• Analytical Science and Technology
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• v.19 no.4
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• pp.285-289
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• 2006

In this study, the effect of an acidic treatment on granular activated carbon (GAC) and activated carbon fibers (ACF) was investigated for a $Pb^{2+}$ and $Ni^{2+}$ ion adsorption. 1.0 M nitric acid solution was used as the acid solution for the surface treatment. Surface properties of the GAC and ACF were characterized by the pH, elemental analysis and pHpzc (pH of the point of zero charge). Their specific surface area and the pore structure were also evaluated by the nitrogen adsorption data at 77K. As a result, the acidic treatment led to an increase of the oxygen-containing functional groups. Furthermore, the adsorption capacity of the acid-treated GAC and ACF was improved in the order of acidic-ACF > untreated-ACF > acidic-GAC > untreated-GAC, though the decrease in specific surface area induced by a pore blocking of the functional groups was observed.

• Clean Technology
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• v.30 no.1
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• pp.55-61
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• 2024

Efforts are actively underway to address the issues related to the high cost of Pt-based catalysts for oxygen reduction reactions by designing high-performance Pt-based alloys through the control of their nanostructures. In this study, a method was proposed to control the nanostructure of Pt-based alloys, either hollow or core-shell, by adjusting the pH of the solution during the galvanic replacement reaction between the carbon-supported nickel-nickel nitride composite and the Pt ions. The physical characteristics, including the state, quantity, and morphology of the metal particles under different preparation conditions, were evaluated through X-ray diffraction, transmission electron microscopy, and inductively coupled plasma. When the prepared catalysts were employed for the oxygen reduction reaction, they exhibited an improvement in area specific-activity compared to a commercial Pt/C, with a 1.7 and 1.9-fold enhancement for the hollow and core-shell structured catalysts, respectively.

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.157-163
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• 2004

Nitrogen ion implantation and ion plating techniques were applied for improvement of the wear resistance of metallic implant materials. In this work, the wear dissolution behaviour of a nitrogen ion implanted super stainless steel (S.S.S, 22Cr-20Ni-6Mo-0.25N) was compared with those of S.S.S, 316L SS and TiN coated 316L SS. The amounts of Cr and Ni ions worn-out from the specimens were Investigated using an electrothermal atomic absorption spectrometry. Furthermore, the Ti(Grade 2) disks were coated with TiN, ZrN and TiCN by use of low temperature arc vapor deposition and the wear resistance of the coating layers was compared with that of titanium. The chemical compositions of the nitrogen ion implanted and nitride coated layers were examined with a scanting auger electron spectroscopy. It wat observed that the metal ions released from the nitrogen ion implanted S.S.S surface were significantly reduced. From the results obtained, it was shown that the nitrogen ion implanted zone obtained with 100 KeV ion energy was easily removed within 200,000 revolutions from a wear dissolution testing under a similar load condition when applied to artificial hip joint. The remarkable improvement in wear resistance weir confirmed by the nitrides coated Ti materials and the wear properties differ greatly according to the chemical composition of the coating layers. for specimens with the same coating thickness of about 3$\mu\textrm{m}$, TiCN coated Ti showed the highest wear resistance. However, after removing the coating layers, the wear rates of all nitrides coated Ti reverted to their normal rates of below 10,000 revolutions from Ti-disk-on-disk wear testing under the same load condition. From the results obtained, it is suggested that the insufficient depth of the 100 Kel N$\^$＋/ ion implanted zone and of the nitrides coated layers of 3$\mu\textrm{m}$ are subject to restriction when used as frictional parts of load bearing implants.

• Journal of the Korean Chemical Society
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• v.37 no.8
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• pp.723-729
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• 1993

Cu(II) ion-responsive chemically modifed electrodes (CMEs) were constructed by incorporating 1-(2-pyridylazo)-2-naphthol (PAN) into a conventional carbon-paste mixture of graphite powder and Nujol oil. Cu(II) ion was chemically deposited on the surface of the PAN-chemically modified electrode in the absence of an applied potential by immersion of the electrode in a buffer solution (pH 3.2) containing Cu(II) ion, and then reduced at a constant potential in 0.1 M KNO$_3$. And a well-defined voltammetric peak could be obtained by scanning the potential to the positive direction. The electrode surface could be regenerated with exposure to acid solution and reused for the determination of Cu(II) ion. In 5 deposition / measurement / regeneration cycles, the response could be reproduced with 6.1${\%}$ relative standard deviation. In case of using the differential pulse voltammetry, the calibration curve for Cu(II) was linear over the range of 2.0 ${times}$ 10$^{-7}$ ∼ 1.0 ${times}$ 10$^{-6}$ M. And the detection limit was 6.0 ${times}$ 10$^{-8}$ M. Studies of the effect of diverse ions showed that Co, Ni, Zn, Pb, Mg and Ag ions added 10 times more than Cu(II) ion did not influence on the determination of Cu(II) ion, except EDTA and oxalate ions.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1669-1674
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• 2012

A novel superabsorbent composite was prepared by intercalation polymerization of acrylic acid (AA) and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) in the presence of montmorillonite (MMT), using ammonium persulfate (APS) as an initiator and $N,N'$-methylenebisacrylamide (MBA) as a cross linker. The superabsorbent composite was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Maximum absorbency of the composite in distilled water and 0.9% sodium chloride solution was 722 and 108 g/g, respectively. The composite was used for removal of heavy metal ions from aqueous solutions. Maximum amount of adsorption for $Ni^{2+}$, $Cu^{2+}$ and $Pb^{2+}$ was 211.0, 159.6 and 1646.0 mg/g, respectively, and the adsorption was in accordance with both Langmuir and Freundlich model. The composite could be regenerated and reused in wastewater treatment.

