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Opportunities for an en-route to polymer inclusion membrane approach from conventional hydrometallurgical recycling of WPCBs: a mini-review
No full textWaste printed circuit boards (WPCBs) are an essential part of any electric and electronic equipment (EEE). A plethora of valuable metals such as gold, palladium, silver, and copper along with the presence of hazardous metals like cadmium, lead and mercury is a good motivation for designing an effective recycling process for WPCBs. The pyrometallurgical route shows environmental challenges like the formation of toxic gases such as dioxins and furans. Overtaking the limitations of the pyrometallurgy route, the hydrometallurgical route comes into existence with very low capital cost, low gas generation, and an environmentally friendly process. This article reviews the conventional hydrometallurgical processes followed en route to newer polymer inclusion membrane (PIMs) routes for the treatment of WPCBs to recover trace metals. The conventional hydrometallurgical approaches such as cementation, ion exchange, and solvent extraction are efficient in recovering metals from WPCBs. However, the purity of recovered metals is also compromised by metals of lower concentrations. PIMs are found as low-cost processes for the extraction of valuable metals from WPCBs leach liquor as this process combines extraction and stripping steps. Additionally, this process is a nature-friendly, chemically stable processing route for the extraction of heavy and toxic metallic elements
Effect of Annealing Time on Coating Microstructure, Frictional and Electrochemical Behavior of Galvannealed Interstitial-Free Steel
No full textThe present study deals with the effect of isothermal holding time (10, 20, and 30 s) at a fixed annealing temperature of 500 degrees C on the formation of various Fe-Zn intermetallic phases during galvannealing treatment of a galvanized (GI) interstitial-free steel, and its correlation with the friction behavior determined by scratch test and electrochemical behavior in a freely aerated 3.5 wt. % NaCl solution. Pure Zn coating in GI specimen transforms to the various Fe-Zn intermetallic phases consisting of overlay zeta (zeta) phase with elongated rod type morphology, compact delta (delta) phase as well as a very thin layer of gamma (Gamma) phase at the coating-substrate interface during isothermal annealing treatment of the GI sheet. The zeta phase has been noticed to get consumed by the more compact delta phase and increase in thickness of the thin Gamma phase layer at the coating-substrate interface as iron content in the coating increases with an increase in galvannealing holding time. The galvannealed (GA) coating prepared at a galvanneal time of 30 s has the lowest coefficient of friction (COF similar to 0.26) as compared to 20 s (COF similar to 0.31) and 10 s (COF similar to 0.36), and the lowest corrosion rate (CR similar to 0.184 mm/y) as compared to 20 s (CR similar to 0.214 mm/y) and 10 s (CR similar to 0.227 mm/y). The dominance of compact and crater-free coating surface morphology along with the lowest zeta to delta (zeta/delta) phase fraction results in the lowest COF as well as the lowest corrosion rate of the GA coating prepared at a galvanneal time of 30 s
Potential hydrometallurgical processes to recycle metals from discarded personal computer
Get PDFRapid technological modernization has accelerated the replacement of older electronic goods with newer ones, which has led to the generation of huge quantities of discarded electronic items at their end-of-life, known as electronic waste (e-waste). The growing quantity of e-waste has become a major threat to the society as well as the environment. On the other hand, e-waste contains several valuable metals and materials of high economic value, which compels researchers to work in the area for secondary resources for metal recovery. Metal recovery from such secondary resources will
not only preserve the primary resources but also reduce the loss of valuable metals/materials, protect the environment from their hazardous effects as well as reduce the demand-supply gap of metals up to some extent. In view of the above, the present study is focused on the possible effort to figure out a variety of metals present in the component of waste personal computers (WPCs) as well as different recycling processes implemented for the efficient recovery of metals
Strategies for Recycling of Primary and Secondary Resources for Germanium Extraction
No full textIn this review, availability of germanium in primary and secondary resources and its recovery from these resources are presented. With nearly 40% germanium consumed in fiber optics and scarcity of resources, the global consumption outplays the primary production. Germanium exists as a substituted element in zinc sulfide matrix of lead-zinc sulfides and lignites. Nearly 60% of the germanium supply is met by zinc refining residues, and about 20-30% of germanium is produced from coal and its by-products. Germanium recovery from various resources such as zinc plant residues, coal and coal plant waste, spent optical fibers, and copper flue dust has been examined. Bioleaching was exploited by few researchers to extract germanium from zinc sulfides, sulfide tailings, jarosite, coal fly ash, and flue dust. This review covers the various work carried out by different chemical separation processes, viz., chemical precipitation, solvent extraction (SX), ion exchange (IX), and membrane processes, as well as biological approaches
Ionic Liquids-Assisted Solvent Extraction of Precious Metals from Chloride Solutions
