• 한국가정과학회지
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• 제6권1호
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• pp.27-34
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• 2003

We investigated the bacterial and chemical retting conditions of ramie grown in Hansan. Bacterial retting was done in troughs at a temperature of 30${\pm}$2$^{\circ}C$ for 1, 2, 3, 4, 5, 6 and 10 days. Chemical retting(CR) was done at the different conditions using sodium silicate (Na$_2$SiO$_3$), sodium carbonate(Na$_2$CO$_3$) and sodium hydroxide(NaOH) as alkali solutions. The retting solution was boiled during 1. 2, 4 and 6 hours respectively at the different concentration(0.5, 2.0, 4.0, 6.0. 8.0 %) with decorticated ramie stems submerged in it. The treated ramie was then rinsing with running tap water thoroughly, which was further soaker in 0.5% acetic acid (v/v) solution for three minutes and washed thoroughly with distilled water. Finally ramie was dried for 2 hours in vacuum oven at 100 $^{\circ}C$. To know change of ramie fiber characteristics retted at the different conditions, weight loss, fiber bundle strength were tested and color, texture, luster etc. were also sensually evaluated. The results were as follows. $.$ Weight loss of ramie retted in each alkali solutions were about 10%, 20% and 30% in sodium silicate, sodium carbonate and sodium hydroxide, respectively. $.$ Chemical retting was faster than bacterial retting, but the color of chemically retted ramies were worse than that of bacterially retted ramies. $.$ The combination of bacterial and chemical processing showed some merits. A combination of either 2 or 3 days of bacterial and then chemical retting might provide the best quality ramie. $.$ Ramie fiber became cottonized ramie when retted in 8% NaOH solution for 6-8hours.

• 한국환경과학회지
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• 제9권1호
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• pp.43-47
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• 2000

A study on the remediation of heavily for ion contaminated soils from abandoned iron mine was carried out, using ex-situ extraction process. Also, oxalic acid as a complex agent was evaluated as a function of concentration, reaction time and mixing ratio of washing agent in order to evaluate Fe removability of the soil contaminated from the abandoned iron mine. Oxalic acid showed a better extraction performance than 0.1N-HCl, i.e., the concentrations of Fe ion extracted from the abandoned mine for the former at uncontrolled pH and the latter were 1,750 ppm and 1,079 ppm, respectively. The optimum washing condition of oxalic acid was in the ratio of 1:5 and 1:10 between soil and acid solution during l hr reaction. The total concentrations of Fe ion by oxalic acid and EDTA at three repeated extraction, were 4,554 ppm and 864 ppm, respectively. The recovery of Fe ions from washing solution was achieved, forming hydroxide precipitation and metal sulfide under excess of calcium hydroxide and sodium sulfide. In addition, the amounted of sodium sulfide and calcium hydroxide for the optimal revovery of Fe were 15g/$\ell$ and 5g/$\ell$ from the oxalic acid complexes, respectively.

• 대한본초학회지
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• 제33권6호
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• pp.87-92
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• 2018

Objectives: The aim of the study was to analyze the constituents of Pyrolusitum, which was used to eliminate static blood and inflammation, to establish the basis of clinical application. Methods: Qualitative analysis was performed by X-Ray Diffraction (XRD) using the sample as a powder, and the elemental content of granular sample was measured by X-Ray Fluorescence (XRF). 1 M hydrochloric acid and 5% sodium hydroxide aqueous solution were added to observe the changing shape, respectively. Results: Qualitative analysis by XRD revealed that the Pyrolusitum samples used in the study contained quarts and kaolinite. Quantitative analysis by XRF revealed that the manganese content in the samples used in the study was 6.16% on average, while iron was contained the highest amount of 22.99%. The minor constituents include 1.08% of titanium, 0.30% of barium, 0.18% of lead, 0.06% of zirconium, 0.05% of chromium, 0.04% of zinc, 0.03% of cadnium, 0.02% of nickel, 0.01% of arsenic, 0.01% of copper, 0.01% of rubidium, 0.01% of strontium, 0.00% of molybdenum, respectively. And cobalt, which is reported to be a constituent of Pyrolusitum, was not detected at all in the samples of the study. Pyrolusitum was dissolved in dark brown when it was put into 1 M hydrochlorid acid, and there was brown precipitate when sodium hydroxide solution was added to Pyrolusitum and stirred. Conclusions: It was found that manganese and iron were the major constituents of Pyrolusitum, and it could be identified by using concentrated hydrochloric acid and sodium hydroxide solution.