• Journal of Applied Biological Chemistry
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• v.51 no.3
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• pp.95-101
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• 2008

The gene encoding a putative esterase of Xanthomonas oryzae pv. oryzae was cloned using PCR technique. The gene was expressed with His6 tag in E. coli. One-step purification of the recombinant esterase with Ni-NTA resin resulted in one band by SDS-PAGE analysis. The purified enzyme showed a molecular weight of 30 kDa, as expected, therefore the enzyme was a mononer. The enzyme was the most active toward p-nitrophenyl (p-NP) acetate and p-NP-butyrate to a lesser extent. However, the enzyme could not hydrolyze p-NP-myristate, palmitate, and stearate. Therefore, the enzyme is considered as an esterase, very different from lipase. The purified esterase had optimal pH at around 8.0 and was stable in a broad range of pH values. The optimal temperature ranged from 30 to $40^{\circ}C$, and the residual activity observed after heat treatment at $55^{\circ}C$ for 20 min was 72 % of the initial activity. The activity was inhibited by the presence of copper and cobalt ions.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.6
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• pp.475-486
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• 1997

The characteristics of atmospheric aerosols were investigated as a function of particle size and water solubility. The atmospheric aerosols were sampled with classifying into 12 size ranges by the use of Andersen low-pressure impactor. Collected aerosol particles were extracted by ultrapure water and filtered to be separated into water-soluble and insoluble components. The concentrations 12 elements in both components were determined by PIXE analysis. And the concentrations of 8 ions in the soluble component were analyzed by ion chromatography. In general, the mass size distribution of particulate matter was represented as a bimodal distribution. The mass size distributions of S$(SO_4^{2-}), K(K^+), Zn and NH_4^+$ skewed to the smaller size range and those of Si, Ca$(Ca^{2+}), Fe, Na^+ and Mg^{2+}$ skewed to the larger size range. They had roughly one peak in the fine and coarse particle region,respectively. On the other hand, the mass size distribution of Ti, Mn, Ni, Cu, $Cl^- and NO_3^-$ were represented as the bimodal distribution. Fe and Si in the aerosol particles extracted into pure water are existing in high insoluble state. Conversely, almost the whole of S is dissolved in water.

• KSBB Journal
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• v.11 no.2
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• pp.173-180
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• 1996

The contamination of the environment by heavy metals results in a serious public health problem due to the toxicity of those pollutants even at low concentrations. Microorganisms may be used to remediate wastewaters contamlialtd with heavy metals. The waste S. cerevisiae is an inexpensive readily available source of biomass for bioremediation of wastewater. S. cerevisiae was investigated for their ability to absorb Pb. The crushed biomass of S. cerevisiae exhibited higher Pb uptake capacity than the living S. cerevisiae and the sterilized S. cerevisiae. At the same metal concentration, metal uptake per unit concentration or adsorbent decreased when the biomass concentration rises. The order of the biosorption capacity of the living S. cerevisiae was Pb>Cu>Cd=Co>Cr. When S. cerevisiae was pretreated with 0.1 M NaOH, Pb uptake was increased by 150 percent and 0.1 M HC1, 0.1 M $H_2S_O4$ solutions were efficient in the desorption of Pb. The sorption equilibrium of Pb ions can be described by the Freundlich and Langmuir models.

• BMB Reports
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• v.43 no.4
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• pp.284-290
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• 2010

Replication of positive-strand RNA virus is mediated by a virus-encoded RNA-dependent RNA polymerase (RdRp). To study the replication of Ectropis obliqua virus (EoV), a newly identified insect virus belonging to the family Iflaviradae, we expressed the RNA polymerase domain in Escherichia coli and purified it on a Ni-chelating HisTrap affinity column. It is demonstrated that EoV RdRp initiated RNA synthesis in a primer and poly (A)-dependent manner in vitro. Furthermore, the effect of primer concentration, temperature, metal ions ($Mg^{2+}$, $Mn^{2+}$, and $K^+$) on enzymatic activity were determined. Our study represented a first step towards understanding the mechanism of EoV replication.

• BMB Reports
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• v.28 no.2
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• pp.170-176
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• 1995

Rhodanese from mouse liver was purified to near homogeneity by ammonium sulfate precipitation, CM-Sephadex ion exchange, hydroxyapatite and Sephacryl S-200-HR gel filtration chromatographies with a purification of 776 folds. The molecular weight was determined by Sephadex G-150 gel filtration and found to be 34.8 KDa. SOS-PAGE showed molecular weight 34 KDa and two identical subunits splitting by aging for 3 weeks at $-70^{\circ}C$ the molecular weight of which was 17 KDa. The optimal pH of enzyme activity was 9.4 and the pI value of the enzyme was 6.6. Rhodanese showed the optimal reaction temperature of $25^{\circ}C$ and near linear increasing pattern until 10 min. incubation. $K_m$ values of rhodanese for KCN and $Na_{2}S_{2}O_{3}$ as substrates were 12.5 mM and 8.3 mM, respectively. Rhodanese activity was inhibited by more than 70% at a concentration of 100 ${\mu}M$ of $Ni^{2+}$, $Zn^{2+}$, $Cd^{2+}$, $Hg^{2+}$ and $Cu^{2+}$. Other metal ions, such as $Mn^{2+}$, $Mg^{2-}$, $Ca^{2+}$, and $Fe^{2+}$ showed no effect on rhodanese activity.