• Archives of Pharmacal Research
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• v.28 no.3
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• pp.370-375
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• 2005

The objective of this study was to develop a new reverse micelle-based microencapsulation technique to load tetracycline hydrochloride into PLGA microspheres. To do so, a reverse micellar system was formulated to dissolve tetracycline hydrochloride and water in ethyl formate with the aid of cetyltrimethylammonium bromide. The resultant micellar solution was used to dissolve 0.3 to 0.75 g of PLGA, and microspheres were prepared following a modified solvent quenching technique. As a control experiment, the drug was encapsulated into PLGA microspheres via a conventional methylene chloride-based emulsion procedure. The micro­spheres were then characterized with regard to drug loading efficiency, their size distribution and morphology. The reverse micellar procedure led to the formation of free-flowing, spherical microspheres with the size mode of 88 ~m. When PLGA microspheres were prepared follow­ing the conventional methylene chloride-based procedure, most of tetracycline hydrochloride leached to the aqueous external phase: A maximal loading efficiency observed our experimental conditions was below $5\%$. Their surfaces had numerous pores, while their internal architecture was honey-combed. In sharp contrast, the new reverse micellar encapsulation technique permitted the attainment of a maximal loading efficiency of 63.19 $\pm$$0.64\%$. Also, the microspheres had smooth and pore-free surfaces, and hollow cavities were absent from their internal matrices. The results of this study demonstrated that PLGA microspheres could be successfully prepared following the new reverse micellar encapsulation technique.

• Macromolecular Research
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• v.16 no.7
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• pp.626-630
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• 2008

Poly(vinyl pyrrolidone) was used successfully to control the size and distribution of silver nanoparticles generated on inorganic silica nanofibers. The inorganic nanofibers were electro spun using sol-gel chemistry of silicates, and the diameter of the prepared nanofibers was unaffected by adding up to 7% of poly(vinyl pyrrolidone). The silver ions, in the form of silver nitrate, were introduced into the silica nanofibers and reduced to metallic silver by ultraviolet irradiation with a subsequent thermal treatment. The size of the generated silver particles was decreased dramatically by adding poly(vinyl pyrrolidone). The size of the silver nanoparticles was 73 nm when no poly(vinyl pyrrolidone) was added but 23 nm with the addition of only 1% of poly(vinyl pyrrolidone). The extent of reduction could be checked by determining the concentration of silver ions leached into water from the silica nanofibers. After thermal treatment of the silica nanofibers, more than 99% of the silver remained in the nanofibers, indicating almost complete reduction of the silver ions to silver metal.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 1999.10a
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• pp.221-223
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• 1999

The adsorption and leaching of organophosphorus pesticide, EPN are investigated in Namwon soil(black volcanic soil), Aewol soil(very dark brown volcanic soil) and Mureung soil(dark brown nonvolcanic soil) sampled in Cheju Island. The organic matter of Namwon soil, Aewol soil and Mureung soil is 19.8%, 6.2%, 2.4%, respectively. The cation exchange capacity of Namwon soil, Aewol soil and Mureung soil is 24.8 meq/100g, 13.0 meq/100g, 9.5 meq/100g, respectively. The Freundlich constant, K value, is 89.4, 26.9 and 9.25 for Namwon soil, Aewol soil and Mureung soil, respectively. The K value of Namwon soil with very high organic matter content and cation exchange capacity was the highest for Aewol soil and Mureung soil. The Freundlich constant, 1/n, show a high correlation with organic matter content, i.e., it is less than unity for organic matter rich soil of Namwon soil and greater than unity for organic matter poor soil of Mureung soil. The leaching of EPN is slower for Namwon soil with high K values, and faster for Mureung soil with low K values. The results of the study is demonstrated the potential of pollution for EPN have little leached into soil environment.

• Journal of Ecology and Environment
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• v.37 no.1
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• pp.13-19
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• 2014

The effect of different turnover time of water on the decomposition of emergent macrophyte litter (Zizania latifolia Griseb.) was investigated using a microcosm experiment. Microcosm treatment represented different turnover time of water; 1, 2, 4 and 8 weeks. The litterbags from each treatment were retrieved every 2 weeks until the 8th week and the water simultaneously sampled with the litterbag. The dry weight and the content of major cations in the litter, and the content of available N, P, and major cations in the water were analyzed. Dry weight loss after 8 weeks indicated the lower decay rates under the condition of short turnover time of water. Major cations from the litter and the water showed that the leached amounts of K and Mg from the litter were highest in the 2nd week and dramatically decreased from the 4th week. The dynamics of available nitrogen and phosphorus in the water showed that as the water turnover time was getting longer, the amounts of available nitrogen and phosphorus remained higher. These results suggest that wetlands with longer turnover time of water could maintain the increased nitrogen and phosphorus and no outflow of the nutrients could cause eutrophication problem.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.2
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• pp.286-290
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• 1998

The effects of cooking methods and storage time on folate content in spinach were determined by boiling for 1, 2, 3, 4, 5, 10 and 20min in distilled water or by microwave blanching for 20, 40, 60, 80, 100 sec. The folate content of cooked spinach was decreased to 80.7% after 1min boiling, and to 5.5% after 20min boiling. The folate recovered from the cooked spinach and cooking water was 101.1% after 1min, 68.0% after 2min and 51.3% after 3min. The relative folate content leached out of the cooked spinach into the cooking water varied from 20.2% after 1min boiling to 88.8% after 20min boiling. Total folate content of spinach was decreased to 45% by microwave heating for 40sec. However, the spinach cooked by microwave heating retained more folate due to the minimal loss of folate into cooking water. More than 90% of folate content of spinach was retained during 1 to 2 weeks of storage at 4$^{\circ}C$.

