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Solvent Extraction for Separation of 99.9% Pure Cobalt and Recovery of Li, Ni, Fe, Cu, Al from Spent LIBs
No full textIn this work, hydrometallurgical recycling of metals from high-cobalt-content spent lithium-ion batteries (LIBs) from laptops was studied using precipitation and solvent extraction as alternative purification processes. Large amounts of cobalt (58% by weight), along with nickel (6.2%), manganese (3.06%) and lithium (6.09%) are present in LiCoO2 and Li2CoMn3O8 as prominent Co-rich phases of the electrode material. The pregnant leach solution (PLS) that was generated by leaching in the presence of 10% H2O2 using 50 g/L pulp density at 80 degrees C for 4 h contained 27.4 g/L Co, 3.21 g/L Ni, 1.59 g/L Mn and 3.60 g/L Li. The PLS was subjected to precipitation at various pH using 2 M NaOH but the purification performance was poor. To improve the separation of Mn and other impurities and in order to avoid the loss of cobalt and nickel, separation studies were carried out using a solvent extraction technique using di-(2-ethylhexyl) phosphoric acid (D2EHPA) and bis-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272). Overall, this study examines the fundamentals of separating and synthesizing 99.9% pure Co sulfate from leach liquor of spent laptop LIBs with remarkably high cobalt content
Preparation and characterization of graphene oxide from coal
No full textHerein, we report a facile method for the preparation of graphene oxide from semi-bituminous coal. Ultrafine powdery (∼72 mesh) demineralized coal was treated with concentrated H2SO4 in presence of NaNO2 in an ultra-sonication system at 80 °C for 24 h followed by the addition of HNO3 to obtain the desired graphene oxide product. The synthesized material was characterized by Raman spectroscopy, XRD, XPS, FTIR, UV–vis spectroscopy, and Zeta potential analyzer. The Raman spectra of the synthesized product show two peaks at 1350 cm−1 and 1590 cm−1, corresponding to the D band and G band, respectively with an ID/IG value of about 1.04. C1s XPS data of synthesized material showed three peaks at 284.46 eV, 286.28 eV, and 289.35 eV corresponding to the presence of C-sp2 carbon, epoxide group, and carboxyl group respectively with the carbon percentage of 64% and the oxygen percentage of 26%. FTIR spectrum of the synthesized material showed a broad peak at 3428 cm−1 corresponding to the stretching mode of the O–H bond and a peak at 1626 cm−1 corresponding to the stretching and bending vibration of water molecules adsorbed on the material. SEM images of the synthesized material show distinct edges, wrinkled surfaces, stacked and layered structures compared to the coal. All the observed results indicate the formation of graphene oxide
Leaching characteristics of rare earth elements from coal ash using organosulphonic acids
No full textExtraction of valuable REEs from end of life products like coal ash is a viral topic. The potency of organosulphonic acids in leaching out REEs from coal ash matrix has not been exploited till date. In the present study, the leaching potential of methanesulphonic acid and p-toluenesulphonic acid was compared towards extraction of REEs from coal ash. The optimized conditions for extraction were determined to be at a temperature of 90 degrees C, for duration of 60 min in a liquid to solid ratio 100 at stirring speed of 600 rpm. At 0.5 M acid concentration, LREE was leached out in about 65-70% yield whereas HREEs could be only extracted in about 15-20% yield. XRD diffraction studies revealed that the leaching with organosulphonic acids did not destroy the aluminosilicate matrix of coal ash. MSA imparted good selectivity in leaching, wherein, it leached out 70% of REE along with minimal quantities of other coal ash elements (<10%). The leaching kinetics studies under varying temperature concluded the process to be diffusion controlled, following the shrinking core model. The leaching potency of organosulphonic acid was found to be at par with mineral acids (HNO3 and HCl), and hence it could be considered as a green alternative to mineral acids which are conventionally widely used in REE extraction from coal ash wastes
The Role of Slag Carryover on the Non-metallic Inclusion Evolution and Magnetic Behavior in Electrical Steel
