• Clean Technology
• /
• v.20 no.2
• /
• pp.103-107
• /
• 2014

Acrylic acid is a commodity chemical which is applicable for various industries such as polymer and textile industry. Currently, it has been produced by chemical synthesis from petroleum. However, due to the high price of petroleum and global $CO_2$ emission, renewable materials such as sugar are interesting alternative carbon sources for the biological production of acrylic acid. For an economic production of acrylic acid from renewable carbon sources, a cost effective separation process for acrylic acid should be needed. In this study, reactive extraction by TOA (tri-n-octylamine) was used for the recovery of acrylic acid from its aqueous solutions. The effects of polarity of diluents and concentration of TOA on extraction equilibrium were investigated. The extraction efficiency was proportional to concentration of TOA and polarity of diluents and its value was more than 95% in the case of sufficient concentration of TOA. From IR spectroscopy, it was concluded that the ratio of (1,1) acid-amine complex was increased and the ratio of acid dimer was decreased with concentration of TOA. Equilibrium model based on IR spectroscopy was well fitted with experimental data.

• Membrane Journal
• /
• v.27 no.6
• /
• pp.487-498
• /
• 2017

In this study, pervaporation performances of water/methanol and water/butanol mixture were evaluated using zeolite 4A membranes manufacutred by FINETECH by experimental works and numerical modeling. Permeation and separation characteristics, such as flux and separation factor, were analyzed by gas chromatography (TCD) and liquid nitrogen traps. Experiments have shown that water is selectively separated from a mixture of water and methanol (separation factor up to approximately 250) and water and butanol (separation factor up to approximately 1,500). Generalized Maxwell Stefan (GMS) theory was implemented to predict pervaporation behaviors of water/alcohol mixtures and diffusional coefficients of zeolite layer were obtained through parameter estimation using $MATLAB^{(R)}$ optimization toolbox. Since the pore size of zeolite 4A are much larger than kinetic diameter of water molecules and smaller than those of methanol and butanol, zeolite 4A membranes can be applied to in situ water removal process such as membrane reactors or hybrid reaction-dehydration process.

• Korean Chemical Engineering Research
• /
• v.54 no.2
• /
• pp.248-254
• /
• 2016

Efficacious wastewater treatment is essential for increasing sewage sludge volume and implementing strict environmental regulations. The operation cost of sludge treatment amounts up to 50% of the total costs for wastewater treatment plants, therefore, an economical sludge destruction method is crucially needed. Amid several destruction methods, wet air oxidation (WAO) can efficiently treat wastewater containing organic pollutants. It can be used not only for sludge destruction but also for useful by-product production. Volatile fatty acids (VFAs), one of many byproducts, is considered to be an important precursor of biofuel and chemical materials. Its high reaction condition has instituted the study of gravity pressure reactor (GPR) for an economical process of WAO to reduce operation cost. Simulation of subcritical condition was conducted using Aspen Plus with predictive Soave-Redlich-Kwong (PSRK) equation of state. Conjointly, simulation analysis for GPR depth, oxidizer type, sludge flow rate and oxidizer injection position was carried out. At GPR depth of 1000m and flow rate of 2 ton/h, the conversion and yield of VFAs were 92.02% and 0.17g/g, respectively.

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.3
• /
• pp.155-161
• /
• 2012

A simple in-situ methane enrichment system in mesophilic anaerobic digestion was developed to take advantage of the differing solubilities of $CO_2$ and methane. The methane enhancement systems consisted of low solids plug-flow maize digester coupled with a leachate recycle loop to an external $CO_2$ stripper. The effects of leachate recycle rate (LRR) and reactor alkalinity on the resulting offgas $CH_4$ contents, biogas productivity and TVS removal efficiency were quantitively evaluated. The results showed that offgas $CH_4$ contents of over 94% was achieved at 3 volume of leachate recycle per volume of reactor per day (3 v/v-d) and at the reactor alkalinity of 4 g/L as $CaCO_3$, as the optimum operating conditions. The TVS removal efficiency of the methane enhancement system was 79% which corresponds to 94% of the control reactor and the methane productivity appeared to be 0.71 v/v-d. Offgas methane contents correlated well with LRR. However excessively high LRR led to the decrease in TVS removal efficiency.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.250-250
• /
• 2013

