• Clean Technology
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• v.21 no.1
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• pp.22-32
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• 2015

In this study, we studied the characteristics of ion exchange for treatment of HSS (heat stable salts) which cause performance reduction in CO₂ gas capture amine solution using anion exchange resins. The optimum HSS removal efficiency, 96.1% was obtained when using strong base anion exchange resin SAR10 at dosage 0.05 g/mL, 316 K, pH 12 and the best resin regeneration efficiency, 78.8% was obtained using NaOH solution of 3 M at 316 K. The adsorption data were described well by the Freundlich model and the sorption intensity(n) was 2.0951 lying within the range of favorable adsorption. The adsorption selectivity coefficients were increased by increasing valences and size of ion and desorption selectivity coefficients showed a contradictory tendency to adsorption selectivity coefficients. By continuous HSS removal experiments, 13.3 BV of HSS contaminated solution was effectively treated and the optimum NaOH solution consumption was 5.2 BV to regenerate resins.

• Journal of Electrochemical Science and Technology
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• v.14 no.4
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• pp.311-319
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• 2023

This work was performed to characterize the electrochemical behavior of AZ31 Mg alloy in neutral aqueous solutions where Cl^-, SO₄^2-, PO₄^3-, and F^- ions were present and pH was adjusted to 6 to exclude the contribution of H⁺ and OH^- ions. Open-circuit potential (OCP) transient, electrochemical impedance spectroscopy (EIS) and potnetiodynamic polarization curves were employed. The OCP value appeared to decrease in the order of F^- > Cl^- > SO₄^2- > PO₄^3- ions while corrosion current density increased in the same order. Electrochemical impedance spectroscopy (EIS) data showed two capacitive arcs in all the solutions and one more inductive arc appeared in PO₄^3--containing solution. By fitting of two capacitive arcs, capacitance of dense film (C_df), resistance of porous film (R_pf) and double layer capacitance (C_dl) and charge transfer resistance (R_ct) beneath the porous films were obtained. A simplified model in which various thicknesses and coverages of dense and porous films are assumed to be present on the AZ31 Mg alloy surface, is suggested to explain the effects of four different anions on the electrochemical behavior of AZ31 Mg alloy.

• Journal of the Korean institute of surface engineering
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• v.56 no.5
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• pp.289-298
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• 2023

In this study, the effect of drying temperature on characteristics of the trivalent chromate film on electroplated zinc was investigated. An zinc-electroplated iron specimen with a thickness of 5 ㎛ was used for chromate treatment. Chromate treatment was conducted in a solution diluted 10 times from a mixture of Cr(NO₃)₃·9H₂0 360 g/L, Co(NO₃)₂·6H₂O 60 g/L, Na₂SO₄ 60 g/L, NH₄F·HF 25 g/L, and NaOH 20 g/L. The zinc electroplated specimen was treated using the chromate solution with pH 2.0 at 25 ℃ for 60 s. Subsequently, chromate-treated samples were dried in an electric furnace for 2h with temperature varied from 25 to 125 ℃. The corrosion rate increased with the increase in the drying temperature, and the surface morphology of the chromate-treated film was observed using FE-SEM. When the drying temperature changed, the color of the chromate film changed from green to yellow, and the thickness of the film changed from 362 to 241 nm, respectively. Additionally, corrosion resistance was evaluated via a salt spray test.

• Journal of Integrative Natural Science
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• v.12 no.4
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• pp.101-104
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• 2019

A hydrated strontium iron fluoride, Sr₂Fe₂F₁₀(H₂O) has been synthesized and characterized. The material was synthesized through mild hydrothermal reaction using an aqueous CF₃COOH solution. The material exhibits a one-dimensional structure consisting of chains of corner-shared Fe³⁺F₆ octahedra, isolated Fe³⁺F₅(H₂O) octahedra, chains of SrF₁₀ polyhedra and isolated SrF₈ polyhedra, respectively. Magnetic property measurements on Sr₂Fe₂F₁₀(H₂O) reveals an antiferromagnetic order at T_N of ~2.5 K with a Weiss temperature (θ) of -61.51 K.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.3
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• pp.55-64
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• 2023

This batch experiment was conducted to investigate the patterns of major plant nutrients in the leachates from the soil that was incorporated with rice hull biochar adjusted pH with dry fish powder utilizing rice hull biochar for loading the soil microorganisms. The rice hull biochar adjusted pH between 6.0 and 7.0, and the mixture ratio of rice hull biochar and dry fish powder was 4:6. The treatments consisted of three; the soil incorporated with rice hull biochar non-adjusted pH with dry fish powder as control (RB + DF), the soil incorporated with rice hull biochar adjusted pH by pyroligneous acid solution and dry fish powder (RBP+DF), and the soil incorporated with rice hull biochar adjusted pH by citric acid solution and dry fish powder (RBC+DF). NH₄-N, NO₃-N, PO₄-P, and K concentrations in the leachates were analyzed during incubation. The accumulated NH₄-N and PO₄-P concentrations in the leachates from the RBC+DF treatment were the highest during leaching periods. The highest accumulated NO₃-N and K concentrations in the leachates from the RBP+DF treatment were observed. It observed that NH₄-N and PO₄-P were more released in the adjusted citric acid solution, but NO₃-N and K were less released than those in the pyroligneous acid solution due to their low absorption capacity. Furthermore, it is necessary to investigate crop growth responses to the soil incorporated with adjusted pH rice hull biochar and dry fish powder for loading soil microorganisms.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.210-213
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• 2011