No full textIn the present investigation, a set of high-temperature experimentations were carried out to improve the understanding of the influence of slag carryover (SCO) on non-metallic inclusion evolution during the production of high silicon electrical steels for functional applications. It was observed that the liquid steel treated with synthetic slag and lime resulted in the formation of CaO-based complex oxide, sulfide, and nitride inclusions in the matrix. Whereas the top slag (synthetic slag and lime) contaminated with carryover slag transforms the complex oxide inclusions to Mn free oxy-sulfide inclusions in the high Si steel. Further, the high-silicon steel evaluated for magnetic property confirms the detrimental magnetic behavior of the steel treated using the top slag with the excess amount of SCO (10 kg/t). The increase in coercivity is due to a higher fraction of sub-micron inclusions in the steel matrix. The industry implications of the present findings are highlighted in the light of the evolution of Goss texture in high silicon steel during downstream processing. The evolution of detrimental inclusions in functional grade (electrical) steels due to the presence of SCO call for stringent process control during the upstream processing of liquid steel to maintain the desired magnetic properties
Kinetics of Carbon Oxidation During Induration of Hematite Ore Pellet
No full textHematite ore pellets require a much higher induration temperature than magnetite ore pellets because no exothermic heat is generated due to oxidation inside during induration-like magnetite pellets. Carbon is used as in situ heat source in hematite ore pellets which can reduce temperature requirement in the induration strand and hence decreases energy consumption. Many investigators have reported that a 0.8-1.25% addition of carbon in hematite pellets can improve the pellet properties also. However, to investigate the exact role of carbon in hematite pellets, its reaction mechanisms and kinetics study are required which have not been done so far. Therefore, the reaction mechanism and its kinetics have been studied in this investigation. It has been found that carbon reaction happens in pellets from the surface towards the center in a topochemical manner which is controlled by pore diffusion of gas, and its activation energy is around 52 k J mol(-1). It is also found that apart from in situ heat, carbon in hematite pellets enhances diffusion bonding which improves pellet properties. This study ascertains the exact role of carbon in hematite pellets which may help operators to use carbon effectively to reduce energy consumption and improve pellet properties
A Study on Brittle Cleavage Fracture on Ti-Mo Nano-precipitation-Strengthened High-Strength Steel
No full textHot-rolled high-strength steel having ferrite matrix and nano-size precipitation possesses a good combination of strength and ductility, and it finds application in the automobile industry for the manufacture of
long member and chassis parts of large-capacity vehicles. Such an application needs steel with high stretch
flangeability since there are several drilled or broached holes in the finished component. Apart from an
adequate strength level of 800 MPa UTS with a minimum elongation of around 16%, the steel requires a
high degree of stretch flangeability to avoid any catastrophic failure during its use. During the commercial
production process, sometimes, the steel grade namely NPS800 (Nano-Precipitation Strengthened 800
grade) exhibited brittle fracture in the tensile test specimens as well as during the component manufacture.
A detailed study was undertaken to understand the causes of brittle fracture or mixed-mode fracture,
despite the steel showing a total elongation of not less than 18%, and the resolution to this problem is
explained in this paper. Despite the steel having tensile strength and total elongation as per specification, the
performance of steel during component forming was found to be erratic. The steel samples while possessing
similar chemical composition and mechanical properties exhibited a variation in stretch formability. The
main strengthening mechanism of this new grade being precipitation hardening by nano-precipitates, a
detailed study involving microstructural characterization became essential to explain the causes of the
incidences of poor stretch flangeability. Our study reveals that the size distribution of nano-precipitate
formed at the austenite–ferrite interfaces plays an important role in determining the steel properties such as
strength, strain-hardening exponent, stretch flangeability, uniform elongation and post-necking elongation.
