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Direct hematite flotation from an iron ore tailing using an innovative biosurfactant
No full textThe use of a biosurfactant (BS) in mineral flotation offers numerous advantages over conventional surfactants, such as their low toxicity, high degradation kinetics, and potential for selectively treating low-grade ores. In the present study, the use of a biosurfactant obtained from Rhodococcus opacus bacteria for the flotation of hematite from iron ore tailings was evaluated. The microflotation assessments were conducted in a modified Partridge-Smith cell, and the batch flotation studies were conducted in a mechanical cell (CDC - cell). In addition, the effects of the pH, biosurfactant concentration, and depressant concentration on hematite recovery were evaluated. The results confirmed the biosurfactant adsorption onto the hematite surface, and the biosurfactant decreased the surface tension of the water/gas interface. The critical micelle concentration (CMC) of the biosurfactant was approximately 1 g.L-1. Hematite recovery was feasible at a pH of around 3. In microflotation tests, the iron grade and recovery reached approximately 37% and 30%, respectively. These values increased in batch flotation circuits, specifically in the cleaner stage, the iron grade reached approximately 44% and the recovery was approximately 65%. Thus, the current development proved that this particular treatment of ore tailings carries environmental and technical benefits as an appropriate alternative cleaning technology
Developed Commercial Processes to Recover Au, Ag, Pt, and Pd from E-waste
No full textDue to the supply gap towards increasing demand as well as loss of precious metals by illegal recycling, present research reports application-oriented processes developed at CSIR-NML, India to recover precious metals from small
components of e-waste containing ~0.1–0.8% Ag, ~0.03–0.9% Au, ~0.01–0.02% Pd, ~0.0003–0.0005% Pt, and related effluent. Firstly, ~99.99% Au was recovered from plated e-waste using the process of selective leaching followed by charcoal adsorption and heat treatment, whereas the second process consists of dismantling, physical/ chemical pre-treatment of e-waste followed by hydrometallurgical
processing to recover 99% Ag, 99.9% Au, 95% Pd, and 90% Pt. Apart from the above, leaching and selective precipitation were used to recover ~95% Ag from waste
computer keyboards. The effluent generated during the e-waste processing was found to contain ~8–10 mg/L Au, which was also recovered using ion-exchange technique.
All processes presented are scientifically validated and commercially viable after scale-up studies
Recovery of Cobalt as Cobalt Sulfate from Discarded Lithium-Ion Batteries (LIBs) of Mobile Phones
No full textCobalt, an exceptional cathode material present in lithium-ion batteries (LIBs), is an essential element for the production of energy storage devices. But, the
lifespan of rechargeable batteries is decreasing day-by-day, which become obsolete after reaching their end of life. Therefore, an enormous amount of discarded LIBs are
generated. Keeping in mind the above, a novel approach has been made to selectively recover cobalt from sulfate leach liquor of discarded LIBs containing 1.4 g/L Cu,
1.1 g/L Ni, 11.9 g/L Co, 6.9 g/L Mn, and 1.2 g/L Li. Initially, Cu and Ni were extracted by solvent extraction techniques using 10% LIX 84-IC. Almost complete
precipitation of cobalt occurred from leach liquor at pH ~3 using ammonium sulfide solutions. Cobalt from the precipitated product was further dissolved in H2SO4 in
presence of H2O2 at elevated temperature. The leach liquor obtained was evaporated to get the cobalt sulfate with a purity of more than 98%
Microstructural Effect of Iron In Titanium Zirconium Alloys
No full textABSTRACT
The report starts with an introduction of basic concepts of some metals are titanium, zirconium, iron, molybdenum etc, which exhibit excellent physical, chemical and mechanical properties after alloying. Design and implementation of these kind of alloys possible by metallurgical development for different compositions required.
Many reactive metals are difficult to prepare in pure form without complex procedures. Alloy development is the key factor for development of better materials for engineering applications.
