• Journal of Environmental Science International
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• v.27 no.6
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• pp.401-410
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• 2018

Waste citrus peel-based activated carbon (WCAC) was prepared from waste citrus peels by activation with KOH. The removal of Cu and Pb ions from aqueous solution by the prepared WCAC was investigated in batch experiments. The solution pH significantly influenced Cu and Pb adsorption capacity and the optimum pH was 4 to 6. The adsorption of Cu and Pb ions by WCAC followed pseudo-second-order kinetics and the Langmuir isotherm model. The maximum adsorption capacity calculated by Langmuir isotherm model was 31.91 mg/g for Cu and 92.22 mg/g for Pb. As the temperature was increased from 303 K to 323 K, the ${\Delta}G^{\circ}$ value decreased from -7.01 to -8.57 kJ/mol for Cu ions and from -0.87 to -2.06 kJ/mol for Pb ions. These results indicated that the adsorption of Cu and Pb by WCAC is a spontaneous process.

• Journal of Sensor Science and Technology
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• v.15 no.5
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• pp.317-322
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• 2006

A method to determine quinine in aqueous solution by chemiluminescence method using a stopped flow system has been studied. The method is based on the increased chemiluminescence intensity with the addition of quinine to a solution of lucigenin and hydrogen peroxide. The effects of KOH concentration, flow rate of reagents, $H_{2}O_{2}$ concentration used for the masking of quinine on the chemiluminescence intensity have been investigated. The calibration curve for quinine was linear over the range from $1.0{\times}10^{-7}$ M to $1.0{\times}10^{-3}$ M, coefficient of correlation was 0.993 and the detection limit was $3.0{\times}10^{-8}$ M under the optimal experimental conditions of 1.0 M, 1.5 M, 3.0 mL/min for the concentration of $H_{2}O_{2}$, KOH and flow rate of reagents, respectively.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.947-949
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• 1998

In this paper, the NO was oxidized $NO_2$ by using the non-thermal plasma and NOx removal characteristics were measured by showering NaOH water-solution to $NO_2$. The NO oxidation increased in the order of DC, AC, and Pulse. NOx oxidation for two stage with applied voltage was better than that for one stage with applied voltage. NO oxidation didn't depend on applied voltage. While NO oxidation was going on, NOx removal efficiency was 20-25%, however, significantly depended on the injection method of air and $H_2O$ + air. When NaOH water-solution density of 20% was showered to flue gases, NOx removal efficiency increased to 64%.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.604-607
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• 2012

Solid base catalysts for biodiesel production were synthesized by impregnating basic metal species on two support materials with large specific surface area : zeolite and pyrolysis char. KL zeolite and Undaria pinnatifida char were impregnated with KOH aqueous solution and calcium nitrate solution, respectively, to enhance the basic strength. The catalysts synthesized were characterized using Hammett indicators and $CO_2$-TPD analysis. Biodiesel was produced using soybean oil and methanol over the catalysts synthesized. The content of fatty acid methyl esters was measured to evaluate the catalytic activity. Generally, the catalytic activity increased with increasing quantity of basic metal impregnated but impregnation of excessive amount of metal could cause reduction in the activity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.2
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• pp.254-262
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• 1996

$Pb(Zr_{0.52}Ti_{0.48})O_{3}$ (PZT) ceramics were prepared with uniform particle size of $1~3\;\mu\textrm{m}$ by hydrothermal synthesis at various conditions, such as hydrothermal reaction temperature, concentration of mineralizer and reaction time. PZT ceramics were formed above $180^{\circ}C$ for 2 hrs reaction using 10 M KOH solution as a mineralizer, but reaction condition was slightly different by starting materials. Morphology and characterization of PZT powders were investigated by XRD and SEM. By increasing the reaction temperature, KOH concentration and reaction time, the composition of the PZT phase tended to be homogeneous phase.

• Carbon letters
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• v.18
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• pp.43-48
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• 2016

Sulphonated polysulphone (SPS) has been synthesized and subsequently applied as binder for graphene oxide (GO)-based electrodes for development of electrochemical supercapacitors. Electrochemical performance of the electrode was investigated using cyclic voltammetry in 1M Na₂SO₄ and 1M KOH solution. The fabricated supercapacitors gave a specific capacitance of 161.6 and 216.8 F/g with 215.4 W/kg and 450 W/kg of power density, in 1M Na₂SO₄ and 1M KOH solutions, respectively. This suggests that KOH is a better electrolyte than Na₂SO₄ for studying the electrochemical behavior of electroactive material, and also suggests SPS is a good binder for fabrication of a GO based electrode.

