• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.1
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• pp.1-14
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• 2017

For the removal of cesium (Cs) from high radioactive/high salt-laden liquid waste, this study synthesized a highly efficient composite adsorbent (potassium cobalt ferrocyanide (PCFC)-loaded chabazite (CHA)) and evaluated its applicability. The composite adsorbent used CHA, which could accommodate Cs as well as other molecules, as a supporting material and was synthesized by immobilizing the PCFC in the pores of CHA through stepwise impregnation/precipitation with $CoCl_2$ and $K_4Fe(CN)_6$ solutions. When CHA, with average particle size of more than $10{\mu}m$, is used in synthesizing the composite adsorbent, the PCFC particles were immobilized in a stable form. Also, the physical stability of the composite adsorbent was improved by optimizing the washing methodology to increase the purity of the composite adsorbent during the synthesis. The composite adsorbent obtained from the optimal synthesis showed a high adsorption rate of Cs in both fresh water (salt-free condition) and seawater (high-salt condition), and had a relatively high value of distribution coefficient (larger than $10^4mL{\cdot}g^{-1}$) regardless of the salt concentration. Therefore, the composite adsorbent synthesized in this study is an optimized material considering both the high selectivity of PCFC on Cs and the physical stability of CHA. It is proved that this composite adsorbent can remove rapidly Cs contained in high radioactive/high salt-laden liquid waste with high efficiency.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.490-499
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• 1998

This study was initiated to investigate the applicability of sludge from water or waste water treatment on the crop cultivation. Sludge is generated in the process of water and wastewater treatment process in large quantity. The sludge can cause many environmental problems. we have a many available treatment methods of sludge However, these methods still shortcomings and are not. The composition of typical municipal sludge contains organics and inorganics. The organics components are normally burnt in high temperature and mainly inorganics components are left after thermal treatment process. For the production of artificial media, chabazite was used as additive, and the mixed material was thermally treated in the firing kiln at 800~1,10$0^{\circ}C$ for about 10 minutes. The physical and chemical characteristics of artificial media were analyzed and it showed that the artificial media could be used as a media for plants and soil conditioner for farmland. The concentrations of the toxic heavy metals in the media were lower then those in the soil quality standard for farmland. This study illustrated that the artificial media production process, and introduced how to produce it's possible application as a media for Plant growth.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.5
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• pp.64-70
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• 1997

Sludge is generated in the process of water and wastewater treatment, and it has been causing various problems environmentally and economically. The firing technology in pottery industry was applied to the sludge treatment, and the final product was called artificial soil. For the production of artificial soil, lime and chabazite was used as additive, and the mixed material was thermally treated in the firing kiln at $300^{\circ}$ temperature for about 15 minutes. The physico-chemical characteristics of the artificial soil was analyzed and it showed that the artificial soil could be used as a soil conditioner for farmland. The concentrations of the toxic heavy metals in the artificial soil were lower than those in the soil quality standard for farmland. It was high in permeability, total nitrogen and total phosphorous concentrations and surface area of the artificial soil compared to the common field soil. Preliminary cost analysis showed that the sludge treatment cost for artificial soil was less than the disposal cost in the current landfill disposal method. This study illustrated that the artificial soil production process can be a feasible alternative for sludge treatment, and produced artificial soil may he applied to farmland without causing significant adverse effect. Further study is recommended for practical application of the system and verification of the longterm effect of the artificial soil on farmland.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.1
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• pp.49-58
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• 2018

For the immobilization of high-radioactive nuclides such as Cs and Sr by high-temperature thermal decomposition, this study was carried out to investigate the phase transformation with calcined temperature by using TGA (thermogravimetric analysis) and XRD (X-ray diffraction) in the Cs-adsorbed CHA (chabazite zeolite of K type)-Cs and CHA-PCFC (potassium cobalt ferrocyanide)-Cs zeolite system, and Sr-adsorbed 4A-Sr and BaA-Sr zeolite system, respectively. In the case of CHA-Cs zeolite system, the structure of CHA-Cs remained at up to $900^{\circ}C$ and recrystallized to pollucite ($CsAlSi_2O_6$) at $1,100^{\circ}C$ after undergoing amorphous phase at $1,000^{\circ}C$. However, the CHA-CFC-Cs zeolite system retained the CHA-PCFC-Cs structure up to $700^{\circ}C$, but its structure collapsed in $900{\sim}1,000^{\circ}C$, and then transformed to amorphous phase, and recrystallized to pollucite at $1,100^{\circ}C$. In the case of 4A-Sr zeolite system, on the other hand, the structure of 4A-Sr maintained up to $700^{\circ}C$ and its phase transformed to amorphous at $800^{\circ}C$, and recrystallized to Sr-feldspar ($SrAl_2Si_2O_8$, hexagonal) at $900^{\circ}C$ and to $SrAl_2Si_2O_8$ (triclinic) at $1,100^{\circ}C$. However, the BaA-Sr zeolite system structure began to break down at below $500^{\circ}C$, and then transformed to amorphous phase in $500{\sim}900^{\circ}C$ and recrystallized to Ba/Sr-feldspar (coexistence of $Ba_{0.9}Sr_{0.1}Al_2Si_2O_8$ and $Ba_{0.5}Sr_{0.5}Al_2Si_2O_8$) at $1,100^{\circ}C$. All of the above zeolite systems recrystallized to mineral phase through the dehydration/(decomposition) ${\rightarrow}$ amorphous ${\rightarrow}$ recrystallization with increasing temperature. Although further study of the volatility and leachability of Cs and Sr in the high-temperature thermal decomposition process is required, Cs and Sr adsorbed in each zeolite system are mineralized as pollucite, Sr-feldspar and Ba/Sr-feldspar. Therefore, Cs and Sr seen to be able to completely immobilize in the calcining wasteform/(solidified wasteform).