• The Korean Journal of Ecology
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• v.20 no.2
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• pp.133-143
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• 1997

From 1984 to 1989 reclaimed coastal lands in Choongnam Province of the western coast of Korea were studied for soil texture at three sites(Daeho, Hyundai A and Hyundai B) and for desalination one site(Hyundai B). The soil textures of varied sites in Hyundai A were horizontally similar and composed of 39-40% clay, 40-49% silt and 8-14% sand. But those in Da돼 and Hyundai B differed horizontally in the same area and vertically at the same site. Soil texures of Da돼 were composed of 15-17% clay, 30-45% silt and 40-55% sand and those of Hyundai B were composed of 22-45% clay, 26-49% silt and 17-31% sand. The measured electrical conductivity(EC), which represents whole salt content of the reclaimed soil, decreased year by year. The vertical distribution of the EC changed temporally and spatially in the upper zone above a 50 cm depth but not in The lower zone below a 50 cm depth. The EC valus of the soil were inversely proportional to the magnitued of annual precipitation, evaporation and the numbers of rainy days with r equalling -0.97. But the annual decrease of the EC was directly proportional to climatic factors with r=0.7. Salt in the reclaimed land was leached out by the percolative action of surplus rain water, or moved up by evaporation and carried away by running rain water. The running out of the salt on the soil surface was most efficiently carried out over 10 mm precipitation per day.

• Environmental Engineering Research
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• v.10 no.6
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• pp.294-305
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• 2005

The effectiveness of fly ash-, quicklime-, and quicklime-fly ash-based stabilization/solidification(S/S) in chromium(Cr) contaminated soils was investigated using modified semi-dynamic leaching tests. Artificial soil samples composed of kaolinite or montmorillonite contaminated with chromium nitrate(4000 mg $Cr^{3+}\;kg^{-1}$ of solid) were prepared and then subjected to S/S treatment using quicklime, fly ash, or quick lime-fly ash. The effectiveness of the treatment was evaluated by assessing the cumulative fraction of leached $Cr^{3+}$ as well as, by computing the effective diffusivity ($D_e$) and the leachability index (LX) of the treated samples. The reduction in $Cr^{3+}$ release for the untreated samples was more pronounced in the presence of montmorillonite, which was attributed to sorption. Treatment with quicklime, fly ash, or quick lime-fly ash was significantly effective in reducing $Cr^{3+}$ release most probably due to the formation of pozzolanic reaction products and $Cr(OH)_3$ precipitation. The most effective treatment was observed in montmorillonite-sand soil samples treated with quicklime-fly ash (99.8% removal). The mean $D_e$ decreased significantly and the mean LX was greater than 9 for all treated samples, indicating that the treated soils were acceptable for "controlled utilization". The mechanism controlling $Cr^{3+}$ leaching from all treated samples during the first 5 days appeared to be diffusion.

• Economic and Environmental Geology
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• v.27 no.6
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• pp.507-521
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• 1994

Bentonite occurs in the Janggi Conglomerate of Tertiary age and consists mainly of montmorillonite with Mg as predominant interlayer cations. The bentonite was reacted with various concentrations of sulfuric acid (0.8~1.5M) for various reaction time (1-10h) at $103^{\circ}C$. Cation exchange capacity, exchangeable cations, surface area and solid acidity of the original bulk and acid activated bentonites were measured. Chemical analysis, X-ray diffraction, differential thermal analysis and infrared spectroscopy were used to characterize the changes in structure and properties of the acid activated bentonite. The dissolution of octahedral cations occurs not only from the edge of the clay platelets but also throughout the whole clay structure creating vacant octahedral sites. These lattice defects are created by $H^+$ diffused into the smectite layers. The cations leached possibly from the octahedral sheets are adsorbed on the interlayer exchange sites. They are exchanged with hydronium ions again by stronger acid attack. These reactions create wedge-shaped pores resulting in the increase of the surface area and the changes the morphology in the lattice structure.

• Resources Recycling
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• v.1 no.1
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• pp.51-57
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• 1992

The hydrochloric acid leaching has been studied as a fundamental experiment on the recovery of arsenic from arsenic-bearing copper slime in copper electrorefining. The slime is mainly composed of $\beta-Cu_3As$ Which is intermetallic compound of CU and As. And the minor components are $CU_2O$ and CusAs in the slime. The optimum conditions of leaching of the slime were found to be as follows : 6N hydrochloric acid, particle size passed through 140 mesh, leaching for 150 min at $60^{\circ}C$, ratio of HCI/slime of 3 to 1 ; where 98 percent of arsenic were leached out of the As-bearing slime.

• Journal of Wetlands Research
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• v.4 no.2
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• pp.23-41
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• 2002

In this paper, changes of the coliform bacteria were investigated when aquatic plant pond was used for separating algal particles from waste stabilization ponds(WSPs). Three different types of integrated natural systems were operated. It was found that there were no significant interferences for the disinfection efficiency of two integrated systems (WSPs coupled with water hyacinth ponds) used for treating domestic sewage and upgrading the secondary effluent as well. However, when constructed wetland (CW) was combined with the shallow algal ponds and used for the secondary effluent, it seriously interfered with the disinfection efficiency due to the regrowth and/or after-growth of the coliform bacteria, which can readily metabolize the amino acids and sugars leached from plants. In order to find out the primary disinfection parameters, several sets of the batch test were run. It was found that sunlight is the most predominant factor for the coliform decay. During the night, algal toxicity partly supports the decay but during the day, deteriorates it by attenuating the sunlight. The pH in the range of 4 to 10 did not affect the decay in the dark.