• Resources Recycling
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• v.25 no.4
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• pp.32-41
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• 2016

The precipitation test, which is the last step of magnesium recovery process consisting of three processes (pre-precipitation, selective dissolution of magnesium, precipitation) is performed to obtain magnesium sulfate powder from seawater. In the study, we succeed in precipitating the magnesium sulfate by adding acetone into the solution of magnesium over 4 times concentrated from seawater. The yield efficiency of magnesium sulfate increases with increasing pH and the ratio of added acetone. More than 99% of magnesium is obtained as magnesium sulfate hydrate ($MgSO_4{\cdot}6H_2O$) under the following conditions; pH 1.0 ~ 1.5, and the ratio of solution and acetone 1 : 1.5 (v:v). The acetone used in the precipitation process is recovered by the fractional distillation.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.110-110
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• 2015

표면에너지는 계면특성을 지배하는 핵심인자로 디스플레이의 터치 스크린 패널 공정, 이종소재의 접합, 금속의 클래딩 등 실제 산업에 있어서 매우 중요하다. 표면에너지는 코팅과 본딩 이론에 있어서 기본이 되는 물리량으로 표면에너지가 높을수록 코팅 또는 박막 증착시 코팅, 증착이 용이하며 이종소재의 접합도 쉽게 일어난다. 본 연구에서는 플라즈마 표면처리시 산소 분율의 변화에 따른 기판의 표면에너지와 코팅층과 기판의 부착력의 변화에 대해 연구하였다. 연구의 주요 기판으로 ITO, PET 기판을 사용하였고, 표면 에너지 변화를 확인하기 위해 기판을 상온 상압 플라즈마에 노출시켰다. 플라즈마는 아르곤(Ar)의 공급량을 20 LPM으로 고정하고 산소($O_2$)의 공급량을 0 sccm에서 40 sccm 까지 10 sccm 간격으로 변수를 주었다. 표면에너지 값은 기판 위에 형성된 액체의 접촉각을 통해 도출하였다. 표면에너지 측정 액체로 증류수(deionized water)와 디오도메탄(diiodo-methane)을 사용하였다. 표면에너지는 산소분압이 10 sccm에서 최대값인 76 mJ/m2으로 증가한 후 20 sccm까지 유지하다 다시 직선적으로 감소하였다. 기판에 증착된 크롬 박막의 부착력은 스크래치 테스트를 통해 측정하였다. 표면에너지의 증가와 비례하게 부착력은 증가하였고 표면에너지가 감소하는 범위에서는 부착력도 감소하였다. 기판과 코팅층의 부착력 증가 원인 중 하나인 계면 산화물 층의 생성 여부를 알아보기 위해 auger electron spectroscopy (AES) 분석을 진행하였다. AES 분석을 통해 플라즈마 표면처리시 기판과 코팅층의 계면 산화물층의 두께가 표면에너지의 변화와 비례하게 증가하였다가 감소하는 것을 확인하였다. 산소분압이 10 sccm 이었을 경우 산화물층의 두께가 가장 두꺼웠다. 또한 계면의 화학적 결합 상태를 알아보기 위해 X-ray photoelectron spectroscopy (XPS) 분석을 진행하였으며 산소 분율의 변화에 따라 크롬 산화물의 양이 증가하였다 감소하는것을 확인하였다. 이 연구를 통해 산소를 포함한 플라즈마 표면개질이 기판과 코팅층의 부착력 증가에 영향을 끼침을 확인 할 수 있었다. 또한 이를 응용하여 부착력 증가가 필요한 다양한 분야에서도 쉽게 적용시킬 수 있을 것이다.

