• Journal of environmental and Sanitary engineering
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• v.15 no.4
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• pp.44-51
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• 2000

The reactivity of a range of volatile organic compounds with differing functional groups observed over 0.5% $Pt/{\gamma}-Al_2O_3$ catalyst. In general, the reactivity pattern observed was alcohols > aromatics > ketones > cycloalkane > alkanes. The deep conversion was increased as reaction temperature was increased. A correlation was found between the reactivity of the individual and the strength of the weakest C-Hbond in structure. The conversion of volatile organic compounds increases in order methanol > benzene > cyclohexane > MEK > n-hexane. That is the effect of differences in total dissociation energy. An apparent zeroth-order kinetics with respect to inlet concentration have been observed. A simple multicomponent model based on two-stage redox model made reasonably good predictions of conversion over the range of parameters studied. thus, the catalytic process was suggested as the new VOCs control technology.

• Journal of environmental and Sanitary engineering
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• v.16 no.1
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• pp.66-71
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• 2001

The objective of this study was to depict the kinetic behavior of the platinum catalyst for the deep oxidation of aromatic solvents and their binary mixtures. The oxidation kinetics of aromatic solvents, which were benzene, toluene and m-xylene, was studied on a 0.5% $Pt/{\gamma}-Al_2O_3$ catalyst. Deep oxidation of binary mixtures, which were 1:1 in volume, was carried out and the inlet concentration was controlled in the range of 133 and 333ppmv. An approach based on the two-stage redox model was used to analysis the results. The deep oxidation conversion of aromatic solvents was inversely proportional to inlet concentration in plug flow reactor. This trend is due to the zeroth-order kinetics with respect to inlet concentration. The kinetic parameters of multicomponent model were independently evaluated from the single compound oxidation experiments. A simple multicomponent model based on two-stage redox rate model made reasonably good predictions of conversion over the range of parameters studied.

• Bulletin of the Korean Chemical Society
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• v.19 no.7
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• pp.733-737
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• 1998

Using an atom superposition and electron delocalization molecular orbital (ASED-MO) method, we have compared adsorption properties of adsorbates on the Pt(Ill) surface with the Pt(lll)/γ-Al203 surface in the ethylene hydrogenation reaction. In two-layer thick model systems, the calculated activation energy of the hydrogenation by the surface platinum hydride is equal to the energy by the hydride over supported platinum/γ-alumina. The transition structure on platinum is very close to the structure on the supported platinum/γ-alumina surface. Hydrogenation by the surface hydride on platinum can take place easily because the activation energy is about 0.5 eV less than hydrogenation by ethylidene. On supported platinum/,y-alumina the activation energy of the hydride mechanism is about 0.61 eV less than that of ethylidene mechanism. In one-layer thick model systems, the activation energy of hydrogenation by ethylidene is about 0.13 eV less than the activation energy of hydride reaction. The calculated activation energy by the hydride over the supported platinum y-alumina is 0. 24 eV higher than the platinum surface. We have found from this result that the catalytic properties of one-layer thick model systems have been influenced by the support but the two-layer thick model systems have not been influenced by the support.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1638-1649
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• 2019

Top soil samples across the state of Kuwait numering ninety were collected and analysed using gamma-ray spectrometry, to evaluate the elemental concentration of $^{238}U$, $^{232}Th$ and $^{40}K$ and their depletion/enrichment. Results of elemental concentration ranges from 0.48 to 2.61 mg/kg, 0.87-5.23 mg/kg, and 0.24-2.23%, with a mean values of 1.39 mg/kg, 3.47 mg/kg, and 1.18%, for the $^{238}U$, $^{232}Th$ and $^{40}K$, respectively. Further analysis was conducted amongst the five identified soil types, i.e. Aquisalids (S1), Calcigypsids (S2), Petrocalcids (S3), Petrogypsids (S4), and torripsamment (S5). The highest radioactivity concentrations from both uranium and thorium were recorded in the S2 (Calcigypsids) soil, with a value of 1.71 (mg/kg) and 4.45 (mg/kg), respectively. Minimum and maximum values of $^{40}K$ are 1.1(%) and 1.27(%) and is prevalent in Aquisalids (S1) and Petrocalcids (S3) soil types, respectively. Ratios of elemental concentration for $^{232}Th/^{238}U$, $^{40}K/^{238}U$, $^{40}K/^{232}Th$ across the soil types are 2.53, 0.09 and 0.03, with a correlation coefficient of 0.92, 0.34, and 0.38, respectively. A progressively higher $^{232}Th/^{238}U$ ratio is observed moving south-wards, indicating lower $^{238}U$ content in soils from the south relative to the northern part. Overall results indicate Kuwait to be relatively an area with low level of natural radioactivity.

