• Journal of the Korean Chemical Society
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• v.25 no.4
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• pp.275-282
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• 1981

A simple semiquantitative procedure was developed for the determination of sub-ppm level of chromium(VI) in aquatic samples by using an analytical micro-column packed with diphenylcarbazide(DPC) gel beads. DPC gel beads were prepared by swelling XAD-2 resin(115∼150 mesh in dry condition) in ethanol for 10min, packing into a glass column(1.5 mm bore, 65nm length) and adsorbing 1ml of ethanol solution of $2{\times}10^{-3}M$ DPC for 20min at room temperature. When 0.5ml of ethanol solution containing chromium(VI) was passed through the DPC gel column for 40min, the original white color of the reagent gel turned to red-violet from the up-stream of the column. As the length of colored band was proportional to the total amount of chromium(VI) in the sample solution passed through the column, the concentration of chromium(VI) could be determined from the calibration line which had been prepared by using the standard solution. Chromium(VI) ion as small as from 0.1 to 0.8 ppm could be determined with ${\pm}5{\sim}{\pm}15{\%}$ relative errors. Since other interfering cations were few, 100-fold excess of Fe(III), 50-fold excess of Cu(II) could be masked with EDTA. This method was successfully applied to the analysis of chromium(VI) in industrial effluents.

• Bulletin of the Korean Chemical Society
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• v.34 no.8
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• pp.2381-2386
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• 2013

A new series of Mn(II) and Mo(VI) complexes containing the Schiff bases hydrazinecarbothioamide and hydrazinecarboxamide of 5,6-dimethyl-1H-indol-2,3-dione have been synthesized. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, molecular weight determinations and spectral studies viz. electronic IR, ESR, $^1H$ NMR and $^{13}C$ NMR and X-ray diffraction spectral studies. The magnetic moment values of the manganese(II) complexes are in the range of 5.80-6.15 B.M. suggesting a high spin state of manganese in these complexes. The spectral data are consistent with a tetrahedral geometry around Mn(II) and an octahedral geometry for Mo(VI), in which the ligands act as bidentate chelating agents, coordinated through the nitrogen and sulfur/oxygen atoms. The ligands and their metal complexes have been tested against a number of pathogenic fungi and bacteria at different concentrations and were found to possess sufficient fungicidal and bactericidal properties. Further, the complexes were also tested for their antifertility activity in male albino rats and the results were indeed positive.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.7 no.1
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• pp.71-78
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• 1969

To study the varietal differences of vegetative organs, yield and yield components along the periodical changes of rice variety in korea, this experiment was conducted in 1968. Eighteen used varieties were grouped into 6 varietal groups by the cultivated period as follow.: 1) Group I - Korean local varieties cultivated about 1907, 2) Group II - introduced varieties cultivated in 1907 - 1930, 3) Group III - introduced varieties cultivated in 1930-1960, 4) Group IV - improved varieties cultivated in 1930-1960, 5) Group V - introduced varieties cultivated after 1960 and 6) Group VI - improved varieties cultivated after 1960. 1. Varietal Group I showed the longest leaves, the largest leaf area, the lowest value of leaf area index and the highest value of flag leaf angle. Along the periodical changes of rice varieties the leaf length, the total leaf area and the flag leaf angle were decreased, and the leaf area index was increased. 2. Varietal Group I showed higher value of the length and the weight of leaf sheath than those of Group II, III, IV, V and VI. The length of every internode was longer in Group I than in the other varietal groups. The weight of every internode was shown higher value in Group 1. The length and the weight of every internode were decreased along the periodical changes of rice variety. 3. Varietal Group I and Group III showed the higher value of culm length, panicle length and the number of grain per panicle length and groups. Group IV, V and VI had the higher value of the number of panicle, the maturing rate and the 1, 000 grains weight. Varietal Group V and VI which are cultivated in recent years showed shorter culm and panicle length, higher value of the maturing rate and the 1, 000 grains weight, and intermediate in the number of panicle and the number of grain per panicle. 4. The lowest value of straw weight was found in Group I. The highest value of grain yield was shown in Group VI, intermediate in Group II, III, IV and V and lowest in Group I. Grain-straw ratio was shown highest in Group VI.

