• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.318-321
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• 2003

비소로 오염된 토양, 하천 퇴적물 및 광미의 복원할 때, 토양 세척 공정에서 중요한 인자인 비소의 화학적 결합형태와 세척제에 따른 용출특성과 고효율 세척 및 세척액의 재활용도를 높이기 위한 공정을 바탕으로 토양세척장비를 설계하였다. 화학적 결합형태에 있어서 토양은 잔류 결합형태가 주되고, 퇴적물의 경우는 철산화물과의 결합형태가 강하며, 광미는 황화물과의 결합에 따른 잔류형태와 철산화물과의 결합형태가 상당부분을 차지한다. 세척제에 따른 용출특성으로부터, 철산화물과 황화물과 결합하고 있는 비소의 화학적 결합형태를 파괴하면서 비소를 추출할 수 있는 용제로 HCl, Oxalate, EDTA, M$_2$O$_2$를 사용하였다. 추출 결과, 비소가 철산화물과 결합한 형태가 비중이 높을수록 EDTA 나 Oxalate가 효율이 높으며, 황화물에 대해서는 HCl과 $H_2O$$_2$이 상대적으로 높은 추출 효율을 보였다. 구성된 세척조는 밀폐실린더형과 스크류이송형 세척조로 구성되어 각각 혼합교반에 의한 세척과 토양입자 분급에 따른 세척이 가능하다. 세척 공정중 최적 산도 조절이 중요한 인자가 되며, 세척액의 재활용도를 높일때, 세척수에 용해되어 있는 비소 및 중금속과 미립자의 동시 제거를 위한 응집 침전조에서 응집제에 의해서 미립자와 함께 제거하는 응집, 침전 및 분리공정을 배치하였다.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.445-455
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• 2009

Microbiological sulfate reduction is the transformation of sulfate to sulfide catalyzed by the activity of sulfate-reducing bacteria using sulfate as an electron acceptor. Low solubility of metal sulfides leads to precipitation of the sulfides in solution. The effects of microbiological sulfate reduction on in-situ precipitation of arsenic and copper were investigated for the heavy metal-contaminated soil around the Songcheon Au-Ag mine site. Total concentrations of As, Cu, and Pb were 1,311 mg/kg, 146 mg/kg, and 294 mg/kg, respectively, after aqua regia digestion. In batch-type experiments, indigenous sulfate-reducing bacteria rapidly decreased sulfate concentration and redox potential and led to substantial removal of dissolved As and Cu from solution. Optimal concentrations of carbon source and sulfate for effective microbial sulfate reduction were 0.2~0.5% (w/v) and 100~200 mg/L, respectively. More than 98% of injected As and Cu were removed in the effluents from both microbial and chemical columns designed for metal sulfides to be precipitated. However, after the injection of oxygen-rich solution, the microbial column showed the enhanced long-term stability of in-situ precipitated metals when compared with the chemical column which showed immediate increase in dissolved As and Cu due to oxidative dissolution of the sulfides. Black precipitates formed in the microbial column during the experiments and were identified as iron sulfide and copper sulfide. Arsenic was observed to be adsorbed on surface of iron sulfide precipitate.

• Economic and Environmental Geology
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• v.36 no.1
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• pp.27-38
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• 2003

