• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.370-374
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• 2013

The effects of zinc chloride addition on pore development of porous carbon nanofibers prepared by polyacrylonitrile (PAN)/ N,N'-dimethylformamide (DMF) (10 wt%) electrospinning were investigated. The change of morphological and structural modification by zinc chloride activation was investigated by a scanning electron microscopy (SEM) analysis. $N_2$ adsorption isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller (BET) and Horvath-Kawazoe (H-K) equations, and the curves showed the Type I mode in the International Union of Pore and Applied Chemistry (IUPAC) classification, indicating that lots of micropores exist in the sample. In addition, specific surface areas and total pore volumes of porous carbons prepared by the zinc chloride activation were determined as 600~980 $m^2/g$ and 0.24~0.40 $cm^3/g$, respectively. As experimental results, many holes or demolished structures were found on the fiber surfaces after the zinc chloride activation as confirmed by a SEM analysis. It was also observed that various pore sizes were found to be depended on the adding content of zinc chloride in PAN/DMF solution in this system.

• Korean Journal of Environmental Agriculture
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• v.37 no.1
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• pp.66-72
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• 2018

BACKGROUND: Constructed wetlands are low-cost alternatives for treating domestics sewage. However, previous study has reported that the removal of phosphorus in constructed wetlands was limited. Therefore, a new alternative was needed to extend the life of the constructed wetlands. The purpose of this study was to evaluate the effect of total phosphorus removal by oyster shell on longevity of constructed wetlands for treating domestic sewage. METHODS AND RESULTS: The changes of total phosphorus concentration and treatment efficiency in two constructed wetlands (CWs) classified as system A (coarse sand 100%) and system B (coarse sand 90%+oyster shell 10%) were investigated for 6 years. The actual saturation time of total phosphorus in the systems A and B was estimated to be longer than that of theoretical saturation by adsorption isotherm experiment. In particular, the saturation pattern of phosphorus in system A was maintained at a certain concentration level in the initial stage of operation, and finally saturation was reached as the saturation gradually progressed from the breaking point. In system B, the saturation period of phosphorus was prolonged as compared with system A due to the addition of oyster shells. CONCLUSION: Our results suggest that the longevity of the constructed wetlands can be extended due to the phosphorus saturation by adding the oyster shells to the coarse sands in constructed wetlands.

• 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.

• Membrane Journal
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• v.28 no.4
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• pp.221-232
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• 2018

The silica containing carbon ($C-SiO_2$) membranes were fabricated using poly(imide siloxane)(Si-PI) and polyvinylpyrrolidone (PVP) blended polymer. The characteristics of porous carbon structures prepared by the pyrolysis of polymer blends were related with the micro-phase separation behaviors of the two polymers. The glass transition temperatures ($T_g$) of the mixed polymer blends of Si-PI and PVP were observed with a single $T_g$ using differential scanning calorimetry. Furthermore, the nitrogen adsorption isotherms of the $C-SiO_2$ membranes were investigated to define the characteristics of porous carbon structures. The $C-SiO_2$ membranes derived from Si-PI/PVP showed the type IV isotherm and possessed the hysteresis loop, which was associated with the mesoporous carbon structures. For the molecular sieving probe, the $C-SiO_2$ membranes were prepared with the ratio of Si-PI/PVP and the pyrolysis conditions, such as the pyrolysis temperature and the isothermal times. Consequently, the $C-SiO_2$ membranes prepared by the pyrolysis of Si-PI/PVP at $550^{\circ}C$ with the isothermal time of 120 min showed the $O_2$ permeability of 820 Barrer ($1{\times}10^{-10}cm^3(STP)cm/cm^2{\cdot}s{\cdot}cmHg$) and $O_2/N_2$ selectivity of 14.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.204-210
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• 1997

Zeolite 4A-impregnated complex molecular sieve was prepared by hydrothermal reaction after aluminosilicate gel was penetrated into the pore of activated carbon granule. The crystals of zeolite 4A mainly were formed in the macropore of activated carbon, and their average diameter is $0.8{\mu}m$. The pore volume of activated carbon granule is $0.67m{\ell}/g$, and the pore volume of the sample including 21.6wt% of zeolite 4A crystal is $0.41m{\ell}/g$ decreasing the pore volume by 40% due to the crystallization of zeolite 4A crystals on the internal surface of activated carbon. The calcium ion exchange capacity of zeolite 4A-impregnated sample is 320mg $CaCO_3/g$ zeolite, and this value is almost the same as that of zeolite 4A powder. The crystal of zeolite 4A was not separated from the support of activated carbon granule in the course of ultrasonic dispersion. The adsorption isotherm of water on zeolite 4A-impregnated sample shows the intermediate shape between types, I and III. In addition, zeolite 4A-impregnated sample shows the hydrophilic and hydrophobic properties simultaneously.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.61-68
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• 2009

The main objective of this study was to examine the removal of heavy metals from water by inflated vermiculites. The component of vermiculites was analyzed by XRF, and the concentration of metal ion was measured by ICP-AES. Serial batch kinetic tests and batch sorption tests were conducted to determine the removal characteristics for heavy metals in aqueous solutions. As a result, solution pH values of tests with the inflated vermiculites generally increased and then stabilized. Equilibrium pHs were generally established within 5 hrs. In addition, removal rates of inflated vermiculites were tested at the initial concentration of 3 mg/L. As a result, at equilibrium concentration, except for chromium (36.23%), Most of the heavy metals were effectively removed (96.08~98.54%). Finally, sorption data were correlated with both Langmuir and Freundlich isotherms. The Qmax obtained from Langmuir isotherm were determined to Pb $725.4mg\;kg^{-1}$, Cd $568.8mg\;kg^{-1}$, Zn $540.2mg\;kg^{-1}$, Cu $457.2mg\;kg^{-1}$ Cr $0.9mg\;kg^{-1}$ respectively. The results of the study indicate that inflated vermiculites can be properly used as an adsorbent for various heavy metals because of its outstanding removal rate.

