• Journal of the Korean earth science society
• /
• v.28 no.1
• /
• pp.112-122
• /
• 2007

It is known that coal-derived fly ashes have the unique chemical composition and mineralogical characteristics. Since iron oxides in coal fly ash are enriched with heavy metals, the subsurface media including soils, underground water, and sea water are highly likely contaminated with heavy metals when the heavy metals are leached from fly ashes by water-fly ash interactions. The purpose of this study was to investigate how indigenous bacteria affect heavy metal leaching and mineralogy in fly ash slurry during the fly ash-seawater interactions in the ash pond located in Dangjin seashore, Korea. The average pH of ash pond seawater was 8.97 in nature. Geochemical data showed that microbial activity sharply increased after the 7th day of the 60-day course batch experiments. Compared with other samples including autoclaved and natural samples, ${SO_4}^{2-}$ was likely to decrease considerably in the fly ash slurry samples when glucose was added to stimulate the microbial activity. Geochemical data including Eh/pH, alkalinity, and major and trace elements showed that the bacteria not only immobilize metals from the ash pond by facilitating the chemical reaction with Mn, Fe, and Zn but may also be able to play an important role in sequestration of carbon dioxide by carbonate mineral precipitation.

• Journal of the Microelectronics and Packaging Society
• /
• v.21 no.1
• /
• pp.7-11
• /
• 2014

Recently, the buffer layers consisting of poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT-PSS) are extensively used to improve power conversion efficiency (PCE) of organic solar cells. However, PEDOT-PSS is not suitable for mass production of organic solar cells due to its intrinsic acid and hygroscopic properties. Moreover, because of chemical reactions between indium tin oxide (ITO) layer and PEDOT-PSS layer, the interface is not stable. For these reasons, alternative materials such as $V_2O_5$ have been developed to be an effective buffer layer. In this work, we used $V_2O_5$/Ag/ITO multilayer structure for the anode buffer layer. With variation of thickness of Ag layer, we investigated the optical and electrical properties of $V_2O_5$/Ag/ITO multi-layer films. As a result, we found that the electrical properties were improved with increasing Ag thickness while optical transmittance decreases in visible wavelength region. From the calculation of figure of merit (FOM) which is used to evaluate proper structure for transparent of optoelectronic, $V_2O_5$/Ag/ITO multilayer electrode was optimized with 4 nm thick Ag layer in optical (88% in transmittance) and electrical ($4{\times}10^{-4}{\Omega}cm$) properties. This indicates that $V_2O_5$/Ag/ITO multilayer electrode could be a candidate for the anode of optoelectronic devices.

• Applied Chemistry for Engineering
• /
• v.28 no.5
• /
• pp.576-580
• /
• 2017

In the present paper, the thermal deactivation characteristics of plate-type commercial $V_2O_5-WO_3/TiO_2$ SCR catalyst were investigated. For this purpose, the plate-type catalyst was calcined at different temperatures ranging from $500^{\circ}C$ to $800^{\circ}C$ for 3 hours. Structural and morphological changes were characterized byXRD, specific surface area, porosity, SEM-EDS and also NOx conversion with ammonia according to the calcine temperature. The NOx conversion decreased with increasing calcine temperature, especially when the catalysts were calcined at temperatures above $700^{\circ}C$. This is because the crystal phase of $TiO_2$ changed from anatase to rutile, and the $TiO_2$ grain growth and $CaWO_4$ crystal phase were formed, which reduced the specific surface area and pore volume. In addition, $V_2O_5$, which is a catalytically active material, was sublimated or vaporized over $700^{\circ}C$, and a metal mesh used as a support of the catalyst occurred intergranular corrosion and oxidation due to the formation of Cr carbide.

