• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.393-404
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• 2005

The environmental problem is a main subject of the 21C and an environment destruction phenomenon by various kinds of environmental materials is reaching serious level. Nations to be classified as the environmental developed country, are born again environmental rich country. And they earn a large income by trade Every kind environmental resource in an international commercial transaction. Especially, the study that a reliability assessment method to prevent to reliability problem to be happened when the solder lead(lead-free solder), non-cd component, non-bromide component(without the polybrominated biphenyls(PBB) and polybrominated diphenyl ethers(PBDE))and hexavalent chromium(Cr VI) clearance component and mercury-free applied to electronic equipment is progressed. As the result of the study for applying of a reliability assessment technique of lead-free solder that recognized the most of urgent problem at the company, combination accelerated life test could taken by adding and appling the part of a humidity acceleration part to Eyring Model which is proposed by R.E.Thomas. The reliability assessment methods study of PWB clean environmental materials is expected to respond to a reliability elevation and environmental material regulation policy spreading all over the world by beginning form Europe.

• 산업경영시스템학회지
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• 제45권4호
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• pp.8-20
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• 2022

The paint removal of fighter jets is just as important as the painting, because perfect paint removal ensures the quality of the exterior painting on the aircraft. However, the current conditions for paint removal work of the ROKAF's are poor. It is identified that the painting process currently implemented by the ROKAF is not only exposed to harmful compounds such as harmful dust and hexavalent chromium, but also consumes a lot of water. Thus, the introduction of advanced facility is considered. This study compares the fighter jets painting removal process currently applied by the Korean Air Force with the improved laser coating removal process of the US Air Force, and conducts an incremental analysis to perform economic analysis for the introduction of advanced facility. Four scenarios were envisioned on the premise of an increase in the number of fighters in the future, incremental analysis shows that laser coating removal method is advantageous in all scenarios. In addition, it is recommended that paint removal cycle keeps the current 12-year and the outsourcing amount to civilian depot is reduced.

• Journal of the Korean Wood Science and Technology
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• 제51권5호
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• pp.321-333
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• 2023

In this study, lignin, a lignocellulosic biomass, was chemically modified to produce polyethyleneimine-grafted lignin (PKL) with maximum hexavalent chromium [Cr(VI)] adsorption capacity. Changes in the physicochemical properties due to the cationization of lignin were confirmed through elemental analysis, Fourier transform infrared spectroscopy, and moisture stability evaluation. Alginate (Alg) beads containing PKL (Alg/PKL) were prepared by incorporating cationic lignin into the Alg matrix to apply the prepared PKL in a batch-type water treatment process. The optimal Alg/lignin mixing ratio was selected to increase the Cr(VI) adsorption capacity and minimize lignin elution from the aqueous system. The selected Alg/PKL beads exhibited an excellent Cr(VI) removal capacity of 478.98 mg/g. Isothermal adsorption and thermodynamic analysis revealed that the Cr(VI) removal behavior of the Alg/PKL beads was similar to that of heterogeneous chemical adsorption. In addition, the bulk adsorbent material in the form of beads exhibited adsorption behavior in three stages: surface adsorption, diffusion, and equilibrium.

• 공업화학
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• 제10권8호
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• pp.1104-1108
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• 1999

본 연구에서는 피혁분에서 크롬을 제거하여 여러 면으로 활용 가능한 단백질자원을 얻고자 하였다. 피혁분은 크롬이 콜라겐사이에 가교결합을 하여 크롬-콜라겐염(Cr-collagenate)을 형성하므로 1단계 공정에서 $Ca(OH)_2$용액에 침지(steeping)하여 팽윤(swelling)-팽창(plumping)시켜, $H_2SO_4$용액으로 크롬을 용출시켰다. 2단계 공정에서 NaOH용액으로 팽윤-팽창시키고 $H_2O_2$용액으로 용해도가 큰 Cr(VI)으로 산화하여 $H_2SO_4$용액으로 용출시켜 탈 크롬을 마무리하였다. 1단계 공정에서 $3%-Ca(OH)_2$용액, $0.8%-H_2SO_4$용액으로 2단계 공정에서 0.1%-NaOH용액, $3%-H_2O_2$용액, $1%-H_2SO_4$용액으로 순차적으로 침지하여 효율적으로 완전 탈 크롬을 할 수 있었다. 완전 탈 크롬된 피혁분에는 수분 10.68%일 경우, 조 단백질이 79.81% 함유하였으며, 각 공정의 침지용액들은 3회까지 반복 사용하여도 완전히 크롬을 제거할 수 있었다.

