• Resources Recycling
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• v.7 no.3
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• pp.27-35
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• 1998

EAF dust generated from electric arc steelmaking process is classified as "hazardous" materials by tbe environmental regulation because of the existence of water leachable heavy metals such as Fe, Zn, Pb, and Cd. However, Fe and Zn among t the elements in the dust can be recovered to high valuable materials by applying a proper process. Therefore, in order to study t the possibility of recovery of iron from EAF dust, the effect oE carbon content and basicity, of synthesized EAF dust on the reduction rate of iron oxide was studied. Experimental results are as follows: TIle softening and melting temperature of the slag w was illcreased with increasing carbon addition amount [or carbon reduction eqUIvalent. At the carbon addition amount of 100% for carbon reduction equivalent and basicity of 1.7, reduction rate of $Fe_2O$ in the slag was the highest. The reaction order fur reduction of $Fe_2O$ by carbon was nearly first order.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.31-36
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• 2005

It is well known that PCB (Printed Circuit Board) is a complex mixture of various metals mixed with various types of plastics and ceramics. In this study, high temperature pyre-metallurgical process was investigated to extract valuable metallic components from the PCB scrap. For this purpose, PCB scrap was shredded and oxidized to remove plastic materials, and then, quantitative analyses were made. After the oxidation of the PCB scrap, $30.6wt\%SiO_2,\;19.3wt\%Al_2O_3\;and\;14wt{\%}CaO$ were analyzed as major oxides, and thereafter, a typical composition of $32wt\%SiO_2-20wt\%Al_2O_3-38wt{\%}CaO-10wt\%MgO$ was chosen as a basic slag system for the separation of metallic components. Moreover a size effect of crushed PCB scrap was also investigated. During experiments a high frequency induction furnace was used to melt and separate metallic components. As a result, it was found that the size of oxidized PCB scrap was needed to be less 0.9 m to make a homogeneous liquid slag and to recycle metallic components over $95\%$.

• Resources Recycling
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• v.20 no.2
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• pp.30-44
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• 2011

This review describes the involvement of different microorganisms for the recovery of uranium from the ore. Mainly Acidithiobacillus forrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans are found to be the most widely used bacteria in the bioleaching process of uranium. The bioleaching of uranium generally follows indirect mechanism in which bacteria provide the ferric iron required to oxidize $U^{4+}$. Commercial applications of bioleaching have been incorporated for extracting valuable metals, due to its favorable process economics and reduced environmental problems compared to conventional metal recovery processes such as smelting. At present the uranium is recovered through main bioleaching techniques employed by heap, dump and in situ leaching. Process development has included recognition of the importance of aeration of bioheaps, and improvements in stirred tank reactor design and operation. Concurrently, knowledge of the key microorganisms involved in these processes has advanced, aided by advances in molecular biology to characterize microbial populations.

• Resources Recycling
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• v.26 no.5
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• pp.85-96
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• 2017

In this study, we tried to select a slag system capable of pyro-metallurgical process through analysis of sludge generated from PCB plating and etching process solution. Based on this, the possibility of extracting valuable metals in the sludge was studied by experimental and thermodynamic approaches. The sludge was dried at $100{\sim}500^{\circ}C$ and the morphology, chemical composition and phase of the sludge were analyzed. The possibility of pyro-metallurgical process of sludge was investigated through thermodynamic approach using FactSage software.

• Resources Recycling
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• v.30 no.6
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• pp.36-42
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• 2021

Spent lithium-ion batteries are treated by reduction-smelting at high temperatures to recover valuable metals. Solvent extraction and precipitation of the HCl leaching solution of reduction-smelted metallic alloys resulted in a filtrate containing Ni(II) and a small amount of Si(IV). Adsorption and precipitation experiments were conducted to recover pure Ni(II) compounds from the filtrate. Si(IV) was selectively loaded onto polyacrylamide, but this method did not efficiently filter the solution due to an increase in viscosity. The addition of Na₂CO₃ as a precipitant to the filtrate led to the simultaneous precipitation of Ni(II) and Si(IV). However, it was possible to recover nickel oxalate with a purity higher than 99.99% by selectively precipitating Ni(II) with the addition of Na₂C₂O₄ as a precipitant.