단일벽 탄소나노튜브(Single-walled nanotubes, SWNTs)는 나노스케일의 크기와 우수한 물성으로 인하여, 전자, 에너지, 바이오 분야로의 응용이 기대되고 있다. 특히 SWNTs의 직경을 제어하게 되면 튜브의 전도성 제어가 훨씬 수월하게 되어, 차세대 나노전자소자의 실현을 앞당길 수 있으며 이러한 이유로 많은 연구들이 현재 행해지고 있다. SWNTs의 직경제어 합성을 위해서는 현재 열화학기상증착법(Thermal chemical vapor deposition; TCVD)이 가장 일반적으로 이용되고 있으며, 합성 촉매와 합성되는 튜브의 직경과의 크기 연관성이 알려진 후로는, 촉매의 크기를 제어하여 SWNTs의 직경을 제어하고자 하는 연구들이 활발하게 보고되고 있다. 특히, 촉매 나노입자의 직경이 1~2 nm 이하로 감소될 경우, SWNTs의 직경 분포가 어떻게 변화할 것인지가 최근 가장 중요한 관심사로 남아 있으나, 이러한 크기의 금속입자는 나노입자의 융점저하 현상이 발현되는 영역이므로, SWNTs의 합성온도 영역에서 촉매 금속입자는 반액체(Semi-liquid) 상태로 존재할 것으로 추측하고 있다. 본 연구에서는 고온의 SWNTs 합성환경에서 금속나노촉매의 유동성을 제한하기 위하여 나노사이즈의 기공이 규칙적으로 정렬된 다공성 물질인 제올라이트를 촉매담지체로 이용하였고, 이 때 다양한 합성변수가 SWNTs의 직경에 미치는 영향을 살펴보고자 하였다. SWNTs의 합성을 위해 실리콘 산화막 기판 위에 제올라이트를 도포한 후, 합성 촉매로서 전자빔증발법을 통하여 수 ${\AA}$에서 수 nm 두께의 철 박막을 증착하였다. 합성은 메탄을 원료가스로 하여 TCVD법으로 실시하였다. 주요변수로는 제올라이트 종류, 증착하는 철 박막의 두께, 합성온도를 설정하였으며, 이에 따라 합성된 SWNTs의 합성수율 및 직경분포의 변화를 체계적으로 살펴보았다. SWNTs의 전체적인 합성수율의 변화는 SEM 관찰결과를 이용하였으며, SWNTs의 직경은 AFM 관찰 및 Raman 스펙트럼의 분석에서 도출하였다. 실험결과, 제올라이트 종류에 따라서는 명확한 튜브직경 분포의 변화 없이 비교적 좁은 직경분포를 갖는 SWNTs가 합성되었으며, 합성온도가 $850^{\circ}C$ 이하로 감소되면 합성수율이 현저히 감소되는 것을 알 수 있었다. 촉매박막의 두께가 1 nm 이상인 경우에서는 직경 5 nm 전후의 나노입자가 형성되었으며, 이때 SWNTs의 합성수율은 높았으나 다양한 직경의 튜브가 합성이 된 것을 확인할 수 있었다. 반면, 촉매입자의 크기가 2 nm 이하에서는 합성수율은 다소 저하되었으나, SWNTs의 직경분포의 폭이 상대적으로 훨씬 좁아지는 것을 알 수 있었다. 추후, 극미세 촉매와 저온합성 환경에서의 합성수율 향상을 위한 합성공정의 개량이 지속적으로 요구된다.

• Korean Journal of Food Science and Technology
• /
• v.51 no.1
• /
• pp.42-47
• /
• 2019

The purpose of this study was to compare the amygdalin content, alcohol content, pH, titratable acidity, and color of maesil wine prepared with two different manufacturing processes. Maesil wine was made from maesil chung, and maesil was preserved (MW1) or removed (MW2) before fermentation. During aging, amygdalin content in all the wines was gradually reduced, and the content of MW2 was less than that of the other. The alcohol content, pH, and titratable acidity ranged from around 9.87-10.94, 3.57-3.80, and 8.89-10.68%, respectively. The difference between the samples was not significant. For color, MW1 had lower L and higher a and b values than MW2. In this study, the difference in physicochemical properties according to the presence of maesil was not significant, indicating no degradation of the quality according to the manufacturing processes. However, the MW2 showed a reduction in amygdalin contents.