No full textIncreasing applications of precious metals (PMs: Au, Ag and platinum group metals) and the growing demand is a matter of great concern for supply security. The hydrometallurgical route through chloride-based leaching has been considered as the most promising method to recover almost all the metals. However, separation of metal-chloro complexes formed during the leaching is difficult to achieve because of similar properties of these complexes. Among the methods developed to extract and separate the metal-chloro complexes, ionic liquid (IL)-based solvent extraction has been recognized as one of the most promising approaches. The ionic liquids possess unique characteristics of 'greener,' 'designer' and 'highly effective' solvents. This paper reviews extraction and separation of PM-chloro complexes by ionic liquids. Mechanisms and IL role in the process, along with merits and drawbacks of IL-assisted solvent extraction are discussed comprehensively. Effects of operational conditions, stripping, and regeneration of the loaded ILs and possible use of ionic liquids in other separation methods are also presented. A flow-sheet for separation of PM-chloro complexes has been developed as a part of basic process approach using ionic liquids. In addition, future directions for the development and application of IL-assisted solvent extraction in separation of precious metals are provided
Bubble size analysis in a two-phase countercurrent flow in the narrow rectangular column
No full textThe flow of bubbles in a two-phase system has great implications in chemical, petrochemical, and biochemical applications. This work enunciates the measurement of bubble size distribution and bubble aspect ratio in three-different axial zones in the countercurrent flow mode with a gas and liquid velocity range of 0.044-0.321 and 0.019-0.058 m/s, respectively. Bubble size is measured by the photographic technique. The bubble aspect ratio and bubble size distribution results reveal that the impact of gas and liquid velocities is significant on the Sauter mean bubble size. The Sauter mean bubble size increases as the gas velocity increases, whereas it decreases with the liquid velocity. The Sauter mean bubble diameter ranges from 2.65 to 6.16 mm. The distribution of bubble sizes follows the LogLogistic probability density function. In addition, a correlation is also proposed for the interpretation of bubble diameter in terms of Reynolds number and Froude number. The bubble aspect ratio changes with axial zones and gas and liquid velocities. Experiments reveal that the bubble aspect increases with liquid velocity while decreasing with gas velocity and axial zones. The bubble aspect ratio correlations are developed in terms of Eotvos and Reynolds numbers. The present results will be helpful for the process intensification of bubble-aided two-phase flow applications
Spectral conversion by silicon nanocrystal dispersed gel glass: efficiency enhancement of silicon solar cell
No full textAlongside the quest for new materials for development of next-generation solar cells, increasing the efficiency of the existing crystalline silicon-based photovoltaic module is of paramount importance. In this work we prepared a silicon nanocrystal (NC) dispersed gel-glass and used it as a luminescent down shifting material to enhance the efficiency of a conventional solar cell module. The synthesized gel-glass efficiently converts the unutilized high energy UV photons of the solar spectrum to blue-green photons and renders them amenable for effective carrier generation. An exceptionally high quantum yield (42.8%) of photon down conversion could be achieved with the luminescent silicon NCs. Following the insertion of the NC embedded gel-glass, the relative photon conversion efficiency and the short circuit current of the solar cell were found to increase by 6.48% and 4.2%, respectively. Further improvement of solar cell efficiency using this material could be achieved by optimized design and deposition and by optimizing the formation parameters of the gel-glass
Magnetic Anisotropic Behaviour of CRGO Steels for Quality Assessment
No full textAn investigation on quality assessment of cold rolled grain oriented (CRGO) steels is carried out in this research with
the supports of microstructure, texture and magnetic property evaluation in one virgin and three service exposed CRGO sheets. The microstructure evolution reveals oxidation, precipitation and widening at grain boundary of service exposed samples, justifying structural deterioration with service exposure. Additionally, the misorientation of Goss grains is found with higher angle range for service exposed (7°–31°) than virgin (6°–17°) CRGO. The service exposed CRGO sheets are also examined with poor magnetic properties of high core loss compared to virgin one. The non-destructive evaluation explains the deterioration of magnetic anisotropy in service exposed CRGO sheets, which would be beneficial for the rapid inspection of CRGO quality. The quality degradation of CRGO sheet is justified through the lowering of magnetic anisotropy factor and Steinmetz exponent. This research outcome would be the baseline to transformer manufacturer for the separation of inferior
quality CRGO sheets amongst good one
Effect of quenching and partitioning time on microstructure and mechanical properties of low carbon micro-alloyed steel
No full textIn this present study, quenching and partitioning (Q&P) process was applied to rolled low carbon microalloyed steels. The Effect of partitioning time after quenching below martensite start temperature (Ms) on microstructure and mechanical properties is investigated. The resulting microstructure was investigated by using optical microscopy, Scanning Electron microscopy and X-ray diffraction techniques. The mechanical properties are evaluated. The microstructure consists of lath martensite, temper- martensite and retained austenite. The retained austenite is identified by XRD analysis. The tensile strength of Q&P processed steel significantly increases than rolled sample, but ductility decreases. The quenching below Ms temperature and portioning for 10 min shows a good strength and ductility combination. Copyright (c) 2022 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the Symposium on Failure and Preventive Maintenance of Machineries 2022