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Extraction of rare earths from waste SmCo magnet
No full textDue to unique physical and chemical properties, rare earth elements are widely used in various modern applications such as electronics, catalysts, magnets etc. Recently, the demand of rare earths increased worldwide due to its usage in clean energy applications such as electric vehicles, wind turbines etc. In India, it is estimated that the demand of rare earths increased 28 times since year 2016. The primary resources of rare earths are limited and multiple separation stages are required for the extraction of rare earths. In this scenario, secondary resources of rare earths may
serve as potential source of rare earths. After NdFeB magnets, the Samarium-Cobalt (SmCo) magnets are the second most important group of rare-earth-based permanent magnets. The magnetic property of SmCo magnet can withstand even at high temperature (upto 800 °C), therefore it is used in defence equipment, satellite, high-end engines etc. The present study is focused on the extraction of rare earths from scrap SmCo magnet. The solid-state roasting followed by leaching process is studied for the recovery of metals from SmCo magnet. Different parameters such as temperature, time etc. are varied to obtain the optimum conditions. The leach residue obtained at different conditions was also characterized by XRD and SEM
Recovery of Ag, Cu, Ni and Fe from the nitrate leach liquor of waste ICs
Get PDFNovel and simple flow-sheet has been reported to process integrated circuits (ICs) for effective recovery of
metals. The depopulated ICs from waste PCBs were pulverised, beneficiated and leached in nitric acid. From the
nitrate leach liquor, Fe was removed at pH 3.5, temperature 60 °C and air sparging. Subsequently, 99.99% Ag
was precipitated as AgCl using 5% NaCl in mixing time 10 min. Further, 99.99% Cu was extracted from the
filtrate using 20% LIX 984 N along with 2% isodecanol (ID) diluted in kerosene at pH 2.97, organic to aqueous
phase ratio 1 in 10 min, leaving Ni in the raffinate. From the obtained pure solutions, salts of Cu and Ni could be produced using evaporation technique. The developed hydrometallurgical process flow-sheet to recover valuables from the nitrate leach liquor of waste ICs has the potential to be commercialised after pilot/ scale-up trial validations
Advances in Synthesis, Luminescence and Characterization Studies of Red Phosphor
No full textRare earth doped phosphors are an important group of luminescent materials that can render white light. These phosphors play an integral role in development of next generation light sources for illumination. However, the commercially available white light emitting diodes (WLEDs) lacks the red-light component resulting to low colour rendering index. This inculcates the need of development of novel phosphors with remarkable red-light emission. Extensive research work has been conducted for the development of phosphors with high luminescence efficiency, longer life span, compact design and minimum adverse environmental effect. Solid state combustion, coprecipitation, forced hydrolysis technique and sol-gel method are generally used for the synthesis of red phosphor. The luminescence efficiency is highly dependent upon the type of dopant added and its concentration.
This review article provides an insight into different routes of red phosphor synthesis, characterization and factors influencing luminescence efficiency. Moreover, Photoluminescence studies of phosphor powder doped with different activators are compared and reported
A novel rate based methodology for creep fatigue life estimation of superalloys
No full textIn this present work, we present an accumulated inelastic strain rate based methodology to predict creep fatigue life of two different superalloys i.e. Haynes 282 and IN 718. The evolution of differential strain rate during creep and fatigue respectively motivated the present work. As creep is the rate controlling damage process in creep fatigue interaction, present mean strain rate based approach considers creep strain rate as a kinetic variable controlling the process. The other variable considered for this approach is accumulative cyclic strain during Creep-fatigue interaction. Our prediction method is purely based upon a relative accumulation rate of creep and fatigue strain. This method correlates the creep fatigue life with rate of interaction in strain-controlled regions successfully from the data of creep fatigue tests on those superalloys at two temperatures, 650 °C and 760 °C. We found suitable microstructure sensitive constants in a lifing model
Fly ash and zinc slag blended geopolymer: Immobilization of hazardous materials and development of paving blocks
Get PDFThe potential for practical application of fly ash, zinc slag and their blends for geopolymer synthesis at ambient
temperature have been investigated in this paper. Fly ash is an alumino-silicate byproduct suitable for geopolymer reaction, but its low reactivity at ambient condition is the restriction of its bulk utilization. Above limitation can be overcome by blending with zinc slag (ZS). Additionally, ZS contains heavy and toxic metals (Pb,
Zn, Cr, Cd, As), which can be stabilize in Al-Si based geopolymer network structure. Isothermal conduction
calorimetry (ICC) is used to monitor the geopolymer reaction with time. Slag rich specimens are characterized
with higher rate of reaction with augmented peak. The mineralogy and microstructure of the geopolymers have
been examined through X-ray diffraction and scanning electron microscope. The detected chief reaction product
is N-(C)-A-S-H and C-(N)-A-S-H1 type hydrated gel. Continual improvement of compressive strength of the
geopolymers with increasing slag content is explained with higher degree of reaction, formation of more reaction products and development of compact microstructure. According to toxicity characteristic leaching procedure (TCLP), toxic metals leaching is within permissible limit. Paver blocks using 40−80 wt% ZS has been developed, which meets IS 15,658: 2006 standard and comply with US-EPA specification
On mechanical activation of glauconite: Physicochemical changes, alterations in cation exchange capacity and mechanisms
