• Economic and Environmental Geology
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• v.11 no.3
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• pp.89-98
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• 1978

Mineralogy, beneficiation, and processes of titanium ores are reviewed from petrographic viewpoints. The most important titanium minerals are ilmenite ($FeTiO_3$) and rutile ($TiO_2$). Ilmenite will play major role :for raw material, because rutile are rapidly diminishing. Thus, there is a need to develope a successful process for producing high grade Ti02 from ilmenite. Commercial, as well as R and D processes to treat more abundant ilmenite ores fall in three general classess: 1. Iron in ilmenite is partially or completely reduced and separated either physically or chemically. 2. Iron is reduced to ferrous state and chemically leached away from the titanium. 3. Ore is treated to make chlorides either selectively or with subsequent separation and purification of $TiC_4$. Routes and efficiencies of these process technologies are primarily influenced by the particular ore deposit to be mined and secondly by environmental considerations. One deposit parameters which influence ilmenite process technologies are: 1. Complexity of microtextures of ilmenite intergrown with Fe-oxide minerals. 2. Composition of concentrates; ilmenites contain minor amounts of substituted Mg, Mn, and V. These elements plus iron and gangue minerals can cause difficulties to complete reactions, substantial acid consumption, difficulties of removing waste solids, and waste disposal problems. Major contributions to be made by petrologists for process optimization are: characterization and interpretation of compositional and physical changes of raw materials and solids derived from process streams. These informations can play significant role in selecting and improving process steps for titania production.

• Korean Journal of Food Science and Technology
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• v.49 no.5
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• pp.494-501
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• 2017

Waffles with cinnamon powder added in different proportions (0-12% of wheat flour) were baked to investigate the effects of baking on the physicochemical properties and antioxidant activity. Compared with the control without cinnamon, baking loss was lower in waffles with cinnamon, which led to a decrease in waffle hardness. This was attributable to the higher water-holding capacity of cinnamon than wheat flour. With the increase in the amount of cinnamon, the springiness, resilience, and cohesiveness of the waffle decreased, which was thought to result from the decrease in gluten formation by the proportional decrease of wheat flour. The total reducing capacity and DPPH radical scavenging activity of the waffle was significantly increased. This was substantially in agreement with the observations that cinnamon had an appreciable total reducing capacity and radical scavenging activity that were unchanged by heat treatment. This indicates that the antioxidant functionality of cinnamon could be effectively added to thermally processed food.

• Resources Recycling
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• v.13 no.5
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• pp.28-36
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• 2004

The extraction of platinum group metals such as Pt, Pd and Rh from spent automobile catalyst has been investigated by leaching in HCl solutions using $HNO_3$ or NaOCl as a oxidant. The effect of type and amount of oxidant, reaction time and pulp density on the extraction of platinum group metals was examined. Platinum group metals were recovered by the cementation method using aluminum as a reducing agent. The extraction ratio was higher when NaOCl was used as a oxidant. The optimum leaching conditions were obtained to be: HCl 8 M, the amount of NaOCl 1.4 mole, leaching temperature $90^{\circ}C$, leaching time 180 minutes, pulp density 400g/L. Under the optimum conditions, the extraction of Pt, Pd and Rh were 96.1%, 93.6% and 77.3%, respectively. With the addition of 2.0g of aluminum which corresponds to 28 equivalent the reduction were 98% for Pt. 98.8% for Pd and 65.3% for Rh, respectively.

• Journal of the Korean Chemical Society
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• v.66 no.2
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• pp.124-135
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• 2022

The purpose of this study was to analyze the chemisry education contents of South Korea and North Korea for understanding chemistry education of North Korea. Chemistry education in South and North Korea was investigated in terms of learning period and learning quantaty. Especially, what content North Korea learned prior to South Korea and what contents learned more were analyzed. The subjects of this study were South Korean 2015 revised National Science Curriculum and North Korean science textbooks in Kim Jong-un era. The North Korean textbooks analyzed are 'Nature' for North Korean elementary school 3, 'Natural Science' for North Korean middle school 1 and 2, and 'Chemistry' for North Korean high school 1 and 2. The analysis results are as follows. First, the content elements to be learned in advance in North Korean textbooks were density, oxidation and reduction, battery, and atomic weight. Second, the content elements additionally learned in North Korean textbooks include separation of mixtures, fuels, oxidation and reduction, metals, organic and inorganic substances, metals and non-metal oxides and hydroxides, inorganic substances used as fertilizers, nutritional substances, and salt reaction and utilization, atomic orbitals, hybridization of orbitals, coordination bonds and complexes. As a future research task, a qualitative analysis of the elements of North Korean chemistry, the activities of textbooks, and an experimental analysis were proposed.

• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.188-194
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• 2022

This work presents a non-destructive and straightforward approach to assemble a large-scale conductive electronic film made of a pre-treated single-walled carbon nanotube (SWCNT) solution. For effective electron transfer between the immobilized enzyme and SWCNT electronic film, we optimized the pre-treatment step of SWCNT with p-terphenyl-4,4"-dithiol and dithiothreitol. Glucose oxidase (GOx, a model enzyme in this study) was immobilized on the SWCNT electronic film following the positively charged polyelectrolyte layer deposition. The glucose detection was realized through effective electron transfer between the immobilized GOx and SWCNT electronic film at the negative potential value (-0.45 V vs. Ag/AgCl). The SWCNT electronic film-based glucose biosensor exhibited a sensitivity of 98 ㎂/mM·cm². In addition, the SWCNT electronic film biosensor showed the excellent selectivity (less than 4 % change) against a variety of redox-active interfering substances, such as ascorbic acid, uric acid, dopamine, and acetaminophen, by avoiding co-oxidation of the interfering substances at the negative potential value.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.296-302
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• 2024

An ionic conjugated polymer-iron (III) chloride composite was prepared via in-situ quaternization polymerization of 2-ethynylpyridine (2EP) using iron (III) chloride. Various instrumental methods revealed that the chemical structure of the resulting conjugated polymer (P2EP)-iron (III) chloride composite has the conjugated backbone system having the designed pyridinium ferric chloride complexes. The polymerization mechanism was assumed to be that the activated triple bond of 2-ethynylpyridinium salt, formed at the first reaction step, is easily susceptible to the step-wise polymerization, followed by the same propagation step that contains the propagating macroanion and monomeric 2-ethynylpyridinium salts. The electro-optical and electrochemical properties of the P2EP-FeCl₃ composite were studied. In the UV-visible spectra of P2EP-FeCl₃ composite, the absorption maximum values were 480 nm and 533 nm, and the PL maximum value was 598 nm. The cyclic voltammograms of the P2EP-FeCl₃ composite exhibited irreversible electrochemical behavior between the oxidation and reduction peaks. The kinetics of the redox process of composites were found to be very close to a diffusion-controlled process from the plot of the oxidation current density versus the scan rate.

• Journal of the Korean Electrochemical Society
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• v.5 no.2
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• pp.52-56
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• 2002

Tin oxide was coated on graphite particle by sol-gel method and an electrode with this material having microcrystalline structure for lithium ion battery was obtained by heat treatment in the range $400-600^{\circ}C$. The content of tin oxide was controlled within the range of $2.25wt\%\~11.1wt\%$. The discharge capacity increased with the content of tin oxide and also initial irreversible capacity increased. The discharge capacity of tin oxide electrode showed more than 350 mAh/g at the initial cycle and 300 mAh/g after the 30th cycle in propylene carbonate(PC) based electrolyte whereas graphite electrode without surface modification showed 140 mAh/g. When the charge and discharge rate was changed from C/5 to C/2, The discharge capacity of tin oxide and graphite electrode showed $92\%\;and\;77\%$ of initial capacity, respectively. It has been considered that such an enhancement of electrode characteristics was caused because lithium $oxide(Li_2O)$ passive film formed from the reaction between tin oxide and lithium ion prevented the exfoliation of graphite electrode and also reduced tin enhanced the electrical conduction between graphite particles to improve the current distribution of electrode.

