• Journal of the Korean Chemical Society
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• v.23 no.3
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• pp.161-164
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• 1979

The effect of acidity and the metal surface area of the Pd loaded zeolite catalysts; prepared from $Ca^{2+}-,\;La^{3+}-,\;NH_4^+-$exchanged Y and dealuminated HY was studied for the reaction of n-butane. The amount of strong acid site determined by the temperature programmed desorption of ammonia increased in the order NaY < CaY < LaY. Total amount of acid site decreased with increasing degree of dealumination, but the portion of strong acid site increased with increasing $SiO_2/Al_2O_3$ ratio. The effective metal surface area determined by the CO adsorption technique was large for those zeolite catalysts having strong acidity. It was found that conversion of n-butane was strongly dependent on the acidity and the effective metal surface area of the catalysts. The fact that the conversion of n-butane was proportional to the effective metal surface area suggests that the dehydrogenation by metallic component is the primary step in the reaction of n-butane.

• Resources Recycling
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• v.1 no.1
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• pp.23-28
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• 1992

The process for recovery of acids and valuable metals such as nickel and chromium from the stainless-steel pickling acids has been developed vased on the use of solvent extraction technique. Until now, several processes for the treatment of waste acids were already developed in such countries as Japan, Swden and Canada. Those methods are, however, forcussed on the recovery of acids from them discarding the metals included in them as the hydroxides sludge. In the present work, the recovery of nickel and chromium in addition to nitric acid and hydrofluoric acid has been aimed so as to recycle them to the stainless-steel pickling lines and also to minimize the amount of sludge generated during the treatment of waste acids. The establishment of the process to recover the acids has been carried out based on the solvent extraction with TBP. The iron was eliminated from the waste solutions by precipitating in the form of hydroxide through the adjustment of pH with calcined limestone and the selective extration of chromium and nickel from the resultant solutions has been conducted by using D2EHPA as extractant.

• Applied Chemistry for Engineering
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• v.31 no.4
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• pp.438-442
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• 2020

Studies on the recovery conditions and optimization process for valuable metal recovery through chemical treatment from detoxified asbestos-containing waste composed of calcium silicate, larnite, merwinite, and akermanite were conducted. The main components, Si, Ca, and Mg, of detoxified asbestos-containing waste (DACW) were separated and recovered in the form of SiO₂, CaSO₄, and Mg(OH)₂ compounds, respectively. Each separated component was confirmed through X-ray diffraction (XRD) and inductively coupled plasma spectrometer (ICP) analysis. The recovery conditions for each component were first treating them with an acid to separate SiO₂ and subsequently with H₂SO₄ to recover Ca in the form of sulfate, CaSO₄. The remaining Mg was recovered by precipitation with Mg(OH)₂ under strong basic conditions. This study suggested that it is possible to convert existing treatment process of asbestos waste by landfill through recovering the components into a resource-recycling green technology.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1642-1647
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• 2009

Changes in aerosol characteristics during 2006 ${\sim}$2008 Asian dust events in Cheoan were investigated by measuring mass, ion and elemental concentrations of fine and coarse particles. The average mass concentrations of daily TSP, PM10, PM2.5 were 214.9, 160.3, and 95.9${\mu}\;g/m^3$during Asian dust events, which were 3.08, 2.58, and 1.95 times higher than Non-asian dust events. The maximum concentrations of TSP, PM10, and PM2.5 were 850.1, 534.4, and 233.3${\mu}\;g/m^3$, which were 12.19, 8.60, and 4.76 times higher, respectively. Increases in ion concentrations were not significant during Asian dust events, but elemental concentrations including soil components such as Fe, Al, Ti increased by 17.1 and 43.4 times for fine and coarse particles, respectively. The results clearly indicate that metallic components from soil constituents were the major components in Asian dusts sampled at Cheonan.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.111.2-111.2
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• 2011

야금학적 방법을 통한 태양전지용 실리콘 제조를 위하여 아크로(Arc furnace)에서 제조된 용융 상태의 금속급 실리콘을 슬래그와 직접 반응시켜 불순물을 제거하는 공정에 관한 연구를 수행하였다. 이를 위해 아크로와 고주파 유도용해로(High-frequency induction furnace)를 이용하여 금속급 실리콘을 제조와 정련 특성 실험을 수행하였다. 본 연구에서 금속급 실리콘을 제조하기 위한 장비로 150kW급-DC 아크로와 300kW급-AC 아크로를 사용하였다. 원재료로 규석, 코크스(Cokes), 숯, 그리고 우드칩(Wood chip)을 실험 비율에 맞춰 아크로 내부에 장입하고, 이를 용융환원 방법을 통해 반응을 시켰다. 이때 생산된 금속급 실리콘의 순도는 약 99.2~99.8% 이었으며, 원재료의 순도, 장입 비율 및 아크로 운전 특성에 따라 편차가 있다. 아크로에서 생산된 금속급 실리콘의 경우 인(phosphorus), 붕소(boron)를 다량 함유하고 있고, 이를 제거하기 위하여 50kW급 고주파 유도용해로 장비를 사용하여 슬래그 정련 실험을 수행하였다. 슬래그 정련시 사용한 성분은 SiO2, CaO 그리고 CaF2 이며, 금속급 실리콘과 슬래그의 질량비 및 반응 시간에 따른 실리콘 불순물 특성을 평가하였다. 실험결과 인과 붕소는 각각 1 ppm 이하, 5 ppm 이하 였으며, 칼슘을 제외한 대부분의 금속 불순물의 경우 0.1~0.2% 임을 확인하였다.

