• Bulletin of the Korean Chemical Society
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• 제28권2호
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• pp.251-256
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• 2007

The crystal structure of fully dehydrated partially Cs+-exchanged zeolite X, [Cs52Na40Si100Al92O384], a = 24.9765(10) A, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21 °C. The crystal was prepared by flow method for 5 days using exchange solution in which mole ratio of CsOH and CsNO3 was 1 : 1 with total concentration of 0.05 M. The crystal was then dehydrated at 400 °C and 2 × 10-6 Torr for 2 days. The structure was refined to the final error indices, R1 = 0.051 and wR2 (based on F2) = 0.094 with 247 reflections for which Fo > 4σ (Fo). In this structure, about fifty-two Cs+ ions per unit cell are located at six different crystallographic sites with special selectivity; about one Cs+ ion is located at site I, at the centers of double oxygen-rings (D6Rs), two Cs+ ions are located at site I', and six Cs+ ions are found at site II'. This is contrary to common view that Cs+ ions cannot pass sodalite cavities nor D6Rs because six-ring entrances are too small. Ring-opening by the formation of ?OH groups and ring-flexing make Cs+ ions at sites I, I', and II' enter six-oxygen rings. The defects of zeolite frameworks also give enough mobility to Cs+ ions to enter sodalite cavities and D6Rs. Another six Cs+ ions are found at site II, thirty-six are located at site III, and one is located at site III' in the supercage, respectively. Forty Na+ ions per unit cell are located at two different crystallographic sites; about fourteen are located at site I, the centers of D6Rs and twenty-six are also located at site II in the supercage. Cs+ ions and Na+ ions at site II are recessed ca. 0.34(1) A and 1.91(1) A into the supercage, respectively. In this work, the highest exchange level of Cs+ ions per unit cell was achieved in zeolite X by conventional aqueous solution methods and it was also shown that Cs+ ion could pass through the sixoxygen rings.

• 공업화학
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• 제20권1호
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• pp.80-86
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• 2009

파라자일렌 분리용 흡착제로서 효과적인 결합제가 없는 제올라이트 BaX 성형체를 제조하는 방법에 대하여 검토하였다. 제올라이트 NaX 타입의 결정분말을 무기결합제인 colloidal silica sol (C.S.) 용액과 기공형성제인 microcrystalline cellulose 분말을 이용하여 구형화 한 후 소성, binderless 처리, 바륨 이온교환, 활성화 등의 단계를 거치면서 넓은 비표 면적과 우수한 강도 및 파라자일렌에 대한 선택도를 갖는 파라자일렌 분리용 흡착제를 제조하였다. 각 시료의 무기결합제$SiO_2$함량을 14.0 wt%, 18.0 wt%, 22.3 wt%로 조절하여, 무기결합제의 함량 증가에 따른 시료 강도의 변화에 대해 검토하였다. 구형화 시료의 무기결합제 함량이 증가 될수록 binderless 처리 후의 강도가 증가함을 확인할 수 있었다. 이렇게 제조된 시료에 무게비 1 : 1 : 1로 혼합된 혼합자일렌 용액으로 $90^{\circ}C$에서 회분식 흡착실험을 수행해본 결과, 본 연구에서 제조된 binderless zeolite BaX는 파라자일렌에 선택적인 흡착능을 보임을 확인하였다. 이렇게 제조된 흡착제는 충분한 강도(0.450 kgf)와 결정화도(98.53%), BET 비표면적$(647.57m^2/g)$을 가지면서, 파라자일렌을 선택적으로 흡착함을 확인할 수 있었다.

• 한국결정성장학회지
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• 제11권1호
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• pp.14-19
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• 2001

NaX 제올라이트의 결정화 과정 중 온도에 따른 결정 크기를 측정하였다. 이때 선형결정성장속도 상수는 80, 90, 100$^{\circ}C$에 대해서 각각 0.0441$\mu\textrm{m}$/h, 0.0595$\mu\textrm{m}$/h 그리고 0.0972$\mu\textrm{m}$/h로 얻어졌다. 반응온도와 선형결정성장율 사이의 관계를 이용하여 활성화에너지는 43.243 kJ/mol 로 계산되었다. 결정화 반응의 종료는 각각 $80^{\circ}C$에서 20일 90$^{\circ}C$에서 16일, 100$^{\circ}C$에서 9일로 각각 나타났다. 반응온도의 증가에 따라서 최종생성물 결정크기는 감소할 뿐만 아니라 결정화 시간도 역시 감소하였다.