• Analytical Science and Technology
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• v.9 no.3
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• pp.279-291
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• 1996

The new chelating resins, XAD-2, 4, 16-TAC and XAD-2, 4, 16-TAO were synthesized by Amberlite XAD-2, XAD-4, and XAD-16 macroreticular resins with 2-(2-thiazolylazo)-p-cresol(TAC) and 4-(2-thiazolylazo)orcinol(TAO) as functional groups and were characterized by elemental analysis and FT-IR spectrometry. It was found that the content of functional group in chelating resin was 0.60mmol/g in XAD-16-TAC and 0.68mmol/g in XAD-16-TAO respectively. The chelating resins were stable in acidic and alkaline solution and can be reused over 10 times. The sorption behavior of some metalions to two chelating resins was investigated by batch method, which included batch equilibrium, effect of pH, coexisting ions and masking agent. For the optimum condition of sorption, the time required for equilibrium was about 1 hour and optimum pH was 5. In the presence of anions such as ${SO_4}^{2-}$ and $CH_3COO^-$, the sorption of U(VI) ion was slightly reduced but other anions such as $Cl^-$ and $NO{_3}^-$ revealed no interference effect. Also, sorption capacity of U(VI) ion was decreased by addition of $CO{_3}^{2-}$ ion because of complex formation of $[UO_2(CO_3)_3]^{4-}$, but alkali metals and alkali earth metals including Na(I), K(I), Mg(II), and Ca(II) were not affected for the sorption extent. Masking agent, NTA showed better separation efficiency of U(VI) ion from coexisting metal ions such as Th(IV), Zr(IV), Hf(IV), Cu(II), Cd(II), Pb(II), Ni(II), Zn(II) and Mn(II) than EDTA, CDTA.

• Textile Coloration and Finishing
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• v.17 no.1
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• pp.20-29
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• 2005

Cotton fabric was treated with a reactive anionic agent in order to have anionic sites(-S03-) on it, which made it possible for the fabric to adsorb various cationic materials. In this study, the adsorptivity of various heavy metal ions such as Pb(II), Cd(II), Cr(III), Co(II), Cu(II), Ni (II) and Cr(VI) on the cotton fabrics treated with anionic agent was examined at the various conditions; concentrations of heavy metal ions, pHs of solution, reaction time and temperature. As a result, the adsorptivity of the heavy metal ions on the cotton fabrics treated with the anionic agent was highly increased comparing to that of untreated cotton fabrics. The order of the adsorptivity was as follows: $Pb(II)>Cd(II)>Cu(II)\geqNi(II)\geqCo(II)>Cr(III)\ggCr(VI)$. The adsorption amounts of most heavy metal ions were increased in weak alkaline conditions and were reached to an adsorption equilibrium within 10 ~ 30 minutes. The maximum adsorption ratios of Pb(II) and Cd(II) were respectively 99% and 80% of the initial concentration of heavy metal ions. Therefore the anionized cotton fabrics seem to be utilized as an adsorption fabrics for the removal of heavy metal ions in the waste water.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.3
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• pp.398-407
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• 2007

This study was performed to evaluate possibility to reduce treatment time for child patient who have limited control activity during flowable composite resin restoration according to comparing microleakage and shear bond strength. Group I, II with Single $Bond^{TM}$, group III, IV with AQ Bond $Plus^{TM}$, group V, VI with Prompt L-$Pop^{TM}$, and group VII as control group without adhesive system. 12 premolars and 10 molars were assigned into each group. Restorative material was used the Filtek $Z350^{TM}$ flowable. The results were as follows; 1. The result of microleakage evaluation, in the group I, II with Single $Bond^{TM}$ showed low dye penetration score. Dye penetration between group I and group II were similar. 2. Results for shear bond strength at group I and group II showed values higher than other groups. (p<0.05) There were no statistical differences between group I and group II. (p>0.05) 3. There was no statistical differences among I and II, III and IV, V and VI groups. 4. Group VII showed significantly low shear bond strength than group I, II, V, VI(p<0.05). Group VII showed low value than group with III and IV, but no statistical significances. In conclusion, adhesive bonding resin was not affect significantly to microleakage and shear bond strength of flowable resin restoration. Therefore, to reduce the operation time, adhesive bonding resin and flowable composite resin can be cured at once. But contamination of saliva, location of cavities can affect to bond strength in clinical field.

