• 대한환경공학회지
• /
• 제38권11호
• /
• pp.603-610
• /
• 2016

본 연구에서는 폐 알칼리망간전지 분말(spent alkaline manganese battery powder, SABP <8 mesh)의 산 침출액으로부터 분리한 망간이온을 이용하여 산화-중합반응 촉매인 버네사이트를 제조하였고, 1-naphthol (1-NP)을 대상으로 페놀계 화합물의 제거 반응성을 조사하였다. 망간산화물의 결정상과 반응성은 순수 망간시약($MnSO_4$, $MnCl_2$)을 사용하여 합성한 망간산화물(manganese oxide, MOs) 및 기존의 McKenzie 합성방법에 의한 Acid birnessite (A-Bir)의 결과와도 비교 평가하였다. SABP에 존재하는 망간과 아연이온은 과산화수소 존재 하에서의 황산 침출($1.0M\;H_2SO_4+10.5%\;H_2O_2$, solid/liquid (S/L)비=1/10 g/mL, $60^{\circ}C$)을 통해 각각 약 96%와 98% 회수하였다. 산 침출액으로부터 망간이온은 수산화물(NaOH) 침전을 통해 pH 8과 pH>13 조건에서 각각 69.0%와 94.3% 분리하였다. 1-NP 제거능을 토대로 SABP 산 침출액으로부터 알칼리(NaOH) 수열합성법에 의한 망간산화물의 제조를 위한 적정 OH/Mn 혼합비(M/M)는 6.0이었고, XRD 분석을 통해 버네사이트(${\delta}-MnO_2$) 결정상을 가짐을 확인하였다. pH 8 (${Mn^{2+}}_{(aq)}$)과 pH>13 ($Mn(OH)_{2(s)}$)에서 회수한 망간을 사용하여 얻은 망간산화물의 1-NP 제거 반응속도(k, at pH 6)는 각각 0.112, $0106min^{-1}$으로서 $MnSO_4$ 시약을 사용하여 얻은 망간산화물의 결과($0.117min^{-1}$)와 유사하였다. 이상의 연구를 통해 폐 알칼리망간전지 분말로부터 얻은 버네사이트는 미량 유해물질 제거를 위한 산화-중합 반응 촉매로 활용 가능함을 알 수 있었으며, 버네사이트 제조를 위한 폐 알칼리망간전지의 재활용 흐름도를 제시하였다.

• Progress in Superconductivity
• /
• 제4권1호
• /
• pp.90-93
• /
• 2002

The sintering process of BSCCO 2223 tapes is a complex process that is very sensitive to parameters, such as temperature, oxygen partial pressure, heating and cooling rate and holding time. During the first heat treatment, 2212 phase of precursor powder is partially transformed into 2223 phase and some residual secondary phases, such as $(Bi,Pb)_2$$Sr_2$CuO／sub y／(2201), $(Ca,Sr)_2$CuO／sub y／(2/1AEC), (Ca,Sr)／sub 14／Cu／sub 24／O／sub 41／(14／24 AEC) etc. The secondary phases are difficult to be removed from the BSCCO 2223 matrix on the heat treatment. These secondary phases degrade the critical current density. In order to minimize the amount and size of alkaline earth cuprate(AEC) particles step heat treatment is applied during the first heat treatment under the varying atmosphere. Experimental results showed that by adapting the step heat treatment process, the amount and particle size of the secondary phases in the final tapes are decreased. Consequently, the BSCCO 2223grain texture and Jc properties are improved.

• 공업화학
• /
• 제31권1호
• /
• pp.61-66
• /
• 2020

본 연구에서는 압착·코팅방식 촉매 제조 공정에 첨가제로 사용되는 콜로이드 실리카의 특성이 제조된 촉매의 성능 및 열적 안정성에 미치는 영향을 연구하였다. 이를 위해 4종의 콜로이드 실리카를 대상으로 실리카 형상 및 크기, 비표면적 및 기공특성, 성분 등을 분석하였으며 해당 콜로이드 실리카를 적용하여 제조한 V₂O₅/TiO₂ 촉매의 특성 평가 및 NOx 전환율에 대한 연구를 수행하였다. 콜로이드 실리카를 이용하여 제조한 촉매의 특성은 적용한 콜로이드 실리카의 특성에 따라 달라지며, 특히 콜로이드 실리카 내 피독물질 함량은 촉매 성능에 직접적인 영향인자인 것으로 분석되었다. 또한 콜로이드 실리카 내 실리카 함량이 높을수록 촉매의 열안정성과 성능이 향상되는 것으로 나타났다.

