• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.563-567
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• 1999

Reverse osmosis concentration for cephalosproin C was studied using a polyamide composite membrane, FT-30 in spiral wound type with high solute rejection. The experiments were carried out in the aqueous solution of cephalosporin C for water flux, solute rejection and mass transfer coefficient under applied pressure of $4{\sim}20kg/cm^2$, feed concentration of 100~1000 mg/L and feed velocity of 2.8 and 5.6 L/min at room temperature. The effect of operating pressure on the separation of cephalosporin C showed that permeate flux increased with increasing operation pressure. These results are consistent with those predicted by Kedem-Katchalsky model. Solute rejection was nearly 1. The increase of feed concentration caused the reduction of cephalosporin C rejection, which was higher at low concentration than at high concentration, but degree of reduction was small.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.659-666
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• 2019

Proton exchange membrane fuel cells (PEMFCs) generate electricity by electrochemical reactions of hydrogen and oxygen. PEMFCs are expected to alternate electric power generator using fossil fuels with various advantages of high power density, low operating temperature, and environmental-friendly products. PEMFCs have widely been used in a number of applications such as fuel cell vehicles (FCVs) and stationary fuel cell systems. However, there are remaining technical issues, particularly the long-term durability of each part of fuel cells. Degradation of a carbon supported-platinum catalyst in the anode and cathode follows various mechanistic origins in different fuel cell operating conditions, and thus accelerated stress test (AST) is suggested to evaluate the durability of electrocatalyst. In this article, comparable protocols of the AST durability test are intensively explained.

• Proceedings of the Microbiological Society of Korea Conference
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• 2007.05a
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• pp.80-82
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• 2007

We have isolated numerous cold deep-sea adapted microorganisms (piezophilic, formerly referred to as "barophilic" bacteria) using deep-sea research submersibles. Many of the isolates are novel psychrophilic bacteria, and we have identified several new piezophilic species, i.e., Photobacterium profundum, Shewanella violacea, Moritella japonica, Moritella yayanosii, Psychromonas kaikoi, and Colwellia piezophila. These piezophiles are involving to five genera in gamma-Proteobacteria subgroup and produce significant amounts of unsaturated fatty acids in their cell membrane fractions to maintain the membrane fluidity in cold and high-pressure environments. Piezophilic microorganisms have been identified in many deep-sea bottoms of many of the world oceans. Therefore, these microbes are well distributed on our planet. One of the isolated deep-sea piezophiles, Shewanella violacea strain DSS12 is a psychrophilic, moderately piezophilic bacterium from a sediment sample collected at the Ryukyu Trench (depth: 5,110 m), which grows optimally at 30 MPa and $8^{\circ}C$ but also grows at atmospheric pressure (0.1 MPa) and $8^{\circ}C$. We have examined this strain to elucidate the molecular basis for gene regulation at different pressure conditions because this strain is useful as a model bacterium for comparing the various features of bacterial physiology under pressure conditions. In addition, we completed the sequencing of the entire genome of this piezophilic bacterium and we expect that many biotechnologically useful genes will be identified from the genome information.

• Journal of Microbiology and Biotechnology
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• v.20 no.3
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• pp.447-459
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• 2010

Bacterial diversity of two distinct wastewater treatment systems, conventional activated sludge (CAS) and membrane bioreactor (MBR), of petroleum refineries were investigated through 16S rRNA gene libraries. Sequencing and phylogenetic analysis showed that the bacterial community composition of sludge samples was distinct between the two wastewater treatment systems. MBR clones belonged predominantly to Class Betaproteobacteria, represented mainly by genera Thiobacillus and Thauera, whereas CAS clones were mostly related to Class Alphaproteobacteria, represented by uncultured bacteria related to Order Parvularculales. Richness estimators ACE and Chao revealed that the diversity observed in both libraries at the species level is an underestimate of the total bacterial diversity present in the environment and further sampling would yield an increased observed diversity. Shannon and Simpson diversity indices were different between the libraries and revealed greater bacterial diversity for the MBR library, considering an evolutionary distance of 0.03. LIBSHUFF analyses revealed that MBR and CAS communities were significantly different at the 95% confidence level ($P{\leq}0.05$) for distances $0{\leq}D{\leq}0.20$. This work described, qualitatively and quantitatively, the structure of bacterial communities in industrial-scale MBR and CAS processes of the wastewater treatment system from petroleum refineries and demonstrated clearly differentiated communities responsible for the stable performance of wastewater treatment plants.

• Korean Journal of Environmental Agriculture
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• v.15 no.3
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• pp.306-315
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• 1996

This study was performed to develop the biological treatment technology of wastewater polluted with heavy metals. The lead-tolerant microorganism, Pseudomonas aeruginosa which possessed the ability to accumulate lead, was isolated from the industrial wastewater polluted with various heavy metals. The characteristics of lead accumulation in the cells and the recovery of the lead there from were investigated. Removal rate of lead from the solution containing 100mg/l of lead by the lead-tolerant microorganism was more than 97% at 48 hours after inoculation with the microorganism. A large number of the electron-dense granules were found mainly on the cell wall and cell membrane fractions, when determined by transmission electron microscopy. Energy dispersive X-ray spectroscopy revealed that the electron-dense granules were lead complex with the substances binding heavy metals. The lead accumulated into cells was not desorbed by distilled water, but more than 87% of the lead accumulated was desorbed by 0.1M-EDTA. The residues of the cells after combustion at $550^{\circ}C$ amounted to about 30% of the dry weight of the cells. EDS analysis showed that the residues were relatively pure lead compounds containing more than 86% of lead.