• 한국토양환경학회지
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• 제4권2호
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• pp.11-31
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• 1999

회분식 및 연속류 주상 실험을 통해 인공 조제 지하수로부터 입상활성탄에 의한 6가크롬 (Cr(VI)) 제거에 대한 연구를 수행하였다. 실험에 적용된 변수로는 용액의 pH, 용존산소의 존재여부를 사용하였고 2가철(Fe(II))로 활성탄을 전처리한 것을 처리하지 않은 활성탄과 그 결과를 비교하였다. 용액의 pH를 4.0에서 7.5로 증가 시킴에 따라 무처리 및 Fe(II)로 전처리한 활성탄 모두에 흡착된 Cr(VI)의 양이 현저히 감소하였다. 용존산소가 배제 (무산소조건) 되었을 경우 Cr(VI) 제기량이 증가하였는데, 이는 Cr(VI)의 Cr(III)로의 환원 때문으로 추측된다. 그러나, Fe(II)에 의한 활성탄의 전처기는 Cr(Vl)제거에 거의 영향을 미치지 않았다 흡착된 Cr(VI)를 추출하기위해 0.01M $K_2$$HPO_4$와 침전 또는 흡착된 Cr(III)를 제거하기위해 0.02N $K_2$$HPO_4$로 세척하였는데, 이는 Cr(VI)로 흡착능이 고갈된 활성탄 재생의 한 방법으로 고려될 수 있으리라 사료된다. 재생된 활성탄은 본래의 활성탄보다 큰 흡착능을 보였는데, 그 이유는 Cr(VI)가 낮은 pH에서 흡착이 잘되며 또 Cr(III)로 환원되기 때문으로 사료된다. 산세척수중의 Cr(III)의 존재는 비교적 산성 조건하에서 Cr(VI)의 Cr(III)로의 환원을 보여주는 증거로 사료된다. 5회의 재생 및 재사용 실험에서 이 재생방법이 흡착능을 악화시키는 것 없이 지속적으로 사용될 수 있음을 알 수 있었다.

• 환경영향평가
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• 제8권2호
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• pp.1-8
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• 1999

The research centers on the concentration profile and risk assessment of toxic metals for ambient air in Taejon industrial complex. Airborne concentrations of each toxic metal for risk assessment were obtained from 2-year sampling by high volume air sampler and analysis by ICP-MS and ICP-AES in the complex. The long-term arithmetic mean of human carcinogen, arsenic, hexavalent chromium and nickel subsulfide was 5.53, 2.16 and $3.46ng/m^3$ while the mean of probable human carcinogen, beryllium, cadmium and lead was 0.08, 2.35, $293.29ng/m^3$, respectively. And the long-term arithmetic mean concentration of non-carcinogenic metal, manganese was $55.91ng/m^3$. The point risk estimate for the inhalation of carcinogenic metals was $3.6{\times}10^{-5}$, which was higher than a risk standard of $10^{-5}$. About 75% of the cancer risk was to the inhalation of human carcinogen, arsenic. Thus, it is necessary to properly manage arsenic risk in Taejon industrial complex. The point hazard index by the inhalation of manganese was 1.1. Therefore, an investigation into Taejon industrial complex is needed to obtain more fine long-term concentration data for airborne non-carcinogenic metals including manganese.

• 한국세라믹학회지
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• 제51권5호
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• pp.505-510
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• 2014

The properties of black ceramic pigments including thermal and glaze stability were systematically investigated so that these pigments could be used to decorate porcelain products. Various compositions of $(Ni,Mn)(Fe,Cr,Mn)_2O_4$ and $Co(Fe,Cr)_2O_4$ powders were synthesised using a solid state reaction method. The obtained $Co(Fe,Cr)_2O_4$ and $(Ni,Mn)(Fe,Cr,Mn)_2O_4$ powders showed single phases of spinel structure after calcination processes at $1000^{\circ}C$ and $1200^{\circ}C$, respectively. CIE $L^*a^*b^*$ colourimetric parameters of glazed $Co(Fe,Cr)_2O_4$ and $(Ni,Mn)(Fe,Cr,Mn)_2O_4$ pigments were analyzed according to the different amounts of Cr substitution. In addition, the amount of $Cr^{+6}$ remaining in the $Co(Fe,Cr)_2O_4$ and $(Ni,Mn)(Fe,Cr,Mn)_2O_4$ pigments was also measured.

