na + K)/Al molar prop.] varying between 0.75 and 1.01. Scanning electron microscope study shows that some REE-bearing mineral phases occur as inclusions or in interstitial spaces of the major mineral phases of nepheline syenite. The REEphases are of RE-sillicates, RE-oxides, and RE-phosphates which are generally rich in their LREE content. The identified REE-bearing mineral phases are britholite, allanite, apatite and zircon. The leucocratic syenite shows a strong positive Eu anomaly whereas the mafic-rich and mafic-poor nepheline syenites show a slightly negative Eu anomaly indicating that the rock originated from a highly fractionated magma. A rare Tm anomaly found in the leucocratic syenite indicates some influence of refractory dusts derived from carbonaceous chondritic material during their formation. This study provides an insight into the mineralogical and petrological peculiarities of this alkaline complex which might guide further exploration programs.

The Precambrian Eastern Ghats Group of rocks consisting of a series of regionally metamorphosed rocks such as khondalite, charnockite, calc-granulite and quartzite hosts several pockets to lensoidal Mn-ores in Odisha, Eastern India. The Mn-minerals identified in these deposits are Mn-silicates and lower Mn-oxides with Mn-oxyhydroxides. Lithiophorite, an aluminous Mn-oxyhydroxide mineral, is conspicuous with other secondary Mn-phases. It generally occurs in two habits, such as cryptocrystalline/crystalline aggregates either as vug fillings or as replacement of other minerals like cryptomelane/romanechite/goethite/graphite. Two morphological types of lithiophorite viz. globular and platy were examined in detail by optical and electron microscopy. The electron probe micro-analyses (EPMA) of these two morpho-types reveal the cryptocrystalline (globular) type to be rich in both CoO and NiO, while the platy crystalline type is preferentially enriched in NiO and depleted in CoO. Compositional map for both the types also supports such selective entrapment. Binary plots of electron probe data for MnO 2 and Al 2 O 3 versus CoO and NiO in the globular type show strong positive relation confirming to their presence in adsorbed state. In contrast, the NiO in platy type show strong positive relation with Al 2 O 3 only indicating desorption of Co and a part of Mn from the structure during crystallisation and its subsequent diadochic substitution in the alumina lattice.