• Economic and Environmental Geology
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• v.36 no.3
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• pp.177-189
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• 2003

The main purposes of this study are to utilize mineralogical studies such as optical microscope, XRD and SEM/EDS analyses to characterize the oxidation of sulfide minerals and the mechanisms controlling the movement of dissolved metals from waste rocks at the abandoned Seobo mine. Mineralogical research of the waste rocks confirms the presence of anglesite, covellite, goethite, native sulfur and nsutite as secondary minerals, suggesting that these phases control the dissolved concentrations of As, Cu, Fe, Mn, Pb and Zn. The dissolved metals are precipitated, adsorbed and/or coprecipitated with(or within) Fe(Mn)-hydroxides and Mn(Fe)-hydroxides. The main phases of secondary mineral, Fe-hydroxide, can be classified as amorphous or poorly crystalline and more crystallized phases(e.g. goethite) by crystallinity. Amorphous or poorly crystalline Fe-hydroxide has relatively high As contents(9-24 wt.%). This poorly crystalline Fe-hydroxide changes toward more crystallized phase(e.g. goethite) which contains relatively low As(0.6-7.7 wt.%). These results are mainly due to the progressive release of As with the crystallization evolution of the As-trapping poorly crystalline Fe-hydroxides. It is also attributed to the differences of specific surface areas between the poorly crystalline Fe-hydroxides and well crystallized phases. The dissolved metals from waste rocks at Seobo mine area are naturally attenuated by a series of precipitation(as Fe, Mn, Cu, Pb), coprecipitation(Fe, Mn) and adsorption(As, Cu, Pb, An) reactions. The results of mineralogical researches permit to assess the environmental impacts of mine waste rocks in the areas, and can be used as a useful data to lay available mine restoration plan.

• Ecology and Resilient Infrastructure
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• v.3 no.4
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• pp.279-284
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• 2016

Mine tailings generated during mining activity often contain high concentrations of heavy metals, with pyrite-containing mine tailings in particular being a major cause of environmental problems in mining areas. Chemical cell technology, or fuel cell technology, can be applied to leach heavy metals in pyrite-containing mine tailings. As pyrite dissolves through spontaneous oxidation (i.e. galvanic oxidation) in the anode compartment of the cell, $Fe^{3+}$, sulfuric acid are generated. A decrease in pH due to the generation of sulfuric acid allows heavy metals to be leached from pyrite-containing mine tailings. In this study, pyrite was dissolved for 4 weeks at $23^{\circ}C$ in an acidic solution (pH 2) and in a galvanic reactor, which induces galvanic oxidation, and total Fe leached from pyrite and pH were compared in order to investigate if galvanic oxidation can facilitate pyrite oxidation. The change in the pyrite surface was analyzed using a scanning electron microscope (SEM). Comparing the total Fe leached from the pyrite, there were 2.9 times more dissolution of pyrite in the galvanic reactor than in the acidic solution, and thus pH was lower in the galvanic reactor than in the acidic solution. Through SEM analysis of the pyrite that reacted in the galvanic reactor, linear-shaped cracks were observed on the surface of the pyrite. The study results show that pyrite dissolution was facilitated through the galvanic oxidation in the galvanic reactor, and also implied that the galvanic oxidation can be one remediation option for pyrite-containing mine tailings.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.194.1-194.1
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• 2014

기저면에 구조적 결함을 도입함으로써 그래핀과 $MoS_2$와 같은 이차원 결정의 물리, 화학, 전기 및 기계적 성질을 제어하려는 연구가 폭넓게 수행되고 있다. 본 연구에서는 플라즈마 속의 산소 래디컬을 이용하여 기계적 박리법으로 만들어진 단일층 그래핀과 $MoS_2$ 표면에 구조적 결함을 유도하고 제어하는 방법을 개발하였다. 라만 및 광발광 분광법을 통해 생성된 결함 밀도를 측정하고 전하 밀도 등의 화학적 변화를 추적하였다. 그래핀의 경우 산소 플라즈마 처리 시간에 따라 결함(defect)의 정도를 보여주는 라만 D-봉우리의 높이와 넓이가 커짐을 확인하였고 이를 G-봉우리의 높이와 비교하여 정량하였다. $MoS_2$의 경우 $E{^1}_{2g}$와 $A_{1g}$-봉우리의 높이가 점점 감소하고 광발광의 세기 또한 감소함을 확인하였다. 또한 본 연구에서는 기판의 편평도가 결함 생성 속도에 미치는 영향을 비교 및 분석하여 반응 메커니즘을 제시하고자 한다.