To maintain the superior biocompatibility, corrosion resistance etc of some alloy elements especially in biomedical implants and consumer applications like eye glasses, wrist watches are becoming major attaraction for human kind in the present days due to excess skin allergies caused by metal ions reactions of biomedical implants
Further, the most important characteristic property before alloying has to be considered is corrosion resistance. As no metal, or alloy, is entirely inert to corrosion, it is important to understand the characteristics before using it in any applications.
The result indicates that addition of iron in Zirconium improves the effect of β-phase stability and improves the properties of titanium zirconium alloys for many applications. Hence we proposed to study the phase behaviour of the Zr-Ti-Fe alloy along with characterization of the alloys.
Hence in this MTech thesis we focus on the effect of iron on (Zr-Ti) alloy and microstructural and mechanical properties. In this study, alloys are to be fabricated by arc melting followed by polishing and etching treatments to achieve observe optical microstructural effect of the alloys. Further alloys will be characterised by X-ra
Corrosion at the Weld Nugget of the Friction-Stir-Welded Medium Strength Steel: Effect of Microstructure
No full textIn the present investigation, friction stir welding (FSW) was carried out on C-Mn steel using various welding parameters. The microstructural examination of the weld nugget (WN) region revealed different area fractions of cementite, pearlite, bainite, and martensite within the ferrite matrix. The average hardness in the region of the WN was higher than the base material. The corrosion behavior of the WN and base metal was investigated. The base metal underwent uniform corrosion. Localized pitting corrosion was dominant in the region of the WN. The primary corrosion products were γ-Fe2O3 (maghemite), γ-FeOOH (lepidocrocite), and Fe3O4 (magnetite). The corrosion rate of the WN was significantly higher than that of the base metal. However, the same was considerably lower than the conventionally fusion-welded specimens. Further, the corrosion rate of the WN increased with the increment in the rotational speed of the tool. The change in the corrosion rate at the WN for various specimens was influenced by the matrix grain size, quantity of second phase, area fraction of special boundary, and relative quantity of low- and high-angle grain boundaries
Energy efficient process for recovery of rare earths from spent NdFeB magnet by chlorination roasting and water leaching
No full textRare earth elements are one of the most essential ingredient of modern technological applications. The extraction and recovery of rare earths from primary resources generates huge overburden, which adversely affect the environment. The spent Neodymium-Iron-Boron (NdFeB) magnet can be a potential secondary resource of rare earths through urban mining and recycling. In the earlier studied hydrometallurgical processes for the recovery of rare earths from spent NdFeB magnet, use of concentrated acids during leaching, discharge of acidic effluents and involvement of energy intensive oxidation roasting operations (500-950 degrees C) found as the major drawbacks of the processes. In view of high energy consumption and environmental concern, the present paper is focused on the development of an energy efficient process for the recovery of rare earths from spent NdFeB magnet. In this study, conventional oxidation roasting-acid leaching method was adapted to a lower temperature chlorination roasting-water leaching process by reducing the roasting temperature to 300 degrees C. In the process, ammonium chloride (NH4Cl) was used as chloridizing agent. The thermodynamic feasibility for selective chlorination of rare earths in the presence of NH4Cl was studied using FactSage and Thermo Gravimetric-Differential Thermal Analysis (TG-DTA). In order to determine the most suitable chlorination roasting condition, the effect of different parameters such as temperature, NH4Cl dosage and roasting time were studied in detail. The roasted products were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy - Energy Dispersive X-Ray Spectroscopy (SEM-EDS) and chemical analysis. The rare earths were quantitatively and selectively recovered at the most suitable chlorination roasting condition (300 degrees C, 3 times of stoichiometric amount, 3 h) followed by water leaching. From the leach solution, rare earth oxide of 99.2% purity was produced. The leach residue containing 96.4% Fe2O3 was obtained as a by-product of the process. The lower chlorination roasting temperature and shorter roasting time (300 degrees C, 3 h) make the process more energy-efficient. The process with zero effluent discharge is easily scalable and environment-friendly
