• Korean Chemical Engineering Research
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• 제54권6호
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• pp.854-862
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• 2016

최근 화석연료를 대체할 친환경 신재생에너지에 대한 요구가 증가하면서 수소에너지가 미래 대체에너지원으로서 주목받고 있다. 수소를 생산하는 방법 중 수전해 기술은 에너지효율과 안정성이 뛰어난 장점이 있지만, 산소발생반응시 발생하는 높은 과전압은 여전히 단점으로 지적되고 있다. 본 연구에서는 분무열분해 공정을 통하여 Co 전구체로부터 $Co_3O_4$를 제조하였다. 또한, urea, sucrose, citric acid의 유기물첨가제를 사용하여 다양한 입자 크기와 표면형상을 가지는 $Co_3O_4$를 제조하였고, 필요에 따라 추가로 열처리를 실시하였다. 합성한 $Co_3O_4$의 물리적 특성을 분석하기 위해 X-선 회절 분석(XRD)으로 결정성을 조사하였고, 주사전자현미경(SEM)과 투과전자현미경(TEM)으로 입자형상 및 표면을 분석하였다. 질소 흡 탈착 시험을 통해 촉매의 비표면적 및 기공부피를 측정하였고, 질소도핑을 확인하기 위해 X-선 광전자 분광법(XPS)을 사용하였다. 촉매의 산소발생반응 활성을 알아보기 위해 3전극 셀에서 선형주사전위법(LSV)으로 전기화학적 거동을 분석하였다. 첨가제를 사용하지 않은 $Co_3O_4$가 가장 우수한 활성을 보였고, 이는 분무열분해법을 통하여 상대적으로 작은 입자형성과 높은 비표면적의 영향인 것으로 판단된다.

• Asian-Australasian Journal of Animal Sciences
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• 제24권2호
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• pp.285-294
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• 2011

The abatement of methane emission from ruminants is an important global issue due to its contribution to greenhouse gas with carbon dioxide. Methane is generated in the rumen by methanogens (archaea) that utilize metabolic hydrogen ($H_2$) to reduce carbon dioxide, and is a significant electron sink in the rumen ecosystem. Therefore, the competition for hydrogen used for methanogenesis with alternative reductions of rumen microbes should be an effective option to reduce rumen methanogenesis. Some methanogens parasitically survive on the surface of ciliate protozoa, so that defaunation or decrease in protozoa number might contribute to abate methanogenesis. The most important issue for mitigation of rumen methanogenesis with manipulators is to secure safety for animals and their products and the environment. In this respect, prophylactic effects of probiotics, prebiotics and miscellaneous compounds to mitigate rumen methanogenesis have been developed instead of antibiotics, ionophores such as monensin, and lasalocid in Japan. Nitrate suppresses rumen methanogenesis by its reducing reaction in the rumen. However, excess intake of nitrate causes intoxication due to nitrite accumulation, which induces methemoglobinemia. The nitrite accumulation is attributed to a relatively higher rate of nitrate reduction to nitrite than nitrite to ammonia via nitroxyl and hydroxylamine. The in vitro and in vivo trials have been conducted to clarify the prophylactic effects of L-cysteine, some strains of lactic acid bacteria and yeast and/or ${\beta}$1-4 galactooligosaccharide on nitrate-nitrite intoxication and methanogenesis. The administration of nitrate with ${\beta}$1-4 galacto-oligosaccharide, Candida kefyr, and Lactococcus lactis subsp. lactis were suggested to possibly control rumen methanogenesis and prevent nitrite formation in the rumen. For prebiotics, nisin which is a bacteriocin produced by Lactococcus lactis subsp. lactis has been demonstrated to abate rumen methanogenesis in the same manner as monensin. A protein resistant anti-microbe (PRA) has been isolated from Lactobacillus plantarum as a manipulator to mitigate rumen methanogenesis. Recently, hydrogen peroxide was identified as a part of the manipulating effect of PRA on rumen methanogenesis. The suppressing effects of secondary metabolites from plants such as saponin and tannin on rumen methanogenesis have been examined. Especially, yucca schidigera extract, sarsaponin (steroidal glycosides), can suppress rumen methanogenesis thereby improving protein utilization efficiency. The cashew nutshell liquid (CNSL), or cashew shell oil, which is a natural resin found in the honeycomb structure of the cashew nutshell has been found to mitigate rumen methanogenesis. In an attempt to seek manipulators in the section on methane belching from ruminants, the arrangement of an inventory of mitigation technologies available for the Clean Development Mechanism (CDM) and Joint Implementation (JI) in the Kyoto mechanism has been advancing to target ruminant livestock in Asian and Pacific regions.

