• Membrane Journal
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• v.31 no.6
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• pp.434-442
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• 2021

Poly(vinylidene fluoride) (PVDF) membrane has a good membrane durability because of its high mechanical resistance, thermal and chemical stability. However, the strong hydrophobic property of PVDF membrane can induce a low water permeability and easy fouling by proteins and organic matters. In order to improve the anti-fouling properties of PVDF membrane, the PVDF mixed matrix asymmetric membranes impregnated with biofunctional material 𝛽-cyclodextrin (𝛽-CD) in the membrane structure were prepared by phase inversion method. The membrane filtration experiments of pure water and BSA solution were performed using the PVDF/𝛽-CD mixed matrix asymmetric membranes prepared according to the 𝛽-CD contents. The experiments showed that the introduction of 𝛽-CD into the PVDF polymer matrix contributed to increase in the hydrophilic property of the PVDF membranes, and this led to the reduction of contact angles and improvement of anti-fouling properties. The PVDF/𝛽-CD membrane which was prepared using the dope solution with a 2 wt% 𝛽-CD content represented 64 L/m²·h of pure water flux, 95% of BSA rejection and maximum 80% of flux enhancements compared to flux results of the pristine PVDF membrane.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.6
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• pp.405-415
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• 2021

MMBR system has been suggested as a promising system to resolve harvesting problems induced from low settling efficiency of microalgae. And recently, a lot of research on reducing fouling at the MMBR system has investigated focused on EPS in many cases. EPS of microalgae mainly consists of polysaccharides and protein components, and is produced through photosynthesis and nitrogen-carbon metabolic pathways. Especially, P-EPS is one of major compounds which occur membrane fouling phenomenon, as its hydrophobic protein components cause floc formation and cake layer accumulation. And it is already known that almost every microalgae can metabolize P-EPS or Chl-a when nitrogen sources as a substrate is insufficient or exhausted situation. With the above backgrounds, uptake rates of P-EPS or Chl-a by Scenedesmus quadricauda according to the type of carbon source and nitrogen concentration were evaluated in order to verify correlation between carbon source vs P-EPS production, and indeed Scenedesmus quadricauda uses P-EPS or Chl-a when the amounts of nitrogen sourc es in the feed is not satisfied. As a result, it was shown that P-EPS and Chl-a production were increased proportional to nitrogen concentration under organic carbon condition. And especially, the amo unts of P-EPS and Chl-a in the cell were diminished with the nitrogen source becomes insufficient or exhausted. Because P-EPS accelerates fouling at the MMBR system, P-EPS degradation by Scenedesmus quadricauda in order to get nitrogen source may contribute to reducing fouling. About a affects of N-consumed Chl-a to the MMBR fouling, more survey is needed. On the contrary, considering the purpose of MMBR system of this study, i.e. harvesting useful high value microalgae efficiently feeding adequate industrial process wastewater, it seems like difficult to maintain satisfied metabolic activity and to harvest with high yield rate using nitrogen-poor MMBR feed.

• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.188-194
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• 2022

This work presents a non-destructive and straightforward approach to assemble a large-scale conductive electronic film made of a pre-treated single-walled carbon nanotube (SWCNT) solution. For effective electron transfer between the immobilized enzyme and SWCNT electronic film, we optimized the pre-treatment step of SWCNT with p-terphenyl-4,4"-dithiol and dithiothreitol. Glucose oxidase (GOx, a model enzyme in this study) was immobilized on the SWCNT electronic film following the positively charged polyelectrolyte layer deposition. The glucose detection was realized through effective electron transfer between the immobilized GOx and SWCNT electronic film at the negative potential value (-0.45 V vs. Ag/AgCl). The SWCNT electronic film-based glucose biosensor exhibited a sensitivity of 98 ㎂/mM·cm². In addition, the SWCNT electronic film biosensor showed the excellent selectivity (less than 4 % change) against a variety of redox-active interfering substances, such as ascorbic acid, uric acid, dopamine, and acetaminophen, by avoiding co-oxidation of the interfering substances at the negative potential value.

