• 한국재료학회지
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• 제21권8호
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• pp.468-475
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• 2011

[ $LaMeO_3$ ](Me = Cr, Co) powders were prepared using the polymeric precursor method. The effects of the chelating agent and the polymeric additive on the synthesis of the $LaMeO_3$ perovskite were studied. The samples were synthesized using ethylene glycol (EG) as the solvent, acetyl acetone (AcAc) as the chelating agent, and polyvinylpyrrolidone (PVP) as the polymer additive. The thermal decomposition behavior of the precursor powder was characterized using a thermal analysis (TG-DTA). The crystallization and particle sizes of the $LaMeO_3$ powders were investigated via powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and particle size analyzer, respectively. The as-prepared precursor primarily has $LaMeO_3$ at the optimum condition, i.e. for a molar ratio of both metal-source (a : a) : EG (80a : 80a) : AcAc (8a) inclusive of 1 wt% PVP. When the as-prepared precursor was calcined at $700^{\circ}C$, only a single phase was observed to correspond with the orthorhombic structure of $LaCrO_3$ and the rhombohedral structure of $LaCoO_3$. A solid-electrolyte impedance-metric sensor device composed of $Li_{1.5}Al_{0.5}Ti_{1.5}(PO_4)_3$ as a transducer and $LaMeO_3$ as a receptor has been systematically investigated for the detection of NOx in the range of 20 to 250 ppm at $400^{\circ}C$. The sensor responses were able to divide the component between resistance and capacitance. The impedance-metric sensor for the NO showed higher sensitivity compared with $NO_2$. The responses of the impedance-metric sensor device showed dependence on each value of the NOx concentration.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.829-835
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• 2011

A dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) has been developed as a new approach for the extraction of trace copper in water and beverage samples followed by the determination with flame atomic absorption spectrometry. In the DLLME-SFO, 8-hydroxy quinoline, 1-dodecanol, and methanol were used as chelating agent, extraction solvent and dispersive solvent, respectively. The experimental parameters related to the DLLME-SFO such as the type and volume of the extraction and dispersive solvent, extraction time, sample volume, the concentration of chelating agent and salt addition were investigated and optimized. Under the optimum conditions, the enrichment factor for copper was 122. The method was linear in the range from 0.5 to $300\;ng\;mL^{-1}$ of copper in the samples with a correlation coefficient (r) of 0.9996 and a limit of detection of $0.1\;ng\;mL^{-1}$. The method was applied to the determination of copper in water and beverage samples. The recoveries for the spiked water and beverage samples at the copper concentration levels of 5.0 and $10.0\;ng\;mL^{-1}$ were in the range between 92.0% and 108.0%. The relative standard deviations (RSD) varied from 3.0% to 5.6%.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.622-628
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• 2013

Nanocrystalline spinel lithium manganese oxide ($LiMn_2O_4$) powders with narrow-size-distribution, pure-phase particles, and high crystallinity with an average crystallite size of about 70 nm were synthesized at $600^{\circ}C$ for 6 h in air by freeze drying method. Spinel $LiMn_2O_4$ is also prepared by sol-gel using citric acid as a chelating agent. The influence of different parameters such as pH conditions, solvent, molar ratio of citric acid to total metal ions, calcination temperature, starting material on the structure, morphology and purity of this oxide was investigated. The results of sol-gel method show that pure $LiMn_2O_4$ with average crystallite size of about 130 nm can be produced from nitrate salts as starting materials at $800^{\circ}C$ for 6 h in air. The optimum pH and molar ratio of chelating agent to total metal ions are $4{\leq}pH{\leq}6$ and 1.0, respectively. A possible mechanism on the formation of the nanocrystallines synthesized by sol-gel was also discussed. At the end a comparison of the differences between two methods was made on the basis of x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) tests.

• Restorative Dentistry and Endodontics
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• 제42권2호
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• pp.105-110
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• 2017