No full textMechanical activation (MA) of glauconite [(K,Na,Ca)(Fe3+,Al,Mg,Fe2+)2(Si,Al)4O10(OH)2] has been investigated to improve its cation exchange capacity (CEC), an impediment for its direct use as nutrients (agro-mineral), notably potassium. Glauconite is mechanically activated using planetary ball milling for varying lengths of time up to 240 min. Milling induces time dependent physicochemical changes in terms of particulate characteristics (morphology, particles size distribution, geometrical and BET specific surface area), structure (crystallite size and strain; –OH/H2O bonding) and surface charge (zeta potential). It is possible to tailor the CEC of glauconite with MA. A remarkable improvement (30-fold!) in the CEC of K+ ions is possible. The effect of milling time on the exchange behaviour is ion-specific. Plausible mechanisms of cation exchange are presented in terms of the chemical nature of the ions involved and the physicochemical changes. Lastly, MA approach is compared with reported methods of potassium recovery; its superiority as a green option is underlined
Effect of compositional elements and processing routes on structural and thermal response in Fe-based metallic glasses
No full textThe effect of varying thickness on structure and thermal properties is investigated in Fe-B-Nb and Fe-B-Si-Nb glassy alloy systems with the addition of different Nb and Co content, respectively. Accordingly,four alloys with the nominal compositions of Fe76-xB18Nb6+x (x = 0, 2) and (Fe1-yCoy)72B12Si12Nb4 (y = 0,0.5) are processed in the forms of ribbon and rod. All alloys of ribbons represent amorphous structure,while those of rods explain the crystalline structure with the exception of heteromorphous structure for
Co added alloy. The Nb addition causes about same glass transition temperature (Tg) but increases crystallization onset (Tx), resulting in a wider supercooled liquid region (deltaTx =Tx-Tg). Moreover, Nb also improves glass forming ability (GFA) with more free volume generation and higher structural relaxation exothermic heat (delta H0). The Co addition also improves free volume generation and higher delta H0 for ribbon, but lower amount free volume generation in bulk alloys (rod) than ribbon
Hydrometallurgical processing of waste multilayer ceramic capacitors (MLCCs) to recover silver and palladium
No full textPresent paper reports an application oriented approach to recover precious metals such as silver (Ag) and palladium (Pd) from multilayer ceramic capacitors (MLCCs) of waste printed circuit boards (PCBs). These capacitors are being widely used in modern electronic gadgets to provide advance features as well as to enhance their performance. Due to the generation of large amount of e-waste as well as the loss of precious metals, a sincere R&D effort has been made to develop a process for the recovery of Ag and Pd from waste MLCCs. Initially, the MLCCs were depopulated from the PCBs by de-soldering using thermal treatment. Further, the depopulated material was pulverised to get homogeneous fine powder of MLCCs, which contained 0.14% Pd, 1.08% Ag, 1.76% Cu and 11.1% Ni. First of all Ni was removed/recovered selectively using two stages of leaching at optimized condition i.e. 2 M HCl, temperature 75 °C and pulp density 100 g/L. The obtained leached residue was washed, dried and further leached to get 99.99% Ag and Pd both in solution using 4 M HNO3, temperature 80 °C, pulp density 100 g/L and mixing time 1 h. From the obtained leach liquor, salt of Ag (purity 99.99%) was selectively recovered/precipitated using KCl. Further, Cu was extracted from the Ag depleted solution using LIX 84IC leaving Pd in the raffinate, which was evaporated to get pure Pd salt. The developed flow-sheet has potential to be commercialized after scale up trials
Separation of thorium and uranium from xenotime leach solutions by solvent extraction using primary and tertiary amines
No full textThis study addressed the development of a continuous countercurrent extraction-scrubbing-stripping technique
using a mixture of primary and tertiary amines as an effective extractant for both thorium (Th) and uranium (U)
to simultaneously separate them from the leach solutions of xenotime concentrate from the Yen Phu mine (Vietnam). Systematic studies determined the optimum parameters of the separation, including the optimum concentrations of the mixture of the primary amine (N1923) and tertiary amine (tri-n-octyl amine), the optimum acidity (pH) of the feed liquor (Yen Phu xenotime leachate), the optimum contact time between phases for extraction, scrubbing and stripping processes, and the most suitable stripping reagent mixture. Using the optimum parameters, the optimum stage number and phase volumetric ratio for extraction, scrubbing, and stripping processes were calculated using the calculus method based on the law of matter conservation. The flow rates of both phases for extraction, scrubbing, and stripping were determined from the results of these studies and calculations. To optimize the separation of uranium and thorium from the Yen Phu xenotime leachate, countercurrent simulations of extraction, scrubbing and stripping were done in a series of mixer-settler units. The results indicated that the selective separation of Th and U with almost no loss of rare earths (REs) and a minimal contamination of iron were obtained. The continuous countercurrent extraction-scrubbing-stripping technique shows potential applications in the commercial separation of Th and U from RE leachate after tests using a sequence of mixer-settler units on a pilot scale
Effect of Re-normalizing and Re-tempering on Inter-critical Heat Affected Zone(S) of P91B Steel
No full textThe novel perspective of this paper was to restore the grain boundary (GB) hardening effect in inter-critical heat affected zone (ICHAZ) of boron modified P91 steel (P91B). To achieve this, samples of the base metal (BM) of P91B steel were thermally simulated by Gleeble followed by post-weld heat treatment (PWHT) and were further re-normalized and re-tempered. With such heat treatment, four different ICHAZ(s) were reproduced. These ICHAZ(s) were subjected to impression creep testing. As impression creep testing brings local deformation, the suitable characterization technique was electron back scatter diffraction (EBSD) for in-depth investigations of microstructural deformation. High creep deformation was observed for simulated ICHAZ followed by PWHT-ICHAZ due to GB softening. Whereas, the least deformation was observed for re-normalized and re-tempered ICHAZ(s) restoring GB hardening. In this respect, type IV cracking was avoided by re-normalizing and re-tempering in P91B steel. This phenomenon was further correlated with the impression creep curves of each ICHAZ with BM