• Journal of the Korean Electrochemical Society
• /
• v.13 no.3
• /
• pp.211-216
• /
• 2010

Boron trifluoride lithium methacrylate ($BF_3$LiMA)-based gel polymer electrolytes (GPEs) were synthesized with various $BF_3$LiMA concentration to elucidate the effect on ionic conductivity and electrochemical stability by a AC impedance and linear sweep voltammetry (LSV). As a result, the highest ionic conductivity reached $5.3{\times}10^{-4}Scm^{-1}$ at $25^{\circ}C$ was obtained for 4 wt% of $BF_3$LiMA. Furthermore, high electrochemical stability up to 4.3 V of the $BF_3$LiMA-based GPE was observed in LSV measurement since the counter anion was immobilized in this self-doped system. On the other hand, it was assumed that there was a rapid decomposition of electrolytes on a lithium metal electrode which results in a high solid electrolyte interface (SEI) resistance. However, a high stability toward graphite or lithium cobalt oxide (LCO) electrode thereby a low SEI resistance was observed from the AC impedance measurement as a function of storage time at $25^{\circ}C$. Consequently, the high ionic conductivity, good electrochemical stability and the good interfacial compatibility with graphite and LCO were achieved in $BF_3$LiMA-based GPE.

• Journal of the Korean Chemical Society
• /
• v.35 no.3
• /
• pp.226-232
• /
• 1991

Adsorption and oxidation of polychlorinated phenols by suspended ${\sigma}-MnO_2$ in aqueous solution have been studied. Of the proposed mechanism, adsorption reaction of chlorophenols onto ${\sigma}-MnO_2$(s) depended upon the pH of the solution and the concentration of chlorophenol. Adsorption isotherms showed a reasonably good fit to the Langmuir isotherm. From the pH dependence of adsorption partition coefficient and the linear relationship between octanol-water partition coefficient and adsorption partiton coefficient of chlorophenol, it is estimated that adsorption is dominated by its hydrophobicity. The rate of electron transfer reaction evaluated from the rate of reductive dissolution of ${\sigma}-MnO_2$(s) depended linearly upon the concentration of chlorophenol and the pH of medium. Observed rate constants ($K_0$) of the meta-substituted chlorophenol were lower than that of the ortho-or para-chlorophenol because of resonance effect of chlorophenoxy radical. It is indicated that this radical is produced in the adsorption process and the electron transfer reaction is rate determining.

• Journal of Conservation Science
• /
• v.33 no.1
• /
• pp.25-33
• /
• 2017

The stone lantern of the four guardian kings in the Beopjusa temple at Boeun was mainly made of biotite granodiorite consisting of porphyritic-textured potassium feldspar and included in ilmenite series. A base stone made of alkali granite was buried, after founded its place during an earlier restoration process. Cracking and break out are noticeable on this object. In addition, discoloration, salt crusting, and epiphytes were observed. The lantern was vulnerable in terms of physical and structural stability caused by cracking in the front and back of the light chamber and in the non-horizontal direction. According to the conservational condition of the stone lantern, structural reinforcement was carried out based on calculations, including those on the position, size, and anchor length of the titanium stiffener. Chemical and biological pollutants were washed off without damage to the surface of the stone material. Oxygenated iron pieces were replaced with titanium. Ethyl silicate was applied to the surface of the lantern for consolidation and smooth drainage.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.39 no.3
• /
• pp.406-413
• /
• 2010

To enhance the yield and bioactivity of hot-water extract from herbal medicine, Astragalus membranaceus was hydrolyzed with carbohydrases, such as ClariSEB and Fungamyl. After hot-water extracts were prepared from each hydrolysate (HW-C/F), physicochemical property, antioxidant activity and sensory property were evaluated. The solid content ($^{\circ}Brix$) of HW-C/F was higher than hot-water extract from A. membranaceus no treated enzyme (control). Although pH of HW-C/F was lower than that of the control, the acidity was higher. Lightness of Hunter's color values was increased in HW-C/F whereas redness and yellowness were decreased. The contents of reducing sugar, flavonoid and polyphenol of HW-C/F were higher than the control but the content of ascorbic acid was not different from control. The inhibitory activity of HW-C/F against lipid peroxidation was slightly higher than control, but DPPH radical scavenging, ABTS reducing, metal chelating activities were significantly increased by HW-C/F. The sensory evaluation also revealed that the sensory panelists preferred HW-C/F to that of control. Therefore, hydrolysis by carbohydrases for preparation of hot-water extract from A. membranaceus is one of the good methods to improve antioxidative activity and sensory property of hot-water extract.

