• Resources Recycling
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• v.2 no.4
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• pp.27-32
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• 1993

A process has been studied to recover gallium from steelmaking dust which had several hundreds ppm of gallium. Aqueous solution containing 38 mg/l gallium was obtained by leaching of dust with 2.25 mol/l sulfuric acid. The leach liquor contained iron and zinc about 1,000 times greater than gallium. Gallium was then concentrated by ion exchanger of chelating resin with functional group of amino carboxylic acid after reduction of ferric ion to ferrous ion and pH adjustment. Gallium was concentrated to be 13 g/l in the resulting eluate by double ion exchanges. The liquor was further treated to remove impurities by solvent extraction technique empolying TOMAC as extractant. The galluim with 99% purity was finally obtainable.

• Resources Recycling
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• v.22 no.2
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• pp.3-10
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• 2013

Indium is one of the rare metals, and it has been used mainly for preparation of indium tin oxide (ITO). This review investigated the process parameters and the merits and demerits of several methods to recover indium from the leaching solution of secondary resources, such as solvent extraction, ion exchange, and precipitation. D2EHPA has been used mostly as a cationic extractant for indium extraction in moderate acid solutions, while amine extractants are used in strong hydrochloric acid solution. Since the loading capacity of resins for indium is generally small, ion exchange has some advantage over solvent extraction only when the concentration of indium is low.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2607-2610
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• 2011

Monodispersed Ag/$TiO_2$ core/shell nanoparticles were synthesized in solution via colloid-seeded deposition process using Ag nanoparticles as colloid seeds and $Ti(SO_4)_2$ as Ti-source respectively. Silver nitrate was reduced to Ag nanoparticles with $N_2H_4{\cdot}H_2O$ in the presence of CTAB as stabilizing agent. The titania sols hydrolyzed by the $Ti(SO_4)_2$ solution deposited on the surface of Ag nanoparticles to form the Ag/$TiO_2$ core/shell nanoparticles. Inductively coupled plasma atomic emission spectrometry (ICP-AES) showed low amount of Ag ion leaching from the Ag/$TiO_2$ core/shell nanoparticles. The Ag/$TiO_2$ core/shell nanoparticles indicated excellent antibacterial effects against Escherichia coli and maintained long-term antibacterial property.

• Journal of the Korean Ceramic Society
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• v.43 no.1 s.284
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• pp.33-37
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• 2006

For producing the fine ribs structure of plasma display panel, the metal ions of barrier materials during the etching process should be understood on the etching mechanism with etching conditions. Etching was done on bulk glasses of the $BaO_B_2O_3-ZnO$ system with $HNO_3$ solution at $40^{\circ}C$. The surface structure of glasses and ion dissolution were analyzed by ICP (Inductive Coupled Plasma measurement). The structure and surface of the etched bulk glass were investigated by using scanning electron microscopy and nanoindenter. As a result, Ba (3-35 ppm/min) and Zn (2-27 ppm/min) ions as major components were leached in the solution and the leached layers were found to be phosphor-rich surface layers. A decrease of the bridge oxygen and relative increase of non bridge oxygen in the etched glass were found by X-ray photoelectron spectroscopy.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.618-622
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• 2010

Cost-effective purification methods of silicon were carried out in order to replace the conventional Siemens method for solar grade silicon. Firstly, acid leaching which is a hydrometallurgical process was preceded with grinded silicon powders of metallurgical grade (~99% purity) to remove metallic impurities. Then, plasma treatments were performed with the leached silicon powders of 99.94% purity by argon plasma at 30 kW power under atmospheric pressure. Plasma treatment was specifically efficient for removing Zr, Y, and P but not for Al and B. Another purification step by EB treatment was also studied for the 99.92% silicon lump which resulted in the fast removal of boron and aluminum. That means the two methods are effective alternative tools for removing the doping elements like boron and phosphor.