• 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.

• 한국환경과학회지
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• 제29권12호
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• pp.1261-1274
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• 2020

The characteristics of ammonia-nitrogen (NH4+-N) adsorption by a zeolitic material synthesized from Jeju scoria using the fusion and hydrothermal method was studied. The synthetic zeolitic material (Z-SA) was identified as a Na-A zeolite by X-ray diffraction, X-ray fluorescence analysis and scanning electron microscopy images. The adsorption of NH4+-N using Jeju scoria and different types of zeolite such as the Z-SA, natural zeolite, and commercial pure zeolite (Na-A zeolite, Z-CS) was compared. The equilibrium of NH4+-N adsorption was reached within 30 min for Z-SA and Z-CS, and after 60 min for Jeju scoria and natural zeolite. The adsorption capacity of NH4+-N increased with approaching to neutral when pH was in the range of 3-7, but decreased above 7. The removal efficiency of NH4+-N increased with increasing Z-SA dosage, however, its adsorption capacity decreased. For initial NH4+-N concentrations of 10-200 mg/L at pH 7, the adsorption rate of NH4+-N was well described by the pseudo second-order kinetic model than the pseudo first-order kinetic model. The adsorption isotherm was well fitted by the Langmuir model. The maximum uptake of NH4+-N obtained from the Langmuir model decreased in the order of Z-CS (46.8 mg/g) > Z-SA (31.3 mg/g) > natural zeolite (5.6 mg/g) > Jeju scoria (0.2 mg/g).

• 대한환경공학회지
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• 제39권2호
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• pp.66-73
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• 2017

본 연구에서는 제올라이트 X를 이용한 Cs 이온 흡착시 흡착시간 및 초기농도, 온도 및 pH 변화와 같은 영향인자를 평가하였다. 이 결과로부터 Cs 이온의 흡착속도, 등온흡착량 및 열역학적 특성을 해석하였다. 제올라이트 X에 의한 Cs 이온의 흡착은 pH 5~10에서 효과적이었으며, 평형흡착시간은 약 60분이었다. 흡착속도와 등온흡착량은 유사 2차 속도 모델식과 Langmuir 식에 잘 적용되었다. Langmuir 식으로 구한 Cs 이온의 최대 흡착량은 293~333 K에서 각각 303.03~333.33 mg/g이었다. 제올라이트 X에 의한 Cs 이온의 흡착은 흡열반응이고 자발적인 반응이었다. 실험값을 다중회귀분석으로 최적화하여 2차 다항식을 얻었다. 이 최적화된 식으로부터 구한 종속변수의 값과 실험에서 구한 값은 잘 일치하였다.

• 공학논문집
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• 제5권1호
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• pp.57-62
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• 2004

국내 천연 제올라이트에 포함된 feldspar와 illite의 불순광물을 공기 분급 조작 의하여 정제하였다. 공기 분급된 제올라이트를 XRD로 분석한 결과 공기분급에 의하여 제올라이트와 불순광물을 분리할 수 있었고, 공기 분급을 함으로서 불순광물이 감소된 것을 알 수 있었다. 또한, 공기 분급된 천연 제올라이트를 1N NaOH용액으로 100, 150, $200^{\circ}C$에서 17시간동안 수열처리한 결과 mordenite와 clinoptiolite에서 phillilsite와 analcime의 상변화를 얻을 수 있었다.

• 한국환경보건학회지
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• 제33권4호
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• pp.317-324
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• 2007

The sewage treatment sludge disposal has become a serious environmental problem because of restricted direct land-filling and oceandumping in spite of their large amounts discharged. So the recycling of sewage treatment sludge is very useful alternative for waste management. Here, we studied the feasibility of zeolite synthesis in open system from the sewage treatment sludge incinerator fly ash by means of hydrothermal synthesis. We considered the concentration of NaOH, reaction time, reaction temperature and reaction step as synthesis variables. The phase of zeolite products was identified by X-ray diffractometer(XRD) and ammonium ion exchange test was performed for the raw fly ash and two zeolite products(Z-3 and Z-5). In leaching test of the raw fly ash, hazard metal is detected very low level compared with regulatory leaching test standard. But in total recoverable test, the total contents of the fly ash were very high in terms of the standard for waste-derived fertilizer. Through hydrothermal reaction, small amount of zeolite P was synthesied in 1 N of NaOH solution and relatively large amount of hydroxysodalite was synthesied in 3 N and 5 N of NaOH solution with similar peak intensity. Addition of an aging step in the synthesis didn't increase the amount of zeolite phase. Maximum $NE_4^+-N$ exchange capacity is 1.49 mg $NH_4^+-N/g$ in Z-3 and 1.38 mg $NH_4^+-N/g$ in Z-5. Most of the ammonium ion is exchanged in 30 minutes and disorption did not occur until 5 hours.