• Resources Recycling
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• v.19 no.5
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• pp.25-30
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• 2010

Leaching of CMSX-4 superalloy was done in hydrochloric acid solutions. The leaching behaviors of main alloy components, such as Ni, Co, Cr, Al, was investigated by controlling acid concentration, temperature, leaching time and pulp density. Increasing acid concentration enhanced the leaching rate till the rate decreased over 3 M acid concentration. Raising temperature increased the leaching amount of the metal components. After the leaching for 60 minutes at $90^{\circ}C$ and 10 g/L pulp density in 4 M acid solution, 93.2% nickel, 89.9% aluminum, 80.4% cobalt, and 79.1% chromium were leached. Nickel and aluminum were preferentially leached out, while the leaching rate of cobalt and chromium were relatively high only after 60 minutes, Increasing pulp density lowered the leaching rate and especially serious on cobalt and chromium, The optimum leaching condition for CMSX-4 was obtained at $90^{\circ}C$, 120 minutes, and less than 125 g/L in 4 M hydrochloric acid solution.

• Resources Recycling
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• v.14 no.5 s.67
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• pp.45-53
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• 2005

Electro-generated chlorine leaching of waste printed circuit boards was investigated in hydrochloric acid solutions. Non-magnetic component of $0.6{\sim}1.2mm$ was prepared by grinding, magnetic separation, and sieving. The non-magnetic component of pulverized printed circuit board contained about 45% of metal component, in which copper was about 83.6%. The leaching rate of copper was greatly affected by current density and agitation speed. The leaching of copper up to 98% was achieved at $20mA/cm^2$, $50^{\circ}C$, 180 minutes, and 600 rpm in 1M HCl solutions. Increasing agitation and lowering current density enhanced utilization efficiency of electro-generated chlorine. Leaching of copper was suppressed at the initial stage, while the minor metal elements, such as aluminum, lead, and tin, were dominantly leached out.

• Journal of the Korean Chemical Society
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• v.29 no.4
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• pp.341-347
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• 1985

Formation of metal complex is the first step in the many biological actions of metal ions present in the biological systems. In this work the not electron affinity necessary for the formation of such metal complexes has been determined for a series of metal ions. It has been found that excess polarizing strength can be adopted as a measure of electron affinity and trend is the excess polarizing strength is related to Irving-Williams series. Those metal ions having greater than 0.22 in value of excess polarizing strength have been found to show carcinogenicity and other metal ions, which are supposed to be carcinogenic, have shows to have greater than 0. 22 in value of excess polarizing strength, demonstrating that excess polarizing strength could be used to determine if any metal ion possesses carcinogenic activity.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.116-116
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• 2018

