• Resources Recycling
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• v.21 no.3
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• pp.56-64
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• 2012

It is generally well known that PCB (Printed Circuit Board) is an electric component assembled by various metals mixed with plastics and ceramics. Accordingly, it is very important to extract metallic components from used PCBs from the point of view of recycling of used resources as well as an environmental protection. In this paper, patents and paper on the recycling technologies of PCB were analyzed. The range of search was limited in the open patents of USA (US), European Union (EP), Japan (JP), Korea (KR) and SCI journals from 1980 to 2011. Patents and journals were collected using key-words searching and filtered by filtering criteria. The trends of the patents and journals was analyzed by the years, countries, companies, and technologies.

• Journal of the Mineralogical Society of Korea
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• v.23 no.4
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• pp.331-346
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• 2010

This study was carried out to leach valuable metals from galena using indigenous bacteria with no optimum pH conditions at room temperature. Even in these conditions, the rod-shaped indigenous bacteria, ranging from $0.4{\times}0.2{\mu}m$ to $0.5{\times}1.7{\mu}m$, were attached to the surface of the galena. For the 19 days of the bioleaching experiment, the content of Ph, Fe, Zn ions was found to be 347, 222 and 1.7 times higher than that of the control leaching agent, respectively. Numerous hexagonal column crystals were observed on the surface of galena. Those crystals may be formed from the biooxidation of galena by the indigenous bacteria. XRD analysis showed the peaks of anglesite observed in the bioleached galena. It is expected that more valuable elements can be leached out of the galena, if the bacteria is used under optimum pH and temperature conditions in future bioleaching experiments.

• Resources Recycling
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• v.16 no.2 s.76
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• pp.63-76
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• 2007

Typical examples as unrecycled materials in Korea were Zinc from the electric arc furnace dust (EAF Dust), and Moiybdenium and Vanadium from the desulfurizing spent catalyst of petrochemical industries. In the otherwise, though recovery of valuable metals from the waste electronic scrap such as printed circuit boards (PCBs) and platinum group metals (PGM) from the waste automobile catalyst have been interesting issues, it is difficult to collect the exact informations or statistics on their material flow system. In this article, The current domestic research trends for unrecycled or less recycled materials have been reviewed, and material flow and recycling technologies on the desulfurizing spent catalyst were surveyed.

• Resources Recycling
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• v.7 no.5
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• pp.46-51
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• 1998

A study has been on the recovery of nitric acid and valuable metals such as Fe, Cu, Sn, Pb, from spent nitric etching solutions. The effects of extractant of extractant type, concentrations, phase raios and selectivity from Fe, Cu, Sn, Pb on nitric acid extraction were studied. The results showed that TBP as an extractant for recovering of nitric acid was more effective than Alamine336, and the optimal concentration of TBP was found to be 60~70% of organic phase. Also, the nitric acid were only extracted by TBP from the spent etching solutions and the heavy metals such as Fe, Cu, Sn, Pb were not extracted above 0.1N nitric acid in spent etching solutions, From the analysis of McCabe-Thiele diagram, the extraction of 95% nitric acid is attained at a ratio of O/A=3 with five stages by 60% TBP and the stripping of 98% nitric acid from 80 g/l nitric acid in organic phase is attained at a ratio of O/A=1 with four stages by distilled water.

• Journal of Microbiology and Biotechnology
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• v.28 no.2
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• pp.323-329
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• 2018

In Escherichia coli, the transcription of genes related to metal homeostasis is activated by the presence of target metals. The promoter regions of those genes can be fused with reporter genes to generate whole-cell bioreporters (WCBs); these organisms sense the presence of target metals through reporter gene expression. However, the limited number of available promoters for sensing domains restricts the number of WCB targets. In this study, we have demonstrated an alternative method to generate novel WCBs, based on the notion that since the sensing mechanisms of WCBs are related to metal transportation systems, their properties can be modulated by disrupting metal homeostasis. Mutant E. coli strains were generated by deleting the znt-operon genes zntA, which encodes a zinc-export protein, and zntR, which encodes a znt-operon regulatory protein, to investigate the effects on the metal-sensing properties of WCBs. Deletion of zntA increased the sensitivity but abolished the selectivity of cadmium-sensing WCBs, whereas arsenic-sensing WCBs gained sensitivity toward cadmium. When zntR was deleted, cadmium-sensing WCBs lost the ability to detect cadmium, and this was recovered by introducing exogenous zntR. In addition, the metal-binding site of ZntR was genetically engineered to modulate metal selectivity. This study provides a valuable platform for the development of novel E. coli-based WCBs.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.5
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• pp.567-575
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• 2017

To understand the geochemical characteristics of Gomso Bay, which features extensive Manila clam, we measured various geochemical parameters, organic matter, and trace metals (Cu, Cd, Pb, Zn, Cr, Hg, As and Fe) of intertidal and subtidal surface sediments in 2011. The surface sediments consisted of sedimentary facies including gravel (0.21%), sand (61.1%), silt (32.1%), and clay (6.5%). The chemical oxygen demand (COD) and acid volatile sulfide (AVS) values in most areas were below sediment quality criteria (COD, $20mg/g{\cdot}dry$; AVS, $0.2mg/g{\cdot}dry$). Trace metals in the surface sediments were below pollution thresholds, except for As (morderately polluted). Sediment quality was evaluated using the trace metal pollution load index (PLI) and ecological risk index (ERI), which showed that sediments were generally not polluted and at low risk; however, values along the outer bay were higher. We expect these results will be valuable for sustainable aquaculture prodution and environmental management in Gomso Bay.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.633-637
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• 2001