• KSBB Journal
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• 제25권6호
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• pp.520-526
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• 2010

토양 미생물로부터 스크리닝한 미생물 중 카탈라제 생산량이 높은 세 가지 미생물 (Bacillaceae bacterium BKBChE-1, Bacillus sp. BKBChE-2와 Bacillus flexus BKBChE-3)을 배양하여 얻은 카탈라제 효소가 과산화수소를 분해하는 것을 확인하고, 미생물 균체를 천연제올라이트에 정전기적 흡착법으로 고정하였다. 주사전자 현미경을 통해 각각의 미생물이 지지체에 잘 흡착된 것이 관찰되었고, 10.5 mM의 과산화수소를 1시간 이내에 완전히 분해되는 것을 확인하였다. 과산화수소 분해 속도가 가장 빠른 Bacillus flexus BKBChE-3은 온도와 pH 영향성 실험을 통해 고온과 pH 10 이상의 강알칼리 조건에서도 30일 이후까지 미생물이 생존하는 것을 관찰하였다. 또한 고정화된 미생물의 경우 온도 $25-40^{\circ}C$, pH 7-10의 조건에서 생균수가 계속하여 증가하는 것을 확인하였다. 본 실험을 통해 Bacillus flexus BKBChE-3이 생산한 카탈라제 효소 뿐만 아니라 고정화된 균체도 과산화수소의 제거에 효과적임을 확인할 수 있었다. 이들 결과로부터 미생물 발효를 통해 생산된 효소의 생산량 증가와 미생물 개체 수 증가를 이용하여 산업폐수에 적용하면, 과산화수소의 제거 효율을 높이고 균체 재활용을 통한 공정비용을 절감할 수 있을 것으로 사료된다.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.148-158
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• 2022

The electrochemical CO₂ reduction (ECR) to produce value-added fuels and chemicals using clean energy sources (like solar and wind) is a promising technology to neutralize the carbon cycle and reproduce the fuels. Presently, the ECR has been the most attractive route to produce carbon-building blocks that have growing global production and high market demand. The electrochemical CO₂ reduction could be extensively implemented if it produces valuable products at those costs which are financially competitive with the present market prices. Herein, the electrochemical conversion of CO₂ obtained from flue gases of a power plant to produce diesel and formic acid using a consistent techno-economic approach is presented. The first scenario analyzed the production of diesel fuel which was formed through Fischer-Tropsch processing of CO (obtained through electroreduction of CO₂) and hydrogen, while in the second scenario, direct electrochemical CO₂ reduction to formic acid was considered. As per the base case assumptions extracted from the previous outstanding research studies, both processes weren't competitive with the existing fuel prices, indicating that high electrochemical (EC) cell capital cost was the main limiting component. The diesel fuel production was predicted as the best route for the cost-effective production of fuels under conceivable optimistic case assumptions, and the formic acid was found to be costly in terms of stored energy contents and has a facile production mechanism at those costs which are financially competitive with its bulk market price. In both processes, the liquid product cost was greatly affected by the parameters affecting the EC cell capital expenses, such as cost concerning the electrode area, faradaic efficiency, and current density.

• 대한환경공학회지
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• 제22권2호
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• pp.291-302
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• 2000

연료가스로부터 황화수소를 제거하기 위해 망간계 탈황제를 개발하여, 대기압하 고정층반응기에서 황화/재생 반복실험을 통하여 탈황제의 효용성, breakthrough times, 그리고 평형농도를 구하였다. 황화수소 제거능에 영향을 미치는 입자크기, 황화반응 온도, 재생온도 그리고 재생 특성에 관해 살펴보았다. 황화수소 제거를 위한 적정 조업온도는 $800^{\circ}C$였으며 입자크기가 감소할수록 탈황능은 증가하였으나 입경 0.214~0.631mm에서는 큰 차이를 보이지 않았다. 실험으로부터 구한 황화수소 평형관계식은 log(K)=3.396/T-1.1105이고 탈황제 이용효율은 $800^{\circ}C$에서 92%를 나타냈다. 공기를 사용해서 재생할 때 $SO_2$ 배출농도는 $800^{\circ}C$에서 8.5% 이상, $850^{\circ}C$에서 8.4% 이상, 그리고 $900^{\circ}C$에서 8.8% 이상을 보여 황산제조에 사용될 수 있을 것으로 판단된다.

