• Economic and Environmental Geology
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• v.42 no.5
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• pp.435-444
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• 2009

In situ stabilization of heavy metals through adsorption onto indigenous bacterial biofilm developed on soil particles was investigated. Biofilms were developed in soil columns by supply of various carbon sources such as acetate, lactate and glucose. During development of biofilms, acetate, lactate, and glucose solutions were flew out from the soil columns with volume ratios of 98.5%, 97.3%, and 94.7%, respectively, when compared with soil column supplied with deionized water. Decrease in effluent amounts through the soil columns amended with carbon sources over time indicated the formation of biofilms resulting in decrease of soil porosity. Solutions of Cd, Cr(VI), Cu, Pb, and Zn were injected into the biofilms supported on soil particles in the columns, and the dissolved heavy metals in effluents were determined. Concentrations of dissolved Cd, Cr(VI), Cu, and Zn in the effluents through biofilm columns were lower than those of control column supplied with deionized water. The result was likely due to enhanced adsorption of the metals onto biofilms. Efficiency of metal removal by biofilms depended on the type of carbon sources supplied. The enhanced removal of dissolved heavy metals by bacterial biofilms in this study may be effectively applied to technical development of in situ stabilization of heavy metals in natural soil formation contaminated with heavy metals.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2649-2654
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• 2014

Synthesis of north-5'-methylbicyclo[3.1.0]hexyl adenine and hypoxanthine nucleosides with an ethenyl group at C3' position was successfully achieved by a highly facile method. Methylbicyclo[3.1.0]hexanone (${\pm}$)-7 with three contiguous chiral centers and its epimer (${\pm}$)-6 was remarkably simply constructed only by four steps involving a carbenoid insertion reaction in the presence of rhodium (II) acetate dimer as a metal catalyst, giving a correct relative stereochemistry of the generated three chiral centers. Due to steric hindrance from the concave face of the bicyclo[3.1.0]hexanone system, a Grignard reaction of (${\pm}$)-7 with ethenylmagnesium bromide showed exclusive diastereoselectivity towards the b-face. The Grignard reaction chemoselectively proceeded without reacting with ester functionality. Coupling reaction of glycosyl donor (${\pm}$)-11 with 6-chloropurine nucleobase afforded only the desired $N^9$-alkylated nucleoside without the formation of $N^7$-regioisomer. By the conventional method, 6-chloro group was converted into 6-amino and 6-hydroxy groups to give the desired adenine and hypoxanthine bicyclo[3.1.0]hexyl carbanucleosides with 3'-ethenyl group, respectively.

• Journal of Periodontal and Implant Science
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• v.33 no.3
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• pp.499-518
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• 2003

The surface characteristics of titanium have been shown to have an important role in contact ossseointegration around the implant. Anodizing at high voltage produces microporous structure and increases thickness of surface titanium dioxide layer. The aim of present study was to analyse the response of rat calvarial osteoblast cell to commercially pure titanium and Ti-6A1-4V anodized in 0.06 mol/l ${\beta}$-glycerophosphate and 0.03 mol/l sodium acetate. In this study, rat calvarial osteoblasts were used to assay for cell viability and cell proliferation on the implant surface at 1,2,4,7 days. 1. Surface roughness was 1.256${\mu}m$ at 200V, and 1.745${\mu}m$ at 300V. 2. The thickness of titanium oxide layer was increased 1 ${\mu}m$ with the increase of 50V. 3. The proliferation rate of osteoblastic cells was increased with the increase of the surface roughness and the thickness of titanium oxide layer. 4. There was no difference in cell viability and cell proliferation between commercially pure titanium and Ti-6A1-4V anodized at the same condition. In conclusion, the titanium surface modified by anodizing was biocompatible, produced enhanced osteoblastic response. The reasons of enhanced osteoblast response might be due to reduced metal ion release by thickened and stabilized titanium dioxide layer and microporous rough structures.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.132-134
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• 2016