• Journal of Environmental Health Sciences
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• v.49 no.5
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• pp.251-261
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• 2023

Background: This paper deals with the study of natural radioactivity in rocks from Ogun State in Southwestern Nigeria. The aim is to determine radiation emissions from rocks in order to estimate radiation hazard indices. Objectives: The following objectives were targeted: 1. To determine radiation emissions from each type of rocks; 2. To estimate radiation hazard indices based on the rocks; 3. To correlate the activity concentrations of radionuclides with major oxides. Methods: The samples were analyzed using a NaI (Tl) gamma ray spectrometric detector and PerkinElmer AAnalyst 400 AAS spectrometer. Results: The activity of ⁴⁰K, ²²⁶Ra, and ²³²Th were found in order of decreasing magnitude from pegmatite>granite>migmatite. In contrast, lower concentrations were found in shale, phosphate, clay stone, sandstone and limestone. The mean absorbed doses were 125±23 nGyh^-1 (migmatite), 74±13 nGy/h (granite), 72±13 nGyh^-1 (pegmatite), 64±09 nGyh^-1 (quartzite), 45±16 nGyh^-1 (shale), 41±09 nGyh^-1 (limestone), 41±11 nGyh^-1 (clay stone), 24±03 nGyh^-1 (phosphate), and 21±10 nGyh^-1 (sandstone). The outdoor effective dose rates in all rock samples were slightly higher than the world average dose value of 0.34 mSvy^-1. The percentage composition of SiO₂ in the rock samples was above 50 wt% except for in the limestone, shale and phosphate. Al₂O₃ ranged from 4.10~21.24 wt%, Fe₂O₃ from 0.39~7.5 wt%, and CaO from 0.09-46.6 wt%. In addition, Na₂O and K₂O were present in at least 5 wt%. Other major oxides, including TiO₂, P₂O₅, K₂O, MnO, MgO and Na₂O were depleted. Conclusions: The findings suggest that Ogun State may be described as a region with elevated background radiation. It is recommended that houses should be constructed with good cross ventilation and residences should use home radiation monitoring instruments to monitor radon emanating from walls.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.687-693
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• 2004

Composite membranes with a titania layer were prepared by soaking-rolling method with the titania sol of nanoparticles formed in the sol-gel process and investigated regarding the vapor permeation of various organic mixtures. The support modification was conducted by pressing $SiO_2$ xerogel of 500 nm in particle size under 10 MPa on the surface of a porous stainless steel (SUS) substrate and designed the multi-layered structure by coating the intermediate layer of ${\gamma}-Al_2O_3$. Microstructure of titania membrane was affected by heat-treatment and synthesis conditions of precursor sol, and titania formed at calcination temperature of 300$^{\circ}C$ with sol of [$H^+$]/[TIP]=0.3 possessed surface area of 210 $m^2$/g, average pore size of 1.25 nm. The titania composite membrane showed high $H_2/N_2$ selectivity and water/ethanol selectivity as 25-30 and 50-100, respectively. As a result of vapor permeation for water-alcohol and alcohol-alcohol mixture, titania composite membrane showed water-permselective and molecular-sieve permeation behavior. However, water/methanol selectivity of the membrane was very low because of chemical affinity of permeants for the membrane by similar physicochemical properties of water and methanol.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.103-111
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• 2018

A plasma-catalytic combined process was used as an attempt to improve the conversion efficiency of nitrogen oxides ($NO_x$) over a wide temperature range ($150{\sim}500^{\circ}C$) to cope with the exhaust gas whose temperature varies greatly. Since the catalytic $NO_x$ reduction is effective at high temperatures where the activity of the catalyst itself is high, the $NO_x$ reduction was carried out without plasma generation in the high temperature region. On the other hand, in the low temperature region, the plasma was created in the catalyst bed to make up for the decreased catalytic activity, thereby increasing the $NO_x$ conversion efficiency. Effects of the types of catalysts, the reaction temperature, the concentration of the reducing agent (n-heptane), and the energy density on $NO_x$ conversion efficiency were examined. As a result of comparative analysis of various catalysts, the catalytic $NO_x$ conversion efficiency in the high temperature region was the highest in the case of the $Ag-Zn/{\gamma}-Al_2O_3$ catalyst of more than 90%. In the low temperature region, $NO_x$ was hardly removed by the hydrocarbon selective reduction process, but when the plasma was generated in the catalyst bed, the $NO_x$ conversion sharply increased to about 90%. The $NO_x$ conversion can be maintained high at temperatures of $150{\sim}500^{\circ}C$ by the combination of plasma in accordance with the temperature change of the exhaust gas.

