• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.159-168
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• 2022

Catalytic activity in ammonia decomposition reaction was studied on Mo-Al nitride obtained through temperature programmed nitridation of calcined Mo-Al mixed oxide prepared by varying the MoO₃ quantity in the range of 10-50 wt%. N₂ sorption analysis, X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and H₂-temperature programmed reduction (H₂-TPR), and transmission electron microscopy (TEM) to investigate the physicochemical properties of the prepared catalyst were performed. After calcination at 600 ℃, the XRD of Mo-Al oxide showed γ-Al₂O₃ and Al₂(MoO₄)₃ phases, and the nitride after nitridation showed an amorphous form. The specific surface area after nitridation by topotactic transformation of MoO₃ to nitride was increased due to the formation of Mo nitride, and the Mo nitride was observed to be supported on γ-Al₂O₃. As for the catalytic activity in the ammonia decomposition reaction, 40 wt% MoO₃ showed the best activity, and as the nitridation time increases, the activity increased, and thus the activation energy decreased.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.581-587
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• 2022

The leather industry generates a large amount of hazardous leather waste of various types every year. Among them, shaving scrap is difficult to recycle because it contains chromium ions. Many studies in recent years have shown that shaving scraps can be processed into various types of valuable products, such as adsorbent, filler, and poultry feed. In this study, collagen peptides were extracted from shaving scraps and structurally modified to be developed as new materials with improved physicochemical properties. First, the chromium ions contained in the shaving scraps were removed using a sodium hydroxide solution, and purified through concentration and low-temperature crystallization. The purified collagen peptide was used to prepare the powder using a spray dryer. The extracted collagen peptides were structurally modified by introducing double bonds by reacting with methacrylic anhydride (MAA), and the product was confirmed by ¹H NMR spectroscopy. Next, a copolymer was prepared by redox polymerization of the modified collagen peptide (MCP) and 2-ethylhexyl acrylate (2-EHA). The structure of the copolymer was qualitatively confirmed by FT-IR. In conclusion, this study confirmed that collagen peptides can be extracted from shaving scrap and converted into new eco-friendly materials through certain treatments.

• Economic and Environmental Geology
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• v.55 no.3
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• pp.219-229
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• 2022

Bentonite is being considered as a candidate for buffer material in geological disposal systems for high-level radioactive wastes. In this study, the effect of cement-bentonite interactions on bentonite alteration was investigated by reviewing the literature on studies of cement-bentonite interactions. The major bentonite alteration by hyperalkaline fluids produced by the interaction of cementitious materials with groundwater includes cation exchange, montmorillonite dissolution, secondary mineral precipitation, and illitization. When the hyperalkaline leachate from the reaction of the cementitious material with the groundwater comes into contact with bentonite, montmorillonite, the main component of bentonite, is dissolved and a small amount of secondary minerals such as zeolite, calcium silicate hydrate, and calcite is produced. When montmorillonite is continuously dissolved, the physicochemical properties of bentonite may change, which may ultimately causes changes in bentonite performance as a buffer material such as adsorption capacity, swelling capacity, and hydraulic conductivity. In addition, the bentonite alteration is affected by various factors such as temperature, reaction period, pressure, composition of pore water, bentonite constituent minerals, chemical composition of montmorillonite, and types of interlayer cations. This study can be used as basic information for the long-term stability verification study of the buffer material in the geological disposal system for high-level radioactive wastes.

• Journal of Conservation Science
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• v.37 no.6
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• pp.748-766
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• 2021

The Iksan Ssangneung (twin tombs), a pair of tombs comprising the Daewangneung (large royal tomb) and the Sowangneung (small royal tomb), were constructed in the typical style of stone tunnel and chamber tombs in the Baekje Kingdom during the Sabi period (538 to 660 AD) of ancient Korea. Soil layers exposed during excavation of Sowangneung in a trench east of the tomb are: the bottommost layer, the ground level layer, the Panchuk (rammed earth) layer of the Baekje, the layer created by a grave robbery, and soil recovered during the Japanese colonial period. Soil samples were obtained by segmenting an easy stratigraphic horizon into sub categorized soil layers, and their material properties were analyzed; they are composed mainly of sandy loam based on the particle size distributions. In the site foundation, loamy sand is packed in the bottommost layer, and sandy loam with high sand and silty sand fills most of the overlying layer. The central and topmost portion of the Baekje layer is composed of loam with high clay content. All soil layers show geochemical behaviors similar to those of the bottommost layer. X-ray diffraction analysis verified kaolinite in all layers, also observed in soil layers displaying high crystallinity. Kaolinite and halloysite were identified by scanning electron microscopy. Thus, we conclude that the Baekje layer of the Sowangneung is composed of sandy loam containing kaolin procured from near the site. An impermeable middle to upper layer was created using viscous loam. The top of the tomb was closed tightly.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.459-467
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• 2022

Redispersion of Pt-Sn particles in Pt, PtSn catalyst which have been sintered by high temperature hydrogen reduction was investigated using oxygen treatment with various temperatures. The aim of this study was to understand the relationship between the catalytic activity for propane dehydrogenation reaction and the change in the physicochemical properties of the catalyst. X-ray diffraction analysis (XRD), CO pulse chemisorption, and H₂ temperature programmed reduction (H₂-TPR) were performed to investigate the state of active metal and interactions between particles of redispersed catalyst. It was confirmed that the dispersion and particle size of platinum, the crystal phase of the catalyst, and the reduction behavior were changed according to the oxygen treatment. As for the catalytic activity in propane dehydrogeantion, sintered PtSn catalyst treated with oxygen at 500 ℃ showed best activity and recovery of initial activity. It was confirm that catalyst after oxygen treatment at 500 ℃ showed high dispersion of Pt and decreased particle size as the results of CO pulse chemisorption and XRD of catalyst, and thus the redispersion of PtSn particles in sintered catalyst was occurred. Catalytic activity was recovered due to redispersion using oxygen treatment, and the activity recovery of the PtSn catalyst was higher than that of Pt catalyst.