• Journal of Digital Convergence
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• v.19 no.3
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• pp.303-311
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• 2021

The accessories growth according to the changes in each era and of course, jewelry processing technology has also improved, but in modern times, the frequency of use of jewelry has decreased, and it has been neglected compared to crafting and metal-related technologies. The beauty of crafted jewelry still remains, there are many problems to cover many age groups due to valuable and design problems. Accordingly, this researcher intends to conduct research to inform the formative beauty and value of processed jewelry. Jewelry designby mainly applying lines during the shaping of the jewelry cutting surface. Prior to the design, a theoretical approach to the design case and jewelry processing literature, and based on this, jewelry design applied in the form of jewelry cutting. This study is expected to promote the vitalization of jewelry research, which is currently marginalized in the field of precious metals, and to develop a number of designs using jewelry.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.1
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• pp.43-63
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• 2022

The aim of this review is to communicate some essential knowledge of the underlying mechanism of the corrosion of structural containment alloys during molten salt reactor operation in the context of prospective online monitoring in future MSR installations. The formation of metal halide species and the progression of their concentration in the molten salt do reflect containment corrosion, tracing the depletion of alloying metals at the alloy salt interface will assure safe conditions during reactor operation. Even though the progress of alloying metal halides concentrations in the molten salt do strongly understate actual corrosion rates, their prospective 1^st order kinetics followed by near-linearly increase is attributed to homogeneous matrix corrosion. The service life of the structural containment alloy is derived from homogeneous matrix corrosion and near-surface void formation but less so from intergranular cracking (IGC) and pitting corrosion. Online monitoring of corrosion species is of particular interest for molten chloride systems since besides the expected formation of chromium chloride species CrCl₂ and CrCl₃, other metal chloride species such as FeCl₂, FeCl₃, MoCl₂, MnCl₂ and NiCl₂ will form, depending on the selected structural alloy. The metal chloride concentrations should follow, after an incubation period of about 10,000 hours, a linear projection with a positive slope and a steady increase of < 1 ppm per day. During the incubation period, metal concentration show 1^st order kinetics and increasing linearly with time^1/2. Ideally, a linear increase reflects homogeneous matrix corrosion, while a sharp increase in the metal chloride concentration could set a warning flag for potential material failure within the projected service life, e.g. as result of intergranular cracking or pitting corrosion. Continuous monitoring of metal chloride concentrations can therefore provide direct information about the mechanism of the ongoing corrosion scenario and offer valuable information for a timely warning of prospective material failure.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.2
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• pp.61-67
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• 2022

A metal salt solution was prepared from valuable metals (Ni, Co, Mn) recovered from a scrap of waste lithium secondary batteries, and an NCM811 precursor was synthesized from the solution. The effect on precursor formation according to reaction time was confirmed by SEM, PSA, and ICP analysis. Based on the analysis results, the electrochemical properties of the synthesized NCM811 precursor and the commercial NCM811 precursor were investigated. The Galvano charge-discharge cycle, rate performance, and Cycle performance were compared, and as a result, there was no significant difference from commercial precursors.

• Resources Recycling
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• v.33 no.4
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• pp.22-28
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• 2024

Waste PCBs contain a large amount of valuable resources, including copper, and technology to recover them is constantly being developed. Generally, to recycle waste PCBs, a physical pretreatment process such as shredding and crushing is required. However, during this stage, the loss rate of metals is high and the sorting efficiency is low, indicating a need for a more efficient recycling pretreatment process. In this study, a high-temperature milling process, which simultaneously employs heat treatment and ball milling, was utilized to efficiently recover copper from waste PCBs. An experiment was conducted at 350 ℃ with milling time, milling speed, and the weight of the balls as variables. The results showed a copper recovery rate of over 90% under the conditions of a ball weight of 500 g, a milling speed of 70 RPM, and a milling time of 5 hours. The purity of the recovered copper was approximately 93%, and through post-processing after the high-temperature milling process, the feasibility of reusing the recovered copper as a high-purity material was confirmed.

• Journal of Microbiology and Biotechnology
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• v.34 no.9
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• pp.1877-1889
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• 2024

Rhamnolipid (RL) is renowned for its efficacy in bioremediating several types of organic and metal contaminants. Nevertheless, there has been a scarcity of studies specifically examining the relationship between this substance and metals, especially in terms of their impact on RL formation and the underlying interaction processes. This study addresses this gap by investigating the RL mechanism in Cr (VI) remediation and evaluating its effect on RL production in Pseudomonas aeruginosa RW9. In this study, P. aeruginosa RW9 was grown in the presence of 10 mg l^-1 Cr (VI). We monitored RL yield, congeners distribution, and their ratios, as well as the transcriptional expression of the RL-encoded genes: rhlA, rhlB, and rhlC. Our results revealed that RL effectively reduced Cr (VI) to Cr (III), with RL yield increasing threefold, although with a slight delay in synthesis compared to control cells. Furthermore, Cr (VI) exposure induced the transcriptional expression of the targeted genes, leading to a significant increase in di-RL production. The findings confirm that Cr (VI) significantly impacts RL production, altering its structural compositions and enhancing the transcriptional expression of RL-encoded genes in P. aeruginosa RW9. This study represents a novel exploration of Cr (VI)'s influence on RL production, providing valuable insights into the biochemical pathways involved and supporting the potential of RL in Cr (VI) bioremediation.