• Plant Biotechnology Reports
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• v.5 no.3
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• pp.225-234
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• 2011

Arabidopsis mutants with T-DNA insertion in seven calmodulin genes (CAM) were used to determine the specific role of CAM in the tolerance of plants to oxidative stress induced by paraquat and hydrogen peroxide ($H_2O_2$) treatments. Arabidopsis calmodulin mutants (cam) were screened for seedling growth, seed germination, induced oxidative damage, and levels of ${\gamma}$-aminobutyric acid (GABA) shunt metabolites. Only the cam5-4 and cam6-1 mutants exhibited an increased sensitivity to paraquat and $H_2O_2$ during seed germination and seedling growth. In response to treatments with $3{\mu}M$ paraquat and 1 mM $H_2O_2$, only the cam5-4, cam6-1 mutants showed significant changes in malonaldehyde (MDA) levels in root and shoot tissues, with highly increased levels of MDA. In terms of the GABA shunt metabolites, GABA was significantly elevated in root and shoot tissues in response to the paraquat treatments in comparison to alanine and glutamate, while the levels of all shunt metabolites increased in root tissue but not in the shoot tissue following the $H_2O_2$ treatments. GABA, alanine and glutamate levels were significantly increased in root and shoot of the cam1, cam4, cam5-4, and cam6-1 mutants in response to paraquat (0.5, 1 and $3{\mu}M$), while they were increased only in the root tissue of the cam1, cam4, cam5-4, and cam6-1 mutants in response to $H_2O_2$ (200 and $500{\mu}M$, 1 mM). These data show that the cam5-4 and cam6-1 mutants were sensitive to the induced oxidative stress treatments in terms of seed germination, seedling growth, and oxidative damage. The accumulation of GABA shunt metabolites as a consequence of the induced oxidative stress treatments (paraquat and $H_2O_2$ treatments) suggests that the GABA shunt pathway and the accumulation of GABA metabolites may contribute in antioxidant machinery associated with reactive oxygen species and in the acquisition of tolerance in response to induced oxidative stress in Arabidopsis seedlings.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.235-235
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• 2017

Chromium (Cr) toxicity is hazardous to the seed germination, growth, and development of plants. ${\gamma}$-Aminobutyric acid (GABA) is a non-protein amino acid and is involved in stress tolerance in plants. To investigate the effects of GABA in alleviating Cr toxicity, we treated eight-d-old mustard (Brassica juncea L.) seedlings with Cr (0.15 mM and 0.3 mM $K_2CrO_4$, 5 days) alone and in combination with GABA ($125{\mu}M$) in a semi-hydroponic medium. The roots and shoots of the seedlings accumulated Cr in a dose-dependent manner, which led to an increase in oxidative damage [lipid peroxidation; hydrogen peroxide ($H_2O_2$) content; superoxide ($O{_2}^{{\cdot}-}$) generation; lipoxygenase (LOX) activity], MG content, and disrupted antioxidant defense and glyoxalase systems. Chromium stress also reduced growth, leaf relative water content (RWC), and chlorophyll (chl) content but increased phytochelatin (PC) and proline (Pro) content. Furthermore, supplementing the Cr-treated seedlings with GABA reduced Cr uptake and upregulated the non-enzymatic antioxidants (ascorbate, AsA; glutathione, GSH) and the activities of the enzymatic antioxidants including ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione peroxidase (GPX), superoxide dismutase (SOD), catalase (CAT), glyoxalase I (Gly I), and glyoxalase II (Gly II), and finally reduced oxidative damage. Adding GABA also increased leaf RWC and chl content, decreased Pro and PC content, and restored plant growth. These findings shed light on the effect of GABA in improving the physiological mechanisms of mustard seedlings in response to Cr stress.

• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.20-28
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• 2015

This work investigated the size and shape effect of ${\gamma}$-alumina-supported metal oxides on the hydrocarbon selective catalytic reduction of nitrogen oxides. Several metal oxides including Ag, Cu and Ru were used as the catalysts, and n-heptane as the reducing agent. For the Ag/${\gamma}$-alumina catalyst, the $NO_x$ reduction efficiency in the range of $250{\sim}400^{\circ}C$ increased as the size of Ag decreased (20 nm>50 nm>80 nm). The shape effect of metal oxides on the $NO_x$ reduction was examined with spherical- and wire-shape nanoparticles. Under identical condition, higher catalytic activity for $NO_x$ reduction was observed with Ag and Cu wires than with the spheres, while spherical- and wire-shape Ru exhibited similar $NO_x$ reduction efficiency to each other. Among the metal oxides examined, the best catalytic activity for $NO_x$ reduction was obtained with Ag wire, showing almost complete $NO_x$ removal at a temperature of $300^{\circ}C$. For Cu and Ru catalysts, considerable amount of NO was oxidized to $NO_2$, rather than reduced to $N_2$, leading to lower $NO_x$ reduction efficiency.