• Korean Journal of Environmental Agriculture
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• v.19 no.3
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• pp.234-241
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• 2000

For the recycling of sludge as soil conditioner, the firing technology in pottery industry was applied to the sludge treatment, and produced artificial media with many voids. To produce artificial media using sludge, chabazite and lime were used as additives, and the mixture of sludge and additives was thermally treated in the firing kiln at about $800{\sim}1,100^{\circ}C$ for about ten minutes. The effect of mixed artificial media into upland soil was investigated through the crop growth experiment and the physical & chemical characteristics of the mixed soils were analysed. The pH of artificial media was higher than that of the control soils. After the plant growth experiment, artificial media plots almost contained more CEC, OM, TN, TP and $AV.P_2O_5$ than upland soil plots. From the growth analysis, growth of soybean and corn in the artificial media plots was better than that in the original upland soil plots. The yield of soybean and corn in the artificial media plots were about 46kg/10a, 194kg/10a, respectively, which is higher than that in the control. Heavy metals in the artificial media plots were lower than the standard regulation. Therefore, the artificial media produced from sludge can be mixed into farmland, and crop production can be increased additionally.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.61-71
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• 1992

Through the low-temperature(60-150${\circ}C$) hydrothermal treatment of perlite with the alkaline solution at various NaOH concentrations, the mode of volcanic glass alteration and resultant zeolite formation were investigated in a closed system. At a temperature of 80${\circ}C$ and alkalinities of pH range 8 to 12, corresponding to the natural environments of diagenetic zeolite formation, only weak dissolution of perlitic glass occurs without zeolite formation despite the residence time of 100 days. Activities of Si and Al increase progressively, as a consequence of increasing pH, whereas activity ratios of Si/Al decrease. Zeolites were synthesized from perlite in the alkaline solution at above 0.1M NaOH concentrations. Below the temperature of 100${\circ}C$ Na-P was mainly formed, whereas analcime was the dominant zeolite at the temperature range of 100-150${\circ}C$. During Na-P synthesis chabazite and Na-X were also formed as by-products in case of lower proportion of solution/sample(<10ml/g) and higher NaOH concentraion (>3M), respectively. The alteration modes of perlite in the zeolite synthesis reflect that the formation of synthetic zeolites occurs as an incongruent dissolution likely with the diagenetic formation of natural zeolites from volcanic glass. Considering much difference in reaction kinetics between natural and synthetic systems, however, the evaluated synthetic conditions in these experiments were not directly applicable to the natural diagenetic system.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.305-311
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• 2021

Effects of chitosan as a mesopore directing agent of SAPO-34 catalysts were investigated to improve the catalytic lifetime in DTO reaction. The synthesized catalysts were characterized by XRD, SEM, N₂ adsorption-desorption isotherm and NH₃-temperature programmed desorption (TPD). The modified SAPO-34 catalysts prepared by varying the added amount of chitosan showed the same cubic morphology and chabazite structure as the conventional SAPO-34 catalyst. As the added amount of chitosan increased to 3 wt%, the surface area, mesopore volume and concentration of weak acid sites of modified SAPO-34 catalysts increased. The modified SAPO-34 catalysts showed enhanced catalytic lifetime and high selectivity for light olefins in the DTO reaction. In particular, the SAPO-CHI 3 catalyst (3 wt%) exhibited the longest catalytic lifetime than that of the conventional SAPO-34. Therefore, it was confirmed that chitosan was a suitable material as a mesopore directing agent to delay deactivation of the SAPO-34 catalyst.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.2
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• pp.141-151
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• 2022

The 16 natural zeolites collected from Mongolia (6 types), the United States (1 type), and Korea (9 types) were characterized by XRD, XRF, TGA, DTA, and CEC analysis. All 16 samples are composite minerals. Two or more mineral phases co-exist and consist primarily of minerals such as clinoptilolite, heulandite, mordenite, and chabazite. In certain samples, minerals like illite and quartz were present as impurities. The XRF analysis showed that the 16 natural zeolites contain SiO₂, Al₂O₃, K₂O, CaO, Na₂O, MgO, and Fe₂O₃ oxides. The cation exchange capacity of the U-1 sample was 223.3 meg/100 g, which is higher than the rest of the samples. M-6 sample in Mongolian natural zeolite and K-1 sample in Korean natural zeolite showed the highest cation exchange capacity at 166.6 meg/100 g. As a result of thermal differential and thermos gravimetric analysis, all 16 samples showed excellent thermal stability up to 600℃.