• Advances in environmental research
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• 제5권2호
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• pp.141-151
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• 2016

Large amounts of aluminum hydroxide ($Al(OH)_3$) exist in water purification sludge (WPS) because of the added aluminum coagulant in water treatment process. Notably, $Al(OH)_3$ is an amphoteric compound, can be dissolved in its basic condition using sodium hydroxide to form aluminate ions ($Al(OH)_4{^-}$). However, in a process in which pH is increasing, the humid acid can be dissolved easily from WPS and will inhibit the recovery and reuse of the dissolved aluminate ions. This study attempts to fix this problem by a novel approach to separate $Al(OH)_4{^-}$ ions using nanofiltration (NF) technology. Sludge impurity in a alkaline solution is retained by the NF membrane, such that the process recovers $Al(OH)_4{^-}$ ions, and significantly decreases the organic matter or heavy metal impurities in the permeate solution. The $Al(OH)_4{^-}$ ion is an alkaline substance. Experimental results confirm that a recovered coagulant of $Al(OH)_4{^-}$ ion can effectively remove kaolin particles from slightly acidic synthetic raw water.

• Korean Chemical Engineering Research
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• 제57권3호
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• pp.378-386
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• 2019

이 논문에서는 염수 중 이온 농축을 위해 진공 증발법과 하이드레이트 활용법 적용시 소모 에너지를 계산 결과를 보고하고자 한다. 상온 상압의 염수(NaCl 농도 0.35 wt%) 1 mol/s 를 10배 농축할 경우를 가정하여 $69^{\circ}C$, 30 kPa 조건에서 진공 증발시와 객체가스로 $CH_4$, $CO_2$, $SF_6$ 를 사용한 하이드레이트 기반 기술의 에너지 소모량을 계산하였다. 진공 증발시 소모 에너지는 약 47 kJ/mol 이었으며, $CH_4$, $CO_2$, $SF_6$ 하이드레이트 공정을 적용할 경우에는 각각 43, 32, 28 kJ/mol의 에너지가 필요하였다. 에너지 소모량 관점에서 이온 농축시 하이드레이트 활용방법은 경쟁력있는 기술이 될 수 있으나, 객체가스에 따라 수화수(hydration number), 수화에너지, 압축에너지 등이 달라지므로 적절한 객체가스의 선정이 매우 중요한 요소라고 판단된다. 하이드레이트를 이용한 용존 이온 농축 기술의 상용화를 위한 핵심 요소로는 객체가스의 선정, 하이드레이트와 농축수의 효과적 분리, 하이드레이트 형성 속도 향상을 들 수 있다.

• Bulletin of the Korean Chemical Society
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• 제22권2호
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• pp.205-209
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• 2001

Uniformly-doped silicon thin films were fabricated by ion beam sputter deposition. The thin films had four levels of copper dopant concentration ranging between 1 ${\times}$1019 and 1 ${\times}$ 1021 atoms/cm3 . Concentrations of Copper dopants were determined by the isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) to provide certified reference data for the quantitative surface analysis by secondary ion mass spectrometry (SIMS). The copper-doped thin films were dissolved in a mixture of 1 M HF and 3 M HNO3 spiked with appropriate amounts of 65 Cu. For an accurate isotope ratio determination, both the detector dead time and the mass discrimination were appropriately corrected and isobaric interference from SiAr molecular ions was avoided by a careful sample pretreatment. An analyte recovery efficiency was obtained for the Cu spiked samples to evaluate accuracy of the method. Uncertainty of the determined copper concentrations, estimated following the EURACHEM Guide, was less than 4%, and detection limit of this method was 5.58 ${\times}$ 1016 atoms/cm3.

• Bulletin of the Korean Chemical Society
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• 제17권4호
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• pp.338-342
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• 1996

A sensitive method for the determination of trace cadmium after the preconcentration by extracting its 8-hydroxyquinoline complex into a molten benzophenone was developed. Several experimental conditions such as the pH of solution, the amounts of 8-hydroxyquinoline and benzophenone, stirring time, and standing time were optimized. Trace cadmium in 100 mL water sample was chelated with 2.5 mL of 0.001 M 8-hydroxyquinoline at pH 8.0. After 0.07 g benzophenone was added, the solution was heated to about 70 ℃ and stirred vigorously for 1 minute to dissolve the complex quantitatively in a molten benzophenone, and stood for 30 minutes to reproduce the microcrystalline benzophenone. The benzophenone containing Cd-8-hydroxyquinoline complex was filtered and dissolved in acetone. Cadmium was determined by a flame atomic absorption spectrophotometry. The interfering effects of diverse concomitant ions were investigated and eliminated. This method could be applied to natural water samples and the recovery of more than 90% was obtained in the real samples.

• 자원리싸이클링
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• 제3권2호
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• pp.17-23
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• 1994

국내의 금정광으로부터 산성치오요소법에 의해 금, 은을 회수하기 위한 침출실험을 행하였다. 실험결과에 따르면 금, 은의 침출은 치오요소 및 산화제의 농도, 광액농도 등에 의해 크게 영향을 받고 있으며, 특히 3가철과 같은 산화제는 금, 은의 침출속도를 상당히 증가시킨다. 그러나 3가철의 농도가 너무 높으면 황화팡을 용해시켜 광석입자표면에 부동태층을 형성하기 때문에 금, 은의 침출을 저해하기도 한다. 한편 침출반응시 $SO_2$를 첨가하면 치오요소의 소모량은 어느정도 절감시킬 수 있으나, 금은의 침출율이 저하하여 귀금속의 회수에는 그리 효과적이지 못하다. 금정광으로부터 금과 은은 적정조건하에서 각각 90% 및 80%의 침출율을 보이며 이때 치오요소 소모량은 초기 농도의 약 10% 정도이다.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2539-2545
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• 2012

