• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.676-680
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• 2003

Dissolution of magnetite powders by 0.05 M citric acid was investigated at $50^{\circ}C$. All the tests were performed in the pH range between 2.0 to 5.0, which was adjusted using nitric acid or sodium hydroxide. Concentration of each of the dissociated chemical species of citric acid under various solution pHs was calculated using the ionization constants. Variation of zeta potential of magnetite with pH changes was also investigated. The dissolution reaction was explained by comparing the concentration of the dissociated chemical species of citric acid with the zeta potential. Longer than 3 h of induction time was required to dissolve the magnetite. The dissolution behaviour of magnetite was well described by the equation. The physical meaning of each parameter was explained successfully from the model equation.

• Journal of Korean Society of Forest Science
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• v.61 no.1
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• pp.27-36
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• 1983

This study was performed to get the basic information on nitric acid pulping of beech wood. In order to reduce the consumption of nitric acid, alkali pretreated woods were applied to a nitric acid pulping process. It consisted of nitric acid treatment to a high residual lignin content and the subsequent delignification with alkali, required far less chemical than the single stage method. At the first stage of nitric pulping, pulp yield descreased with increasing cooking time and 3 percent of nitric acid was more effective on the delignification of wood than 1 or 2 percent. Alkali pretreatment of wood improved significantly the rate of delignification, and 79 percent of the pretreated yield was good enough for excellent delignification. The dissolution of carbohydrate (mainly xylose) was increased with increasing cooking time, especially at the second stage. It would be considered that carbonyl groups introduced to polysaccharides in wood by nitric acid oxidation caused the degradation of carbohydrates.

• Resources Recycling
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• v.18 no.5
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• pp.26-36
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• 2009

A recovery process of Ruthenium from waste electronic scrap has been investigated by means of nitric acid leaching as a part of development for scrap pretreatment process to obtaining an optimum conditions for removal of removing various impurities such as Pb, Bi, Zn, Al, Bi, Ag Fe, Co, Zr, Si. From the experiments, 90% of Pb leached with 250 g/l pulp density in 10-15% nitric acid. Leaching behavior of Ba was also similar to that of the Pb, but those of other metal impurities, such as Zn, Al, Bi, Ag, Fe, Co, Zr, showed different behavior, in which the dissolution rate increased as the concentration of nitric acid in solution is increased up to the 10% $HNO_3$ in solution and then it was constant above 10% $HNO_3$ concentrations. Meanwhile, the dissolution of Ru in $HNO_3$ solution was less then 100ppm, and that the total content of Ru in undissolved residue scrap was resulted in an increment of 50%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.65-66
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• 2006

Solubility of single wall carbon nanotubes (SWNTs) has been determined in various dispersing media by using the solvent parameters such as Kamlet-Taft parameter and 3-dimensional parameters. Nitric acid-treated SWNTs exhibit significantly improved solubility in hydrogen bondable solvents as well as in solvent mixtures. The forming bucky gel with ionic liquid allows for the new group of dissolving solvent. The dissolution behavior of SWNTs provides a route for SWNT dispersion/exfoliation in preparing electrically conductive films such as transparent electrode.

• Journal of the Mineralogical Society of Korea
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• v.32 no.3
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• pp.185-200
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• 2019

This study aimed to liberate gold from invisible gold concentrate (Au = 1,840.00 g/t) through microwave nitric acid leaching experiments. For the purpose, this study conducted microwave-nitric acid leaching experiments and examined nitric acid concentration effect, microwave leaching time effect and sample addition effect. The results of the experiments were as follows: Au (gold) contents were not detected in all of the microwave leaching conditions. In the insoluble-residue, weight loss rate tended to decrease as the nitric acid concentration, microwave leaching time and sample addition increased. In an XRD analysis with solid-residue, it was suggested that gypsum and anglesite were formed due to dissolution of calcite and galena by nitric acid solution. When a fire assay was carried out with insoluble-residue, it was discovered that gold contents of the solid-residue were 1.3 (Au = 2,464.70 g/t) and 28.8 (52,952.80 g/t) times more than those of concentrate. But in the gold contents recovered, a severe gold nugget effect appeared. It is expected that the gold nugget effect will decrease if a sampling method of concentrate is improved in the microwave-nitric acid leaching experiments and filtering paper with smaller pore size is used for leaching solution and burned filter paper is used for sampling in lead-fire assay.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1085-1089
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• 2000

