• Journal of Korean Society for Atmospheric Environment
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• v.5 no.2
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• pp.1-11
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• 1989

Sandy dust phenomena was observed from April 19 to 23, 1988 in Seoul. During this period it rained and the precipitation was collected to investigate the rain chemistry. This study was carried out to analyzed the chemical composition of precipitation by the measurements of conditivity, cations $(H^+, NH_4^+, K^+, Na^+, Ca^{2+}, MG^{2+})$, and anions $(SO_4^{2-}, NO_3^-, Cl^-, F^-, Br^-)$ which are believed to be the major ions playing an important role in the acidity of rain water. During the period of sandy dust phenomena the range of pH value and conductivity concentration of rainwater were 6.0-6.7, 172-254 $\mu \mho/cm$. The anions and cations concentrations increased and the orders of these concentrations were $SO_4^{2-} > Cl^- > NO_3^- > Na^+ > Ca^{2+} > NH_4^+ > Mg^{2+}$. THe principal chemical compounds of rainwater were estimated at $(NH_4)_2 SO_4, CaSO_4, NaCl, and MgCl_2$.

• Microbiology and Biotechnology Letters
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• v.42 no.1
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• pp.25-31
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• 2014

Fractional precipitation is a simple method for purifying (+)-dihydromyricetin extracted from biomass. However, the fractional precipitation process has been inherently problematic due to the lengthy precipitation time that is required. The fractional precipitation time was shortened and (+)-dihydromyricetin yield was improved by increasing the surface area per working volume (S/V) of the reacting solution through the addition of a cation exchange resin (Amberlite 200, Amberlite IR 120Na, Amberlite IR 120H, or Amberlite IRC 50). Most of the (+)-dihydromyricetin (>90%) could be obtained after about 16 h of fractional precipitation using Amberlite 200. Since high-purity (+)-dihydromyricetin can be obtained at a high yield and the precipitation time can be reduced by increasing the surface area available for precipitation, this improved method is expected to minimize solvent usage and the size and complexity of the high performance liquid chromatography operation required for (+)-dihydromyricetin purification.

• Korean Journal of Food Science and Technology
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• v.26 no.6
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• pp.683-689
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• 1994

With a view to utilizing effectively fish skin wastes from marine manufactory, a gelatin solution extracted from yellowfin sole skin was fractionated by precipitation with ethanol, and then the functional and physico-chemical properties for the fractionated gelatin were determined. Ethanol was added up to 50% of ethanol content to a gelatin solution extracted from yellowfin sole skin, then the mixture was left to stand at $0^{\circ}C$ for 12 hours. Finally, the precipitates were dried by hot-air ($40^{\circ}C$). The gel strength and melting point of a 10% gel of gelatin prepared from yellowfin sole skin by precipitation with ethanol has 322.4g and $23.3^{\circ}C$, respectively. The physico-chemical properties of the ethanol treated fish skin gelatin were superior to those of fish skin gelatin prepared without ethanol treatment. Besides, the functional properties of the ethanol treated gelatin were lower in solubility and higher in water holding capacity, oil binding capacity, emulsifying activity, emulsifying stability, foam expansion and foam stability than those of pork skin gelatin sold on market as well as gelatin prepared without ethanol treatment. It may be concluded, from these results, that the fish skin gelatin prepared by precipitation with ethanol can be effectively utilized as a human food by improving the functional properties.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.698-704
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• 1999

Li rich Li1+xMn2-xO4(x=0.07) spinel powders were prepared by an oxalate precipitation of wet chemical methods at temperature lower than $600^{\circ}C$. The FTIR results showed that the powders prepared at $600^{\circ}C$ had high degree of crystal quality comparing with the spinel powders prepared by solid state reaction at 75$0^{\circ}C$ which was the lowest synthesis temperature of the solid state reaction method. The particle size of powders prepared by the oxalate precipitation at $600^{\circ}C$ was smaller than 0.2${\mu}{\textrm}{m}$ and the specific surface area was 11.01 m2/g A heat treatment over 90$0^{\circ}C$ formed second phase in the precipitates. It was shown that there were phase transitions at temperatures. T1,T2 and T2. The transitions involved weight loss and gain during heating and cooling. The low temperature synthesis below $600^{\circ}C$ avoided the second phase formation and the prepared powders showed improved compositional and physical properties for secondary lithium battery applications.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1144-1148
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• 2014