Arsenic contamination around Au-Ag mining areas occurs mainly from the oxidation of arsenopyrite which is frequently contained in mine tailings. In weathered tailings, oxidation of sulfide minerals typically results in the formation of abundant ferric (oxy)hydroxides or (oxy)hydroxysulfates near the tailings surface, and arsenic may be associated with these secondary precipitates. In this study, solid phases of arsenic in weathered tailings of some Au-Ag mines were investigated through the SEM/EDS and sequential extraction analyses. The stability of As solid phases and the leaching potential were assessed with the variation of pH and Eh conditions. Oxidation of sulfides in the tailings samples was indicated by depletion of S molar concentrations compared to As and heavy metals. Under XRD examinations, jarosite as an Fe-oxyhydroxysulfate was found in the tailings of Deokeum, Dongil and Dadeok, and scorodite as an As-bearing crystalline mineral was identified from Dadeok which has the highest concentration of As (4.36 wt.%). Beudantite-like phases and some Pb-arsenates were also found under SEM/EDS analysis, and most of As phases were associated with Fe-(oxy)hydroxides and (oxy)hydroxysulfates despite a few arsenopyrite from Samgwang and Gubong. Sequential extraction analysis also showed that As was present predominantly as coprecipitated with Fe hydroxides from Dongil, Dadeok and Myungbong (72∼99%), and as sulfides (58%) and Fe hydroxide-associated forms (40%) from Samgwang and Gubong. In the tailings leaching experiment, As was released with high amounts by the dissolution of As-bearing Fe(oxy)hydroxysulfates in the lowest pH (2.7) conditions of Deokeum, and by desorption under alkaline conditions of Samgwang and Gubong. Higher leaching rates of arsenite(+3) were found under acidic conditions, which pose a higher risk to water quality. Changes in pH and Eh conditions coupled with microbial processes could influence the stabilities of the As solid phases, and thus, time amendments or landfilling of weathered tailings may result in enhanced As mobilization.

• Resources Recycling
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• v.30 no.4
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• pp.11-19
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• 2021

Arsenic (As) oxidation followed by precipitation from a high-As(III)-containing leaching solution derived from a sulfidic ore was investigated in this study to remove aqueous As from the solution using activated carbon (AC) with air injection as an oxidant. To obtain the initial leaching solution, a domestic sulfidic ore was leached in a sulfuric acid solution at pH 1 and 50℃ for 95 h, and approximately 7 g/L of Fe and 3 g/L of As were leached out. To determine the effect of the oxidative reaction utilizing AC with air injection, the leaching solution was tested under the following five oxidative conditions at an initial pH of 1 and 90℃ for 72 h: air-only injection; air injection with 1, 5, and 10 w/v% of AC addition; and H₂O₂ addition. The tests in the presence of both air and AC revealed that the oxidation kinetics and As removal were improved by the reaction between the metallic species and the surface group formed on the AC surface. In addition, the greater the amount of AC added, the better was the reaction efficiency, removing 93-94% of As with more than 5 w/v% of AC addition. Finally, X-ray diffraction analysis confirmed that the precipitate formed from the oxidative reaction was scorodite (FeAsO₄·2H₂O).

• 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.

• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.64-72
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• 2007

Nationwide occurrence of arsenic in groundwater of Korea was investigated with the data from the groundwater quality monitoring stations. During 2001-2006, As has been quantitatively detected in 3.0 % of the total wells $(5.0{\sim}188{\mu}g/L)$, and its geographical distribution suggests 3 groups: an urbanized and industrialized area (Seoul and its neighbouring province), and two naturally occurring areas (Chungbuk and Gyeongnam provinces). Natural occurrence of As appears to be geologically related with Ogcheon metasedimentary rocks and Cretaceous volcanic rocks. Based on the results of the previous studies in the high As sites, the oxidation of sulfides can be a major control on As concentrations in groundwater in the mineralized and altered zone within the area of Cretaceous volcanic rocks. Desorption process under slightly high pH conditions may also be responsible for high As in groundwater in areas of Ogcheon metasedimentary rocks.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.575-585
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• 2007

Microbial control of the geochemical behavior of heavy metals (Cd, Cu, Pb, and Zn) and As in contaminated subsurface soil and sediment was investigated through activation of indigenous bacteria with lactate under anaerobic condition for 25 days. The results indicated that dissolved Cd, Pb and Zn were microbially removed from solutions, which was likely due to the formation of metal sulfides after reduction of sulfate by indigenous sulfate-reducing bacteria. Soils from the Dukeum mine containing a large amount of sulfate resulted in complete removal of dissolved As after 25 days by microbial activities, while there were gradual increases in dissolved As concentration in soils from the Hwabuk mine and sediments from the Dongducheon industrial area which showed low $SO_4{^2-}$ concentrations. Addition of appropriate carbon sources and sulfate to contaminated geological media may lead to activation of indigenous bacteria and thus in situ stabilization of the heavy metals; however, potential of As release into solution after the amendment should be preferentially investigated.