The effect of 2-hydroxyacetophenone-aroyl hydrazone derivatives on the inhibition of copper corrosion in 3N nitric acid solution at 303 K was investigated by galvanostatic polarization and thermometric techniques. A significant decrease in the cor rosion rate of copper was observed in the presence of the investigated compounds. The corrosion rate was found to depend on the nature and concentrations of the inhibitors. The degree of surface coverage of the adsorbed inhibitors is determined from polarization measurements, and it was found that the results obey the Frumkin adsorption isotherm. The inhibitors acted as mixed-type inhibitors, but the cathode is more polarized. The relative inhibitive efficiency of these compounds has been explained on the basis of structure dependent electron donor properties of the inhibitors and the nature of the metal-inhibitor interaction at the surface. Also, some thermodynamic data for the adsorption process ( ΔGa* and f ) are calculated and discussed.

• Journal of the Korean Society for Heat Treatment
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• v.26 no.4
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• pp.173-177
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• 2013

Separation and recovery of valuable metals such as zinc, nickel or tin from copper alloy dross has recently attracted from the viewpoints of environmental protection and resource recycling. In this report, preliminary study on concentration and separation of tin from copper alloy dross using selective dissolution method was performed. The tin in the copper alloy dross did not dissolve in the nitric acid solution which could allow the concentration and separation of the tin from the copper alloy dross. Precipitation of tin as $H_2SnO_3$ (metastannic acid) occurred in the solution and transformed to tin dioxide ($SnO_2$) after drying process. The dried sample was heat-treated at low temperature and its phase characteristics, surface morphology and chemical composition were investigated.

• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.99-107
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• 1997

This study Provides the treatment methods of liquid wastes from the dissolution/purification process of nuclear fuel raw material and the fabrication process of nuclear fuel powder. One of the treatment methods is to process liquid waste from uranium raw material dissolution/purification process. This waste, of the strong acid, can be reused to dissolve the fine ADU particles in filtrate which is ADU waste of pH 8.0 converted from AUC waste after recovery of uranium. To dissolve the fine ADU particles, ADU filtrate was pretreated to pH 4.0 with the dissolution/purification waste, and then mixed with the lime to pH 9.2 and aged for 30 minutes. From this processing, uranium content of the filtrate was decreased to below 3ppm. The waste from fuel powder fabrication is emulsified solution dispersed with fine oil droplets. This emulsion was destroyed effectively by adding and mixing the nitric acid with rapid heating at the same time. After this processing, $Na_2U_2O_7$ compound is produced by addition of NaOH. Optimum condition of this processing was shown at pH 11.5, and uranium content of the filtrate was analyzed to 5ppm. To remove the trace of uranium in the filtrate, lime should be added. Otherwise, 4N nitric acid was used to destroy the emulsion directly, and then lime was added to this waste. Uranium content of the treated filtrate was below 1 ppm. In addition to these wastes, the trace of uranium in filtrate after recovery of uranium from the AUC waste which is produced during PWR power preparation, is treated with NaOH to takeup fluorine(F) in the waste because fluorine is valuable and toxic material. In the finally treated waste, uranium was not detected.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1252-1254
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• 2005

Recently, PDP barrier ribs require the formation of complex structure so that they are usually formed by etching method. For producing the fine ribs structure, during the etching process the metal ions of matrix (glass) of barrier materials should be understood on the etching mechanism with etching condition. We analyzed the quantity of Pb, Si, and B ions from the etch solution as a function of etching time.

• Bulletin of the Korean Chemical Society
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• v.19 no.7
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• pp.766-770
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• 1998

On-line preconcentration by direct precipitation with hydroxide has been developed and applied for the analysis of Cd in Inductively Coupled Plasma Atomic Emission Spectrometry. Cadmium is continuously precipitated with hydroxide and dissolved by nitric acid in on-line mode. Currently, the enrichment factor is more than 90 times for 20.0 mL of sample and could be further increased very easily. For a large sample throughput, 1.0 mL of sample loop is used and the enrichment factor is 4.5 with the sampling speed of 15/hr. The method has been applied to the analysis of NIST reference sample and has yielded good results with the certified value.