• Journal of the Mineralogical Society of Korea
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• v.31 no.3
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• pp.137-147
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• 2018

The aim of this study was to leach penalty elements, such as Bi and As, effectively through microwave leaching of a gold concentrate sample containing penalty elements with nitric acid solution. For this purpose, the time effect of microwave leaching, nitric acid concentration effect, and sample addition effect in a microwave were examined. The experiment, demonstrated that the leaching rate of penalty elements increased as microwave leaching time and nitric acid concentration increased and concentration addition decreased. When a microwave heating experiment was carried out on the concentrate and ore minerals, Bi was removed by as much as 90%, and the phase of arsenopyrite was transformed in the order of arsenopyrite (FeAsS), pyrrhotite (FeS), and hematite ($Fe_2O_3$). When the X-ray diffraction (XRD) analysis was carried out with solid residue, elemental sulfur and anglesite were identified. The intensity of the XRD peaks of elemental sulfur and anglesite increased, and the peaks were sharper when the microwave leaching time was 12 min instead of 1 min, the nitric acid concentration was 4 M in rather than 0.5 M, and the concentration addition was 30 g rather than 5 g. This was probably because more elemental sulfur and anglesite were generated in the leaching solution as the leaching efficiency increased. Bi can be leached as valuable elements in the leaching solution through microwave leaching processes while they are released to the environment through a microwave heating processes.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.59.1-59
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• 2002

• Resources Recycling
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• v.26 no.1
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• pp.51-58
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• 2017

The present study to develop a process for extracting nitric acid and gold from aqua regia leach solution using TBP(tributyl phosphate) was conducted. The pure aqua regia was used to investigate the extractive behavior of nitric acid depending on the concentration of extractant, concentration ratio of nitric and hydrochloric acid. The extraction rate of nitric acid and gold from the gold bearing aqua regia was also examined. The theoretical extraction number was verified by counter current using the number of operations and the phase ratio obtained from McCabe-Thiele diagram. Stripping experiments were carried out for continuous recovery of nitric acid and gold in loaded organic. Considering the effect of extraction acid and gold, the simulation showed that greater than 99.9% extraction of $103.0mg{\cdot}L^{-1}$ gold and 98.0% of $151.2g{\cdot}L^{-1}$ nitric acid could be attained in a two and three-stage counter-current extraction at an O/A phase ratio of 1:0.85. Distilled water and sodium thiosulfate were used as the nitric acid and gold stripping solution. The stripping rates were 99.5% and 92.0%, respectively. The study revealed that the recovery of nitric acid and gold from gold bearing aqua regia was a plausible approach through simultaneous extraction and continuous stripping of nitric acid and gold.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.996-1002
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• 1999

The oxalate precipitation of lanthanide and actinide by oxalic acid was investigated in the simulated radioactive liquid waste, which was composed of 17 elements of alkali, alkaline earth(Cs, Rb, Ba, Sr), transition metal(Zr, Fe, Mo, Ni, Pd, Rh), lanthanide(La, Y, Nd, Ce, Eu) and actinide(Np, Am) in nitric acid solution. The effect of concentrations of nitric acid and ascorbic acid on the precipitation yield of each element in the simulated solution was examined at 0.5 M oxalic acid concentration. The precipitation yields of the elements were usually decreased with nitric acid concentration, nevertheless, the precipitation yields of lanthanide and actinide were more than 99%. Palladium was precipitated due to the reduction of Pd(II) into Pd metal by the addition of ascorbic acid in the oxalate precipitation and then, the precipitation yields of Mo, Fe, Ni, Ba decreased by 10~20% with concentration of ascorbic acid. The reductive precipitation of Pd(II) into Pd metal by the addition of ascorbic acid into the simulated radwaste occurred at below 1 M nitric acid concentration and its yield showed maximum at the ascorbic acid concentration of 0.01~0.02 M. The hydrazine suppressed the reductive precipitation of Pd by the ascorbic acid.

• Analytical Science and Technology
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• v.12 no.3
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• pp.177-183
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• 1999

The determination method of free acid in spent U-Al nuclear fuel solutions by Gran plot titration was described. Effect of U(VI) and Al(III) on the alkalimetric titration of nitric acid was investigated in oxalate complexing media as well as in noncomplexing media. Positive biases were observed in both titration media when the end-point was estimated by the Gran plot method. It was found that the cause of the bias was U(VI) in the oxalate complexing media, but Al(III) in the noncomplexing media. The relative error was less than 1% in the titration of 0.1 M $HNO_3$ at a U(VI) : Al(III) : $H^+$ mole ratio of up to 2:12:1 as long as the pH of the oxalate titration media was sustained to be below 5.0 at the beginning of titration. The method was successfully applied to the determination of nitric acid in a solution of HANARO reactor fuel with U:Al mole ratio of 1:6.

