• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2813-2817
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• 2014

A new magnetic semiconductor material was synthesized to enable separation after a liquid-type photocatalysis process. Core@shell-structured $CuFeS_2@TiO_2$ magnetic nanoparticles were prepared by a combination of solvothermal and wet-impregnation methods for photocatalysis applications. The materials obtained were characterized using X-ray diffraction, transmission electron microscopy, ultraviolet-visible, photoluminescence spectroscopy, Brunauer-Emmett-Teller surface area measurements, and cyclic voltammetry. This study confirmed that the light absorption of $CuFeS_2$ was shifted significantly to the visible wavelength compared to pure $TiO_2$. Moreover, the resulting hydrogen production from the photo-splitting methanol/water solution after 10 hours was more than 4 times on the core@shell structured $CuFeS_2@TiO_2$ nanocatalyst than on either pure $TiO_2$ or $CuFeS_2$.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.6
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• pp.396-401
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• 2014

Nanomaterials have been widely used in many fields. This study investigates the effects of metal oxide nanoparticles (CuO, NiO, $TiO_2$, $Fe_2O_3$, $Co_3O_4$, ZnO) on germination and germination index (G.I.) of seeds, Lactuca and Raphanus. Under aqueous exposure, CuO on Lactuca shows the most significant impacts on activities compared to others, showing $EC_{50s}$ for germination and G.I. as 0.46 mg/L and 0.37%, respectively. The effects of nanoparticle phytotoxicity on seed Lactuca was much higher than that of Raphanus. In general, the toxicities on seed germination and germination index were as following orders : CuO > ZnO > NiO ${\gg}$ $TiO_2$, $Fe_2O_3$, $Co_3O_4$. No measurable inhibition was observed at 1,000 mg/L (maximum exposure concentration) of $TiO_2$, $Fe_2O_3$, $Co_3O_4$.

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

• Clean Technology
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• v.23 no.1
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• pp.27-33
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• 2017

In this study, toxicities of seven metals (Cu, Cd, Cr, As(III), As(V), Zn, Ni) and five metal oxide nanoparticles (NPs: CuO, ZnO, NiO, $TiO_2$, $Fe_2O_3$) were evaluated based on the growth of Chlorella vulgaris. Effect on algae growth was evaluated by integrating the results of absorption, chlorophyll content, and cell count. The toxicity rankings of metals was observed as Cr ($0.7mgL^{-1}$) > Cu ($1.7mgL^{-1}$) > Cd ($3.2mgL^{-1}$) > Zn ($3.9mgL^{-1}$) > Ni ($13.2mgL^{-1}$) > As(III) ($17.8mgL^{-1}$) ${\gg}$ As(V) (> $1000mgL^{-1}$). Slightly different orders and sensitivities of metal toxicity were examined depending on endpoints of algal growth. In case of NPs, regardless of endpoints, similar toxicity rankings of NPs ($TEC_{50}$) were observed, showing ZnO ($2.4mgL^{-1}$) > NiO ($21.1mgL^{-1}$) > CuO ($36.6mgL^{-1}$) > $TiO_2$ ($62.5mgL^{-1}$) > $Fe_2O_3$ ($82.7mgL^{-1}$). These results indicate that an integrating results of endpoints might be an effective strategy for the assessment of contaminants.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.206-214
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• 2005

