• Journal of the Korean GEO-environmental Society
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• v.10 no.7
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• pp.25-32
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• 2009

The main objective of this study was to examine the removal properties of Cu from water by inflated vermiculites. The component of vermiculites was analyzed by XRF and the concentration of Copper ion was measured by UV-VIS. Serial batch Kinetic tests and batch sorption tests were conducted to determine the removal characteristics for Cu in aqueous solutions. The result shows that removal rate, $K_{obs}$, of Cu are 0.73, 1.52, and 1.71 for initial pH 3, pH 4, pH 5, respectively, and are 3.19, 1.90, and 0.73 for the initial concentration of $1mg\;L^{-1}$, $5mg\;L^{-1}$, $10mg\;L^{-1}$, respectively. It leads to the conclusion that the removal rates are inversely proportional to the initial Cu concentration and are increased proportionally to the initial pHs. Finally, Sorption data were correlated with both Langmuir and Freundlich isotherms. As a result, Langmuir and Freundlich models were well fitted to batch isotherm data with good values of the determination coefficient. but the determination coefficient value for the Freundlich model fit was slightly higher than that of Langmuir model (0.965 for the Freundlich model and 0.936 for the Langmuir model). Using the Langmuir model, the maximum sorption capacity ($Q_{max}$), Freundlich partition coefficient, and the numerical value of n wrer estimated as $1,250mg\;kg^{-1}$, $635.1L\;kg^{-1}$ and 1.69, respectively. These results show that the inflated vermiculites could be used as an excellent adsorbent for copper contained in various types of aqueous solutions.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.131-136
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• 2013

The aim of this study was to investigate the removal of fluoride using thermally treated pyrophyllite as adsorbent. Sorption experiments were conducted under batch conditions to examine the effects of adsorbent dose, reaction time, initial fluoride concentration and solution pH on fluoride removal. In the experiments, the pyrophyllite thermally treated at different temperatures [untreated (P-U), $400^{\circ}C$ (P-400), $600^{\circ}C$ (P-600)] were used. Results showed that the adsorption capacity was in the order of P-400 > P-U > P-600. The XRD analysis indicated that both P-U and P-400 were composed of quartz, dickite and pyrophyllite while P-600 was quartz. The BET analysis showed that the specific surface area was in the order of P-600 > P-400 > P-U. Kinetic data showed that fluoride sorption to P-400 arrived at equilibrium around 24 h. Equilibrium test demonstrated that the maximum sorption capacity of P-400 was 0.957 mg/g. In addition, fluoride removal by P-400 was not sensitive to solution pH between 4 and 10. However, fluoride removal decreased considerably at highly acidic (pH < 4) and alkaline (pH > 10) conditions. This study demonstrates that pyrophyllite could be used as a low-cost adsorbent for fluoride removal from aqueous solution.

• Clean Technology
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• v.25 no.4
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• pp.296-301
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• 2019

This study was conducted to investigate the characteristics of CO oxidation by NO poisoning in Pt/TiO₂ catalyst prepared by wet impregnation method and calcined at 400 ℃. In order to confirm the NO poisoning effect of the Pt/TiO₂ catalyst, the change of reaction activity was observed when NO was injected during the CO+O₂ reaction where it was ascertained that the CO conversion rate rapidly decreased below 200 ℃. Also, CO conversion was not observed below 125 ℃. Recovery of initial CO conversion was not verified even if NO injection was blocked at 125 ℃. Accordingly, various analyses were performed according to NO injection. First, as a result of the TPD analysis, it was confirmed that NO pre-adsorption in catalyst inhibited CO adsorption and conversion desorption from adsorbed CO to CO₂. When NO was pre-adsorbed, it was confirmed through H₂-TPR analysis that the oxygen mobility of the catalyst was reduced. In addition, it was validated through FT-IR analysis that the redox cycle (Pt²⁺→Pt⁰→Pt²⁺) of the catalyst was inhibited. Therefore, the presence of NO in the Pt/TiO₂ catalyst was considered to be a poisoning factor in the CO oxidation reaction, and it was determined that the oxygen mobility of the catalyst is required to prevent NO poisoning.