Objectives: This study investigated the cleaning ability of ultrasonically activated irrigation (UAI) and a novel activation system with reciprocating motion (EC, EasyClean, Easy Equipamentos $Odontol\acute{o}gicos$) when used with a relatively new chelating agent (QMix, Dentsply). In addition, the effect of QMix solution when used for a shorter (1 minute) and a longer application time (3 minutes) was investigated. Materials and Methods: Fifty permanent human teeth were prepared with K3 rotary system and 6% sodium hypochlorite. Samples were randomly assigned to five groups (n = 10) according to the final irrigation protocol: G1, negative control (distilled water); G2, positive control (QMix 1 minute); G3, QMix 1 minute/UAI; G4, QMix 1 minute/EC; G5, QMix 3 minutes. Subsequently the teeth were prepared and three photomicrographs were obtained in each root third of root walls, by scanning electron microscopy. Two blinded and pre-calibrated examiners evaluated the images using a four-category scoring system. Data were statistically analyzed using Kruskal-Wallis and Dunn tests (p < 0.05). Results: There were differences among groups (p < 0.05). UAI showed better cleaning ability than EC (p < 0.05). There were improvements when QMix was used with auxiliary devices in comparison with conventional irrigation (p < 0.05). Conventional irrigation for 3 minutes presented significantly better results than its use for 1 minute (p < 0.05). Conclusions: QMix should be used for 1 minute when it is used with UAI, since this final irrigation protocol showed the best performance and also allowed clinical optimization of this procedure.

• 한국지하수토양환경학회지:지하수토양환경
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• 제23권1호
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• pp.85-91
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• 2018

Arsenic (As) usually is bound to amorphous iron oxides in the soils, and it can be removed via dissolution of iron oxides. Inorganic acid and chelating agent are widely used to extract As in the soil washing. However, the overall performance is highly dependent on the state of As fractionation. In this study, oxalic acid and inorganic acids (HCl, $H_2SO_4$, and $H_3PO_4$) were applied to enhance the dissolution of iron oxides for remediation of As-contaminated soils. Oxalic acid was most effective to extract As from soils and removal of As was two times greater than other inorganic acids. Additionally, 75% of As bound to amorphous iron oxides was removed by 0.2 M oxalic acid. Arsenic removal by oxalic acid was directly proportional to the sum of labile fractions of As instead of the total concentration of As. Therefore, the oxalic acid could extract most As bound to amorphous iron oxides.

• 한국식품과학회지
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• 제19권4호
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• pp.295-299
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• 1987

유안염석과 column chromatography 및 gel여과등으로 비활성이 23.4U/mg이 되는 정제된 mungbean lipoxygenase를 12%의 수율로 얻었다. 정제효소의 작용최적 pH는 8.4이었으며 linoleic acid를 기질로 사용하였을 때 Km값은 0.25mM이었다. 정제효소는 pH $5.0{\sim}7.0$범위와 $50^{\circ}C$이하의 온도에서 비교적 안정하였다. 효소의 활성은 항산화제인 NDGA에 의해 현저히 저해되었고 chelating agents에 의해 저해되었다.

• Nuclear Engineering and Technology
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• 제15권2호
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• pp.117-122
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• 1983

$\beta$-diketo의 관능기를 가진 1-phenyl-3-methyl-4-acyl-pyrazolone-5-one (acyl pyrazolone)이라고 이름지어진 킬레이팅 화합물은 오랫동안 동위원소 분리 및 추출에 이용되어 왔다. 새로운 acylating 물질을 사용해서 만들어진 succinyl, malenyl 그리고 phthalyl pyrazolone이 우라늄이온(VI)과 고가의 산화상태를 지니는 다른 중금속의 추출에 이용되었다. Succinyl pyrazolone이 우라늄(VI) 추출에서 매우 뛰어나다는 것이 밝혀졌으며, 대체로 카르복실 관능기를 가진 킬레이팅 화합물이 우라늄(VI) 혹은 악티나이드 계열의 중금속 추출에 매우 효과적인 것으로 나타났다.

• 대한임상독성학회지
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• 제19권1호
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• pp.59-63
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• 2021

Copper sulfate is widely used as a fungicide and pesticide. Acute copper sulfate poisoning is rare but potentially lethal in severe cases. Copper sulfate can lead to cellular damage of red blood cells, hepatocytes, and myocytes. Toxic effects include intravascular hemolysis, acute tubular necrosis and, rhabdomyolysis. A 76-year-old man presented with vomiting and epigastric pain. He had ingested a copper-containing fungicide (about 13.5 g of copper sulfate) while attempting suicide 2 hours prior to presentation. From day 3 at the hospital, laboratory findings suggesting intravascular hemolysis were noted with increased serum creatinine level. He was treated with a chelating agent, dimercaptosuccinic acid (succimer). His anemia and acute kidney injury gradually resolved with a 19-day regimen of succimer. Our case suggests that succimer can be used for copper sulfate poisoning when other chelating agents are not available.

