• Korean Chemical Engineering Research
• /
• v.61 no.3
• /
• pp.426-438
• /
• 2023

Lithium-sulfur batteries, recently attracting attention as next-generation batteries, have high energy density but are limited in application due to sulfur's insulating properties, shuttle phenomenon, and volume expansion. This study used an economical and simple vacuum filtration method to prepare a freestanding electrode without a binder and collector. Carbon nanotubes (CNTs) are used to improve the electrical conductivity of sulfur, where CNT also acts as both collector and conductor. In addition, metal oxides (MO_x, M=Ni, Mg), which are easy to adsorb lithium polysulfide, are added to the CNT/S electrode to suppress the shuttle reaction in lithium-sulfur batteries, which is a result of suppressing the loss of active sulfur material due to the excellent adsorption of lithium polysulfide by metal oxides. The MO_x@CNT/S electrode exhibited higher capacity characteristics and cycle stability than the CNT/S electrode without metal oxides. Among the MO_x@CNT/S electrodes, the NiO@CNT/S electrode displayed a high discharge capacity of 780 mAh g^-1 at 1 C and an extreme capacity decrease to 134 mAh g^-1 after 200 cycles. Although the MgO@CNT/S electrode exhibited a low discharge rate of 544 mAh g^-1 in the initial cycle, it showed good cycle stability with 90% of capacity retention up to 200 cycles. Further, to achieve high capacity and cycle stability, the Ni_0.7Mg_0.3O@CNT/S electrode, mixed with Ni:Mg in the ratio of 0.7:0.3, manifested an initial discharge rate of 755 mAh g^-1 (1 C) and a capacity retention rate of more than 90% after 200 cycles. Therefore, applying binary metal oxides to CNT/S provides a freestanding electrode for developing economical and high-performance Li-S batteries, effectively improving lithium polysulfide's high capacity characteristics and dissolution.

• Resources Recycling
• /
• v.17 no.6
• /
• pp.34-42
• /
• 2008

The properties of sodium silicate solution were surveyed by using the yellow silicomolybdic method, and the formation of silica sol from sodium silicate solution and the growth of silica sol were investigated in this study. The $SiO_2$ content of 2 wt% in sodium silicate solution was proper to oxidize sodium silicate with sulfuric acid. After the removal of sodium ions in sodium silicate solution, the pH of silicate solution had to be controlled above 9 for the stabilization of silicate solution. The condensation between silicic acid species and silica nuclei surfaces has been studied at $20{\sim}80^{\circ}C$ and pH 10 in silicate solutions with silica nuclei. The reaction falls into two kinetics regimes, limited at high silicic acid species concentration by polymerization, but at lower concentration by a process whereby deposited silicic acid species condenses further to silica. The overall condensation is first-order in silicic acid species concentration, proceeded toward to pseudo equilibrium concentration, $C_x$, rather than the solubility of amorphous silica. The heat of solution of amorphous silica was 3.34 kcal/mol and exhibits an Arrhenius temperature dependence with an apparent activation energy of 3.16 kcal/mol in the range of $20{\sim}80^{\circ}C$.

• Applied Chemistry for Engineering
• /
• v.25 no.5
• /
• pp.520-525
• /
• 2014

In this paper, the effect of silane-treated silicas and epoxidized soybean oil (ESBO) addition on adhesion properties of silicas-filled epoxy adhesives was examined. The silicas were treated by ${\gamma}$-methacryloxy propyltrimethoxy silane (MPS), ${\gamma}$-glycidoxy propyl trimethoxy silane (GPS), and ${\gamma}$-mercapto propyl trimethoxy silane (MCPS). Surface and structural properties of the adhesives were determined by using scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR). The t-peel strength of the adhesives was estimated using the universal testing machine (UTM). And, the equilibrium spreading pressure, surface free energy, and specific surface area were investigated by BET methods with $N_2$/77 K adsorption. As a result, the peel strength of the adhesives was increased in the presence of silane-treated silicas in the adhesives compared to that of untreated silicas. This result indicated that the silane coupling agent played an important role in improving the dispersion of silicas in epoxy adhesives. And, the adhesives treated by MCPS were superior to the others in adhesion.

