• Bulletin of the Korean Chemical Society
• /
• v.35 no.12
• /
• pp.3535-3541
• /
• 2014

Bisphenol A is considered as pollutant, because it is toxic and hazardous to living organisms even at very low concentrations. Biological oxidation used for removing this organic from waste water is not suitable and consequently application of catalytic wet oxidation has been considered as one of the best options for treating bisphenol A. We have developed Fe/SBA-15, Ni/SBA-15 and Fe-Ni/SBA-15 as heterogeneous catalysts using the advanced impregnation method for oxidation of bisphenol A in water. The catalysts were characterized with physico-chemical characterization methods such as, powder X-ray diffraction (PXRD), FT-IR measurements, N2 adsorption-desorption isotherm, thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. This work illustrates activity of the catalysts for heterogeneous catalytic degradation reaction revealed with excellent conversion and recyclability. The degradation products identified were not persistent pollutants. GC-MS analysis identified the products: 2,4-hexadienedioic acid, 2,4-pentadienic acid and isopropanol or acetic acid. The leachability study indicated that the catalysts release very little metals to water. Therefore, the possibility of water contamination through metal leaching was almost negligible.

• Nuclear Engineering and Technology
• /
• v.52 no.10
• /
• pp.2299-2305
• /
• 2020

Zr alloy specimens were coated with Cr-Al alloy to enhance their resistance to oxidation. The coated samples were oxidized at 1200 ℃ in a steam environment for 300 s and showed extremely low oxidation when compared to uncoated Zr alloy specimens. The microstructure and elemental distribution of the oxides formed on the surface of Cr-Al alloys have been investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A very thin protective layer of Cr₂O₃ formed on the outer surface of the Cr-Al alloy, and a thin Al₂O₃ layer was also observed in the Cr-Al alloy matrix, near the surface. Our results suggest that these two oxide layers near the surface confers excellent oxidation resistance to the Cr-Al alloy. Even after exposure to a high temperature of 1200 ℃, inter-diffusion between the Cr-Al alloy and the Zr alloy occurred in very few regions near the interface. Analysis of the inter-diffusion layer by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) measurement confirmed its identity as Cr₂Zr.

• Journal of Microbiology and Biotechnology
• /
• v.21 no.7
• /
• pp.753-756
• /
• 2011

A methane-oxidizing bacterium was isolated from the enriched culture of a landfill cover soil. The closest relative of the isolate, designated M6, is Methylocystis sp. Based on a kinetic analysis, the maximum specific methane oxidation rate and saturation constant were 4.93 mmol gdry cell $weight^{-1}{\cdot}h^{-1}$ and 23${\mu}M$, respectively. This was the first time a kinetic analysis was performed using pure methanotrophic culture. The methane oxidation by M6 was investigated in the presence of aromatic (m- and pxylene and ethylbenzene) or sulfur (hydrogen sulfide, dimethyl sulfide, methanthiol) compounds. The methane oxidation was inhibited by the presence of aromatic or sulfur compounds.

• Membrane and Water Treatment
• /
• v.11 no.4
• /
• pp.257-274
• /
• 2020

There are many previous review articles are available to summarize either the characterization methods of effluent organic matter (EfOM) or the individual control treatment options. However, there has been no attempt made to compare in parallel the physicochemical treatment options that target the removal of EfOM from biological treatments. This review deals with the recent progress on the characterization of EfOM and the novel technologies developed for EfOM treatment. Based on the publications after 2010, the advantages and the limitations of several popularly used analytical tools are discussed for EfOM characterization, which include UV-visible and fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), size exclusion chromatography (SEC), and Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS). It is a recent trend to combine an SEC system with various types of detectors, because it can successfully track the chemical/functional composition of EfOM, which varies across a continuum of different molecular sizes. FT-ICR-MS is the most powerful tool to detect EfOM at molecular levels. However, it is noted that this method has rarely been utilized to understand the changes of EfOM in pre-treatment or post-treatment systems. Although membrane filtration is still the preferred method to treat EfOM before its discharge due to its high separation selectivity, the minimum requirements for additional chemicals, the ease of scaling up, and the continuous operation, recent advances in ion exchange and advanced oxidation processes are greatly noteworthy. Recent progress in the non-membrane technologies, which are based on novel materials, are expected to enhance the removal efficiency of EfOM and even make it feasible to selectively remove undesirable fractions/compounds from bulk EfOM.

• BMB Reports
• /
• v.34 no.1
• /
• pp.39-42
• /
• 2001

Previous studies indicate that B. subtilis protoporphyrinogen oxidase is poorly inhibited by diphenyl ether herbicides. To better understand the basis of this insensitivity, the enzyme was overexpressed as a soluble protein in E. coli, purified and characterized. The mechanism of oxidation of B. subtilis protoporphyrinogen IX was studied and the enzyme kinetic parameters were determined for protoporpyrinogen IX; $K_m$, and $k_{cat}$ were $6.3\;{\mu}M$ and $0.028\;h-^1$, respectively. The enzyme required flavin adenine dinucleotide as a cofactor and its activity was enhanced by 1 mM n-octylglucopyranoside. The nonenzymatic oxidation rate was dependent on the concentration of protoporphyrinogen IX, suggesting that the reaction involves a pre-equilibrium step followed by a rate-limiting step.

