• 대한화학회지
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• 제52권4호
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• pp.369-379
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• 2008

• Advances in environmental research
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• 제5권2호
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• pp.125-140
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• 2016

The paper is focused on the economic analysis of two hydrometallurgical processes for recovery of yttrium and other rare earth elements (REEs) from fluorescent phosphors of spent lamps. The first process includes leaching with sulphuric acid and precipitation of a mixture of oxalates by oxalic acid, the second one includes leaching with sulphuric acid, solvent extraction with D2EHPA, stripping by acid and recovery of yttrium and traces of other rare earths (REs) by precipitation with oxalic acid. In both cases the REEs were recovered as oxides by calcination of the oxalate salts. The economic analysis was estimated considering the real capacity of the HydroWEEE mobile's plant ($420kg\;batch^{-1}$). For the first flow-sheet the cost of recycling comes to $4.0{\euro}kg^{-1}$, while the revenue from the end-product is around $5.40{\euro}kg^{-1}$. The second process is not profitable, as well as the first one, taking into account the composition of the final oxides: the cost of recycling comes to $5.2{\euro}kg^{-1}$, while the revenue from the end-product is around $3.56{\euro}kg^{-1}$. The process becomes profitable if the final RE oxide mixture is sold for nearly $50{\euro}kg^{-1}$, a value rather far from the current market prices but not so unlikely since could be achieved in the incoming years, considering the significant fluctuations of the Res' market.

• 유기물자원화
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• 제28권3호
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• pp.5-14
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• 2020

본 연구는 돈분과 사과착즙박 혼합 혐기소화액의 호기성 처리 과정에서 황산(H₂SO₄)을 이용한 혐기소화액의 pH를 7.0과 6.5 조절 처리가 암모니아 휘발과 화학적 특성 변화에 미치는 영향을 구명하기 위하여 수행하였다. 혐기소화액은 0.3 ㎥ air/㎥·min 조건에서 60일 동안 폭기처리를 실시하였다. 무처리구의 혐기소화액은 호기성 액비화 과정 중 pH가 상승하고, EC와 T-N 함량이 감소하는 경향을 나타내었다. 황산 무처리 혐기소화액은 pH가 높아 액비화 과정에 암모니아 농도가 172.6 mg/L로 높았으나 황산 처리 pH 조절 혐기소화액은 암모니아(NH₃) 발생이 유의적으로 감소되었다. 황산 무처리 혐기소화액은 액비화 과정 중 암모늄태 질소 함량이 47.2% 감소되었다. 혐기소화액의 pH 조절 처리구는 암모늄태 질소의 함량이 황산 처리 pH 조절 처리구에 비하여 높았다. 또한, 황산(H₂SO₄)처리는 혐기소화액에서 질소, 인산 함량의 증가에 영향을 주어 비료 성분이 높아지는 효과를 나타내었다. 따라서 혐기소화액의 황산 첨가에 의한 pH 조절은 호기성 액비화 공정에서 암모니아 휘산 저감과 질소 함량을 높이기 위한 유용한 방법으로 활용될 수 있을 것이다.

• 상하수도학회지
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• 제18권5호
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• pp.638-648
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• 2004

In many drinking water treatment plants, chlorination process is one of the main techniques used for the disinfection of water. This disinfecting treatment leads to the formation of haloacetic acid (HAAs). In this study, headspace solid-phase microextraction (HS-SPME) was studied as a possible alternative to liquid-liquid extraction for the analysis of HAAs in drinking water. The method involves direct derivatization of the acids to their methyl esters without methyl tert-butyl ether (MTBE) extraction, followed by HS-SPME with a $2cm-50/30{\mu}m$ divinylbenzene/carboxen/polydimethylsiloxane fiber. The effects of experimental parameters such as selection of SPME fiber, the volume of sulphuric acid and methanol, derivatization temperature and time, the addition of salts, extraction temperature and time, and desorption time on the analysis were investigated. Analytical parameters such as linearity, repeatability and limit of detection were also evaluated. The $2cm-50/30{\mu}m$-divinylbenzene/carboxen/polydimethylsiloxane fiber, sulphuric acid of 1ml, methanol of 3ml, derivatization temperature of $50^{\circ}C$ derivatization time of 2hrs, sodium chloride salt of 10g, extraction time of 30 minutes, extraction temperature of $20^{\circ}C$ and desorption time of 1 minute at $260^{\circ}C$ were selected as the optimal experimental conditions for the analysis of HAAs. The linearities ($r^2$), relative standard deviations (%RSD) and limits of detection (LOD) for HAAs were 0.9978~0.9991, 1.1~9.8% and $0.05{\sim}0.2{\mu}g/l$, respectively.