Here we report a facile synthesis of ruthenium (Ru) Nanoparticles (NPs) by chemical co-precipitation method. The calcination of ruthenium hydroxide samples at $500^{\circ}C$ under hydrogen atmosphere lead to the formation of $Ru^0$ NPs. The size and aggregation of Ru NPs depends on the pH of the medium, and type of surfactant and its concentration. The X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope image (TEM) analyses of particles indicated the formation of $Ru^0$ NPs, and have 10 to 20 nm sizes. As-synthesized $Ru^0$ NPs are characterized and investigated their catalytic ability in click chemistry (azidealkyne cycloaddition reactions), showing good results in terms of reactivity. Interestingly, small structural differences in triazines influence the catalytic activity of $Ru^0$ nanocatalysts. Click chemistry has recently emerged to become one of the most powerful tools in drug discovery, chemical biology, proteomics, medical sciences and nanotechnology/nanomedicine. In addition, preliminary tests of recycling showed good results with neither loss of activity or significant precipitation.

• Journal of Industrial Technology
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• v.43 no.1
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• pp.1-6
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• 2023

TiO₂ is a versatile metal oxide material that is frequently used as a photo-catalyst for organic pollutant oxidation and a functional material for ultraviolet-ray protection. To improve its chemical/physical properties and widen the range of industrial application, it is demanded to control the crystalline feature and morphology precisely by applying advanced nano-synthesis methods. In this study, we prepared TiO₂ nanoparticles using the water-in-oil (W/O) microemulsion method and compared them with the particles synthesized by the conventional precipitation method. Also, we tried to find the optimum conditions for obtaining nano-sized, anatase-rich TiO₂ particles by the W/O microemulsion method. We analyzed the crystalline feature and particle size of the prepared samples using X-ray diffraction (XRD) and Transmission electron microscopy (TEM). In summary, we found the W/O microemulsion is more effective than precipitation in obtaining nano-sized TiO₂. The best result was derived when the microemulsion was formed using AOT surfactant, hydrolysis was performed under basic condition and the sample was calcined at 200℃.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.846-851
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• 1998

An experimental research on the preparation of zinc oxide fine particles in w/o emulsions was conducted. Precipitation solutions were zinc nitrate aqueous solutions with hexamethylenetetramine(HMTA) as precipitant. The precipitation solutions formed stable w/o emulsions with kerosine in the presence of Span 80. Homogeneous precipitation reaction occurred in the w/o emulsion after the resultant w/o emulsion was heated above the decomposition temperature of HMTA and zinc oxide particles were precipitated. In some case, zinc oxide particles of bi-modal distribution were obtained. However, zinc oxide fine particles of narrow particle size distribution could be obtained, even when the initial zinc concentration of precipitation solution and the conversion to zinc oxide are both higher that those in bulk homogeneous precipitation.

• Journal of Environmental Science International
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• v.7 no.5
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• pp.707-716
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• 1998

The chemical characteristics of precipitation was investigated in Pusan area. Samples were collected from January to November in 1996 at 4 sites, and analyzed pH, major soluble ionic components(C $l^{[-10]}$ , N $O_3$$^{[-10]}$ , S $O_4$$^{2-}$, N $a^{+}$, $K^{+}$, N $H_4$$^{+}$, $Mg^{2+}$, $Ca^{2+}$). The order of anion and cation concentrations for the initial precipitation were C $l^{[-10]}$ ＞ S $O_4$$^{2-}$ ＞ N $O_3$$^{[-10]}$ , and $Ca^{2+}$ ＞ N $a^{+}$ ＞ N $H_4$$^{+}$ ＞ $Mg^{2+}$ ＞ $K^{+}$, respectively. At coastal sites(P1 and P2) C $l^{[-10]}$ and N $a^{+}$ of maritime sources (seasalt) were high, but at inland sites(P3 and P4) nss-C $a^{2+}$ and nss-S $O_4$$^{2-}$ were high. Calcium ion for the initial precipitation showed high value of enrichement factor(EF) relative to seawater composition. The contribution of seasalt to the composition of precipitation was higher at bite P1 (53.5%) than those of the other sites. Throughout the year the concentrations of major ions for the initial precipitation were low in the heavy rain season. The mean pH for the initial precipitation was 5.4 and showed the negative relationship with the precipitaion amount. The S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ do not play an important role in rain acidification due to the high(97%) neutralizing effect of amonia and calcium species.and calcium species.

• Journal of the Korean Chemical Society
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• v.14 no.1
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• pp.137-140
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• 1970

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.702-706
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• 1998