• 한국지하수토양환경학회지:지하수토양환경
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• 제15권3호
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• pp.1-6
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• 2010

This study investigated the change of metal contamination levels according to amendment of enforcement regulation of the Soil Environmental Conservation Act in Korea. As an analytical result of 87 samples in abandoned metallic mine area, the extracted amount of As, Pb and Cu with aqua regia was 4.3~29.6 times higher than that with hydrochloric acid extraction and the number of samples, which contamination levels were found to exceed soil contamination standards, was also increased. On the other hand, in case of Cd, Zn, and Ni, the number of samples, which contamination levels were found to exceed soil contamination standards, was decreased or similar. These results can be used as a preliminary material in comparison between the soil pollution data accumulated previously and the data obtained by the revised standard method for the examination of soil pollution.

• 한국토양비료학회지
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• 제43권3호
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• pp.296-303
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• 2010

Chromium as a constituent of rocks occurs naturally in the environment in varying concentrations. However, the human activity has changed the geochemical cycle of chromium in the environment and has caused the chromium accumulation in soils. Korean soils revealed a wide range of chromium contents depending on parent material and land use. The total chromium contents of volcanic ash soils in Jeju, which were determined using $HNO_3$ + $HClO_4$ + HF, ranged from 434 to 1,164 mg $kg^{-1}$. The 'ecological' total chromium contents extracted using conc. HCl + conc. $HNO_3$ (aqua regia) in the same soils varied in a lower range of 50-189 mg $kg^{-1}$ (averaged percentage of aqua regia contents in $HNO_3$ + $HClO_4$ + HF contents: 14.9%). Serpentine soils in Andong showed a 'ecological' total chromium content of 309 mg $kg^{-1}$ and against it granitic soils in Andong only 20 mg $kg^{-1}$. In uncontaminated forest soils of Korea, the 'ecological' total chromium contents varied from 4.89 to 106 mg $kg^{-1}$ and the soluble chromium contents determined using 0.1 M HCl ranged from 0.01 to 0.64 mg $kg^{-1}$ (averaged percentage of 0.1 M HCl contents in aqua regia contents: 0.4%). Arable lands contained more soluble chromium than reported in forest soils (averaged soluble chromium: 0.36 and 0.09 mg $kg^{-1}$, respectively). In particular, the soluble chromium contents in greenhouse, orchard and upland soils were higher than in contaminated soils near mine and industrial site (maximum contents: greenhouse 15.3 mg $kg^{-1}$; upland 12.1 mg $kg^{-1}$; orchard 8.29 mg $kg^{-1}$; mine site 4.76 mg $kg^{-1}$; industrial site 2.80 mg $kg^{-1}$). On the basis of these results a accumulation of chromium in some specific arable lands can be assumed, probably by long-continued applications of fertilizers or soil amendments containing chromium. In Korean Enforcement Decree of the Soil Environment Conservation Act soil standards for total chromium do not exist yet.

• 한국지하수토양환경학회지:지하수토양환경
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• 제14권3호
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• pp.32-39
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• 2009

우리나라 토양 중 중금속 자연배경농도를 비교 평가함으로써 토양오염기준 설정을 위한 과학적 근거를 마련하고자 전국 주요 지질단위인 대동층군, 백악기화강암, 옥천층군, 조선누층군, 평안층군, 경상누층군, 쥬라기화강암, 화산암, 변성암등 산림지역 총 92개 지점에 대한 표토를 0.1N 염산 가용성 시험방법 및 왕수 시험방법으로 분석한 결과, 왕수시험방법에 의한 자연함유량 평균값(mg/kg)은 Cd 0.287, Cu 15.26, Pb 18.43, Cr 25.36, Zn 54.27, Ni 17.68, As 6.83으로 조사되었으며, 가용성 시험결과 평균농도(mg/kg)는 Cd 0.040, Cu 0.48, Pb 3.06, Cr 0.09, Zn 1.54, Ni 0.27, As 0.089로 나타났다. 이들 시료의 가용성 평균 농도는 왕수 시험방법의 평균농도에 비하여 각각 Cd 13.9%, Cu 3.1%, Pb 16.6%, Cr 0.4%, Zn 2.8%, Ni 1.5%, As 1.3% 수준으로 낮게 평가되었다. 또한 가용성 시험방법과 왕수 시험방법에 의한 중금속 측정값 간의 상관계수는 0.24~0.88의 범위로 나타났으며 Cd > Pb > Cu > Ni > Cr > Zn $\approx$ As의 순으로 감소하였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제24권6호
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• pp.1-8
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• 2019

This study evaluated the relative extraction ratio (RER) of As and heavy metals (Cd, Cu and Pb) in paddy soils using the two types extractant, 0.05 M EDTA and 0.43 M HNO₃. The RER was calculated by dividing the concentrations of metals obtained by 0.05 M EDTA or 0.43 M HNO₃ extraction by those obtained by aqua regia extraction. The RER of 0.43 M HNO₃ was larger than that of 0.05 M EDTA. Correlation analysis indicated there was statistically significant correlation (p<0.001) between the concentration in aqua regia and 0.05 M EDTA or 0.43 M HNO₃. Especially, Cd showed the higher correlation than other metals. Stepwise multiple linear regression analyses indicated soil pH, CEC, organic matter content, and soil texture all influenced the metal extraction rates and bioavailability of the metals.