• Journal of the Korean Wood Science and Technology
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• 제29권1호
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• pp.52-59
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• 2001

본 연구는 양생방법과 양생온도에 따른 소나무, 낙엽송, 북양가문비나무 변재부에서 CCA와 CCFZ의 정착특성을 조사하기 위하여 수행되었다. 방부제 유효성분의 정착 정도는 6가크롬의 3가크롬으로 환원율에 의해 결정하였으며, 연구결과를 토대로 수종, 방부제, 양생방법, 양생온도의 조합별 적정 양생기간을 예측하였다. 양생방법에 관계없이 양생온도가 높을수록 방부제 유효성분들의 정착이 크게 가속되었으며, 건조양생에 비하여 비건조양생시 정착이 빨리 진행되었다. 수종간의 양생속도는 양생방법과 방부제의 종류에 관계없이 전반적으로 소나무>낙엽송>북양가문비나무 순으로 빨랐고, 소나무를 대상으로 비교한 방부제간의 정착속도는 CCA 2호>CCA 3호>CCFZ의 순이었다. 양생방법에 관계없이 양생온도와 양생 소요기간간의 상관이 매우 우수하여 처리재 양생장소의 대기온도에 의해 수종과 방부제의 조합별 적정 양생기간을 거의 완벽하게 예측할 수 있었다.

• Environmental Analysis Health and Toxicology
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• 제20권2호
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• pp.179-186
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• 2005

Particulate materials (PM) less than 10 ${\mu}m$ in diameter are of special interest in air pollution because they are respirable and responsible for the increasing mortality rate of lung cancer and cardiovascular diseases. These particles are often referred to as $PM_{10}$ and they are divided into a coarse fraction and a fine fraction which is also often referred to as $PM_{25}$. In this study, we monitored the TSP, $PM_{10},\;PM_{2.5}$ concentration of ambient air collected in northern part of Seoul in early spring and measured the concentration of heavy metals; Cr, Mn, Zn, As, Cd, and Pb. All the heavy metals were found in the collected particles and the concentrations were variable in the $PM_{10},\;and\;PM_{2.5}$ respectively. The detected concentration ranges were Cr: $ND\~2,889ng/m^3,\;Mn:2.4\~257.9ng/m^3,\;Zn:ND\~353.7ng/m^3,\; As:ND\~22.3ng/m^3,\;Cd:0.1\~2.9ng/m^3,\;and\;Pb:ND\~392.2ng/m^3$ in fine particles. Heavy metal toxicity of the particles were also tested in $H_9C_2$ cell line derived from rat cardiomyocytes. As for the results of health risk assessment calculated by unit risk of IRIS, heavy metals in ambient air of Seoul metropolitan area were found to be responsible for the increase of total excess cancer risk. Among them, chromium (hexavalent) was found to be the most risky in fine particles of ambient air collected in the northern part of Seoul in early spring.

• Environmental Engineering Research
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• 제21권2호
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• pp.152-163
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• 2016

Present study investigates the potential of cassava peel and rubber tree bark for the removal of Cr (VI) from aqueous solution. Removal efficiency of more than 99% was obtained during the kinetic adsorption experiments with dosage of 3.5 g/L for cassava peel and 8 g/L for rubber tree bark. By comparing popular isotherm models and kinetic models for evaluating the kinetics of mass transfer, it was observed that Redlich-Peterson model and Langmuir model fitted well ($R^2$ > 0.99) resulting in maximum adsorption capacity as 79.37 mg/g and 43.86 mg/g for cassava peel and rubber tree bark respectively. Validation of pseudo-second order model and Elovich model indicated the possibility of chemisorption being the rate limiting step. The multi-linearity in the diffusion model was further addressed using multi-sites models (two-site series interface (TSSI) and two-site parallel interface (TSPI) models). Considering the influence of interface properties on the kinetic nature of sorption, TSSI model resulted in low mass transfer rate (5% for cassava peel and 10% for rubber tree bark) compared to TSPI model. The study highlights the employability of two-site sorption model for simultaneous representation of different stages of kinetic sorption for finding the rate-limiting process, compared to the separate equilibrium and kinetic modeling attempts.