• Bulletin of the Korean Chemical Society
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• 제17권10호
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• pp.925-929
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• 1996

Uranyl hydrolysis precipitates were obtained by increasing pH value of aqueous uranyl solution in the range of neutral to alkaline pH value and their phase transformation during the solubility experiment under various conditions has been examined. The precipitates formed in the hydrolysis reaction of uranyl ion had a layered structure such as a meta-schoepite phase, a schoepite structure, or a mixed phase of meta-schoepite and schoepite. Phase transformation between them was strongly dependent on the pH value at which the precipitate was formed. The distance between the layers in meta-schoepite or schoepite phase was ∼7.35 Å, and it was increased with the pH value at which the precipitate was synthesized as well as the pH values of the aqueous solution. The phase transformation from a meta-schoepite to schoepite was fast for the precipitates formed at low pH values, however, it was not the case for the precipitates formed at high pH values. A small difference of pH value in aqueous solution gave a great change on its solubilities near pH 9.7, because a layered structure of the precipitates became amorphous above that pH value. Greater solubility for the precipitate formed at higher pH value can be explained from the fact that the precipitates formed at low pH value had a better crystallinity and also that the precipitates formed at higher pH value has a slower rate of crystallization.

• Bulletin of the Korean Chemical Society
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• 제32권8호
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• pp.2643-2647
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• 2011

Efficient ditopic receptor, uranyl(II) N,N'-(ethylenedioxy)benzenebis(salicylideneimine) (3) for beryllium ion has been obtained upon functionalization of 1,2-ethylenedioxybenzene (1) with a uranyl-salphen (salphen = N,N'-phenylenebis(salicylideneimine)) unit. Binding affinities of the receptor, 3 in AN-DMSO (v/v 95:5) solution have been measured for alkali and alkaline earth metal ions by conductometry comparing 1. The results showed that both monotopic 1 and ditopic receptor 3 were selective for $Be^{2+}$ ions over other cations, while especially 3 that can complex both with cations (coordinated to basic oxygen of ethylenedioxybenzene) and anions (coordinated to the Lewis acidic uranyl center) results in an increase of the stability constants by a factor of $10^{2.42}$ with respect to 1. Furthermore, the $Be^{2+}$-3 interactions are demonstrated by $^1H$ NMR experiments in highly polar solvent medium, DMSO-$d_6$. Higher selectivities were also observed for $Be^{2+}$ when the ditopic receptor, 3 was incorporated into PVC membranes and tested as ion selective electrodes at neutral pH.

• 전기화학회지
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• 제3권3호
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• pp.141-145
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• 2000

전도성이 뛰어난 피롤고분자 피막을 전기화학적으로 중합하고 이를 Gr/ppy(Polypyrrole),X.O.(xylenol orange)형의 수식된 전극을 제작하여 U(VI)의 포집에 이용하였다. 사전피막제인 NBR(nitrile butadiene rubber)을 사용하였을 때 중합속도는 $3.22\times10^{-3}s^{-1}$로 이를 사용하지 않았을 때 보다 1.6배 느린 반응이었다. 포집된 U(VI)의 양은 ppy $1.70Ccm^{-2}$ 당에 $1.55\times10^{-4}g$ 이었으며, 인공해수 중에서 matrix효과는 $6.8\%$로 나타났다. ppy전극이 Gr/ppy, $X.O^{4-}UO^+$형으로 수식됨에 따라서 피막자체의 임피던스가 증가하여 ppy만일 때의 확산에 지배적인 전도과정에서 피막자체의 전자전도와 이온도핑과정이 함께 영향을 받는 결과를 보였다. ppy전극을 X.O.로 수식하여 U(VI)를 포집함에 따라 전기이중층의 용량은 각각 56과 130여 배로 증가하였다.

• 전기화학회지
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• 제1권1호
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• pp.40-44
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• 1998

pH변화를 정밀하게 측정하기 위하여 빠른 응답특성과 높은 감도를 갖는 전기화학적 전위차를 이용한 LAPS(Light-Addressable Potentiometric Sensor) 소자 및 시스템을 제작하여 그 기초 특성을 조사하였다. 먼저 pH 변화에 따른 LAPS의 정전기적 인 변화특성 및 소자의 변수를 LAPS 등가회로 모델을 이용한 모의실험을 통해 검증하고 이러한 모의 실험을 바탕으로 하여 LAPS 소자 및 시스템을 제작하였다. 제작된 LAPS 시스템은 pH 2-11 사이에서 56 mV/pH의 선형적인 감도를 보였다. 구성된 LAPS 시스템의 다양한 응용성을 도모하기 위한 시도로서 먼저, 일반적인 urea 센서가 가지는 긴 응답시간의 단점을 극복하기 위해 nitrocellulose membrane 에 urease가 고정화된 막을 LAPS에 부착하여 측정한 결과 urease 농도 $50{\mu}g/ml,500{\mu}g/ml$에 대하여 각각 0.29mV/sec, 0.816 mV/sec의 매우빠른 응답특성을 얻을 수 있었다. 또한 환경적 측면에서 중요한 우라닐 이온의 감지를 위하여 우라늄 인식 매체를 LAPS의 감지부에 부착하고 수용액 속에 녹아 있는 우라늄 이온을 측정한 결과 $10^{-11}\~10^{-4}M$의 넓은 농도 범위에서 25mV/decade 감도를 보였다

• 대한화학회지
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• 제40권9호
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• pp.599-606
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• 1996

서로 다른 pH 조건에서 생성한 우라닐 가수분해물의 용해도에 미치는 지하수 성분의 영향을 측정하였다. 우라닐 가수분해 침전물 pH 6.4 및 9.7에서 제조하였다. 편마암 층에서 채취한 지하수로부터 무기 및 유기콜로이드를 제거한 분리지하수, 채취지하수의 분석성분과 동일한 조성을 가지는 합성지하수, 그리고 0.1 M NaCl 수용액에서의 용해도에 미치는 pH의 영향을 측정하였다. 또한 채취지하수에서 상대적으로 다량 존재하는 음이온 및 양이온의 영향을 측정하였다. 지하수에서의 우라닐 가수분해 침전물의 용해도는 0.1 M NaCl 용액에서보다 약 100배 정도 큰 것으로 나타났다. X-선 회절분석 결과는 높은 pH에서 제조한 우라닐 가수분해 침전물이 낮은 pH에서 제조한 것보다 낮은 결정화도와 높은 용해도를 보였다.