부식은 재료와 사용 환경과의 상호작용에 의한 결과로서 일반적으로 두께의 감소와 균열의 발생 및 파손 등의 문제로 나타난다. 특히 사용환경 중에서 해수 분위기는 금속의 부식에 가장 유리한 조건이다. 따라서 해양환경 중 항만이나 조선 및 해양 산업 등에 많이 이용되는 강 구조물은 이에 대응하기 위하여 도장방식이나 음극방식을 사용하고 있다. 여기서 음극방식은 피방식체를 일정전위로 음극 분극하는 원리로써 외부전원을 인가하거나 비전위의 금속을 전기적으로 연결하여 방식하는 방법이다[1]. 한편, 해수 중에서 이와 같은 원리로 음극방식 할 경우에는 피방식체인 강재표면에 부분적으로 칼슘 또는 마그네슘 화합물 등의 생성물이 부착하는 현상을 볼 수 있게 된다. 이와 같이 수산화마그네슘($Mg(OH)_2$)및 탄산칼슘($CaCO_3$)을 주성분으로 하여 석출되는 석회질 피막(calcareous deposits)은 피방식체에 유입되는 음극방식 전류밀도를 감소시켜 주거나 물리적 장벽의 역할을 함으로써 외부의 산소와 물 등 부식환경으로부터 소지금속을 보호한다[2]. 그러나 석회질 피막은 소지금속과의 결합력, 막의 균일한 분포, 내식성 및 제작시간의 단축 등 해결해야 할 과제가 있다. 또한 여러 가지 환경 조건 등의 영향을 받아 그 피막의 형성 정도도 가늠하기 어렵기 때문에 음극방식 설계 시 그 정도에 따른 영향을 고려-반영하기가 곤란하다. 따라서 본 연구에서는 석출속도, 밀착성 및 내식특성을 향상시키기 위해 전착프로세스를 통해 해수 중 기체를 용해시켜 석회질 피막을 제작하고 막의 결정구조 제어 및 특성을 분석-평가하였다. 본 연구에 사용된 강 기판(Steel Substrate)은 일반구조용강(KS D 3503, SS400)을 사용하였으며, 외부전원은 정류기(Rectifier, xantrex, XDL 35-5T)를 사용하여 3 및 $5A/m^2$의 조건으로 인가하였다. 양극의 경우에는 해수에 녹아있는 이온 이외에 다른 성분들이 환원되는 것을 방지하기 위해 불용성 양극인 탄소봉(Carbon Rod)을 사용하였다. 이때 석출속도, 밀착성 및 내식특성 향상을 위해 해수에 주입한 기체의 양은 0.5 NL/min였으며, 기판 근처에 고정하여 음극 부근에서의 반응을 유도하였다. 각 조건별로 제작된 막의 표면 모폴로지, 조성원소 및 결정구조 분석을 실시하였으며, 석회질 피막의 밀착성과 내식특성을 평가하기 위해 규격에 따른 테이핑 테스트(Taping Test, ISO 2409)와 3 % NaCl 용액에서 전기화학적 양극 분극 시험을 진행하여 제작된 막의 내구성과 내식성을 분석-평가하였다. 시간에 따른 전착막의 외관관찰 결과 전류밀도의 증가와 함께 상대적으로 많은 피막이 형성되었고, 용해시킨 기체에 의해 더 치밀하고 두터운 피막이 형성됨을 확인할 수 있었다. 성분 및 결정구조 분석 결과 $Mg(OH)_2$ 성분의 Brucite 및 $CaCO_3$ 성분의 Calcite 및 Aragonite 구조를 확인하였으며, 용해시킨 기체의 영향으로 $CaCO_3$ 성분의 Aragonite 구조가 상대적으로 많이 검출되었다. 밀착성 및 내식성 평가를 실시한 결과 해수 중 용해시킨 기체에 의해 제작한 시편의 경우 견고하고 화학적 친화력이 높은 Aragonite 결정이 표면을 치밀하게 덮어 전해질로부터 산소와 물의 침입을 차단하는 역할을 하여 기체를 용해시키지 않은 3 및 $5A/m^2$ 보다 비교적 우수한 밀착성 및 내식 특성을 보이는 것으로 사료된다.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.1
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• pp.53-60
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• 2012

Purpose: The purpose of this study was to compare Ni-Cr alloy property of gas-oxygen torch soldering and infrared welding using optical microscope and Electron Probe Micro Analyzer (EPMA). Materials and methods: Ni-Cr alloys were casted for specimens. Specimens had 3.0 mm diameter, 30.0 mm length and were divided into two groups. Each group had 4 specimens. One group was for gas-oxygen torch soldering and the other was infrared welding. Specimens were cut with low-speed disc and soldered each other with gas-oxygen torch and infrared machine. After soldering and polishing, specimens were observed at 3 points (soldering point, 5 mm distance point, 10 mm distance point) with optical microscope and analyzed 3 points (soldering point, 5 mm distance point, 10 mm distance point with EPMA. Results: The results of this study were as follows: 1. The observation of gas-oxygen torch soldering at 10 mm distance point under the optical microscope was not founded any specific surface properties, but some crack lines were observed at 5 mm distance and soldering point. 2. There were no crack lines were founded at the observation of infrared welding at 10 mm distance and 5 mm distance points under the optical microscope. However, at the 5 mm distance, the surface was not smooth enough compared with at 10 mm distance point. Some crack lines were observed at the welding point as well. 3. In the EPMA analysis of the gas-oxygen torch soldering, the component of Ni was increased by 4.5%, Cr was increased by 7.5% than that of the Ni-Cr alloy at the 10.0 mm distance. At the 5 mm distance, the component of Ni was decreased by 6.1%, Mo was increased by 9.0% than that of the Ni-Cr alloy but Cr was equally shown at the 5.0 mm distance. Only Ni was shown at the soldering point. 4. In the EPMA analysis of the infrared welding, the component of Ni was increased by 9.1%, Cr was increased by 0.4% than that of the Ni-Cr alloy but Al was equal at the 10.0 mm distance. At the 5 mm distance, the component of Ni was increased by 4.7%, Cr was increased by 4.7% and Al was increased by 0.1% than that of the Ni-Cr alloy. At the welding point, the component of Ni was increased by 8.8%, Cr was increased by 8.2% than that of the Ni-Cr alloy. Conclusion: From these results, at the 5 mm distance from the soldering point, the surface of the infrared welding was more smoother than that of the gas-oxygen torch soldering. On the EPMA analysis, the component of the specimens with infrared welding was more similar than that of the gas-oxygen torch soldering compared with the component of the Ni-Cr alloy.