• 한국광물학회지
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• 제25권3호
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• pp.123-130
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• 2012

염소-차아염소산 용액을 소성정광에 적용하여 gold와 silver를 효과적으로 용출시키고자 하였다. 염소 : 차아염소산 혼합비율 1.5 : 1, 그리고 NaCl 농도를 1 M으로 적용하였을 때 Au 용출율은 겨우 75%와 81%이였다. 그러나 광액농도를 1%로, 그리고 용출온도를 $65^{\circ}C$로 적용하자 Au 용출율이 100%에 도달되었다. 왕수분해 및 염소-차아염소산 용출 고체 잔유물을 XRD분석을 실시한 결과 석영이 관찰되었다. 따라서 석영 속에 함유된 gold는 염소-차아염소산으로 용출시키지 못할 것으로 사료된다. 따라서 석영 속의 gold를 용출시키기 위해서는 더 작은 미립자로 전처리하거나 더 강력한 산화제를 적용해야 할 것이다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제19권4호
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• pp.45-51
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• 2014

In accordance with the view on remediated soil as a resource, this study assessed the applicability of soil washing with the neutral phosphate for remediation of arsenic (As)-contaminated soil. Three soil samples of different land uses (i.e., rice paddy, upland field and forest land) were collected from the study site, and the aqua regia-extractable As concentrations were 59.2, 30.8 and 53.1 mg/kg, respectively. Among the neutral phosphate reagents, ammonium phosphate showed the highest As washing efficiency. The optimized washing condition was 2-hr washing with 0.5M ammonium phosphate solution (pH 6) and soil to liquid ratio of 1 : 5. The extraction efficiencies of As did not guarantee the residual soil As concentrations to satisfy the Korea soil regulatory level (i.e., Worrisome level) in the three soil samples. To enhance washing efficiency, the As-contaminated soil was submerged in washing solution (1 : 1, w/v) for 24 hr and 1-hr washing with 0.5M ammonium phosphate solution was tested. As extraction efficiencies of 36.1 (rice paddy), 21.4 (upland field) and 26.4% (forest land) were attained, which satisfied the Worrisome level for Region 1 (25 mg/kg of As) in rice paddy, but not in upland field and forest land.

• Bulletin of the Korean Chemical Society
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• 제23권11호
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• pp.1541-1544
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• 2002

The concentration of B in steels is important due to its influence on mechanical properties of steel such as hardenability, hot workability, and creep resistance. An analytical method has been developed to determine B in steel samples by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). National Institute of Standard and Technology Standard Reference Material (NIST SRM) 348a was analyzed to validate the analytical method. The steel sample was digested in a centrifuge bottle with addition of aqua regia and $^{10}B$ spike isotope. Sample pH was then adjusted to higher than 10 to precipitate most matrix elements such as Fe, Cr, and Ni. After centrifugation, the supernatant solution was passed through a cation exchange column to enhance the matrix separation efficiency. B recovery efficiency was about 37%, while matrix removal efficiency was higher than 99.9% for major matrix elements. The isotope dilution method was used for quantification and the determined B concentration was in good agreement with the certified value.

• 한국정밀공학회지
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• 제31권4호
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• pp.353-358
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• 2014

This paper reports a simple, yet effective 1-step surface modification method for stainless steel. Electrochemical etching in dilute Aqua Regia forms hierarchical micro and nanoscale structure on the surface. The surface becomes highly hydrophobic (${\sim}150^{\circ}$) as a result of the etching in terms of static contact angle (CA). However the liquid drops easily pinned on the surface because of high contact angle hysteresis (CAH), which is called a "petal effect": The petal effect occur because of gap between surface microstructures, despite of intrinsic hydrophobicity of the base material. The pore size and period of surface structure can be controlled by applied voltage during the etching. This method can be applied to wide variety of industrial demand for surface modification, while maintaining the advantageous anti-corrosion property of stainless steel.

• 자원환경지질
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• 제18권3호
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• pp.263-276
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• 1985

Building stones can be divided into two groups: raw stone and stone product. In Korea, they consist of granite, diorite, gabbro, andesite, tuff, slate and marble, of which granite is main product. The disribution area is approximately $31,753km^2$. The enterprises of building stone are about 1,500 at present. The granites for building stone are biotite granite, hornblende granite. granodiorite and porphyritic granite, of different colors (white, pink, grey, green and black). The compressive strength of granite ranges from 813 to $1,338kg/cm^2$, hardness from 78 to 101 and water absorption ratio from 0.09 to 0.40%. The weight reduction ratio of granite for 14 hours in aqua regia+$KMnO_4$solution is 0.3~4.5wt.%. There are eighty granite quarries in Korea. Marbles can also be extensively used for building but only a few mines are operated at present.

• 자원리싸이클링
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• 제6권3호
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• pp.36-40
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• 1997

A series of processes has been developed to recover the gold from electronic scrap containing about 200~600 ppm Au. First, mechanical beneficiation including shredding, crushing and screening was employed. Results showed that 99 percent of gold component leaves in the fraction of under 1mm of crushed scrap and its concentration was enriched to about 800 ppm without incineration. The crushed scrap was leached in 50% aqua regia solution and gold was completely dissolved at $60^{\circ}C$ withing 2 hours. Other valuable metals such as silver, copper, nickel and iron were also dissolved. The resulting solution was boiled to remove nitrous compounds in the leachate. Finally, a newly designed electrolyzer was tested to recover the gold metal. More than 99% of gold and silver were recovered within an hour by electrowinning process.