• Applied Chemistry for Engineering
• /
• v.21 no.1
• /
• pp.63-70
• /
• 2010

Transition metal based spent catalysts (Ni-Mo and Co-Mo), which were scrapped from the petrochemical industry, were reused for the removal processes of volatile organic compounds (VOCs). Especially the optimum regeneration procedures were determined using the removal efficiency of VOCs. In this work, the spent Ni-Mo and spent Co-Mo catalysts were pretreated with different physic-chemical treatment procedure: 1) acid aqueous solution, 2) alkali solution, 3) chemical agent and 4) steam. The various characterization methods of spent and its regenerated catalysts were performed using nitrogen adsorption, X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with an energy dispersive spectrometry (EDS). It was found that all spent catalysts were found to be potentially applicable catalysts for catalytic oxidation of benzene. The experimental results also indicated that among the employed physico-chemical pretreatment methods, the oxalic acid aqueous (0.1 N, $C_2H_2O_4$) pretreatment appeared to be the most efficient in increasing the catalytic activity, although the catalytic activity of spent Ni-Mo and spent Co-Mo catalysts in the oxidation of benzene were greatly dependent on the pretreatment conditions. The pretreated spent catalysts at optimum condition could be also applied for removing other aromatic compounds (Toluene/Xylene).

• Membrane Journal
• /
• v.28 no.2
• /
• pp.136-141
• /
• 2018

Carbon dioxide ($CO_2$) exists not only as a component of natural gas, biogas, and landfill gas, but also as a major combustion product of fossil fuels which leads to a major contributor to greenhouse gases. Hence it is essential to reduce or eliminate carbon dioxide ($CO_2$) in order to obtain high fuel efficiency of internal combustion engine, to prevent corrosion of gas transportation system, and to cope with climate change preemptively. In recent years, there has been a growing interest in not only conventional membrane-based separation but also new adsorbent-based separation technology. Particularly, in the case of metal-organic frameworks (MOFs), it has been received tremendous attentions due to its unique properties (eg : flexibility, gate effect or strong binding site such as open metal sites) which are different from those of typical porous adsorbents. Therefore, in this study, stereotype of two MOFs have been selected as its flexible MOFs (MIL-53) representative and numerous open metal sites MOFs (MOF-74) representative, and compared each other for $CO_2/CH_4$ separation performance. Furthermore, varying and changeable separation performance conditions depending on the temperature, pressure or samples' unique properties are discussed.

• Applied Chemistry for Engineering
• /
• v.20 no.4
• /
• pp.453-458
• /
• 2009

Iron-containing TNU-9 zeolites were prepared by aqueous ion exchange in the range of Fe contents 0.6~3.3 wt%. Direct decomposition of $N_2O$ was performed varying $N_2O$ concentrations and reaction temperatures. Fe-TNU-9 zeolites used were characterized using XRD, $N_2$ sorption, SEM/EDX. A 2.7 wt% Fe-TNU-9 zeolite showed high activities and above this contents of Fe the effect of catalytic activity was little dominated. Fe-TNU-9 zeolites after ion exchange conserved their TNU-9 structure although the degree of crystallinity was decreased until ca. 60% in 3.1 wt% Fe-TNU-9 zeolite after ion exchange in 0.01 M Fe solution. The decrease in the degree of crystallinity could be correlated with the decrease of surface area and pore volume. The partial reaction order of $N_2O$ in the decomposition of $N_2O$ was dependent on the reaction temperature from 0.69 at $420^{\circ}C$ to 0.97 at $494^{\circ}C$. The activation energy of $N_2O$ was also dependent on the $N_2O$ concentration and its value is ranged to 34~43 kcal/mol.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.23 no.4
• /
• pp.21-31
• /
• 2015