• Clean Technology
• /
• v.21 no.1
• /
• pp.39-44
• /
• 2015

This study investigated the effects of six metal oxide nanoparticles (NPs: CuO, NiO, TiO₂, Fe₂O₃, Co₃O₄, ZnO) on seed germination and germination index (G.I) for five types of seeds: Brassica napus L., Malva verticillata L., Brassica olercea L., Brassica campestris L., Daucus carota L. NPs of CuO, ZnO, NiO show significant toxicity impacts on seed activities [CuO (6-27 mg/L), ZnO (16-86 mg/L), NiO (48-112 mg/L)], while no significant effects were observed at > 1000 mg/L of TiO₂, Fe₂O₃, Co₃O₄. Tested five types of seed showed different sensitivities on seed germination and root activity, especially on NPs of CuO, ZnO, NiO. Malva verticillata L. seed was highly sensitive to toxic metal oxide NPs and showed following EC₅₀s : CuO 5.5 mg/L, ZnO 16.4 mg/L, NiO 53.4 mg/L. Mostly following order of toxicity was observed, CuO > ZnO > NiO > Fe₂O₃ ≈ Co₃O₄ ≈ TiO₂, where slightly different toxicity order was observed for carrot, showing CuO > NiO ≈ ZnO > Fe₂O₃ ≈ Co₃O₄ ≈ TiO₂.

• Journal of the Korean Chemical Society
• /
• v.42 no.4
• /
• pp.422-431
• /
• 1998

Tridentate Schiff base ligands such as $SIPH_2,\;SIPCH_2,\;HNIPH_2,\;and\; HNIPCH_2$ were prepared by the reaction of salicylaldehyde and 2-hydroxy-l-naphthaldehyde with 2-aminophenol and 2-amino-p-cresol. The structures and properties of ligands and their Co(II) complexes were investigated by elemental analysis, $^1H$NMR, IR, UV-visible spectra, and thermogravimetric analysis. The molar ratio of Schiff base to the metal of complexes was found to be 1:1. Co(II) complexes were contemplated to be hexa-coordinated octahedral configuration containing three water molecules. The redox process of ligands and complexes in DMSO solution containing 0.1 M TBAP as a supporting electrolyte were investigated by cyclic voltammetry with glassy carbon electrode. The redox process of the tridentate Schiff base ligands was totally irreversible. The redox process of Co(II) complexes were irreversible and one electron processes by two steps in diffusion controlled reaction. The reduction potential of the Co(II) complexes was shifted to the positive direction in the order [Co(Ⅱ)$(HNIPC)(H_2O)_3$]>[Co(Ⅱ)$(HNIP)(H_2O)_3$]>[Co(II)$(SIPC)(H_2O)_3$]>[Co(Ⅱ)$(SIP)(H_2O)_3], and their dependence on ligands were not so high.

• Applied Biological Chemistry
• /
• v.47 no.2
• /
• pp.244-250
• /
• 2004

Biological activities and application of Sanguisorbae officinalis L. were investigated. In the enzymological physiological activities, the electron donating ability (EDA) was 54.9% in 10 ppm and it was over 90% over 50 ppm and SOD-like activity was high as 65.4% in 1000 ppm, it was gradual increased. As inhibitory effect of xanthine oxidase, it was 17.9% in 200 ppm and little low as 36.9% in 500 ppm and inhibitory effect of tyrosinase. As the result of measuring the lipid oxidation, all the concentrations of medical ion treatments had the ability to keep it from acidification and metal ion blocking effects about the lipid oxidation promoting factors ($Fe^{2+}$ and $Cu^{2+}$), $Fe^{2+}$ was better than $Cu^{2+}$ and all concentrations of medical ion treatments was 40% in 50 ppm. When it was applied into normal skin-softener it showed safe effect so that we can expect that as the natural material of cosmetics.