• Clean Technology
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• v.19 no.4
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• pp.487-491
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• 2013

To efficiently desorb gold and copper-cyanide complexes adsorbed onto Dowex21K XLT resin, the mixed solvent with HCl and acetone which is a kind of dipolar aprotic solvent was used as a desorbing agent. The desorption efficiency for gold-cyanide complex was the highest as about 94% when the mixing ratio of HCl and acetone based on volume was the 7:3, however, the value decreased as the ratio of acetone increased. In the case of copper-cyanide complex, most of them was desorbed when the amount of HCl was relatively higher than that of acetone, however, desorption efficiency decreased as the ratio of acetone increased. The desorption efficiency for gold and copper-cyanide complexes was the 94 and 100%, respectively at the 0.6 M of HCl with the 7 (HCl) : 3 (Acetone) of mixing ratio and desorption efficiency for gold-cyanide complex not increased any more even though higher HCl concentration was used. And the desorption efficiency for gold and copper-cyanide complexes was about 100% at the S/L raio ${\leq_-}1.0$ whereas desorption efficiency for gold-cyanide complex was very low as about 20-29% at the S/L ratio > 1.0. Also, most of desorption process for gold and copper-cyanide complexes was completed within 120 min.

• Resources Recycling
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• v.21 no.5
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• pp.3-17
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• 2012

Selective leaching processes for copper, gold, nickel, and cobalt have been investigated because there is an advantage of ammoniacal hydrometallurgy that metal such as copper could be selectively extracted restricting the dissolution of iron or calcium. In the present article, the studies for selective ammoniacal leaching of copper from motor scraps and waste printed circuit boards (PCBs), for ammoniacal leaching of gold to decrease the amount of cyanide used or to substitute cyanide by thiosulfate, and for ammoniacal leaching to recover nickel and cobalt from nickel oxide ore and intermidiate obtained from manganese nodule treatment process were summarized and further studies were proposed for domestic technology development for ammoniacal hydrometallurgy processes.

• Resources Recycling
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• v.24 no.1
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• pp.66-72
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• 2015

Various waste PCBs arose during disassembly of LCD TVs and monitors in which they originally functioned for transmission of imaging signal, power supply, and imaging control. In those functional PCBs, gold and copper are contained at far more acceptable level, exceeding mining grade ores. Those valuable metals and their contents widely vary with functionality and end use of PCBs. Therefore, compositional analysis of individual waste PCBs from disassembled LCD TVs and monitors were performed in the present study to classify them into three categories: high gold yield and low gold yield PCBs and those without gold contents. Besides, additional chemical analysis was made to reveal gold and copper contents in the waste PCBs arising from actual disassembly/separation of end-of-life LCD TVs and monitors.

• The Korean Journal of Zoology
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• v.15 no.3
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• pp.105-110
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• 1972

A cellulosse acetate electrophoretic survey of Korean Anura has revealed the presence of diverse lactate and malate dehydrogenase (LDH and MDH) isozymes. The pattern of LDH and MDH isozymes in the tissues of the central nervous system of the six species of Anura examined are species specific and differ from those of mammals and birds. Both Rana nigromaculata nigromaculata and Rana nigromaculata coreana have two molecular forms of LDH and MDH, respectively, with almost the same pattern. Whole brain homogenate of Rana temporaria shows also a maximum of only two LDH isozymes. Both Bufo bufo asiaticus and Bombina orientalis have five molecular forms of LDH with an entirely different spacing on the zymograms, whereas Rana rugosa has three. Two molecular forms of MDH are present in all animals examined and one band is shown in olfactory lobe and mixture of cerebellum and medulla oblongata of Rana nigromaculata nigromaculata.

• Proceedings of the Zoological Society Korea Conference
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• 1997.10b
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• pp.90.2-90
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• 1997

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.3
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• pp.177-185
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• 2014

Purpose: This study is designed to investigate the various impacts of different types of scaler tips such as cooper alloy base tip and the others on the surface roughness of teeth and implant by the method which is currently in clinical use. Materials and methods: Four different types of disc shaped porcelain, titanium, zirconia, and Type III gold alloy dental materials sized 15 mm diameter, 1.5 mm thickness were used for the experiment. Plastic hand curette (Group PS), cooper alloy new tip (Group IS), and stainless steel tip (Group SS) were used as testing appliances. A total of 64 specimens were used for this study; Four specimens for each material and appliance group. Surface roughness was formed with 15 degree angle in ultrasonic scaler tip and with 45 degree angle in hand curette of instrument tip and the specimen surface with 5 mm long, one horizontal-reciprocating motion per second for 30 seconds by 40 g force. To survey the surface roughness of each specimen, a field emission scanning electron microscope, an atomic force microscope, and a surface profiler were used. (Ra, ${\mu}m$). Results: According to SEM, most increased surface roughness was observed in SS group while IS groups had minimal roughness change. Measurement by atomic force microscope presented that the surface roughness of SS group was significantly greater than those of PS, IS and control groups in the type III gold alloy group (P<.05). IS group showed lesser surface roughness changes compared to SS group in porcelain and gold alloy group (P<.05). According to surface profiler, surface roughness of SS group showed greater than those of PS, IS and control groups and IS group showed lesser than those of SS group in all specimen groups. Type III gold alloy group had large changes on surface roughness than those of porcelain, titanium, zirconia (P<.05). Conclusion: The result of this study showed that newly developed copper alloy scaler tip can cause minimal roughness impacts on the surface of implant and dental materials; therefore this may be a useful alternative for prophylaxis of implant and restored teeth.

