• Journal of environmental and Sanitary engineering
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• v.13 no.1
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• pp.16-25
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• 1998

Laboratory-scale experiment using anaerobic fluidized bed reactor was carried out to investigate the prehydrolysis step with caustic soda on the treatment efficiency of anaerobic sludge treatment, since the overall rate-limiting step for the complete anaerobic digestion of sludge was the hydrolysis step by extracellular bacterial enzymes of insoluble polymeric molecules. Reactors received a sludge which had not been pretreated, a 50-50 mixture of pretreated and untreated sludge, and the fully pretreated sludge. Hydraulic retention time of 10, 5, 2.5 days and 1 day were applied with an respective equivalent organic loading rate of 1.17, 2.23, 4.17, 11.24 gCOD/L/d. Reactor with the untreated sludge did not archieve adequate digestion even at the HRT of 5 days, and reactor, which received the 50-50 mixture, operated well at the HRT of 5 days, but began to show signs of unstable digestion at the HRT of 2.5 days. While, reactor, which was fed the hydrolyzed sludge, operated reasonably well at the 2.5 days, but was showing somewhat decrease in removal efficiencies. Results, therefore, have substantiated that the limiting reaction in the anaerobic treatment process is hydrolysis. The soluble COD did not significantly accumulate in the reactor as organic acid form, even when they were highly stressed. It was believed that this resistance to a build-up of organic acids and soluble COD behavior was mainly due to the maintenance of the methane bacteria in the fixed-film system which prevents washout as the organic loading increased. The anaerobic fluidized bed reactor was therefore effective for the digestion of waste activated sludge at short HRT.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.961-965
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• 2007

In this study, degradation of carbohydrates and composition of fermentative products were investigated in semi-continuous acid fermenter varying hydraulic retention time (HRT). Rice soup was used as a sole substrate for the acid fermentation. Solubilization efficiency of the substrate was higher than 70% for all HRT, however the gas conversion was ignorable implying that most of organic contents in the influent remained in the form of volatile fatty acids (VFAs) and ethanol after acid fermentation. The VFAs were the predominant product and the VFAs conversion increased as the HRT decreased. The VFAs conversion reached the maximum value at 12 hr HRT accounting for 70% of the influent COD. Similar to VFAs, ethanol conversion was increased with the decrease of HRT and the maximum ethanol conversion efficiency was 8% at the HRT of 12 hr. Composition of VFAs was markedly dependent on HRT. As HRT increased, the composition of acetic acid was increased as a product of acetogenesis from butyrate, valerate and ethanol. This study demonstrated that HRT affected acid fermentation of a carbohydrate containing organic wastes producing VFAs and ethanol which could be effectively used to compensate the lack of carbon in wastewater for biological nutrient removal.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1040-1044
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• 1998

Tetrasodium pyrophosphate peroxidate can be crystallized as a hydrogen-peroxide-bound salt from the solution of tetrasodium pyrophosphate and hydrogen peroxide. The antimicrobial activity and stability of the compound were tested for the use as a food preservative. It showed antimicrobial activities against several food spoilage microorganisms at the concentration of 0.1% (w/v), and was stable for 80 days in room temperature as a form of 70% hydrogen-peroxide-bound tetrasodium pyrophosphate peroxidate. It was also stable at the boiling temperature but decomposed significantly in the presence of metal ions. The compound can be an effective food preservative at the 0.2% (w/v) concentration, which contains 0.03% (v/v) hydrogen peroxide. The compound could be commercialized if the application area and usage direction as well as the removal method of hydrogen peroxide were developed.

• Membrane Journal
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• v.18 no.3
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• pp.250-255
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• 2008

Zeolite A have been known to be chemically, mechanically and thermally quite stable. The ion-exchanged membranes were tested for the removal of water from ethanol/water mixtures by pervaporation. Since it is quite difficult to prepare the potassium form of zeolite A by a direct synthesis, it was obtained by the ion-exchange method from NaA zeolite. The effects of concentration of ethanol at the feed side and the temperature were studied on the permeation flux and the separation factor of water. After $Na^+$ ion was exchanged to $K^+$ ion, it was found that the total flux decreased and the separation factor increased.

• Archives of Plastic Surgery
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• v.35 no.4
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• pp.407-412
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• 2008

Purpose: Hydrofluoric acid(HF) is one of the most dangerous mineral acids with the dissociated fluoride ions. The initial corrosive burn is caused by free hydrogen ion, and the second and more severe burn is caused by penetration of fluoride ions into subcutaneous tissues. Silver is a cation producing dressing, an effective antimicrobial agent, but older silver-containing formulations are rapidly inactivated by wound environment, requiring frequent replenishment. But, $Acticoat^{(R)}$ is a relatively new form of silver dressing which helps avoid the problems of earlier agents. The aim of this study is to evaluate effects of $Acticoat^{(R)}$, silver-containing dressing on the treatment for HF injury wound. Methods: From september 2006 to september 2007, the study was carried out with 10 patients who had HF partial thickness burns. $Acticoat^{(R)}$ dressing and 10% calcium gluconate wet gauze dressings in 10 cases. As a principle, in the emergency treatment, partial or complete removal of the nail and early bullectomy along with copious washing with normal saline was done, depending on the degree of HF invasion of the wound. Wound was dressed with $Acticoat^{(R)}$ and 10% calcium gluconate solution. The effect of dressing was investgated by serial bacterial culture and wound exudates assessment. Results: We therefore reviewed 10 cases of HF-induced chemical burns and treatment principle. The 10 cases who came to the hospital nearly immediately after the injury healed completely without sequelae. Conclusion: As the industrial sector develops, the use of HF is increasing more and more, leading to increased incidences of HF-induced chemical burns. The education of patients regarding this subject should be empathized accordingly. In conclusion, $Acticoat^{(R)}$ dressing is a better choice for HF partial thickness burn injuries because of shorter healing time, less pain and more comfortable dressing.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.34 no.3
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• pp.1-8
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• 2002