• 대한기계학회논문집B
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• 제35권4호
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• pp.391-397
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• 2011

수소가 매력적인 연료로 각광받기 시작하면서 수요가 급증하였으며 이에 대응하여 수소 생산 기술에 대한 연구가 필요하다. 본 연구에서는 산소-메탄올 비율에 따른 연료전지용 메탄올 개질기의 반응 효율을 알아보았다. 각각의 촉매 배열에 따른 산소-메탄올의 비율($O_2/CH_3OH$)의 영향을 알아보기 위해 $O_2/CH_3OH$를 0.1에서 0.4까지 0.05씩 증가시켜 반응기의 온도, 변환율, 효율에 관한 실험을 수행하였다. $O_2/CH_3OH$가 0.15에서 0.2로 증가할 때 촉매층(catalyst bed)의 온도도 증가하며, 흡열 반응이 발열반응으로 변하여 반응기의 온도를 상승시켜 촉매 점화에 따라 온도는 $235^{\circ}C$정도 급상승한 $500^{\circ}C$가 된다. 반응기의 성능은 $O_2/CH_3OH$에 크게 의존하며 이론적 연구에서 $O_2/CH_3OH$는 0.23이었으나 실험 결과는 30 % 높은 0.30일 때 최적의 성능을 나타내었다. 이것은 혼합기체의 농도차이, 반응속도, 촉매, 반응기의 열손실, 반응 시 생성된 생성물 등의 변화 때문인 것으로 여겨진다.

• Asian-Australasian Journal of Animal Sciences
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• 제22권10호
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• pp.1366-1376
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• 2009

Effect of sulfur (S) on utilization efficiency of fresh cassava foliage and cassava hay in dairy cows was evaluated using thirty-two $1^{st}-2^{nd}$ lactation Holstein-Friesian crossbred dairy cows. The experimental treatment was a 2${\times}$2 factorial arrangement in a randomized complete block design (RCBD) using two roughages (rice straw+fresh cassava foliage (FCF) and rice straw+cassava hay (CH)) and two elemental sulfur (S) levels (0.15 and 0.4% S of dry matter (DM)), respectively. Four dietary treatments (FCF+0.15, FCF+0.4, CH+0.15 and CH+0.4) were offered ad libitum in the form of a total mixed ration (TMR) with concentrate to roughage (chopped rice straw+chopped cassava foliage) ratio at 60:40. Fresh cassava foliage or cassava hay resulted in similar dry mater intake, rumen ecology parameters, total tract digestibility, blood chemistry, milk production and composition. However, HCN intake, blood and milk thiocyanate concentration were significantly higher (p<0.01) in cows fed fresh cassava foliage with no sign of potential toxicity. Dry matter intake, body weight changes, molar percentage of propionate in rumen, neutral detergent fiber (NDF) digestibility and nitrogen (N) retention of cows tended to be increased while DM digestibility (65.6, 72.7, 68.6 and 72.1% of total DM intake for the respective treatments), rumen bacteria population (1.4, 1.7, 1.6 and $1.7{\times}10^{11}$ cell/ml for respective treatments), fungal zoospore population (0.4, 0.6, 0.4 and $0.5{\times}10^{6}$ cell/ml for respective treatments), urinary allantoin (25.3, 28.0, 26.3 and 27.6 g/d for respective treatments), microbial N yield (136.0, 154.6, 142.8 and 151.3 g N/d for respective treatments) and milk protein content (3.4, 3.5, 3.2 and 3.5% for respective treatments) were significantly (p<0.05) higher in cows fed on supplemented sulfur at 0.4% of DM in comparison with 0.15% S-supplemented diets. Based on these results, it is concluded that cassava foliage could be used as a portion of roughage for dairy cows and supplementation of S would be nutritionally beneficial.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.59-75
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• 2016