• Clean Technology
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• v.29 no.1
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• pp.71-75
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• 2023

In general, the presence of non-selective intercrystalline (grain boundary) defects in polycrystalline metal-organic framework (MOF) or zeolite membranes, which are known to be ca. 1 nm in size, causes lower membrane performance (selectivity) than the intrinsically expected. In this study we show that applying a thin polymeric coating of polydimethylsiloxane (PDMS) on a polycrystalline MOF membrane is effective to cap the non-selective intercrystalline defects and therefore improve membrane performance. To demonstrate the concept, first, polycrystalline UiO-66, one of Zr-based MOFs, membranes were prepared by an in-situ solvothermal growth. By controlling membrane growth condition with respect to growth temperature, we were able to obtain polycrystalline UiO-66 membranes at 150 ℃ with intercrystalline defects of which the quantity is not significant, so it can be plugged by the suggested PDMS deposition. Second, their performances were compared before and after the PDMS deposition. As expected, the PDMS deposition ended up with a noticeable increase in CO₂/N₂ ideal selectivity from 6 to 14, indicating successful intercrystalline defect plugging. However, the enhancement in CO₂/N₂ selectivity was accompanied by a significant reduction in CO₂ permeance from 5700 to 33 GPU because the PDMS deposition not only plugs defects but also forms a continuous coating on membrane surface, adding an additional transport resistance.

• Composites Research
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• v.19 no.5
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• pp.7-11
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• 2006

The improved SWNTs/PANi composite actuator films applicable to an artificial muscle were fabricated successfully using a new process of manufacture that consists of 90% pure single-walled carbon nanotubes (SWNT) and chemical polymerization. PANi is electrically conducting polyaniline polymer. The conductivities of the composite SWNTs/PANi film-type actuators and the pure PANi films fabricated were measured as 56.15 S/cm and 17.38 S/cm, respectively, by the 4-prove method. The conductivity of the composite actuator is 3.2 times higher than the pure PANi film. The fabricated composite actuator showed higher conductivity than any other similar ones. The quality of samples was investigated by an electron scanning microscope (SEM). To measure the actuating strains, a specially designed beam balance apparatus was developed and strains of the composite actuators was measured by a laser displacement sensor subjected to electric currents. During the operation, the sample was soaked in the $NaNO_3$ solution and the sine-wave voltage in the range of $+1V{\sim}-1V$ was applied. The length of the composite actuator changed from $l_0=12.690$ mm to $l_1=12.733$ so that the change of length was l=0.043 mm and the strain was 0.34 %. This is a very high strain for this kind of a composite actuator. Other result reported by Tahhan showed 0.23 % strain, so that the present result is improved by 48%.

• Analytical Science and Technology
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• v.19 no.1
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• pp.73-85
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• 2006

Blood serum concentrations of polychlorinated biphenyls (PCBs) were measured in employees who worked at a municipal solid waste incinerator (MSWI), members of residential community who lived near the MSWI (<0.3km) and members of residential community lived far from the MSWI (>10 km). Human blood serum samples were analyzed for all PCB congeners using high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). The mean levels of total PCBs and dioxin-like PCBs in 87 serum samples were 242.77 ng/g lipid and 8.83 TEQ pg/g lipid, respectively. The PCB homologue profiles showed that penta-, hexa-, hepta-chlorinated biphenyls contributed more than 80% of the total PCBs concentration. The most abundant congeners were PCB153, PCB138, PCB180, PCB187, PCB118. A statistical analysis was performed to determine whether there were significant correlations between PCB concentrations and specific variables such as age, gender, smoking habits, occupation, BMI (Body Mass Index) and time of residence. As a result, the age was found to be strongly correlated with serum PCB concentrations. In addition, there were strong correlations between total PCBs and PCB153 (r=0.93, p<.0001), dioxin-like PCBs and PCB118 (r=0.98, p<.0001). So these two congeners are satisfactory indicators for total PCB concentrations and dioxin-like PCBs in human blood respectively.

• Journal of the Korean Electrochemical Society
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• v.27 no.1
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• pp.32-39
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• 2024

The key components of a Phosphoric acid fuel cell (PAFC) are an electrode catalyst, an electrolyte matrix and a gas diffusion layer (GDL). In this study, we introduced a microporous layer on the GDL of PAFC to enhance liquid electrolyte management and overall electrochemical performance of PAFC. MPL is primarily used in polymer electrolyte membrane fuel cells to serve as an intermediate buffer layer, effectively managing water within the electrode and reducing contact resistance. In this study, electrodes were fabricated using GDLs with and without MPL to examine the influence of MPL on the performance of PAFC. Internal resistance and polarization curves of the unit cell were measured and compared to each other to assess the impact of MPL on PAFC electrode performance. As the results, the application of MPL improved power density from 170.2 to 192.1 mW/cm². MPL effectively managed electrolyte and water within the matrix and electrode, enhancing stability. Furthermore, the application of MPL reduced internal resistance in the electrode, resulting in sustained and stable performance even during long-term operation.

