• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1030-1035
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• 1998

The porous alumina membrane was prepared from aluminum metal(99.8%) by anodic oxidation using DC power supply of constant current mode in an aqueous solution of sulfuric acid. To prevent the chemical dissolution of alumina membrane, $Al_2(SO_4)_3$, $AlPO_4$ and $Al(NO_3)_3$ which could be considered to supply $Al^{3+}$ ions were added to electrolyte solution at a reaction temperature of $20^{\circ}C$ and cumulative charge of $150C/cm^2$. Effects of these additives on the formation of porous alumina membrane were evaluated under various electrolyte concentration(5~20 wt%) and current densities($10{\sim}50mA/cm^2$). The membrane surfaces which were prepared in electrolyte solution with all the additives except $Al_2(SO_4)_3$ were damaged. However, when $Al_2(SO_4)_3$ was added to the $H_2SO_4$ solution, an uniform surface of porous alumina was obtained. Also, it was shown that the pore size of membrane was nearly independent on the quantity of $Al_2(SO_4)_3$ added at same electrolyte concentration and current density.

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.550-555
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• 2013

A hydrogel electrolyte consisting of potassium poly(acrylate) (PAAK) (3 wt%) in 6 M KOH aqueous solution is coated on poly(acrylonitrile) nonwoven separator to examine high-rate characteristics of activated carbon supercapacitor adopting the separator. The hydrogel is homogeneously coated on the surface pores of the nonwoven separator. The electrolyte uptake of the PAAK hydrogel maintains for 24 days higher than 230% and the coated separator shows slightly lower ionic conductivity ($2.9{\times}10^{-2}Scm^{-1}$) than that ($3.6{\times}10^{-2}Scm^{-1}$) of using 6 M KOH only. The activated carbon supercapacitor adopting the coated separator shows a specific capacitance higher than $27Fg^{-1}$ at $1000mVs^{-1}$ and a retention ratio higher than 97% after the 1000th cycle. This is due to strong interfacial contact of coated hydrogel electrolyte between the activated carbon electrode and the nonwoven separator.

• Journal of Biomedical Engineering Research
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• v.21 no.3 s.61
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• pp.273-277
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• 2000

The galvanostatic anodization of commercially Pure titanium plate (c.p.Ti, grade 2) was investigated in various concentrations of aqueous $H_3PO_4$ from 0.05M to 0.7M. The surfaces of anodic oxide films, formed by the current density in the range between 0.3 and $l.0 A/dm^2$. were analyzed by SEM and XRD. The voltage-time (V-T) curves displayed an initial linear part and a subsequent parabolic part, and the initial slopes increased with an increase in the current density in 0.05M $H_3PO_4$. As the concentration of the electrolyte increased, the V-T corves exhibit no change but the final voltage decreased. The anodic oxide film of titanium developed from fine grains to snowflake-like grains in a layered structure with an increase in the concentration of the electrolyte and current density. Sparking at the interface of the oxide/electrolyte accompanied the local deposition and dissolution of the oxide film through discharging. The crystallinity of the anodic oxide film increased with the anodizing voltage and decreased with an increase in the concentration of the electrolyte.

• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.255-260
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• 2011

$NH_4{^+}-{\beta}^{{\prime}{\prime}}$-alumina which is expected to an inorganic solid electrolyte of high temperature polymer electrolyte membrane fuel cells (PEMFC) was prepared by ion-exchange reaction of $K^{+}-{\beta}^{{\prime}{\prime}}$-alumina pellet with $NH_4NO_3$ aqueous solution and molten $NH_4NO_3$ salts as an ion-exchange medium in the autoclave and the heating mentle reaction. In the autoclave reaction, the concentrations of $NH_4NO_3$ solution was chosen at 5 and 10 M. Each ion-exchange reaction was carried out at 130, 150, 170, and $200^{\circ}C$ for 2, 4, 6 and 8 h. In the heating mentle reaction, ion-exchange was performed at $200^{\circ}C$ for 2, 4, 6 and 8 h with molten $NH_4NO_3$ salts. In order to determine the effect of reaction times, each ion-exchange reaction was repeated 3 times. The phase stability and the ion-exchange rate of $NH_4{^+}-{\beta}^{{\prime}{\prime}}$-alumina were analyzed by XRD and ICP.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.153-164
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• 1999