• Journal of the Optical Society of Korea
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• v.18 no.3
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• pp.283-287
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• 2014

Square lattice nano-hole arrays with diameters and periodicities of 200 and 500 nm, respectively, are fabricated on InGaN/GaN blue light emitting diodes (LEDs) using electron-beam lithography and inductively coupled plasma reactive ion etching processes. Cathodoluminescence (CL) investigations show that light emission intensity from the LEDs with the nano-hole arrays is enhanced compared to that from the planar sample. The CL intensity enhancement factor decreases when the nano-holes penetrate into the multiple quantum wells (MQWs) due to the plasma-induced damage and the residues. Wet chemical treatment using KOH solution is found to be an effective method for light extraction from the nano-patterned LEDs, especially, when the nano-holes penetrate into the MQWs. About 4-fold CL intensity enhancement factor is achieved by the KOH treatments after the dry etching for the sample with a 250-nm deep nano-hole array.

• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.467-472
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• 2017

Alkaline electrolytes consisting of 6 M KOH and polymer (PEO, PVA, and PAAK) are coated on PAN nonwoven fabrics as a separator, and the electrochemical properties of the activated carbon supercapacitor adopting them are investigated in terms of redox behavior, specific capacitance, and interfacial impedance. Although the interaction between polymer and KOH are comparatively inactive in PEO and PVA, PAAK (3 wt.%)-KOH forms a hydrogel phase by active interactions between $COO^-K^+$ in side-chain of PAAK and $K^+OH^-$ from alkaline electrolyte solution, improving ionic conduction of electrolytes and the electrochemical properties of the supercapacitor. As a result, the activated supercapacitor adopting the PAAK-KOH shows the superior specific capacitance of $46.8Fg^{-1}$ at $100mVs^{-1}$.

• Carbon letters
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• v.12 no.1
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• pp.1-7
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• 2011

In the present study, the removal of Pb (II) ions on oxidized activated carbons (ACs) was investigated. ACs were derived from activation of indigenous cotton stalks waste with potassium hydroxide (KOH) in two-stage process. The KOH-ACs were subjected to liquid-phase oxidation with hot $HNO_3$ and one untreated sample was included for comparison. The obtained carbons were characterized by Fourier transform infrared (FTIR), slurry pH and $N_2$-adsorption at 77 K, respectively. Adsorption capacity of Pb (II) ions on the resultant carbons was determined by batch equilibrium experiments. The experimental results indicated that the oxidation with nitric acid was associated with a significant increase in mass of yield as well as a remarkable reduction in internal porosity as compared to the untreated carbon. The AC-800N revealed higher adsorption capacity than that of AC-800, although the former sample exhibited low surface area and micropore volume. It was observed that the adsorption capacity enhancement attributed to pore widening, the generation of oxygen functional groups and potassium containing compounds leading to cation-exchange on the carbon surface. These results show that the oxidized carbons represented prospective adsorbents for enhancing the removal of heavy metals from wastewater.

• Journal of Powder Materials
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• v.26 no.6
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• pp.481-486
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• 2019

Iron oxides currently attract considerable attention due to their potential applications in the fields of lithiumion batteries, bio-medical sensors, and hyperthermia therapy materials. Magnetite (Fe₃O₄) is a particularly interesting research target due to its low cost, good biocompatibility, outstanding stability in physiological conditions. Hydrothermal synthesis is one of several liquid-phase synthesis methods with water or an aqueous solution under high pressure and high temperature. This paper reports the growth of magnetic Fe₃O₄ particles from iron powder (spherical, <10 ㎛) through an alkaline hydrothermal process under the following conditions: (1) Different KOH molar concentrations and (2) different synthesis time for each KOH molar concentrations. The optimal condition for the synthesis of Fe₃O₄ using Fe powders is hydrothermal oxidation with 6.25 M KOH for 48 h, resulting in 89.2 emu/g of saturation magnetization at room temperature. The structure and morphologies of the synthesized particles are characterized by X-ray diffraction (XRD, 2θ = 20°-80°) with Cu-kα radiation and field emission scanning electron microscopy (FE-SEM), respectively. The magnetic properties of magnetite samples are investigated using a vibrating sample magnetometer (VSM). The role of KOH in the formation of magnetite octahedron is observed.