The object of this study was to determine the surface energy of hydrophobically modified micro-crystalline cellulose (MCC) with AKD and evaluate the effect of surface energy of the solid particles dispersed in aqueous medium on flotation efficiency. Especially to eliminate the complication derives from the diverse parameters of solid particles including particle size, type, etc. MCC's modified with AKD have been used. The surface energy Parameters were calculated from advancing contact angles of apolar and polar liquids on MCC pellets using the Lifshitz-van der Waals acid-base (LW:AB) approach. Total surface energy of hydrophobic MCC ranged from 46.19 mN/m to 48.60 mN/m. The contribution of the acid-base components to the total surface energy ranged form 13% to 17% for hydrophobic MCC's. The effect of surface characteristics on the flotation efficiency was evaluated. It was shown that there exist critical values of surface energies to increase flotation efficiency. Total surface energy and polar component of solid particles should be lower than 47 mN/m and 7 mN/m, respectively, for effective removal in the flotation process.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.11b
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• pp.159-163
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• 1999

Model experiments were conducted to investigate the effect of different fillers on the removal of toner ink. Combinations of different papers (commercial photocopy paper and filler-free paper), fillers (calcium carbonate, kaolin clay, and talc), and chemicals(1-octadecanol, stearic acid, oleic acid, and TOFA) and stearic acid were found to be effective in detachment and agglomeration of toner ink. Furthermore, pH had little effect on toner detachment and agglomeration, indicating both protonated fatty acids and their anions are equally effective. In the presence of either kaolin clay or talc, all these agglomerating agents are equally effective, although a slightly higher dosage(1% for clay and 2% for talc as compared with control) is required, presumably due to the adsorption of chemical by the filler. Calcium carbonate filler, on the other hand, has a significant and adverse effect on the fatty acids used but has little effect on 1-octadecanol with the exception of possible adsorption. While stearic acid is not effective, a much higher level of oleic acid or TOFA is needed when calcium carbonate fillers are present as compared to the filler-free case. Fatty acids react with calcium carbonate to form calcium salts. The availability of fatty acid anion for toner detachment and agglomeration is determined by the solubility of calcium salt of a given fatty acid. Calcium oleate is 10 times more soluble in water than calcium stearate.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.48-48
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• 2011

We have developed a chemically-driven top-down approach using vapor phase HCl to form various GaN nanostructures and successfully demonstrated dislocation-free and strain-relaxed GaN nanostructures without etching damage formed by a selective dissociation method. Our approach overcomes many limitations encountered in previous approaches. There is no need to make a pattern, complicated process, and expensive equipment, but it produces a high-quality nanostructure over a large area at low cost. As far as we know, this is the first time that various types of high-quality GaN nanostructures, such as dot, cone, and rod, could be formed by a chemical method without the use of a mask or pattern, especially on the Ga-polar GaN. It is well known that the Ga-polar GaN is difficult to etch by the common chemical wet etching method because of the chemical stability of GaN. Our chemically driven GaN nanostructures show excellent structure and optical properties. The formed nanostructure had various facets depending on the etching conditions and showed a high crystal quality due to the removal of defects, such as dislocations. These structure properties derived excellent optical performance of the GaN nanostructure. The GaN nanostructure had increased internal and external quantum efficiency due to increased light extraction, reduced strain, and improved crystal quality. The chemically driven GaN nanostructure shows promise in applications such as efficient light-emitting diodes, field emitters, and sensors.

• Journal of Conservation Science
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• v.26 no.2
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• pp.203-211
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• 2010

Analytic research on the surface pollutant of the three storied-pagoda at the west of Gameunsaji site as well as studies of previous wet cleaning cases was undertaken in order to decide cleaning method for removing inorganic pollutants. The status of pollutant was examined by naked eye observation, SEM-EDS, XRD. Then it was compared and categorized through qualitive and quantitative analysis. The result showed that the surface pollutants consisted of iron compounds or sulfur compounds and it was crystallized in the form of circle, oval, needle, etc. Result, Low-pressure rotating vortex process cleaning, with which particular matters are sprayed in swirl, is considered to be the best method to remove the pollutants.

• Korean Journal of Environmental Agriculture
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• v.25 no.2
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• pp.124-128
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• 2006

To reducing offensive odor form compost UIW-6 mutant obtained by UV treatment from sulfur-oxidizing bacteria, Thiobacillus sp. IW. The UIW-6 mutant was found 1.6 times faster in growth than the parent strain on thiosulfate medium (TM) at 36 h after incubation. Initial pH, temperature and agitation for the optimum growth of UIW-6 were 6.5, $35^{\circ}C$ and 200 rpm, respectively. The UIW-6 mutant growth was two times higher than parent strain at 6 h culture in TM liquid medium containing 50 mM sodium thiosulfate. The UIW-6 mutant used fructose and sucrose as carbon sources and yeast extract> tryptone> peptone as nitrogen ones. It was found that the growth of UIW-6 was increased in addition of 0.2% yeast extract.