• Journal of Integrative Natural Science
• /
• v.3 no.3
• /
• pp.133-137
• /
• 2010

New synthetic route and characterization of alkyl-capped nanocrystalline silicon (R-n-Si) were achieved from the reaction of silicon tetrachloride with sodium/benzophenone ketal reducing agent followed by n-butyllithium. Surface of silicon nanoparticles was derivatized with butyl group. Effect of oxidation of silicon nanoparticle with benzophenone was investigated for their stabilization. Optical characteristics of silicon nanoparticles were characterized by fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), and photoluminescence (PL) spectroscopy. Butyl-capped silicon nanoparticles exhibited an emission band at 410 nm with excitation wavelength of 360 nm. Average size of n-butyl-capped silicon nanoparticles was obtained by particle size analyzer (PSA) and transmission electron microscopy (TEM). Average size of n-butyl-capped Si nanoparticles was about 6.5 nm.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.5
• /
• pp.1033-1037
• /
• 2008

A copper cyclam-type complex was successfully immobilized onto mesoporous silica SBA-16. Characterization by NIR spectroscopy and TGA analysis confirmed that copper cyclam complex is immobilized onto mesoporous SBA-16. The Cu(II)-Cyclam-SBA-16 was proven to be a good catalyst for oxidation reaction of cyclohexene with conversion up to 77.8% after 13 h reaction and providing a high selectivity to cyclohexenol and 3-hydroperoxycyclohex-1-ene. The results suggest that the copper species play a major role as catalyst via reversible redox cycles as proven by cyclic voltammetry analysis.

• Korean Journal of Materials Research
• /
• v.14 no.4
• /
• pp.281-286
• /
• 2004

The oxide scales formed on Ni-18W(at.%) coating that was electrodeposited on steel were investigated using XRD, SEM and TEM. The oxide scales consisted mainly of an outer NiO layer, and an inner thick ($NiWO_4$+NiO) mixed layer. The unoxidized coating below the oxide scale was rich in Ni and depleted in W, owing to the consumption of Wand the resultant Ni enrichment. The oxidation resistance of Ni-18W coating was poorer than that of the TiN coating, due to the formation of nonprotective NiWO$_4$. During oxidation, Ni and the substrate element of Fe diffused outward, while oxygen inward, according to the concentration gradients.

• Journal of the Microelectronics and Packaging Society
• /
• v.27 no.4
• /
• pp.39-45
• /
• 2020

The Cu/Cu2O/CuO photoelectrode has been successfully fabricated by Rapid Thermal Annealing technique. The structural characterization of fabricated photoelectrode was performed using X-Ray diffraction, while elemental composition of the prepared material has been checked with X-Ray Photoelectron Spectroscopy. The synthesis parameters are optimized on the basis of photoelectrochemical performance. The best photoelectrochemical performance has been observed for the Cu/Cu2O/CuO photoelectrode fabricated at 550 ℃ oxidation temperature and oxidation time of 50 seconds with highest photocurrent density of -3 mA/㎠ at -0.13 V vs. RHE.

• Korean Journal of Materials Research
• /
• v.25 no.4
• /
• pp.202-208
• /
• 2015

Alumina dispersion strengthening copper(ADSC) alloy has great potential for use in many industrial applications such as contact supports, frictional break parts, electrode materials for lead wires, and spot welding with relatively high strength and good conductivity. In this study, we investigated the oxidation behavior of ADSC alloys. These alloys were fabricated in forms of plate and round type samples by surface oxidation reaction using Cu-0.8Al, Cu-0.4Al-0.4Ti, and Cu-0.6Al-0.4Ti(wt%) alloys. The alloys were oxidized at $980^{\circ}C$ for 1 h, 2 h, and 4 h in ambient atmosphere. The microstructure was observed with an optical microscope(OM) and a scanning electron microscope(SEM) equipped with energy-dispersive X-ray spectroscopy(EDS). Characterization of alumina was carried out using a 200 kV field-emission transmission electron microscope(TEM). As a result, various oxides including Ti were formed in the oxidation layer, in addition to ${\gamma}$-alumina. The thickness of the oxidation layer increased with Ti addition to the Cu-Al alloy and with the oxidation time. The corrected diffusion equation for the plate and round type samples showed different oxidation layer thickness under the same conditions. Diffusion length of the round type specimen had a value higher than that of its plate counterpart because the oxygen concentration per unit area of the round type specimen was higher than that of the plate type specimen at the same diffusion depth.