Heterogeneously-catalyzed oxidation of aqueous phase trichloroethylene (TCE) over supported metal oxides has been conducted to establish an approach to eliminate ppm levels of organic compounds in water. A continuous flow reactor system was designed to effect predominant reaction parameters in determining catalytic activity of the catalysts for wet TCE decomposition as a model reaction. 5 wt.% $CoO_x/TiO_2$ catalyst exhibited a transient period in activity vs. on-stream time behavior, suggesting that the surface structure of the $CoO_x$ might be altered with on-stream hours; regardless, it is probable to be the most promising catalyst. Not only could the bare support be inactive for the wet decomposition reaction at $36^{\circ}C$, but no TCE removal also occurred by the process of adsorption on $TiO_2$ surface. The catalytic activity was independent of all particle sizes used, thereby representing no mass transfer limitation in intraparticle diffusion. Very low TCE conversion appeared for $TiO_2$-supported $NiO_x$ and $CrO_x$ catalysts. Wet oxidation performance of supported Cu and Fe catalysts, obtained through an incipient wetness and ion exchange technique, was dependent primarily on the kinds of the metal oxides, in addition to the acidic solid supports and the preparation routes. 5 wt.% $FeO_x/TiO_2$ catalyst gave no activity in the oxidation reaction at $36^{\circ}C$, while 1.2 wt.% Fe-MFI was active for the wet decomposition depending on time on-stream. The noticeable difference in activity of the both catalysts suggests that the Fe oxidation states involved to catalytic redox cycle during the course of reaction play a significant role in catalyzing the wet decomposition as well as in maintaining the time on-stream activity. Based on the results of different $CoO_x$ loadings and reaction temperatures for the decomposition reaction at $36^{\circ}C$ with $CoO_x/TiO_2$, the catalyst possessed an optimal $CoO_x$ amount at which higher reaction temperatures facilitated the catalytic TCE conversion. Small amounts of the active ingredient could be dissolved by acidic leaching but such a process gave no appreciable activity loss of the $CoO_x$ catalyst.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.7
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• pp.706-713
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• 2010

The research seeks to find the optimal conditions for sonodegradation of naphthalene and phenol as exemplary organic pollutants to be subjected to ultrasound in varying frequencies (28 kHz, 580 kHz, and 1,000 kHz) and in the presence of different kinds of additive (T$TiO_2$, $H_2O_2$, $FeSO_4$, Zeolite, and Cu). In cases of both naphthalene and phenol, 580 kHz of ultrasound has proven to be the most effective among others at sonodegradation. Based on the observation that OH radicals are also produced in maximum under exposure of 580 kHz of ultrasound, we concluded that this frequency of ultrasound creates hospitable condition for the combined process of degradation by pyrolysis and oxidization. $FeSO_4's$ degradation rate and k1 value have increased by approximately 1.8 times compared with the results of the solutions without any additives. This seems to be the result of ultrasound reaction which, accompanied by Fenton's reaction, increased the oxidative degradation and the production of OH radicals. However, application of ultrasound and Fenton's reaction is limited to the batch type conditions, as its use in continuous system can cause loss of iron or decay of the cistern, thereby creating additional pollutants. When the additive is replaced with $TiO_2$, on the contrary, the rate of sonodegradation has increased up to 20% compared to when there was no additive. We therefore conclude that $TiO_2$ could prove to be an effective additive for ultrasound degradation in continuous treatment system.

• Journal of the Korean Magnetics Society
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• v.9 no.1
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• pp.35-40
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• 1999

Sr substituted materials for some barium in M-type barium ferrite powder and Co-Ti substituted Sr-Ba hexagonal ferrite powder were prepared by citrate sol-gel method and 2 MOE sol-gel method these hexaferrite particles were reduced for 1hr in the hydrogen gas. The reduction temperatures were varied in the range of 250 $^{\circ}C$ to 500 $^{\circ}C$. X-ray diffraction patterns were measured using diffractometer with Cu $K_{\Alhpa}$ radiation. Mossbauer absorption spectra were measured with a constant acceleration spectrometer. We have focused on studying the origin of increasing $M_s$ by M$\"{o}$ssbauer spectroscopy. Ferrite particles which were sintered at 105$0^{\circ}C$ were found to be typical magnetoplumbite structure and single phase. XRD patterns with varying the reduction temperatures in $Sr_{0.5}Ba_{0.5}Fe_{10}O_{19}$ indicates ferrites particles become composite hexaferrites containing $\alpha$-Fe at T_{red}=350 \;$^{\circ}C$$. On the otherhand, it was found that $Co^{2+}$ ions and $Ti^{4+}$ ions in $Sr_{0.7}Ba_{0.3}Fe_{10}CoTiO_{19}$ prevent from changing $Fe^{3+}$ ions to $\alpha$-Fe during the $H_2$ reduction. Comparing Mossbauer results with XRD results, we have determined most of $\alpha$-Fe are reduced from $4f_{vi}$ sites and 12k sites of $Fe^{3+}$ ions. These $\alpha$-Fe phase bring the induced anisotropy and increase saturation magnetization $M_s$.TEX>.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12S
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• pp.1195-1199
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• 2003

