• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.9 no.2
• /
• pp.63-71
• /
• 2011

A large volume of uranium electrokinetic leachate has been generated during the electrokinetic decontamination to remove uranium from contaminated soil. The treatment technology for the reuse of the uranium leachate was developed. The concentration of uranium in the generated uranium leachate was 180 ppm and concentrations of Mg(II), K(I), Fe(II), and Al(III) ions ranged from 20 ppm to 1,210 ppm. The treatment process for uranium leachate consisted mainly of mixing and cohesion, precipitation, concentration, and filtration. In order to obtain the pH=11 of a precipitate solution, the calcium hydroxide needs to be 3.0g/100ml and the sodium hydroxide needed to be 2.7g/100ml. The results of several precipitation experiments showed that a mixture of NaOH+0.2g alum+0.15g magnetite was an optimal precipitant for filtration. The average particle size of precipitate with NaOH+alum+0.15g magnetite was $600\;{\mu}m$. Because the total value of metal concentrations in supernatant at pH=9 was the smallest, sodium hydroxide should be added with 0.2g alum and 0.15g magnetite for pH=9 of leachate.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.2
• /
• pp.292-296
• /
• 2005

Physical and chemical properties of thexylboronic acid and its derivatives such as thexylboroxine and ethylene glycol or diethanolamine thexylboronic ester have been studied. Thexylboronic acid can be extracted from an organic solution with an aqueous sodium hydroxide solution as an “te”complex. It is readily converted into thexylboroxine in the presence of anhydrous magnesium sulfate in pentane. It reacts with simple alcohols only slowly; however, it reacts readily with excess diethanolamine in the presence of anhydrous magnesium sulfate to give the corresponding ester.

• Resources Recycling
• /
• v.28 no.4
• /
• pp.23-29
• /
• 2019

In order to recover pure alumina from balck dross, precipiatation experiments were done to the NaOH leaching solution of mechanically activated black dross. In this work, hydrogen peroxide was added to the synthic solution as a precipitating agent. Among some variables, the concentration of $H_2O_2$ and the volume ratio of $H_2O_2$ to solution showed a remarkable effect on the precipitation of aluminum hydroxide. At the optimum conditions, most of the aluminate was precipitated. Calcination of the aluminum hydroxide at $1200^{\circ}C$ led to the formation of ${\theta}$ and ${\alpha}$-alumina. The charactistics of the synthesized activated alumina was measured by XRD and EDS. The average particles size of the alumina was $3.73{\mu}m$.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.29 no.5
• /
• pp.222-228
• /
• 2019

In this study, we carried out the experiment to prepare lithium carbonate powder through gas-liquid reactions with a lithium-containing solution and $CO_2$ gas using lithium hydroxide, lithium chloride, and lithium sulfate. Thermodynamically, the carbonation reaction of a lithium-containing solution showed that aqueous reaction of lithium hydroxide occurs spontaneously, but aqueous reactions of lithium chloride and lithium sulfate does not occur spontaneously. In the case of lithium hydroxide solution, the recovery rate of lithium carbonate was 69.8 % at room temperature ($25^{\circ}C$), and increased to 89.4 % at $60^{\circ}C$. In the case of lithium chloride and lithium sulfate solution, lithium carbonate could be prepared using sodium hydroxide as an additive, but the recovery rates were 19.2 % and 16.7 %, respectively.

• Nuclear Engineering and Technology
• /
• v.48 no.2
• /
• pp.368-375
• /
• 2016

A sodiume-water reaction takes place when high-pressured water vapor leaks into sodium through a tiny defect on the surface of the heat transfer tube in a steam generator of the sodium-cooled fast reactor. The sodiume-water reaction brings deterioration of the mechanical strength of the heat transfer tube at the initial leakage site. As a result, it damages the crack itself, which may eventually enlarge into a larger opening. This self-enlargement is called "self-wastage phenomenon." In this study, a simulant experiment was proposed to reproduce the self-enlargement of a crack and to evaluate the mechanism of the self-wastage. The damage on the surface of the crack was simulated by making the neutralization reaction with hydrochloric acid solution and sodium hydroxide solution. A numerical investigation was carried out to validate the feasibility of the approach and to determine experimental conditions. From the computation results, it is observed that when 5M HCl is injected into 5M of NaOH with 0.05 m/s inlet velocity, the temperature at the surface near the crack increased over 319.26 K. The computational results show that the self-wastage phenomenon is capable of being reproduced by the simulant experiment.

• Journal of Korean Society for Atmospheric Environment
• /
• v.31 no.2
• /
• pp.173-180
• /
• 2015

The purpose of this study was to fabricate a ferric nitrate impregnated activated carbon, and the performance for hydrogen sulfide by adsorption was evaluated. Sodium hydroxide was utilized to control pH in the process during generation of ferric hydroxide on the surface of the carbon. Critical mixing duration for generation of ferric hydroxide on the carbon was 48 hrs at pH 1 of the solution, in which the chemical adsorption of hydrogen sulfide was enhanced. The adsorption capacity of the impregnated carbon increased up to 0.10 g hydrogen sulfide/g carbon, which was 4.3 times higher than that of the raw carbon. Presence of FeOOH on the surface of the impregnated carbon was examined by X-ray diffraction.