• Economic and Environmental Geology
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• v.43 no.2
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• pp.137-148
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• 2010

The Myoungbong mine located in Boseong-gun, Jellanamdo consists of Au-Ag bearing quartz veins which filled the fissures of Bulguksa granitic rocks of Cretaceous. The tailings obtained from the Myungbong mine were used to investigate the effects of various processes, such as oxidation of primary sulfides and formation(alteration) of secondary and/or tertiary minerals, on arsenic immobilization in tailings. This study was conducted via both mineralogical and chemical methods. Mineralogical methods used included gravity and magnetic separation, ultrasonic cleaning, and instrumental analyses(X-ray diffractometry, energy-dispersive spectroscopy, and electron probe microanalyzer) and aqua regia extraction technique for soils was applied to determine the elemental concentrations in the tailings. Iron (oxy)hydroxides formed as a result of oxidation of tailings were identified as three specific forms. The first form filled in rims and fissures of primary pyrites. The second one precipitated and coated the surfaces of gangue minerals and the final form was altered into yukonites. Initially, large amounts of acid-generating minerals, such as pyrite and arsenopyrite, might make the rapid progress of oxidation reactions, and lots of secondary minerals including iron (oxy)hydroxides and scorodite were formed. The rate of pH decrease in tailings diminished, in addition, as the exposure time of tailings to oxidation environments was prolonged and the acid-generating minerals were depleted. Rather, it is speculated that the pH of tailings increased, as the contribution of pH neutralization reactions by calcite contained in surrounding parental rocks became larger. The stability of secondary minerals, such as scorodite, were deteriorated due to the increase in pH, and finally arsenic might be leached out. Subsequently, calcimn and arsenic ions dissociated from calcites and scorodites were locally concentrated, and yukonite could be grown tertiarily. It is confirmed that this tertiary yukonite which is one of arsenate minerals and contains arsenic in high level plays a crucial role in immobilizing arsenic in tailings. In addition to immobilization of arsenic in yukonites, the results indicate that a huge amount of iron (oxy)hydroxides formed by weathering of pyrite which is one of typical primary minerals in tailings can strongly control arsenic behavior as well. Consequently, this study elucidates that through a sequence of various processes, arsenic which was leached out as a result of weathering of primary minerals, such as arsenopyrite, and/or redissolved from secondary minerals, such as scorodite, might be immobilized by various sorption reactions including adsorption, coprecipiation, and absorption.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.06a
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• pp.3-7
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• 1998

본 연구에서는 광산 인근 토양에서 산성비를 비롯한 침출수에 의한 지하 환경 오염 메카니즘을 검토하고, 오염 방지 및 교정과 대안의 효과를 정량화 하기 위한 방안을 고찰하였다. 이를 위하여 중금속인 비소의 오염도가 높은 토양을 대상으로 인위적 산성용액에 의한 비소의 용출을 실험적으로 검토하였다. 한편, 산성 침출오염수에 의한 지하 환경의 오염을 방지하기 위하여 석회석을 활용한 토양의 안정화방법의 효과를 살펴보았다. 오염된 시료토양에 포함된 비소는 pH 1 이하의 강산성 용액일수록 격렬히 용출되었으며, pH 값이 낮아질 수록 최대 용출량은 증가되는 것으로 나타났다. 석회석에 의한 토양 안정화방안은 매우 효과적이었으며, 석회석에 의한 산성용액의 중화반응 특성식은 미반응 핵 모델중에서 화학반응이 속도지배인 특성식에 잘 부합되는 것으로 보여진다.

• Journal of Environmental Science International
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• v.13 no.1
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• pp.37-40
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• 2004

In this study, the decomposition of gas-phase TCE, Benzene and Toluene, in air streams by direct UV Photolysis and UV/TiO$_2$ process was studied. For direct UV Photolysis, by regressing with computer calculation to the experimental results the value of reaction rate constant k of TCE, Toluene and Benzene in this work were determined to be 0.00392s$\^$-l/, 0.00230s$\^$-1/ and 0.00126s$\^$-1/, respectively. And the adsorption constant K of TCE, Toluene and Benzene in this work were determined to be 0.0519 mol$\^$-l/ ,0.0313mo1$\^$-1/ and 0.0084mo1$\^$-1/, respectively. For UV/TiO$_2$ system by regressing with computer calculation to the experimental results the value of reaction rate constant k of TCE, Toluene, and Benzene in this work were determined to be 5.74g/$\ell$$.$min, 3.85g/$\ell$$.$min, and 1.18g/$\ell$$.$min, respectively. And the catalyst adsorption constant K of TCE, Toluene, and Benzene in this work were determined to be 0.0005㎥/mg, 0.0043㎥/mg and 0.0048㎥/mg, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.5
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• pp.104-109
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• 2007

Photochemical patterning of self-assembled mono layers (SAMs) has been performed by diode pumped solid state (DPSS) 3rd harmonic Nd:$YVO_4$ laser with wavelength of 355 nm. SAMs patternings of parallel lines have subsequently been used either to generate compositional chemical patterns or fabricate microstructures by a wet etching. This paper describes a selective etching process with patterned SAMs of alkanetiolate molecules on the surface of gold. SAMs formed by the adsorption of alkanethiols onto gold substrate employs as very thin photoresists. In this paper, the influence of the interaction between the functional group of SAMs and the etching solution is studied with optimal laser irradiation conditions. The results show that hydrophobic functional groups of SAMs are more effective for selective chemical etching than the hydrophilic ones.