For the normal finish rolling and coiling temperatures, optimization of chemistry was achieved to obtain the
mechanical properties such as strength and ductility in the desired range. It is observed that the fineness of
the nano-precipitate is important to achieving a good combination of strength, total elongation, strainhardening exponent, and post-necking elongation to obtain satisfactory stretch formability. The study on
the crack tip opening displacement (CTOD) also confirms the significance of finer precipitates on crack
propagation and thereby improving hole expansion ratio (HER). By the study of fracture samples using
transmission electron microscopy, the role of large-size precipitates in causing the mixed-mode or brittle
failure is explained. The significance of the reduction in area (RA), post-necking elongation, and strain rate
sensitivity in achieving a satisfactory HER is established
Prediction of Mechanical Properties of Sensitized Stainless Steel by Neural Network Modeling and Validation Using Ball Indentation Test
No full textElevated temperature sensitization of a 304 stainless steel results in degradation of mechanical properties
and becomes prone to premature failure. In the present investigation, sensitization of 304 stainless steel has
been done in the temperature range of 500–800 C. Yield strength, ultimate tensile strength and fracture
toughness (KJc) of the sensitized 304 stainless steel specimens were determined by ball indentation technique. Microstructural characteristics were quantified and used in artificial neural network to predict the
mechanical properties of the investigated alloy. Neural network was developed with the help of MATLAB
toolbox. Best equation was fitted for training, testing and validating the output. Predicted values from the
developed model exhibited impressive correlation with experimental data obtained through ball indentation
technique as well as with literature reports. The model has proved its distinctive potential in predicting the
mechanical properties of sensitized 304 stainless steel, which faces restriction in bulk sampling from original
component to perform conventional mechanical test during service exposure
Analytical estimation of thermomechanical distortion and interface layer thickness for gas metal arc lap joining of dissimilar sheets
No full textThe thermomechanical distortion and the evolution of an interface layer with intermetallic phases are the two critical challenges for gas metal arc overlap joining of multimaterial sheets. Two novel analytical methods are proposed following mechanistic principles to estimate the thermomechanical distortion and the interface layer thickness. The analytically estimated results are tested rigorously with the corresponding experimentally measured results for gas metal arc joining of aluminium and steel sheets for different process conditions. Both the thermomechanical distortion and the interface layer thickness are influenced predominantly by the wire feed rate and the resulting heat input. The interface layer thickness and the thermal distortion are found to be the minimum for a heat input of 42.4 J/mm corresponding to the lowest wire feed rate of 4 m/min and the highest travel speed of 10 mm/s. The proposed analytical methods can serve as practical easy-to-use design tools for appropriate selection of process variables in gas metal arc overlapped joining of dissimilar sheets to mitigate the joint distortions and restrict excessive growth of the interface layer
Zinc powder preparation from zinc dross
No full textDirect electro winning of zinc containing waste under anodic material may be useful in electrowinning of zinc powder. The present invention deals with the electrolytic zinc powder preparation from zinc dross in sodium zincate solution. The zinc dross was first expose to SEM-XRD for micrographic study and then subjected for wet chemical analysis. It was observed that most of the zinc is in metallic state with few amount of zinc is associated with iron. Different parameters such as current density, current efficiency, voltage and concentration of electrolyte have been studied to establish the process. It was observed that at 5 amp/dm(2) current density the formation of zinc powder is possible with 1.23 kWh per kg of energy consumption. The corresponding impressed voltage was found 1.2 V and with a current efficiency of 90 %. Copyright (C) 2022 Elsevier Ltd. All rights reserved
Sigma phase embrittlement-induced failures of heat-resistant stainless steel traveling grate links
No full textTraveling grates (TG) are used as beds over which green pellets are subjected to a series of thermal cycles, namely preheating, induration, and firing to make the pellets suitable for charging in the blast furnaces of an integrated steel plant. In this work, chronic failures of TG links after a service life of 2.5-3 years are investigated. A comparative analysis of failed, used and new TG links was carried out. Fractography of the failed link revealed an intergranular brittle fracture near the surface followed by a transgranular fracture with a signature of decohesion in the bulk of the fracture surface. Microstructural analysis revealed the presence of pre-existing grain boundary chromium carbides (Cr23C6) in the new (unused) link, which can facilitate easy crack initiation and propagation. Furthermore, failed and used TG link revealed the presence of extensive precipitation of needle-like sigma phase confirmed by a combination of X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy techniques. Such precipitation of the sigma phase occurs during exposure to a susceptible high-temperature range. The presence of the sigma phase is known to embrittle the austenitic stainless steel and such embrittlement is confirmed by a significant increase in hardness and decrease in Charpy impact toughness of failed and used TG links compared to the new TG link. Thermodynamic and kinetic simulations confirmed a high susceptibility of the existing alloy composition to extensive sigma phase precipitation in a wide temperature range. A new alloy composition with higher nickel (similar to 30 wt%) and free from tungsten is proposed to reduce the susceptibility towards in-service embrittlement induced by sigma phase precipitation