• Economic and Environmental Geology
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• v.55 no.4
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• pp.389-398
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• 2022

Many studies have been conducted to accurately predict the correlations between As and heavy metals content in contaminated soil and cultivated crops; however, due to the low correlation between the two, few clear results were obtained to date. This study aimed to create statistical models that predict the As content transferred from soil to polished rice, considering the physicochemical properties of the soil, as well as the total content and the single-extracted content of As in the soil. Predictive models were derived through regression analysis while sequentially classifying soil samples according to pH, soluble As content by single extraction, and organic matter content of the soil. The correlation coefficients between the As content in 80 polished rice and total As content and Mehlich soluble As content in the soil were low, 0.533 and 0.493, respectively. However, the models derived after sequential classification of the soil by pH, a ratio of total As content to Mehlich soluble As content, and organic matter content greatly increased the predictive power; ① 0.963 for 13 soils with a pH higher than 6.5, ② 0.849 for 15 soils with pH lower than 6.5 and a high ratio of As_Tot/As_Mehlich, ③ 0.935 for 30 soils with pH lower than 6.5, a high ratio of As_Tot/As_Mehlich, and organic matter content lower than 8.5%. The suggested prediction model of As transfer from soil to polished rice derived by soil classification may serve as a statistically significant methodology in establishing a rice cultivation standard for arsenic-contaminated soil.

• Korean Journal of Food Science and Technology
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• v.54 no.4
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• pp.445-454
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• 2022

This study aimed to improve the physiological activity of onion juice via lactic acid bacterial fermentation. Seven types of lactic acid bacteria were used for the fermentation of onion juice. The pH and sugar content of the onion juice decreased, while its titratable acidity increased after lactic acid bacteria fermentation, and the cell count of lactic acid bacteria was 7.31-10.40 log CFU/mL. The total free sugar content decreased, while the total organic acid content increased in the fermented onion juice. Quercetin content of the fermented juice was 0.13-0.53 mg/kg. The total polyphenol and flavonoid contents increased after fermentation. Additionally, the 2,2-diphenyl-1-picryl-hydrazyl-hydrate free radical and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) radical cation scavenging activities were increased by fermentation. Overall, lactic acid bacteria fermentation of onion juice enhanced its physiological activity. Based on these findings, Bifidobacterium breve KCTC 3441 was selected as the onion juice fermentation strain.

• Korean Journal of Food Science and Technology
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• v.54 no.4
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• pp.422-430
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• 2022

The effects of phytase and cellulase treatment on the bioavailability of iron, calcium, and zinc in whole wheat flour and their food applications were evaluated in this study. Whole wheat flour was treated with phytase and cellulase either individually or in combination and incubated at 50℃ for 2 h; the concentrations used for the individual enzymes were 2%, 10%, and 20%. The concentration of the combination enzyme was 20% with a mixing ratio of 5:5. Total dietary fiber and phytate contents were reduced as the concentrations of phytase and cellulase increased. The bioavailability of iron, calcium, and zinc was notably improved after in vitro digestion in 20% cellulase, combination enzyme, and 20% phytase, respectively. Muffins made with cellulase- and phytase-treated whole wheat flour showed improved quality and bioavailability of minerals. Phytase- and cellulase-treated whole wheat flour may be useful for development of functional food products with improved bioavailability of minerals.

• Journal of Life Science
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• v.32 no.9
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• pp.698-705
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• 2022

Rice consumption in Korea is continuously decreasing; therefore, methods for reducing rice stocks are now being proposed. Increasing the consumption of rice and reduce these stocks will require that the rice processing industry be developed beyond simply using cooked rice as food. The Korean people's eating habits have also diversified recently, and the consumption of bread is increasing. Therefore, breeding a cultivar for rice flour is now necessary. Here, a line suitable for processing into rice flour was cultivated by deriving a mutant line by tissue culture of Ilpum. Mutant populations were investigated for major agricultural traits in the field, and grain characteristics and endosperm characteristics were investigated after harvest. Among the lines, line 29111 had similar agricultural characteristics to the background Ilpum, and excellent grain quality, and was selected for further analysis. The physicochemical properties that determine taste were similar or improved. However, unlike Ilpum, 29111 had a non-uniform starch structure and a characteristic powdery endosperm because large and male starch grains are evenly distributed. Therefore, 29111 was viewed as a breeding line suitable for processing and for excellent agricultural characteristics and taste. The added value can be increased by diversifying the uses of rice. The taste was improved and a method for breeding cultivars with grain characteristics for glutinous rice that would satisfy both producers and consumers was presented.

• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.202-209
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• 2022

Effects of the support and amount of NiCl₂ on ammonia adsorption capacity were investigated to improve the ammonia adsorption performance. NiCl₂ was impregnated onto the surface of various supports under ultrasonic irradiation. The physicochemical properties and ammonia adsorption performance of NiCl₂-impregnated adsorbents were investigated. Among the various supports, it was found that the adsorption capacity of ammonia was the best when NiCl₂ was impregnated on activated carbon (AC) with the highest specific surface area. As a result of changing the amount of NiCl₂ impregnated on AC, the NiCl₂(2.0)/AC adsorbent impregnated with 2 mmol·g^-1 of NiCl₂ showed the highest ammonia adsorption capacity of 5.977 mmol·g^-1. In addition, the adsorption capacity was found to be maintained at an almost constant level in five repeated cycle tests under the condition that low-temperature heat could be utilized. This indicates that the adsorbent has excellent regeneration ability.