• Economic and Environmental Geology
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• v.56 no.5
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• pp.619-628
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• 2023

In this study, we investigated the feasibility of calcium sulfate fertilizer as a stabilizing agent for As and Hg contaminated farmland soil and its stabilization characteristics in 3 different physical forms (particulate, powder, and solution) through a pot experiment including 34 days of lettuce growth. As and Hg contents of the lettuce grown in the stabilized soils were decreased by at least 70%. However the lettuce yield of the soil stabilized with the solution agent was decreased by 46% due to the overabundance of the nutrients from the solution agent. Thus, if a solution-type agent is planned for agricultural farmland soil stabilization, additional tests for optimal dosage are needed to preserve vegetation growth. In Hg fractionation, a lower concentration of elemental fractions and a higher concentration of residual/sulfide fractions were identified in the soils stabilized with the solution, powder, and pariculate agents in descending order while there were no significant changes in As fractionation. Overall results suggest that calcium sulfate fertilizer can be used as a stabilizing agent, and a solution-type agent could be used when the operation of heavy machinery for the soil stabilization process is impossible.

• Journal of the Mineralogical Society of Korea
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• v.20 no.2 s.52
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• pp.115-124
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• 2007

Electrum-sulfide mineralization of the Youngbogari mine area occurred in two stages of massive quartz veins that fill the fractures along the fault/shear zones in the Precambrian gneiss. Ore mineralogy is simple, consisting of arsenopyrite $(31.4{\sim}33.4atom.%As)$, pyrite, sphalerite $(4.1{\sim}17.6mole%FeS)$, galena, chalcopyrite, argentite, and electrum. Electrum $(60.3{\sim}87.6atom.%Ag)$ is associated with galena, chalcopyrite and late sphalerite infilling the fractures in quartz and sulfides. Fluid inclusion data show that ore mineralization was formed from $H_2O-CO_2-CH_4-NaCl$ fluids $(X_{CO2+CH4}=0.0\;to\;0.2)$ with low salinities (0 to 10wt.% eq. NaCl) at temperatures between $200^{\circ}\;and\;370^{\circ}C$. Gold-silver mineralization occurred later than the base-metal sulfide deposition, at temperatures near $250^{\circ}C$ and was probably a result of cooling and decreasing sulfur fugacity caused by sulfide precipitation and/or $H_2S$ loss through fluid unmixing.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.1
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• pp.1-17
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• 2023

On painting cultural properties to which Orpiment, a traditional yellow mineral pigment, is applied, the color's degeneration is frequently observed. To identify the cause of the degeneration, this study takes a look into orpiment and the various pigments that are mixed into it (Lead White, Lead Red, and Cinnabar) in powder and painting state. The pigment was mixed with Argyo glue and then applied to korean traditional paper and silk. Considering the possibility that alum causes the discoloration, it was applied to the specimen. With a UV tester, the powders and the painted specimens were subjected to a light resistance test in three phases (96 hour). Color changes were measured with a colorimeter and minerals, chemical composition and structural changes were analysed by XRD, SEM/EDS and Raman spectrometers. While the color change of pure Orpiment powder according to the light resistance test was small, the colored specimen became darker. The color change was large in the Orpiment colored on the silk and in the alum-treated specimen. In Orpiment powder was produced white arsenolite as altered orpiment after UV test. In the mixed powder of Orpiment and Lead White were detected only the constituent minerals of Orpiment and Lead White, and no altered substances were produced. Whereas after the UV test, orpiment and arsenolite, which were altered substances of orpiment, and the constituent minerals of Lead White were detected. In the case of mixing the two pigments in the powder state, darkening did not occur even by the UV test. However, the specimens colored with the mixed powder were darkened by the UV test. The color change of Orpiment was different depending on the mixed pigment and base material. The color change was greater in the case of alum treatment than in the case without alum treatment, and it was found that alum also had an influence on the color change of Orpiment.