Glass-ceramics composed of $5Na_2O-36CaO-10TiO_2-xP_2O_5$ could be obtained with $P_2O_5$ content as following procedure: 1) leaching out $Ca_3(PO_4)_2$ crystals between $Ca_3(PO_4)_2$ and $NaTi_2(PO_4)_3$ selectively in 1 N HCl solution for 2 days, and 2) exchanging $Na^+$ ion to $Ag^+$ ion in Ag($NO_3$) solution for 1 day. Scanning electron microscope (SEM) and X-rat diffractometer (XRD) were measured to verify the proper synthesis of glass-ceramics. And anti-bacteria test was accomplished using Staphylococus aureus bacteria. In the results of anti-bacteria test, the bacteria were died perfectly after 3 hours.

• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.223-228
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• 1998

Glass films of $SiO_2-TiO_2-M_xO_y$ (M = Co, Cr or Cu) have been prepared on soda-lime-silica slide glasses by the chemical solution method using a spin-coating technique. Commercially available tetraethyl orthosilicate, titanium trichloride, and cobalt-, chromium- and copper-nitrates were used as starting materials. No crystalline segregations of $Co_3O_4$, $Cr_2O_3$ and CuO were observed by X-ray diffraction ${\theta}-2{\theta}$ scans. From the optical transmission analysis, cobalt existed as $ Co^{2+}$ in tetrahedral coordination, chromium as $Cr^{6+}$ in tetrahedral symmetry and copper as $Cu^{2+}$ in octahedral coordination. Films with a crack-free and no texture exhibited homogeneous interfaces between the films and the substrates along the cross-section.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1201-1207
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• 2020

This study explored whether MXene (Ti₃C₂T_x) could remove radioactive Cs⁺ from model nuclear wastewater. Various adsorption tests were performed and the physical aspects of the interaction were investigated. We varied the MXene dosage, Cs⁺ initial concentration, solution pH, solution temperature and exposure time. MXene adsorption exhibited very fast kinetics, based on the fact that equilibrium was achieved within 1 h. MXene exhibited an outstanding adsorption capacity (148 mg g^-1) at adsorbent and adsorbate concentrations of 5 and 2 mg L^-1, respectively, at neutral pH condition (i.e., pH 7). We explored Cs⁺ adsorption by MXene in the presence of four different ions (NaCl, KCl, CaCl₂ and MgCl₂) and three different organic acids (sodium oleate, oxalic acid, and citric acid). The Cs⁺ removal rate changed in the presence of these components; adsorption of Cs⁺ by MXene thus involved ion exchange, supported by both Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. We confirmed that MXene was re-usable for at least four cycles. MXene is cost-effective and practical when used to adsorb radionuclides (e.g., Cs⁺) in nuclear wastewater.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.122-126
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• 2018

Mesoporous molecular sieves were prepared by the reaction of $Na_2SiO_3$ and $H_2SiF_6$ using nonionic micelle templates in an aqueous solution. Well-crystalline mesoporous molecular sieves were obtained after several seconds at atmospheric conditions. Powder samples exhibited d-spacing of 3.8-5.1 nm with the sharpness of the d00l peak, showing well-crystalline mesoporous molecular sieves, pore size distributions of 2.5-3.1 nm and large specific surface areas of $290-1,018m^2/g$, depending on types of surfactants. SEM images of samples showed well-divided spherical particles with an uniform size of ${\sim}0.5{\mu}m$ and TEM images demonstrated uniform pores with a worm hole shape.

• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1189-1196
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• 2003

Ferroelectric B $i_{3.25}$L $a_{0.75}$ $Ti_3$ $O_{12}$ (BLT) solution was synthesized by sol-gel process. BLT thin films were deposited on Pt/Ti $O_2$/ $SiO_2$/Si substrates by spin-coating. In this experiments, Bi(TMHD)$_3$, La(III)2-Methoxyethoxide, and Ti(IV) i-propoxide were used as starting materials, which were dissolved in 2-Methoxyethanol. Rapid Thermal Annealing (RTA) was used to promote crystallization of BLT thin films. The thin films with RTA process were compared with those with non-RTA process on electrical properties. After RTA process, the remanent polarization value (2Pr) of BLT thin films annealed at 72$0^{\circ}C$ was 20.46 $\mu$C/$\textrm{cm}^2$ which was approximately 27% higher than that of non-RTA process at 5 V.