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, dielectric and piezoelectric properties of PSN-PZT[0.91Pb(Sb$\sub$1/2/Nb$\sub$1/2/)$\sub$0.03/(Zr$\sub$0.495/Ti$\sub$0.505/)$\sub$0.97/O$_3$-0.04Pb(Ni$\sub$1/2/W$\sub$1/2/)O$_3$+0.05BiFeO$_3$+0.3wt％MnO$_2$+0.6wt％CuO〕 ceramics were investigated according to Zr/Ti ratio. As Zr/Ti ratio is increased, electromechanical coupling factor(k$\sub$p/) and dielectric constant increased and then decreased after the ratio of Zr/Ti=50/50. Also, mechanical qualify factor(Q$\sub$m/) decreased and then increased after the ratio of Zr/Ti=50/50.

• 보존과학연구
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• s.22
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• pp.93-114
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• 2001

The composition analysis of Danchung pigments at Geunjeongjeon Hall in Gyeongbokgung Palace were carried out by FXRF and MXRD. The analytical result of the inside pigments at Geunjeongjeon showed that these painted in use the mineral pigments. Gold pigment was pure gold(Au).The main composition identified in green pigments were chalcanthite($CuSO_4$.$5H_2O$) and celadonite($K(Mg, Fe, Al)_2$.$(Si, Al)_4O_10(OH)_2$ ). Red pigments werecinnnabar(HgS).The analytical result of the outside pigments at Geunjeongjeon revealed that these applied to the artificial synthetic pigment. Yellow pigment was chromeyellow($PbCrO_4$). The main composition identified in red pigments were red lead($Pb_3O_4$)and hematite($Fe_2O_3$). Green pigments were emeral green($C_2H_3A_s3Cu_2O_8$) and chromegreen($Cr_2O_3$). Blue pigment was lazurite($Na_6Ca2Al_6Si_6O_24(SO_4)_2$), titanium dioxide($TiO_2$) of white pigment.

• Journal of Environmental Health Sciences
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• v.20 no.1
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• pp.62-67
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• 1994

Introduction : Recently, water and environmental pollution becomes serious social problem and high technology makes this pollution accelerate. Hydrogen sulfide, the main subject of our research, is one of the most dangerous air pollutant like SO$_x$ and NO$_x$. The major contaminant in coal gasification is H$_2$S, which is very toxic, hazardous and extremely corrosive. Therefore, control of hydrogen sulfide to a safe level is essential. Although commercial desulfurization process called liquid scrubbing is effective for removal of H$_2$S, it has drawbacks, the loss of sensible heat of the gas and costly wastewater treatment. Many investigations are carried out about high-temperature removal ol H$_2$S in hot coal-derived gas using metal oxide or mixed metal qxide sorbents. It was reported that ZnO was very effective sorbent for H2S removal, but it has big flaw to vaporize elemental zinc above 600\ulcorner \ulcorner As alternative, metal oxides such as CaO, $Fe_2O_3$, TiO$_2$ and CuO were added to ZnO. Especially, different results are reported for $Fe_2O_3$ additive. Tamhankar et al. reported SiO$_2$ with 45 wt% $Fe_2O_3$ sorbent is favorable for removal of H$_2$S and regeneration.