• Resources Recycling
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• v.25 no.1
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• pp.3-9
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• 2016

The leaching behavior of gold from waste CPU chip using Iodide/Iodine solution was studied. The direct leaching of gold with Iodide/Iodine solution for CPU chip under the size of 150 mesh showed leaching ratio of 20%. It was assumed that the copper film was produced on the gold particle during grinding process and the copper film prevents lodine/Iodide solution from contacting with leachable gold. Meanwhile, the extraction of gold was improved to 90% by pretreatment process with $HNO_3$ solution. In order to explain the result, EDS and ICP analysis for the leaching residue were conducted. It was found that the copper coated on the surface of the gold particle was removed about 80% by $HNO_3$, resulting in the increment of gold leaching rate.

• Korean Journal of Heritage: History & Science
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• v.54 no.1
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• pp.4-17
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• 2021

This study analyzed 19 samples of harness fittings and pendants, which were excavated in Tomb No. 15 in Songhyeon-dong, Changnyeong. Harness fittings and pendants are used for ostentation, rather than practicality, and were excavated from ancient tombs in Gaya culture. So, they are considered artifacts that compare the production techniques and raw materials. This study aimed to examine the production techniques and provenience studies of Bihwa Gaya, which is estimated to be from the 5th to 6th centuries. According to the research, harness fittings were made of pure copper and were gilded with Au·Ag alloys on their surfaces. Hg was detected together and plated with a mercury amalgam method. As a result of the pendant (fish scales-pattern, oval and fish-tail shape), analysis showed that Fe in the background metal, Cu in the middle layer, and Au and Ag on the surface were the main components. The method of adhesion between Cu and Au·Ag gilded layers are plated by a mercury amalgamation method. So, it was identified by the gilt-iron·gold·bronze technique. Since the pendant (heart shaped) is found to be the main component of Fe in the background metal and Ag in the surface layer, the metal was made gilt-iron·silver technique. The background metal and gilding were additionally fixed using a rivet. The raw materials of 3 harnesses excavated from Changnyeong are plotted in zone 2 in the southern Korean Peninsula. And 16 harnesses were plotted in Chinese copper ore by Mabuchi Hishao in the Chinese Peninsula.

• Resources Recycling
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• v.21 no.6
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• pp.45-50
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• 2012

The room-temperature electrodeposition of metallic lithium was investigated from ionic liquid, 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13TFSI) with lithium bis (trifluoromethanesulfonyl)imide (LiTFSI) as a lithium source. Cyclic voltammograms on gold working electrode showed the possibility of the electrodeposition of metallic lithium, and the reduction current on a gold electrode was higher than the value on platinum and copper. The metallic lithium could be electrodeposited on the gold electrode under potentiostatic condition at -2.4 V (vs. Pt-QRE) and was confirmed by analytical techniques including XRD and SEM-EDS. The dendrite-typed electrodeposits were composed of a metallic lithium and a alloy with gold substrate. And any impurity could be detected except for trace oxygen introduced during handling for the analyses.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.23.1-23.1
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• 2010

Alkanethiol (CH3(CH2)nSH) 자기 조립 박막은 금, 은, 팔라듐 그리고 구리와 같은 금속 물질과 결합하여 산화 방지 보호막, 생화학적 멤브레인 그리고 케미컬 센서로 널리 이용되었다. 전도성을 가진 많은 금속 분말 중에서, 구리는 뛰어난 열, 전기 전도성과 풍부한 양으로 다른 귀금속에 비교하여 경제성까지 갖춘 물질이다. 그러나 이러한 구리 나노 분말은 대기에 노출된 구리 분말이 쉽게 산화된다는 결정적인 단점 때문에 그동안 널리 이용되지 못하였다. 이러한 구리의 단점을 극복하고 뛰어난 전도성의 특징을 이용하고자, Langmuir-Blodgett (LB), layer by layer (LbL), electrophoretic deposition (EPD), self-assembled monolayer (SAM)과 같은 구리 나노 분말 위에 유기 박막을 형성하고자 하는 많은 방법이 시도되어왔다. 이러한 방법들 대부분은 습식 방법으로 진행되었으며, 약 2-nm 두께의 SAM 구조를 형성할 수 있음이 많은 연구를 통하여 확인되었다. 그러나 습식 기반의 SAM 구조는 단지 수일 동안만 유효하며, 이는 코팅을 수행하면서 점차 떨어지는 source solvent의 순도와 적합하지 않은 코팅 조건, 그리고 이러한 원인으로 형성된 부실한 막질 구조 때문으로 추측된다. 게다가 이러한 습식 기반 공정은 코팅 막의 두께 조절과 코팅 시 solvent의 순도를 일정하게 유지하는 것이 매우 복잡하고 어려운 작업으로 알려져 왔다. 본 실험에서는 고 진공 챔버 (< $4.0{\times}10-6$ torr) 시스템을 이용하여 습식 기반 공정의 문제점을 극복하고 구리 나노 분말의 산화를 막기 위한 실험을 진행하였다. 1-octanethiol (CH3(CH2)7SH)은 중간 길이의 hydrocarbon (n=7) 구조를 가진 특징 때문에 코팅 물질로 사용되었다. 게다가, alkanethiol 족 특유의 물질인 황(sulfur)은 구리와 결합하여 산화방지 보호막의 역할을 수행할 수 있다. 저 진공 조건에서는 10-nm의 multilayer가 일괄적으로 코팅됨을 확인할 수 있었다. 본 실험에서는 약 10-nm 두께의 자기 조립 박막(self assembled monolayers: SAMs)이 고 진공 조건에서 구리 나노 분말 표면 위에 코팅 조건의 변경을 통해서 5-nm에서 10-nm 두께의 1-octanethiol SAMs 구조를 얻어낼 수 있었다. 이는 고 진공 조건에서 1-octanethiol SAMs의 코팅 두께를 조절함으로 다양한 크기의 분말에 코팅 물질로 쓰일 수 있음을 알 수 있다.