Phase transformation, Mechanical Properties and Corrosion Behavior of 304L Austenitic Stainless Steel Rolled at Room and Cryo Temperatures
Get PDFThe present work investigates the effect of rolling (90% thickness reduction) on phase transformation, mechanical properties, and corrosion behaviour of 304L-austenitic stainless steel through cryorolling and room temperature rolling. The processed steel sheets were characterised through X-ray diffraction (XRD), electron backscattered diffraction (EBSD), and vibrating sample magnetometer (VSM). The analysis of XRD patterns, EBSD scan, and vibrating sample magnetometer results confirmed the transformation of the austenitic phase to the martensitic phase during rolling. Cryorolling resulted in improved tensile strength and microhardness of 1808 MPa and 538 VHN, respectively, as compared to 1566 MPa and 504 VHN for room temperature rolling. The enhancement in properties of cryorolled steel is attributed to its higher dislocation density compared to room temperature rolled steel. The corrosion behaviour was assessed via linear polarisation corrosion tests. Corrosion resistance was found to decrease with increasing rolling reduction in both room temperature rolled and cryorolled specimens
Evolution of microstructure and deformation behavior in Al–Ni added medium-Mn steel processed through intercritical / cold rolling and annealing
No full textIn the present work, the effect of intercritical annealing on Fe–8Mn–4Al-3.5Ni-0.8Si-0.25C (wt.%) medium-Mn steel, processed through two different processing routes viz. intercritical rolling (IR) and cold rolling (CR), has been studied. The microstructure, mechanical properties, austenite stability and deformation behavior of the steel, after intercritical annealing (IA) at different temperatures (760, 800 and 840 °C), has been investigated. It has been observed that different rolling regimes (intercritical rolling and cold rolling) give rise to distinct variation in the grain structure owing to different recrystallization behavior during intercritical annealing. The IR-annealed samples showed a mixture of lath and equiaxed grains while the CR-annealed samples showed mostly equiaxed grain morphology. Due to extensive recrystallization in CR-annealed samples, a higher fraction of retained austenite was formed, as compared to IR-annealed samples. The yield strength (YS) and ultimate tensile strength (UTS) was found to be higher for IR-annealed samples, as compared to CR-annealed samples, at all annealing temperatures. However, a high elongation (EL) of 57 % with (UTS x %El) product of 47.7 GPa% was obtained in CR sample, annealed at 800 °C. The mechanical stability of retained austenite was found to influence the work hardening behavior of the annealed samples. The CR-annealed samples exhibited strain-induced transformation to α′-martensite, as compared to ε-martensite transformation in IR-annealed samples. A sustained three-stage strain hardening behavior during deformation, comprising combined TWIP and discontinuous TRIP effect, led to excellent strength-ductility combination in CR sample annealed at 800 °C
Dangling Bond-Induced Surface Depletion in CdS Leaf
No full textUnderstanding the surface electronic properties of nanostructured CdS is important for the development of next-generation sensors and optoelectronic and photocatalytic devices, as efficiency is solely dependent on surface activity. In this study, we have shown dangling bond-induced surface depletion in the CdS leaf structure. The angle-resolved X-ray photoelectron spectroscopy (ARXPS) data of the Cd 3d peak measured at different take-off angles ranging from 0 to 55 degrees indicate that the spectra contain surface peaks centered at 407.9 and 414.6 eV with the bulk peaks centered at 405.5 and 412.2 eV. Furthermore, the separated Cd 3d XPS peaks of the surface and the bulk are merged by the stray electrons of the electron flood gun operated at a bias voltage of 9 eV and an emission current of 1 mA, indicating that the electron deficiency of the depletion layer can be modulated by external electrons. It is observed that the valence band maxima (VBM) of the surface and the bulk are located at 3.14 and 1 eV below the Fermi energy level, respectively. However, such ARXPS features are not observed in the case of spherical-structured CdS. The analysis of these results suggests that the depletion layer of the leaf structure is formed at the surface due to the high density of dangling bonds. The dangling bonds responsible for surface depletion are further confirmed from the density of states (DOS) calculation using density functional theory (DFT) with Coulomb interaction (U)
CSIR-NML NEWSLETTER JANUARY- 2021
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For the period January, 2021,
CSIR-National Metallurgical Laborator