The aim of this study is to determine the removal efficiency of total nitrogen and phosphorus from treated swine wastewater by Phragmites australis and Miscanthus sacchariflorus var Geode Uksae-1, and to determine its biomass total energy value and biomethane potential. Plants were grown with a bedding mixture either soil and sand or soil, sand, and bioceramic. Treeated swine wastewater with Total nitrogen (TN) and Total phosphorus (TP) of 222.78 mg/L and 66.11 mg/L, respectively, was utilized. The TN and TP removal is higher in the bio-ceramic-soil-sand bedding media treatment. The highest TN removal of 96.14% was performed by Miscanthus sacchariflorus var Geode Uksae-1, but the elemental analysis shows that Phragmites australis contains more nitrogen than Miscanthus sacchariflorus var Geode Uksae-1, indicating higher nitrogen uptake. The highest TP removal of 98.12% was performed by Phragmites australis. The cellulose content of the plant grown with the bioceramic-soil-sand bedding was approximately 3-6% higher than that of the plant grown in the soil-sand bedding. Different growing substrates may have an effect on the fiber content of plants. The biomethane potential of the produced biomass of the plants was between 57.01 and $99.25L-CH_4/kg$ VS. The lignin content is believed to inhibit the breakdown of plant biomass, resulting in the lowest methane production in the Phragmites australis grown in the soil-sand bedding media.

• Korean Journal of Food Science and Technology
• /
• v.23 no.1
• /
• pp.88-92
• /
• 1991

To analyze the effects of the system parameters on the target parameters, which include the amount of water evaporation, water solubility index(WSI) and water absorption index(WAI), test trials of fractional factorial design of the three process variables at three levels were carried out for corn grit with a laboratory twin-screw extruder with three different screw configurations. The system parameters collected from the trials, such as extrusion temperature, specific mechanical energy input(SME) and mean residence time(RT), were showed the ranges of $129{\sim}182^{\circ}C$, $67{\sim}163\;kwh/ton$ and $12{\sim}34\;sec$, respectively. Within these ranges of the system parameters, the target parameters were able to be quantified by using multiple regression equations. The correlation of results with the system parameters blocked by the screw configuration as dependent variables, yield correlation coefficients above 0.90, and the correlation using the system parameters obtained from whole experiment system as the dependent variables yield correlation coefficients around 0.80. The functional relationship, which can be quantified by second order polynomial regression equation with only two system parameters within necessary degree of accuracy, can he graped in three dimensional surface response and contour diagrams.

• Applied Chemistry for Engineering
• /
• v.9 no.2
• /
• pp.255-260
• /
• 1998

Metal hydrides, $LaNi_5$ and $LaNi_{4.5}Al_{0.5}$, were prepared using chemical synthetic method, and their physical properties were examined using various analytic techniques such as TGA, XRD, SEM and EDX. The activation of the chemically prepared $LaNi_5$ and $LaNi_{4.5}Al_{0.5}$ was achieved by two hydriding/dehydriding cycles only. The miasurements of P-C-T curves revealed that 6 and 5.5 hydrogen atoms were stored in LaNi5and $LaNi_{4.5}Al_{0.5}$, respectively. The hydriding reaction rated for $LaNi_{4.5}Al_{0.5}$ were measured by the method of initial rates. It was found that the shrinking unreacted core model could be applied for the analysis of hydriding kinetics of $LaNi_5$. The rate controlling step of this reaction was the dissociative chemisorption of hydrogen molecules on the surface of $LaNi_5$. The activation energy was $9.506kcal/mol-H_2$. The rates measured in the temperature range from 273 to 343K and in pressure difference ($P_o-P_{eq}$) range form 0.25 to 0.66atm could be expressed as the following equation ; $\frac{dX}{dt}=4.636(P_o-P_{eq})$ exp($\frac{-9506}{RT}$).

• Korean Chemical Engineering Research
• /
• v.54 no.3
• /
• pp.320-331
• /
• 2016

Linze-Donawitz gas (LDG) adjunctively produced in the steel mill contains over 60% of CO. Two processes that recover high purity CO from LDG were considered: COSORB and CO-Pressure swing adsorption (PSA). This study aimed to decide which one is more economically feasible than the other by techno-economic analysis (TEA). From the technical point of view of TEA, the process flow diagram (PFD) was constructed, the mass and energy balances were calculated, and the equipment type and size were determined in order to estimate the total capital investment (TCI) and the total production cost (TPC). From the economic point of view of TEA, economic performance such as return on investment (ROI) and payback period (PBP) was evaluated, and the sensitivity analysis was carried out to identify key factors influencing ROI and PBP. It was found that CO-PSA is more economically feasible due to higher ROI and lower PBP. The CO price highly influenced ROI and PBP.