• Resources Recycling
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• v.21 no.3
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• pp.74-83
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• 2012

Rare earth metals have been made from rare earth compounds which were prepared from rare earth ore concentrates through successive processes such as leaching(i.e. extraction of rare earth elements to liquid media), separation, purification, precipitation. Here, process for treating monazite and bastnasite ore concentrates were briefly reviewed, and metallothermic reduction and fused salt electrolysis methods were introduced as the extraction technologies for rare earth metals.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.132-132
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• 2009

To achieve the commercialization of PEM fuel cell, the durability problem must be solved. Recently, many researchers have focused on this durability problem and degradation studies about membrane and electrode have been reported. But durability characteristics of gas diffusion layer is not much reported yet. Durability of GDL is very important to maintain the performance of PEM fuel cell because the main function of GDL is a path of fuel and water and the GDL degradation causes the loss of the GDL function. In this study, the degradation of GDL, especially, the mechanical degradation process was investigated with the leaching test. The effect of water dissolution was observed through the test and the amount of GDL degradation was measured with various measurement methods such as weight measurement, static contact angle measurement, scanning electron microscope. After 2,000 hours test, the GDL showed structural damage and loss of hydrophobicity.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.345-349
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• 2003

The quantity, process and kinetics of di-(2-ethylhexyl)phthalate (DEHP) migration in the 30/70 and 40/60 poly(vinylchloride) (PVC)/DEHP blends were investigated using gas chromatograph. A thin and flexible PVC sheet was soaked in surrounding medium (SM) of water/ethanol mixture and acetonitrile with constant stirring to release DEHP. By observed concentration of DEHP in the SM, it is found that acetonitrile is more intense in DEHP migration than water/ethanol mixture. In addition the amount of extracted DEHP is proportional to the leaching temperature and added ratio of DEHP. The behavior of DEHP migration from flexible PVC sheets was described by the Ficks's law with $2.72-10.1\;{times}\;10^{-10}$ cm²/s of the diffusion coefficients.

• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.685-693
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• 1988

From leaching of Korean native halloysite with hot sulfuric acid, active species of siliceous aluminosilicate are obtained as residue, which gives the mole ratio of SiO2/Al2O3 10 and substantially removes most acid-soluble impurities. By dissolving the residue in sodium hydroxide at an ambient temperature sodium silicate solution is prepared, this is used for zeolite synthesis as one of starting materials. In order to prepare zeolite Type 4A thereform, addition of a proper aluminum source is made so that the composition of the reactant materials may be of the following mole ratios : Na2O/SiO2=1.2-1.5, SiO2/Al2O3=1.8-2.0 and H2O/Na2O=34-45 By careful control of ageing time and temperature, subsequent crystal growth is induced into microfine zeolite 4A, which gives optimum particle size distributjion being suitable for detergent builder. The zeolite products thus obtained and highly competitive with those from the use of the refined clay in comparison of their calcium exchange capacity, whiteness and particle size distribution. The present method shows a marginal advantage over the existing procedures requiring neitherseparate purification nor calcinating otherwise necessary for the raw clay ores in use.

• Journal of the Korean Ceramic Society
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• v.55 no.1
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• pp.36-43
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• 2018

The physical and chemical analyses of mineral waste such as moisture content, water absorption, freezing-thawing resisting sexual, chemical composition and crystal structure were investigated. In the technological process of crushing, screening, molding, drying, preheating, sintering and cooling, many parameters were changed to eliminate the influence of freeze thaw stability and the ball billets were processed into slate ceramsites eventually. Adopting orthogonal experiment and range analysis, the optimal technology parameters were confirmed as preheating temperature of $300^{\circ}C$ for 25 minutes and sintering temperature of $1230^{\circ}C$ for 20 minutes. Slate wastes in Shangri-la could foam and expand without any additive. The ultra-light ceramsite could be directly used as building aggregate, since the analysis results of its leaching toxicity were eligible. Besides, effects of sintering temperature on physical property and crystal phase were also explored in this study.