• 자원리싸이클링
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• 제30권1호
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• pp.44-52
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• 2021

본 연구에서는 알칼리성 침전제 종류 따라 제조되는 수산화리튬 결정화 정도 확인을 위해 폐리튬이차전지로부터 회수된 황산리튬을 원료로 사용하여 수산화리튬 제조 거동을 확인하였다. 황산리튬의 리튬염 전구체에 포함되어 있는 불순물 제거 및 높은 수산화리튬 합성효율을 위해 2차 침전법인 Double replacement reaction(DRR) 공정을 사용하였으며, 결정성 높은 수산화리튬 제조를 위하여 알칼리성 침전제(KOH, Ca(OH)2, Ba(OH)2)를 포함하여 전구체 몰비 ([Li]/[OH]) 및 합성온도 조건을 변수로 두어 실험을 진행하였다. 반응 후 생성된 불순물 제거를 위해 2차 고/액 분리를 실시하였고 불순물이 제거된 수산화리튬 수용액은 증발을 통해 수분 제거하여 분말을 수득하였다. 최종적으로 수득한 분말의 결정성 평가 및 제조 거동을 확인하였다.

• Journal of Korean Dental Science
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• 제2권1호
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• pp.11-18
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• 2009

The purpose of this study was to investigate the possibility to reduce the toxicity of oil based root canal sealers containing calcium hydroxide using MTT & agar overlay assays. Thus some formulations of traditional root canal sealers were replaced with oil-soluble solvents and experimental root canal sealers manufactured. In MTT assay, Cell viability of all experimental sealers in addition with oil soluble solvents were observed significantly higher than both control groups, especially according to replace zinc and/or calcium ion components. Also agar overlay assay was appeared moderate to no cell responses into modifying both zinc and/or calcium ion components and oil soluble solvent weight. Authors found the reducing effect of cell toxicity through significant role of oil soluble solvent factor into root canal sealer containing calcium hydroxide.

• 한국세라믹학회지
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• 제26권5호
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• pp.637-644
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• 1989

Beta-sialon powder(Z=1) was synthesized by the simultaeous reduction and nitridation of the mixed powders of Hadong kaolin and silica. Silicon hydroxide was prepared from Si-alkoxide by a hydrolysis method and amorphous silica was obtained from the calcination of the prepared silicon hydroxide. Hadong kaolin was mixed with both the silicon hydroxide and amorphous silica, respectively. The average particle size was 4${\mu}{\textrm}{m}$ and the morphology of particle was rod-like and equiaxed in the case of beta-sialon powder prepared form Hadong kaolin and silicon hydroxide(COMPOSITION A), whereas the average particle size was 3${\mu}{\textrm}{m}$ and the morphology of particle was equiaxed in the case of beta-sialon powder prepared from Hadong kaolin and amorphous silica(COMPOSITION B). The synthesized beta-sialon powders were hot-pressed at 175$0^{\circ}C$ for 2 hours under 30 MPa in a nitrogen atmosphere after YAG composition(8wt%) was added to these powders as a sintering agent. The hot-pressed specimens were annealed a 140$0^{\circ}C$ for 4 hours in a nitrogen atmosphere. The mechanical properties of sintered bodies were investigated in terms of M.O.R., fracture toughness and hardness. The measured values are as follows. COMPOSITION A : M.O.R. 508MPa, KIC 3.5MN/m3/2, hardness 13.6GPa. COMPOSITION B : M.O.R. 653MPa, KIC 5.4MN/m3/2, hardness 13.5GPa.

• 한국가구학회지
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• 제27권4호
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• pp.392-398
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• 2016

Wood-plastic composites (WPCs) composed of mainly wood flour and thermoplastics have attracted considerable attentions due to advantages of cost effectiveness, high durability, and microbial resistance. However, relatively poor fire resistance of WPCs from low thermal stability of wood and plastics prevents further uses. This study investigated the effect of expandable graphite (EG) and aluminium hydroxide (AH)/magnesium hydroxide (MH) on the properties of WPCs. The combined incorporation of both EG and metal hydroxide (i.e., AH or MH) into formulations leads to higher flexural modulus of filled composites compared to neat PP and WPC. In thermal properties, EG played an important role in improving thermal stability of filled composites by suppressing thermal decompositions of wood and PP. Moreover, EG showed better water absorption features. From this research, it can be said that EG and metal hydroxides have potentials as effective reinforcement, flame retardant, and moisture barrier.

• Journal of Microbiology and Biotechnology
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• 제25권12호
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• pp.2016-2023
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• 2015

Xylanase plays important roles in a broad range of industrial production as a biocatalyst, and its applications commonly require immobilization on supports to enhance its stability. Aluminum hydroxide, a carrier material with high surface area, has the advantages of simple and low-cost preparation and resistance to biodegradation, and can be potentially used as a proper support for xylanase immobilization. In this work, xylanase from Thermomyces lanuginosus was immobilized on two types of aluminum hydroxide particles (gibbsite and amorphous Al(OH)₃) through adsorption, and the properties of the adsorbed enzymes were studied. Both particles had considerable adsorptive capacity and affinity for xylanase. Xylanase retained 75% and 64% of the original catalytic activities after adsorption to gibbsite and amorphous Al(OH)₃. Both the adsorptions improved pH and thermal stability, lowered activation energy, and extended lifespan of the immobilized enzyme, as compared with the free enzyme. Xylanase adsorbed on gibbsite and amorphous Al(OH)₃ retained 71% and 64% of its initial activity, respectively, after being recycled five times. These results indicated that aluminum hydroxides served as good supports for xylanase immobilization. Therefore, the adsorption of xylanase on aluminum hydroxide particles has promising potential for practical production.