• 한국환경과학회지
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• 제28권6호
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• pp.561-570
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• 2019

A zeolitic material (Z-Y2) was synthesized from Coal Fly Ash (CFA) using a fusion/hydrothermal method under low-alkali condition (NaOH/CFA = 0.6). The adsorption performance of the prepared zeolite was evaluated by monitoring its removal efficiencies for Sr and Cs ions, which are well-known as significant radionuclides in liquid radioactive waste. The XRD (X-ray diffraction) patterns of the synthesized Z-Y2 indicated that a Na-A type zeolite was formed from raw coal fly ash. The SEM (scanning electron microscope) images also showed that a cubic crystal structure of size $1{\sim}3{\mu}m$ was formed on its surface. In the adsorption kinetic analysis, the adsorption of Sr and Cs ions on Z-Y2 fitted the pseudo-second-order kinetic model well, instead of the pseudo-first-order kinetic model. The second-order kinetic rate constant ($k_2$) was determined to be $0.0614g/mmol{\cdot}min$ for Sr and $1.8172g/mmol{\cdot}min$ for Cs. The adsorption equilibria of Sr and Cs ions on Z-Y2 were fitted successfully by Langmuir model. The maximum adsorption capacity ($q_m$) of Sr and Cs was calculated as 1.6846 mmol/g and 1.2055 mmol/g, respectively. The maximum desorption capacity ($q_{dm}$) of the Na ions estimated via the Langmuir desorption model was 2.4196 mmol/g for Sr and 2.1870 mmol/g for Cs. The molar ratio of the desorption/adsorption capacity ($q_{dm}/q_m$) was determined to be 1.44 for Na/Sr and 1.81 for Na/Cs, indicating that the amounts of desorbed Na ions and adsorbed Sr and Cs ions did not yield an equimolar ratio when using Z-Y2.

• Bulletin of the Korean Chemical Society
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• 제19권1호
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• pp.98-103
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• 1998

The crystal structure of dehydrated $Rb^+$-exchanged zeolite X, stoichiometry $Rb_{71}Na_{21}-X\; (Rb_{71}Na_{21}Si_{100}Al_{92}O_{384})$ per unit cell, has been determined from single-crystal X-ray diffraction date gathered by counter methods. The structure was solved and refined in the cubic space group Fd3, a=25.007(3) Å at 21(1) ℃. The crystal was prepared by ion exchange in a flowing stream using a 0.05 M aqueous RbOH solution (pH=12.7). The crystal was then dehydrated at 360 ℃ and $2{\times}10^{-6}$ torr for two days. The structure was refined to the final error indices, $R_1=0.047$ and $R_2=0.040$ with 239 reflections for which I> 3σ(I). In this structure, 71 $Rb^+$ ions per unit cell are found at six different crystallographic sites and 21 $Na^+$ ions per unit cell are found at two different crystallographic sites. Four and a half $Rb^+$ ions are located at site Ⅰ, the center of the hexagonal prism. Nine $Rb^+$ ions are found at site Ⅰ' in the sodalite cavity (Rb-O=2.910(15) Å and O-Rb-O=78.1(4)°). Eighteen $Rb^+$ ions are found at site Ⅱ in the supercage (Rb-O=2.789(9) Å and O-Rb-O=92.1(4)°). Two and a half $Rb^+$ ions, which lie at site Ⅱ', are recessed ca. 2.07 Å into the sodalite cavity from their three O(2) oxygen planes (Rb-O=3.105(37) Å and O-Rb-O=80.6(5)°). Thirty-two $Rb^+$ ions are found at site Ⅲ deep in the supercage (Rb-O=2.918(12) Å and O-Rb-O=71.9(4)°), and five $Rb^+$ ions are found at site Ⅲ'. Seven $Na^+$ ions also lie at site Ⅰ. Fourteen $Na^+$ ions are found at site Ⅱ in the supercage (Na-O=2.350(19) Å and O-Na-O=117.5(6)°).