The solubilization of BTEX was evaluated in aqueous surfactant solutions with and without several additives. Anionic surfactant(Sodium Dodecyl Sulfate, SDS) and nonionic surfactants (NEODOL(equation omitted)25-3 and $SOFTANOL\circledR-90$ were used as test surfactants. The effects of surfactant HLB(Hydrophile-Lipophile Balance) Number and hydrocarbon molar volume and polarity of BTEX on the MSR(Molar Solubilization Ratio), micelle-water partition coefficient of BTEX, and CMC(C,itical Micelle Concentration) were investigated. Optimizing treatment conditions applicable to enhanced solubilization was also studied by manupulating salinity or electrolyte control with additives of ethyl alcohol, hydrotrope, and electrolyte solution. The most effective surfactant for solubilization was found $SOFTANOL\circledR-90$, since HLB number of 13.6 is similar to those values of BTEX ranging between 11.4 and 12.2, which was also proved experimentally. Ethyl alchohol of 3% was the most effective additives in reducing CMC and improving solubilization among the conditions using SDS, NEODOL(equation omitted)25-3, and $SOFTANOL\circledR-90$ with three additives. The partitioning of BTEX between surfactant micelles and aqueous solutions was characterized by a mole fraction micelle-phase/aqueous phase partion coefficient, $K_m$. Values of log $K_m$. for BTEX compounds in surfactant solutions of this study range from 2.95 to 3.76(100mM SDS) and 2.95 to 3.49(117mM $SOFTANOL\circledR-90$. Log $K_m$ appears to be a linear function of log $K_{ow}$ for SDS and $SOFTANOL\circledR-90$. A knowledge of partitioning of BTEX in aqueous surfactant system can be a prerequisite for the understanding of the behavior of hydrophobic organic compounds in soil-water systems in which surfactants play a role in remediation of contaminated soil and facilitated transport.

• Journal of the Mineralogical Society of Korea
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• v.28 no.2
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• pp.95-108
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• 2015

Nano-sized iron colloids are formed as acid mine drainage is exposed to surface environments and is introduced into surrounding water bodies. These iron nanomaterials invoke aesthetic contamination as well as adverse effects on aqueous ecosystems. In order to control them, the characteristics of their behaviour should be understood first, but the cumulative research outputs up to now are much less than the expected. Using zero-valent iron (ZVI) and magnetite, this study aims to investigate the behaviour of iron nanomaterials according to the change in the composition and pH of background electrolyte and the concentration of natural organic matter (NOM). The size and surface zeta potential of iron nanomaterials were measured using dynamic light scattering. Characteristic behaviour, such as aggregation and dispersion was compared each other based on the DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory. Whereas iron nanomaterials showed a strong tendency of aggregation at the pH near point of zero charge (PZC) due to electrostatic attraction between particles, their dispersions became dominant at the pH which was higher or lower than PZC. In addition, the behaviour of iron nanomaterials was likely to be more significantly influenced by cations than anions in the electrolyte solutions. Particularly, it was observed that divalent cation influenced more effectively than monovalent cation in electrostatic attraction and repulsion between particles. It was also confirmed that the NOM enhanced the dispersion nanomaterials with increasing the negative charge of nanomaterials by coating on their surface. Under identical conditions, ZVI aggregated more easily than magnetite, and which would be attributed to the lower stability and larger reactivity of ZVI.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.6
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• pp.684-688
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• 2007

