• Journal of the Korean earth science society
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• v.35 no.4
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• pp.259-266
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• 2014

This study was carried out to find an environmental friendly and effective way to leach Au and Ag from scrap of Printed Circuit Boards (PCBs) using sodium-hypochlorite solution. In an EDS analysis, valuable metals such as Cu, Sn, Sb, Al, Ni, Pb and Au were all found in PCBs. The highest leaching rates obtained were 1% of pulp density with a chlorine:hypochlorite of 2:1 and a concentration of NaCl at 2M. The highest Au recovery was observed with the addition of sodium metabisulfite to make a 3M solution. It is confirmed that the leaching agent (chlorine-hypochlorite) could effectively leach Au and Ag from Printed Circuit Boards (scrap parts) and the additive reagent sodium metabisulfite could easily precipitate Au from the chlorine-hypochlorite solution.

• Economic and Environmental Geology
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• v.43 no.5
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• pp.523-528
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• 2010

With the financial crisis from USA had negative impacts on the real economy, base metals price on LME was downward in 4 quarter of 2008. Following the deepest global downturn in recent history, economic growth solidified and broadened to advanced countries and simultaneously the price of base metal on LME showed a rising curve over 2009. There are three factors supported an upward tendency of base metal's price. The First factor is the US economy recovery, the second factor is the weak dollar, the third factor is the chinese base metal demand. Among the factors, the last one is a major factor. Therefore, this study analyze the factor of the movement of price of base metal with linear regression analysis. The result of analysis show that the chinese GDP growth has effect on the recent upward base metal price. Despite the result, the upward movement is difficult to be sustained without the full recovery of advanced economies.

• Resources Recycling
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• v.18 no.5
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• pp.44-51
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• 2009

Fundamental study has been made on the recovery of copper from the electronic scrap by hydrometallurgical process. Nitric acid was used as a leaching agent to dissolve the metals such as Cu, Sn, Pb, Fe etc. from the crushed electronic scraps. TBP was employed to extract nitric acid from the strong nitric acid leaching solutions and to reclaim nitric acid. From the experimental results, Cu was effectively leached by 3.0-4.0 M nitric acid. And 95% of nitric acid in the leaching solution was extracted by 60% TBP, and 98% of nitric acid was stripped from the loaded organic phase by distilled water and it was possible to reuse as a leaching agent.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.414-417
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• 2014

LED scraps consisting of highly crystalline GaN and their leaching behavior are comprehensively investigated for hydro-metallurgical recovery of rare metals. Highly stable GaN renders the leaching of the LED scraps extremely difficult in ordinary acidic and basic media. More favorable state can be obtained by way of high temperature solid-gas reaction of GaN-$Na_2CO_3$ powder mixture, ball-milled thoroughly at room temperature and subsequently oxidized under ambient air environment at $1000-1200^{\circ}C$ in a horizontal tube furnace, where GaN was effectively oxidized into gallium oxides. Stoichiometry analysis reveals that GaN is completely transformed into gallium oxides with Ga contents of ~73 wt%. Accordingly, the oxidized powder can be suitably leached to ~96% efficiency in a boiling 4 M HCl solution, experimentally confirming the feasibility of Ga recycling system development.

• Resources Recycling
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• v.20 no.4
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• pp.58-64
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• 2011

Recovery of novel metals such as Au, Ag and Ni from wastes PCB was investigated by slag treatments. The CaO-$Al_2O_3$(-$SiO_2$) and CaO-$SiO_2$-$CaF_2$ slags were employed in the present study. The PCB/Cu ratio is recommended to be lower than unity. The use of CaO-$SiO_2$-$CaF_2$ slag provided the more higher yield of Au, Ag and Ni than the CaO-$Al_2O_3$(-$SiO_2$) slag did, which was mainly due to the lower melting point and the viscosity of $CaF_2$-containing slag. The terminal descending velocity of metal droplets in the slag phase increased with decreasing slag viscosity.