• Applied Microscopy
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• v.32 no.4
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• pp.311-317
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• 2002

There is great requirement on the TEM specimen preparation method with particle size selectivity as a prerequisite for the quantitative structure analysis on the materials such as gibbsite powder, which generally forms a large agglomerate and shows a variation of transition process depending on their sizes. In this experiment, we made an attempt to give a methodology for the TEM specimen preparation of powder with the size selectivity. After mixing 1 wt% gibbsite powder with ethanol solvent, gibbsite suspension was prepared by application of ball-milling and ultrasonification with addition of 0.25 vol% dispersion agent, Darvan C, which was diluted into distilled water by the ratio 1:19. Appling the static sedimentation method to gibbsite suspension after estimation of the sedimentation time by the measurement of accumulative concentration variation, we acquired TEM specimens with well-dispersed and size selected gibbsite particles in nm scale. Overall picture of each sample was taken by SEM and morphology of each dispersed particle was imaged by TEM. Raw and processed gibbsite powders were also examined by XRD to investigate whether they were suffered from phase change during the process or not.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.487-490
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• 2005

재생 가능한 자원인 동식물성 기름으로부터 만들어지는 수송용 연료 바이오디젤은 낮은 대기오염물질 배출과 $CO_2$ Neutral 특성으로 환경친화적인 연료로 인정올 받으며 전세계적으로 그 생산량이 급격히 증가하고 있다 한국에서는 년간 20만톤의 폐식용유가 배출되며 이중 약 10만톤이 회수 가능한 것으로 추산된다. 폐식용유의 무단 폐기로 인한 수질오염과 폐기물의 자원 재활용 및 에너지 생산 관점에서 폐식용유를 바이오디젤 원료로 사용하는 연구가 많이 진행되었다. 높은 함량의 유리지방산을 함유한 폐식용유를 효율적으로 전이에스테르화(methanolysis) 하기 위해서는 먼저 산 촉매를 이용한 유리지방산의 전환 제거가 필요하다 본 연구에서는 다양한 종류의 강산성 이온교환 수지를 폐식용유의 전처리(pre-esterification)용 고체 산 촉매로 회분식 반응기에서 테스트하였으며 그 결과 Amberlyst-15가 유리지방산의 에스테르화 반응에 가장 적합한 것으로 나타났다. 회분식 반응기에서 도출된 최적 전처리 반응조건을 적용한 200시간 이상의 연속 전처리 운전결과 폐식용유에 함유된 $5\%$의 유리지방산이 $90\%$이상 전환제거 되었다 전처리 반응 후의 폐식용유를 균질계 염기촉매(KOH) 존재하에 메탄올과 전이에스테르화 반응을 시킨 결과 바이오디젤로 불리는 지방산메틸에스테르(Fatty Acid Methyl Ester, FAME)의 생산 수율은 $85\%$로 얻어졌으며 국내 바이오디젤 표준 규격에 따른 연료특성 분석 결과 FAME의 농도 규격을 제외한 모든 항목이 국내 규격을 만족하였다 폐식용유 바이오디젤의 FAME 농도가 $94.3\%$로 국내 규격$96.5\%$에 미달하는 문제는 식물성 원료유로 제조한 고순도 바이오디젤과 혼합 사용하거나 감압 증류 공정을 통해 고농도의 폐식용유 바이오디젤을 제조하여 해결 가능하다. 대전시 신성동 소재의 음식점에서 수거한 폐식용유를 원료로 하여 생산한 바이오디젤의 차량 배출가스 실증 테스트 결과 경유 차량의 주 오염물질인 PM과 Soot 및 기타 오염물질의 배출량은 감소하였으나 NOx의 배출량은 약간 증가하는 것으로 나타났다

• Resources Recycling
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• v.18 no.5
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• pp.44-51
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• 2009

Fundamental study has been made on the recovery of copper from the electronic scrap by hydrometallurgical process. Nitric acid was used as a leaching agent to dissolve the metals such as Cu, Sn, Pb, Fe etc. from the crushed electronic scraps. TBP was employed to extract nitric acid from the strong nitric acid leaching solutions and to reclaim nitric acid. From the experimental results, Cu was effectively leached by 3.0-4.0 M nitric acid. And 95% of nitric acid in the leaching solution was extracted by 60% TBP, and 98% of nitric acid was stripped from the loaded organic phase by distilled water and it was possible to reuse as a leaching agent.

