• Journal of Korea Soil Environment Society
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• v.5 no.2
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• pp.87-97
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• 2000

The effects of environmental conditions, initial dissolved oxygen concentrations, pH, and the presence of electron carrier vitamin $B_{12}$, on the reduction rate of Tn by $Fe^0$ was quantitatively analyzed using a batch reactor In all experiments, TNT reduction was best described with a first order reaction and the reduction rate decreased with the increase in the initial DO concentration. However, the specific reaction rate did not decrease linearly with the increase in the initial DO concentration. In the presence of HEPES buffer 0.2 and 2.0 mM(pH 5.7$\pm$0.2), the specific reaction rate increased more than 5.8 times, which showed reduction rate is rather significantly influenced by the pH of the solution. To test the possibility of reaction rate enhancement, well-known electron carrier(or mediator) , vitamin $B_{12}$, has augmented besides $Fe^0$. In the presence of 8.0 $mu\textrm{g}$/L of vitamin $B_{12}$, the specific reaction rate increased as much as 14.6 times. The results indicate that the addition of trace amount of vitamin $B_{12}$ can be a promising rate controlling option for the removal of organics using a $Fe^0$ filled permeable reactive barrier.

• KSBB Journal
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• v.14 no.1
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• pp.114-118
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• 1999

In order to use a polysaccharide, curdlan, as a concrete admixture, we first developed a pilot-scale fermentation process for the mass production of curdlan. We also examined the rheological properties of curdlan, and tested how well the curdlan obtained in this work increased the segregational resistance of the cement slurry. Fermentation was performed in a 300-liter fermenter equipped with 3 disk-turbine impellers. Since curdlan production is stimulated under nitrogen-limiting conditions, the culture pH was shifted from the optimal pH for cell growth (pH 7.0) to the optimal pH for curdlan production (pH 5.5) at the onset of ammonium exhaustion. We obtained a curdlan production of 65 g/L in 120 hr batch cultivation of Agrobacterium species. The insoluble curdlan at the final stage of fermentation was readily harvested by centrifugation together with the cells. The freeze-dried sample contained 78% (w/w) of curdlan. The solubility and viscosity of the curdlan increased with the increase of the solution pH, which enhances the viscosity of concrete since the pH of concrete is extremely high (pH 13.0). Test results of the curdlan as a concrete admixture with cement slurry demonstrated that it prohibits the leakage of water. In conclusion, this work certifies and enlarges curdlan's industrial potential as a concrete admixture.

• KSBB Journal
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• v.22 no.1
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• pp.16-21
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• 2007

Although Energy demands of modern society increase rapidly, current energy would be exhausted shortly. Therefore development of bio-ethanol production process from cellulose containing materials was extremly demanded. Therefore development of highly functional cellulase is requisite for this purpose. In this study cellobio-hydrolase (CBH1) gene from Trichorderma reesei was used to increase cellulase activity by directed evolution and highly functional cellobio-hydrolase was obtained and characterized.

• Korean Journal of Microbiology
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• v.46 no.1
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• pp.27-32
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• 2010

We used phototrophic bacteria to remove low concentrated organic materials (CODCr), nitrogen and phosphorus. We applied $COD_{Cr}$ 37.3 mg/L, $NH_3-N$ 4.0 mg/L, and $PO_4^{3-}-P$ 1.0 mg/L (C:N:P=100:10:1) in the batch test, and the removal efficiencies were shown as follow: $COD_{Cr}$ 87.4%, $NH_3-N$ 46.3%, $PO_4^{3-}-P$ 79.7%. The aerobic process with mixed phototrophic bacteria, ceramic media, and media KSP01 showed the removal efficiencies of $COD_{Cr}$, $NH_3-N$, and $PO_4^{3-}-P$, each as 72.7% and 79.2%, respectively in the lab-scale reactor. The maximum $PO_4^{3-}-P$ removal efficiency reached 92.6% by adjusting pH. There were three conditions used to remove $NH_3-N$. The highest removal efficiency was 98.5% with 10.2 L/min of aeration in 1-2 reactors, and the result of applying river-water showed the high removal efficiency of $NH_3-N$ (82.8%). Therefore, this purification system may be useful to control nitrogen and phosphorus at low concentration in field.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.231-239
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• 2005