• Journal of the Semiconductor & Display Technology
• /
• v.19 no.2
• /
• pp.77-81
• /
• 2020

Silicon wafer etching in micro electro mechanical systems (MEMS) fabrication is challenging to form 3-D structures. Well known Si-wet etch of silicon employs potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH) and sodium hydroxide (NaOH). However, the existing silicon wet etching process has a fatal disadvantage that etching of the back side of the wafer is hard to avoid. In this study, a wet etching bath for 150 mm wafers was designed to prevent back-side etching of silicon wafer, and we demonstrated the optimized process recipe to have anisotropic wet etching of silicon wafer without any damage on the backside. We also presented the design of wet bath for 300 mm wafer processing as a promising process development.

• Restorative Dentistry and Endodontics
• /
• v.23 no.1
• /
• pp.379-390
• /
• 1998

In endodontic treatment, calcium hydroxide has been used as intracanal medicament. Although calcium hydroxide should be removed thoroughly before permanent root canal filling, no effective method for its removal has been reported. Because of irregularity of root canal walls, root curvatures and anatomic variations, it is insufficient to remove calcium hydroxide from the canal wall only by mechanical instrumentation Considering the chemical effects of irrigants on calcium hydroxide, $Ca^{++}$ dissolving effect from two calcium hydroxide products is investigated, using dis- tilled water, NaOCl, citric acid and EDTA. Vitapex$^{(R)}$ 0.1g and calcium hydroxide 0.03g were dissolved in distilled water, 5% NaOCl, 50% citric acid and 17% EDTA respectively, at 1, 3, 5, 10min. time interval. The solution was filtered using filter paper(pore size $5{\mu}m$) and $Ca^{++}$ concentration was determined by ion chromatography. The result were as follows : 1. Distilled water, NaOCl, citric acid and EDTA abstracted more $Ca^{++}$ from calcium hydroxide than Vitapex$^{(R)}$ except NaOCl 1, 5, 10 time interval. 2. EDTA and citric acid abstracted more $Ca^{++}$ from Vitapex$^{(R)}$ and calcium hydroxide than distilled water or NaOCl. The overall result support the view that water-based calcium hydroxide product is easily removed than oil-based calcium hydroxide product and EDTA, citric acid are more effective in $Ca^{++}$ elution than NaOCl or distilled water.

• Korean Journal of Materials Research
• /
• v.20 no.12
• /
• pp.691-698
• /
• 2010

Magnesium hydroxide-melamine core-shell particles were prepared through the coating of melamine monomer on the surface of magnesium hydroxide in the presence of phosphoric acid. The melamine monomer was dissolved in hot water but recrystallized on the surface of magnesium hydroxide by quenching to room temperature in the presence of phosphoric acid. The core-shell particle was applied to low-density polyethylene/ ethylene vinyl acetate (LDPE/EVA) resin by melt-compounding at $180^{\circ}C$ as flame retardant. The effect of magnesium hydroxide and melamine content has been studied on the flame retardancy of the core-shell particles in LDPE/EVA resin according to the preparation process and purity of magnesium hydroxide. Magnesium hydroxide prepared with sodium hydroxide rather than with ammonia solution revealed higher flame retardancy in core-shell particles with LDPE/EVA resin. At 50 wt% loading of flame retardant, core-shell particles revealed higher flame retardancy compared to that of the exclusive magnesium hydroxide in LDPE/EVA composite, and it was possible to satisfy the V0 grade in the UL-94 vertical test. The synergistic flame retardant effect of magnesium hydroxide and melamine core-shell particles was explained as being due to the endothermic decomposition of magnesium hydroxide and melamine, which was followed by the evolution of water from the magnesium hydroxide and porous char formation due to reactive nitrogen compounds, and carbon dioxide generated from melamine.

• Journal of the Society of Naval Architects of Korea
• /
• v.61 no.1
• /
• pp.51-60
• /
• 2024

Hi Air Korea and Hanwha ocean are currently developing an Onboard Carbon dioxide Capture System (OCCS) to absorb CO₂ emitted from ship's engine using a sodium hydroxide(NaOH) solution, and converting the resulting salt into a solid form through a chemical reaction with calcium oxide (CaO). The system process involves the following steps; 1)The reaction of CO₂ gas absorption in water, 2)The reaction between carbonic acid (H₂CO₃) and NaOH solution to produce carbonate or bicarbonate, and 3)The reaction between carbonate or bicarbonate and CaO to form calcium carbonate (CaCO₃). And ultimately, the solid material, CaCO₃, is separated and discharged using a separator. The OCCS has been installed on an ship and the test results have confirmed significant reduction effects of CO₂ in the ship's exhaust gas. A portion of the exhaust gas emitted from the engine was transferred to the OCCS using a blower. The flow rate of the transferred gas ranged from 800 to 1384 m³/hr, and the CO₂ concentration in the exhaust gas was 5.1 vol% for VLSFO, 3.7 vol% for LNG and a 12 wt% NaOH solution was used. The results showed a CO₂ capture efficiency of approximately 42.5 to 64.1 vol% and the CO₂ capture rate approximately 48.4 to 52.2kg/hr. Additionally, to assess the impact of the discharged CaCO₃on the marine ecosystem, we conducted "marine ecotoxicity test" and performed Computational Fluid Dynamics (CFD) analysis to evaluate the dispersion and dilution of the discharged effluent.