• Journal of Korean Society on Water Environment
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• v.36 no.2
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• pp.137-147
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• 2020

A direct contact membrane distillation (DCMD) was applied to treat strong nitrogenous wastewater of anaerobic digestion supernatant (ADS) and human urine (HU). The ammonia transfer was evaluated in terms of specific ammonia transfer (SAT) value, which is the ratio of total ammoniacal nitrogen divided by the amount of water transferred. The acidification resulted in low SAT values and high quality of produced water. The ammonia transfer control in the acidic condition was stronger for HU than ADS due to higher alkalinity (pH 8.8) and ammonia concentration (5700 mg-N/L) of HU. Acidified HU at pH 4 exhibited a SAT value of 1.64 × 10^-5, which was significantly smaller than the SAT value of 3.00 × 10^-3 for the original HU. The low pH enhanced the water flux for ADS, but HU showed a steep decrease in water flux due to enhanced fouling. It was considered that the fouling intensity in acidic conditions depends on the characteristics of the wastewater source. The major foulants on the MD membrane were NaCl, CaCO₃ and CuSO₄ as recognized by the SEM-EDS. Acidified ADS and HU at pH 4 showed relatively high N content of 8.18 % and 28.03 %, respectively, as organic fouling.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.512-515
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• 2008

The removal of iron from neodymium chloride solution was carried out by solvent extraction using Alamine 336 in kerosine. The effect of Alamine 336, hydrochloric acid and chloride ion concentrations on the extraction of Fe were studied. The results showed that Alamine 336 as an extractant for removal of iron was effective and the extraction percentage of iron was increased with increasing hydrochloric acid and chloride ion concentration in aqueous solution. The extraction of 99% of iron is attained at a ratio of A/O = 4 by distilled water. The stripping yield of iron from loaded Alamine 336 decreased with decreasing hydrochloric acid concentration in stripping solution.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.125-133
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• 2016

With the aim of using a filler material in a conductive paste, fine Cu nanoparticles were synthesized through the high-speed chemical reaction between cuprous oxide ($Cu_2O$) powder and sulfuric acid in distilled water. Under external temperature of $7^{\circ}C$, sulfuric acid concentration of 48%, and $Cu_2O$ amount of 30 g, the $Cu_2O$ particles were eliminated and slightly aggregated Cu nanoparticles were synthesized. Futhermore, Cu nanoparticles of 224 nm, in which the aggregation between particles was obviousiy much suppressed, were synthesized with the choice of an additive. In the particle sample, occasionally there are coarse particles formed by the aggregation of fine nanoparticles and weak linkages between the nanoparticles. However, the coarse particles were destroyed and the linkages were broken after mixing with a resin formulation, indicating the behavior of untangling the aggregation between nanoparticles.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.3 s.40
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• pp.33-38
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• 2006

Aerosol slurry composed of dielectric materials, distilled water, and deflocculants was sprayed on the substrates, through a high-pressure spray gun as an aerosol. The coated layers were cofired together with $Al_{2}O_{3}$ substrates and green sheets on which the inner connectors were printed. Although the coating rate of coated layers strongly depended on slurry viscosity, spray shape, and the pressure of the spray gun, the coated density was not changed. Buried conductors were maintained as printed by high pressure spray coating method, because the pressing process was not used. At the optimum condition of air controller step 3-4 and slurry viscosity c.p 2000-4000, dense and uniform layers could be achieved. Comparing with conventional lamination process using green sheets, spray coating method enabled thin dielectric layers of $20{\sim}50{\mu}m$.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.351-354
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• 2002

This research discussed about the substrate transport phenomena in anaerobic biofilm. Three anaerobic fixed biofilm reactors were filled with the sludge of anaerobic digestor from Suyoung wastewater treatment plant. After 15 days of biofilm formation periods, suspended solids within the reactors were removed, and each fixed biofilm reactor was supplied with synthetic wastewater of different concentration of 8.00 mgTOC/L, 9.76 mgTOC/L and 18.97 mgTOC/L, respectively. The experimental results in conjunction with substrate transfer phenomena indicated that data - thickness, substrate removal rate. At the low influent substrate concentration(reactor 1 : 8.00 mgTOC/L, reactor 2 : 9.76 mgTOC/L), the rate of substrate utilization($k_v$), effective diffusivity($D_{eff}$) of substrate in biofilm were similar. While $k_v$ and $D_{eff}$ of the high influent substrate concentration(reactor 3 : 18.97 mgTOC/L) were higher than data in the reactors of the low influent substrate concentration.