The results of potentiostatic electrolysis of aqueous solution containing fluoride by bipolar packed bed electrolytic cell filled with granular aluminium were summarized. Removal efficiency of fluoride ion which it analyzed with ion chromatograph were 53, 73, 90% in applied voltage. Control the concentration of supporting electrolyte were 10, 30, 50, 70 mg/L and volume of packing material were 0, 25, 50, 75%, respectively, the quantity of electricity was $2.58A{\cdot}hr$ when the concentration of supporting electrolyte was 50 mg/L and the volume of packing material was 75%. As the results of electrolytsis of fluoride aqueous solution containing fluoride 10, 30, 50, 70 mg/L for 3 hours at 10 V, the removal efficiency of fluoride were 93.3, 80, 68.6%. Then the quantity of electricity were 2.58, 3.89, $5.43A{\cdot}hr$ and the fluoride removal amounts per quantity of electricity were 4.0, 3.5, $2.0mg/A{\cdot}hr$.

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.213-217
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• 1999

The electrochemical characteristics of two distinct adsorption sites of H at the polycrystalline Pt/0.2 M LiOH aqueous electrolyte interface have been studied using the phase-shift method. At the forward and backward scans, the under-potentially deposited H (WD H) peak occurs on the cyclic voltammogram. The transition region on the phase-shift profile or the Langmuir adsorption isotherm occurs at ca. -0.66 to -0.96 V vs. SCE. At the transition region (ca. -0.66 to -0.96 V vs. SCE), the equilibrium constant (K) for H adsorption transits from 18.5 to $4.0\times10^{-5}$ and vice versa. Similarly, the standard free energy $({\Delta}G_{ads})$ of H adsorption transits from -7.2 to 25.1kJ/mol and vice versa. The under and over-potentially deposited H (UPD H and OPD H) on the poly-Pt surface act as two distinguishable electroadsorbed H species. An exothermic reaction occurs at the UPD H range. Both the UPD H peak and the transition region are attributed to the two distinct adsorption sites of the UPD H and OPD H on the poly-Pt surface.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.695-700
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• 2019

n this study, the evaluation of performance of AORFB using anthraquinone derivative and TEMPO derivative as active materials in neutral supporting electrolyte with various membrane types was performed. Both anthraquinone derivative and TEMPO derivative showed high electron transfer rate (the difference between anodic and cathodic peak potential was 0.068 V) and the cell voltage is 1.17 V. The single cell test of the AORFB using 0.1 M active materials in 1 M KCl solution with using Nafion 212 membrane, which is commercial cation exchange membrane was performed, and the charge efficiency (CE) was 97% and voltage efficiency (VE) was 59%. In addition, the discharge capacity was $0.93Ah{\cdot}L^{-1}$ which is 35% of theoretical capacity ($2.68Ah{\cdot}L^{-1}$) at $4^{th}$ cycle and the capacity loss rate was $0.018Ah{\cdot}L^{-1}/cycle$ during 10 cycles. The single cell tests were performed with using Nafion 117 membrane and SELEMION CSO membrane. However, the results were more not good because of increased resistance because of thicker thickness of membrane and increased cross-over of active materials, respectively.

• Korean Journal of Materials Research
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• v.19 no.10
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• pp.544-549
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• 2009

Activated carbon (AC) with very large surface area has high capacitance per weight. However, such activation methods tend to suffer from low yields, below 50%, and are low in electrode density and capacitance per volume. Carbon NanoFibers (CNFs) had high surface area polarizability, high electrical conductivity and chemical stability, as well as extremely high mechanical strength and modulus, which make them an important material for electrochemical capacitors. The electrochemical properties of immobilized CNF electrodes were studied for use as in electrical double layer capacitor (EDLC) applications. Immobilized CNFs on Ni foam grown by thermal chemical vapor deposition (CVD) were successfully fabricated. CNFs had a uniform diameter range from 50 to 60 nm. Surface area was 56 m$^2$/g. CNF electrodes were compared with AC and multi wall carbon nanotube (MWNT) electrodes. The electrochemical performance of the various electrodes was examined with aqueous electrolyte of 2M KOH. Equivalent series resistance (ESR) of the CNF electrodes was lower than that of AC and MWNT electrodes. The specific capacitance of 47.5 F/g of the CNF electrodes was achieved with discharge current density of 1 mA/cm$^2$.