• Restorative Dentistry and Endodontics
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• 제20권2호
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• pp.843-855
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• 1995

Occupational Dentistry was introduced in Korea about 70 years ago. During the colonial period occupied by Japan till 1945, there were few documents about industrial dentistry, furthermore most cases of occupational diseases and accidents might have been concealed intentionally by the colonial government. After being an independent country, several dentists made efforts to set up 'Preventive Dentistry for Workers' performing specific oral health surveys, even though which were stopped by Korean War. In 1960s' and 1970s', some investigations of oral status were carried out intermittently for specific small groups;white-collar workers, mentally retarded person, buddhist monks and crews of ocean liners. At the same time there was important study in Korean history of occupational dentistry, which was 'a comparison of the oral hygiene conditions in the female workers of a spinning factory at intervals of 30 years.' In 1980s', young researchers began to give attention to erosion of the teeth due to sulphuric acid in the acid-related industry and dental caries due to sugar and flour in the sweets industry. After being democratic labor union movement activated in 1987, hidden and suppressed occupational diseases under the military dictatorship were exposed and flushed in the newspapers. It was shocking for all people that 15-year old boy had been dead due to mercury intoxication after 3-month employment in 1988. In 1990s', the activity for studying oral status of workers in their workplaces was launched and 'Occupational Accidents and Diseases in Oral and Maxillofacial Field' was published. And also The Korean Association of Occupationl Dentistry was established. Oral health examination of workers at the time of employment and of workers exposed to 5 special chemicals at the time of routine special health examination was adopted in 1992, and epocally oral health examination was also included in periodic routine examination of workers' health in 1995. So, occupational dentistry in Korea should cope with the changing needs of working environment and the altering scheme of health examination.

• 동력기계공학회지
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• 제13권3호
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• pp.33-39
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• 2009

The aim of this study is to analyze the welds characteristics of the 205 stainless steel pipe for application of street pole material. The welds corrosion behavior of STS 205 pipe in 0.1 N sulphuric acid solution and 5% NaCl solution at room temperature was studied using both salt spray test and potentiodynamic polarization experiment. The morphology and components of corrosion products on surface of STS 205 pipe welds were investigated using SEM/EDX. The tensile strength and yield strength values of STS 205 plate were 715 MPa and 369 MPa respectively. The microvickers hardness values of STS 205 pipe welds were slightly increased than that of STS 304 pipe welds. Corrosion current density($I_{corr.}$) and critical current density($I_{crit.}$) values of STS 205 pipe welds in 3.5% NaCl solution were $1.89{\times}10^{-6}$ $A/cm^2$ and $15.8{\times}10 ^{-6}$ $A/cm^2$. The corrosion resistance of SIS 205 pipe welds was similar to its STS 304 pipe welds. The STS 205 and 304 pipe welds passive films were chromium oxide. Especially, the STS 205 pipe welds showed good corrosion resistance in 0.1 N sulphuric acid. This is attributed to the forming of protective chromium oxide on the surface of STS 205 pipe welds.