• Applied Biological Chemistry
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• v.40 no.6
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• pp.531-535
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• 1997

An efficient process for recovery of calcium from the eggshell was developed and some organic acids were used in an attempt to enhance the degree of calcium ionization. Eggshell membrane was readily separated from crushed eggshell based on the differences in specific gravities. The conditions which allowed most efficient membrane removal were found to be 30 rpm of speed, 30 min of residence time and 0.08 of volume fraction. It took 3 hours for the eggshell powder prepared at $1000^{\circ}C$ to reach L value of 90 with the Hausner ratio being 1.43. The calcium ion concentrations were 990, 3500, 3900 and 4200 ppm in pure water, acetic acid, citric acid and lactic acid$(0.05{\sim}3%)$ aqueous solution, respectively. The degrees of ionization of calcium-citrate-malate complex(CCM), calcium-citric acid complex(CC) and calcium malic acid complex(CM) increased by 4 to 5 times compared to eggshell calcium powder.

• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.586-590
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• 2006

As one of electro active polymers for soft smart materials, the ionic polymer metal composites (IPMC) are easy to produce through chemical reduction processing and show high displacements at low voltage. When the IPMC actuates, the deformation depends on a few factors including the structure of based membrane, species and morphology of the metal electrodes, the nature of cations and the level of hydration. As previously published, we have been studying on improvement of actuation through surface electrode modification of IPMC to grasp the effect of electrode morphology on actuation. This study is comparative experiments through the chemical reaction and deposition by ion beam assisted deposition (IBAD) in order to prepare the very thin and homogeneous surface electrode of IPMC. The IPMCs were prepared with different surface roughness of polymer membrane, and the influence of the surface roughness on the actuation was studied. By investigating the electrical properties and driving displacement, the actuating properties of IPMC with different surface roughness were studied.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.319-323
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• 1999

Asymmetric polyetherimide membranes were prepared by phase inversion method. In the modification of the skin layers of polyetherimide membranes, the effects of NaOH concentration on the morphology and pervaporation separation of water-isopropanol mixtures were investigated. With increasing concentration of NaOH solution, polyamicacid structure was formed by the hydrolysis of imide group of polyetherimide, and the thickness of dense layer of the asymmetric membrane increased. In the pervaporation separation of water-isopropanol mixtures the overall permeation rate decreased and the separation factor increased with increasing concentration of NaOH solution. However, when the concentration of NaOH solution was very high, the permeation rate increased but separation factor decreased. From these results, it was found that the permeation behaviors of asymmetric polyetherimide membranes depended upon the concentration of NaOH solution. These modified membranes showed that both the permeation rate and separation factor increased as the operating temperature increased.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.469-474
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• 1998

Poly (vinyl alcohol) (PVA) membranes crosslinked with poly (styrene-co-maleic anhydride) (PSMAn) have been prepared by the solution method. To investigate the separation behavior of the crosslinked PVA/PSMAn membranes in the pervaporation process, the selective sorption experiment and swelling measurements of the membranes in ethanol-water mixtures of 30~90 wt % ethanol contents were conducted with equipment that was able to measure the concentration and amount of the liquid absorbed in the membranes. The membranes prepared in this study exhibited good selectivity toward water component in sorption and permeation. Also, in the feed containing ethanol more than 50 wt %, the permeation selectivity of the membrane showed better correlation with the sorption selectivity than that with the swelling ratio changing toward the crosslinking content. This behavior was consistence with a solution-diffusion model correlating permeation and sorption selectivity, and led to the conclusion that the permeation selectivity was determined by sorption step rather than by diffusion step in the membrane.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.386-391
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• 2014

Atmospheric-pressure nonthermal corona discharge plasma was applied to the sterilization of biologically contaminated scoria powder. Escherichia coli (E. coli) culture solution was uniformly sprayed throughout the scoria powder for artificial inoculation, which was well mixed to ensure uniformity of the batch. The effect of the key parameters such as discharge power, treatment time, type of gas and electrode distance on the sterilization efficiency was examined and discussed. The experimental results revealed that the plasma treatment was very effective for the sterilization of scoria powder; 5-min treatment at 15 W could sterilize more than 99.9% of E. coli inoculated into the scoria powder. Increasing the discharge power, treatment time or applied voltage led to an improvement in the sterilization efficiency. The effect of type of gas on the sterilization efficiency was in order of oxygen, synthetic air (20% oxygen) and nitrogen from high to low. The inactivation of E. coli under the influence of corona discharge plasma can be explained by cell membrane erosion or etching resulting from UV and reactive oxidizing species (oxygen radical, OH radical, ozone, etc.), and the destruction of E. coli cell membrane by the physical action of numerous corona streamers.