• Journal of the Korean Society of Food Science and Nutrition
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• v.16 no.1
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• pp.1-9
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• 1987

Large amount of aflatoxin $B_1(AFB_1)$ is disappeared in the presence of L-ascorbic acid(AA) in buffer solution at pH values from 1 to 7 during 5 days of Incubation at $37^{\circ}C$. $AFB_1$ was quite stable at pH's between 5 and 7 when AA was absent(control), however, $50{\sim}60%$ of APB, was degraded in its presence after 5 days. The rate of disappearance of $AFB_1$ increased with a decreasing of pH in the presence of AA, even though $AFB_1$ in the control degraded increasingly with the decrease in $pH(pH{\leq}4)$. The level of $AFB_1$, decreased as the reaction temperature increased when $AFB_1$ reacted with AA. The aflatoxin could not be detected at all after 3 days when the reaction occurred at $60^{\circ}C$, while the aflatoxin was stable at $5^{\circ}C$ thoughout the reaction period. $90{\sim}96%$ of $AFB_1$ was found to be degraded in a far when $AFB_1$ reacted with AA plus different concentrations of $CuSO_4{\cdot}5H_{2}O$, showing remarkably faster rate than the control; however, different concentrations of L-cysteine instead of $CuSO_4\;5H_{2}O$ protected the degradation of aflatoxin and no $AFB_1$ was degraded for a day and resulted in less $AFB_1$ disappeared than the control. The degradation of $AFB_1$ was dependent on AA concentration and the rate of disappearance as the concentration of AA decrease, but $AFB_1$ concentration did not influence the rate. The product formed when $AFB_1$ reacted with AA was identified to $AFB_{2a}$ by using HPLC chromatographic examinations, and by UV spectrum of $AFB_1$ reacted with AA. The disappearance of $AFB_1$ was correlated well in the appearance of $AFB_2a$. From the results, the degradation of $AFB_1$ in the presence of AA is probably due to one or more of the oxidative products of AA which was produced during the AA oxidation.

• Clean Technology
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• v.21 no.3
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• pp.200-206
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• 2015

In order to investigate the effect of cerium oxide addition, Cu-ZnO-CeO₂ catalysts were prepared using co-precipitation method for water gas shift (WGS) reaction. A series of Cu-ZnO-CeO₂ catalyst with fixed Cu Content (50 wt%, calculated as CuO) and a given ceria content (e.g., 0, 5, 10, 20, 30, 40 wt%, calculated as CeO₂) were tested for catalytic activity at a GHSV of 95,541 h^-1, and a temperature range of 200 to 400 ℃. Cu-ZnO-CeO₂ catalysts were characterized by using BET, SEM, XRD, H₂-TPR, and XPS analysis. Varying composition of Cu-ZnO-CeO₂ catlysts led the difference characteristics such as Cu dispersion, and binding energy. The optimum 10 wt% doping of cerium facilitated catalyst reduction at lower temperature and improved the catalyst performance greatly in terms of CO conversion. Cerium oxide added catalyst showed enhanced activities at higher temperature when it compared with the catalyst without cerium oxide. Consequently, ceria addition of optimal composition leads to enhanced catalytic activity which is attributed to enhanced Cu dispersion, lower binding energy, and hindered Cu metal agglomeration.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.10
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• pp.1525-1532
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• 2013

The objective of this study was to investigate the effect of hot water extract from Cornus walteri Wanger (CWE) on tert-butyl hydroperoxide (TBHP)-induced oxidative stress in HepG2 cells. Generation of reactive oxygen species (ROS), concentrations of cellular lipid peroxidation products and reduced glutathione, and antioxidant enzyme activity were used as biomakers of cellular oxidative status. Cells pretreated with CWE (25~200 ${\mu}g/mL$) showed an increased resistance to oxidative stress in a dose-dependent manner, as revealed by a higher percentage of surviving cells compared to control cells. ROS generation induced by TBHP was significantly reduced when cells were pretreated with 200 ${\mu}g/mL$ CWE for 4 h. Pretreatment with CWE (5~50 ${\mu}g/mL$) prevented the decrease in reduced glutathione and the increase in malondialdehyde and ROS evoked by TBHP in HepG2 cells. Finally, CWE pretreatments prevented the significant increase of glutathione peroxidase, catalase, glutathione reductase, and superoxide dismutase activities induced by TBHP. These results show that CWE has significant protective ability against a TBHP-induced oxidative insult and that the modulation of antioxidant enzymes by CWE may have an important antioxidant effect on TBHP-induced oxidative stress in HepG2 cells.