Oil fly ash is known as one source of raw materials from which vanadium and nickel metals can be recovered. The current recovery process of valuable metals from oil fly ash is mainly the hydrormetallurgy one. Nevertheless, a great amount about 50~80%, of unburned carbon remains as byproduct after hydrormetallursy process. In Taiwan, if hydrormetallursy processes have proceeded, it can be estimated that the annual production of unburned carbon is 25 thousand tons. From the viewpoint of resource recycling, this study is a preliminary study and investigates in recovery of sub micron- graphitized carbon from unburned carbon by a designed process. The designed process included the following steps: 1.selecting a portion with +400mesh size from unburned carbon; 2.treating the selected in ultrasonic waves; 3.using a 400mesh sieve to obtain the product which is under 400mesh; 4.Removal ash from the product. In regard to treatment by ultrasonic waves in the designed process, treating time of ultrasonic waves is a simple and only variance in this study. The results indicate that the production yields increase with the treating time of ultrasonic waves; the production yield in specific conditions of this study can reach about 23%, in which ash content in product is about 2.5%. According to results of SEM, TEM and XRD, the products from the designed process are flakes in shape, several microns in size and graphitized carbon in carbon crystal phase. Except to graphitized carbon, there are a little carbon blacks, which are graphite 2H in carbon crystal phase in the products. Conclusively, the designed process is possibly applicable, by which comes to the recovery of micron- graphitized carbon.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.6
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• pp.334-339
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• 2005

Although phosphogypsum can have profound effects on both the physical and chemical properties of certain soils with supplying the essential elements, no widespread use of by-product phosphogypsum will be made unless such uses pose no threat to the public health and soil contaminations. This study was conducted to evaluate the effects of phosphogypsum on the growth of oriental melon and soil properties in plastic film house. Phosphogypsum was treated at the rate of $70kg\;CaO\;10a^{-1}$ and the effects were compared with the treatment of Ca-Mg carbonate. In the treatment of phosphogypsum, early growth of oriental melon was significantly increased comparing to the growth in the Ca-Mg carbonate treatment. Total fruit yield was not different between the treatments of phosphogypsum and Ca-Mg carbonate, but marketable fruit yield was higher in the phosphogypsum treatment. Although Ca and S contents in oriental melon were increased in the phosphogypsum treatment, contents of toxic heavy metals including As, Cd, Cr, Cu, and Pb were not different between the two treatments. Also, soil pH and contents of extractable toxic metals in the soil were not significantly different between the two treatments after the experiment. These results suggest that phosphogypsum can be a valuable substitute for lime materials in high pH soils of plastic film house.

• Proceedings of the Korea Society of Environmental Biology Conference
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• 2002.11a
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• pp.123-126
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• 2002

Pollutants that are persistent, bioaccurnulative, and toxic have been linked to numerous adverse effects in human and animals, PBTs include heavy metals, polychlorinated biphenyls (PCBs), dioxins, polycyclic aromatic compounds (PACs) in addition to pesticides. This study focuses on toxic effects of the PBTs except pesticides on insects. Eight PBTs were selected from subgroups: three heavy metals (Pb, Hg, and Cd), two PCB mixtures (Aroclor mixtures 1 and 2), 2,3,7,8-tetrachlorodibenzo-p-dioxin, two monophenols (4-octylphenol and 4-nonylphenol), and tetrabutyltin, Beet armyworm, Spodoptera exigua, was used as test target insect species. Three physiological markers (metamorphosis, immune reaction, and follicle patency) were assessed in each exposure to different doses of the PCBs. Heat-shock proteins as molecular markers were also analyzed in response to the PCBs. All tested PBTs were toxic to metamorphosis from larvae to pupae when they were applied with diet. Two PCB mixtures were the most toxic compounds in this assay by giving significant toxicity at 0.005 ppm, while others had from 10 to 1000 ppm. Dioxin (0.1 ppb), tetrabutyltin (0.1 ppb), Pb (10 ppb), and Hg (0,01 ppb) were potent to inhibit immune reactions analyzed by inducing phenoloxidase activity and blocked phospholipase $A_2$ enzyme, Tetrabutyltin and dioxin significantly induced follicle cell patency, but their effects were lower than that of endogenous juvenile hormone, Dioxin, Pb, Hg, and Cd could induce the expression of heat shock proteins that were detected by immunoblotting against human HSP70 monoclonal antibody. HSP78 and HSP80 were upregulated in response to the PBTs. This expression was detected from the fat body and epidermis at as fast as 4h after injection. All these results clearly suggest that PBTs give significant ecotoxicity to insects that are valuable organisms in our environment.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.2
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• pp.66-74
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• 2021

Cladding material, which can selectively obtain excellent properties of different metals, is a composite material that combines two or more types of dissimilar metals into one plate. The titanium-copper cladding material between titanium which has excellent corrosion resistance and copper which has high thermal and electrical conductivity, are highly valuable composite materials. It can be used as heat exchangers with high conductivity under severe corrosion conditions. In order to apply the clad plate to the heat exchanger, it must be manufactured in the form of a tube and additional welding is required. It is important to select the cladding material manufacturing process and the welding process. The process of manufacturing the cladding material includes extrusion, rolling, and explosive bonding. Among them, the explosive bonding process is suitable for additional welding because no heat-affected zone is formed. In this study TIG welding of the explosive-bonded dissimilar clad plates was successfully performed by butt welding. The microstructures and bonding interface of the welded part were observed, and the effect of the bonding layer at the welding interface and the intermetallic compounds on the mechanical properties and tensile plastic deformation behaviors were analyzed. And also the integrity of TIG-welded dissimilar part was evaluated.