This study was performed to investigate adsorption characteristics of MTBE and Cd depending upon types of clay minerals md their physicochemical properties. The adsorption characteristics were examined by batch adsorption test on various experimental parameters such as adsorption time, ratio of solution to soil, concentration of contaminants, content of organic matter, pH, and zeta potential. The adsorption efficiency of MTBE or Cd for three types of clays decreased in response to the increase of the ratio of solution to soil whereas their adsorbed amounts increased. MTBE was greatly adsorbed in the decreasing order of vermiculite, bentonite, and CTAB-bentonite while Cd was adsorbed in the decreasing order of bentonite, vermiculite, and CTA-bentonite. An equilibrium isotherm for MTBE was well fitted to Freundlich plotting whereas that for Cd was closely corresponded to Langmuir isotherm. The adsorbed amount of MTBE on bentonite and vermiculite showed the maximum at 1% and 5% of humic acid, thereafter diminished while the adsorbed amount of MTBE on CTAB-bentonite increased in proportion to humic acid. Conversely, the adsorbed amount of Cd on the addition of humic acid continued to increase regardless of types of adsorbents. For all types of adsorbents, adsorbed quantity and adsorption efficiency of Cd have been coincidently increased at pH 8 and they were further enhanced at pH 10 showing 90% adsorption efficiency. Upon pH rose, the zeta potential on each adsorbent began to decrease, while increasing Cd concentration led to decline of zeta potential, which in turn ascribed to lowering dispersion stability that could consequently enhance adsorption capability.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.2
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• pp.73-80
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• 2015

An investigation on the removals of tetracycline (TTC), which is a family of antibiotics widely founded in the environment, from the aqueous solution by birnessite(${\delta}-MnO_2$)-mediated oxidative transformation was described. This study also examined the potential effect of the naturally occurring substances, humic acid (HA) on the oxidative transformation. The experiment was carried out in various conditions (reaction time, Mn oxide loadings, pH) and in the presence of HA as a batch test. The removals of TTC followed pseudo-first order reactions, and rate constants (k, $hr^{-1}$) for the removals of TTC were constantly increased with decreasing pH from 0.98 (pH 9) to 2.97 (pH 3). The rate constants also increased about 1.3 times when the birnessite loading increased from 1 to 2 g/L. Presence of HA (5 mg-C/L, at $pH{\geq}6$) caused some enhancement in the removals of TTC as compared to the control, and also showed the removal efficiencies of TTC in the birnessite mediated systems (TTC=0.25 mM, ${\delta}-MnO_2=2.0g/L$, pH 6) increased with increasing HA concentrations (1~10 mg-C/L). The results obtained from the oxidative transformation of TTC and the effect of HA were discussed in terms of reaction characteristics and mechanism.

• Resources Recycling
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• v.27 no.5
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• pp.69-76
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• 2018

For the purpose of optimizing the counter current extraction process for separation of [Sm] and [Pr, Nd] group in hydrochloric acid solution using Cyanex 572 as an extractant, the theory of Xu Guangxian was derived for calculating the optimized extraction factors. From the basic batch test result, the separation factor of [Sm]/[Pr, Nd] was 14.59 at pH 1.75 in extraction process and 14.61 at 0.01 M HCl in scrubbing process. The process parameters can be calculated using a theory of optimum extraction ratio. From the result of calculation, the total extraction and scrubbing stage numbers at counter current process were 11 and for maintain extraction ratio the flow rate ratio of feed solution, solvent solution, scrubbing solution was 6.25 : 1.74 : 5.80 using 0.1 M HCl.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.3
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• pp.116-126
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• 1995