• Journal of Microbiology and Biotechnology
• /
• 제25권5호
• /
• pp.718-722
• /
• 2015

Techniques for immobilizing effective enzymes on nanoparticles for stabilization of the activity of free enzymes have been developing as a pharmaceutical field. In this study, we examined the effect of three different pH conditions of phosphate buffer, as a dissolving solvent for lysosomal enzymes, on the direct immobilization of lysosomal enzymes extracted from Hen's egg white and Saccharomyces cerevisiae. Titanium(IV) oxide (TiO₂) nanoparticles, which are extensively used in many research fields, were used in this study. The lysosomal enzymes immobilized on TiO₂ under each pH condition were evaluated to maintain the specific activity of lysosomal enzymes, so that we can determine the degree of melanin treatment in lysosomal enzymes immobilized on TiO₂. We found that the immobilization efficiency and melanin treatment activity in both lysosomal enzymes extracted from Hen's egg white and S. cerevisiae were the highest in an acidic condition of phosphate buffer (pH 4). However, the immobilization efficiency and melanin treatment activity were inversely proportional to the increase in pH under alkaline conditions. In addition, enhanced immobilization efficiency was shown in TiO₂ pretreated with a divalent, positively charged ion, Ca²⁺, and the melanin treatment activity of immobilized lysosomal enzymes on TiO₂ pretreated with Ca²⁺ was also increased. Therefore, this result suggests that the immobilization efficiency and melanin treatment activity of lysosomal enzymes can be enhanced according to the pH conditions of the dissolving solvent.

• 공업화학
• /
• 제7권5호
• /
• pp.992-998
• /
• 1996

Citrate process로 제조한 $La_{1-x}Ca_xCoO_3$에서 Ca이 20mole% doping된 perovskite oxide가 산소환원반응에 대해 가장 높은 전류밀도와 specific activity를 보여주었으며 cyclic voltammogram에서 carbon만으로 제조된 전극에서보다 carbon과 Perovskite oxide를 혼합한 전극에서 높은 산소흡착/탈착전류를 보였다. 입자크기분포와 소결효과에 의해 $900^{\circ}C$, 5시간 공기중에서 소결한 $La_{0.8}Ca_{0.2}CoO_3$가 산소환원반응에 대한 전기화학적 촉매특성이 우수하였다.

• Environmental Engineering Research
• /
• 제11권2호
• /
• pp.84-90
• /
• 2006

UV-catalytic oxidation technique was applied for the treatment of bio-refractory character of the leachate, which is generally present in the form of adsorbable organic halogens (AOX). Destruction of AOX was likely to be governed by pH adjustment, quantitative measurement of oxidants, and the selection of oxidation model type. Peroxide induced degradation ($UV/H_2O_2$) facilitated the chemical oxidation of organic halides in acidic medium, however, the system showed least AOX removal efficiency than the other two systems. Increased dosage of hydrogen peroxide (from 0.5 time to 1.0 time concentration) even did not contribute to a significant increase in the removal rate of AOX. In ozone induced degradation system ($UV/O_3$), alkaline medium (pH 10) favored the removal of AOX and the removal rate was found 11% higher than the rate at pH 3. Since efficiency of the $UV/O_3$ increases with the increase of pH, therefore, more OH-radicals were available for the destruction of organic halides. UV-light with the combination of both ozone and hydrogen peroxide ($UV/H_2O_2$ 0.5 time/$O_3$ 25 mg/min) showed the highest removal rate of AOX and the removal efficiency was found 26% higher than the removal efficiency of $UV/O_3$. The system $UV/H2O_2/O_3$ got the economic preference over the other two systems since lower dose of hydrogen peroxide and relatively shorter reaction time were found enough to get the highest AOX removal rate.

• 공업화학
• /
• 제28권1호
• /
• pp.64-72
• /
• 2017

본 연구에서는 다양한 증진제에 따른 $CH_4-SCR$ 반응특성을 확인하기 위하여 $Pt/Al_2O_3$를 기본으로 한 촉매에 알칼리, 알칼리 토류 금속을 담지하여 습식함침법으로 제조한다. 본 연구를 통해 $Pt/Al_2O_3$ 촉매에 Na를 담지시킬 경우 Pt와 Na 원자간 electronegative gap의 발생으로 Pt의 valence state 변화를 일으키며, 금속상 Pt의 비율이 증가됨을 확인할 수 있다. 또한 Na 첨가를 최적화시켜 제조한 촉매의 금속상 Pt종은 촉매표면에서 NO species 흡착 증진과 환원제로 사용되는 $CH_4$의 $CO_2$로의 산화를 억제시킨다. 이때, Na/Pt의 mole ratio는 4.0이 최적화이며, $CH_4-SCR$ 효율이 가장 우수하다.