Reduced or black $TiO_{2-x}$ materials with oxygen-deficiency have been achieved by creating oxygen vacancies and/or defects at the surface using different methods. Fascinatingly, they exhibited an extended absorption in VIS and IR instead of only UV light with bandgap decrease from 3.2 (anatase) to ~1 eV. However, despite the dramatic enhancement of optical absorption in black $TiO_{2-x}$ materials, they have failed to show expected visible light-assisted water splitting efficiency. This was ascribed to the high concentration of the surface defects and/or oxygen vacancies, considered as an electron donor to enhance donor density and improve the charge transportation in black $TiO_2$ can also act as charge recombination centers, which eventually decrease photocatalytic activity. Therefore, a black ot reducd $TiO_2$ material with optimized properties would be highly desired for visible light photocatalysis. In this report, a new controlled magnesiothermic reduction has been developed to synthesize reduced black $TiO_{2-x}$ in the presence $H_2/Ar$ for photocatalytic $H_2$ production from methanol-water system. The material possesses an optimum band gap and band position, oxygen vacancies, and surface defects and shows significantly improved optical absorption in the visible and infrared region. The synergistic effects enable the reduced $TiO_{2-x}$ material to show an excellent hydrogen production ability along with long-term stability under the full solar wavelength range of light and visible light, respectively, in the methanol-water system in the presence of Pt as a co-catalyst. These values are superior to those of previously reported black $TiO_2$ materials. On the basis of all the results, it can be realized that the outstanding activity and stability of the reduced of $TiO_{2-x}$ NPs suggest that a balanced combination of different factors like $Ti^{3+}$, surface defects, oxygen vacancy, and recombination center is achieved along with optimized bandgap and band position during the preparation employing magnesiothermic reduction in the presence of $H_2$. The controlled magnesiothermic reduction in the presence of $H_2$ is one of the best alternative ways to produce active and stable $TiO_2-based$ photocatalyst for $H_2$ production.

• 한국축산시설환경학회지
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• 제11권2호
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• pp.97-102
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• 2005

Anaerobic decomposition is one of the most common processes in nature and has been extensively used in waste and wastewater treatment for several centuries. New applications and system modifications continue to be adapted making the process either more effective, less expensive, or suited to the particular waste in question and the operation to which it is to be applied. Animal manure is a highly biodegradable organic material and will naturally undergo anaerobic fermentation, resulting in release of noxious odors, such as in manure storage pits. Depending on the presence or absence of oxygen in the manure, biological treatment process may be either aerobic or anaerobic. Under anaerobic conditions, bacteria carry on fermentative metabolisms to break down the complex organic substances into simpler organic acids and then convert them to ultimately formed methane and carbon dioxide. Anaerobic biological systems for animal manure treatment include anaerobic lagoons and anaerobic digesters. Methane and carbon dioxide are the principal end products of controlled anaerobic digestion. These two gases are collectively called biogas. The biogas contains $60\~70\%$ methane and can be used directly as a fuel for heating or electrical power generation. Trace amounts of ammonia and hydrogen sulfide ($100\~300\;ppm$) are always present in the biogas stream. Anaerobic lagoons have found widespread application in the treatment of animal manure because of their low initial costs, ease of operation and convenience of loading by gravity flow from the animal buildings. The main disadvantage is the release of odors from the open surfaces of the lagoons, especially during the spring warm-up or if the lagoons are overloaded. However, if the lagoons are covered and gases are collected, the odor problems can be solved and the methane collected can be used as a fuel. Anaerobic digesters are air-tight, enclosed vessels and are used to digest manure in a well-controlled environment, thus resulting in higher digestion rates and smaller space requirements than anaerobic lagoons. Anaerobic digesters are usually heated and mixed to maximize treatment efficiency and biogas production. The objective of this work was to review a current anaerobic biological treatment of animal manure for effective new technologies in the future.

• 멤브레인
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• 제26권6호
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• pp.458-462
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• 2016

염수전기분해(saline water electrolysis) 또는 클로로-알칼리 막공정(chlor-alkali membrane process)은 양이온교환막과 전극으로 구성되는 전해셀에 전기를 가하여, 고순도(> 99%)의 고부가가치 화합물(예 : 염소, 수소, 수산화나트륨)을 직접 제조하는 화학공정이다. 염수전기분해의 경제성은 동일한 양의 화합물을 생산하기 위해 투여되는 에너지 소비량을 저감시킴으로 달성될 수 있다. 이러한 이슈는 전해질이나 전극의 고유 저항을 줄이거나, 전해질과 전극 사이의 계면 저항을 감소시킴으로 달성시킬 수 있다. 본 연구에서는 전자빔 동시조사법을 사용하여, 높은 화학적 안정성을 지닌 탄화수소계 술폰산 이오노머 막의 표면에 높은 이온선택성을 갖는 고분자를 접목 시키는 시도가 이루어졌다. 이를 통해, 고분자 전해질 막의 이온전도성을 보완함과 동시에, 전극과의 계면 저항을 감소시켜, 전기화학적 효율 향상이 이루어짐을 관찰하였다.