• 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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• 제22권8호
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• pp.801-806
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• 2001

A study has been carried out on the separation of gold, iridium, palladium, rhodium, ruthenium and platinum in chromite samples and their quantitative determination using inductively coupled plasma atomic emission spectrometry (ICP-AES). The dissolution condition of the minerals by fusion with sodium peroxide was optimized and chromatographic elution behaviour of the rare metals was investigated by anion exchange chromatography. Spectral interference of chromium, a matrix of the minerals, was investigated on determination of gold. Chromium interfered on determination of gold at the concentration of 500 mg/L and higher. Gold plus trace amounts of iridium, palladium, rhodium and ruthenium, which must be preconcentrated before ICP-AES was separated by anion exchange chromatography after reducing Cr(Ⅵ) to Cr(III) by H2O2. AuCl4- retained on the resin column was selectively eluted with acetone- HNO3-H2O as an eluent. In addition, iridium, palladium, rhodium and ruthenium remaining on the resin column were eluted as a group with concentrated HCl. However, platinum was eluted with concentrated HNO3. The recovery yield of gold with acetone-HNO3-H2O was 100.7 ${\pm}2.0%$, and the yields of palladium and platinum with concentrated HCl and HNO3 were 96.1 ${\pm}1.8%$ and 96.6 ${\pm}1.3%$, respectively. The contents of gold and platinum in a Mongolian chromite sample were 32.6 ${\pm}$ 2.2 ${\mu}g$/g and 1.6 $\pm$ 0.14 ${\mu}g$/g, respectively. Palladium was not detected.

• Corrosion Science and Technology
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• 제4권1호
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• pp.19-22
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• 2005

Two Au-Ag-Cu-Pd dental casting alloys (Au:12% and 20%) used. The test solutions used 0.9 % NaCl solution (isotonic sodium chloride solution), 0.9 % NaCl solution containing 1 % lactic acid, and 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol $dm^{-3}$ $Na_2S$. The surface of two samples in three sample solutions was not natural discoloration during one year. The alloy containing 12 % gold was easily alloyed and the composition was uniform comparing with the alloy containing 20 % gold. The rest potentials have not a little effect after three months. The kinds of metals could not definitely from the oxidation and reduction waves of metal on the cyclic voltammograms. The dissolutions of gold and palladium were 12 % Au sample in the 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol $dm^{-3}$ $Na_{2}S$. The pH of solution had an affect on dissolution of copper, and sulfur ion had an affect on dissolution of silver. The copper dissolved amount from 20 % gold sample was about 26 times comparing with that of 12 % gold sample in the 0.9 % solution containing 1 % lactic acid. Corrosion products were silver chloride and copper chloride in NaCl solution, and silver sulfide and copper sulfide in NaCl solution containing $Na_{2}S$.

• 청정기술
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• 제26권4호
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• pp.270-278
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• 2020

팔라듐(Pd)은 희소금속임에도 불구하고 보석, 촉매 및 치과 소재와 같은 다양한 산업 응용 분야에 널리 사용되고 있다. 이러한 가운데 폐자원으로부터 고순도 Pd를 회수하는 기술들이 주목받고 있다. 본 연구에서는 염산 용액에서 팔라듐 침출 및 회수를 위한 최적 조건을 조사하였다. 염산 농도, 침출온도, 침출시간, 산화제 농도 및 광액 농도 등 다양한 실험조건에서 팔라듐 침출 실험을 수행하였다. 염산농도 3 M, 산화제 3 vol%, 침출온도 80 ℃, 침출시간 60분에서 약 97.2%의 침출율을 나타내었다. 과산화수소/차아염소산나트륨의 비율은 침출용액 내 염소 이온 농도를 증가시켜 팔라듐 침출을 용이하게 하는 역할을 하는 것으로 확인하였다. 또한 pH 7에서 포름산을 첨가하여 80 ℃에서 30분 간 교반할 시 99.6% 순도를 가지는 팔라듐 분말을 회수할 수 있었다. 이는 포름산이 80 ℃에서 수소 가스와 이산화탄소로 분해되어 환원제 역할을 하였기 때문이라고 사료된다. 따라서 회수 되어진 고순도 팔라듐 분말은 회로, 촉매 전구체 및 수술기구에 사용될 것으로 기대되어진다.