• Economic and Environmental Geology
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• v.38 no.5 s.174
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• pp.499-512
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• 2005

EPMA determined that Fe(Mn)-(oxy)hydroxides and well-crystallized Fe-(oxy)hydroxides and could contain a small amount of As $(0.3-11.0\;wt.\%\;and\;2.1-7.4\;wt.\%\;respectively)$. Amorphous crystalline Fe-(oxy) hydroxide assemblages were identified as the richest in As with $28-36\;wt.\%$. On the ternary $As_2O_5-SO_3-Fe_2O_3$ diagram, these materials were interpreted here as 'scorodite-like'. Dissolved As was attenuated by the adsorption on Fe-(oxy) hydroxides and Fe(Mn)-(oxy) hydroxides and/or the formation of an amorphous Fe-As phase (maybe scorodite: $FeAsO_4\cdot2H_2O$). Leaching tests were performed in order to find out leaching characteristics of As and Fe under acidic conditions. At the initial pHs 3 and 5, As contents dissolved from tailings of the cheongyang mine significantly increased after 7 days due to the oxidation of As-bearing secondary minerals (up to ca. $2.4\%$ of total), while As of Seobo mine-tailing samples was rarely released (ca. $0.0-0.1\%$ of total). Dissolution experiments at an initial pH 1 liberated a higher amount of As (ca. $1.1-4.2\%$ of total for Seobo tailings, $1.5-14.4\%$ of total for Cheongyang tailings). In addition, good correlation between As and Fe in leached solutions with tailings was observed. The kinetic problems could be the important factor which leads to increasing concentrations of As in the runoff water. Release of As from Cheongyang tailings can potentially pose adverse impact to surface and groundwater qualities in the surrounding environment, while precipitation of secondary minerals and the adsorption of As are efficient mechanisms for decreasing the mobilities of As in the surface environment of Seobo mine area.

• Economic and Environmental Geology
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• v.34 no.5
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• pp.423-435
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• 2001

The gold-silver vein deposits in the Mugeug mineralized area are emplaced in late Cretaceous biotite granite associated with the pull-apart type Cretaceous Eumseong basin. Mugeug mine in northern part is composed of multiple veins showing relatively high gold fineness and is characterized by sericitization, chloritization and epidotization. The ore-forming fluids were evolved by dilution and cooling mechanisms at relatively high temperature and salinity (=30$0^{\circ}C$,1~9 equiv. wt. % NaCl) and highly-evolved meteoric water ($\delta$$^{18}$ O;-1.2~3.7$\textperthousand$) and gold mineralization associated with sulfides tormed at temperatures between 260 and 22$0^{\circ}C$ and within sulfur fugacity range of 10$^{-11.5}$ ~ 10$^{-13.5}$ atm. In contrast, Geumwang, Geumbong and Taegueg mines show the low fineness values, in southern part are characterized by increasing tendency of simple and/or stockwork veins and by kaolinitization, silicificatitan, carbonatization and smectitization. These droposits formed at relatively low temperature and salinity (<23$0^{\circ}C$, <3 equiv. wt. % NaCl) from ore-forming fluids containing greater amounts of less-evolved meteoric waters ($\delta$$^{18}$ O;-5.5~4.0$\textperthousand$), and silver mineralization representing various gold-and/or silver-bearing minerals formed at temperatures between 200 and 15$0^{\circ}C$ and from sulfur fugacity range of 10$^{-15}$ ~10$^{-18}$ atm These results imply that mineralization in the Mugueg area formed at shallow-crustal level and categorize these deposits as low-sulfidation epithermal type. The genetic differences between the northern and southern parts reflect the evolution of the hydrothermal system due to a different physicochemical environment from heat source area (Mugeug mine) to marginal area (Taegeum mine) in a geothermal field.

• Applied Chemistry for Engineering
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• v.32 no.2
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• pp.163-167
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• 2021

In the present work, we studied a method for the synthesis of uniform gold-peptide hierarchical superstructures using tyrosine rich peptide, Tyr-Tyr-Leu-Tyr-Tyr (YYLYY). Peptide nanoparticles self-assembled by dityrosine bonds were synthesized through the photo-crosslinking reaction of the peptide, and gold-peptide hybrid nanoparticles were synthesized using biomineralization properties of tyrosine in a green synthetic manner. The synthesized gold-peptide hybrid nanoparticles were then characterized by transmission electron microscopy, scanning electron microscopy, dynamic light scattering, UV-vis spectroscopy, scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, and X-ray diffraction. Furthermore, the catalytic activity of gold-peptide hybrid nanoparticles was confirmed by the reduction reaction of methylene blue where the catalytic reaction rate constant was 13.4 × 10-3 s-1.