• 전기화학회지
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• 제10권2호
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• pp.73-81
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• 2007

This review article considered the electrochemical reduction of uranyl ions on a Pt surface. Specifically, we focussed on the improvement in its reduction current efficiency. First, this article briefly explained the fundamentals of the reduction of uranyl ($UO_2^{2+}$) ions on a Pt surface. Namely, they involved the electrochemical behaviour of uranium species, and electrochemical cell configurations for the reduction of $UO_2^{2+}$ ions. In addition, the effects of adsorbed hydrogen atoms were investigated on the reduction of $UO_2^{2+}$ ions. Finally, this article presented the methods for improving current efficiency of the reduction of $UO_2^{2+}$ ions on a Pt surface. Three different kinds of methods are introduced, which include electrochemical surface treatments of Pt electrode involving hydrogenation and anodisation, the use of catalyst poisons, and formation of thin mercury film on a Pt electrode. Moreover, this article provided some clues about how hydrogenation and catalyst poisons work on the reduction of $UO_2^{2+}$ ions.

• 분석과학
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• 제17권1호
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• pp.23-28
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• 2004

Trace amount of uranyl (II) has been determined spectrophotometrically by measuring the optical density of the light blue yellowish coloured solutions formed by reaction between the metal ion and nicotinohydroxamic acid (NHx) in presence of different secondary ligands in strong isoamyl alcohol alkaline medium. The absorption maxima for both aqueous and extracted systems measured at their respective optimum pH were found to be 360 and 559 nm (DETA), 375 and 358 nm (EDA), 369 and 362 nm (piperidine), 354 and 341 nm (pyridine) and 363 and 336 nm (3 piperidine), 354 and 341 nm (pyridine) and 363 and 336 nm (3 - picoline), respectively at which Beer's law was obeyed. Effect of pH, reagent concentration, order of addition of reagent, time, temperature and solvent media on the absorption spectra have also been studied. Among the different systems studied, the shortest concentration range of uranyl(II) adhering to Beer's Law was 2.4 - 10.5 ppm observed for $UO_2(II)$ - NHx - DETA system in aqueous medium and also for iso amyl alcohol(IAA) extracted $UO_2$ - NHx - pyridine system was 2.4 - 7.8.

• 대한화학회지
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• 제32권4호
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• pp.351-357
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• 1988

Propanediol-1,2-carbonate (PDC) 용매중에서 우라닐 화합물의 전기화학적 환원반응 메카니즘을 전압전류법으로 조사하여 봉우리 전위의 위치, 한계전류의 성질, 한계전류와 온도 및 농도의 관계, 전극반응의 가역성, 양성자 공여체인 페놀의 첨가에 대한 영향등을 기술하였다. 또 우라닐 화합물의 수용액에 PDC의 양을 점차 증가시킨 혼합용매에서의 전극반응도 조사하였다. 우라닐 화합물의 비가역적 전극반응에 관여하는 전이계수 및 속도상수등의 반응 속도론적 파라미터를 Koutecky의 이론에 따라 결정하였으며, ${\Delta}H,\;{\Delta}G\;및\;{\Delta}S$등에 열역할적 파라미터도 계산하였다.

• 대한화학회지
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• 제5권1호
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• pp.84-87
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• 1961

A polarographic method for rapid determination of Uranium in the presence of foreign ions was proposed. The method is based on the measurement of polarogram in the sulfuric acid as supporting electrolyte. In this medium Uranyl ions give well defined reduction waves, and half-wave potentials are -0.19V vs. S.C.E. as first wave, and uncertain volt. vs. S.C.E. as second wave in $2.4 N-H_2SO_4.$ The first wave has a linear relationship between the concentration of Uranyl ion and wave height. The author also studied a method for rapid determination of Uranium in Korean monazite sand without eliminating the foreign ions. The Korean monazite sands were analyzed by this method and satisfactory result were obtained.

• Bulletin of the Korean Chemical Society
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• 제25권5호
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• pp.629-633
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• 2004

A new PVC membrane electrode for $UO_2^{2+}$ ion based on 2,2'-[1,2-ethanediyl bis (nitriloethylidene)]bis(1-naphthalene) as a suitable ionophore was prepared. The electrode exhibites a Nernstian response for $UO_2^{2+}$ ion over a wide concentration range ($1.0{\times}10^{-1}-1.0{\times}10^{-7}$M) with a slope of 28.5 ${\pm}$ 0.8 mV/decade. The limit of detection is $7.0{\times}10^{-8}$M. The electrode has a response time of < 20 s and a useful working pH range of 3-4. The proposed membrane sensor shows good discriminating abilities towards $UO_2^{2+}$ ion with regard to several alkali, alkaline earth transition and heavy metal ions. It was successfully used to the recovery of uranyl ion from, tap water and, as an indicator electrode, in potentiometric titration of $UO_2^{2+}$ ion with Piroxycam.