• Journal of the Korean Electrochemical Society
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• v.23 no.2
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• pp.39-46
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• 2020

Composite electrodes for rechargeable batteries generally consist of active material, electric conductor, and polymeric binder. And their composition and distribution within the composite electrode determine the electrochemical activity in the electrochemical systems. However, it is not easy to quantify the physical properties of composite electrodes themselves using conventional experimental analysis tools. So, 3D structural modeling and simulation can be an efficient design tool by looking into the contact areas between particles and electric conductivity within the composite electrode. In this study, while maintaining the composition (LiCoO₂ : Super P Li^® : Polyvinylidene Fluoride (PVdF) = 93 : 3 : 4 by wt%) and loading level (13 mg cm^-2) of the composite electrode, the effects of LiCoO₂ size (10 ㎛ and 20 ㎛) and electrode density (2.8 g cm^-3, 3.0 g cm^-3, 3.2 g cm^-3, 3.5 g cm^-3, 4.0 g cm^-3) on the physical properties are investigated using a GeoDict software. With this tool, the composite electrode can be efficiently designed to optimize the contact area and electric conductivity.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.2
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• pp.149-155
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• 2012

In this study, the functional properties of royal court (RC) soy sauces, Gungjung-kanjang, were analyzed in vitro. RC soy sauces, traditional soy sauce, and commercial soy sauces were fractionated based on an MW cut-off of 1,000. The total phenolic compounds smaller than and larger than 1,000 MW (low and high fraction) in RC soy sauces were determined to be $101.55{\pm}1.49\sim114.00{\pm}0.11$ mg/L and $32.51{\pm}0.32\sim113.47{\pm}0.43$ mg/L, respectively. The low fraction of RC soy sauces showed around 51% superoxide dismutase (SOD)-like activity, which was higher than other soy sauces. Among RC soy sauces, Cheong-jang showed significantly high activity. Significant differences in fibrinolytic and antibacterial activities were not observed between soy sauces. ${\alpha}$-Glucosidase inhibitory activities in the low and high fractions of RC soy sauces were in the range from $6.34{\pm}1.51\sim8.79{\pm}0.81$% and $5.72{\pm}1.29\sim7.94{\pm}0.34$%, respectively. However, ${\alpha}$-glucosidase inhibitory activity in the high fraction of Kot-jang soy sauce was 75.88%${\pm}$1.20%. Lipase inhibitory activities in the low fractions of RC soy sauces, especially Cheong-jang, Deot-kangang, Jin-jang, and Euyeuk-kanjang, were also measured.

• Korean Journal of Weed Science
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• v.30 no.4
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• pp.340-360
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• 2010

The depletion of fossil fuels, ecological problems associated with $CO_2$ emissions climate change, growing world population, and future energy supplies are forcing the development of alternative resources for energy (heat and electricity), transport fuels and chemicals: the replacement of fossil resources with $CO_2$ neutral biomass. Several options exist to cover energy supplies of the future, including solar, wind, and water power; however, chemical carbon source can get from biomass only. When used in combination with environmental friend production and processing technology, the use of biomass can be seen as a sustainable alternative to conventional chemical feedstocks. The biorefinery concept is analogous to today's petroleum refinery, which produce multiple fuels and chemical products from petroleum. A biorefinery is a facility that integrates biomass conversion processes and equipment to produce fuels, power, and value-added chemicals from biomass. Biorefinery is the co-production of a spectrum of bio-based products (food, feed, materials, and chemicals) and energy (fuels, power, and heat) from biomass [definition IEA Bioenergy Task 42]. By producing multiple products, a biorefinery takes advantage of the various components in biomass and their intermediates therefore maximizing the value derived from the biomass feedstocks. A biorefinery could, for example, produce one or several low-volume, but high-value, chemical or nutraceutical products and a low-value, but high-volume liquid transportation fuel such as biodiesel or bioethanol. Future biorefinery may play a major role in producing chemicals and materials as a bridge between agriculture and chemistry that are traditionally produced from petroleum. Industrial biotechnology is expected to significantly complement or replace the current petroleum-based industry and to play an important role.