• Food Science and Industry
• /
• v.52 no.2
• /
• pp.153-170
• /
• 2019

With the breathtaking stride beingmade in the field of biotechnology, biocatalyst research using genetically modified microorganism (GMM) is actively being pursued in food industry. However, domestic food and food additive regulation standards and the number of examination management examples currently used in industry is lacking significantly. Up till now, there are only 6 examples of domestic GMM examination and approval cases for food production purposes and furthermore they are limited to the production of functional sweeteners. Domestically, although GMM is developed as a processing aid (contained use), if they are used in the production of food, the safety of GMM, including environmental safety, is evaluated. Also the produced food or food additives using GMM need to be separately examined and approved as a novel food. On the other hand, imported products produced using GMM need to gain approval for the final product only. Thus the expense and the time to obtain regulatory approval is advantageous for imported products versus domestically produced products. This commentary is written to create the opportunity to reform the current domestic food GMM regulation by comparing and discussing domestic and foreign case analyses of safety evaluation of GMM and related regulations.

• Applied Chemistry for Engineering
• /
• v.22 no.5
• /
• pp.562-565
• /
• 2011

In this study, we developed a bioprocess using Clostridium ljungdahlii as a biological catalyst to produce bio-ethanol, and the effect of pH on microbial growth and ethanol production was investigated. From the results of fermentation at various initial pH condition without pH control, pH of fermentation broth decreased to 4.5 within 24 h due to accumulation of by-product acetic acid and both microbial growth and ethanol production were stopped. The experimental result of initial pH 8 showed the highest microbial growth and ethanol production (0.53 g/L), since the pH drop was relatively slow. From the experiment of pH 7 maintained fermentation using pH controllable bioreactor, the maximum cell dry weight of 1.65 g/L and the maximum ethanol concentration of 1.43 g/L were obtained within 24 h. In conclusion, the C. ljungdahlii growth was enhanced by pH maintenance of neutral range, and the ethanol production was also enhanced based on the growth-associated ethanol production characteristics of C. ljungdahlii.

• Korean Journal of Food Science and Technology
• /
• v.54 no.2
• /
• pp.185-195
• /
• 2022

To enable the widespread use of buckwheat and create novel consumer demands through improved food processing techniques, we compared the quality characteristics of roasted groats following different processing and brewing methods for common and tartary buckwheat. The various processing steps resulted in significant reductions in rutin content for both buckwheat species, while the quercetin content increased in the tartary buckwheat. The fully processed tea products showed dramatic differences in rutin content, which varied based on the buckwheat species, formulation, and brewing method. Tartary buckwheat contained an average of 61 times more rutin than common buckwheat. The tartary buckwheat variety, Hwanggeum-miso, was used to determine an optimal roasting temperature of 70-80℃. Finally, we suggest that consumers who want buckwheat tea rich in rutin would prefer hand-drip-extracted tea, while those who want tea with less bitterness, sweetness, and good flavor would prefer the cold-brewed method.

• Membrane Journal
• /
• v.33 no.6
• /
• pp.352-361
• /
• 2023

Steam methane reforming is currently the most widely used technology for producing hydrogen, a clean fuel. Hydrogen produced by steam methane reforming contains impurities such as carbon monoxide, and it is essential to undergo an appropriate post-purification step for commercial usage, such as fuel cells. Recently, membrane separation technology has been gaining great attention as an effective purification method; in this study, we evaluated the feasibility of using commercial polysulfone membranes for biogas upgrading to separate and recover hydrogen from a hydrogen/carbon monoxide gas mixture. Initially, we examined the physicochemical properties of the commercial membrane used. We then conducted performance evaluations of the commercial membrane module under various conditions using mixed gas, considering factors such as stage-cut and operating pressure. Finally, based on the evaluation results, we carried out simulations for process design. The maximum H₂ permeability and H₂/CO separation factor for the commercial membrane process were recorded at 361 GPU and 20.6, respectively. Additionally, the CO removal efficiency reached up to 94%, and the produced hydrogen concentration achieved a maximum of 99.1%.