• 한국재료학회지
• /
• 제23권4호
• /
• pp.227-232
• /
• 2013

Al-based alloys have recently attracted considerable interest as structural materials and light weight materials due to their excellent physical and mechanical properties. For the investigation of the potential of Al-based alloys, a surface porous $Al_{88}Cu_6Si_6$ eutectic alloy has been fabricated through a chemical leaching process. The formation and microstructure of the surface porous $Al_{88}Cu_6Si_6$ eutectic alloy have been investigated using X-ray diffraction and scanning electron microscopy. The $Al_{88}Cu_6Si_6$ eutectic alloy is composed of an ${\alpha}$-Al dendrite phase and a single eutectic phase of $Al_2Cu$ and ${\alpha}$-Al. We intended to remove only the ${\alpha}$-Al phase and then the $Al_2Cu$ phase would form a porous structure on the surface with open pores. Both acidic and alkaline aqueous chemical solutions were used with various concentrations to modify the influence on the microstructure and the overall chemical reaction was carried out for 24 hr. A homogeneous open porous structure on the surface was revealed via selective chemical leaching with a $H_2SO_4$ solution. Only the ${\alpha}$-Al phase was successfully leached while the morphology of the $Al_2Cu$ phase was maintained. The pore size was in a range of $1{\sim}5{\mu}m$ and the dealloying depth was nearly $3{\mu}m$. However, under an alkaline NaOH, aqueous solution, an inhomogeneous porous structure on the surface was formed with a 5 wt% NaOH solution and the morphology of the $Al_2Cu$ phase was not preserved. In addition, the sample that was leached by using a 7 wt% NaOH solution crumbled. Al extracted from the Al2Cu phase as ${\alpha}$-Al phase was dealloyed, and increasing concentration of NaOH strongly influenced the morphology of the $Al_2Cu$ phase and sample statement.

• Journal of Microbiology and Biotechnology
• /
• 제30권3호
• /
• pp.404-416
• /
• 2020

Bacteria that are resistant to high temperatures and alkaline environments are essential for the biological repair of damaged concrete. Alkaliphilic and halotolerant Bacillus sp. AK13 was isolated from the rhizosphere of Miscanthus sacchariflorus. Unlike other tested Bacillus species, the AK13 strain grows at pH 13 and withstands 11% (w/v) NaCl. Growth of the AK13 strain at elevated pH without urea promoted calcium carbonate (CaCO₃) formation. Irregular vaterite-like CaCO₃ minerals that were tightly attached to cells were observed using field-emission scanning electron microscopy. Energy-dispersive X-ray spectrometry, confocal laser scanning microscopy, and X-ray diffraction analyses confirmed the presence of CaCO₃ around the cell. Isotope ration mass spectrometry analysis confirmed that the majority of CO₃^2- ions in the CaCO₃ were produced by cellular respiration rather than being derived from atmospheric carbon dioxide. The minerals produced from calcium acetate-added growth medium formed smaller crystals than those formed in calcium lactate-added medium. Strain AK13 appears to heal cracks on mortar specimens when applied as a pelletized spore powder. Alkaliphilic Bacillus sp. AK13 is a promising candidate for self-healing agents in concrete.

• 공업화학
• /
• 제7권3호
• /
• pp.554-564
• /
• 1996

페롭스카이트 $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$(x=0.00, 0.01, 0.10, 0.20, 0.35, 및 0.50)를 산소전극물질로 사용하여 알칼리형 연료전지에서의 산소환원반응을 연구하였다. Fe치환에 따른 촉매특성의 변화를 X-선회절분석법(XRD), 열중량분석법(TG) 및 승온환원법(TPR)을 통하여 조사하였다. XRD 구조분석을 통하여 페롭스카이트 단위격자의 격자상수값을 측정할 수 있었다. TG 실험결과 Fe는 페롭스카이트 구조내에서 크게 안정화되어 $900^{\circ}C$까지 거의 환원되지 않았고, Fe치환량 증가에 따라 Co-O간의 결합에너지가 증가하여 고온에서 제거되는 산소종의 양이 증가하였다. TPR 실험결과, ${\alpha}$-(저온피크)와 ${\beta}$-(고온피크)산소종이 존재하였다. ${\beta}$-산소종은 Co와 강하게 결합되어 있는 산소종으로서 Fe치환량 증가에 따라 결합세기가 증가하였다. ${\alpha}$-산소종은 가역적으로 격자내외를 출입하는 산소환원반응의 활성종이었으며, Fe치환량 증가에 따른 격자상수의 증가는 금속과 ${\alpha}$-산소종간의 결합에너지로 볼 수 있는 ${\alpha}$산소종의 환원피크를 저온으로 이동시킴으로써 산소환원반응의 활성을 증가시켰다. 반면에, Fe치환량 증가에 따른 ${\alpha}$-산소종의 감소는 산소환원반응의 활성을 감소시켰으며, Fe치환에 따른 표면적의 증가는 반응활성에 크게 영향을 미치지 못하였다.