The purpose of this study was to investigate the removal of ammonium nitrogen by biological nitrification in raw water containing LAS using BAC. At batch teats, LAS removal by ozone followed the first order reaction, and the rate constants(k) by ozone dose 1, 3mg/min.L were $0.040min^{-1}$, $0.062min^{-1}$ respectively. Therefore, the more ozone was dosed, the higher LAS was removed The reaction between ozone and ammonium nitrogen also followed the first order, and rate constants(k) at pH7,8 and 9 were $8.9{\times}10^{-4}min-1$, $3.8{\times}10^{-3}min^{-1}$, and $2.9{\times}10^{-2}min^{-1}$ respectively at ozone dose of 3mg/min.L . Therefore, ammonium nitrogen was little removed by ozone under neutral pH of 7. The continuous flow apparatus had four sets composed of a ozone contacter and a GAC column. Through continuous filtration test for 50days, the following conclusions were derived; (1) LAS was removed 23%, 30% respectively by ozone dose 1, 3mg/L, and was not detected in all column effluents during the period of experiment. Therefore, it appeared that adsorption capacities of each column still remained. (2) Ammonium nitrogen concentration after ozone contact varied little in raw Water because pH of raw water was from 6 to 7, and was transfered to nitrite and nitrate within GAC columns as the result of staged nitrification. After 30days, nitrite was not detected in all column effluents due to biological equilbrium between nitro semonas and nitrobacter Average removals of ammonium nitrogen in each column after the lapse of 30days were the following; ${\cdot}$ column A (ozone dose 3mg/L, EBCT 9.5min): about 100% ${\cdot}$ column B (ozone dose 1mg/L, EBCT 9.5min): 91% ${\cdot}$ column C (ozone dose 3mg/L, EBCT 14.2min): about 100% ${\cdot}$ column D (ozone dose 0mg/L, EBCT 9.5min): 53% Though column A and C reached nitrification of about 100%, column C (longer EBCT than column A) was more stable than column A. (3) After backwash, nitrification reached steady state within 5 to 8 hours. Therefore, nitrification was not greatly affected by backwash. (4) According to the nitrification capacity in depth of column A, C, where 100% nitrification occured. LAS was removed within 20cm, while ammonium nitrogen required more depth to be removed by nitrification.

• Journal of the Korea Organic Resources Recycling Association
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• v.12 no.4
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• pp.121-129
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• 2004

Anaerobic digestion is the most common process for sewage sludge stabilization and has benefits of VS reduction and biogas production. Many pretreatment methods have been studied to improve hydrolysis rate because the rate of sewage sludge degradation is slow in anaerobic digestion. This study mainly focused upon the effects on disintegration of sewage sludge by ultrasonic pretreatment according to the variation of acoustic density and duration of sonication time. In this study, acoustic density has been changed as follows : 33W/L, 70W/L, 88W/L, 139W/L in case of 40 kHz with the test time changes of 10min, 20min, 25min, 30min and 40min. In the comparison of $SCOD_{Cr}/TCOD_{Cr}$ variation for excess sludge and mixed sludge disintegration, the rates of $SCOD_{Cr}/TCOD_{Cr}$ have been increased in the condition of denser acoustic density and longer sonication time with acoustic frequency of 40kHz. The pH of the excess sewage sludge and mixed sewage sludge has been decreased in the condition of denser acoustic density and longer sonication time with acoustic frequency of 40kHz.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.1
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• pp.44-50
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• 2013

E-glass fiber is the most widely used glass fiber for reinforced composite materials of aircrafts, automobiles and leisure equipments. But recently researches are being progressed to reduce boric oxide from 8 % to 0 (zero), as is called 'Boron free E-glass', because of increasing material cost, environmental problem, and improving chemical resistance and mechanical properties of E-glass fiber. In this study, we fabricated the bulk glass and fiber glass of 'Boron free E-glass (BF) compositions', and characterized thermal properties and optical properties. 'Boron free E-glass (BF)' was obtained by the melting of mixed batch materials at $1550^{\circ}C$ for 2 hrs with different $Al_2O_3$ compositions 5~10 %. We obtained transparent clear glass with high visible light transmittance value of 81~86 %, and low thermal expansion coefficient of $4.2{\sim}4.9{\times}10^{-6}/^{\circ}C$ and softening point of $907{\sim}928^{\circ}C$. For the chemical resistance test of 'BF' fiber samples, we identified that the higher alumina contents gives the better corrosion resistance of glass fiber.