• 분석과학
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• 제9권3호
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• pp.279-291
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• 1996

미량 금속이온을 선택적으로 분리, 농축 및 회수하기 위해 물리적 특성이 서로 다른 XAD-2, 4 및 16 다공성 수지에 2-(2-thiazolylazo)-p-cresol(TAC) alc 4-(2-thiazolylazo)orcinol(TAO)을 화학적으로 결합시켜 킬레이트 수지를 합성하고 뱃치법으로 U(VI) 등 10개 금속이온들의 흡착 특성을 조사 비교하였다. 킬레이트 수지의 합성률은 XAD-16-TAC형 수지는 0.60 mmol/g이었고 XAD-16-TAO형은 0.68mmol/g으로서 수지의 표면적이 큰 XAD-16형 수지가 XAD-2, 4형 수지보다 높은 합성률을 나타내었다. XAD-16-TAC와 XAD-16-TAO 킬레이트 수지는 1~5M 의 $HNO_3$, HCl 및 NaOH 등의 산과 염기성 용액에서 비교적 안정하였다. 그리고 U(VI) 이온을 10회 이상 반복적으로 흡착 및 탈착을 시킨 결과 연속적으로 재사용할 수 있는 안정한 내구성을 가지고 있음을 확인하였다. XAD-16-TAC 및 XAD-16-TAO형 수지에 대한 금속 이온의 최척 흡착조건과 흡착 특성을 조사한 결과는 금속이온이 킬레이트 수지에 흡착될 때 평형에 도달하는 시간은 약 1시간 정도였으며, XAD-16형 수지에서 흡착률이 가장 높았다. 그리고 금속이온들의 흡착률에 미치는 pH의 영향을 보면 U(VI)을 비롯한 대부분의 금속이온들은 pH 5~6 범위에서 최대로 흡착됨으로써 최척 pH 를 5로 정하였다. 또한 U(VI) 이온의 흡착에 미치는 공존이온의 영향을 보면 음이온인 $Cl^-$, $NO{_3}^-$, ${SO_4}^{2-}$, $CH_3COO^-$ 이온 및 $Na^+$, $K^+$, $Mg^{2+}$ 및 $Ca^{2+}$과 같은 양이온들은 흡착에 거의 영향을 미치지 않았다. 그러나 $CO{_3}^{2-}$는 $UO{_2}^{2+}$와 $[UO_2(CO_3)_3]^{4-}$의 안정한 착물을 형성하므로 U(VI) 이온의 흡착능을 크게 감소시켰다. 선택적인 특정 금속이온의 분리를 위하여 EDTA, CDTA 및 NTA 등과 같은 가리움제를 첨가하여 그 영향을 조사한 결과 NTA에 의한 가리움 효과가 10가지 혼합 금속이온 중 U(VI) 이온에 대하여 가장 큰 것으로 나타났다.

• 한국토양비료학회지
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• 제46권6호
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• pp.665-672
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• 2013

This study was conducted to evaluate the effects of a chelating agent on cucumber growth and changes in soil nutrients availability in polytunnel greenhouse fields. Diethylene triamine penta acetic acid (DTPA) was selected as a chelating agent. Two experiments were carried out as follows: i) For field experiment in the autumn season of 2010, each plot was treated by varying the concentration and the number of times being applied with DTPA; [DTPA (0.5 mM, 1 time/3 months), DTPA (0.06 mM, 1 time/1 week), DTPA (0.13 mM, 1 time/2 weeks), DTPA (0.06 mM, 1 time/1 week)+N]. Conventional practice was also investigated. ii) In the spring and summer seasons of 2011, each plot was treated by varying the concentration (0, 0.06, 0.13, 0.19 mM) of DTPA, chemical fertilizers (NPK), and combination of chemical fertilizers and DTPA 0.06 mM. The fruit yields of cucumber and soil chemical properties had no significant differences between treatments. However, in the spring season of 2011, DTPA 0.06 mM plot added 1 time per 2 weeks increased the yield of cucumber, but caused the reduction of yield in next cultivation season. This result showed that excess use of DTPA can cause the damage of crop growth. The inorgainc contents such as Ca and Mg absorbed by cucumber plant had significant differences between DTPA 0.19 mM (2 times/1 week) and fertilizers plus DTPA treatments [DTPA 0.06 mM (2 times/1 week) + 1/2 NPK, DTPA 0.06 mM (2 times/1 week) + NPK]. The input cost of fertilizers was saved when the concentration and the number of times added with DTPA was 0.06 mM and 1 time a week, respectively. This treatment used 67% less of applied fertilizers cost than the plot of conventional practice did. Thus, this research suggested that the application of DTPA 0.06 mM by 1 time a week can be effective for sustainability of crop production and reduction of fertilizers usage in polytunnel greenhouse.