• Resources Recycling
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• v.9 no.3
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• pp.22-28
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• 2000

A study on the recovery of gallium from zinc residues is carried out by alkali leaching using NaOH. The results show that in case of alkali leaching of zinc residues, Zn, K and Si are mainly leached out and Fe and other base metals are scarcely leached out, which results in that gallium is easily recovered by solvent extraction. The leaching efficiency of gallium increases with increasing alkali concentration and solid density. Especially, alkali consumption is considerably reduced by washing the zinc residues with water before leaching in order to eleminate the soluble zinc compounds. The gallium from zinc residues is found to be leached out with a recovery of 80% or higher for 2hrs leaching with 1~1.25 M/L NaOH solution and solid density 333 g/L at $25^{\circ}C$.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.3
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• pp.175-182
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• 2022

Heavy metals can be intentionally or unintentionally introduced into plastic food utensils, containers, and packaging (PFUCP) as additives or contaminants, which can be ingested with food by humans. Here, seven-heavy metals (lead, cadmium, nickel, chromium, antimony, copper, and manganese) with toxicity concerns were selected, and risk assessment was done by establishing their migration from 137 PFUCP products made of 16 materials distributed in Korea. Migration of heavy metals was examined by applying 4% acetic acid as a food simulant (70℃, 30 minutes) to the PFUCP products. Inductively coupled plasma mass spectrometry (ICP-MS) was employed for the analysis of migrated heavy metals, and the reliability of quantitative results was confirmed by checking linearity, LOD, LOQ, recovery, precision, and expanded uncertainty. As a result of monitoring, heavy metals were detected at a level of non-detection to 8.76 ± 11.87 ㎍/L and most of the heavy metals investigated were only detected at trace amounts of less than 1 ㎍/L on average. However, antimony migrated from PET products was significantly higher than other groups. Risk assessment revealed that all the heavy metals investigated were safe with a margin of exposure above 311. Collectively, we demonstrated that heavy metals migrated from PFUCP products distributed in Korea appear to be within the safe range.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.176-179
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• 2001

A simple cold pressing procedure which allows shear deformations on sheet metals is proposed by designing dies with grooves and applied to aluminum 3003 sheets. shear deformation led to the formation of preferred orientation along <100>//RD, and the effect of initial tortures on the formation of shear textures was also studied Rectangular shaped dislocation cells formed in the deformed microstructure and boundaries of dislocation cells gradually rounded with the increased plastic strain. Upon subsequent annealing textures inherited deformation textures. Recrystallized grains consisted of a large number of fully recovered subgrains with well defined boundaries which persisted even after annealing at a higher temperature.

• Bulletin of the Korean Chemical Society
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• v.23 no.7
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• pp.943-947
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• 2002

The two reactions between iron ion (Fe3+ ) and o-chlorophenylfluorone (o-CPF) and copper ion (Cu2+ ) and o-CPF are sensitive at pH 6 in the presence of Triton X-100. We have determined the formation constants of the complexes by the spectral correction technique. Because of the poor selectivity of o-CPF to metals, the competition coordination of only the iron ion from the Cu-o-CPF complex was found and applied to the selective detection of iron traces by the Selective Competition Coordination Determination (SCCD) approach.The analysis of several samples shows that the relative standard deviations are less than 5.0% and the recovery of iron ions between 94.5% and 106%.

• Resources Recycling
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• v.1 no.1
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• pp.37-43
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• 1992

The submerged injection smelting process was performed to recover Zn and Pb from steel dust throuth vaporization and to investigate the effect of temperature, slag composition, injection time, gas flow rate, etc. on the recoveries of valuable metals. The results show that vaporation rates of zinc and lead increased at higher temperture and higher moral ratio of ferrous to ferric oxides. In the initial stage of submerged injection of nitrogen gas, the molten slags of the dust have high value of molar ratio of $Fe^{2+}$/$Fe^{3+}$ and hence zinc and lead can be effectively recovered.