• Journal of Hydrogen and New Energy
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• v.28 no.1
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• pp.9-16
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• 2017

Hydrogen forms metal hydrides with some metals and alloys leading to solid-state storage under moderate temperature and pressure that gives them the safety advantage over the gas and liquid storage methods. However, it has disadvantages of slow hydrogen adsorption-desorption time and low thermal conductivity. To improve characteristics of metal hydrides, it is important that activation and thermal conductivity of metal hydrides are improved. In this study, we have been investigated hydrogen storage properties of Hydralloy C among Ti-Mn alloys. Also, the characteristics of activation and thermal conductivity of Hydralloy C were enhanced to improve kinetics of hydrogen adsorption-desorption. As physical activation method, PHEM (planetary high energy mill) was performed in Ar or $H_2$ atmosphere. Hydralloy C was also activated by $TiCl_3$ catalyst. To improve thermal conductivity, various types of ENG (expanded natural graphite) were used. The prepared samples were compacted at pressure of 500 bar. As a result, the activation properties of $H_2$ PHEM treated Hydralloy C was better than the other activation methods. Also, the amounts of hydrogen storage showed up to 1.6 wt%. When flake type ENG was added to Hydralloy C, thermal conductivity and hydrogen storage properties were improved.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.50-56
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• 2006

We investigated the adsorption of benzene and pyridine on $Si(5\;5\;12)-2\times1$ at 80 K by using variable-low temperature scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The benzene molecule most strongly binds to two adatoms on the D3 and D2 units in a tilted butterfly configuration, which consists of $di-\sigma$ bonds between C atoms and Si adatoms and two C=C double bonds in the benzene molecule Pyridine molecules interact with adatom(s) on the D2 and D3 units through both Si-N dative bonding and $di-\sigma$ bonds. The dative bonding through the lone pair electrons of N atom produces a vertical configuration (pyridine-like), which is more stable than $di-\sigma$ bonds $Di-\sigma$ bonds can be formed either through Si-N1 and Si-C4 or Si-C2 and Si-C5.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.4
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• pp.239-246
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• 2012

This study was performed to investigate the removal characteristics and mechanism of heavy metals using pellet-type ceramics(ZS ceramics), in which natural zeolite was mixed and calcined with converter slag. The optimal calcination temperature range was measured to be $600{\sim}800^{\circ}C$. The calcination time had little effect on the removal of heavy metal in acid wastewater. The adequate dose of ceramics was shown to be 2~5% for removal of heavy metals in acid wastewater. The maximum removal capacity of ZS ceramics for heavy metals were observed to be Al 84.7 mg/g, Cd 37.3 mg/g, Cr 81.7 mg/g, Cu 55.6 mg/g, Fe 57.2 mg/g, Mn 32.1 mg/g, Ni 38.0 mg/g, Pb 71.6 mg/g, Zn 46.3 mg/g. The pH played a pivotal role in the removal of heavy metals by ZS ceramics. The analysis results of mechanism exhibited that the ZS ceramics could act as a multi-functional ceramics for removal of heavy metals in acid wastewater by adsorption, ion-exchange, or precipitation.

• Korean journal of applied entomology
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• v.10 no.2
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• pp.77-83
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• 1971

In order to find out the decomposing factors of Sumithion in mineral diluents, the physical and chemical properties of the diluents such as talcs, bentonites, diatomaceous earth and other clay minerals was studied in relation to the decomposition rate of Sumithion in dust formulations. The total base, moisture adsorption capacity, pH, specific surface, water contents, active $Fe^{++}$, ignition loss and cation exchange capacity were analysed as the properties of mineral diluents, and these properties were correlated with the stability of Sumithion in dust formulations. And in hope of finding out the main factors among those properties of diluents, the decomposed products of Sumithion in dust formulations prepared with standard Sumithion were separated by the methods of column chromatography and investigated by thin layer chromatography. The following results were otbained; 1. The total base, moisture adsorption capacity, specific surface, water contents, active $Fe^{++}$ and cation exchange capacity of mineral diluents were found to be highly effective on the rate of decomposition of Sumithion in dust formulations. 2. Decomposed products of Sumithion in dust formulations were found to be dimethylphosphorothionate, 3-methyl-4-nitro phenol and its derivatives. And one fraction was not dissolved in n-hexane and ethylether, but was soluble in methylalcohol and ethylalcohol. 3. The moat highly correlated properties of diluents with the decomposition rate of Sumithion in dust were found to be the total base and water contents. 4. In regard to the kind of diluents, it was found that the rate of decomposition of Sumithion in dust formulations was higher in order of bentonite, diatomaceous earth, kaolin and talc.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.428-432
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• 2013