• Journal of Electrochemical Science and Technology
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• 제14권1호
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• pp.59-65
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• 2023

Sodium hydroxide solutions are often employed as sterilization agents in the pharmaceutical industry. Here, the chloride content is considered as a critical impurity. In this study, an electrochemical method was developed to remove chloride ions (Cl^-) through the oxidative deposition of AgCl on a Ag anode. The Cl^- content in the commercially available 50% w/w NaOH solution employed was approximately 100 mg Cl^-/kg NaOH. As the OH^- content is approximately 18,000 times higher than the Cl^- content, the formation of AgCl may be expected to be thermodynamically less favorable than the formation of Ag₂O. However, activation energies for AgCl and Ag₂O formation have been reported to be approximately 3.8 and 31.2 kJ/mol, respectively, and indicate that AgCl formation is favored. AgCl can be selectively produced by controlling the anode potential. Here, the Cl^- concentration was reduced to less than 50 mg Cl^-/kg NaOH when an anode potential of 0.18 or 0.19 V vs. Hg/HgO (reference electrode) was applied for one hour at 50℃. XRD analysis and visual monitoring of the Ag anode confirmed the oxidative deposition of AgCl on the anode surface as well as the electrochemical desalination of the concentrated NaOH solution.

• 한국표면공학회지
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• 제19권1호
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• pp.13-19
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• 1986

Manganese in the Anode slime and the paste-positive material of waste-dry cell was recovered by leaching with the hydrochloric acid solution. The impurities (Zn, Fe, Pb), co-leached with manganese were removed from the leached solution prior to electrolysis by hydrometallurgical techniques such as the neutralization with ammonium hydroxide and cementation on manganese powder. The electrodeposition of manganese from the purified chloride solution with sodium selenate was performed. Cathode current efficiency was found to be affected significantly by the concentration of sodium selenate and ammonium chloride salt, bath temperate, current density and PH. The current efficiency of about 88.7% was obtained by electrolysis manganese chloride solution with sodium selenate (0.1/g) at 10$^{\circ}C$.

• 자연과학논문집
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• 제8권2호
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• pp.119-127
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• 1996

Zeolite인 mordenite 광물을 수산화나트륨용액으로 화학처리한 효과에 대해서 화학분석, X-선 분말회절, 열분석, 이산화탄소의 흡착측정 및 GC를 통하여 조사하였다. 출발원료로 mordenite 광물을 3시간동안 water bath 중 약 $95^{\circ}C$에서 NaOH 0.1-5N의 농도범위로 화학 처리한 결과, 시료중 함유된 모든 화학성분은 NaOH 0.5N 이하의 농도에서는 불용이고 mordenite 구조는 변화하지 않았으며 1N 이상의 농도에서는 실리카, 알루미나 등과 같이 성분들이 용해되었고 시료중 실리카의 용해비율이 알루미나의 용해보다 높으며 실리카와 알루미나의 비가 2-3N 농도 범위에서는 급격히 감소하였다.Mordenite 의 (202)면의 X-선 회절피크 강도와 $CO_2$ 흡착량은 1N 이상의 NaOH 농도가 증가함에 따라 감소하며 이로 인하여 mordenite 구조의 붕괴가 나타났다.산소, 질소 및 일산화탄소의 GC분리공정에서는 NaOH 용액 처리에 의한 영향을 받지 않으나 메탄과 크립톤의 용출피크가 넓어지는 경향이 나타나며 retention time 은 단축되었고 이 두 기체모두 용리피크는 산소 또는 질소와 중복되기 쉬운 경향을 보여주었다.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4062-4071
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• 2022

Long-term aluminum (Al) corrosion tests were designed to investigate the condition that would generate severe Al corrosion and precipitation. Buffer agents of sodium tetraborate (NaTB), trisodium phosphate (TSP) and sodium hydroxide (NaOH) were adopted. The insulation materials, fiberglass and calcium silicate (Ca-sil), were examined to explore their effects on Al corrosion. The results show that significant precipitates were formed in both NaTB/TSP-buffered solutions at high pH. The precipitates formed in NaTB solution raise more concerns on chemical effects in GSI-191. A passivation layer formed on the surfaces of coupon in solution with the presence of insulations could effectively mitigate Al corrosion. The Fe-enriched intermetallic particles (IPs) embedded in coupon appeared to serve as seeds to readily induce precipitation via providing extra area for heterogeneous Al hydroxide precipitation. X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses indicate that the precipitates are mainly boehmite (γ-AlOOH) and no direct evidence confirms the presence of sodium aluminum silicate or calcium phosphate.