• 콘크리트학회논문집
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• 제14권3호
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• pp.409-419
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• 2002

Nowadays, antiwashout underwater concrete is widely used for constructing underwater concrete structures but they, especially placed in marine environment, can be easily attacked by chemical ions such as SO$\^$2-/$\_$4/ Cl$\^$-/ and Mg$\^$2＋/, so the quality and capability of concrete structures go down. In this paper, to solve and improve those matters, flyash and GGBFS(ground granulated blast furnace slag) were used as partial replacements for ordinary portland cement. As results of experiments for fundamental properties of antiwashout underwater concrete containing 10, 20, 30％ of flyash and 40, 50, 60 ％ of GGBFS respectively, setting time, air contents, suspended solids and pH value were satisfied with the "Standard Specification of Antiwashout Admixtures for Concrete" prescribed by KSCE, and also slump flow, efflux time and elevation of head were more improved than that of control concrete. From the compressive strength test, it was revealed that the antiwashout underwater concrete containing mineral admixtures(flyash and GGBFS) is more effective for long term compressive strength than control concrete. An attempt to know how durable when they are under chemical attack has also been done by immersing in chemical solutions that were x2 artificial seawater, 5 ％ sulphuric acid solution, 10％, sodium sulfate solution and 10％ calcium chloride solution. After immersion test for 91days, XRD analysis was carried out to investigate the reactants between cement hydrates and chemical ions and some crystalline such as gypsum ettringite and Fridel′s salt were confirmed.

• Natural Product Sciences
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• 제27권3호
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• pp.208-215
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• 2021

𝛽-Patchoulene (𝛽-PAE) is a tricyclic sesquiterpene which performed many potential bioactivities and can be found in patchouli oil but in very low concentration. This study aimed to obtained 𝛽-PAE in high concentration by conversion of patchouli alcohol (PA) in patchouli oil under acid catalyzed reaction. Patchouli oil was fractinated by vacuum distillation at 96 kPa to get the fraction with the highest PA content. H₂SO₄ and ZnCl₂ were used respectively as homogeneous and heterogeneous acid catalysts in the conversion reaction of the selected fraction. Patchouli oil, the fractions and the products were analysed by using GC-MS and FTIR instruments. Moreover, the interaction of 𝛽-PAE to COX-2 protein was studied to understand the antiinflammation activity of 𝛽-PAE. The results showed that patchouli oil contains 25.3% of PA. The selected fraction which has the highest PA content (70.3%) was distilled at 151 - 152 ℃. The application of ZnCl₂ catalyst in conversion reaction did not succeed. In contrast, H₂SO₄ as a catalyst in acetic acid solvent succeeded in converting the overall fraction of PA to 𝛽-PAE. Furthermore, the molecular docking study of 𝛽-PAE against COX-2 enzyme showed van der Waals and alkyl-alkyl stacking interactions on ten amino acid residues.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2003년도 가을 학술논문집
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• pp.196-201
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• 2003

제염이란 방사능에 오염된 물체로부터 방사능을 어느 수준 이하로 떨어뜨리는 모든 종류의 작업을 말한다. 본 논문에서는 제염 방법 중의 한가지인 전해 연마 제염법을 이용한 방사선 오염제거에 대하여 실험을 통하여 기술하였다. 알파선과 베타선에 오염된 각각의 SUS 시편을 사용하여 두 가지 방사선에 대한 제염도를 비교해 보았고, 베타선에 오염된 SUS 및 Carbon steel 시편을 사용한 각 전해액에 대한 제염 실험이 수행되었다. 전해액으로서는 황산, 인산, 질산, 구연산 및 옥살산 등을 사용되었다. 전해액의 종류, 통과하는 전류의 세기 및 시간에 따라 각 시편에 대한 제염도의 차이를 비교, 분석 할 수 있었다.

• Journal of Electrochemical Science and Technology
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• 제4권2호
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• pp.81-87
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• 2013

Inhibition of corrosion of mild steel in sulphuric acid by acidic extract of Jatropha Curcas leaves has been studied using weight loss and thermometric measurements. It was found that the leaves extract act as a good corrosion inhibitor for mild steel in all concentrations of the extract. The inhibition action depends on the concentration of the Jatropha Curcas leaves extract in the acid solution. Results for weight loss and thermometric measurements indicate that inhibition efficiency increase with increasing inhibitor concentration. The adsorption of Jatropha curcas leaves extract on the surface of the mild steel specimens obeys Langmuir adsorption isotherm. Based on the results, Jatropha curcas leaves extract is recommended for use in industries as a replacement for toxic chemical inhibitors.