• Resources Recycling
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• v.10 no.5
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• pp.22-28
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• 2001

Recovery of silver in the spent solution generated from MEO(Mediated Electrochemical Oxidation) process, which is a process to decompose radioactive organic mixed wastes at low temperature, was performed using chemical method. Silver nitrate in 5M nitric acid solution could be completely recovered as AgCl by using 1% excess of the stoichiometric HCl equivalents. Then, AgCl was transformed to Ag metal by reduction reaction with hydrogen peroxide under alkaline media. The optimum pH for the reduction to silver metal was found to be in the range of 12.8∼13.0.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.3 no.1
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• pp.99-99
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• 1993

혈액 및 생체시료 중 필수원소 혹은 독극성 원소의 극미량상분 정밀측정과 동위원소비율측정에 널리 사용되는 유도결합플라즈마 질량분석기(ICP-MS)의 기본원리를 소개하고 ICP-SM를 이용한 혈액중 낮은 ppb수준의 Cd, Hg 그리고 Pb의 정밀분석법을 소개한다. 혈액은 많은 양의 유기물을 포함하고 있으므로 digestion bomb에 질산과 과산화수소를 넣어 microwave oven에서 고온고압 상태로 분해시켜 많은 용액을 얻어 이 용액을 플라즈마에 주입시켜 분석한다. 그리고 수온은 tin(II) chloride 용액을 환원제로하여 생성시킨 수은원소증기를 membrane liquid-gas separator를 이용하여 뽑아내어 플라즈마에 주입시켜 낮은 ppt 수준의 검출한계를 얻는다. 또한 높은 정밀도와 정확도와 극미량 원소 측정에 사용되는 동위원소 회석법율 소개하고 실제 혈액분석에의 응용방법을 제시한다.

• Analytical Science and Technology
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• v.17 no.5
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• pp.393-400
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• 2004

Nitrosation of phenol (POH) was studied by adding hydrochloric acid and sodium nitrite to phenol solution with reaction temperature and time change. The optimum condition of nitrosation was found from the effects of hydrochloric acid and sodium nitrite concentration, reaction temperature, and reaction time changes on the production of nitrosophenol (POHNO). As a result, it was found that the optimum conditions were $5.0{\times}10^{-4}{\sim}2.0{\times}10^{-3}M$ range of $NO{_2}^-$ concentration, more than 0.10 M of HCl concentration, temperature of $80^{\circ}C$, and 3 hrs. of reaction time. In this condition, 10 U.S. E.P.A. classified priority environmental pollutant, phenols, were nitrosated. Nitrosated phenols were: POH, 2-Chlorophenol (2ClPOH), 2,4-diChlorophenol (2ClPOH), 2,4-dimethylphenol (24diMPOH), and 4-Chloro -3-methylphenol (4Cl3MPOH), and a small part of 2-nitrophenol (2NPOH). The ${\lambda}_{max}$ values of nitrosated phenols in acidic solution were around 300 nm, and those in basic solution were around 400 nm. Molar absorptivities (${\varepsilon}$) at the 400 nm of the nitrosated phenols in the basic solution were 1.5~2.0 times larger than those at 300 nm in acidic solution. It was also found by Capillary-HPLC chromatograms of the nitrosated phenol solutions that the production of the nitrosophenols were interfered by the excess concentration of nitrite (more than $3.0{\times}10^{-3}M$).

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.2
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• pp.85-93
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• 2013

This study has been carried out to elucidate the characteristics of the dissolution for Thermal Decomposed Solid Waste of uranium-bearing sludge (TDSW), the removal of impurities by an alkalization in a nitric acid dissolving solution of TDSW, and the selective removal (/recovery) of uranium by an acidification in an carbonate alkali solution, respectively. TDSW generated by thermal decomposition of U-bearing sludge which was produced in the uranium conversion plant operation, was stored in KAERI as a solid-powder type. It is found that the dissolution of TDSW is more effective in nitric acid dissolution than oxidative-dissolution with carbonate. At 1 M nitric acid solution, TDSW was undissolved about 30wt% as a solid residue, and uranium contained in TDSW was dissolved more than 99%. In order to the alkalization for the nitric acid dissolving solution of TDSW, carbonate alkalization is more effective with respect to remove the impurities. At the carbonate alkali solution controlled to about 9 of pH, Al, Ca, Fe and Zn co-dissolved with U in dissolution step was removed about $98{\pm}1%$. On the other hand, U could be recovered more than 99% by an acidification at pH about 3 in a carbonate alkali solution, which was nearly removed the impurities, adding 0.5M $H_2O_2$. It was found that uranium could be selectively recovered (/removed) from TDSW.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.319-324
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• 2016

In this study, pitch-based carbon fibers in the acid were radiated with an electron beam to modify their surface, and surface changes were investigated according to each treatment conditions. Nitric acid and hydrogen peroxide were used as a drenched acidic solution and an electron beam dose was set to 200 and 400 kGy. The use of nitric acid introduced more oxygen functional groups on carbon fiber surfaces than that of using hydrogen peroxide, and also introduced nitrogen functional groups into the carbon fiber surface. In addition, oxygen functional groups introduced on carbon fiber surface increased as the electron beam dose increased due to the fact that the oxidizing material can be easily formed by e-beam radiation in nitric acid than the hydrogen peroxide, and also the higher energy electron beam dose can help forming more oxidizing materials. Moreover, the generation of C=O functional groups was favorable when using nitric acid because oxidizing C-OH functional groups to the C=O functional groups mainly occurred by $NO_2$ radicals generated by the electron beam radiation in a nitric acid solution.