• 한국환경과학회지
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• 제10권4호
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• pp.299-304
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• 2001

For the remediation of the contaminated soil with heavy metals, Cd, Cr, Cu, and Pb, the reaction parameters were optimized. Tartaric acid (TA) and oxalic acid(OA) as a washing agent and recovery of metals, The optimum washing conditions of TA and OA were in the ratio of 1 : 20 between soil and acid solution during 2hr reaction under unbuffered pH solutions. At the optimized reaction conditions, the removal efficiencies were compared with that of 0.1 M HCl and ethylenediamine tetraacetic acid(EDTA). TA showed higher efficiency on the removal of Pb than that of EDTA, which established for the remediation of contaminated soil with Pb and Cd metals. The recovery of metal ions from washing solution was achieved by adding calcium hydroxide and sodium sulfide by forming the precipitation of metal hydroxide and metal slfied. Optimum amounts of sodium sulgide and calcium hydroxide were Cd = 25g/$\ell$, Cu = 5~10g/$\ell$ and Pb = 5~10g/$\ell$ for the washing solution of OA and 2~5g/$\ell$ for the washing solution of TA, respectively. The amounts of $Na_2S$ and $CA(OH)_2$ for the tartaric acid was less than that of oxalic acid.

• 자원리싸이클링
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• 제14권6호
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• pp.3-9
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• 2005

본 연구에서는 CRT용 폐세륨연마재 건조분말로부터 수산화세륨을 선택적으로 분리회수 하고자 하였다. 폐세륨연마재에는 산화희토류가 약 $64.5\%$ 함유되어 있으며, 이중 산화세륨은 $36.5\%$로서 전체 희토류 중 $56.3\%$를 차지한다. 산화세륨은 희토류원소들 중에서 가장 안정된 형태로 이에 대한 분해가 용이하지 않다. 그러므로 황산화반응을 이용하여 산화희토류 및 산화세륨을 분해하고 수침출을 통하여 희토류의 분리 $\cdot$회수율을 향상시키고자 하였다 침출용액의 희토류는 황산나트륨을 이용한 복염[$\Re{\cdot}Na(SO_{4})_{2}$] 형태로 회수한 후, 수산화나트륨 수용액에 투입하여 수산화희토류 슬러리를 제조하였다. 공기 접촉에 의하여 3가 수산화세륨을 4가 수산화세륨으로 산화시킨 후 산도조절에 의하여 기타 수산화희토류로부터 수산화세륨을 분리하였다.

• 한국결정성장학회지
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• 제23권2호
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• pp.101-107
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• 2013

재생 세륨 전구체로부터 수산화세륨($Ce(OH)_3$), 염화세륨($CeCl_3{\cdot}nH_2O$), 탄산세륨($Ce_2(CO_3)_3{\cdot}8H_2O$) 및 산화세륨($CeO_2$)을 합성하고 Ultra-sonication을 통해 나노입자의 산화세륨(IV)을 제조하였다. 폐 유리연마재로부터 정제한 약 99 wt% 재생 세륨 분말을 출발물질로 하여 황산침출과 황산나트륨의 첨가조건을 통해서 황산나트륨세륨 화합물($CeNa(SO_4)_2$)을 합성하였다. 또한 황산나트륨세륨 화합물과 수산화나트륨 수용액 첨가량 비의 조건을 달리하여 수산화세륨을 제조하였으며 염산의 첨가량에 따라 염화세륨을 합성하였다. 연속적인 합성공정으로 침상형의 탄산세륨을 합성한 후 하소와 분산을 통해서 평균 30~40 nm의 산화세륨(IV)을 합성하였다.