• Landscaping Tree
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• v.47 no.11_12
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• pp.4-10
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• 1998

• Carbon letters
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• v.8 no.4
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• pp.280-284
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• 2007

Samples of active carbon of $1150\;m^2/g$ surface area were impregnated with ammoniacal salts of copper, chromium and silver, with and without triethylenediamine. The samples of impregnated carbon were aged at $50^{\circ}C$, with and without 90% RH (relative humidity), for a little more than one year and chemically evaluated periodically. Initially copper (II) and chromium (VI) reduced very fast in the samples in humid atmosphere to the extent of 30% and 60% respectively in four months. These values were found to be unaffected by the presence of triethylenediamine (TEDA) indicating that the chemical did not retard the reduction process of chromium (VI) and copper (II). However, in the absence of humidity the reduction of the impregnants was significantly less (10-12%, w/w) in four months. It was quite evident; therefore, that the moisture was mainly responsible for the reduction of chromium (VI) and copper (II) species in impregnated carbons. The prolonged ageing of the samples with and without triethylenediamme after four months with and without humid atmosphere showed that the extent of reduction of chromium (VI) was very low, i.e. 5-10% and of copper (II) was 2-25%. Silver is not reduced due to carbon, as it remained unchanged in concentration on storage. The impregnated carbon samples (100 g) without triethylenediamine, which were aged at room temperature for 5 years in absence of humidity and unaged when evaluated against cyanogen chloride (CNCl) at a concentration of 4 mg/L and airflow rate of 30 lpm showed a high degree of protection (80- 110 minutes).

• Analytical Science and Technology
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• v.19 no.4
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• pp.280-284
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• 2006

The objective of this study is to investigate the removal of heavy metal by using the coprecipitation of barium sulfate. Several parameters governing the efficiency of the coprecipitation method were evaluated by the pH of sample solution, amount of coprecipitant, and addition of sulfide for the removal of As(V), Cd(II), Cr(III), Cr(VI), Cu(II), Hg(II) and Pb(II) metal ions ($10{\mu}g/ml$ each). The coprecipitation was about 80% - 95% only for lead at low pH but under 10% for other ions. The amount of removal was about 95% - 100% for Cd, Hg, Pb, Cu in the all pH range by the addition of sulfide with barium sulfate but As(V) and Cr(III, VI) ions were not affected by the same conditions.

• Environmental Engineering Research
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• v.22 no.1
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• pp.95-107
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• 2017

Adsorption equilibrium and kinetic behavior of two toxic heavy metals hexavalent chromium [Cr(VI)] and mercury [Hg(II)] on mustard oil cake (MOC) was studied. Isotherm of total chromium was of concave type (S1 type) suggesting cooperative adsorption. Total chromium adsorption followed BET isotherm model. Isotherm of Hg(II) was of L3 type with monolayer followed by multilayer formation due to blockage of pores of MOC at lower concentration of Hg(II). Combined BET-Langmuir and BET-Freundlich models were appropriate to predict Hg(II) adsorption data on MOC. Boyd's model confirmed that external mass transfer was rate limiting step for both total chromium and Hg(II) adsorptions with average diffusivity of $1.09{\times}10^{-16}$ and $0.97m^2/sec$, respectively. Desorption was more than 60% with Hg(II), but poor with chromium. The optimum pH for adsorptions of total chromium and Hg(II) were 2-3 and 5, respectively. At strong acidic pH, Cr(VI) was adsorbed by ion exchange mechanism and after adsorption reduced to Cr(III) and remained on MOC surface. Hg(II) removal was achieved by complexation of $HgCl_2$ with deprotonated amine ($-NH_2$) and carboxyl (COO-) groups of MOC.