The Study mainly focused on bioremediation of 16 types PAHs and heavy metals in contaminated marine sediments at filed scale study using slow release biostimulant ball (BSB) was investigated. In our experiment, filed scale study ($1m{\times}1m$) was performed and the effect of BSB on PAHs and heavy metals were analysed. BSB size and distance were determined and optimum size and distance were 3cm and 5.5cm respectively. BSB containing nutrients of acetate, nitrate and sulphate which can enhance the activity of microorganism to increase degrading capacity of PAHs and enhance the heavy metals stabilization also to decrease bioavailability. PAHs containing 16 types of 2, 3, 4, 5 and 6 rings compound PAHs were found and to degrade upto 100% in 2, 3 rings, upto 90 to 94% in 4 and 5 rings and 6 ring compound was degrade up to 70%. For heavy metals stabilization percentage was increased using BSB sediment and exchangeable portion was decreased and residual portion was increased in all analysed heavy metals. BSB enhance the PAHs degradation and stabilization of heavy metals percentages. BSB is a promising method for remediation of PAHs and heavy metals in contaminated marine sediments.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.495-499
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• 2010

The biocatalytic capture of $CO_2$, and its precipitationas $CaCO_3$, over bovine carbonic anhydrase (BCA) immobilized on a pore-expanded SBA-15 support was investigated. SBA-15 was synthesized using TMB as a pore expander, and the resulting porous silica was characterized by XRD, BET, IR, and FE-SEM analysis. BCA was immobilized on SBA-15 through various approaches, including covalent attachment (BCA-CA), adsorption (BCA-ADS), and cross-linked enzyme aggregation (BCA-CLEA). The immobilization of BCA on SBA-15 was confirmed by the presence of zinc metal in the EDXS analysis. The effects of pH, temperature, storage stability, and reusability on the biocatalytic performance of BCA were characterized by examining para-nitrophenyl acetate (p-NPA) hydrolysis. The $K_{cat}/K_m$ values for p-NPA hydrolysis were 740.05, 660.62, and $680.11M^{-1}s^{-1}$, respectively, where as $K_{cat}/K_m$ for free BCA was $873.76M^{-1}s^{-1}$. The amount of $CaCO_3$ precipitate was measured quantitatively using anion-selective electrode and was found to be 12.41, 11.82, or 11.28 mg $CaCO_3$/mg for BCA-CLEA, BCA-ADS, or BCA-CA, respectively. The present results indicate that the immobilized BCA-CLEA, BCA-ADS, and BCA-CA are green materials, and are tunable, reusable, and promising biocatalysts for $CO_2$ sequestration.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.250-253
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• 2007

An evaporated Ti/Pd/Ag contact system is most widely used to make high-efficiency silicon solar cells, however, the system is not cost effective due to expensive materials and vacuum techniques. Commercial solar cells with screen-printed contacts formed by using Ag paste suffer from a low fill factor and a high shading loss because of high contact resistance and low aspect ratio. Low-cost Ni and Cu metal contacts have been formed by using electroless plating and electroplating techniques to replace the Ti/Pd/Ag and screen-printed Ag contacts. Ni/Cu alloy is plated on a silicon substrate by electro-deposition of the alloy from an acetate electrolyte solution, and nickel-silicide formation at the interface between the silicon and the nickel enhances stability and reduces the contact resistance. It was, therefore, found that nickel-silicide was suitable for high-efficiency solar cell applications. The Ni contact was formed on the front grid pattern by electroless plating followed by anneal ing at $380{\sim}400^{\circ}C$ for $15{\sim}30$ min at $N_{2}$ gas to allow formation of a nickel-silicide in a tube furnace or a rapid thermal processing(RTP) chamber because nickel is transformed to NiSi at $380{\sim}400^{\circ}C$. The Ni plating solution is composed of a mixture of $NiCl_{2}$ as a main nickel source. Cu was electroplated on the Ni layer by using a light induced plating method. The Cu electroplating solution was made up of a commercially available acid sulfate bath and additives to reduce the stress of the copper layer. The Ni/Cu contact was found to be well suited for high-efficiency solar cells and was successfully formed by using electroless plating and electroplating, which are more cost effective than vacuum evaporation. In this paper, we investigated low-cost Ni/Cu contact formation by electroless and electroplating for crystalline silicon solar cells.