In the present study, we suggest a new way to reactivate performance of direct formic acid fuel cell (DFAFC) and explain its mechanism by employing electrochemical analyses like chronoamperometry (CA) and cyclic voltammogram (CV). For the evaluation of DFAFC performance, palladium (Pd) and platinum (Pt) are used as anode and cathode catalysts, respectively, and are applied to a Nafion membrane by catalyst-coated membrane spraying. After long DFAFC operation performed at 0.2 and 0.4 V and then CV test, DFAFC performance is better than its initial performance. It is attributed to dissolution of anode Pd into $Pd^{2+}$. By characterizations like TEM, Z-potential, CV and electrochemical impedance spectroscopy, it is evaluated that such dissolved $Pd^{2+}$ ions lead to (1) increase in the electrochemically active surface by reduction in Pd particle size and its improved redistribution and (2) increment in the total oxidation charge by fast reaction rate of the Pd dissolution reaction.

• Bulletin of the Korean Chemical Society
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• 제27권5호
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• pp.694-698
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• 2006

A method has been described for the chemical speciation, preconcentration and determination of Cr(III) and Cr(VI) species in filtered tannery waste waters by flame atomic absorption spectrometry using ion-exchange resins. Amberlite IR-120($H^+$) strongly acidic cation exchanger and Amberlite IRA-410($CI ^-$) strongly basic anion exchanger resins were used for the separation and preconcentration of Cr(III) and Cr(VI) species, respectively. Optimum condition for preconcentration and speciation was obtained by testing pH of sample and eluent, flow rates of sample and eluent, amount of resins, volume of sample and eluents, and effect of foreign ions. The recommended method has been successfully applied for the preconcentration and determination of chromium species in the dissolved phase of waste water samples collected from a tannery waste water treatment plant in Kayseri, Turkey. The detection limits achieved were 0.73 $\mu$g/L for Cr(III) and 0.81 $\mu$g/L for Cr(VI). Recovery studies showed 99% for Cr(III) and 98% for Cr(VI), for samples spiked with single species.

• 한국환경과학회지
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• 제14권7호
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• pp.691-697
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• 2005

Waste sludge may be used to recovery wastewater contaminated with heavy metals. The waste sludge is an inexpensive readily available source of biomass for biosorption with metal-bearing wastewater. The biosorption of heavy metals such as Pb(II), Cu(II), Cr(II), and Cd(II) onto waste sludge was investigated in batch ex­periments and waste sludge loaded heavy metals was separated by dissolved air flotation. The biosorption equi­bria of heavy metals could be described by Langmuir and Freundich isotherms. The adsorption capacity for waste sludge was in the sequence of Pb(II)>Cr(II)>Cu(II)>Cd(II). The system attained equilibrium about 20 min. The Langmuir and Freundlich adsorption model effectively described the biosorption equilibrium of Cu(II) and Cr(II) ions on waste sludge. Maximum adsorption capacity of Cu(II) and Cr(II) were 196.08 and 158.73 mg/g, respectively. Solid-liquid separation efficiencies were kept above $95\%$ on waste sludge loaded heavy metals, and were decreased with pH increasing.

• 한국환경과학회지
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• 제6권1호
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• pp.61-67
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• 1997

미생물에 의한 흡착법으로 중금속을 효과적으로 제거, 회수할 수 있다. 알콜 발효 후 부산물로 생성되는 폐 Saccharomyces cerevisiae는 비교적 가격이 저렴하고, 중금속 생체흡착에 유용한 자원으로 이용될 수 있다. 생체흡착 실험에 사용된 미생물은 부유 및 alginate에 고정화된 S. cerevisiae로 수행하였다. 회분식 실험에서 생체흡착량은 Pb > Cu > Cd의 순으로 이루어졌다. Pb 이온의 흡착 평형은 Freundlich와 Langinuir 모델로 설명하였고, Freundlich 모델이 실험자 료와 잘 부합되었다 고정화된 S. cerevisiae를 이용한 혼합용액( Pb, Cu, Cr 및 Cd )흡착 실험에서 각 중금속들은 선택적 흡착 특성을 나타내었다. 고정화 미생물을 고정층 반응기에 충진하여 혼합 중금속 용액의 생체흡착 실험을 수행한 결과 Pb 이온이 가장 많이 흡착을 하였다. 고정화된 미생물에 흡착된 Pb의 탈착실험에서 0.1M의 HCI 및 $H_2SO_4$가 효과적이었다.

• 분석과학
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• 제12권4호
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• pp.284-289
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• 1999

지하수 중에 용존된 무기탄소 화합물을 기체 방출 법을 이용하여 정량적으로 추출하였다. 기체 방출법은 직접 침전법에 비하여 소요시간이 적으며, 대기중의 이산화탄소 및 수중에 존재하는 황산이온의 영향도 무시할 수 있어 보다 효과적임을 알 수 있었다. 기체 방출법에 의한회수율 측정 결과 분당 4리터의 유량 율로 2시간 방출시켰을 때 99% 정도의 회수율을 나타내었다. 포집 시간에 따른 동위원소 분별효과를 측정하기 위하여 방출 초기 1시간과 이후 30분 간격으로 2회 포집 분석한 결과, 각각의 ${\delta}^{13}C$는 각각 -7.9‰, -3.0‰, +0.4‰로 측정되어 기체 방출법을 이용한 수중의 무기탄소 회수시 방출 초기에는 보다 가벼운 탄소의 방출이 우세하며, 보다 무거운 탄소의 방출은 후기에 이루어지는 것을 나타내었다. 그러나 이러한 동위원소 분별효과는 탄소화합물의 거의 완전한 회수에 의해 무시될 수 있었다.