• Environmental Engineering Research
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• 제21권3호
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• pp.297-303
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• 2016

Global warming due to greenhouse gases is an issue of great concern today. Fossil fuel power plants, especially coal-fired thermal power plants, are a major source of carbon dioxide emission. In this work, carbon capture and utilization using sodium hydroxide was studied experimentally. Application for flue gas of a coal-fired power plant is considered. Carbon dioxide, reacting with an aqueous solution of sodium hydroxide, could be converted to sodium bicarbonate ($NaHCO_3$). A bench-scale unit of a reactor system was designed for this experiment. The capture scale of the reactor system was 2 kg of carbon dioxide per day. The detailed operational condition could be determined. The purity of produced sodium bicarbonate was above 97% and the absorption rate of $CO_2$ was above 95% through the experiment using this reactor system. The results obtained in this experiment contain useful information for the construction and operation of a commercial-scale plant. Through this experiment, the possibility of carbon capture for coal power plants using sodium hydroxide could be confirmed.

• Environmental Engineering Research
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• 제12권3호
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• pp.101-108
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• 2007

Fixation of lead contaminants in the solidification/stabilization using Portland cement has been investigated by X-ray diffraction, scanning electron microscopy and compressive strength. The presence of lead was observed to produce lead carbonate sulfate hydroxide ($Pb_4SO_4(CO_3)_2(OH)_2$), lead carbonate hydroxide hydrate ($3PbCO_3{\cdot}2Pb(OH)_2{\cdot}H_2O$) and two other unidentified lead salts in cavity areas and was observed to significantly retard the hydration of cement. By 28 days, howevere, the XRD peaks of most of the lead precipitates have essentially disappeared with only residual traces of lead carbonate sulfate hydroxide and lead carbonate hydroxide hydrate evident. After 28 days of curing, hydration appears well advanced with a strong portlandite peak present though C-S-H gel peaks are not particularly evident. Lead species produced with the dissolution of lead precipitates are fixed into the cement matrix to be calcium lead silicate hydrate (C-Pb-S-H) during cement-based solidification.

• 식물병연구
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• 제10권1호
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• pp.82-85
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• 2004

Erwinia carotovora subsp. carotovora에 의한 배추 무름병은 배추에서 가장 큰 문제가 되고 있는 병 중 하나이다. 본 연구는 칼슘비료 시비가 배추 무름병 발생에 미치는 영향을 조사하기 위하여 실시하였다 칼슘 비료 7종을 선발하여 배추 유묘에 엽면 살포한 후, 세균현탁액과 mineral oil을 4:1로 혼합하여 배추의 중앙 기부에 10 m1 관주 접종하는 mineral oil 접종법으로 접종하였다. 배추 유묘에 엽면 살포한 결과 calcium hydroxide가 다른 calcium 비료보다 무름병 방제에 효과가 높게 나타났다. 질소 비료시비는 무름병 발생을 촉진한 반면, calcium hydroxide를 수용액으로 엽면시비할 때 유묘에서뿐 아니라 포장 시험에서도 무름병 발생을 억제하였다. Calcium과 질소를 혼합 살포할 때도 calcium 단독살포와 마찬가지로 무름병 발생을 억제하였다.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제10권S_2호
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• pp.89-95
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• 2001

The solidification and leaching characteristics of cyclone ash collected from an industrial incineration plant were investigated. Cement and calcium hydroxide were used as the solidifying materials. The leaching characteristics of the solidified cyclone ash were found to vary depending on both the quantitative and the qualitative aspects of the solidifying materials. Except for copper and lead, all the heavy metal ions in the leachate of the solidified material composed of 10~20 % cement or 10~20 % calcium hydroxide were found to be within their standard limit. Moreover, all the heavy metal ions were also observed to be within satisfactory limits in the leachate obtained from the solidified material composed of 30 % cement or 30 % calcium hydroxide. Therefore, to satisfy the standard compressive intensity and permissible limits of heavy metal ions leached from solidified material, it would appear that a 30 % proportion of either additive in the solidification product can meet the required standard for the leachate. The cost of solidifying cyclone ash per ton for ash-30 % cement and ash-30 % lime was calculated as 26,750 and 26,070 won, respectively. Accordingly, significant reduction in the waste toxicity and mobility as well as an improvement in the engineering properties of the solidified products were successfully achieved.

• 대한화학회지
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• 제18권6호
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• pp.430-436
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• 1974

여러 pH에서 1,1-dicyano-2-p-dimethylaminophenyl-2-chloroethylene(DPC)의 가수분해 속도상수를 측정하고 넓은 pH 범위에서 잘 맞는 반응 속도로식을 구하였다. 이 식에 의하면 넓은 pH 범위에서 DPC에 대한 가수분해 반응메카니즘을 잘 설명할 수 있다. pH3이하와 7.5이상에서는 속도상수는 hydronium ion과 hydroxide ion 농도에 각각 비례한다. 또 pH 3∼7.5 사이에서는 물, hydronium ion 과 hydroxide ion이 DPC의 가수 분해에 촉매 역활을 함을 알았다.