• Journal of Microbiology and Biotechnology
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• v.30 no.2
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• pp.216-225
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• 2020

An esterase gene, estA1, was cloned from Alteromonas sp. 39-G1 isolated from the Beaufort Sea. The gene is composed of 1,140 nucleotides and codes for a 41,190 Da protein containing 379 amino acids. As a result of a BLAST search, the protein sequence of esterase EstA1 was found to be identical to Alteromonas sp. esterase (GenBank: PHS53692). As far as we know, no research on this enzyme has yet been conducted. Phylogenetic analysis showed that esterase EstA1 was a member of the bacterial lipolytic enzyme family IV (hormone sensitive lipases). Two deletion mutants (Δ20 and Δ54) of the esterase EstA1 were produced in Escherichia coli BL21 (DE3) cells with part of the N-terminal of the protein removed and His-tag attached to the C-terminal. These enzymes exhibited the highest activity toward p-nitrophenyl (pNP) acetate (C₂) and had little or no activity towards pNP-esters with acyl chains longer than C₆. Their optimum temperature and pH of the catalytic activity were 45℃ and pH 8.0, respectively. As the NaCl concentration increased, their enzyme activities continued to increase and the highest enzyme activities were measured in 5 M NaCl. These enzymes were found to be stable for up to 8 h in the concentration of 3-5 M NaCl. Moreover, they have been found to be stable for various metal ions, detergents and organic solvents. These salt-tolerant and chemical-resistant properties suggest that the enzyme esterase EstA1 is both academically and industrially useful.

• Analytical Science and Technology
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• v.6 no.5
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• pp.435-442
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• 1993

Carboxymethylated polyamine-polyurea resin loaded with rubeanic acid (RCCPPI resin) was obtained by 1 step chemical reaction between chlorocarboxymethylated polyamine-polyurea(CCPPI) resin as matrix polymer and rebeanic acid. This resin was confirmed with infrared spectrometry, elemental analysis, and thermal analysis(DSC). The adsorption characteristics of the heavy metal's on the resin were studied by measuring distribution coefficient($K_d$) with changing pH of the solutions and frontal chromatography. The enrichment, recovery, and analysis of trace heavy metals, such as cadmium, cerium, copper, nikel, lead, and zinc, in the presence of high concentrations of sodium, calcium, and acetate salts was possible quantitatively by a column packed with the resin at each optimum pH. Preconcentration factors were more than 25. To elute the adsorbed heavy metals on the resin, 0.025M EDTA solution(pH 9.0) was used.

• Journal of Hydrogen and New Energy
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• v.19 no.6
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• pp.498-504
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• 2008

Metal-reducing bacterium, Geobacter sulfurreducens is available for mediator-less microbial fuel cell (MFC) because it has biological nanowires(pili) which transfer electrons to outside the cell. In this study, in the anode chamber of the MFC system using G. sulfurreducens, the concentrations of NaCl, sodium phosphate and sodium bicarbonate as electrolytes were mainly optimized for the generation of electricity from acetate. 0.4%(w/v) NaClO and 0.5M $H_2SO_4$ could be utilized for the sterilization of acrylic plates and proton exchange membrane (major construction materials of the MFC reactor), respectively. When NaCl concentration in anode phosphate buffer increased from 5 to 50 mM, power density increased from 6 to $20\;mW/m^2$. However, with increasing sodium phosphate buffer concentration from 5 to 50 mM, power density significantly decreased from 18 to $1\;mW/m^2$. Twenty-four mM sodium bicarbonate did not affect electricity generation as well as pH under 50 mM phosphate buffer condition. Optimized anode chamber of MFC using G. sulfurreducens generated relatively high power density ($20\;mW/m^2$) with the maximum coulombic efficiency (41.3%).

• Clean Technology
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• v.20 no.3
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• pp.277-282
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• 2014

In this study, PU-LMO was made by immobilization of LMO on urethane foam (PU) with using an EVA as a binder. PU-LMO was characterized by using X-Ray Diffractometer (XRD) and Scanning Electron Microscopy (SEM). The optimal ratio of EVA/LMO for preparation of PU-LMO was 0.26 gEVA/gLMO. The adsorption of lithium ions by PU-LMO was found to follow the pseudo-second-order kinetic model. The equilibrium data fitted well with Langmuir isotherm model and the maximum removal capacity of lithium ions was 17.09 mg/g. The PU-LMO was found to have a remarkably high selectivity of lithium ions and high adsorption capacity because the distribution coefficient ($K_d$) of lithium ion was higher than those of other metal ions.