• Korean Journal of Environmental Agriculture
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• v.22 no.4
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• pp.284-289
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• 2003

Titanium mesoporous materials have received increasing attention as a new photocatalyst in the field for photocatalytic degradation of organic compounds. The photocatalytic degradation of chlorothalonil by mesoporous titanium oxo-phoswhate (Ti-MCM) was investigated in aqueous suspension for comparison with $TiO_2$, (Degussa, P25) using as an effective photocatalyst of organic pollutants. Mesoporous form of titanium Phosphate has been prepared by reaction of sulfuric acid and titanium isopropoxide in the presence or n-hexadecyltrimethylammonium bromide. The XRD patterns of Ti-MCM are hexagonal phases with d-spacings of 4.1 nm. Its adsorption isotherm for chlorothalonil reached at reaction equilibrium within 60 min under dark condition with 28% degradation efficiency. The degradation ratio of chlorothalonil after 9 hours under the UV radiation condition (254 nm) exhibited 100% by Ti-MCM and 88% by $TiO_2$. However, these degradation kinetics in static state showed a slow tendency compared to that of stirred state because of a low contact between titanium matrices and chlorothalonil. Also, degradation efficiency of chlorothalonil was increased with decreasing initial concentration and with increasing pH of solution. As results of this study, it was clear that mesoporous titanium oxo-phosphate with high surface area and crystallinity could be used to photo- catalytic degradation of various organic pollutants.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.737-741
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• 2005

In this study, the effect of copper content on the NO removal efficiency by Cu/MCM-41 has been investigated. MCM-41 was prepared by hydrothermal synthesis using a gel mixture of colloidal silica solution and cetyltrimethylammonium. Cu/MCM-41 was manufactured with copper content (5, 10, 20, and 40%) in Cu(II) acetylacetonate. The surface properties of MCM-41 were investigated by using pH, XRD, and FT-IR analyses. $N_2/77K$ adsorption isotherm characteristics, including the specific surface area and micropore volume were studied by BET's equation and Boer's t-plot methods. NO removal efficiency was confirmed by gas chromatography technique. From the experimental results, the MCM-41 was analyzed to have the surface functional groups of Si-OH and Si-O-Si and the characteristic diffraction lines (100), (110), (200), and (210) corresponding to a hexagonal arrangement structure. The copper content supported on MCM-41 appeared to increase the NO removal efficiency in spite of decreasing the specific surface areas or micropore volumes. Consequently, it was found that the copper content in Cu/MCM-41 played an important role in improving the NO removal efficiency, which was mainly attributed to the catalytic reactions.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.611-619
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• 2019

This study was carried out to investigate fuel decomposition characteristics and coke formation according to types of endothermic fuels and methods of catalyst molding. Methylcyclohexane (MCH), n-dodecane, and exo-tetrahydrodipentadiene (exo-THDCP) were used as the endothermic fuels. As a catalyst, USY720 supported with platinum was used. It was manufactured by only using pressure to disk-type, or pelletized with a binder and a silica solution. The characteristics of the catalysts according to the molding method were analyzed by X-ray diffraction analysis, scanning electron microscopy, nitrogen adsorption-desorption isotherm, and ammonia temperature programmed desorption analysis. The reaction was carried out under conditions of high temperature and high pressure ($500^{\circ}C$, 50 bar) in which the fuel could exist in a supercritical state. The product was analyzed by gas chromatograph/mass spectrometer and the coke produced by the catalyst was analyzed by thermogravimetric analyzer. After the reaction, the composition of the products varied greatly depending on the structure of the fuel. In addition, the crystallinity and surface properties of the catalysts were not changed by the method of catalyst molding, but the changes of the acid sites and the pore characteristics were observed, which resulted in changes in the amount and composition of products and coke.

• Clean Technology
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• v.25 no.1
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• pp.91-97
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• 2019

Oxidative desulfurization (ODS) has received much attention in recent years because refractory sulfur compounds such as dibenzothiophenes can be oxidized selectively to their corresponding sulfoxides and sulfones, and these products can be removed by extraction and adsorption. In this work, The oxidative desulfurization of marine diesel fuel was performed in a batch reactor with hydrogen peroxide ($H_2O_2$) in the presence of various supported heteropoly acid catalysts. The catalysts were characterized by XRD, XRF, XPS and nitrogen adsorption isotherm techniques. Based on the sulfur removal efficiency of promising silica supported heteropoly acid catalysts, the ranking of catalytic activity was: $30\;H_3PW_{12}/SiO_2$ > $30\;H_3PMo_{12}/SiO_2$ > $30\;H_4SiW_{12}/SiO_2$, which appears to be related with their intrinsic acid strength. The $30\;H_3PW_{12}/SiO_2$ catalyst showed the highest initial sulfur removal efficiency of about 66% under reaction conditions of $30^{\circ}C$, $0.025g\;mL^{-1}$ (cat./oil), 1 h reaction time. However, through the recycle test of the $H_3PW_{12}/SiO_2$ catalyst, significant deactivation was observed, which was attributed to the elution of the active component $H_3PW_{12}$. By introducing cesium cation ($Cs^+$) into the $H_3PW_{12}/SiO_2$ catalyst, the stability of the catalyst was improved with changing the solubility, and the $Cs^+$ ion exchanged catalyst could be recycled for at least five times without severe elution.