From the forest areas in Chungbuk, large amounts of wood wastes by pruning are generated, however most of them considered as by-products are not treated properly with no disposal options. In this work, among diverse wood wastes such as Quercus variabillis, Juniperus chinensis, Larix kaemoferi, and Pinus densiflora, Juniperus chinensis was found to be more effective biosorbent for the removal of lead ions than other wood wastes. Also, the enhancement of lead removal efficiency from the aqueous phase was investigated using Juniperus chinensis waste. It was observed that the optimal initial pH to increase the removal efficiency of 20 mg/L lead ions was 4.0 and the optimal dosage concentration with regard to the biosorbent for the enhanced removal of 50 mg/L lead ions was 0.6 g/100 mL. In addition, chemical treatment of Juniperus chinensis waste with sulfuric acid was required to improve the adsorption capacity for high lead concentrations (over 100 mg/L). When Juniperus chinensis waste was chemically treated with 6 M sulfuric acid, the adsorption quantities of lead ions were 180, 340, and 425 mg/g with regard to 200, 400, and 500 mg/L lead ions concentrations, respectively. These results indicate that the practical biosorbent technology developed in this study is a highly efficient method to treat the lead ion from an aqueous solution.

• Korean Journal of Materials Research
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• v.8 no.9
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• pp.837-842
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• 1998

As the size of the integrated circuit is scaled down the importance of Si cleaning has been emphasized. One of the major concerns is abut the removal of metallic impurities such as Cu and Fe on Si surface. In this study, we intentionally contaminated Cu and Fe on the Si wafers and cleaned the wafer by cleaning splits of the chemical mixture of $\textrm{H}_2\textrm{O}_2$ and HF and the combination of HF treatment with UV/$\textrm{O}_3$ treatment. The contamination level was monitored by TXRF. Surface microroughness of the Si wafers was measured by AFM. The Si wafer surface was examined by SEM. AES analysis was carried out to analyze the chemical composition of Cu impurities. The amount of Cu impurities after intentional contamination was abut the level of $\textrm{10}^{14}$ atoms/$\textrm{cm}^2$. The amount of Cu was decreased down to the level of $\textrm{10}^{10}$ atoms/$\textrm{cm}^2$ by cleaning splits. The repeated treatment exhibited better Cu removal efficiency. The surface roughness caused by contamination and removal of Cu was improved by repeated treatment of the cleaning splits. Cu were adsorbed on Si surface not in a thin film type but in a particle type and its diameter was abut 100-400${\AA}$ and its height was 30-100${\AA}$. Cu was contaminated on Si surface by chemical adsorption. In the case of Fe the contamination level was $\textrm{10}^{13}$ atoms/$\textrm{cm}^2$ and showed similar results of above Cu cleaning. Fe was contaminated on Si surface by physical adsorption and as a particle type.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.745-754
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• 2013

This study evaluated the optimal soil washing conditions for toxic metals considering the removal efficiency of toxic metals from contaminated soils as well as from soil washing effluents. In the contaminated soils, As was the major contaminant and extracted by sodium hydroxide solution better than by sulfuric acid. However, in the case of the treatment of soil washing effluents, sodium hydroxide was less effective extractant because soil organic matter extracted by sodium hydroxide prevented the solid-liquid phase separation and toxic metal removal. In the treatment of soil washing effluents with sulfuric acid, toxic metals in the effluents were mostly precipitated at the pH above 6.5. In addition, granular ferric oxide (GFO) as an adsorbent enhanced the removal of As and Pb indicating that toxic metals in the washing effluents can be removed almost completely by the use of combined adsorption-neutralization process. This study suggests that soil washing techniques for toxic metals should be optimized based on the physical and chemical properties of the contaminated soils, the nature of chemical extractant, and the removal efficiency and effectiveness of toxic metals from the soils as well as soil washing effluents.